The East Greenland Polar Front as a Mediator of Climate-Ocean-Ecosystem Variability Along Southeast Greenland

The southeast Greenland region features a confluence of Arctic- and Atlantic origin waters along the continental shelf-break, forming the East Greenland Polar Front (EGPF). Here we examine the role of the EGPF in mediating climate-ocean-ecosystem variability. We observe systematic temporal variability in frontal intensity related to regional subpolar gyre (SPG) dynamics via gyre spin-up. By combining sea surface temperature derived frontal metrics with sea surface height, sea-ice concentration, surface chlorophyll-a concentration, and fisheries survey data, we demonstrate how gyre-induced oceanic variability is reflected in the shelf ecosystem. Elevated chlorophyll-a concentrations along the continental slope correspond to periods when the SPG is in a negative phase, the Irminger Gyre is spun-up and the EGPF is strong. This response in chlorophyll-a is likely due to a combination of aggregation of phytoplankton at the frontal zone and enhanced new production fueled by increased nutrient availability. In addition to the temporal variability, the EGPF exhibits spatial variability on seasonal and interannual timescales across the wide Ammassalik shelf. As such, the EGPF has migrated 90 km shoreward in tandem with sea-ice retreat since the early 2010s. This migration led to increased chlorophyll-a concentrations over shallow banks and decreased chlorophyll-a concentrations over the outer shelf and slope areas. Our findings underscore the critical role of the EGPF in mediating interactions between the physical and biological components of the southeast Greenland ecosystem.