Ice sheet

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An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² (20,000 mile²). 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 Canada and North America, the Weichselian ice sheet covered northern Europe and the Patagonian Ice Sheet covered southern South America.

Ice sheets are bigger than ice shelves or glaciers. Masses of ice covering less than 50,000 km2 are termed an ice cap. An ice cap will typically feed a series of glaciers around its periphery.

Although the surface is cold, the base of an ice sheet is generally warmer due to geothermal heat. In places, melting occurs and the melt-water lubricates the ice sheet so that it flows more rapidly. This process produces fast-flowing channels in the ice sheet — these are ice streams.

The present-day polar ice sheets are relatively young in geological terms. The Antarctic Ice Sheet first formed as a small ice cap (maybe several) in the early Oligocene, but retreating and advancing many times until the Pliocene, when it came to occupy almost all of Antarctica. The Greenland ice sheet did not develop at all until the late Pliocene, but apparently developed very rapidly with the first continental glaciation. This had the unusual effect of allowing fossils of plants that once grew on present-day Greenland to be much better preserved than with the slowly forming Antarctic ice sheet.

For more information about Ice sheet, read the full article at Wikipedia.
This text uses material from Wikipedia and is available under the GNU Free Documentation License.

News tagged with ice sheet

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Catastrophic sea levels 'distinct possibility' this century: study

Space & Earth / Earth Sciences

Apr 15, 2009 | 4.4 / 5 (90) | 25

A breakthrough study of fluctuations in sea levels the last time Earth was between ice ages, as it is now, shows that oceans rose some three meters in only decades due to collapsing ice sheets.

Ice Sheets Can Retreat 'In a Geologic Instant,' Study of Prehistoric Glacier Shows

Space & Earth / Earth Sciences

Jun 21, 2009 | 4.5 / 5 (61) | 20

(PhysOrg.com) -- Modern glaciers, such as those making up the Greenland and Antarctic ice sheets, are capable of undergoing periods of rapid shrinkage or retreat, according to new findings by paleoclimatologists ...

Greenland ice sheet larger contributor to sea-level rise

Space & Earth / Earth Sciences

Jun 12, 2009 | 4.4 / 5 (52) | 8

The Greenland ice sheet is melting faster than expected according to a new study led by a University of Alaska Fairbanks researcher and published in the journal Hydrological Processes.

Ice Age lesson predicts a faster rise in sea level

Space & Earth / Earth Sciences

Aug 31, 2008 | 4.2 / 5 (51) | 27

If the lessons being learned by scientists about the demise of the last great North American ice sheet are correct, estimates of global sea level rise from a melting Greenland ice sheet may be seriously underestimated.

Sea level rise could be worse than anticipated

Space & Earth / Earth Sciences

Feb 05, 2009 | 3.3 / 5 (49) | 37

If global warming some day causes the West Antarctic Ice Sheet to collapse, as many experts believe it could, the resulting sea level rise in much of the United States and other parts of the world would be ...

Small glaciers -- not large -- account for most of Greenland's recent loss of ice, study shows

Space & Earth / Earth Sciences

Sep 15, 2008 | 4.3 / 5 (32) | 6

(PhysOrg.com) -- The recent dramatic melting and breakup of a few huge Greenland glaciers have fueled public concerns over the impact of global climate change, but that isn't the island's biggest problem.

Previously Unknown Volcanic Eruption Helped Trigger Cold Decade

Space & Earth / Earth Sciences

Oct 29, 2009 | 4.3 / 5 (27) | 9

(PhysOrg.com) -- A team of chemists from the U.S. and France has found compelling evidence of a previously undocumented large volcanic eruption that occurred exactly 200 years ago, in 1809.

Greenland ice cap melting faster than ever

Space & Earth / Earth Sciences

Nov 12, 2009 | 3.6 / 5 (32) | 25

Satellite observations and a state-of-the art regional atmospheric model have independently confirmed that the Greenland ice sheet is loosing mass at an accelerating rate, reports a new study in Science.

New data show much of Antarctica is warming more than previously thought

Space & Earth / Environment

Jan 21, 2009 | 3 / 5 (36) | 31

(PhysOrg.com) -- Scientists studying climate change have long believed that while most of the rest of the globe has been getting steadily warmer, a large part of Antarctica - the East Antarctic Ice Sheet - ...

Long debate ended over cause, demise of ice ages -- may also help predict future

Space & Earth / Earth Sciences

Aug 06, 2009 | 4.4 / 5 (23) | 63

Researchers have largely put to rest a long debate on the underlying mechanism that has caused periodic ice ages on Earth for the past 2.5 million years - they are ultimately linked to slight shifts in solar radiation caused ...

Melting of the Greenland ice sheet mapped

Space & Earth / Earth Sciences

Sep 16, 2009 | 3.9 / 5 (18) | 0

Will all of the ice on Greenland melt and flow out into the sea, bringing about a colossal rise in ocean levels on Earth, as the global temperature rises? The key concern is how stable the ice cap actually ...

West Antarctic ice comes and goes, rapidly

Space & Earth / Earth Sciences

Mar 18, 2009 | 4.3 / 5 (16) | 8

Researchers today worry about the collapse of West Antarctic ice shelves and loss of the West Antarctic ice sheet, but little is known about the past movements of this ice. Now climatologists from Penn State ...

Scientists probe Antarctic glaciers for clues to past and future sea level

Space & Earth / Earth Sciences

Oct 28, 2008 | 3.6 / 5 (18) | 1

Scientists from the U.S., U.K. and Australia have teamed up to explore two of the last uncharted regions of Earth, the Aurora and Wilkes Subglacial Basins, immense ice-buried lowlands in Antarctica with a combined area the ...

New CO2 data helps unlock the secrets of Antarctic formation

Space & Earth / Earth Sciences

Sep 13, 2009 | 4.1 / 5 (15) | 6

The link between declining CO₂ levels in the earth's atmosphere and the formation of the Antarctic ice caps some 34 million years ago has been confirmed for the first time in a major research study.