BAS and USGS analysed more than 2000 aerial photographs dating from 1940, and over 100 satellite images from the 1960s onwards, to calculate the position of glacier fronts along the coast of the Antarctic Peninsula. These historical records reveal previously unknown patterns of change.
Lead author, Alison Cook said, 'Fifty years ago, 62% most of the glaciers that flowed down from the mountains to the sea we looked at were slowly growing slowly in length but since then this pattern has reversed. In the last 5 years the majority were actually shrinking rapidly. The retreat began at the northern, warmer tip of the Antarctic Peninsula and, broadly speaking, moved southwards as atmospheric temperatures rose. This region has shown dramatic and localised warming - around 2°C in the last 50 years - but this is not the only factor causing the changes. It's a complex picture.'
'On average the glaciers we looked at retreated by 50 m per year in the last five years, faster than at any other time in the last fifty years. However 32 glaciers go against the trend and are showing minor advance. Had we not studied such a large number of glaciers we may have missed the overall pattern. It's the pattern of change from advance to retreat that suggests warming is the key cause, but these glaciers clearly show a more complex response than neighbouring ice shelves.' BAS Glaciologist, Dr David Vaughan is a co-author of the paper. He said, 'These glacier retreat patterns combined with dramatic ice shelf break-ups leave us in no doubt that the Antarctic Peninsula ice sheet is extremely sensitive to recent warming. What we still need to determine is whether or not the warming in this area has its roots in human-influenced global warming. Either way, continuing retreat of glaciers in this area is important because it could allow more ice to drain from further inland and contribute to sea level rise. The current effect may be small in global terms, but this research takes us a step closer to understanding the cause and predicting the future.'
Issued by the British Antarctic Survey Press Office.
Author contacts: Alison Cook +44 (0)1223 221438; David Vaughan +44 (0)1223 643.
NOTES TO EDITORS:
Retreating Glacier Fronts on the Antarctic Peninsula over the Past Half Century, by Alison Cook, Adrian Fox, David Vaughan and Jane Ferrigno is published this week in Science.
Pictures: stills and broadcast-quality footage of the glaciers studied are available from the BAS Press Office.
Three maps showing how the coastlines and how they have changed over time will be published shortly by the USGS.
British Antarctic Survey is a world leader in research into global issues in an Antarctic context. It is the UK's national operator and is a component of the Natural Environment Research Council. It has an annual budget of around £40 million, runs eight research programmes and operates five research stations, two Royal Research Ships and five aircraft in and around Antarctica. More information about the work of the Survey can be found at: www.antarctica.ac.uk.
Ice sheet - is the huge mass of ice, up to 4 km thick, that covers Antarctica's bedrock. It flows from the centre of the continent towards the coast where it feeds ice shelves. The ice sheets can flow uphill and over mountain ranges of significant size.
Ice shelf - is the floating extension of the grounded ice sheet. It is composed of freshwater ice that originally fell as snow, either in situ or inland and brought to the ice shelf by glaciers. As they are already floating any disintegration (like Larsen B) will have no impact on sea level. Sea level will rise only if the ice held back by the ice shelf flows more quickly onto the sea.
A glacier - is a 'river of ice', usually flowing between mountains that formed on bedrock by the compaction and recrystallization of snow.