Ice shelf

[1] That flow continually moves ice from the grounding line to the seaward front of the shelf.

In the last several decades, glaciologists have observed consistent decreases in ice shelf extent through melt, calving, and complete disintegration of some shelves.

These shelves serve another important purpose—"they moderate the amount of melting that occurs on the glaciers' surfaces.

[8][9] The height of the shelf above the sea can be even larger, if there is much less dense firn and snow above the glacier ice.

[13]: 2234 In steady state, about half of Antarctica's ice shelf mass is lost to basal melt and half is lost to calving, but the relative importance of each process varies significantly between ice shelves.

The nearly vertical ice front to the open sea is more than 600 kilometres (370 mi) long, and between 15 and 50 metres (50 and 160 ft) high above the water surface.

All Canadian ice shelves are attached to Ellesmere Island and lie north of 82°N.

[21] In the last several decades, glaciologists have observed consistent decreases in ice shelf extent through melt, calving, and complete disintegration of some shelves.

Removal of the shelf has the potential to increase the contribution of Thwaites glacier to sea level rise by up to 25%.

[28] A sequence of Sentinel-1 radar imagery shows that parallel wing and comb cracks have recently formed rifts at high angles to the main shear margin and are propagating into the central part of the ice shelf at rates as high as 2 km per year.

Satellite data, ground-penetrating radar, and GPS measurements taken in 2021 indicate that collapse of the ice shelf may be initiated by intersection of rifts with hidden basal crevasse zones as soon as 2026.

[34] From 31 January 2002 to March 2002 the Larsen B sector partially collapsed and parts broke up, 3,250 km2 (1,250 sq mi) of ice 220 m (720 ft) thick, an area comparable to the US state of Rhode Island.

[37] In 2015, a study concluded that the remaining Larsen B ice-shelf would disintegrate by 2020, based on observations of faster flow and rapid thinning of glaciers in the area.

[39] By contrast, Larsen A was absent for a significant part of that period, reforming about 4,000 years ago.

[40] It broke over a period of three weeks or less, with a factor in this fast break-up being the powerful effects of water; ponds of meltwater formed on the surface during the near 24 hours of daylight in the summertime, flowed down into cracks and, acting like a multitude of wedges, levered the shelf apart.

A large group of small icebergs (the largest some 1000 metres in length), were seen off the south-east coast of the island, with one of them drifting close enough to shore to be visible from the hills above the city of Dunedin.

[58] In the summer of 2002, the Ward Ice Shelf experienced another major breakup,[59] and other instances of note happened in 2008 and 2010 as well.

[60] The last remnant to remain mostly intact, the Milne Ice Shelf, also ultimately experienced a major breakup at the end of July 2020, losing over 40% of its area.

[62] During the twentieth century, the Ellesmere Ice Shelf broke up into six separate shelves.

In April 2000, satellite images revealed that a large crack in the Ward Hunt shelf had begun to form, and in 2003 it was announced that the ice sheet had split completely in two in 2002, releasing a huge pool of freshwater from the largest epishelf lake in the Northern Hemisphere, located in Disraeli Fjord.

[65] In April 2008, scientists discovered that the shelf fractured into dozens of deep, multi-faceted cracks.