Ice sheet

A satellite composite image of Antarctica
Aerial view of the ice sheet on Greenland's east coast
Map of Greenland
Carbon stores and fluxes in present-day ice sheets (2019), and the predicted impact on carbon dioxide (where data exists).
Estimated carbon fluxes are measured in Tg C a−1 (megatonnes of carbon per year) and estimated sizes of carbon stores are measured in Pg C (thousands of megatonnes of carbon). DOC = dissolved organic carbon, POC = particulate organic carbon.

Ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than 50000 km2.

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Last Glacial Period

The Last Glacial Period (LGP), also known colloquially as the last ice age or simply ice age, occurred from the end of the Eemian to the end of the Younger Dryas, encompassing the period years ago.

Chronology of climatic events of importance for the last glacial period (about the last 120,000 years)
Artist's impression of the last glacial period at glacial maximum
Vegetation types at time of Last glacial maximum
Last glacial period, as seen in ice core data from Antarctica and Greenland
Europe during the last glacial period
Violet: extent of the Alpine ice sheet in the Würm glaciation. Blue: extent in earlier ice ages.
Map of Pleistocene lakes in the Great Basin of western North America, showing the path of the Bonneville Flood along the Snake River
Map showing the extent of the glaciated area in Venezuelan Andes during the Mérida glaciation
Map showing the extent of the Patagonian ice sheet in the Strait of Magellan area during the LGP: Selected modern settlements are shown with yellow dots.
Modelled maximum extent of the Antarctic ice sheet 21,000 years before present

The LGP is often colloquially referred to as the "last ice age", though the term ice age is not strictly defined, and on a longer geological perspective, the last few million years could be termed a single ice age given the continual presence of ice sheets near both poles.

Sea level rise

Tide gauge measurements show that the current global sea level rise began at the start of the 20th century.

Satellite observations of sea level rise from 1993 to 2021.
Historical sea level reconstruction and projections up to 2100 published in 2017 by the U.S. Global Change Research Program for the Fourth National Climate Assessment. RCP2.6 is the scenario where emissions peak before 2020, RCP4.5 the one where they peak around 2040, and RCP8.5 the one where they keep increasing.
Different sea level rise projections for the 21st century
Map of the Earth with a long-term 6 m sea level rise represented in red (uniform distribution, actual sea level rise will vary regionally and local adaptation measures will also have an effect on local sea levels).
Earth lost 28 trillion tonnes of ice between 1994 and 2017, with melting grounded ice (ice sheets and glaciers) raising the global sea level by 34.6 ±3.1 mm. The rate of ice loss has risen by 57% since the 1990s−from 0.8 to 1.2 trillion tonnes per year.
Ocean heat content (OHC) between 1957 and 2017, NOAA
The Ross Ice Shelf, Antarctica's largest, is about the size of France and up to several hundred metres thick.
grounding zone
Greenland 2007 melt, measured as the difference between the number of days on which melting occurred in 2007 compared to the average annual melting days from 1988 to 2006
Trends in land water storage from GRACE observations in gigatons per year, April 2002 to November 2014 (glaciers and ice sheets are excluded).
A stripe graphic assigns ranges of annual sea level measurements to respective colors, with the baseline white color starting in 1880 and darker blues denoting progressively greater sea level rise.
Jason-1 continued the sea surface measurements started by TOPEX/Poseidon. It was followed by the Ocean Surface Topography Mission on Jason-2, and by Jason-3
Between 1993 and 2018, the mean sea level has risen across most of the world ocean (blue colors).
Tidal flooding in Miami during a king tide (October 17, 2016). The risk of tidal flooding increases with sea level rise.
Major cities threatened by sea level rise. The cities indicated are under threat of even a small sea level rise (of 1.6 foot/49 cm) compared to the level in 2010. Even moderate projections indicate that such a rise will have occurred by 2060.
Bramble Cay melomys Melomys rubicola. In 2016 declared extinct on Bramble Cay, where it had been endemic, and likely also globally extinct, with habitat loss due to sea level rise being the root cause.
Placard "The sea is rising", at the People's Climate March (2017).
Beach nourishment in progress in Barcelona.
Changes in sea level since the end of the last glacial episode

This acceleration is due mostly to climate change, which heats (and therefore inflates) the ocean and which melts the land-based ice sheets and glaciers.


Water frozen into a solid state, typically forming at or below temperatures of 0 degrees Celsius or 32 degrees Fahrenheit.

The three-dimensional crystal structure of H2O ice Ih (c) is composed of bases of H2O ice molecules (b) located on lattice points within the two-dimensional hexagonal space lattice (a).
Pressure dependence of ice melting
Log-lin pressure-temperature phase diagram of water. The Roman numerals correspond to some ice phases listed below.
An alternative formulation of the phase diagram for certain ices and other phases of water
Frozen waterfall in southeast New York
Feather ice on the plateau near Alta, Norway. The crystals form at temperatures below −30 °C (−22 °F).
Ice on deciduous tree after freezing rain
A small frozen rivulet
Ice formation on exterior of vehicle windshield
An accumulation of ice pellets
A large hailstone, about 6 cm in diameter
Snowflakes by Wilson Bentley, 1902.
Harvesting ice on Lake St. Clair in Michigan, c. 1905
Layout of a late 19th-Century ice factory
Loss of control on ice by an articulated bus
Channel through ice for ship traffic on Lake Huron with ice breakers in background
Rime ice on the leading edge of an aircraft wing, partially released by the black pneumatic boot.
Skating fun by 17th century Dutch painter Hendrick Avercamp
Ice pier during 1983 cargo operations. McMurdo Station, Antarctica

Sufficiently thin ice sheets allow light to pass through while protecting the underside from short-term weather extremes such as wind chill.

Ice stream

Velocity map of Antarctica. Ice streams can be seen with increasing speeds (blue-yellow-white) flowing toward the coast.
Radarsat image of ice streams flowing into the Filchner-Ronne Ice Shelf.

An ice stream is a region of fast-moving ice within an ice sheet.

Laurentide Ice Sheet

The Barnes Ice Cap, containing remnants of the Laurentide Ice Sheet.

The Laurentide Ice Sheet was a massive sheet of ice that covered millions of square miles, including most of Canada and a large portion of the Northern United States, multiple times during the Quaternary glacial epochs, from 2.58 million years ago to the present.

Last Glacial Maximum

A map of sea surface temperature changes and glacial extent during the last glacial maximum according to Climate: Long range Investigation, Mapping, and Prediction.
Temperature proxies for the last 40,000 years.
A map of vegetation patterns during the last glacial maximum.

The Last Glacial Maximum (LGM), also referred to as the Late Glacial Maximum, was the most recent time during the Last Glacial Period that ice sheets were at their greatest extent.

Greenland ice sheet

Vast body of ice covering 1710000 km², roughly near 80% of the surface of Greenland.

Greenland ice sheet
Melting ice during July 2012, images created by NASA show the process in the summer
Arctic Temperature Trend 1981–2007
Glaciologist at work
The cold blob visible on NASA's global mean temperatures for 2015, the warmest year on record up to 2015 (since 1880) – Colors indicate temperature evolution (NASA/NOAA; 20 January 2016).
In August 2020 scientists reported that melting of the Greenland ice sheet is shown to have passed the point of no return, based on 40 years of satellite data. The switch to a dynamic state of sustained mass loss resulted from widespread retreat in 2000–2005.
In August 2020 scientists reported that the Greenland ice sheet lost a record amount of ice during 2019.
Meltwater creates rivers caused by cryoconite on July 21, 2012
Meltwater rivers may flow down into moulins
Until 2007, rate of decrease in ice sheet height in cm per year.
Modelling results of the sea-level rise under different warming scenarios.
Satellite image of dark melt ponds.
Albedo change in Greenland

The ice sheet is almost 2900 km long in a north–south direction, and its greatest width is 1100 km at a latitude of 77°N, near its northern margin.

West Antarctic Ice Sheet

Segment of the continental ice sheet that covers West Antarctica, the portion of Antarctica on the side of the Transantarctic Mountains that lies in the Western Hemisphere.

A map of West Antarctica
A topographic and bathymetric map of Antarctica without its ice sheets, assuming constant sea levels and no post-glacial rebound
grounding zone

The WAIS is classified as a marine-based ice sheet, meaning that its bed lies well below sea level and its edges flow into floating ice shelves.

Patagonian Ice Sheet

Map showing the extent of the Patagonian Ice Sheet in the Strait of Magellan area during the last glacial period. Selected modern settlements are shown with yellow dots. Sea level was much lower than shown here.
During the last ice age the Patagonian Ice Sheet created the elongated and forested drumlins seen south of Puerto Williams, Chile.

The Patagonian Ice Sheet was a large elongated and narrow ice sheet centered in the southern Andes that existed during the Llanquihue glaciation.

Sea level

Average surface level of one or more among Earth's coastal bodies of water from which heights such as elevation may be measured.

This marker indicating sea level is situated between Jerusalem and the Dead Sea.
Sea level measurements from 23 long tide gauge records in geologically stable environments show a rise of around 200 mm during the 20th century (2 mm/year).
Sea level sign seen on cliff (circled in red) at Badwater Basin, Death Valley National Park
Water cycles between ocean, atmosphere and glaciers
Global sea level during the Last Glacial Period
Melting glaciers are causing a change in sea level

Some land movements occur because of isostatic adjustment of the mantle to the melting of ice sheets at the end of the last ice age.