# Rocks/Glaciers/Astroglaciology

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Vatnajökull, Iceland has an ice cap. Credit: NASA.

The discoveries of water ice on the Moon, Mars and Europa add an extraterrestrial component to the field, as in "astroglaciology".[1]

## Astronomy

The great Tambora eruption in 1815 and its aftermath "was the world's greatest ash eruption (so far as is definitely known) since the end of the last Ice Age. This synthesis is based on data and methods from the fields of volcanology, oceanography, glaciology, meteorology, climatology, astronomy, and history."[2]

## Glaciology

Taku Glacier winds through the mountains of southeastern Alaska. Credit: U. S. Navy.
The diagram illustrates the interrelationship of glaciology terms. Credit: .

Def. "a mass of ice that originates on land, usually having an area larger than one tenth of a square kilometer"[3] is called a glacier.

"[M]any believe that a glacier must show some type of movement; others believe that a glacier can show evidence of past or present movement."[3]

"Taku Glacier [in the image at the left] winds through the mountains of southeastern Alaska, calving small icebergs into Taku Inlet."[3]

Def. the study of the internal dynamics and effects of glaciers is called glaciology.

"Satellite imagery and data from ground surveys are used to reconstruct the integrated pattern of the principal longitudinal and transverse features produced on a continent-wide scale by the last ice sheets in Europe and North America."[4]

## Planetary sciences

This is an aerial image of the ice cap on Ellesmere Island, Canada. Credit: National Snow and Ice Data Center.
This is an aerial image of the Kalstenius Icefield on Ellesmere Island, Canada. Credit: the Royal Canadian Air Force, archived at the World Data Center for Glaciology, Boulder, CO.

Def. "a dome-shaped mass of glacier ice that spreads out in all directions"[3] is called an ice cap.

An "ice cap is usually larger than an icefield but less than 50,000 square-kilometers (12 million acres)."[3]

Def. "a mass of glacier ice; similar to an ice cap, and usually smaller and lacking a dome-like shape; somewhat controlled by terrain"[3] is called an icefield.

The image at the left of "Kalstenius Icefield, located on Ellesmere Island, Canada, shows vast stretches of ice. The icefield produces multiple outlet glaciers that flow into a larger valley glacier. The glacier in this photograph is three miles wide."[3]

## Color astronomy

"The optical characteristics of sediment suspensions in the glacierfed lake Veitastrondsvatn are examined to explain observed color variations. The color depends on the wavelength where the ratio between the backward scattering coefficient and the absorption coefficient of the suspension has its maximum, and this usually coincides with the wavelength where the absorption has its minimum."[5]

## Minerals

"A mineral is a naturally occurring homogeneous solid, inorganically formed, with a definite chemical composition and an ordered atomic arrangement. Ice is naturally occurring, given a temperature below 0 degrees Celsius (32 degrees Fahrenheit). It is homogenous (of one material), formed inorganically, and has an ordered atomic structure. Ice has a definite chemical composition (H20), with hydrogen and oxygen atoms bonding in a specific manner."[3]

## Theoretical astroglaciology

The diagram is a cross-section of a glacier showing facies at the end of the balance year from glaciological field observations. Credit: Jan-Gunnar Winther.

Def. "a dome-shaped mass of glacier ice that covers surrounding terrain and is greater than 50,000 square kilometers (12 million acres)"[3] is called an ice sheet.

At the center above is an idealized diagram of an alpine or mountain glacier. "Glaciers are composed of an ablation and an accumulation area. Within these two areas several facies might be present [as indicated in the center diagram]. The facies represent distinctive areas with characteristics that reflect the environment under which the snow or ice was formed."[6]

"The accumulation area is typically composed of wet-snow facies, percolation facies and dry-snow facies [...] due to long periods of mild weather which influence the glacier surface at all altitude levels, the accumulation area [may consist] predominantly of wet- snow facies at the end of the ablation period."[6]

"Superimposed ice is formed by (1) the refreezing of meltwater during the autumn and/or during the ablation period and (2) the refreezing of meltwater on the glacier surface below the snow line at the end of the ablation period [...] net loss by melting occurs in the ice facies."[6]

## Entity astronomy

Def. "a current of ice in an ice sheet or ice cap that flows faster than the surrounding ice"[3] is called an ice stream.

## Radiation astronomy sources

Def. "growth of a cloud or precipitation particle by the collision and union of a frozen particle (ice crystal or snowflake) with a super-cooled liquid droplet which freezes on impact"[3] is called accretion.

## Object astronomy

Here is shuga forming on a shoreline. Credit: Antarctic Sea-Ice Processes and Climate program (ASPeCt).

Def. "a body of unfrozen ground, that is perennially cryotic (T < 0 degrees Celsius) and entirely surrounded by perennially frozen ground"[3] is called an isolated cryopeg.

Def. "a form of new ice, composed of spongy, white lumps a few cm across, that tend to form in rough seas; they resemble slushy snow balls"[3] is called shuga.

## Cryospheres

The photo shows ridged sea ice. Credit: Don Perovich, U.S. Army Cold Regions Research and Engineering Laboratory.

The cryosphere is a term which collectively describes the portions of an astronomical object's surface where water is in solid form, including sea ice, lake ice, river ice, snow cover, glaciers, ice caps and ice sheets, and frozen ground (which includes permafrost). Thus there [may be] a wide overlap with [a] hydrosphere. The cryosphere is an integral part of the global climate system with important linkages and feedbacks generated through its influence on surface energy and moisture fluxes, clouds, precipitation, hydrology, atmospheric and oceanic circulation. Through these feedback processes, the cryosphere plays a significant role in global climate and in any climate model response to global change.

Def. "process that occurs when wind, ocean currents, and other forces push sea ice around into piles that rise and form small mountains above the level sea ice surface; ridges are initially thin and transparent with very sharp edges from blocks of ice piling up"[3] is called ridging.

## Cryopediology

Cryopediology is any study relating to the behavior of frozen snow. The shapes into which frozen snow is blown by the wind (e.g. on the tundra) are said to be 'cryopediological formations'. The ways in which frozen snow behaves due to factors intrinsic to itself and relating to environments are 'cryopediological processes'.

## Strong forces

This is an image of an alpine, or mountain, glacier. Credit: U. S. Navy.

Def. "a glacier that is confined by surrounding mountain terrain; also called a mountain glacier"[3] is called an alpine glacier.

## Electromagnetics

This is a close-up view of frost flowers. Credit: Don Perovich, U.S. Army Cold Regions Research and Engineering Laboratory.

Def. "crystals of ice that form when water vapor becomes a solid (bypassing the liquid phase) and deposits itself on the sea ice surface"[3] are called frost flowers.

"[F]rost flowers [in the image at the right] roughen the surface and dramatically affect its electromagnetic signal."[3]

## Weak forces

This is a close up of chatter marks. Credit: Tom Lowell, University of Cincinnati.

Def. "striations or marks left on the surface of exposed bedrock caused by the advance and retreat of glacier ice"[3] are called chattermarks.

In the image at the right is a close "up of chatter marks, Mt. Sirius, Antarctica. Lens cap in the photo is five centimeters across."[3]

## Continua

This chaotic terrain on Europa has areas consisting of densely packed blocks with fractures and narrow lanes of matrix between them. Credit: G. C. Collins, J. W. Head III, R. T. Pappalardo, and N. A. Spaun.{{fairuse}}
The image shows areas on Europa consisting of almost all matrix and no blocks. Credit: G. C. Collins, J. W. Head III, R. T. Pappalardo, and N. A. Spaun.{{fairuse}}
Conamara Chaos, the most intensely studied chaos area, lies near the middle of this continuum. Credit: G. C. Collins, J. W. Head III, R. T. Pappalardo, and N. A. Spaun.{{fairuse}}
High-resolution (10 m/pixel) image shows a plate surrounded by matrix material within Conamara Chaos. Credit: G. C. Collins, J. W. Head III, R. T. Pappalardo, and N. A. Spaun.{{fairuse}}
Image of Europa's Conamara Chaos taken by the Galileo spacecraft. This view is approximately 35 kilometers across. Credit: NASA.{{free media}}

"The morphology of chaotic terrain forms a continuum from areas consisting of densely packed blocks with fractures and narrow lanes of matrix between them ([first image at the right]), to areas consisting of almost all matrix and no blocks ([first image at the left]). Conamara Chaos, the most intensely studied chaos area ([second image at the right]), lies near the middle of this continuum, with -60% of its area consisting of matrix and the remainder consisting of blocks [Spaunet al., 1998]. In addition to these large chaos areas, chaotic terrain also occurs in the interiors of some small (-10 km diameter) features [Spaun et al., 1999] known as "lenticulae.""[7]

"In Conamara Chaos, where data with spatial resolution of up to ten meters per pixel were obtained, the hummocky matrix appears to be a jumbled collection of ice chunks of all sizes, from a kilometer to tens of meters across ([second image on the left])."[7]

## Emissions

An ice pinnacle separates from Perito Moreno Glacier. Credit: Martyn Clark.

Def. a "process by which ice breaks off a glacier's terminus"[3] is called calving.

## Absorptions

This shows a cirque on Cirque Mountain in the Torngat Mountains, Newfoundland, Canada. Credit: Hazen Russel, Natural Resources Canada, Terrain Sciences Division, Geological Survey of Canada.

Def. a "bowl shape or amphitheater usually sculpted out of the mountain terrain by a ... glacier"[3] is called a cirque.

The image at the right shows an archetype cirque "on Cirque Mountain in the Torngat Mountains, Newfoundland, Canada."[3]

## Bands

Ogives are imaged on the Juno Icefield. Credit: Janet Beitler.

Def. "a distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form subhorizontal layers"[3] is called a banded cryogenic fabric.

Def. "a distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form subhorizontal layers of similar thickness"[3] is called an isoband cryogenic fabric.

Def. "alternate bands of light and dark ice seen on a glacier surface"[3] are called ogives.

Def. "alternate bands of light and dark on a glacier; usually found below steep narrow icefalls and thought to be the result of different flow and ablation rates between summer and winter"[3] is called banded ogives.

Def. "ogives that show some vertical relief on a glacier; usually the dark bands are in the hollows and the light bands are in the ridges; form at the base of steep, narrow ice falls"[3] are called wave ogives.

## Backgrounds

The striated graywackie, Yale Glacier, Alaska, has glacial grooves [glacial striations] running horizontally across. Credit: Tom Lowell, University of Cincinnati.

Def. "grooves or gouges [striations] cut into the bedrock by gravel and rocks carried by glacial ice and meltwater"[3] are called glacial grooves, or glacial striations.

"Parallel striations and bedrock fracture trends (across the left side of the image) are clearly visible in this photo [at the right]."[3]

## Meteors

This shows an avalanche in motion. Credit: Richard Armstrong, National Snow and Ice Data Center.
Avalanche is occurring in a USA national park. Credit: National Park Service.{{free media}}
An avalanche is coming down the face of Mount Index, WA. Credit: Josh Lewis.
An avalanche is occurring in May 2006 on Mount Everest. Credit: Chagai.{{free media}}
This is the start of a powder snow avalanche. Credit: Scientif38.{{free media}}
This is the small powder snow avalanche after the start of a powder snow avalanche. Credit: Scientif38.{{free media}}

Def. a "mass of snow which becomes detached and slides down a slope, often acquiring great bulk by fresh addition as it descends"[3] is called an avalanche.

Both avalanches, left and right, top are avalanches in motion in the USA, the one on the left is in Washington. The one on the right was photographed by Richard Armstrong for the National Snow and Ice Data Center, probably in Colorado.

## Glaciers

The massive lobe of Malaspina Glacier in Alaska is clearly visible in this photograph taken from a Space Shuttle flight. Credit: NASA.
This is an image of icefalls on three parallel glaciers. Credit: Tom Lowell, University of Cincinnati.

Def. a "large ice lobe spread out over surrounding terrain, associated with the terminus of a large mountain valley glacier"[3] is called a piedmont glacier.

"The massive lobe of Malaspina Glacier in Alaska is clearly visible in this photograph taken from a Space Shuttle flight in 1989. Agassiz Glacier is the smaller glacier to the left. The Malaspina Glacier is one of the most famous examples of this type of glacier, and is the largest piedmont glacier in the world. Spilling out of the Seward Ice Field (visible near the top of the photograph), it covers over 5,000 square kilometers as it spreads across the coastal plain."[3]

Def. a "part of a glacier with rapid flow and a chaotic crevassed surface; occurs where the glacier bed steepens or narrows"[3] is called an icefall.

## Cosmic rays

"Evidence for millennial-scale climate variability during the Holocene has been found in the sediments of ice-rafted debris in the North Atlantic [59, 60]. Deep sea cores reveal layers of foraminifera shells mixed with tiny stones that were frozen into the bases of advancing glaciers and then rafted out to sea by glaciers. These reveal abrupt episodes when cool, ice-bearing waters from the North Atlantic advanced as far south as the latitude of southern Ireland, coincident with changes in the atmospheric circulation recorded in Greenland. These so-called Bond events (named after their discoverer) have occurred with a varying periodicity of 1470±530 y, during which temperatures dropped and glacial calving increased. The estimated decreases in North Atlantic Ocean surface temperatures are about 2°C, or 20% of the full Holocene-to-glacial temperature difference."[8]

"What could be the trigger for this millennial-scale climate change? Orbital variations of insolation are too slow to cause such rapid changes. Ice sheet oscillations are also unlikely to be the forcing agent, for two main reasons. Firstly, the icebergs were launched simultaneously from more than one glacier. Secondly, the events continued with the same quasi-1500 y periodicity for at least the last 30 ky through the Holocene and into the last glacial maximum (but with a larger amount of ice-rafted material)—even though the ice sheet conditions changed dramatically over this interval. Solar/GCR [galactic cosmic rays (GCR)] variability appears to be a promising candidate for the forcing agent during the Holocene phase since it is found to be highly correlated with the Bond events (Fig. 8) [61]."[8]

## Neutrals

"The major atmospheric gases on Earth, Venus, and Mars were probably CO2, H2O, and N2. [The ions from the upper parts of an atmosphere] are often suprathermal, and their interactions can produce suprathermal neutral atoms as well [The] ionopause [...] separates the bound ionosphere from an outer region in which the solar wind is diverted and flows around and past the planet. This region still contains some neutral gas, and if such atoms are ionized by solar photons or electron impact, they are swept up in the flow."[9]

"There are strong reasons to believe that Mars once had much more atmospheric CO2 and H2O than it now has ... (Impacts, which may have eroded even larger amounts, operated at an earlier period.) ... The visible polar caps are thought to contain relatively small quantities. [...] More recently it has been proposed (35) that Mars may have had several episodes of high atmospheric pressure, warm conditions, and substantial precipitation of rain and snow, with a north polar ocean and southern glaciers."[9]

## Subatomics

"The geologic spacing of the great ice ages probably reflects the Galactic Cycle."[10]

"The other climate-related radiation is by high-energy subatomic particles which reach the Earth in the "Solar Wind .""[10]

## Neutrons

36Cl "is created by high-energy cosmic-ray neutron reactions on potassium and calcium and low energy neutron reactions on stable chlorine."[11]

## Protons

"Bacterial populations found in subglacial meltwaters and basal ice are comparable to those in the active layer of permafrost and orders of magnitude larger than those found in ice cores from large ice sheets. Populations increase with sediment concentration, and 5%–24% of the bacteria are dividing or have just divided, suggesting that the populations are active. These findings (1) support inferences from recent studies of basal ice and meltwater chemistry that microbially mediated redox reactions may be important at glacier beds, (2) challenge the view that chemical weathering in glacial environments arises from purely inorganic reactions, and (3) raise the possibilities that redox reactions are a major source of protons consumed in subglacial weathering and that these reactions may be the dominant proton source beneath ice sheets where meltwaters are isolated from an atmospheric source of CO2."[12]

## Beta particles

"[L]uminescence dating techniques [may] provide absolute age determinations of eolian sediments on the surface of Mars, including those incorporated in the martian polar ice caps. Fundamental thermally and optically stimulated luminescence properties of bulk samples of JSC Mars-1 soil simulant [have been studied]. The radiation-induced luminescence signals (both thermoluminescence, TL, and optically stimulated luminescence, OSL) from JSC Mars-1 are found to have a wide dynamic dose–response range, with the luminescence increasing linearly to the highest doses used (936 Gy), following irradiation with 90Sr/90Y beta particles."[13]

## Electrons

"The launch of ALOS and the high potential expected for the L-band PALSAR [necessitates investigating] ionospheric electron concentration effects using JERS L-band SAR data acquired at high latitudes."[14]

"Using L-band INSAR and offset tracking for arctic glacier motion monitoring [3], [there is interest] in identifying and, if possible, correcting errors introduced by ionospheric effects."[14]

## Positrons

"The proton-proton chain, or hydrogen burning, is postulated by standard stellar theory as the principal mechanism of energy generation in the sun during the current stage of its evolution. The net result of this chain of nuclear reactions is conversion of four protons into helium-4, and the energy released is carried off by photons, positrons, and neutrinos."[15]

"The nuclear reaction chains postulated by the standard model as the mechanism of solar energy generation [...] include a number of weak interactions (electron captures and beta decays [such as the beta decay of boron-8]) that produce neutrinos."[15]

## Muons

Inheritance "of cosmogenic nuclides from periods of prior exposure occurs in midlatitude terrains affected by continental glaciation and that such inheritance can be significant, especially for hard rocks near former ice margins."[16]

"Although nuclide production by muons is usually a few percent of neutron production at the surface, it extends much deeper (Λ = 1300 g·cm-2) and dominates nuclide production below 2–3 m depth [...] For some nuclides, such as 36Cl produced from Ca, near-surface muon production is very important (>25%) and if disregarded will lead to significant changes in estimates of erosion rate and age (Stone et al., 1998a).[16]

"The quarry samples demonstrate that even deeply shielded rocks contain measurable 10Be and 26Al. The nuclides we detected must have been produced by muons, which penetrate far deeper than neutrons [...]. In order to limit 10Be inheritance to 1000 yr or less, almost 7 m of rock must be removed between periods of surface exposure if the surface is eroding, on average, relatively quickly (50 m/m.y.). For surfaces eroding more slowly (5 m/m.y.), >25 m of rock must be removed for inheritance to be <1000 yr".[16]

"Minimum inheritance in bedrock (and maximum glacial erosion) appears to occur in deep alpine glacial valleys and fjords where ice flowed rapidly and was not frozen to the bed (Davis et al., 1999). [...] outcrops of weaker rocks and outcrops farther from the ice margin (>50 km) in areas of high erosion (dominated by drumlins and stream-lined bedrock knobs) appear to retain fewer nuclides from periods of prior exposure."[16]

## Neutrinos

${\displaystyle \nu +^{97}Mo\rightarrow e^{-}+^{97}Tc,}$ and
${\displaystyle \nu +^{98}Mo\rightarrow e^{-}+^{98}Tc.}$

These "reactions probe precisely the time scale and neutrino-flux component of most interest: the boron-8 neutrino luminosity, which is the most sensitive monitor of variations in the solar core temperature, during and before the Pleistocene epoch. (The half-lives of technetium-97 and -98 are, respectively, 2.6 and 4.2 million years; the reaction on molybdenum-98 is induced only by the high-energy boron-8 neutrinos; and the reaction on molybdenum-97 may sample in addition the flux of beryllium-7 neutrinos, which are second only to boron-8 neutrinos in sensitivity to the core temperature.)"[15]

A "quantitative test can be made of nonstandard solar models that suggest a connection between the solar neutrino puzzle, the proximity of the Pleistocene glacial epoch, and the fundamental thermal and nuclear times of the solar core."[15]

Solar "mixing about four million years ago [may have] initiated the Pleistocene epoch and a persisting depression of the high-energy solar neutrino flux. Clear memory of the steady-state solar phase that preceded mixing should be retained in technetium-98 with its half-life of 4.2 million years. Recovery of this isotope in a quantity lower than that predicted by the standard solar model but significantly higher than that detected by the Davis experiment would support suggestions of solar variability and solar influence on terrestrial climate."[15]

## Gamma rays

"By depositing larger cosmic ray fluence during a much shorter interval, the prompt flux [from a gamma-ray burst, GRB, has] much greater lethality and effect. The occurrence of the sequence of extinction events in the Ordovician due to a long lasting ∼ 1 Myr ice age (Melott et al. 2004) could happen if the prompt blast induced a long term change in the climate, or if the delayed cosmic rays induce a glaciation (Shaviv 2003). On-axis events are considerably more damaging than off-axis events which, though more numerous, release ≲ 1017 eV cosmic rays that slowly diffuse towards Earth over periods of thousands of years and longer."[17]

## X-rays

This shows a photograph and X-radiograph of part of core D4 illustrating fine laminations. Credit: Robert Gilbert, Niels Nielsen, Henrik Möller, Joseph R. Desloges, and Morten Rasch.
Concentration of gravel particles (>2 mm diameter) assessed from X-radiographs (inset shows example from core D20) are inferred to be dominantly ice-rafted. Credit: Robert Gilbert, Niels Nielsen, Henrik Möller, Joseph R. Desloges, and Morten Rasch.

"Beginning in 1995, a large outlet glacier of the Sermersauq Ice Cap on Disko Island [Greenland] surged 10.5 km downvalley to within 10 km of the head of the fjord, Kuannersuit Sulluat, reaching its maximum extent in summer 1999 before beginning to retreat. Sediment discharge to the fjord increased from 13 x 103 t day-1 in 1997 to 38 x 103 t day-1 in 1999. CTD results, sediment traps and cores from the 2000 melt season document the impact of the surge on the glacimarine environment of the fjord."[18]

"Short gravity cores were taken and CTD profiles were recorded at stations throughout Kuannersuit Sulluat [...]. Positions located by GPS are accurate to ±10 m or less. The stream flowing over the sandur to the head of the fjord was gauged and integrated suspended sediment samples were recovered from primary channels."[18]

"The cores were photographed, X-rayed and logged. X-radiographs provided measures of the number and size of gravel particles interpreted as ice-rafted debris (IRD) and the grey-scale (GS) of the scanned images was plotted as a measure of the properties of the sand and silt."[18]

"The twelve layers in core D4 [imaged at the right] suggest a mean period of about 20 days for these events based on the accumulation rates in the traps [...]. In general, these layers have both higher MS and X-radiographs have lighter toned GS, the former related to lower water content and the latter also related to greater absorption of X-rays by the larger rock and mineral fragments."[18]

There "are notable differences in the surge-generated sediments. The proximal sediments [such as in core D4 at the right] are more clearly laminated and layered in visual examination of the cores and as seen in the X-radiographs [compared to distal sediments as imaged on the left for core D20]. These consist both of the subtle differences in the fine-grained sediments on a millimetre scale, and of the sand layers up to 8 cm thick representing more energetic processes (Ó Cofaigh and Dowdeswell, 2001). Both are a response to greater sediment input to the fjord."[18]

## Ultraviolets

Changes occur "in UV attenuation and macrozooplankton community structure in a set of lakes along a deglaciation chronosequence in Glacier Bay Alaska. Terrestrial succession in the watersheds of these lakes results in increasing dissolved organic carbon (DOC) content over time. Due to the primary role of DOC in controlling UV attenuation in lakes, one would suspect a gradient in UV attenuation and potentially zooplankton community structure in lakes of different ages. Field measurements of UV in seven lakes of different ages revealed that UV attenuation depths (1% of surface irradiance at 320 nm) ranged from 0.6 m in the oldest lake in the set (90 yr old), to more than 14 m in the youngest lake (10 yr old)."[19]

## Opticals

Satellite composite image shows the ice sheet of Greenland. Credit: NASA.
The figure contains spectral reflectance curves for snow and ice in different formation stages. Credit: Jan-Gunnar Winther.

At the right is a satellite composite image of the ice sheet over Greenland.

"The visible reflectance declines from 0.95 to 0.60 as the snow cover metamorphoses to glacier ice [as seen in the figure at the left]."[6]

"The Landsat-5 satellite, launched in March 1984, carries a Multispectral Scanner Subsystem (MSS) and a Thematic Mapper (TM) onboard. The TM senses in the following bands:"[6]

1. (TM1) 0.45-0.52 µm blue-cyan-green,
2. (TM2) 0.52-0.60 µm green-yellow-orange,
3. (TM3) 0.63-0.69 µm red,
4. (TM4) 0.76-0.90 µm near-infrared,
5. (TM5) 1.55-1.75 µm near-infrared,
6. (TM6) 10.40-12.50 µm thermal infrared, and
7. (TM7) 2.08-2.35 µm mid-infrared.

All "TM Bands 1-4 can be used to distinguish snow from firn and ice facies."[6]

"The reflectance lies close to 0.6 for glacier ice and at about 0.2 for dirty glacier ice in the visible range, but increases a little in the infra-red due to the presence of moraine (Zeng et al. 1984). Thus, the visible TM Bands are suitable for separating dirty glacier ice from (clean) glacier ice whereas TM Band 4 is unsuited to this purpose. [...] glacier ice has a larger reflectance than refreezing ice in the visible region while the opposite is the case in the infra-red region."[6]

## Visuals

Explorers examine a crevasse on Lyman Glacier in 1916. Credit: United States Forest Service.
A crevasse in Langjökull glacier created by water drilling a hole tens of meters deep into the glacier ice. Credit: Ville Miettinen.

Def. an "open fissure in the glacier surface"[3] is called a crevasse.

The crevasse in the image at the right is in Lyman Glacier in 1916. The one on the left is in Langjökull glacier, Iceland, on 29 July 2006.

## Violets

Western Brook glacial trough, Newfoundland, Canada, is imaged. Credit: Natural Resources Canada, Terrain Sciences Division, Geological Survey of Canada.

Def. "a large u-shaped valley formed from a v-shaped valley by glacial erosion"[3] is called a glacial trough.

"The sheer walls of this glacial trough [Western Brook glacial trough, Newfoundland, Canada, at the right] soar up to 700 m high, and the glacial basin is 500 m deep in places."[3]

## Blues

This is land fast ice. Credit: Michael Van Woert, National Oceanic and Atmospheric Administration/Department of Commerce.

Def. "ice that is anchored to the shore or ocean bottom, typically over shallow ocean shelves at continental margins; fast ice is defined by the fact that it does not move with the winds or currents"[3] is called fast ice.

The image at the right shows land fast ice.

## Cyans

A composite red-cyan anaglyph image displays the rectified Hexagon stereo pair. Credit: Josh Maurer and Summer Rupper.
This stereo disparity map is computed using the semi-global block matching algorithm. Credit: Josh Maurer and Summer Rupper.
This is a Landsat panchromatic image showing the study region in Bhutan/China, with upper left inset showing the Kingdom of Bhutan in red outline. Credit: Josh Maurer and Summer Rupper.

"A digital elevation model (DEM) is a 3D representation of a terrain surface. DEMs are used in countless applications, such as hydrological/mass movement modeling or even 3D visualizations in flight simulators [...] for land-change studies [there] is [...] DEM differencing [...], which compares DEMs over the same region from different time periods [like the 3D image at the right over Bhutan]. This allows quantification of surface elevation changes due to erosion, landslides, earthquakes, melting glaciers, construction of man-made features, and many other factors. It follows that historical DEMs are useful for land-surface change studies."[20]

To "reconstruct a DEM from 1974 imagery over a large glacierized region in the Bhutan Himalayas, [glacier] changes over several decades are visualized using a DEM differencing method."[20]

"An implementation of the semi-global block matching algorithm (Hirschmuller, 2008) is utilized from the open source software package OpenCV to compute the stereo disparity map [imaged at the left]. Subsequently, matched pixels are projected back to their respective pre-rectified image coordinates using the inverse of the homography transformation."[20]

"“Cool” pixels represent smaller disparities (valleys further from camera), while “hot” pixels represent larger disparities (mountains closer to camera)."[20]

The image at the lower right is a Landsat panchromatic image of the study region in Bhutan/China, with an upper left inset of the Kingdom of Bhutan in red outline.[20]

"Temporal changes in area and volume of glaciers and lakes are of interest in this region to better understand the effect of dwindling glacial ice on water resources."[20]

## Greens

These big lumps in the ground are called thufur. Credit: Reinhold Richter.

Def. "perennial hummocks formed in either the active layer in permafrost areas, or in the seasonally frozen ground in non-permafrost areas, during freezing of the ground"[3] is called thufur.

## Yellows

Photo of the glacier basin taken from a glider shows the yellow Sahara-dust layer melting out in the mid-elevation range of the glacier. Credit: Christina Rothenbühler.

In the photograph at the right, Piz Bernina is the highest mountain of the region. Note the yellow Sahara-dust layer melting out in the mid-elevation range of the glacier.[21]

"The Morteratschgletscher is located in the Bernina Alps, in the Swiss province ("Kanton") Graubuenden, close to Sankt Moritz."[21]

## Oranges

Glacial grooves are caused by erosion of limestone bedrock from the Wisconsin glaciation at Kelleys Island. Credit: Rmhermen.
NASA’s Mars Reconnaissance Orbiter has detected thick ice under the red Martian dust here. Credit: ESA/DLR/FU Berlin (G. Neukum).

Although limestone is usually light gray to white depending on impurities, the heavy glacial grooves and the limestone cross section in the image at the right are brown.

"Signs of glacial ice flows [occur] in the 582-mile-wide feature Deuteronilus Mensae [in the image at the left]."[22]

## Reds

A: Back trajectories are reconstructed using the NOAA ARL Website (www.arl.noaa.gov/ready/) and CDC1 meteorological data. B: Backward trajectory is plotted ending at 06:00 UTC, on March 6, 1990. Credit: Francis E. Grousset, Paul Ginoux, Aloys Bory, and Pierre E. Biscaye.

"Dusts originating from the Sahara/Sahel region are frequently spread over the Mediterranean Sea [Moulin et al., 1997], sometimes reaching France and even southern England [Bücher and Dessens, 1992]. These dusts can be easily sampled a few times a year in the French mountains – mostly in the Alps and the Pyrénées–where they suddenly cover snow surfaces with thin, red-to-brown blankets."[23]

"Over the last 20 years, a few tens of red dust events suddenly covered snow surfaces in the Alps and Pyrénées mountains. They have been carefully sampled with plastic spatula and stored in clean bags [Grousset et al., 1994]. For each of those, the Nd isotopic composition of their carbonate-free fraction has been analyzed [Grousset et al., 1998]. The isotopic composition of Nd is usually defined by the 143Nd/144Nd ratio, which, for convenience, is normalized and reported as follows: ENd(o) = ((143Nd/144Nd/0.512636) − 1).104. Precision of the ENd(o) measurements is ≤ ± 0.2. In northern Africa, ENd(o) ranges from radiogenic values (ENd(o) ≈ 0) in young volcanic areas to unradiogenic values (ENd(o) ≈ −20) such as those observed in the Mauritania Archean provinces [Grousset et al., 1998]. When comparing the data obtained on the particles sampled in Alpine and Pyrenean snows, to those of the isotopic composition of the different dust fields of North Africa, it appears that the dusts reveal generally a North African origin."[23]

## Infrareds

This is a Landsat Thematic Mapper TM Bands 2, 4 and 5 composite image recorded on 7 August 1987 of several glaciers. Credit: Jan-Gunnar Winther.

The "Austre Brøggerbreen and Midre Lovénbreen glaciers [are] located 78°50'N, 11°50'E in the Svalbard archipelago. The satellite data are Landsat-5 TM images recorded on 7 August 1987 and 31 August 1988. In situ measurements of shortwave and spectral reflectance of snow, glacier ice and moraine were carried out in August 1991 and in June 1992."[6]

The image at the right is a composite of visible reflectance in the green-yellow-orange (0.52-0.60 µm) and the infrared (0.76-0.90 µm and 1.55-1.75 µm).

"Austre Brøggerbreen (left arrow) and Midre Lovénbreen (right arrow) lie on the Brøggerhalvøya peninsula due south of the Kongsfjorden inlet. Austre Brøggerbreen terminates on land at about 75 [meters above sea level] m.a.s.l. The upper part of the glacier stretches up to 575 m.a.s.l. and the main flow direction is towards north i.e., towards the upper left corner of the image. The lower part of the glacier has low reflectance due to morainal deposits and exposed blue ice. A transition zone of superimposed ice is seen close to the arrow while the upper part is covered by snow."[6]

"The near-infra-red snow albedo is sensitive to changes in characteristic snow grain size. Spectral measurements show a distinct drop in the near-infra-red albedo as the snow metamorphoses, i.e. the grain size increases. The visible albedo is little affected by the variation of grain size. Clouds affect the snow albedo by introducing a spectral shift to the incoming radiation. It is shown that the integrated snow albedo (370-900 nm) increases by 7% due to the change from clear sky to overcast weather."[6]

## Submillimeters

"Penetration through H2O ice is limited by multiple scattering and by the long-wavelength wing of the submillimeter band. Deep penetration is possible at long wavelengths, and strong reflections could result from pockets or layers of subsurface H2O:NH3 solution."[24]

## Microwaves

(a) The probability is for of a pixel melting at least as many times as observed during the 1995, 1998 and 2002 melt seasons given the last 25 years of melt observations. (b) Melt extent is for 2002: Pixels are color coded for number of melt days during the season. (c) Slopes of the trend lines are fit to the areas observed to melt between April and November from 1979 to 2003. Credit: K. Steffen, S. V. Nghiem, R. Huff, and G. Neumann.
Half-decade records for ETH/CU Camp station: (a) Top panel is for QSCAT backscatter, (b) middle panel for QSCAT diurnal signature, and (c) bottom panel for air temperature measured at the AWS site. Credit: K. Steffen, S. V. Nghiem, R. Huff, and G. Neumann.
QSCAT melt maps are shown on the climatological peak-melt day (1 August). Red color represents current active melt areas, light blue is for areas that have melted but currently refreeze, white is for areas that will melt later, and magenta is for areas that do not experience any melt throughout the melt season. The dark blue color surrounding Greenland is the ocean mask. Credit: K. Steffen, S. V. Nghiem, R. Huff, and G. Neumann.
QSCAT maps of number of melt days (violet to red for 1 to 31 days) in 2000–2003 with the overlaid black contours representing melt extent derived from PM data are shown. Credit: K. Steffen, S. V. Nghiem, R. Huff, and G. Neumann.

"Active and passive microwave satellite data are used to map snowmelt extent and duration on the Greenland ice sheet. The passive microwave (PM) data reveal the extreme melt extent of 690,000 km2 in 2002 as compared with an average extent of 455,000 km2 from 1979–2003."[25]

"Several PM-based melt assessment algorithms [Mote and Anderson, 1995; Abdalati and Steffen, 1995] are applicable to Scanning Multi-channel, Microwave Radiometer (SMMR) and Special Sensor Microwave/Imager (SSM/I) instruments providing near-continuous coverage since 1979. The PM data as gridded brightness temperatures on polar stereographic grids (25 km resolution) [used] are from the National Snow and Ice Data Center [Maslanik and Stroeve, 2003], containing daily data spanning 25 melt seasons from 1979 to 2003."[25]

In the image at the right, (a) "shows the probabilities of the observed melt behavior on the Greenland ice sheet for several large melt years and indicates the extreme melt anomaly observed in northeastern Greenland in 2002."[25]

"Prior to 2002, both 1995 and 1998 were extreme melt years in terms of maximum areal extent and total melt. During 1995 melt was dominated by a high frequency of melt along the western margin of the ice sheet. During 1998 melt was spatially diverse with slightly more melt than usual in the northeast and southwest. However, the high frequency melt in 2002 in the northeast and along the western margin is unprecedented in the PM record with a log likelihood of occurrence that is 35% lower than the previous record melt anomaly in 1991."[25]

(c) "depicts the magnitude of the increasing trends in melt extent on a daily basis over the last 25 years. Although there is a large amount of inter-annual variability in melt extent on a given day, 56 days show statistically significant (alpha = 0.1) increasing trends in melt area."[25]

"Melt along the west coast was extensive during 2002 but not atypical for large melt years. However melt in the north and northeast was highly irregular both in terms of extent and frequency. Nearly 3,000 km2[(b)] were classified as melting during 2002 that had not previously melted during any other year between 1979 and 2003."[25]

The figure at the left "presents QSCAT backscatter and diurnal signatures, and ETH/CU AWS air temperature."[25] Half-decade records for ETH/CU Camp station: (a) Top panel is for QSCAT backscatter, (b) middle panel for QSCAT diurnal signature, and (c) bottom panel for air temperature measured at the AWS site.[25]

At the lower right QSCAT melt maps are shown on the climatological peak-melt day (1 August). Red color represents current active melt areas, light blue is for areas that have melted but currently refreeze, white is for areas that will melt later, and magenta is for areas that do not experience any melt throughout the melt season. The dark blue color surrounding Greenland is the ocean mask.

"QSCAT mapping can reveal details of the spatial pattern of surface melt evolution in time. There are large variabilities in melt extent and melt timing over different regions. [The figure at tje lower right] confirms that 2002 has the most extensive areal melt. In 2002, the northeast quadrant of the Greenland ice sheet, extending well into the dry snow zone, experienced at least some melt where melt never happened before (from satellite data records to date). Since the beginning of the QSCAT data record (July 1999), the smallest spatial extent of melt occurred in 2001, and melt extent was similar for years 2000 and 2003."[25]

"To provide a direct comparison of PM and QSCAT results, we overlay results for PM melt extent and QSCAT number of melt days in [the figure at the lower left] for years 2000–2003. PM XPGR melt extent is approximately confined to QSCAT melt areas experiencing 2 weeks or more of melting time [the figure at the lower left]. QSCAT melt areas outside of the PM melt extent represent the surface that has less melt corresponding to about 15 melt days or less. This is consistent with the relationship of relative melt strength measured by active and passive data as discussed above. Note that such areas can total up to a large region in year 2002. Surface albedo can reduce considerably once the snow melts for a period of 2 weeks. The albedo reduction may significantly impact the surface heat balance and thus change the mass balance. The large number of melt days around the northern perimeter of the ice sheet, which is shown as the narrow dark-red band in north Greenland in the 2003 map was an anomalous feature [the figure at the lower left]. This band was wider as defined by the PM melt extent in 2002 than in 2003. However, there were more QSCAT melt days in the 2003 northern melt band."[25]

"The comparison reveals that the PM cross-polarized gradient algorithm classifies melt more conservatively than the scatterometer algorithm. The active microwave identifies melt approximately up to two weeks more than the PM at higher elevation in the percolation zone toward the dry snow zone [the figure at the lower left]. Both methods (active and passive microwave) consistently identify melt areas that have a melt duration of at least 10–14 days. The longer snowmelt duration can be sufficient to decrease surface albedo and affect surface heat and mass balance."[25]

## Radars

A: Topography of Mars has major features identified. B: Topography shows the MRO/SHARAD ground tracks for orbits 6830 (a-a′), 7219 (b-b′), and 3672 (c-c′). LDAs crossed by these tracks are labeled. Credit: John W. Holt, Ali Safaeinili, Jeffrey J. Plaut, James W. Head, Roger J. Phillips, Roberto Seu, Scott D. Kempf, Prateek Choudhary, Duncan A. Young, Nathaniel E. Putzig, Daniela Biccari, Yonggyu Gim.
Results are for SHARAD orbit 6830 (line a-a′). A: Simulated surface echoes (clutter) are in one-way travel time. B: SHARAD data is in one-way travel time. Vertical arrows identify echoes not consistent with surface clutter simulation and also confirmed in adjacent tracks. C: Radar data is converted to depth assuming a water-ice composition. Credit: John W. Holt, Ali Safaeinili, Jeffrey J. Plaut, James W. Head, Roger J. Phillips, Roberto Seu, Scott D. Kempf, Prateek Choudhary, Duncan A. Young, Nathaniel E. Putzig, Daniela Biccari, Yonggyu Gim.
Results are for SHARAD orbits 7219 (left) and 3672 (right). Credit: John W. Holt, Ali Safaeinili, Jeffrey J. Plaut, James W. Head, Roger J. Phillips, Roberto Seu, Scott D. Kempf, Prateek Choudhary, Duncan A. Young, Nathaniel E. Putzig, Daniela Biccari, Yonggyu Gim.

"Radar waves penetrate the surface and pass through materials that do not severely attenuate or scatter them. Reflections arise from interfaces with dielectric contrasts. [Shallow radar] SHARAD has penetrated the ∼2-km-thick polar layered deposits in both the north and south, detecting many internal reflectors (17, 18). Smaller targets can be more challenging because SHARAD's antenna pattern is broad, resulting in surface reflections up to a few tens of kilometers away from the suborbital point in rugged areas, versus only a few kilometers in smooth, flat areas. These off-nadir echoes can appear at time delays similar to those arising from subsurface interfaces, so steps are required to avoid misinterpreting this surface clutter as subsurface echoes. Synthetic-aperture data processing is used to improve along-track resolution to ∼300 m, greatly reducing along-track clutter and focusing the surface and subsurface features. We used the known topography of the surface and the radar geometry to model cross-track clutter together with nadir surface echoes [...]. Comparisons of radar sounding data with these synthetic surface echoes and the examination of possible surface echo sources in imagery (19) were undertaken for all cases [...]; such a procedure is a necessary part of radar sounding data interpretation in high-relief environments."[26]

The "Shallow Radar (SHARAD) (15) on the Mars Reconnaissance Orbiter (MRO) to probe the internal structure of several LDAs surrounding massifs on the eastern rim of the Hellas impact basin [first image at the right] where more than 90 LDA complexes flank steep topography (2, 6, 16). The southernmost LDA we studied (LDA-2, [figure at the upper right] has multiple lobes that coalesce to form a continuous deposit extending more than 20 km outward from a massif along ∼170 km of its margins."[26]

"Examination of radar data from SHARAD orbit 6830 where it crosses multiple [lobate debris aprons] LDAs in the eastern Hellas region [...] shows that the only radar reflections not matching simulated surface echoes occur where the spacecraft passes over each LDA [...]; therefore, these echoes are interpreted as arising from within or beneath the LDAs. In one case (LDA-2A), surface clutter is predicted near the terminus of the LDA, where it may obscure portions of a subsurface reflector that clearly extends farther inward below the LDA. LDA-2A and LDA-2B [image at the lower right] show evidence for multiple, closely spaced subsurface reflectors indicating the presence of at least one thin (∼70 m assuming a water-ice composition), distinct deposit below thicker deposits (up to 800 m)."[26]

## Radios

"Radio-echo soundings provide an effective tool for mapping the thermal regimes of polythermal glaciers on a regional scale. Radar signals of 320-370 MHz penetrate ice at sub-freezing temperatures but are reflected from the top of layers of ice which are at the melting point and contain water. Radar signals of 5-20 MHz, on the other hand, see through both the cold and the temperate ice down to the glacier bed. Radio-echo soundings at these frequencies have been used to investigate the thermal regimes of four polythermal glaciers in Svalbard: Kongsvegen, Uvérsbreen, Midre Lovénbreen and Austre Broggerbreen. In the ablation area of Kongsvegen, a cold surface layer (50-160m) thick was underlain by a warm basal layer which is advected from the temperate accumulation area. The surface ablation of this cold layer may be compensated by freezing at its lower cold-temperate interface. This requires that the free water content in the ice at the freezing interface is about 1% of the volume. The cold surface layer is thicker beneath medial moraines and where cold-based hanging glaciers enter the main ice stream. On Uvérsbreen the thermal regime was similar to that of Kongsvegen. A temperate hole was found in the otherwise cold surface layer of the ablation area in a surface depression between Kongsvegen and Uvérsbreen where meltwater accumulates during the summer (near the subglacial lake Setevatnet, 250 m a.s.l.). Lovénbreen was frozen to the bed at the snout and along all the mountain slopes but beneath the central part of the glacier a warm basal layer (up to 50m) thick was fed by temperate ice from two cirques. On Austre Broggerbreen, a temperate basal layer was not detected by radio-echo soundings but the basal ice was observed to be at the melting point in two boreholes."[27]

## Superluminals

The "emission phenomena observed in active galactic nuclei [includes] the production of compact radio sources separating at superluminal speeds".[28]

Outbursts "of cosmic ray electrons from the Galactic Center [may] penetrate the Galaxy relatively undamped and [may be able] to have a major impact on the Solar System through their ability to vaporize and inject cometary material into the interplanetary environment. [One] such 'superwave', passing through the Solar System toward the end of the Last Ice Age, [may have been] responsible for producing major changes in the Earth's climate and for indirectly precipitating the terminal Pleistocene extinction episode. The high concentration of 10Be, NO3-, Ir and Ni observed in Late Wisconsin polar ice are consistent with this scenario."[28]

## Plasma objects

"Hessdalen lights (HL) are unexplained light balls usually seen in the valley of Hessdalen, Norway. [...] HL [may be] formed by a cluster of macroscopic Coulomb crystals in a plasma produced by the ionization of air and dust by alpha particles during radon decay in the dusty atmosphere. Several physical properties (oscillation, geometric structure, and light spectrum) observed in HL phenomenon can be explained through the dust plasma model."[29]

"Geological and geochemical factors [affect] radon concentrations in dwellings located on permeable glacial sediments".[29]

## Gaseous objects

Methane bubbles are trapped in lake ice in Siberia in early autumn. Credit: Katey Walter, AP/Nature.

"Methane trapped in a special type of permafrost [in the image at the right] is bubbling up at rate five times faster than originally measured [...]."[30]

## Liquid objects

An aerial view shows thermokarst lakes in northeast Siberia. Credit: Dmitry Solovyov/REUTERS.
Increased thawing of frozen ground could create more thermokarst features, like this lake. Credit: Andrew Slater.

Def. "water that forms transition layers at mineral/water and mineral/water/ice interfaces in frozen ground"[3] is called interfacial water.

Def. "water occurring in unfrozen zones (taliks and cryopegs) within permafrost"[3] is called interpermafrost water.

At the right is an "aerial view [of] thermokarst lakes outside the town of Chersky in northeast Siberia [on] August 28, 2007."[31]

Def. "a lake occupying a closed depression formed by settlement of the ground following thawing of ice-rich permafrost or the melting of massive ice"[3] is called a thermokarst lake.

"Paul Lake is located [...] at the border of Wisconsin and the upper peninsula of Michigan, USA [...] The center of the property is positioned at 46°13'N 89°32'E, with an altitude range between 500 and 520 m."[32]

It "lies in [the] Northern Highland Province, which is the southernmost extension of the Canadian Shield. This province is characterized primarily by Pre-Cambrian bedrocks capped by a thin layer of sedimentary rocks left by the Paleozoic seas. On top of this formation are glacial deposits left by the Woodfordian and Valderan substages of the Wisconsinian glaciers. These glacial deposits are young and the drainage system is poorly developed. The surface deposits are characteristic of glacial retreat, consisting of infertile, sandy, pitted glacial out-wash or boulder and clay morainic deposits. As a result of their composition, the soils have a reduced capacity for cation exchange, leaving them very susceptible to acidification. Many of the lakes in this region are kettle lakes, others originate from irregular depressions in the ground moraine or were scoured out of the bedrock as the glaciers passed."[32]

"Paul Lake has a surface area of 1 ha, a mean depth of 6 m, and a maximum depth of 13 m [...]. All the water entering Paul Lake comes from atmospheric deposition and groundwater seepage. Paul Lake generally remains stratified year-long because of a biogenic meromixis [...] and has been classified mesotrophic [...]. The concentration of soluble reactive phosphorus remains low in surface waters year-long, but nutrient regeneration at the oxic/anoxic transition promotes phyto-planktonic blooms just above this interface [...]."[32]

## Rocky objects

A sense of the size of the glacial erratic can be estimated by noting the person standing in front of the boulder, on the left side. Credit: Lynda Dredge, Natural Resources Canada, Terrain Sciences Division, Geological Survey of Canada.
Glacial erratic (granite) is in the Polish Geological Institute, Warsaw. Credit: Robert Niedźwiedzki.

Def. "a mass of rock fragments and finer material, on a slope, that contains either an ice core or interstitial ice, and shows evidence of past, but not present, movement"[3] is called an inactive rock glacier.

Def. "a boulder swept from its place of origin by glacier advance or retreat and deposited elsewhere as the glacier melted; after glacial melt, the boulder might be stranded in a field or forest where no other rocks of its type or size exist"[3] is called a glacial erratic.

"A sense of the size of the glacial erratic [imaged at the right in northeastern Manitoba, Canada]] can be estimated by noting the person standing in front of the boulder, on the left side. This erratic, as well as neighboring ones, were carried by the Keewatian Ice Sheet."[3]

## Astrochemistry

A yedoma in Russia shows the thick layer of ice and carbon material exposed along a body of water. Credit: Vladimir Romanovsky.

Def. a "type of Pleistocene-age (formed 1.8 million to 10,000 years before present) permafrost that contains a significant amount of organic material with ice content of 50-90% by volume"[3] is called yedoma.

In the image at the right, a yedoma in Russia is a thick layer of ice and carbon material exposed along this body of water. "Thawing yedoma is a significant source of atmospheric methane."[3]

## Hydrogens

"Isotopic exchange between ice and water is found to take place in temperate glaciers. This exchange causes homogenization of deuterium in snow during summer thaws, together with a general increase in deuterium concentration."[33]

## Heliums

"We analyze helium (He) and neon (Ne) isotope data sets from the southeast Pacific sector of the Southern Ocean collected in 1992 and 1994 and describe a new method to estimate glacial meltwater fluxes independent of previous approaches."[34]

## Lithiums

"Taylor Valley glaciers have the lowest lithium concentrations and lightest δ7Li values in the McMurdo Dry Valleys aquatic system."[35]

"The δ7Li ratios of the glacial snow are among the lightest values observed in surface and groundwater samples (+0.8 to +2.9‰) and are unlike seawater (+30.8‰) (Tomascak, 2004; Rosner et al., 2007). This suggests that marine aerosol or marine-derived salts are not the primary sources of lithium to the glacier surfaces [...] Generally, geologic materials are isotopically lighter than natural water samples because of the preferential retention of 6Li in the solid phase. Despite this general relationship, Taylor Valley glacier snow samples have δ7Li signatures more like granite and rhyolite, which range from −1.2 to +8.0‰ (Tomascak, 2004). Although this wide range of Li isotopic values for granite does not conclusively mean the source to the glaciers is felsic rock, the snow samples are extremely light and resemble aluminosilicates. We therefore conclude that the major source of Li in the glacier ice is likely the dissolution of silicate materials."[35]

## Berylliums

"Good agreement is seen between the 14C (Fig. 8a) and 10Be (Fig. 8b) records, which confirms they are indeed measuring changes of the GCR flux, since their respective transport processes from the atmosphere to archive are completely different. After its formation, 14C is rapidly oxidised to 14CO2 and then enters the carbon cycle and may reach a tree-ring archive. On the other hand, 10Be attaches to aerosols and eventually settles as rain or snow, where it may become embedded in a stable ice-sheet archive. The correlation between high GCR flux and cold North Atlantic temperatures embraces the Little Ice Age, which is seen not as an isolated phenomenon but rather as the most recent of around ten such events during the Holocene. This suggests that the Sun may spend a substantial fraction of time in a magnetically-quiet state."[8]

## Borons

The "pH change for deep Pacific Ocean water associated with both the 3% increase in salinity resulting from the growth of the ice caps and the 700-m deepening of the lysocline9 are so small that they would lie within the uncertainty of pH reconstruction based on boron isotopes. If the glacial to Holocene drop in pH (0.3 units) suggested by the boron isotope measurements on benthic foraminifera was mainly accomplished by excess CaCO2 accumulation, then the alkalinity of deep Pacific water must have been ~10% higher during glacial time. As a result, the carbonate ion concentration of deep Pacific water during glacial time would have been ~100 µmol kg-1 higher than the present-day value, deepening the calcite saturation horizon by several kilometres."[36]

## Carbons

Here, carbon is trapped in permafrost. Credit: Katey Walter.

At the right is an image of yedoma.

"The shiny surface of the cliff represents massive ice wedges."[37]

"Most of the yedoma is in little-studied areas of northern and eastern Siberia. What makes that permafrost special is that much of it lies under lakes; the carbon below gets released as methane. Carbon beneath dry permafrost is released as carbon dioxide."[37]

"The big methane or carbon dioxide release hasn’t started yet, but it’s coming."[38]

In the image at the right, "Sergey Zimov, director of the Northeast Science Station in Siberia, [examines] a cross-section of yedoma, carbon trapped in permafrost along the bank of the Kolyma River in Siberia."[37]

"The dark sections in between are soil inclusions which contain ice-age organic carbon, left over from the Pleistocene steppe-tundra ecosystem."[37]

## Nitrogens

Nitrate (NO3-) concentrations in the [glacial and snowpack meltwaters] GSF lakes were 1-2 orders of magnitude higher than in [snowpack melt] SF lakes. Although nitrogen (N) limitation is common in alpine lakes, algal biomass was lower in highly N-enriched GSF lakes than in the N-poor SF lakes."[39]

## Oxygens

"Oxygen-isotope analyses of ice and firn from the Saskatchewan Glacier, Canada, and the Malaspina Glacier, Alaska, show that variations in ratios are likely to be of considerable value in glaciological research."[40]

## Fluorines

"Variations in sea-surface temperature (SST) occur in association with changes in the Earth's climate. [...] However, despite a large effort, the glacial record of SST is still controversial, especially in the tropics. [Studies] of foraminifera demonstrated that the interspecific variability in Mg/Ca ratios of planktonic shells is strongly correlated with water temperature at the estimated calcification depth [...] Similar correlations were also observed Sr/Ca and F/Ca [...] possibly suggesting an important role for temperature on the elemental composition of foraminifera. [...] F/Ca of foraminafera is governed primarily by biological processes."[41]

## Neons

"21Ne exposure ages [are] of erosional glaciogenic rock surfaces on nunataks in northern Victoria Land, Antarctica: i) in the Prince Albert Mountains and ii) near Mesa Range. These nunataks are located directly at the margin of the polar plateau and therefore provide an immediate record of ice volume changes of the East Antarctic Ice Sheet, not biased by ice shelf grounding or narrow valley sections downstream the outlet glaciers. The sampling locations overlook the present ice surface by less than 200 m, but were last covered by ice 3.5 Ma BP (minimum age, not corrected for erosion). This strongly indicates that the ice sheet has not been substantially thicker than today since at least the early Pliocene, which supports the hypothesis of a stable East Antarctic Ice Sheet."[42]

## Sodiums

"Glaciers in the Karakoram and western Himalaya (site 2 and 3) show high annual snow accumulation rates and high annual fluxes of calcium, sodium, chloride, sulfate, and nitrate."[43]

## Magnesiums

The "Mg content of shallow water benthic foraminifera can be used as an independent tracer of thermocline paleotemperatures, thereby allowing the reconstruction of the conditions at the ocean surface where the deep water masses originated. [...] The best precision of Mg/Ca thermometry may be achieved by using single species calibrations which avoid the scatter introduced by interspecific variability. In principle, the method should allow for analyzing δ 18O and Mg/Ca on the same samples, thus avoiding potential errors introduced by combining measurements on different organisms which could have lived at different depths or during different seasons. This is an important advantage over other approaches because using combined measurements of foraminiferal δ 18O, and Mg will allow for the estimation of both paleo-temperature and salinity which may provide the physical dataset necessary for reconstructing surface-water paleohydrography."[41]

## Aluminums

Sampling locations are in and along the upper 12 km of the Rio Quilcay, Cordillera Blanca, Peru. Main stream samples are labeled 1–24, tributaries A–F. Credit: Sarah K. Fortner, Bryan G. Mark, Jeffrey M. McKenzie, Jeffrey Bury, Annette Trierweiler, Michel Baraer, Patrick J. Burns, and LeeAnn Munk.
Tributary C feeds the Northeast Branch of the Rio Quilcay, Peru. This tributary has abundant ochreous precipitates. Credit: Sarah K. Fortner, Bryan G. Mark, Jeffrey M. McKenzie, Jeffrey Bury, Annette Trierweiler, Michel Baraer, Patrick J. Burns, and LeeAnn Munk.

"As Andean glaciers recede, there has been an increase in seasonal discharge and in catchments with the least glacierized area and a decrease in total annual discharge [...] Dry season examinations, including this study, are particularly important because during this period glacial melt provides up to 40% of the total discharge in the Cordillera Blanca (Mark et al., 2005). The dry season thus provides the greatest potential opportunity to evaluate water quality deterioration related to glacial retreat. [...] In the Cordillera Blanca, the exposure of fresh sulfide-rich lithologies by retreating glaciers (Wilson et al., 1967) is thus integral to the biogeochemistry of proglacial streams. [...] the dry season geochemistry of trace and minor elements was examined in the proglacial Rio Quilcay from within 1 km of its glacier origins to 12 km downstream."[44]

The "Rio Quilcay [is] a glacial-fed tributary to the Upper Rio Santa in the uppermost 12 km at elevations ranging from approximately 4800 to ~3800 m.a.s.l. [...] The sampled region of the Rio Quilcay receives glacial melt directly and indirectly from two proglacial lakes: Cuchillacocha and Tulpacocha. Geology in this region of the Cordillera Blanca includes pyrite schists and phyllite and pyrite-bearing quartzite intruded by a central granodiorite-tonalite batholith all overlain by clastic sediments deposited during glacial retreat (Wilson et al., 1967). Sulfide-rich lithologies are prevalent especially in the north-eastern high-altitude regions of the Cordillera Blanca (e.g. the Rio Quilcay Valley) with fresh exposures resulting from glacial scour (Wilson et al., 1967). Many headwaters in the Cordillera Blanca, including the Rio Quilcay and its tributaries, have ochreous precipitates"[44]

"Aluminum, Ca, Fe, K, Mn, Na, and Si were determined using an Optima 3000 DV Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES) using five calibration standards that bracketed the range of concentrations within the samples, excepting the three highest samples which were diluted 1:10 before analyses. Cobalt, Cu, Ni, Pb and Zn were determined on a Perkin–Elmer Sciex Elan 6000 Inductively Coupled Plasma-Mass Spectromenter (ICP-MS) also using five calibration standards, however with no sample dilution. All element results were drift corrected. Sulfate and NO3- were determined using a Dionex DX-120 ion chromatograph (IC). Only SO42- is reported because other anions fall near detections limits (DLs) in the higher elevation samples, or represent less than 5% of the charge balance in the pH < 4 streams."[44]

It "is likely that both the sulfide-rich lithology underlying the Rio Quilcay and the near-glacier sample locations enhanced sulfide weathering, and generated exceptionally high cation loads."[44]

"Elevated dissolved Al, Fe and Cu concentrations (6.1mg/L, 21.4 mg/L, 6.1 lg/L) were observed at site 11, 0.3 km immediately downstream of a moraine. Concentrations of these elements increased by more than four times the concentrations at site 10. Concentration gains were likely associated with glacier melt rapidly weathering minerals within the moraine (Brown, 2002)."[44]

"Tributary C also influenced the chemical composition of the stream immediately below its inflow at site 13. In fact, Fe reached the second highest concentration reported (12.8 mg/L) and dissolved Al, Mn, Co, Cu, Ni and Zn concentrations also increased above their upstream values. Tributary C overlays a region with enhanced sulfide mineral oxidation [image at the right]. Evidence for this includes a major cation: SO42- equivalent ratio of 1, and abundant algal mats covered with yellow and orange precipitates (Bigham et al., 1996). In addition, dissolved Al and Zn increased an additional 270% and 160% relative to site 13–14, respectively, and after the inflow of tributary D."[44]

## Silicons

"The relatively long-lived radionuclide of silicon, 32Si, finds important applications as a tracer for studying aqueous geochemistry, biogeochemical cycles of silicon in the oceans, and the chronology of glaciers and biogenic silica-rich sediments in lacustrine and marine environments."[45]

## Phosphoruses

"Phosphorus has been shown to be deficient in glacial environments, and thus is one of the limits on microbial growth and activity."[46]

## Sulfurs

"Both sulfur and oxygen isotopes of sulfate preserved in ice cores from Greenland and Antarctica have provided information on the relative sources of sulfate in the ice and their chemical transformation pathways in the atmosphere over various time periods."[47]

## Chlorines

"Chlorine-36 buildup dating has successfully been applied to glacial moraines in the eastern Sierra Nevada (California) and to lava flows and meteorite impact craters in the western United States."[11]

## Argons

"Nitrogen and argon isotopes in trapped air in Greenland ice show that the Greenland Summit warmed 9 ± 3°C over a period of several decades, beginning 14,672 years ago."[48]

## Potassiums

"Potassium and calcium concentrations are high relative to other cations in glacial water, probably due to dissolution of soluble trace phases, such as carbonates, exposed by comminution, and cation leaching from biotite."[49]

## Calciums

"Heinrich Layers are found in the North Atlantic Ocean as well-constrained markers of catastrophic iceberg surges from the Pan-Atlantic ice sheets during the last glacial cycle. Their physical and geochemical characteristics [...] are predominantly due to the source sediments of the ice-rafted debris (IRD) on the one hand (magnetic susceptibility, color, carbonate content) and the response of the palaeo-environment on the other hand (carbonate content, foraminiferal assemblage)."[50]

"Sediment cores in the Porcupine Seabight (West off Ireland) have shown the presence of Heinrich Events without the diagnostic changes in magnetic susceptibility (MS) [...] the concentration of ice-rafted debris (commonly referred to as the fraction > 150 μm) increases towards the culmination of HL2, marked by an increase in MS, [X-ray fluorescence] XRF Ca and the percentage of N. pachyderma s."[50]

The "zone where the density increases is marked by a cloud of fine and highly dense particles surrounding the IRD. [The] fine clayey “background” matrix throughout the core [consists] of zoned dolomites. [...] the mineralogical analyses [suggest] a predominant volcanic source for the magnetic susceptibility. [Both] XRF Fe and Ti show significant decreases near the HL culmination".[50]

## Scandiums

"Neutron activation analysis was used to deterimne the total [lanthanum] La and [scandium] Sc content of three soils developed from loess-capped glacial till. The profiles were classified as Gray-Brown Podzolics (Hapludalfs) overlying paleosols developed in Rockain till. The total La content in the less than 250µ fraction of these soils ranged from 18.1 to 37.1 ppm, with an average content of 23.7 ppm in the loess and 28.5 ppm in the glacial till. Total Sc in the soils ranged from 5.1 to 10.9 ppm with average contents of 6.5 and 9.0 ppm in the loess and glacial till, respectively. Translocation by pedogenic processes was indicated by the accumulation of these elements in the argillic B horizons. Correlation coefficients of La and Sc with clay percentages in the profiles were 0.79 and 0.88, respectively."[51]

## Titaniums

"Till collected from surface exposures within the valley of the Hudson River south of the Sanford Hill magnetite-ilmenite ore deposit in the Adirondack Mountains of New York is composed primarily of plagioclase, pyroxene, garnet, magnetite, and ilmenite [FeTiO3]. The concentration of magnetite and ilmenite in bulk till both decrease exponentially with increasing distance south of the ore bodies because of dilution by the entrainment of plagioclase and garnet + pyroxene from the bedrock and from older till deposits in the valley. Evidence for comminution of magnetite and ilmenite is provided by decreasing abundances of these minerals in the coarse fractions (1000-125 µm) and corresponding increases in the fine fraction (<125 µm). The apparent rate of comminution of ilmenite as a function of transport distance is significantly greater than that of magnetite, which causes ilmenite to be concentrated in the fine fraction of till compared to magnetite."[52]

## Vanadiums

"The average contents of vanadium in the glacial and alluvial deposits of the Altai are comparable with those of Transbaikalia."[53]

"In Transbaikalia, elevated vanadium contents are characteristic of granitic gneisses (324 ppm), syenites (204 ppm), and granitoids (162 ppm), whereas basalts are poor in vanadium (83 ppm) [2]."[53]

"The lowest values are characteristic of glacial sandy loams and alluvial deposits."[53]

## Chromiums

For "the Pinchi Mine area [...] mercury ore was transported over a distance of 12 km, as measured in the clay-sized fraction (< 0.002 mm) of till, and could have been transported over 24 km according to heavy mineral concentrates (specific gravity >3.3) of this same sediment. Antimony, chromium, and nickel dispersal trains were also detected in the region."[54]

## Manganeses

"In glacial marine sediments from the St. Lawrence estuary, iron varies between 1.32 and 5.42%, manganese between 0.043 and 0.28%, and titanium between 0.31 and 0.64%."[55]

"Analyses of individual sediment size-fractions show that Fe, Mn, and Ti concentrations generally increase with decreasing grain size."[55]

## Irons

"Dissolved iron (DFe) and total dissolvable Fe (TDFe) were measured in January–February 2009 in Pine Island Bay, as well as in the Pine Island and Amundsen polynyas (Amundsen Sea, Southern Ocean). Iron (Fe) has been shown to be a limiting nutrient for phytoplankton growth, even in the productive continental shelves surrounding the Antarctic continent."[56]

"At the southern end of Pine Island Bay, the [Circumpolar Deep Water] CDW upwelled under the Pine Island Glacier, bringing nutrients (including Fe) to the surface and melting the base of the glacier."[56]

"The largest source was Fe input from the PIG, which could satisfy the total Fe demand by the phytoplankton bloom by lateral advection of Fe over a range of 150 km from the glacier."[56]

## Cobalts

The distribution of the concentrations of dissolved cobalt (Cod) observed in May 1994 (filled circles) and July-August 1995 (shaded squares) are presented. Credit: Charles-Philippe Lienemann, Martial Taillepert, Didier Perret, and Jean-François Gaillard.

"On glacier surfaces conditions [...] exist for aerosols and airborne dust deposited with anthropogenic and natural radionuclides attached on their surfaces. In the course of agglomeration processes initiated by melting and redistribution, these particles may concentrate in small depressions, ice pockets, ablation edges etc. and form substances called cryoconites ('ice dust'). As there is no other matrix than the original aerosol particles, cryoconites are a sink for radionuclides and airborne pollutants and their activity levels are among the highest produced by natural processes observed in environmental media. 137Cs activities found on glaciers in the Austrian alps are between 255 and 136.000 Bq/kg and predominantly derived from Chernobyl, but also from global fallout. Further anthropogenic radionuclides detected are 134Cs, 90Sr, 238,239+240Pu, 241Am, 125Sb, 154Eu, 60Co and 207Bi [in] combination with the naturally occurring radionuclides 7Be and 210Pb and isotopic ratios such as 134Cs/137Cs".[57]

The "concentration of dissolved Mn and Co [figure at the right] increase sharply across the oxic/anoxic transition, from 5 to 5.5 m depth. The concentration of Co rises from detection limit, when O2 is still present, to 6.8 nM and 12 nM, respectively, for May 1994 and July-August 1995."[32]

In the oxic mixolimnion, dissolved Co remains primarily under its free hydrated form (Co[H2]2+6, whereas in the anoxic bottom waters it seems to be primarily present as a sulfide complex (CoS0).

## Nickels

In "the Arctic Archipelago and in parts of northern Baffin Island and Boothia Peninsula the glaciers were apparently cold-based and effected little erosion of the preglacial landscape."[58]

Nickel "occurs in concentrations far above the crustal average in basic and ultrabasic igneous rocks. Where a glacier has eroded nickel-enriched zones in basalts, gabbros, serpentinized periodotites, and similar basic or ultrabasic igneous rocks, or their metamorphic equivalents, nickel-enriched glacial debris may be spread out in the form of a glacial dispersal train."[58]

"Nickel occurs in unweathered glacial sediments in the same mineral phases as those in which it is found in rocks."[58]

"Where a glacier has overridden ultrabasic rocks, nickel may still be present in sulfide grains, but its presence in silicates such as olivine, serpentine, amphiboles, biotite, and talc, can lead to very high bulk nickel compositions in till or derived sediments."[58]

## Coppers

This is a Landsat Thematic Mapper image with overlain geological structures. Credit: I.M. Kettles, A.N. Rencz, and S.D. Bauke.

"Approximately five million tonnes were mined from native copper deposits in Michigan. Copper masses from the Michigan deposits were transported by the Pleistocene glaciers. Areas on the copper surfaces which appear to represent glacial abrasion show minimal corrosion."[59]

"A group of pixel areas north of Lake Superior [in the Landsat image on the right] take the form of a linear band which lies along the northern edge of the Port Coldwell Complex (D). [...] there are numerous Cu showings along the northern edge of the Port Coldwell complex (Ontario Division of Mines, 1971)."[60]

## Zincs

"Satellite images taken over the past several decades show the dramatic disappearance of ice, including on the island’s inland areas, where the ice fields can in places be up to three and a half kilometers deep."[61]

"Along with uranium, zinc, iron ore, copper and gold, Greenland’s ancient rocks also harbor large quantities of those minerals known as “rare earth,” among them lanthanum, cerium, neodymium, praesodymium, terbium and yttrium."[61]

## Galliums

Gallium "enrichments are observed in the deep waters of the Norwegian Sea and Iceland Basin."[62]

"If northern deep water formation occurs at lower latitudes during glacial periods, the amount of sediment resuspension in the formation areas is likely to be affected with concomitant effects on the trace element content of newly formed northern-source deep waters."[62]

## Germaniums

"Data from three glacial meltwater streams draining Mt. Tronador in the southern Argentine Andes (72°W, 41°S) show that subglacial pyrite oxidation and the subsequent precipitation of iron oxides strongly influence dissolved phosphate concentrations but do not appear to affect dissolved germanium concentrations."[63]

"Dissolved Ge appears to show no preferential sorption relative to dissolved silica, in contrast to the speculation that Ge preferentially sorbs on fresh iron hydroxyoxide surfaces."[63]

## Mercuries

"Abundant cinnabar (HgS) mineralization is associated with the Pinchi Fault in central British Columbia. [...] The mercury content of till (a sediment type directly deposited by glaciers) in the area of this fault is primarily controlled by the occurrence of cinnabar mineralization in bedrock an the direction of ice flow. Cinnabar-bearing bedrock was eroded by glaciers, transported in the direction of ice flow, and deposited "down-ice" from its source."[54]

## Ions

"Total-Fe (TFe) and total-P (TP) concentrations are high in all three glacial streams, but the ratios of soluble reactive phosphate (SRP) to TP are very different. The Upper Manso Stream that drains the Manso Glacier has relatively low SRP (0.01-0.23 PM), representing a small fraction of its TP (O. l-5%). The SRP of the two streams draining smaller side glaciers (0.12-0.69 PM) represents a much larger portion of their TP (20-32%)."[63]

"TFe, dissolved sulfate, and δ 34S data suggest that pyrite oxidation is the most likely weathering reaction contributing sulfate to the Upper Manso Stream but not to the two smaller glacial-fed streams, in which atmospheric inputs can account for all of the sulfate."[63]

## Compounds

The diagram describes how methane leaks from sea beds. Credit: Katey Walter, University of Alaska at Fairbanks.

The diagram at the right describes how methane (CH4) leaks from sea beds.

"Methane is far more powerful in trapping heat, but only lasts about a decade before it dissipates into carbon dioxide and other chemicals. Carbon dioxide traps heat for about a century."[30]

## Atmospheres

Def. "an atmospheric circulation pattern in which the atmospheric pressure over the polar regions varies in opposition with that over middle latitudes (about 45 degrees N) on time scales ranging from weeks to decades; the oscillation extends through the depth of the troposphere, and from January to March, it extends upward into the stratosphere where it modulates in the strength of the westerly vortex that encircles the arctic polar cap region; the north atlantic oscillation and arctic oscillation are different ways of describing the same phenomenon"[3] is called an arctic oscillation.

## Materials

This is a photograph in natural light of the vertically oriented pores in congelation ice. Credit: Ted Maksym, United States Naval Academy.

Def. "an advanced form of new ice that forms as a stable sheet with a smooth bottom surface"[3] is called congelation ice.

At the right is a "photograph in natural light of the vertically oriented pores in congelation ice."[3]

## Meteorites

Talefre Glacier on Mont Blanc Massif in the European Alps sported a prominent glacier table when this undated photograph was taken. Credit: Cairrar.

Def. "a rock that resides on a pedestal of ice; formed by differential ablation between the rock-covered ice and surrounding bare ice"[3] is called a glacier table.

"Talefre Glacier on Mont Blanc Massif in the European Alps sported a prominent glacier table when this undated photograph was taken. The rock protected the ice directly below it from melting, resulting in the characteristic pedestal that remains after the surrounding ice melts. For scale, note the man standing behind and to the left of the pedestal."[3]

When the glacier table top strikes the Earth with the melting of the pedestal, is the rock a meteorite?

## Spectrometers

"Helium isotopes (3He and 4He) were measured using a dedicated He isotope mass spectrometer (MM5400)."[34]

"Neon isotopes (20Ne and 22Ne) were measured simultaneously on a quadrupole mass spectrometer (Balzers, QMG 112)."[34]

## Planetary astronomy

In this photograph from 1969, small glaciers flow into the larger Columbia Glacier from mountain valleys on both sides. Credit: United States Geological Survey.

Def. a "glacier that has one or more tributary glaciers that flow into it"[3] is called a branched-valley glacier.

"In this photograph from 1969 [at the right], small glaciers flow into the larger Columbia Glacier from mountain valleys on both sides. Columbia Glacier flows out of the Chugach Mountains into Columbia Bay, Alaska."[3]

## Sun

"We have postulated complex thermonuclear reactions occurring deep inside the stars as the source of stellar energy and the natural progression of these reactions as the basis of stellar evolution. Yet our first-hand knowledge of stellar structure is limited, consisting largely of surface observations. How certain, then, is our understanding of the processes governing synthesis of the elements deep within fiery stellar cores?"[15]

"The standard stellar theory depicts the main sequence as a relatively simple, steady-state period in a star’s evolution. Thus, any failure of the standard theory to predict the present behavior of the sun could indicate a serious flaw in our stellar physics."[15]

"We believe that there is disturbing and controversial evidence that such flaws may exist. Part of the evidence is provided by the earth’s climatic history, and part by a contemporary experiment that directly monitors the thermonuclear reactions in the solar core. The evidence suggests that variations in the rate of solar energy generation occur, perhaps induced by periodic mixing of the core."[15]

"According to the standard model, the solar luminosity, or the rate at which the sun radiates electromagnetic energy, has remained constant apart from a monotonic increase of 30 per cent over the lifetime of the sun. This increase tracks the rises in the temperature and helium-4 abundance of the solar core as its supply of hydrogen is depleted."[15]

"To the extent that the earth’s geologic and biologic history provides a record of the solar luminosity, we can check the predictions of the standard model. There appear to be a number of inconsistencies. The low initial luminosity predicted by the standard model suggests a primordial climate for the earth quite different from today’s, yet the paleoclimatic record shows no evidence for any significant climatic evolution."[15]

"Sunspot activity has waxed and waned in a regular eleven-year cycle since 1715. In the preceding seventy years, termed the Maunder Minimum, sunspot activity was nearly absent, and, according to European records, persistently cold weather took its toll on crops. Corroborating evidence for a quiescent sun during the Maunder Minimum exists in the reduced brightness and extent of the sun’s corona, a diminished number of auroral displays, and an increased abundance of carbon-14 in the atmosphere."[15]

A "diminished number of auroral displays, and an increased abundance of carbon-14 in the atmosphere. [...] result from a decreased emission of charged particles by the sun."[15]

The "warm Twelfth Century Grand Maximum and the cold Sporer Minimum of 1450 to 1540, also are correlated with periods of increased or decreased solar activity."[15]

The "eleven-year cycle of solar magnetic field reversals, which govern sunspot activity, is thought to be maintained by dynamo action associated with convection and rotation. Thus, the climatic anomalies of the past millenium may indicate merely some lack of detail in standard stellar theory rather than a basic flaw. However, these phenomena do demonstrate that variations in the solar output have terrestrial consequences. A more provocative question then becomes whether there exist some climatic tests of solar behavior over the longer time scales that might characterize possible changes in the solar core, where the basic process of energy generation occurs."[15]

"Evidence of long-term climatic variability is found in the repeated advance and retreat of continental glaciers and in the quasi-periodic occurrence of major glacial epochs. The strong correlation between stages of continental glaciation and the periods (10,000 to 100,000 years) of the earth’s orbital parameters (its eccentricity, obliquity, and precession) suggest that these changes are governed by the earth’s orbital geometry rather than solar phenomena."[15]

"In the last billion years major glacial epochs lasting several million years have occurred regularly, separated by warmer periods lasting several hundred million years. The latest glacial epoch, the Pleistocene, began just three million years ago, and the proximity of its onset indicates that the present is an atypical time in the earth’s climatic history."[15]

"The duration of the glacial epochs is comparable to the thermal diffusion time of the solar core. Their spacing corresponds to a fundamental hydrogen-burning scale, the time required for the ratio of helium-3 to hydrogen [...] to reach equilibrium over an appreciable fraction of the solar core. These observations have stimulated development of a number of nonstandard models in which variations in the solar output are coupled to these thermal and nuclear time scales."[15]

"The duration and spacing of the transient mixing stages nicely match those of the glacial epochs. It is also widely believed that reduction of the sun’s luminosity by 5 per cent would induce major climatic changes and that periodic mixing, by softening the long-term luminosity increase, would yield a primordial value more acceptable than that of the standard model."[15]

Extinct "Martian rivers indicate an ice-age climate for Mars coincident with the earth’s Pleistocene epoch, which further suggests the existence of extraterrestrial controls."[15]

The "suggested mode of solar variability leaves unexplained other glacial phenomena, such as the steady cooling of the oceans in the ten million years preceding the Pleistocene epoch."[15]

## Earth

Overview of the Cryosphere and its larger components, from the UN Environment Programme Global Outlook for Ice and Snow. Credit: .
A satellite composite image shows the ice sheet of Antarctica Credit: Dave Pape.

The only current ice sheets are in Antarctica and Greenland; during the last glacial period at Last Glacial Maximum (LGM) the Laurentide ice sheet covered much of North America, the Weichselian ice sheet covered northern Europe and the Patagonian Ice Sheet covered southern South America.

## Mars

This is the south polar cap of Mars as it appeared to the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) on April 17, 2000. Credit: NASA/JPL/Malin Space Science Systems (MSSS).

"This is the south polar cap of Mars as it appeared to the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) on April 17, 2000. In winter and early spring, this entire scene would be covered by frost. In summer, the cap shrinks to its minimum size, as shown here. Even though it is summer, observations made by the Viking orbiters in the 1970s showed that the south polar cap remains cold enough that the polar frost (seen here as white) consists of carbon dioxide. Carbon dioxide freezes at temperatures around -125° C (-193° F). Mid-summer afternoon sunlight illuminates this scene from the upper left from about 11.2° above the horizon. Soon the cap will experience sunsets; by June 2000, this pole will be in autumn, and the area covered by frost will begin to grow. Winter will return to the south polar region in December 2000. The polar cap from left to right is about 420 km (260 mi) across."[64]

## Callisto

This image of Callisto from NASA's Galileo spacecraft, taken in May 2001, is the only complete global color image of Callisto obtained by Galileo. Credit: NASA/JPL/DLR(German Aerospace Center).
Views of eroding (top) and mostly eroded (bottom) ice knobs (~100 m high), possibly formed from the ejecta of an ancient impact. Credit: NASA/JPL/Arizona State University, Academic Research Lab.

Scientists believe the brighter areas of Original research/Callisto are mainly ice and the darker areas are highly eroded, ice-poor material.

Compounds detected spectroscopically on the surface include water ice, carbon dioxide, silicates, and organic compounds.

Small, bright patches of pure water ice are intermixed with patches of a rock–ice mixture and extended dark areas made of a non-ice material.[65][66]

Near-infrared spectroscopy has revealed the presence of water ice absorption bands at wavelengths of 1.04, 1.25, 1.5, 2.0 and 3.0 micrometers.[65]

The cratered plains constitute most of the surface area and represent the ancient lithosphere, a mixture of ice and rocky material.

Small patches of pure water ice with an albedo as high as 80% are found on the surface of Callisto, surrounded by much darker material.[65] High-resolution Galileo images showed the bright patches to be predominately located on elevated surface features: crater rims, scarps, ridges and knobs.[65] They are likely to be thin water frost deposits. Dark material usually lies in the lowlands surrounding and mantling bright features and appears to be smooth. It often forms patches up to 5 km across within the crater floors and in the intercrater depressions.[65]

Views of eroding (top) and mostly eroded (bottom) ice knobs (~100 m high), possibly formed from the ejecta of an ancient impact are shown in the second images at left.

"The knobby terrain seen throughout the top inset is unlike any seen before on Jupiter's moons. The spires are very icy but also contain some darker dust. As the ice erodes, the dark material apparently slides down and collects in low-lying areas. Over time, as the surface continues to erode, the icy knobs will likely disappear, producing a scene similar to the bottom inset. The number of impact craters in the bottom image indicates that erosion has essentially ceased in the dark plains shown in that image, allowing impact craters to persist and accumulate."[67]

"The knobs are about 80 to 100 meters (260 to 330 feet) tall, and they may consist of material thrown outward from a major impact billions of years ago. The areas captured in the images lie south of Callisto's large Asgard impact basin."[67]

"The smallest features discernable in the images are about 3 meters (10 feet) across."[67]

## Europa

This image shows two views of the trailing hemisphere of Jupiter's ice-covered satellite, Europa. The left image shows the approximate natural color appearance of Europa. Credit: NASA/Deutsche Forschungsanstalt für Luft- und Raumfahrt e.V., Berlin, Germany.

Europa's surface is composed of water ice and is one of the smoothest in the Solar System.[68] The crust is estimated to have undergone a shift of 80°, nearly flipping over (see true polar wander), which would be unlikely if the ice were solidly attached to the mantle.[69]

## Ganymede

Image of Ganymede's anti-Jovian hemisphere is taken by the Galileo probe. Lighter surfaces, such as in recent impacts, grooved terrain and the whitish north polar cap at upper right, are enriched in water ice. Credit: .
Voyager 2 image mosaic of Ganymede's anti-Jovian hemisphere. The ancient dark area of Galileo Regio lies at the upper right. It is separated from the smaller dark region of Marius Regio to its left by the brighter and younger band of Uruk Sulcus. Fresh ice ejected from the relatively recent Osiris Crater created the bright rays at the bottom. Credit: .

"Ganymede's blue color comes from the absorption of water ice on its surface at longer wavelengths."[70]

Ganymede is composed of approximately equal amounts of silicate rock and water ice.

The average density of Ganymede, 1.936 g/cm3, suggests a composition of approximately equal parts rocky material and water, which is mainly in the form of ice.[71] The mass fraction of ices is between 46–50%, slightly lower than that in Callisto.[72] Some additional volatile ices such as ammonia may also be present.[72][73]

Water ice seems to be ubiquitous on the surface, with a mass fraction of 50–90%,[71] significantly more than in Ganymede as a whole. Near-infrared spectroscopy has revealed the presence of strong water ice absorption bands at wavelengths of 1.04, 1.25, 1.5, 2.0 and 3.0 μm.[74] The grooved terrain is brighter and has more icy composition than the dark terrain.[75]

The forces that caused the strong stresses in the ganymedian ice lithosphere necessary to initiate the tectonic activity may be connected to the tidal heating events in the past, possibly caused when the satellite passed through unstable orbital resonances.[71][76] The tidal flexing of the ice may have heated the interior and strained the lithosphere, leading to the development of cracks and horst and graben faulting, which erased the old, dark terrain on 70% of the surface.[71][77] The formation of the grooved terrain may also be connected with the early core formation and subsequent tidal heating of the moon's interior, which may have caused a slight expansion of Ganymede by 1–6% due to phase transitions in ice and thermal expansion.[71]

Ganymede also has polar caps, likely composed of water frost. The frost extends to 40° latitude.[78] These polar caps were first seen by the Voyager spacecraft. Theories on the caps' formation include the migration of water to higher latitudes and bombardment of the ice by plasma. Data from Galileo suggests the latter is correct.[79]

Additional evidence of the oxygen atmosphere comes from spectral detection of gases trapped in the ice at the surface of Ganymede. The detection of ozone (O3) bands was announced in 1996.[80] In 1997 spectroscopic analysis revealed the dimer (or diatomic) absorption features of molecular oxygen. Such an absorption can arise only if the oxygen is in a dense phase. The best candidate is molecular oxygen trapped in ice. The depth of the dimer absorption bands depends on latitude and longitude, rather than on surface albedo—they tend to decrease with increasing latitude on Ganymede, while O3 shows an opposite trend.[81] Laboratory work has found that O2 would not cluster or bubble but dissolve in ice at Ganymede's relatively warm surface temperature of 100 K.[82]

Heavy ions continuously precipitate on the polar surface of the moon, sputtering and darkening the ice.[83]

## Geography

This shows the terminus of Holgate Glacier. Credit: Janet Beitler, National Snow and Ice Data Center.

Def. "a line drawn through geographical points recording equal amounts of precipitation during a specific period"[3] is called an isohyet.

Def. a "mountain glacier that terminates in the ocean"[3] is called a tidewater glacier.

## Recent history

The image from 1936 shows explorers on Skillet Glacier. Credit: Janet Beitler.
Skillet Glacier on Mount Moran is at right. On the left is Falling Ice Glacier. Credit: Acroterion.{{free media}}

The recent history period dates from around 1,000 b2k to present.

Def. a "crevasse that separates flowing ice from stagnant ice at the head of a glacier"[3] is called bergschrund.

The image at the right from 1936 shows explorers on Skillet Glacier. "Bergschrund is visible as the dark band of ice in the background."[3]

In the image on the left is the summit of Mount Moran, Grand Teton National Park, Wyoming, USA, showing the black diabase dike and Skillet Glacier.

## Physics

Def. "combined processes (such as sublimation, fusion or melting, evaporation) which remove snow or ice from the surface of a glacier or from a snow-field; also used to express the quantity lost by these processes [or to a] reduction of the water equivalent of a snow cover by melting, evaporation, wind and avalanches"[3] is called ablation.

## Sciences

Def. "temperatures generally below -50 degrees Celsius, but usually to temperatures within a few degrees of absolute zero (-273 degrees Celsius)"[3] is called cryogenic temperature.

Def. "the study of the genesis, structure and lithology of frozen earth materials"[3] is called cryolithology.

Def. "the study of soils at temperatures below 0 degrees Celsius, with particular reference to soils subject to intensive frost action, and to soils overlying permafrost"[3] is called cryopedology.

## Technology

An under water, under ice bubble trap is installed on a lake in Siberia. Credit: Katey Walter.

Here at the right an under water, under-ice bubble trap is installed in a lake in Siberia.

## References

1. Richard S. Williams, Jr.. 1987 Annals of Glaciology. 9. International Glaciological Society. p. 255. Retrieved 7 February 2011.
2. Richard B. Stothers (June 1984). "The Great Tambora Eruption in 1815 and Its Aftermath". Science 224 (4654): 1191-8. Retrieved 2014-06-23.
3. Jane Beitler (19 September 2014). Cryosphere Glossary. National Snow and Ice Data Center. Retrieved 2014-09-17.
4. G. S. Boulton, G. D. Smith, A. S. Jones and J. Newsome (June 1985). "Glacial geology and glaciology of the last mid-latitude ice sheets". Journal of the Geological Society 142 (3): 447-74. doi:10.1144/gsjgs.142.3.0447. Retrieved 2014-06-23.
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6. Jan-Gunnar Winther (June 1993). "Landsat TM derived and in situ summer reflectance of glaciers in Svalbard". Polar Research 12 (1): 37-55. doi:10.1111/j.1751-8369.1993.tb00421.x. Retrieved 2014-09-27.
7. G. C. Collins, J. W. Head III, R. T. Pappalardo, and N. A. Spaun (25 January 2000). "Evaluation of models for the formation of chaotic terrain on Europa". Journal of Geophysical Research 105 (E1): 1709-16. Retrieved 2014-08-26.
8. Jasper Kirkby (November 01, 2007). "Cosmic rays and climate". Surveys in Geophysics 28 (5-6): 333-75. doi:10.1007/s10712-008-9030-6. Retrieved 2014-09-19.
9. Donald M. Hunten (February 12, 1993). "Atmospheric Evolution of the Terrestrial Planets". Science 259 (5097): 915-20. Retrieved 2014-09-21.
10. Rhodes W. Fairbridge (1984). Planetary periodicities and terrestrial climate stress, In: Climatic Changes on a Yearly to Millennial Basis. New York: Springer. pp. 509–20. doi:10.1007/978-94-015-7692-5_49. Retrieved 2014-09-29.
11. F.M. Phillips, D.Q. Bowen, and E. Elmore (1994). "Surface exposure dating of glacial features in Great Britain using cosmogenic chlorine-36: preliminary results". Mineralogical Magazine 58A: 722-3. Retrieved 2014-09-21.
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## Further reading

• Richard S. Williams, Jr.. 1987 Annals of Glaciology. 9. International Glaciological Society. p. 255. Retrieved 7 February 2011.