The role of Arctic sea ice in climatic and ecological processes

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In the last century Arctic sea ice has declined, both in extent and thickness. This trend has accelerated to the point where a summer ice-free Arctic Ocean is expected in the next decades. This represents an unprecedented change in scale and speed of sea ice-melt, unique for at least millennia, and also possibly in the history of human civilisation.The impacts of melting sea-ice are predicted to be wide-ranging, from alterations in the distribution of local terrestrial and marine fauna and flora, to changes to the earth's climate systems and ocean circulatory patterns: large shifts in the distribution of marine fauna and plankton, reductions in the habitat of key species such as the polar bear, or an enhanced Arctic-mid-latitudes climate connection responsible for colder winters in Europe are amongst these impacts. Sea ice is a key part of Arctic climate and ecology. Its white surface acts as a mirror for the incoming solar rays, which are largely reflected back into space, instead of penetrating the ocean and getting trapped in our planet. Sea ice loss increases the amount of heat entering our planet, further accelerating warming. Sea ice melt also creates great volumes of freshwater, interfering with the global oceanic circulation. Arctic sea ice loss thus plays a big role in further warming the Arctic (which warms much faster than lower latitudes). This enhances plant growth, causing large changes in the tundra. Plus, many plants and animals have evolved in landscapes with sea ice that are now changing. The consequences of this for animals such as the polar bear, the Arctic fox, Arctic whales and seals, and Arctic plants remain poorly understood.The anticipated large effects on climate and ecology are to date largely unquantified, due to the fact that Arctic biologists and climatologists are confronted with scarce and short information of past environmental conditions. The compilation of long environmental records for the Arctic would allow testing many questions about the effects of a rapidly changing environment. A much needed long (covering thousands of years) record of sea ice conditions for the whole Arctic is thus lacking.The aim of the proposed project is to produce it to answer key questions with direct implications for our society, namely: how changes in Arctic sea ice affect the global climate and the high latitude biota, and what can we learn from this for the future?Past sea ice conditions are inferred from the analysis of material collected in the Arctic that constitutes evidence of past sea ice presence or absence (sea ice proxies). This material consists of molecules and microscopic organisms in dated sediment at the bottom of the ocean, ice cores and tree rings affected by sea ice, scars made by ice on beaches, and animal and plant remains like whale bones or driftwood. This project proposes a collaborative effort to combine all this information and produce a full Arctic picture of past sea ice dynamics.Of all sea ice proxies, driftwood is the only one informing not only of past sea ice condition, but also of the drift routes sea ice took to deliver driftwood from the moment it entered the ocean to the moment it got deposited on Arctic beaches. Since the Arctic is so cold, driftwood is well preserved for more than 10,000 years. Existing material will be analysed using new techniques that can inform with improved precision about past sea ice extent and drift routes. Arctic expeditions will be organized to collect new material for key regions and periods.This will help the scientific community to answer questions about the role of sea ice in Arctic climate and biology and its global consequences. It will also put current changes in a larger framework and improve our understanding of the effects that this huge environmental change will have on our planet, which is what I find most important and exciting about this research proposal.