Observed Inhibited Downward Penetration of Wind-Generated Near-Inertial Energy in the Bering Sea

Abstract

Near-inertial waves (NIWs) are energetic in the Bering Sea, but their downward propagation characteristics remain unknown. Here, we first report the penetration of near-inertial energy generated by distinct synoptic wind forcing events using yearlong subsurface mooring data in this region. It is found that approximately half of the near-inertial energy efficiently penetrates into the deep ocean in wintertime. However, in summertime with a shallow mixed layer, the downward propagating NIWs are constrained to the region of strong near-surface stratification with the surface warming and residual winter cold water, resulting in the absence of near-inertial energy below the permanent pycnocline. Meanwhile, the downward propagating NIWs are partially reflected upward due to the abrupt changes in stratification above the dichothermal water. Given the high vertical shear of NIWs, the present work is important for understanding ocean mixing, upward heat transfer, and sea-ice melting in the subarctic and the broader Arctic.