Separation of the Icelandic Coastal Current from the Reykjanes Peninsula

Abstract

The Icelandic Coastal Current (ICC) is a buoyant flow fueled by multiple rivers. Satellite observations during the October–November 2019 study period indicate the ICC often separates from the southwest tip of the Reykjanes Peninsula; it subsequently has large offshore excursion during west-southwestward winds. Results from a high-resolution realistic simulation exhibit this ICC behavior and provide detail on the associated currents and salinities. Sensitivity tests with simplified bathymetry, no winds, or no local buoyancy inputs are compared to the standard run to isolate contributions of those factors to flow separation. Analysis indicates that ICC separation occurs because the coast turns more tightly than the inertial radius; this behavior is consistent with inviscid theory. Partial flow deflection over the shelf expression of the Reykjanes Ridge and the widening shelf both increase ICC offshore excursion. The ICC is strongly influenced by the barotropic wind response to west-southwestward winds that includes a downshelf jet (flowing in the direction of Kelvin wave propagation) along the coast upshelf of the peninsula's tip where winds are downwelling-favorable, the downshelf extension of the jet that bends around the peninsula and progresses farther offshore with isobaths, a band of offshore and upshelf currents along the coast downshelf of the peninsula's tip, and surface flow aligned with Ekman transport located offshore beyond the downshelf jet. Similar wind-influence scenarios are discussed for other plumes. There are likely many such hotspots for offshore freshwater transport around the world.