The Influence of Sea Ice Cover and Atlantic Water Advection on Annual Particle Export North of Svalbard

• Published in: Journal of geophysical research. Oceans 2022-10, Vol.127 (10), p.n/a
• Main Authors: Dybwad, C., Lalande, C., Bodur, Y. V., Henley, S. F., Cottier, F., Ershova, E. A., Hobbs, L., Last, K. S., Dąbrowska, A. M., Reigstad, M.
• Format: Article
• Language: English
• Subjects: Advection; Algae; annual particle fluxes; Aquatic crustaceans; Arctic; Arctic sea ice; Atlantification; Carbon; Chlorophyll; Chlorophyll a; Continental shelves; Copepods; Diatoms; Faecal pellets; Fluxes; Geophysics; Grazing; Ice cover; Inflow; Marine ecosystems; Mooring; Ocean floor; Oceans; Organic carbon; Organic matter; Particulate flux; Particulate matter; Particulate organic carbon; Plankton; Protists; Sea ice; seasonal sea ice; Seasonal variability; Seasonal variation; Seasonal variations; Sediment; Sediment traps; Sinking; Surface water; Suspended particulate matter; Traps; vertical carbon export; Winter; Zooplankton
• ISSN: 2169-9275; 2169-9291; 2169-9291
• DOI: 10.1029/2022JC018897

The Arctic Ocean north of Svalbard has recently experienced large sea ice losses and the increasing prominence of Atlantic water (AW) advection. To investigate the impact of these ongoing changes on annual particle export, two moorings with sequential sediment traps were deployed in ice‐free and seasonally ice‐covered waters on the shelf north (NSv) and east (ESv) of Svalbard, collecting sinking particles nearly continuously from October 2017 to October 2018. Vertical export of particulate organic carbon (POC), total particulate matter (TPM), planktonic protists, chlorophyll a, and zooplankton fecal pellets were measured, and swimmers were quantified and identified. Combined with sensor data from the moorings, these time‐series measurements provided a first assessment of the factors influencing particle export in this region of the Arctic Ocean. Higher annual TPM and POC fluxes at the ice‐free NSv site were primarily driven by the advection of AW, higher grazing by large copepods, and a wind‐induced mixing event during winter. Higher diatom fluxes were observed during spring in the presence of sea ice at the ESv site. Along with sea ice cover, regional differences in AW advection and the seasonal presence of grazers played a prominent role in the biological carbon pump along the continental shelf off Svalbard. Plain Language Summary Recently, the area north of Svalbard has experienced the largest reduction of winter sea ice extent in the Arctic Ocean and an increasing influence of warm Atlantic water (AW) in surface waters. The consequences for the marine ecosystem remain unclear. In the present study, we investigated the fate of algal production and organic matter by measuring the amount and composition of the material sinking toward the seafloor. Using sediment traps with automatically rotating bottles, the seasonal variability in the quality and quantity of the organic matter sinking to ∼100 m was investigated at two sites with and without winter sea ice on the shelf north and east of Svalbard from 2017 to 2018. Our results suggest that the AW inflow along the shelf break induces a gradient with more zooplankton in the west and more ice in the east. More zooplankton in the west rework the organic matter through grazing, resulting in higher flux of carbon than in the east. Less zooplankton in the east potentially leaves more algal cells to sink ungrazed. As algal fluxes were higher in the presence of sea ice, a future with less sea ice may result in more