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Abstract Seasonal phytoplankton blooms in Greenland’s coastal waters form the base of marine food webs and contribute to oceanic carbon uptake. In Qeqertarsuup Tunua, West Greenland, a secondary summertime bloom follows the Arctic spring bloom, enhancing annual primary productivity. Emerging evidence links this summer bloom to subglacial discharge from Sermeq Kujalleq, the most active glacier on the Greenland Ice Sheet. This discharge drives localized upwelling that may alleviate nutrient limitation in surface waters, yet this mechanism remains poorly quantified. Here, we employ a high-resolution biogeochemical model nested within a global state estimate to assess how discharge-driven upwelling influences primary productivity and carbon fluxes. We find that upwelling increases summer productivity by 15–40% in Qeqertarsuup Tunua, yet annual carbon dioxide uptake rises by only  ~3% due to reduced solubility in plume-upwelled waters. These findings suggest that intensifying ice sheet melt may alter Greenland’s coastal productivity and carbon cycling under future climate scenarios. 

Abstract Knowledge about seafloor depth, or bathymetry, is crucial for various marine activities, including scientific research, offshore industry, safety of navigation, and ocean exploration. Mapping the central Arctic Ocean is challenging due to the presence of perennial sea ice, which limits data collection to icebreakers, submarines, and drifting ice stations. The International Bathymetric Chart of the Arctic Ocean (IBCAO) was initiated in 1997 with the goal of updating the Arctic Ocean bathymetric portrayal. The project team has since released four versions, each improving resolution and accuracy. Here, we present IBCAO Version 5.0, which offers a resolution four times as high as Version 4.0, with 100 × 100 m grid cells compared to 200 × 200 m. Over 25% of the Arctic Ocean is now mapped with individual depth soundings, based on a criterion that considers water depth. Version 5.0 also represents significant advancements in data compilation and computing techniques. Despite these improvements, challenges such as sea-ice cover and political dynamics still hinder comprehensive mapping.