Impacts of Greenland freshwater discharge on fjord productivity: a long-term perspective

In the past few decades, warming of the Arctic region has resulted in an abrupt increase of freshwater discharge from the Greenland Ice Sheet into its surrounding ocean. Greenland fjords are modulated by ice-ocean interactions and are very productive ecosystems that sustain important fisheries and other societal ecosystem services. While many studies are ongoing to understand seasonal and inter-annual changes, very little is known about the long-term impacts of freshwater discharge on primary producers and overall Arctic marine ecosystem functioning and structure. This long-term perspective is particularly important because freshwater runoff is expected to increase in the future along with rising atmospheric temperatures. Here, we present records from three marine sediment cores from the Godthåbsfjord that were used to reconstruct past marine productivity and freshwater discharge. The results based on diatom assemblages, BSi and TOC indicate marked fluctuations in past fjord productivity since the end of the Medieval Climate Anomaly, and periodical bursts of freshwater into the fjord resulting in a lowered productivity.