Wind Effects on Flow Patterns and Net Fluxes in Density‐Driven High‐Latitude Channel Flow. Issue 1 (16th January 2018)

• Record Type: Journal Article
• Authors: Huntley, Helga S.; Ryan, Patricia
• Is Part Of: Journal of geophysical research. Volume 123:Issue 1(2018)
• Page Start: 305
• Page End: 323
• Publication Date: 2018-01-16
• Subjects: channel flow -- wind stress -- density currents -- throughflow -- Ekman number -- Nares Strait; Oceanography -- Periodicals; 551.4605
• DOI: 10.1002/2017JC012748
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: A semianalytic two‐dimensional model is used to analyze the interplay between the different forces acting on density‐driven flow in high‐latitude channels. In particular, the balance between wind stress, viscous forces, baroclinicity, and sea surface slope adjustments under specified flux conditions is examined. Weak winds are found not to change flow patterns appreciably, with minimal (<7%) adjustments to horizontal velocity maxima. In low‐viscosity regimes, strong winds change the flow significantly, especially at the surface, by either strengthening the dual‐jet pattern, established without wind, by a factor of 2–3 or initiating return flow at the surface. A nonzero flux does not result in the addition of a uniform velocity throughout the channel cross section, but modifies both along‐channel and cross‐channel velocities to become more symmetric, dominated by a down‐channel jet centered in the domain and counter‐clockwise lateral flow. We also consider formulations of the model that allow adjustments of the net flux in response to the wind. Flow patterns change, beyond uniform intensification or weakening, only for strong winds and high Ekman number. Comparisons of the model results to observational data collected in Nares Strait in the Canadian Archipelago in the summer of 2007 show rough agreement, but the model misses the upstream surface jet on the east side of the strait and propagates bathymetric effects too strongly in the vertical for this moderately high eddy viscosity. Nonetheless, the broad strokes of the observed high‐latitude flow are reproduced. Plain Language Summary: A simplified model was used to study how wind can change the flow of water through a channel. What happens depends on the specific configuration. Here, the focus was on conditions typical for polar regions. In most cases, the strength of the viscosity (which controls dissipation) plays a bigger role than the strength of the wind stress. Wind may also change how much net water flows through the channel. Accounting for this flux was found to be important for describing the flow structure correctly. For example, flow with a large flux is generally more symmetric and centered in the channel, whereas less throughflow supports a jet that is displaced to the left looking up‐channel. A comparison to observations in an Arctic strait showed that the model performed reasonably well. Key Points: Viscous forces generally dominate wind effects; strong up‐channel winds cause surface return flow Nonzero net flux alters the flow patterns, displacing velocity peaks The main flow features observed in Nares Strait in summer 2007 are captured by the model