Editing Ice sheet (section)

{{Short description|Large mass of glacial ice}}
{{Redirect|Continental glacier|the glacier located in Wyoming|Continental Glacier}}

[[File:Antarctica 6400px from Blue Marble.jpg|thumb|upright=1.3|One of Earth's two ice sheets: The [[Antarctic ice sheet]] covers about 98% of the [[Antarctica|Antarctic]] [[continent]] and is the largest single mass of [[ice]] on Earth. It has an average thickness of over 2&nbsp;kilometers.<ref name="NSFfactsheet">{{Cite web |title=Ice Sheets |url=https://www.nsf.gov/geo/opp/antarct/science/icesheet.jsp |publisher=National Science Foundation}}</ref>]]

In [[glaciology]], an '''ice sheet''', also known as a '''continental glacier''',<ref>[http://amsglossary.allenpress.com/glossary/search?id=ice-sheet1 American Meteorological Society, Glossary of Meteorology] {{webarchive|url=https://web.archive.org/web/20120623093132/http://amsglossary.allenpress.com/glossary/search?id=ice-sheet1 |date=2012-06-23 }}</ref> is a mass of [[glacier|glacial]] [[ice]] that covers surrounding terrain and is greater than {{convert|50000|km2|sqmi|abbr=on|lk=off}}.<ref>{{cite web|url=http://gemini.oscs.montana.edu/~geol445/hyperglac/glossary.htm|access-date=2006-08-22|title=Glossary of Important Terms in Glacial Geology|url-status=dead|archive-url=https://web.archive.org/web/20060829001754/http://gemini.oscs.montana.edu/~geol445/hyperglac/glossary.htm|archive-date=2006-08-29}}</ref> The only current ice sheets are the [[Antarctic ice sheet]] and the [[Greenland ice sheet]]. Ice sheets are bigger than [[ice shelf|ice shelves]] or alpine [[glacier]]s. Masses of ice covering less than 50,000&nbsp;km<sup>2</sup> 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 activity|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&nbsp;— these are [[ice stream]]s.

Even stable ice sheets are continually in motion as the ice gradually flows outward from the central plateau, which is the tallest point of the ice sheet, and towards the margins. The ice sheet slope is low around the plateau but increases steeply at the margins.<ref name="IPCC_AR6_AnnexVII" />

Increasing global air temperatures due to climate change take around 10,000 years to directly propagate through the ice before they influence bed temperatures, but may have an effect through increased surface melting, producing more [[supraglacial lake]]s. These lakes may feed warm water to glacial bases and facilitate glacial motion.<ref name="IPCCc4" />

In previous geologic time spans ([[glacial period]]s) there were other ice sheets. During the [[Last Glacial Period]] at [[Last Glacial Maximum]], the [[Laurentide Ice Sheet]] covered much of [[North America]]. In the same period, the [[Weichselian]] ice sheet covered [[Northern Europe]] and the [[Patagonian Ice Sheet]] covered southern [[South America]].