Mesoscale Atlantic water eddy off the Laptev Sea continental slope carries the signature of upstream interaction

Abstract

A mesoscale eddy formed by the interaction of inflows of Atlantic water (AW) from Fram Strait and the Barents Sea into the Arctic Ocean was observed in February 2005 off the Laptev Sea continental slope by a mooring equipped with a McLane Moored Profiler. The eddy was composed of two distinct, vertically aligned cores with a combined thickness of about 650 m. The upper core of approximately ambient density was warmer (2.6°C), saltier (34.88 psu), and vertically stably stratified. The lower core was cooler (0.1°C), fresher (34.81 psu), neutrally stratified and ∼0.02 kg/m3 less dense than surrounding ambient water. The eddy, homogeneous out to a radius of at least 3.4 km, had a 14.5 km radius of maximum velocity, and an entire diameter of about 27 km. We hypothesize that the eddy was formed by the confluence of the Fram Strait and Barents Sea AW inflows into the Arctic Ocean that takes place north of the Kara Sea, about 1100 km upstream from the mooring location. The eddy's vertical structure is likely maintained by salt fingering and diffusive convection. The numerical simulation of one‐dimensional thermal and salt diffusion equations reasonably reproduces the evolution of the eddy thermohaline patterns from the hypothesized source area to the mooring location, suggesting that the vertical processes of double‐diffusive and shear instabilities may be more important than lateral processes for the evolution of the eddy. The eddy is able to carry its thermohaline anomaly several thousand kilometers downstream from its source location.