Western Greenland Ice Sheet-Land-Ocean Interactions: Near-Shore Dissolved Organic Carbon 14C Ages and Composition in Eastern Baffin Bay

Abstract

Greenland's ongoing deglaciation and thawing permafrost, accompanied by an increase in ice sheet freshwater discharge and nutrient export, are significantly impacting the surrounding fjords and marine ecosystems. Understanding the geochemical linkages between ice, land, and marine environments is crucial for comprehending the effects of amplified cryosphere-biosphere interactions on marine ecosystems. To assess dissolved organic carbon (DOC) geochemistry along Greenland's west coast, we characterized and collected water samples at twelve near-shore stations, at depths of 5 and 50 m, in four key areas: Nuuk, Davis Strait, Disko Bay, and the Uummannaq fjord system, focusing on DOC as it represents the largest pool of organic carbon in the ocean. Analysis of DOC concentration, molecular composition, ¹³C, and ¹⁴C alongside measurements of water temperature, salinity, and stable isotopic composition, revealed that: (a) water masses were predominantly ocean water, albeit with substantial freshwater components, particularly in the most glaciated region. (b) DOC ages range from approximately 1,589 to 2,450 cal BP. (c) Despite exhibiting the greatest freshening, the Uummannaq fjord system surprisingly contained the oldest DOC among all sites. This unexpected observation is postulated to be linked to inputs of ancient carbon from discharge from marine-terminating glaciers. Our findings underscore the potential influence of spatially heterogeneous inputs of new terrestrial sources of DOC, particularly ancient permafrost-derived carbon, to the Arctic carbon cycle especially as glacial melt intensifies in the future. Furthermore, our study provides valuable insights into the age and composition of DOC exported from west Greenland into the adjoining marine system.