An ITP observed warm core eddy is produced by fresh water intrusion in the subsurface Beaufort Sea

Abstract

A subsurface eddy was detected via in situ observations, which was also reproduced via reanalysis data. The whole process determined on the basis of numerical model simulations is described below. Since the late summer of 2014, the low sea level pressure (SLP) center has been gradually replaced by a high SLP center over the Beaufort Sea in a month. In response to SLP variations, cyclonic surface winds have been gradually replaced by anticyclonic surface winds, inducing Ekman pumping along the southern edge of the Beaufort Sea and downwelling in the interior of the Beaufort Sea. As a result, surface water, which is warmer and fresher, was transported downward into the subsurface in the interior of the Beaufort Sea. With a uniform current velocity, warm and fresh water can intrude into the cold salt water, which produced a horizontal density gradient and front. Front slumped and mesoscale eddies were generated via a baroclinic instability mechanism. However, numerical simulations suggest that continuous fresh water intrusion rather than the front slump determines eddy strength.