Source identification and distribution reveals the potential of the geochemical Antarctic sea ice proxy IPSO25

The presence of a di-unsaturated highly branched isoprenoid (HBI) lipid biomarker (diene II) in Southern Ocean sediments has previously been proposed as a proxy measure of palaeo Antarctic sea ice. Here we show that a source of diene II is the sympagic diatom Berkeleya adeliensis Medlin. Furthermore, the propensity for B. adeliensis to flourish in platelet ice is reflected by an offshore downward gradient in diene II concentration in >100 surface sediments from Antarctic coastal and near-coastal environments. Since platelet ice formation is strongly associated with super-cooled freshwater inflow, we further hypothesize that sedimentary diene II provides a potentially sensitive proxy indicator of landfast sea ice influenced by meltwater discharge from nearby glaciers and ice shelves, and re-examination of some previous diene II downcore records supports this hypothesis. The term IPSO25-Ice Proxy for the Southern Ocean with 25 carbon atoms-is proposed as a proxy name for diene II

A922 Sequential measurement of 1 hour creatinine clearance (1-CRCL) in critically ill patients at risk of acute kidney injury (AKI)

Meeting abstrac

Carbon Fluxes Across Boundaries in the Pacific Arctic Region in a Changing Environment

While the inflow of dissolved inorganic carbon (DIC) from the Pacific Ocean is relatively well quantified, the intermittent input from the East Siberian Sea (ESS) is not. The export flux to the Atlantic Ocean has unknown uncertainty due to a paucity of DIC data from the Canadian Archipelago. Within the region, the Chukchi Sea is the dominant site for atmospheric carbon dioxide (CO2) uptake, while the Beaufort Sea and the Canadian Archipelago take-up much less CO2 with latter potentially a weak source of CO2 during certain times of the year. Additionally, the ESS shelf is a net source of CO2. Summertime CO2 uptake capacity in the deep Canada Basin has increased greatly recently as sea-ice retreat progresses rapidly. The region appears to export more DIC than it receives by a small amount, suggesting that it is probably weakly net heterotrophic. In addition to labile organic carbon (OC) produced in the productive marginal seas, some riverine and coastal erosion-derived OC likely is also recycled. As warming progresses, the Arctic Ocean may produce and export more DIC. Whether this change will turn the Arctic Ocean into a weaker CO2 sink or even a CO2 source for the atmosphere is uncertain and dependent on multiple factors that control the rate of surface water CO2 increase versus the rate of the atmospheric CO2 increase

Whole season net community production in the Weddell Sea

Depletions of total CO2, nitrate, phosphate and silicate in the surface layer were calculated for cruise ANT XXII/3 with FS Polarstern in March 2005 for estimating the annual net community production. East-west across the Weddell Sea the variation of all depletions is similar, but this holds to a lesser extent for silicate. Depletions in March 2005 are 2–3 times larger than those in January 1993 for the same transect. Very low N:P and C:P depletion ratios seem to point to dominance of diatoms, in the central Weddell Sea more than in the margin. Estimates of annual net community productions are about 1.8 and 3.5 mol C m−2 year−1 for the interior Weddell Sea and a near-margin region, respectively. The region does not comply with the classical view of a marginal ice zone with high productivity. Net community production is similar to annual export production, implying that remineralization in the ensuing winter be minor.