Abstract
The Arctic Ocean has been identified as a key global carbon sink but worsening global climate change effects including decreased sea-ice extent, increased area of ocean acidification, and ecosystem shifts, will impact the region’s ability to take up CO₂. To better understand the biological pump in the Arctic and how it affects the region’s CO₂ uptake efficiency, particulate carbon data was collected via in situ, large-volume pumping in the upper 500 m of the western Arctic Ocean in September-October 2022 on board the U.S. Coast Guard Cutter Healy (HLY-22-02). These results provided evidence that the region has an overall weak biological pump as compared to other ocean systems. Particulate organic carbon (POC) concentrations were ≤ 0.183 µmol/L in the basins. Maximum POC concentrations of only up to 0.944 µmol/L were observed over the Chukchi Slope where a diatom bloom was observed by the HLY-22-02 scientists and high copepod abundance in October. δ¹³POC values and organic C/N ratios supported the view that remineralized POC was advected off the shelf into the adjacent basin interior. δ¹⁵N values suggested enhanced biological repackaging of the phytoplankton bloom around the margin and remineralization at depth in the basins. Particulate inorganic carbon (PIC) concentrations were ≤ 9.69 nmol/L across all stations and depths, a reflection of pervasive carbonate undersaturation of Arctic waters hindering the formation of calcium carbonate. Small size fraction (1-51 µm) POC concentrations were substantially greater than large size fraction (> 51 µm) concentrations, and displayed distributions that were clearly affected by offshore lateral advection, remineralization, and carbonate undersaturation. Global climate change impacts on the Arctic Ocean over the past several decades including enhanced sea-ice loss, warming, freshening, decreasing alkalinity, and probable shifts in primary productivity, likely will negatively impact the region’s particulate carbon cycling, carbon fluxes, and long-term CO₂ uptake efficiency into the future.