Wind-Driven Freshwater Buildup in the Beaufort Gyre is Enevitably Constraned by Mesoscale Eddies.

Abstract:

Recently the Beaufort Gyre has accumulated over 20km³ of freshwater. This accumulation has been partially attributed to strong anticyclonic atmospheric winds that are prevailing over the gyre for almost two decades. However, mechanisms that can counteract the tendency of the anticyclonic wind stress to deepen the halocline are not well understood. Here, we explore the key physical processes affecting the wind-driven accumulation of freshwater within an idealized high resolution model of the Beaufort Gyre. We demonstrate that an equillibrated halocline (with bulk properties consistent with observations) is achieved when the mesoscale eddy field becomes strong enough to counteract the Ekman pumping. We derive analytical scalings for the depth of the haloclione and its spin-up time scale uncovering the physics behind their strong relation to the eddy dynamics. Our study further suggests that the Beaufort Gyre halocline and its freshwater content are currently in a state of high sensitivity to atmospheric winds. Nonetheless, a significant intensification of surface wind stress would lead to a near saturation of the gyre's freshwater content at about 35m -- a constraint inherently set by the intricacies of the mesoscale eddy dynamics.