Seasonal variability in particle fluxes on the slopes of the East Siberian Sea and Chukchi Sea

Abstract

Time-series sediment traps were deployed on the East siberian Sea and the Chukchi Sea slopes from August 2017 to August 2018 with the aim of understanding the temporal and spatial variations of particle flux and finding out the main processes affecting their variations. Particle fluxes showed a typical seasonal variation with high values in summer and low values in other seasons, and a large inter-annual variation was observed only in the East Siberian Sea slope where particle fluxes were one order of magnitude higher in summer 2018 than in summer 2017. This large inter-annual variation in particle flux resulted from the episodic intrusion of the nutrient-enriched shelf water in the East Siberian Sea, which enhanced biological production at the surface and particle fluxes. The Chukchi Sea slope was influenced by the inflow of the Anadyr water, with the high salinity and high nutrient concentrations, which had little annual variability. Therefore, particle flux showed little inter-annual variation on the Chukchi Sea slope. Under-ice phytoplankton blooms were observed in both the East Siberian Sea and the Chukchi Sea slopes, and increases in particulate organic carbon (POC) flux and the C:N ratio under the sea-ice were related to the transparent exopolymer production by ice algae. On the East Siberian Sea slopes, particle fluxes increased slightly from 115 m to 335 m, indicating the lateral transport of suspended particle matter; POC and lithogenic particles may be laterally transported to the slope as nutrient-rich shelf waters flowed from the East Siberian Sea to the Makarov Basin. Annual POC fluxes were 2.3 and 2.0 g C m-2 yr-1 at 115 m and 335 m, respectively, on the East Siberian Sea slope and was 2.1 g C m-2 yr-1 at 325 m on the Chukchi Sea slope. Annual POC fluxes were higher on the East Siberian Sea and the Chukchi Sea slopes than in Arctic basins, lower than on Arctic shelves, and generally similar to those on western Arctic slopes.