PARTICLE DYNAMICS AND SEDIMENTATION AT THE BARENTS SEA ICE-MARGIN

The Barents Sea marginal ice zone (MIZ) is one of the most dynamic areas in the world ocean. This biologically productive area undergoes extreme intra- and inter-annual variability in sea ice and water mass transport. Here, we investigate the relationship between the MIZ and seasonal and inter-annual patterns of seafloor burial processes. Sediment profiles of the radionuclides ²³⁴Th, ²¹⁰Pb, and ¹³⁷Cs, along with sediment carbon, nitrogen and phosphorus concentrations, are examined in three regions of different ice cover frequency: predominantly open water (POW), MIZ, and predominantly ice-covered (PIC). ²³⁴Th derived bioturbation rates (16.2 - 18.6 cm² yr^-1) and ²¹⁰Pb based sedimentation rates (0.16-0.31 cm yr^-1) are similar in both PIC and MIZ areas, with bioturbation (3.9 – 9.6 cm² yr^-1) and sedimentation (0.11-0.17 cm yr^-1) rates lowest in POW areas. Sedimentation rates also indicate a longitudinal gradient, increasing from west to east. The MIZ has an approximately 4-fold higher ²¹⁰Pb inventory indicating an area of enhanced scavenging and sediment deposition. Organic and total carbon concentrations (1-3%) are highest in sediment cores collected from the MIZ, with sediment organic C/N ratios ranging from 7-12. The MIZ is further associated with a maximum in sedimentary organic carbon flux (2.2 – 2.7 mg cm^-2 y^-1). Overall we find a clear pattern of higher sediment accumulation and mixing rates and higher nutrient concentrations in sediments within the MIZ. Negative correlations are observed between sea-ice cover and OC, IC, OP and IP content in the sediments in all cases, confirming the hypothesis that primary productivity increases with decreasing ice cover. Therefore, we hypothesize that a climate-driven northward shift in the position of the MIZ will move the region of high sediment accumulation further north thereby affecting the availability of preformed nutrients to the Eurasian Basin, as well as significant changes in the benthic community.