The biogeochemistry of ocean-ice interaction around Greenland

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In this project we will use Greenland’s coast as an ideal target for a process study to investigate how changes to the hydrological cycle affect the biogeochemistry and productivity of the ocean.With increasing annual discharge from the Greenland Ice Sheet (GrIS), a critical question is how this outflow of freshwater affects the productivity of shelf seas around Greenland. The GrIS is the second largest Icesheet on Earth. As freshwater enters the ocean from the GrIS it creates strong physical and biogeochemical gradients in coastal waters around the island. These gradients are most pronounced in Greenland’s fjords which, by surface area, are among the largest of marine carbon sinks. Greenland’s fjords and shelf seas are also home to nationally important fisheries, the future of which is of pivotal importance for Greenland’s economy.Whilst it is widely recognized that freshwater inputs from glaciers affect regional ocean circulation, our understanding of links between the physics of meltwater release and long-term changes to marine biogeochemistry is in its infancy. A topic of present interest to the Intergovernmental Panel on Climate Change (IPCC) is how the cryosphere and ocean will interact biogeochemically in a warming climate. The main objective here will be to determine how the physical and chemical changes induced by increased freshwater inputs to the ocean around Greenland affect nutrient (macronutrient and micronutrient) availability to phytoplankton and thus primary production.By combining fieldwork with idealized models, the effects of the three main different freshwater sources (surface runoff, subsurface discharge and iceberg melt) will be determined. The chemistry of the estuarine mixing process- which often induces rapid shifts in the chemical form and thus bioavailability of nutrients- as freshwater mixes with saline water will be investigated. The nutrient-limitation status of phytoplankton communities in freshwater affected regions around Greenland will be determined, and the net effect of concurrent changes to the physical and chemical composition of the water column will thus be assessed.It will therefore be possible to understand the effects of increasing freshwater into the polar ocean in terms of changes to the primary production in the marine environment.