The Xiamen Symposium on Marine Environmental Sciences (XMAS 2027)

Since the 1990s, discharge from the Greenland Ice Sheet into the North Atlantic has increased in response to anthropogenic climate change.  Runoff and calved ice volumes from Greenland into the North Atlantic are increasingly well constrained, but there is not yet consensus on the associated sediment fluxes, changes to marine nutrient dynamics, or effects on marine productivity. In summer 2024 we conducted surveys of three glacier fjord systems in southeast Greenland with contrasting geomorphology, glacier dynamics, and latitude. Full depth profiles revealed extensive subsurface particle plumes from marine-terminating glaciers which are not captured in existing sediment flux estimates. Combined with observations of pelagic biogeochemistry, and ROMS estimates of fjord-shelf exchange, we evaluate the effects of increasing glacier discharge on fjord-scale biogeochemical budgets. Our findings underscore the significant sediment inputs occurring around Greenland, with the Ice Sheet providing >14% of global marine sediment input. Yet a large fraction of this sediment is trapped in inner-fjord environments, limiting the consequential biogeochemical effects further downstream. Furthermore, despite large sediment and meltwater inputs, nutrient budgets for the fjord regions remain dominated by inflow of nutrient-rich Atlantic Water (>98% of fjord silica supply). Changes to fjord-shelf exchange are thus likely the first order control on regional nutrient budgets.