An ice-free Arctic: oceanic and atmospheric mechanism

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The year 2005 marked a record low in summer sea-ice extent in the Arctic.  This is the 4th record low in a row, and caps a nearly 3-decade downward trend, since satellites made synoptic ice imaging possible in 1979. There is serious speculation in the Arctic climate research community that we, or possibly our children, will see an ice-free Arctic as a regular summer feature. The main goal of the proposed work is to clarify the role of the ocean and the atmosphere in shaping an ice-free Arctic. The project will also improve our interpretation of the current generation climate predictions based on General Circulation Models (GCMs). First, the fresh water and heat exchange between the Arctic Ocean and the northern North Atlantic will be investigated. Our goal here is: (1) to quantify the contribution of the surface ocean currents and the sea ice to the year-to-year variability in fresh water transport from the Arctic into the Greenland and Labrador seas, (2) to better understand the link between this fresh water transport and atmospheric forcing, especially atmospheric modes of variability such as the North Atlantic Oscillation (NAO), (3) to quantify the role of buoyancy fluxes and mechanical forcing (from winds) in driving spatial changes to the mixed layer depth which are linked to fresh water export, and (4) to evaluate the ability of current GCMs to simulate features that are believed to be of fundamental importance to climate variability and change in the high latitudes. To this end, the UVic-ESCM coupled ice-ocean model will be used for control and perturbation runs.  Its output, along with other IPCC-2005 runs will be compared with temperature, salinity, and tracer observations (principally O18, C-14, He-Tr, CFCs).