Eddy Shedding from a Pacific Summer Water Plume

Eddies containing Pacific Summer Water are common in the western Arctic basin. They are thought to arise from instabilities in the Alaskan Coastal Current as it flows over the mouth of Barrow Canyon and along the slope. Carrying water that is significantly warmer than the freezing temperature, and with salinities much lower than the ambient water, they may play an important role in setting the stratification of an increasingly ice-free Arctic. Eddies have been observed near the shelf break both to the west and east of Barrow Canyon and work has been done to quantify the heat and freshwater fluxes they supply to the Arctic. The details of their formation, however, are still unclear. Under what conditions do they fully separate from the mean flow?

During a September 2018 cruise, we made several observations of packets of Pacific Summer Water separating from the Alaskan Coastal Current as it entered the Beaufort Sea. These observations were made both in the vicinity of Barrow Canyon and farther to east where the meandering plume appeared to be pinching off intrahalocline eddies at its edges. Using a suite of in-situ measurements including closely-spaced CTD profiles, microstructure, and velocity, along with remote sensing measurements of sea surface temperature, surface chlorophyll, and synthetic aperture radar, we examine the processes that lead to the shedding of these eddies.