Late winter biogeochemical conditions under sea ice in the

With the Arctic summer sea-ice extent in decline, questions are arising as to how changes in sea-ice dynamics might affect biogeochemical cycling and phenomena such as carbon dioxide (CO2) uptake and ocean acidification. Recent field research in these areas has concentrated on biogeochemical and CO2 measurements during spring, summer or autumn, but there are few data for the winter or winterspring transition, particularly in the High Arctic. Here, we present carbon and nutrient data within and under sea ice measured during the Catlin Arctic Survey, over 40 days in March and April 2010, off Ellef Ringnes Island (788 43.11? N, 1048 47.44? W) in the Canadian High Arctic. Results show relatively low surface water (1� 10 m) nitrate ( B1.3 mM) and total inorganic carbon concentrations (mean9SD � 201595.83 mmol kg � 1 ), total alkalinity (mean9SD� 2134911.09 mmol kg � 1 ) and under-ice pCO2sw (mean9SD� 286917 matm). These surprisingly low wintertime carbon and nutrient conditions suggest that the outer Canadian Arctic Archipelago region is nitrate-limited on account of sluggish mixing among the multi-year ice regions of the High Arctic, which could temper the potential of widespread under-ice and open-water phytoplankton blooms later in the season.