Ice sheets

Glacier calving

Data from tide gauges and satellite altimeters suggest that in the 1990s–2000s global sea level rose at a rate of 3 mm/yr, which is higher than projected by the Intergovernmental Panel on Climate Change, though the rate has since slowed to 2.5 mm/yr.

An obvious source for this extra water is from the melting of ice sheets and glaciers overlying land. The ice sheets that blanket Antarctica and Greenland are several kilometres thick, and it is the melting of these massive ice masses that have the potential to cause a significant rise in global sea level.

Before 2000, indications were that Earth’s two major ice caps, covering Antarctica and Greenland, were generally stable, at least in their interiors. However, it is now known that the ice caps are melting at their base, caused by warming oceans. It has been discovered that a large glacial basin at the coastal boundary of West Antarctica – the Pine Island Glacier – is thinning at a rate of 16 m per year, acting as a huge drainage basin. Satellites also continue to observe the break up of the Wilkins Ice Shelf on the southwest side of the Antarctic Peninsula. In April 2009, rifts that had developed on the ice shelf led to the collapse of the ice bridge that connected it to Charcot Island.

Pine Island Glacier
Pine Island Glacier

New information about changes in continental ice cover has led to a projection of sea-level rise in the order of 1.4 m by 2100. This figure, cited in the 2009 report by the Scientific Committee on Antarctic Research Antarctic Climate Change and the Environmentt, is significantly higher than the 28–43 cm projections by the Fourth Assessment Report of the Intergovernmental Panel on Climate Change in 2007.

The improvement in resolution of the CryoSat radar over that of its pulse-limited predecessors, couples with its interferometric capability, will make spatially and temporally continuous measurements of the ice-sheet margins and smaller ice masses possible for the first time. Observations from CryoSat will therefore lead to a much better understanding of how these massive ice sheets are responding to a changing climate.

Last update: 22 January 2010

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