Coupled wind-forced controls of the Bering–Chukchi shelf circulation and the Bering Strait throughflow: Ekman transport, continental shelf waves, and variations of the Pacific–Arctic sea surface height gradient

Abstract

Available online xxxx a b s t r a c tWe develop a conceptual model of the closely co-dependent Bering shelf, Bering Strait, and Chukchi shelf circulation fields by evaluating the effects of wind stress over the North Pacific and western Arctic using atmospheric reanalyses, current meter observations, satellite-based sea surface height (SSH) measurements, hydrographic profiles, and numerical model integrations. This conceptual model suggests Bering Strait transport anomalies are primarily set by the longitudinal location of the Aleutian Low, which drives oppositely signed anomalies at synoptic and annual time scales. Synoptic time scale variations in shelf currents result from local wind forcing and remotely generated continental shelf waves, whereas annual variations are driven by basin scale adjustments to wind stress that alter the magnitude of the along-strait (meridional) pressure gradient. In particular, we show that storms centered over the Bering Sea excite continental shelf waves on the eastern Bering shelf that carry northward velocity anomalies northward through Bering Strait and along the Chukchi coast. The integrated effect of these storms tends to decrease the northward Bering Strait transport at annual to decadal time scales by imposing cyclonic wind stress curl over the Aleutian Basin and the Western Subarctic Gyre. Ekman suction then increases the water column density through isopycnal uplift, thereby decreasing the dynamic height, sea surface height, and along-strait pressure gradient. Storms displaced eastward over the Gulf of Alaska generate an opposite set of Bering shelf and Aleutian Basin responses. While Ekman pumping controls Canada Basin dynamic heights (Proshutinsky et al., 2002), we do not find evidence for a strong relation between Beaufort Gyre sea surface height variations and the annually averaged Bering Strait throughflow. Over the western Chukchi and East Siberian seas easterly winds promote coastal divergence, which also increases the along-strait pressure head, as well as generates shelf waves that impinge upon Bering Strait from the northwest.

Holocene dynamics in the Bering Strait inflow to the Arctic and the Beaufort Gyre circulation based on sedimentary records from the Chukchi Sea

“…In contrast, a mostly negative AO in the late Holocene can be inferred from mineralogical proxy data indicating a general decline in the BSI after 4 ka ), which could be attributed to a stronger Aleutian Low (Danielson et al, 2014) that typically corresponds to the negative AO (Overland et al, 1999). Olsen et al (2012) also concluded that the AO tended to be mostly negative from 4.2 to 2.0 ka based on a redox proxy record from a Greenland lake.…”

“…Recently, a conceptual model of the BSI controls has been developed based on a decade of oceanographic observations (Danielson et al, 2014). According to this model, storms centered over the Bering Sea excite continental shelf waves on the eastern Bering shelf that intensify the BSI on synoptic timescales, but the integrated effect of these storms tends to decrease the BSI on annual to decadal timescales.…”

“…Finally, BSI can be controlled by the regional wind patterns in the Bering Sea (Danielson et al, 2014), as explained above in Sect. 2.1.…”

Advection in polar and sub-polar environments: Impacts on high latitude marine ecosystems

“…In the Pacific sector, frequent low-pressure systems (storms) exert strong control over the western Arctic and sub-Arctic through their influence on ocean circulation patterns, mixing and upwelling (Overland, 1986;Isoguchi et al, 1997;Pickart et al, 2009), and link the two regions through oceanic forcing. For example, these storms mediate flow variations in Bering Strait (e.g., Roach et al, 1995;Cherniawsky et al, 2005;Woodgate et al, 2005b;Danielson et al, 2014) and hence influence the variability of transport of nutrient-rich Pacific waters into the Arctic. Storms that move into the Gulf of Alaska tend to shift the climatological Aleutian Low eastward, reducing transport through Bering Strait over daily to weekly time scales, but cause increased transport anomalies over annual time scales (Danielson et al, 2014).…”

“…For example, these storms mediate flow variations in Bering Strait (e.g., Roach et al, 1995;Cherniawsky et al, 2005;Woodgate et al, 2005b;Danielson et al, 2014) and hence influence the variability of transport of nutrient-rich Pacific waters into the Arctic. Storms that move into the Gulf of Alaska tend to shift the climatological Aleutian Low eastward, reducing transport through Bering Strait over daily to weekly time scales, but cause increased transport anomalies over annual time scales (Danielson et al, 2014). The annual transport anomalies are associated with a changing Pacific-Arctic sea-level elevation difference that is caused in part by changes in Ekman suction over the deep North Pacific.…”