CoAuthors

Ou Wang (Jet Propulsion Laboratory, United States); Ian Fenty (Jet Propulsion Laboratory, United States)

Over the last two decades, sea-level across the arctic’s Beaufort Sea has been rising faster than its global mean by an order of magnitude (Figure a). Beaufort Sea’s rapid sea-level rise is mainly a halosteric change (Figure b), reflecting an increase in freshwater content greater than that associated with the Great Salinity Anomaly of the 1970s, raising the possibility of future disruptions in large-scale ocean circulation and climate. Here we provide a new perspective of this Beaufort Sea variation by quantifying its causal mechanism from 1992 to 2017 using a global, data-constrained ocean and sea-ice estimate of the Estimating the Circulation and Climate of the Ocean (ECCO) consortium.

Analysis reveals that the variation is driven by a combination of wind stress and sea-ice (Figure c). Seasonal variation mainly reflects near-surface change due to the annual melting and freezing of sea-ice while interannual change extends deeper and mostly relates to wind-driven Ekman transport. Increasing wind stress and sea-ice melt are, however, equally important for decadal change that dominates the overall variation. Strengthening anticyclonic wind stress surrounding Beaufort Sea intensifies the ocean’s lateral Ekman convergence of relatively fresh surface waters. The strengthening stress also enhances convergence of sea-ice and ocean heat that increase the amount of Beaufort Sea’s net sea-ice melt (Figure d). The enhanced significance at longer time-scales of sea-ice melt relative to direct wind forcing can be attributed to the ocean’s mixing of melt-water being slower than its dynamic adjustment to mechanical perturbations. The spin-up difference implies that, on their own, the sea-ice-melt-driven diabatic change will last much longer than the direct wind-driven kinematic anomaly.