It is widely acknowledged that polar sea ice plays a critical role in global climate change. As such, sea ice reconstructions are of paramount importance in establishing climatic evolution of the geological past. In the current project, some well characterised organic chemicals (biomarkers) from microalgae will be used as proxy indicators of current and past sea ice in the Arctic and Antarctic regions. These biomarkers, so-called highly branched isoprenoids (HBIs), possess a number of characteristics that make them attractive as sea ice proxies. Firstly, some HBIs are unique to sea ice diatoms, so their presence in polar sediments can be directly correlated with the previous occurrence of sea ice. Secondly, they are relatively resistant to degradation, which extends their usefulness in the geological record. Thirdly, their relative abundance makes them straightforward to measure with a high degree of geological resolution. One component of this project will consist of performing regional calibrations of the proxies. Concentrations of selected biomarkers in recent Arctic and Antarctic sediments will be correlated with the sea ice abundances determined using satellite technology over the last 30 years. The successful calibration of the proxies will then enable reconstructions of past sea ice extents to be performed at unprecedented high resolution. Sediment cores will be obtained from key locations across both of the Arctic and Antarctic regions and the data derived from these studies will be used for climate modelling studies. As a complement to these physico-chemical studies on sea ice, a second component of the project will investigate the use of these biomarkers for studying sea ice-biota interactions and, by examining the transfer of these chemicals through food chains, new tools for determining the consequences of future climate change on polar ecosystems will be established.
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