Reconstruction and analysis of the Chukchi Sea circulation in 1990–1991

Abstract

[1] The Chukchi Sea (CS) circulation reconstructed for September 1990 to October 1991 from sea ice and ocean data is presented and analyzed. The core of the observational data used in this study comprises the records from 12 moorings deployed in 1990 and 1991 in U.S. and Russian waters and two hydrographic surveys conducted in the region in the fall of 1990 and 1991. The observations are processed by a two-step data assimilation procedure involving the Pan-Arctic Ice-Ocean Modeling and Assimilation System (employing a nudging algorithm for sea ice data assimilation) and the Semiimplicit Ocean Model [utilizing a conventional four-dimensional variational (4D-var) assimilation technique]. The reconstructed CS circulation is studied to identify pathways and assess residence times of Pacific water in the region; quantify the balances of volume, freshwater, and heat content; and determine the leading dynamical factors configuring the CS circulation. It is found that in 1990-1991 (high AO index and a cyclonic circulation regime) Pacific water transiting the CS toward the Canada basin followed two major pathways, namely via Herald Canyon (Herald branch of circulation, 0.23 Sv) and between Herald Shoal and Cape Lisburne (central branch of circulation and Alaskan Coastal Current, 0.32 Sv). The annual mean flow through Long Strait was negligible (0.01 Sv). Typical residence time of Pacific water in the region varied between 150 days for waters entering the CS in September and 270 days for waters entering in February/March. Momentum balance analysis reveals that geostrophic balance between barotropic pressure gradient and Coriolis force dominated for most of the year. Baroclinic effects were important for circulation only in the regions with large horizontal salinity gradients associated with the fresh Alaskan and Siberian coastal currents and the Cape Lisburne and Great Siberian polynyas. In the polynyas, the baroclinic effects were due to strong salinification and convection processes associated with sea ice formation.

Synoptic forcing of wave states in the southeast Chukchi Sea, Alaska, at nearshore locations

“…A possible explanation for this would be wave refraction. There is a strong current prominent in the southeast Chukchi Sea region, traveling eastward and northward (Coachman and Tripp 1970;Overland and Roach 1987;Woodgate et al 2005;Panteleev et al 2010). At Station 2009S, this current is found to travel eastward and northward, which corresponds with the westerly and southwesterly wave direction.…”

Two Configurations of the Western Arctic Shelfbreak Current in Summer

“…However, uncertainties remain regarding the relative timing of the seasonal transition and the potential interaction of the summer and winter waters within the individual branches. Synoptically, as well as seasonally, the partitioning of transport varies between the three branches as shown by numerical models (e.g., Winsor and Chapman 2004;Panteleev et al 2010).…”

The Barents and Chukchi Seas: Comparison of two Arctic shelf ecosystems

“…One branch flows east of Hanna shoal and continues to Barrow Canyon, one is west of Herald Shoal through Herald Canyon, and other is between the shoals via what is called the Central Channel ( Fig. 3; Panteleev et al, 2010;Spall, 2007;Weingartner et al, 2005;Woodgate et al, 2005c). Although the volume flows through these different branches are comparable, their seasonal variability is somewhat different (Woodgate et al, 2005c).…”

“…The southern Chukchi Sea is strongly influenced by waters entering through the Bering Strait (Coachman et al, 1975;Panteleev et al, 2010;Spall, 2007;Woodgate et al, 2005c). The Bering Strait volume transport averages about 0.8 Sv northwards over the year (Roach et al, 1995;Woodgate et al, 2006), being strongest in summer and weakest in winter.…”