Improving future predictions of Arctic sea ice and impact of a changing Arctic on the ocean, atmosphere and ecosystem

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Global Climate Models (GCMs) participating in the Intergovernmental Panel on Climate Change - fourth and fifth Assessment Report (IPCC-AR4/5) show that transition to a summertime ice-free Arcticcould occur both abruptly and earlier than previously anticipated. The fact that all AR5 models still underestimate the decline in sea-ice extent as compared to the satellite record (1979-2006) suggests,however, that something in our understanding of the Arctic climate system is lacking. The overall objective of the work is to 1- improve the forecast of future sea ice conditions in the Arctic Ocean and its peripheral Seas, 2- identify/study oceanic, sea ice and atmospheric processes responsible for the sea ice decline, and 3- study the impact of such changes on atmospheric circulation patterns and wildlife that depends on the sea ice for their livelihood. The specific objective of the work is to quantify small scale processes in GCMs that are important in the sea ice mass balance. In this proposal we place special emphasis on the sea ice (lead representation), vertical ocean heat fluxes (through both advection and turbulent mixing), and atmospheric boundary layer processes (i.e. (mis)representation of the surface inversion in GCMs and its impact on clouds and the surfaceradiative balance). The impact of Arctic climate change will focus primarily on the effect of retreating sea ice on storm tracks and precipitation patterns, and the geographical changes and timing ofchanges in habitat for ice-dependent species. The completion of this work will lead to 1- better constraints on projection of future Arctic climate change, 2- a better understanding of small scales oceanic and atmospheric boundary layer processes having a strong impact on the sea ice mass balance, and 3- still more efficient numerical solver for the sea-ice models that are being implemented in Global Climate Models and operational forecasts models from Environment Canada. This research program will place Canada in a unique position to better assess the changing Arctic and how it can affect local marine ecosystem, economic development of the Canadian Arctic, and local Inuit population, whose lifestyle is intimately linked with the presence of ice.