Abstract
The correlation between transport via the Bering Strait throughflow (BTF) and sea surface salinity (SSS) in the Bering Sea has been examined mainly using an atmosphere–ocean–ice coupled climate model that has an eddy-permitting ocean component. The SSS anomaly in the northwestern Bering Sea is high from winter to spring when the BTF transport anomaly is large in the cold season. Similar features can be seen in an observation dataset and two kinds of ocean data assimilation product. BTF transport is strongly correlated with sea surface height (SSH) in the northeastern Bering Sea, the southwestern Chukchi Sea and the East Siberian Sea. The SSH along the Russian coast in the Arctic Ocean is uncorrelated with the SSH in the Bering Sea, the meaning being that the Arctic SSH affects the BTF and the SSS independently of the SSH in the Bering Sea. The low SSH along the Siberian coast is correlated with easterly wind anomalies over the Laptev Sea and north of the New Siberian Islands. The relationship between the low Siberian-coast SSH and the high SSS in the Bering Sea, however, is not confirmed in 10 years of satellite-derived SSH. Mixed-layer salt budget analysis has revealed that the high SSS anomalies are mainly caused by the increases of horizontal advective salt convergence north of 62.5°N, and by the decreases of sea-ice melting south of 62.5°N, through the strengthening of the near-surface northeastward currents. In the warm season, these two factors fade and the salinization disappears.
Highlights
Arctic sea ice during summer and autumn has been decreasing, and temperatures have been increasing faster over the Arctic than the global average (e.g., Serreze and Barry 2011; Vaughan et al 2013)
The present study analyzes the output of an atmosphere–ocean–ice coupled climate model to investigate variations in the Bering Sea that originated in the Bering Strait and the Arctic Ocean; we find interannual variations of sea surface salinity (SSS) and surface currents in the northwestern Bering Sea that are linked with those of Bering Strait throughflow (BTF) transport and Arctic sea surface height (SSH)
In the northwestern Bering Sea, the SSS anomaly associated with the BTF transport anomaly became evident from winter to early summer, and SSS lagged behind the BTF by a few months
Summary
Arctic sea ice during summer and autumn has been decreasing, and temperatures have been increasing faster over the Arctic than the global average (e.g., Serreze and Barry 2011; Vaughan et al 2013). Interannual changes in steric forcing over the Bering Strait were controlled by warm inflow into the Arctic Ocean from the North Atlantic, freshwater accumulation in the southwest Canada Basin, and temperature and salinity changes in the upper Bering Sea. Changes in sea surface height (SSH) in the Arctic Ocean are likely to lead to some changes in the Bering Sea. Danielson et al (2014) indicated that easterly winds over the western Chukchi Sea (CS) and the East Siberian Sea (ESS) increased the Pacific-Arctic pressure-head through coastal divergence and shelf waves, the implication being that winds over the Arctic Ocean can change the BTF. The present study analyzes the output of an atmosphere–ocean–ice coupled climate model to investigate variations in the Bering Sea that originated in the Bering Strait and the Arctic Ocean; we find interannual variations of sea surface salinity (SSS) and surface currents in the northwestern Bering Sea that are linked with those of BTF transport and Arctic SSH. We discuss the salt budget in the northwestern Bering Sea in Sects. 4, and 5 provides the conclusions
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