Structure and Variability of the Barrow Canyon Outflow From Two High-Resolution Shipboard Surveys in 2018

Abstract

Barrow Canyon in the northeast Chukchi Sea is a critical choke point where Pacific-origin water, heat, and nutrients enter the interior Arctic. While the flow through the canyon has been monitored for more than 20 years, questions remain regarding the dynamics by which the Pacific-origin water is fluxed offshore, as well as what drives the variability. In 2018, two high-resolution shipboard surveys of the canyon were carried out—one in summer and one in fall—to investigate the water mass distribution and velocity structure of the outflow. During the summer survey, high percentages of Pacific water (summer water + winter water) were present seaward of the canyon, associated with strong northward outflow from the canyon and a well-developed westward-flowing Chukchi Slope Current (CSC). By contrast, high percentages of Pacific water were confined to the canyon proper and outer Chukchi shelf during the late-fall survey, at which time the canyon outflow and CSC were considerably weaker. These differences can be attributed to differences in wind forcing during the time period of two surveys. A cyclone-like circulation was present in the canyon during both surveys, which was also evident in the satellite-derived sea surface height anomaly field. We argue that this feature corresponds to an arrested topographic Rossby wave, generated as the outflow responds to the deepening bathymetry of the canyon. By applying a self-organizing map analysis using the satellite altimeter data from 2001 to 2020, we demonstrate that such a cyclone-like structure is a prevailing aspect of the canyon outflow.