Modeling effects of tidal and wave mixing on circulation and thermohaline structures in the Bering Sea: Process studies

Abstract

[1] Ocean circulation and the tidal current in the Bering Sea are simulated simultaneously using a coupled ice-ocean model (CIOM) with tidal and parameterized wave mixing to investigate several important physical processes. The simulated circulation pattern in the deep basin is relatively stable, cyclonic, and has little seasonal change. The Bering Slope Current is estimated at 5 Sv and the Kamchatka Current at 20 Sv. The modeled volume transports through the Aleutian passes compared reasonably well with observations. It is confirmed that subtidal clockwise circulation around St. George and St. Paul islands are driven by tidal rectification. The simulation results show that wind-wave mixing and tidal stirring are the main factors controlling the formation of the upper and the bottom mixed layers, respectively. The mechanism of thermocline and the cold pool (summer minimum-temperature water) formation in the middle shelf are investigated in depth. The CIOM reproduces the cold winter-convective water in the middle shelf that forms the bottom cold pool, which persists throughout the summer until sea surface cooling and strong wind mixing in fall, leading to an unstable vertical water column and eventually to vertically well-mixed water in the winter. Sensitivity experiments show that tidal and wind-wave mixing are two important factors in accurately estimating the volume of the cold pool, which is the ideal marine habitat for cold water species.Citation: Hu, H., and J. Wang (2010), Modeling effects of tidal and wave mixing on circulation and thermohaline structures in the

Abrupt Climate Changes and Emerging Ice-Ocean Processes in the Pacific Arctic Region and the Bering Sea

“…For a detailed description of development of the CIOM, readers should refer to Yao et al (2000) and Wang et al (2002Wang et al ( , 2010, which was applied to the pan-Arctic Ocean (Wang et al , 2005aWu et al 2004;Long et al 2012), Chukchi-Beaufort seas , and the Bering Sea (Wang et al 2009b;Hu and Wang 2010;Hu et al 2011). The ocean model used is the Princeton Ocean Model (POM) (Blumberg and Mellor 1987), and the ice model used is a full thermodynamic and dynamics model (Hibler 1979(Hibler , 1980) that prognostically simulates sea-ice thickness, sea ice concentration (SIC), ice edge, ice velocity, and heat and salt flux through sea ice into the ocean.…”

“…The +DA not only drives sea ice from the western/Pacific Arctic to the eastern/ Atlantic Arctic via accelerating the TDS, but also promotes northward flow of warm Pacific water that contributes above-average heat transport from the Pacific, accelerating the drastic thinning of sea ice (Steele et al 2004;Shimada et al 2006;Zhang et al 2008a) (Shimada et al 2006;Hu and Wang 2010) at the subsurface, which enhances the melting in the following spring and summer via ice/ ocean albedo feedback, which further amplifies the ice/ocean albedo process, leading to an early melting.…”

“…The cold water was even observed in late September and early October (Kinder and Schumacher 1981). Hu and Wang (2010) investigate the seasonal change of the cold pool using the CIOM, and found that the largest vertical temperature difference, surface minus bottom, is >7 °C in the middle domain, suggesting that the cool pool survives the summer. The cold pool extends from the Gulf of Anadyr in the west with a temperature of <−1.0 °C (Hufford and Husby 1972) to a variable eastern boundary over the southeastern shelf with a temperature of 2 °C (Maeda et al 1967).…”

“…The CIOM, driven with daily atmospheric forcing, was used to calculate instantaneous cold pool volume for years 1990-2008 according to the formula of Hu and Wang (2010) Volume t x y z…”

“…The ocean circulation pattern is complicated. The Alaskan Stream (AS) mainly flows along the Aleutian Peninsula and provides some of its water via Aleutian passes to the Bering Slope Current (BSC) and to the Aleutian North Slope Current (ANSC; Stabeno et al 1999;Hu and Wang 2010). The BSC extends into two coastal currents: the Anadyr Current (AC), which flows along eastern Siberia into the Chukchi Sea through the western side of the Bering Strait, and the East Kamchatka Current (EKC), which flows southwestward along the Koryak and Kamchatka peninsula.…”