Description: A decade of particle flux measurements providse the basis for a comparison of the eastem and westem provinces ofthe Nordic Seas. Ice-related physical and biological seasonality as well as pelagic settings jointly control fluxes in the westem Polar Province which receives southward flowing water of Polar origin. Sediment trap data from this realm highlight a predominantly physical flux control which leads to exports of siliceous particles within the biological marginal ice zone as a prominent contributor. In the northward flowing waters of the eastem Atlantic Province, feeding Strategie . life histories and the succession of dominant mesozooplankters (copepods and pteropods) are central in controlling fluxes. Furthermore, more calcareous matter is exported here with a shift in flux seasonality towards surnrner/autumn. Dominant pelagic processes modeled numerically as to their impact on annual organic carbon exports for both provinces confirrn that interannual flux variability is related to changes in the respective control mechanisms. Annual organic carbon exports are strikingly similar in the Polar and Atlantic Provinces (2.4 and 2.9 g m-2 y-1 at 500 m depth). despite major differences in flux control. The Polar and Atlantic Provinces. however, can be distinguished according to annual fluxes of opal ( l.4 and 0.6 g m-2 y-1) and carbonate (6.8 and 10.4 g m-2 y-1). lnterannual variability may blur this in single years. Thus. it is vital to use multi-annual data sets when including particle exports in general biogeochemical province descriptions. Vertical flux profiles (collections from 500 m, l000 min both provinces and 300-600 m above the seafloor deviate from the general vertical decline of fluxes due to particle degradation during sinking. At depths 〉 1000 m secondary fluxes (laterally advected/re uspended particles) are often juxtaposed to primary (pelagic) fluxes, a pattem which is most prominent in the Atlantic Province. Spatial variability within theAtlantic Province remains poorly understood. and the same holds true for interannual variability. No proxies are at hand for this province to quantitatively relate fluxes to physical or biological pelagic properties. For the easonally ice-covered Polar Province a robust relationship exists between particle export and ambient ice-regime (Ramseier et al. this volume; Ramseier et al. 1999). Spatial flux pattems may be differentiated and interannual variability can be analyzed in this manner to improve our ability to couple pelagic export pattems with benthic and geochemical sedimentary processes in seasonally ice-covered seas.

Description: As part of the HAUSGARTEN long-term observatory, sediment trap deployments were carried out before, during, and after the anomalously warm Atlantic Water inflow observed from 2005 to 2007 in the eastern Fram Strait. Downward export of particulate organic carbon (POC), zooplankton fecal pellet carbon (FPC), and biogenic particulate silica (bPSi) were measured from August 2002 to June 2003 and from July 2004 to July 2008 to indirectly assess the impact of the warm anomaly on phytoplankton and zooplankton communities in the region. Lower and less frequent bPSi fluxes were observed during most of the warm anomaly period, reflecting a shift in phytoplankton community composition towards dominance of small-sized phytoplankton under warmer conditions. Lower FPC fluxes observed concurrently with the lower bPSi fluxes may indicate a decrease in fecal pellet production due to changing feeding conditions. In addition, the export of smaller fecal pellets in fall 2005 and spring 2006 suggests a dominance of smaller zooplankton during the warm anomaly. Nonetheless, bPSi and FPC export always increased in the presence of ice cover in the area above the sediment trap, even during the warm anomaly period, suggesting that sea ice is a key factor influencing the frequency of export events in the eastern Fram Strait. The scarcity of ice over the sampling area in 2005 and 2006 may partly be due to the warm anomaly, although solar radiation and ice drift due to wind stress also govern ice cover extent in the region. Overall, the warm anomaly resulted in a shift in the composition of the export fluxes when associated with an absence of ice cover in the eastern Fram Strait.