A regional tidal/subtidal circulation model of the southeastern Bering Sea: development, sensitivity analyses and hindcasting

Abstract

A regional eddy-resolving primitive equation circulation model was used to simulate circulation on the southeastern Bering Sea (SEBS) shelf and basin. This model resolves the dominant observed mean currents, eddies and meanders in the region, and simultaneously includes both tidal and subtidal dynamics. Circulation, temperature and salinity fields for years 1995 and 1997 were hindcast, using daily wind and buoyancy flux estimates, and tidal forcing derived from a global model. This paper describes the development of the regional model, a comparison of model results with available Eulerian and Lagrangian data, a comparison of results between the two hindcast years, and a sensitivity analysis. Based on these hindcasts and sensitivity analyses, we suggest the following: 1) The Bering Slope Current (BSC) is a primary source of large (~100 km diameter) eddies in the SEBS basin. Smaller meanders are also formed along the 100 m isobath on the southeastern shelf, and along the 200 m isobath near the shelf break. 2) There is substantial interannual variability in the statistics of eddies within the basin, driven by variability in the strength of the ANSC. 3) The mean flow on the shelf is not strongly sensitive to changes in the imposed strength of the ANSC; rather, it is strongly sensitive to the local wind forcing. 4) Vertical mixing in the SEBS is strongly affected by both tidal and subtidal dynamics. Strongest mixing in the SEBS may in fact occur between the 100 and 400 m isobaths, near the Pribilof Islands, and in Unimak Pass.

Sea Ice Response to Atmospheric and Oceanic Forcing in the Bering Sea

“…For example, tidal forcing induces a strong clockwise circulation around the Pribilof Islands (Fig. 7a), which is qualitatively in agreement with Kowalik and Stabeno (1999) and Hermann et al (2002). Without tidal forcing, such a clockwise circulation is not simulated (Fig.…”

Processes driving sea ice variability in the Bering Sea in an eddying ocean/sea ice model: anomalies from the mean seasonal cycle

“…This may also help account for the simulated agreement with ice cover observations despite tidal forcing not being included in this simulation as a driving process for mixing and current rectification in the shallow waters of the Bering Sea (Hermann et al 2002;Zhang et al 2010).…”

“…It does not include tidal forcing. Earlier numerical studies have found that tidal forcing increases vertical mixing and the kinetic energy of ocean currents in the southeastern Bering Sea (Hermann et al 2002), as well as modifying sea ice thickness in the central-eastern Bering Sea (Zhang et al 2010). Tidal forcing might also reduce the mean flow due to the horizontal gradient of tidal mixing (Auad and Miller 2008).…”

Regular occurrence of Thysanoessa inspinata (Crustacea: Euphausiacea) in the Gulf of Alaska

“…Gorbatenko (2001) recorded T. inspinata in 1998 from the north-western Bering Sea. Apparently, the species has been transported by the Aleutian North Slope Current and the Bering Slope Current, which originates in the eastern Aleutians (Stabeno et al, 1995;Hermann et al, 2002). Nemoto & Kamada (1980) and Taki & Kotani (1994) recorded Thysanoessa inspinata in cold waters underlying the Kuroshio but not in the warmer northward £owing Kuroshio.…”