Tidal currents in the St. Lawrence Island region

Abstract

[1] Vertical and spatial variability of tidal currents in the northern part of the Bering Sea near St. Lawrence Island were examined using observations made at 17 new and historical current meter mooring locations. The semidiurnal currents dominate over the diurnal currents. Semidiurnal currents exhibit a seasonal modulation with currents being somewhat stronger during the summer and fall when the density structure displays two-layer stratification. Diurnal currents exhibit a weak semiannual modulation. Examination of the vertical structure of tidal currents shows that maximum semidiurnal currents are observed in the upper or middle layers down to a depth of about 20 m, and below this depth the energy of the semidiurnal currents decreases rapidly. However, the energy of diurnal band currents remains almost constant with depth, decreasing only in close proximity to the bottom. Rotary spectral analysis applied to the records shows further differences: the M 2 clockwise (CW) component of rotation dominates in the upper and middle water column but the counterclockwise component (CCW) dominates near the bottom. Interpretation of these observed results points to the different bottom boundary layers (BBL) for the CW and CCW motions in addition to the role of density stratification in organizing the BBL. We compare results of a vertically averaged two-dimensional model to the observationally derived tidal ellipse parameters and show that the barotropic formulation provides a first-order description of the tidal regime within the domain.

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

“…The inclination and phase of K 1 progress from the surface to the bottom in an opposite sense to the change of the M 2 parameters. The model simulated vertical structures are qualitatively consistent with the measurements [see Danielson and Kowalik , 2005, Figure 4], except some errors in the inclination and phase, which may be due to the model resolution and depth smoothing. These errors should be significantly reduced if the mentioned error‐causing factors are taken care.…”

“…The yearlong ADCP data at station F 8 were analyzed by Danielson and Kowalik [2005, Figure 4]. Semidiurnal currents (Figure 7) dominate (approximately 4 times) over diurnal currents.…”

Circulation on the central Bering Sea shelf, July 2008 to July 2010

“…The shallow and broad central Bering Sea shelf is the region south of St. Lawrence Island and north of Nunivak Island (Figure 1). It experiences cooling, ice formation and brine production in winter [ Drucker et al , 2003], solar heating in summer, strong winds in fall, winter and early spring [ Brower et al , 1988; Bond et al , 1994], large river discharges in summer [ Brabets et al , 2000], and strong tidal currents [ Pearson et al , 1981; Mofjeld , 1984; Kowalik , 1999; Danielson and Kowalik , 2005]. Thermohaline characteristics exhibit large inter‐annual variability [ Takenouti and Ohtani , 1974; Coachman et al , 1975; Danielson et al , 2011], but the causes of these variations are not fully understood.…”

A new high‐resolution unstructured grid finite volume Arctic Ocean model (AO‐FVCOM): An application for tidal studies

“…Running the model with summer stratification seems to have little influence on the amplitudes of tidal elevation but significant influence on orientation and phases of the tidal currents. Danielson and Kowalik [2005] found from current measurements in the northern region of the Bering Sea near St. Lawrence Island that the tidal currents show a significant seasonal modulation. Our tidal data analysis (not shown) also shows that tidal current ellipse parameters at the same location and measurement depth varied significantly with sampling times, which is consistent with the work by Danielson and Kowalik [2005].…”

“… Danielson and Kowalik [2005] found from current measurements in the northern region of the Bering Sea near St. Lawrence Island that the tidal currents show a significant seasonal modulation. Our tidal data analysis (not shown) also shows that tidal current ellipse parameters at the same location and measurement depth varied significantly with sampling times, which is consistent with the work by Danielson and Kowalik [2005]. Prinsenberg [1988] detected from yearlong current meter records that the annual ice cover significantly affected the tidal currents and elevation in Hudson Bay: both semidiurnal currents and elevations were reduced by ∼10% and had ∼20 min phase leading in winter in comparison to summer.…”