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British Antarctic Survey research supported by HMS Endurance. Workperiod 1, 2006.
A joint team of BAS and University of Durham scientists joined HMS Endurance in October to carry out research in the South Shetland Islands and the Antarctic Peninsula. They are researching climate change and its impact on global sea level.
In order to understand climate change and make realistic predictions, both scientists and Governments need to understand how the climate has changed in the past. This is for two reasons. Firstly the models used by climate scientists to predict future change need to be ‘tested’ against past data to make sure that they can correctly simulate climate changes. Secondly, a record of past changes in climate is needed in order to understand the long-term context of climate change caused by human activities. In other words, we need to know the longer-term trends in order to correctly interpret the origin of the recent (short-term) changes.
To answer these questions the scientists are examining the historical record of past climate and sea level changes. The BAS team are sampling the record of past change in a variety of ways including analysis of cores of sediment retrieved from the bottom of lakes, and digging into raised beaches: features that mark former levels of the sea but which have now been uplifted. They are also studying the geomorphological features left by the ice sheet which until about 12000 years ago buried the land and lakes of the Antarctic Peninsula and South Shetland Islands under 1 km of ice.
Extracting a sediment core from beneath the ice of a frozen Antarctic lake
The sediment from the bottom of the lakes is partly composed of the remains of plants and animals that lived in the lakes. As climate has changed then the assemblage of organisms living in the lake (and falling into the mud when they die) has also changed, allowing the scientists to obtain a continuous record of climate variability. In Antarctica such sediment records can be extremely challenging to obtain and the BAS team are using a variety of methods to obtain appropriate samples, depending on the lake. For those lakes which are still frozen over they are able to drill through the lake ice and drive sediment corers into the lake floor. In other lakes, where the ice cover has melted they are using a pre-fabricated raft and small boats as a platform for their coring work. All this is carried-out, of course, whilst maximising the safety of the team using heavy equipment on ice and water, as well as working through all but the worst of the Antarctic weather conditions.
In a similar way to lakes recording climate change, the raised beaches record past changes in sea level. Unravelling this record is tricky because the sea level can change not only by addition or subtraction of water from the oceans, but also the land itself can rise or sink depending on how onshore ice caps are behaving. Increases in the amount of ice can push the crust down, causing an apparent rise in sea level, or decreases in ice mass can allow the land to ‘rebound’ leading to a fall in sea level. The raised beaches studied by the team mostly date from the period following the last ice age, during which time the ice caps have retreated, leaving numerous raised beaches ‘high and dry’, up to 20 m above present sea level.
Collectively, these data will enable the BAS scientists to understand the past interactions between climate, ice sheets and sea level which will be used to test the complex computer models that predict the most likely pattern of future climate and sea level changes.
HMS Endurance Lynx helicopter deploying BAS scientists at a lake in the South Shetland Islands
HMS Endurance is critical to the success of this work as its helicopters provide access to many remote regions and the capability to lift the heavy equipment required by the scientists. The BAS team have been able to use the logistic capabilities of the ship and helicopters to place field camps in several locations across a wide area of the South Shetlands and northern Antarctic Peninsula. The work will continue through most of the Antarctic summer, with HMS Endurance collecting the last field teams and returning them to the Falkland Islands in late January.
To find out more about this research contact Dominic Hodgson (daho@bas.ac.uk) or Mike Bentley (m.j.Bentley@durham.ac.uk) or visit the BAS website: www.antarctica.ac.uk.
The BAS team:
Dominic Hodgson
Mike Bentley
Steve Roberts
Peter Fretwell
Emma Watcham
Bruce Maltmann
Liz Homer
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