Ocean freshwater fluxes through the Canadian archipelago (CAT)

The objectives of the CAT study are to acquire the first complete observations of Canadian Arctic through-flow, to understand why it occurs and to predict how it may change as climate changes. The study is based long-term observations of ocean current and ice drift which can only be acquired in remote Arctic areas by submerged autonomous instruments. During expeditions on several icebreakers in August 2007, such instruments were moored within the three principal gateways for flow between the Arctic Ocean and Baffin Bay, Nares Strait, Cardigan Strait and Lancaster Sound. The instruments were programmed to measure current, temperature, salinity, ice thickness, ice drift and sea level and recorded data internally because transmission from the sub-sea world to the outside is not possible. Two years¿ data were acquired from Lancaster Sound via two one-year deployments with recoveries in August 2008 and 2009. Two years¿ data were acquired from Nares and Cardigan Straits via a single two-year deployment with recovery in August 2009. When moorings are being serviced from CCG ships, seawater was sampled across the channel sections for later geochemical tracer analysis. Trace chemicals in seawater can reveal the separate contributions to ocean freshwater of melt-water, runoff and Pacific through-flow. The CAT study includes a theoretical component. Physically-based computer models used the new data to develop and test our understanding of through-flow, of its variability and of its impacts on the climate, productivity and fisheries of downstream basins in Baffin Bay and the Labrador Sea. The CAT project was coordinated within the international Arctic Sub-Arctic Ocean Fluxes study. ASOF has striven for simultaneous decade-long observation of all inflows to and outflows from the Arctic Ocean (Bering Strait to Barents Sea) and also those to and from the Labrador and Nordic Seas, where the impacts on the global thermohaline circulation are likely to occur.