Multi-Sensor Observations Reveal Large-Amplitude Nonlinear Internal Waves in the Kara Gates, Arctic Ocean

Abstract

We present multi-sensor measurements from satellites, unmanned aerial vehicle, marine radar, thermal profilers, and repeated conductivity–temperature–depth casts made in the Kara Gates strait connecting the Barents and the Kara Seas during spring tide in August 2021. Analysis of the field data during an 18-h period from four stations provides evidence that a complex sill in the Kara Gates is the site of regular production of intense large-amplitude nonlinear internal waves. Satellite data show a presence of a relatively warm northeastward surface current from the Barents Sea toward the Kara Sea attaining 0.8–0.9 m/s. Triangle-shaped measurements using three thermal profilers revealed pronounced vertical thermocline oscillations up to 40 m associated with propagation of short-period nonlinear internal waves of depression generated by stratified flow passing a system of shallow sills in the strait. The most intense waves were recorded during the ebb tide slackening and reversal when the background flow was predominantly supercritical. Observed internal waves had wavelengths of ~100 m and traveled northeastward with phase speeds of 0.8–0.9 m/s. The total internal wave energy per unit crest length for the largest waves was estimated to be equal to 1.0–1.8 MJ/m.

Decline in Ice Coverage and Ice-Free Period Extension in the Kara and Laptev Seas during 1979–2022

“…These areas correspond to spreading areas of the Ob-Yenisei and Lena plumes [62,63] and, therefore, they are the areas of early ice formation in autumn due to strong vertical stratification [64,65]. The inflow of warm water from the Barents Sea to the Kara Sea is the most important process that causes sea ice reduction in the study area [55,56]. This process affects both DOR and DOA and its influence is localized along the eastern coast of Novaya Zemlya (Figures 6 and 8).…”

“…Note that near the Kara Gates Strait, the observed LTM for DOA occurs later than in the surrounding areas, namely, in the first ten-day period of November. This feature is caused by the influence of warmer and saltier Barents Sea waters, which inflow into the Kara Sea in this area [54,55]. The late occurrence of DOA near the northern cape of Novaya Zemlya is associated with the spreading of warm surface water from the Barents Sea caused by eastward propagation of the Barents Sea branch of Atlantic water [56].…”