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[1] Enhanced resolution Advanced Microwave Scanning Radiometer (AMSR-E) imagery is used to estimate daily sea ice area fluxes between the Canadian Arctic Archipelago and the Arctic Ocean and Baffin Bay for the period September 2002 to June 2007. Over the period, Amundsen Gulf and M'Clure Strait exported 54 Â 10 3 km 2 of sea ice area or roughly 77 km 3 of sea ice volume each year into the Arctic Ocean. Export/import into the Arctic Ocean through the Queen Elizabeth Islands is small and uncertain since no estimates for July and August could be made due to atmospheric attenuation of the microwave signal. Lancaster Sound exported 68 Â 10 3 km 2 of sea ice area or roughly 102 km 3 of ice volume into Baffin Bay. This produced a net loss of sea ice area of about 122 Â 10 3 km 2 or roughly 174 km 3 a À1 which is presumed to be generated from within the Archipelago itself mainly through the stationary and transient polynyas and leads that form each winter. Daily ice area fluxes for Amundsen Gulf (AG) and Lancaster Sound (LS) were as high as ±2500 km 2 d À1 and were event driven depending on synoptic scale atmospheric circulation and the mobility of the sea ice. Mean sea level pressure difference across each gate is moderately correlated with daily sea ice area fluxes despite the fact that free ice drift conditions are not always met in the region. Cross-gradient and daily sea ice area flux for Lancaster Sound show a large number of counter gradient ice flux occurrences suggesting that local mesoscale winds (nongeostrophic) and perhaps ocean currents play a role in transporting sea ice through this gate. Monthly ice fluxes for the AG and MS gate were positively correlated with the AO index indicating that a strong Beaufort Sea high pressure and gyre correspond to more export into the Beaufort Sea. Monthly fluxes for the LS gate were positively correlated with the NAO index indicating that strong southerly atmospheric circulation over Baffin Bay increases ice export into Baffin Bay from Lancaster Sound.

Abstract. During summer 1998, record reductions in ice cover occurred in the Beaufort and Chukchi seas. Open water formed earlier than in prior years, and September ice extent in this region was 25 percent less than the previous minimum for 1953-1997. Seven percent of the Arctic Basin that had been perennially ice covered was ice-free in 1998. This reduction in western Arctic ice extent can be attributed in part to preconditioning by light-ice cover in autumn 1997 and to atmospheric circulation patterns during the following winter through autumn that favored southerly and easterly winds. Such decreases in northerly winds, and the associated weakening or displacement of the Beaufort Gyre, is found to be typical of winters that precede years with below-normal ice extent in the western Arctic.

Human influence has previously been identified in the observed loss of Arctic sea ice, but this hypothesis has not yet been tested with a formal optimal detection approach. By comparing observed and multi‐model simulated changes in Arctic sea ice extent during 1953–2006 using an optimal fingerprinting method, we find that the anthropogenic signal first emerged in the early 1990s, indicating that human influence could have been detected even prior to the recent dramatic sea ice decline. The anthropogenic signal is also detectable for individual months from May to December, suggesting that human influence, strongest in late summer, now also extends into colder seasons.