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[1] The effects of changing ice and atmospheric conditions on the upwelling of deep nutrient-laden waters and biological productivity in the coastal Beaufort Sea were quantified using a unique combination of in situ and remote-sensing approaches. Repeated instances of ice ablation and upwelling during fall 2007 and summer 2008 multiplied the production of ice algae, phytoplankton, zooplankton and benthos by 2 to 6 fold. Strong wind forcing failed to induce upward shifts in the biological productivity of stratified waters off the shelf.

[1] The Arctic summer minimum sea ice extent has experienced a decreasing trend since 1979, with an extreme minimum extent of 4.27 Â 10 6 km 2 in September 2007, and a similar minimum in 2011. Large expanses of open water in the Siberian, Laptev, Chukchi, and Beaufort Seas result from declining summer sea ice cover, and consequently introduce long fetch within the Arctic Basin. Strong winds from migratory cyclones coupled with increasing fetch generate large waves which can propagate into the pack ice and break it up. On 06 September 2009, we observed the intrusion of large swells into the multiyear pack ice approximately 250 km from the ice edge. These large swells induced nearly instantaneous widespread fracturing of the multiyear pack ice, reducing the large, (>1 km diameter) parent ice floes to small (100-150 m diameter) floes. This process increased the total ice floe perimeter exposed to the open ocean, allowing for more efficient distribution of energy from ocean heat fluxes, and incoming radiation into the floes, thereby enhancing lateral melting. This process of sea ice decay is therefore presented as a potential positive feedback process that will accelerate the loss of Arctic sea ice.

The Circumpolar Flaw Lead (CFL) system study is a Canadian-led International Polar Year (IPY) initiative with over 350 participants from 27 countries. The study is multidisciplinary in nature, integrating physical sciences, biological sciences and Inuvialuit traditional knowledge. The CFL study is designed to investigate the importance of changing climate processes in the flaw lead system of the northern hemisphere on the physical, biogeochemical and biological components of the Arctic marine system. The circumpolar flaw lead is a perennial characteristic of the Arctic throughout the winter season and forms when the mobile multi-year (MY) pack ice moves away from coastal fast ice, creating recurrent and interconnected polynyas in the Norwegian, Icelandic, North American and Siberian sectors of the Arctic. The CFL study was 293 days in duration and involved the overwintering of the Canadian research icebreaker CCGS Amundsen in the Cape Bathurst flaw lead throughout the annual sea-ice cycle of 2007-2008. In this paper we provide an introduction to the CFL project and then use preliminary data from the field season to describe the physical flaw lead system, as observed during the CFL overwintering project. Preliminary data show that ocean circulation is affected by eddy propagation into Amundsen Gulf (AG). Upwelling features arising along the ice edge and along abrupt topography are also detected and identified as important processes that bring nutrient rich waters up to the euphotic zone. Analysis of sea-ice relative vorticity and sea-ice area by ice type in the AG during the CFL study illustrates increased variability in ice vorticity in late autumn 2007 and an increase in new and young ice areas in the AG during winter. Analysis of atmospheric data show that a strong northeast-southwest pressure gradient present over the AG in autumn may be a synoptic-scale atmospheric response to sensible and latent heat fluxes arising from areas of open water persisting into late November 2007. The median atmospheric boundary layer temperature profile over the Cape Bathurst flaw lead during the winter season was stable but much less so when compared to Russian ice island stations.RéSuMé [Traduit par la rédaction] L'étude du système du chenal de séparation circumpolaire (CSC) est une initiative de l'Année polaire internationale (API) menée par le Canada et à laquelle 350 participants provenant de 27 pays ont pris part. L'étude, de nature multidisciplinaire, fait appel aux sciences physiques et biologiques ainsi qu'au savoir traditionnel Inuvialuit. L'étude du CSC vise à examiner les répercussions des processus climatiques changeants dans le système du chenal de séparation de l'hémisphère Nord sur les composantes physiques, biogéochimiques et biologiques du système marin arctique. Le CSC est une caractéristique permanente de l'Arctique durant la saison d'hiver et se forme quand la banquise mobile de glace de plusieurs années s'éloigne de la banquise côtière fixe en créant des polynies récurrentes et interconnectées dans les sec...

[1] In September 2009 we observed a much different sea icescape in the Southern Beaufort Sea than anticipated, based on remotely sensed products. Radarsat derived ice charts predicted 7 to 9 tenths multi-year (MY) or thick first-year (FY) sea ice throughout most of the Southern Beaufort Sea in the deep water of the Canada Basin. In situ observations found heavily decayed, very small remnant MY and FY floes interspersed with new ice between floes, in melt ponds, thaw holes and growing over negative freeboard older ice. This icescape contained approximately 25% open water, predominantly distributed in between floes or in thaw holes connected to the ocean below. Although this rotten ice regime was quite different that the expected MY regime in terms of ice volume and strength, their near-surface physical properties were found to be sufficiently alike that their radiometric and scattering characteristics were almost identical.

[1] Recent drastic reduction of the older perennial sea ice in the Arctic Ocean has resulted in a vast expansion of younger and saltier seasonal sea ice. This increase in the salinity of the overall ice cover could impact tropospheric chemical processes. Springtime perennial ice extent in 2008 and 2009 broke the half-century record minimum in 2007 by about one million km 2 . In both years seasonal ice was dominant across the Beaufort Sea extending to the Amundsen Gulf, where significant field and satellite observations of sea ice, temperature, and atmospheric chemicals have been made. Measurements at the site of the Canadian Coast Guard Ship Amundsen ice breaker in the Amundsen Gulf showed events of increased bromine monoxide (BrO), coupled with decreases of ozone (O 3 ) and gaseous elemental mercury (GEM), during cold periods in March 2008. The timing of the main event of BrO, O 3 , and GEM changes was found to be consistent with BrO observed by satellites over an extensive area around the site. Furthermore, satellite sensors detected a doubling of atmospheric BrO in a vortex associated with a spiral rising air pattern. In spring 2009, excessive and widespread bromine explosions occurred in the same region while the regional air temperature was low and the extent of perennial ice was significantly reduced compared to the case in 2008. Using satellite observations together with a Rising-Air-Parcel model, we discover a topographic control on BrO distribution such that the Alaskan North Slope and the Canadian Shield region were exposed to elevated BrO, whereas the surrounding mountains isolated the Alaskan interior from bromine intrusion.Citation: Nghiem, S. V., et al. (2012), Field and satellite observations of the formation and distribution of Arctic atmospheric bromine above a rejuvenated sea ice cover,

[1] The Beaufort Gyre (BG) typically rotates anticyclonically and exerts an important control on Arctic Sea ice dynamics. Previous studies have shown reversals in the BG to rotate cyclonically during summer months and, in recent decades, throughout the annual cycle. In this investigation, we explore the synoptic climatology of atmospheric forcing and its relationship to sea ice motion and BG reversals. A catalog of daily synoptic weather types is generated for the Beaufort Sea Region covering the period 1979 to 2006 using NCEP/NCAR reanalysis mean sea level pressure data, principle components, and k-means cluster analyses. Mean synoptic type frequency, persistence, and duration values are calculated for each synoptic type and contrasted between the summer and winter seasons. Daily synoptic types are linked to changes in sea ice vorticity by using correlation analysis on lagged sea ice vorticity data. Lag correlations are found between synoptic types and sea ice vorticity smoothed over a 12-week running mean and show that cyclonic types, which promote southerly or easterly atmospheric circulation over the southern Beaufort Sea, commonly precede summer reversals. Furthermore, significant seasonal within-type variability in sea ice vorticity is detected within the synoptic types illustrating the importance of seasonal variability on these processes.

A time series of microwave radiometric profiles over Arctic Canada's Cape Bathurst (70 • N, 124.5 • W) flaw lead polynya region from 1 January to 30 June, 2008 was examined to determine the general characteristics of the atmospheric boundary layer in winter and spring. A surface based or elevated inversion was present on 97% of winter (JanuaryMarch) days, and on 77% of spring (April-June) days. The inversion was the deepest in the first week of March (≈1100 m), and the shallowest in June (≈250 m). The mean temperature and absolute humidity from the surface to the top of the inversion averaged 250.1 K (−23.1 • C), and 0.56 × 10 −3 kg m −3 in winter, and in spring averaged 267.5 K (−5.6 • C), and 2.77 × 10 −3 kg m −3 . The median winter atmospheric boundary-layer (ABL) potential temperature profile provided evidence of a shallow, weakly stable internal boundary layer (surface to 350 m) topped by an inversion (350-1,000 m). The median spring profile showed a shallow, near-neutral internal boundary layer (surface to 350 m) under an elevated inversion (600-800 m). The median ABL absolute humidity profiles were weakly positive in winter and negative in spring. Estimates of the convergence of sensible heat and water vapour from the surface that could have produced the turbulent internal boundary layers of the median profiles were 0.67 MJ m −2 and 13.1 × 10 −3 kg m −2 for the winter season, and 0.66 MJ m −2 and 33.4 × 10 −3 kg m −2 for the spring season. With fetches of 10-100 km, these accumulations may have resulted from a surface sensible heat flux of 15-185 W m −2 , plus a surface moisture flux of 0.001-0.013 mm h −1 (or a latent heat flux of 0.7-8.8 W m −2 ) in winter, and 0.003-0.033 mm h −1 (or a latent heat flux of 2-22 W m −2 ) in spring.