Processes Contributing to Bering Sea Temperature Variability in the Late Twentieth and Early Twenty-First Century

Abstract

Abstract Over recent decades, the Bering Sea has experienced oceanic and atmospheric climate extremes, including record warm ocean temperature anomalies and marine heatwaves (MHWs), and increasingly variable air–sea heat fluxes. In this work, we assess the relative roles of surface forcing and ocean dynamical processes on mixed layer temperature (MLT) tendency by computing a closed mixed layer heat budget using the NASA/JPL Estimating the Circulation and Climate of the Ocean (ECCO) Ocean State and Sea Ice Estimate. We show that surface forcing drives the majority of the MLT tendency in the spring and fall and remains dominant to a lesser degree in winter and summer. Surface forcing anomalies are the dominant driver of monthly mixed layer temperature tendency anomalies (MLTa), driving an average of 72% of the MLTa over the ECCO record length (1992–2017). The surface turbulent heat flux (latent plus sensible) accounts for most of the surface heat flux anomalies in January–April and September–December, and the net radiative flux (net longwave plus net shortwave) dominates the surface heat flux anomalies in May–August. Our results suggest that atmospheric variability plays a significant role in Bering Sea ocean temperature anomalies through most of the year. Furthermore, they indicate a recent increase in ocean warming surface forcing anomalies, beginning in 2010. Significance Statement In recent years, the Bering Sea has experienced extremes in ocean temperature, which have had adverse impacts on ocean ecology and marine fisheries and have contributed to increasingly variable sea ice extent. Our results identify anomalous heating by air–sea heat flux anomalies as the process responsible for most of the observed ocean temperature anomalies over the period 1992–2017. We additionally show that there has been an increase in atmosphere-driven ocean warming since 2010. Our work highlights the importance of investigating how ocean–atmosphere interactions might change under future climate change and how this will impact the Bering Sea.