Circulation and Thermohaline Variability of the Hanna Shoal Region on the Northeastern Chukchi Sea Shelf

Abstract

We analyzed velocity and hydrographic data from 23 moorings in the northeast Chukchi Sea from 2011 to 2014. In most years the eastern side of Hanna Shoal was strongly stratified year‐round, while weakly stratified regions prevailed on the shelf south and west of the Shoal. Stratification differences cause differential vertical mixing rates, which in conjunction with advection of different bottom water properties resulted in seasonally varying along‐isobath density gradients. In agreement with numerical models, we find that bottom waters flow anticyclonically around the Shoal. Whereas most of the shelf responded barotropically to wind‐forcing, there was a strong baroclinic component to the flow field northeast of Hanna Shoal, resulting in no net vertically integrated transport on average. In contrast there is a net eastward transport from west of the Shoal, which implies convergence north of the Shoal. Convergence and along‐isobath density gradients may foster cross‐shelf exchange north of Hanna Shoal. Modal analyses indicate that the shelf south of the Shoal and Barrow Canyon responded coherently to local and remote winds, whereas the wind‐current response around Hanna Shoal was less coherent. Barotropic topographic waves, of ~3‐day period, were generated episodically northeast of the Shoal and propagate clockwise around Hanna Shoal, but are blocked from entering Barrow Canyon and are possibly scattered by the horizontally sheared flow and converging isobaths on the western side of the Shoal. Analysis of water properties on the western side of Hanna Shoal suggests that these include contributions from the western and southern portions of the Chukchi Sea.

Mean and Seasonal Circulation of the Eastern Chukchi Sea From Moored Timeseries in 2013–2014

“…This is consistent with the results of Fang et al. (2020).…”

“…However, three of the mooring records (Cj, CT, and FM1) were short by 1-3 months. We note that some, but not all, of the moorings analyzed in this study are the same as those discussed in Fang et al (2020).…”

“…Fang et al. (2020) analyzed data from a set of 23 moorings around Hanna Shoal, deployed between 2011 and 2014, and noted a signal of sudden sustained reduction in temperature to near‐freezing at the start of winter, and a gradual rebound during the summer months.…”

Oceanic Routing of Wind-Sourced Energy Along the Arctic Continental Shelves

“…Local winds over the Pacific-sector Arctic continental shelves can account for 30−50% of the synoptic scale variability in the coastal region, while including time-lagged remote winds can increase the fraction of variance explained by 10−20% (Danielson et al, 2014;Weingartner et al, 2017;Fang et al, 2020). Using a 1-layer (two-dimensional barotropic) model of the Pacific Arctic forced only by wind, Danielson et al (2014) showed that including the combined effects of locally generated storm surges and their associated propagating shelf waves provides a skilfull reproduction of observed current variations in Bering Strait (r 2 = 0.79 in winter months) for synoptic-band current fluctuations.…”

A Multifaceted Approach to Advance Oil Spill Modeling and Physical Oceanographic Research at the United States Bureau of Ocean Energy Management

“…Circulation patterns showed a general clockwise flow around the north and east sides of Hanna Shoal, as well as on the west flank. Unlike the rest of the shelf, observations east of Hanna Shoal indicated the circulation and hydrography maintained a year-round stratification with westward or northwestward flow in the upper layer and southward flow along the bottom [134].…”