Extreme glacier melt rarely seen before
16 January 2013, by Harriet Jarlett
New research has shown that the rapid melting of glaciers seen in Antarctica over the last 11 years is not part of a glaciers natural growth and retreat cycle.
Emperor Penguins on the Brunt Ice Shelf
The sheet of ice covering Antarctica is itself covered by layers of snow and ice, which build up and are incorporated into glaciers that flow towards the sea.
The research showed that two of these major glaciers, the Pine Island and Thwaites glaciers, have retreated as much as 15 and a half miles from where they were in 1992. This significant withdrawal is not something that has been recorded regularly in the past ten thousand years.
'It's possible that the grounding lines may retreat even further inland over coming decades,' says lead-author Dr Claus-Dieter Hillenbrand from the British Antarctic Survey (BAS): 'Our study has revealed that episodes of fast glacier retreat similar to that observed over recent decades can only have occurred very rarely during the previous 10,000 years.'
Hillenbrand and colleagues used a gravity corer – named for the gravity which carries it through water to the seafloor – to collect mud from the seabed surrounding the Antarctic Ice Sheet – the huge sheet of ice covering the Antarctic continent. These samples contained thousands of microscopic fossilised creatures whose skeletons are rich in calcium carbonate, a mineral which makes them ideal for dating using radioactivity.
'Such 'calcareous' microfossils are critical for using the radiocarbon technique to determine the age of the sediments, but they are normally extremely rare on the Antarctic continental shelf,' says co-author Dr Gerhard Kuhn. The scientists then constructed a timeline for ice loss in West Antarctica.
This timeline is crucial for improving the accuracy of computer models that are used to predict the future for the melting ice sheet, and the possible impact this could have on raising sea levels.
Hillenbrand C-D, Kuhn G, Smith JA, Gohl K, Graham AGC, Larter RD, Klages JP, Downey R, Moreton SG, Forwick M, Vaughan DG. (2013) Grounding-line retreat of the West Antarctic Ice Sheet from inner Pine Island Bay, Geology v. 41, p. 35-38
Sea level change,
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