Abstract
AbstractThe southward freshwater flux through Nares Strait is an important component of the Arctic's freshwater budget. On short time scales, flow through the strait is dominated by the tides, and tidal dynamics may be important for the magnitude of the freshwater flux over longer periods. Here we build upon our existing knowledge of the tides in the region by exploring their propagation and vertical structure using data from four bottom‐mounted Acoustic Doppler Current Profilers deployed in Nares Strait between 2003 and 2006. We observe that propagating barotropic semidiurnal tidal waves interact to create a standing wave pattern, explaining the abnormally large tidal amplitudes that are observed in this region. In the along‐strait direction, semidiurnal tidal currents exhibit strong variations with depth. In contrast, the diurnal tides propagate northward through the strait as progressive waves, and the tidal currents are broadly depth invariant. Proximity of Nares Strait to the semidiurnal critical latitude and the topographical restriction imposed by the steep side wall of Ellesmere Island are primary drivers behind the observed vertical variability. In the upper part of the water column, baroclinic activity increases the tidal current amplitude by up to 25%. In the across‐strait direction, a two‐layer structure exists in both the diurnal and semidiurnal tidal flow, with a phase lag of approximately a quarter of a tidal cycle across the strait for the semidiurnal tide. Our results suggest that strong vertical motion exists against the side walls of Nares Strait, as the across‐strait flow interacts with the steeply sloping bathymetry.
Highlights
Nares Strait, a narrow channel to the west of Greenland, forms one of the two major conduits within the Canadian Arctic Archipelago (CAA) through which freshened seawater and sea ice flow from the Arctic Ocean to the North Atlantic (Figure 1a)
An upper water column maximum in the amplitude of both the diurnal and semidiurnal tides is seen across Nares Strait, this feature is clearer in the semidiurnal tides
This result has important implications when using tidal models in studies that explore, for example, the flow dynamics through Nares Strait, or the wider rapid environmental change that is occurring throughout the Arctic Ocean
Summary
Nares Strait, a narrow channel to the west of Greenland, forms one of the two major conduits within the Canadian Arctic Archipelago (CAA) through which freshened seawater and sea ice flow from the Arctic Ocean to the North Atlantic (Figure 1a). In spite of this recent progress, we still know little about the dynamic processes which act to limit the volume and freshwater fluxes through the region, and this is hampering our ability to understand to what extent they may be affected by the rapidly changing conditions throughout the Arctic. Our goal is to build upon the existing depth-averaged analysis of tides by Münchow and Melling (2008) by documenting the vertical structure of the flow through Nares Strait on tidal time scales. By developing a fuller understanding of the nature of the tides in the region, we are providing a basis from which future studies can explore the relevant dynamics in more detail, and begin to understand the wider role of the tides in the climatically important freshwater flux through Nares Strait
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