Growth and Decay of Baroclinic Eddies in the Seasonally Ice-Covered Arctic Ocean

Gianluca Meneghello, Massachusetts Institute of Technology, Cambridge, MA, United States, John C Marshall, MIT, Cambridge, MA, United States, Camille Lique, Laboratoire de Physique des Océans, Ifremer, Brest, France, Pal Erik Isachsen, University of Oslo, Oslo, Norway, Edward Doddridge, Massachusetts Institute of Technology, Earth, Atmospheric and Planetary Sciences, Cambridge, MA, United States, Jean-Michel Campin, M.I.T./EAPS, Cambridge, United States, Heather Regan, NERC British Antarctic Survey, Cambridge, United Kingdom; IUEM Institut Universitaire Européen de la Mer, Laboratoire d'Oceanographie Physique et Spatiale, Plouzané, France and Claude Talandier, CNRS, Laboratoire d'océanographie physique et spatiale, Plouzane, France
Abstract:
Baroclinic eddies play an important role in the equilibrium of the large-scale circulation, ventilation of tracers, upper-ocean biology, and pollutant dispersion in the ocean. In the Arctic, observational evidence shows a curious, and hitherto unexplained, vertical distribution of eddy kinetic energy. A marked seasonal cycle is found close to the surface: strong eddy activity during summer, observed from both satellites and moorings, is followed by very quiet winters. In contrast, subsurface eddies persist all year long within the deeper halocline. Informed by baroclinic instability analysis, and a high resolution pan-Arctic ocean model, we explore the origin and evolution of baroclinic eddies in the seasonally ice-covered Arctic Ocean. Mixed-layer baroclinic eddies are generated in the summer and decay in the winter as the growth of ice enhances decay of eddies. Meanwhile baroclinic eddies which obtain their energy from the halocline below persist year round and are less susceptible to the seasonal cycle.