Tides, Internal and Near-Inertial Waves in the Yermak Pass at the Entrance of the Atlantic Water to the Arctic Ocean.

In the crucial region of the Yermak Plateau where warm Atlantic water enters the Arctic ocean, we examined high frequency variations in the Yermak Pass Branch over a 34 months-long mooring data set. The mooring was ice covered only half of the time with ice-free periods both in summer and winter. We investigated the contribution of residual tidal currents to the low frequency flow of Atlantic Water (AW) and high frequency variations in velocity shears possibly associated with internal waves. High resolution model
simulations including tides show that diurnal tide forced an anticyclonic circulation around the Yermak Plateau. This residual circulation helps the northward penetration of the AW into the Arctic. Tides should be taken into account when examining low frequency AW inflow. High frequency variations in velocity shears are mainly concentrated in a broad band around 12 hr in the Yermak Pass. Anticyclonic eddies, observed during ice-free conditions, modulate the shear signal. Semi-diurnal internal stationary waves dominate high frequency variations in velocity shears. The stationary waves could result from the interaction of freely propagating semi-diurnal internal waves generated by diurnal barotropic tides on critical slopes around the plateau. The breaking of the stationary waves with short length scales possibly contribute to mixing of AW at the entrance to the Arctic.