Tidally induced mean flow over bathymetric features: a contemporary challenge for high-resolution wide-area models

Polton, Jeff A.

doi:10.1080/03091929.2014.952726

Cited by 21 publications

(18 citation statements)

References 7 publications

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“…With the described resolution and parameterizations, the model resolves tidal mixing on the shelf and the formation of tidal fronts (for different aspects of resolution problems, see also Polton 2015 andHolt et al 2017). As demonstrated by Graham et al (2018a), the simulated positions of tidal fronts are close in models with~7 and~1.5-km resolution.…”

Section: What the Model Can And Cannot Resolvementioning

confidence: 85%

Interactions between barotropic tides and mesoscale processes in deep ocean and shelf regions

Stanev

Ricker

2020

Ocean Dynamics

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The interactions between barotropic tides and mesoscale processes were studied using the results of a numerical model in which tidal forcing was turned on and off. The research area covered part of the East Atlantic Ocean, a steep continental slope, and the European Northwest Shelf. Tides affected the baroclinic fields at much smaller spatial scales than the barotropic tidal scales. Changes in the horizontal patterns of the M 2 and M 4 tidal constituents provided information about the two-way interactions between barotropic tides and mesoscale processes. The interaction between the atmosphere and ocean measured by the work done by wind was also affected by the barotropic tidal forcing. Tidal forcing intensified the transient processes and resulted in a substantial transformation of the wave number spectra in the transition areas from the deep ocean to the shelf. Tides flattened the sea-surface height spectra down to~k −2.5 power law, thus reflecting the large contribution of the processes in the high-frequency range compared to quasi-geostrophic motion. The spectra along sections parallel or normal to the continental slope differ from each other, which indicates that mesoscale turbulence was not isotropic. An analysis of the vorticity spectra showed that the flattening was mostly due to internal tides. Compared with the deep ocean, no substantial scale selectivity was observed on the shelf area. Particle tracking showed that the lengths of the Lagrangian trajectories increased by approximately 40% if the barotropic tidal forcing was activated, which contributed to changed mixing properties. The ratio between the horizontal and vertical scales of motion varied regionally depending on whether barotropic tidal forcing was included. The overall conclusion is that the barotropic tides affect substantially the diapycnal mixing.

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Section: What the Model Can And Cannot Resolvementioning

confidence: 85%

Interactions between barotropic tides and mesoscale processes in deep ocean and shelf regions

Stanev

Ricker

2020

Ocean Dynamics

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“…The main current forcing in summer is the tide. The mean current in summer (2.8 cm/s to the northwest along the slope Figure b) can be interpreted as a residual current due to the tide rectification, a superposition of Coriolis and frictional processes over steep topography (Padman et al, ; Polton, ). In autumn/winter, the ellipse of variance of the current data is larger than the ellipse of variance from AOTIM‐5 (std along the main axis 9.7 cm/s in the current data versus 9.1 cm/s in the AOTIM‐5 model; along the secondary axis: 8.4 cm/s versus 6.4 cm/s respectively, Figure a).…”

Section: Statistics and Spectral Content Of The In Situ Velocitiesmentioning

confidence: 99%

The Yermak Pass Branch: A Major Pathway for the Atlantic Water North of Svalbard?

et al. 2017

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An upward‐looking Acoustic Doppler Current Profiler deployed from July 2007 to September 2008 in the Yermak Pass, north of Svalbard, gathered velocity data from 570 m up to 90 m at a location covered by sea ice 10 months out of 12. Barotropic diurnal and semidiurnal tides are the dominant signals in the velocity (more than 70% of the velocity variance). In winter, baroclinic eddies at periods between 5 and 15 days and pulses of 1–2 month periodicity are observed in the Atlantic Water layer and are associated with a shoaling of the pycnocline. Mercator‐Ocean global operational model with daily and 1/12° spatial resolution is shown to have skills in representing low‐frequency velocity variations (>1 month) in the West Spitsbergen Current and in the Yermak Pass. Model outputs suggest that the Yermak Pass Branch has had a robust winter pattern over the last 10 years, carrying on average 31% of the Atlantic Water volume transport of the West Spitsbergen Current (36% in autumn/winter). However, those figures have to be considered with caution as the model neither simulates tides nor fully resolves eddies and ignores residual mean currents that could be significant.

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“…Irregularities in the velocity and bottom shear stresses over a varying topographic relief generate vorticity and vertical motions that result in ageostrophic circulations and either geostrophic upwelling or downwelling of isopycnals. The efficiency of energy transfer from tidal currents to the rectified circulation increases when the characteristic length scales of depth variation match the range of horizontal tidal movement [ Zimmerman , ; Loder , ; Robinson , ] (see also contemporary review Polton []). Kowalik and Proshutinsky [, ] estimated residual currents of 0.08–0.1 m s −1 in some regions of the Arctic Ocean.…”

Section: Effects Of Tides In the Ao: Observations And Hypothesesmentioning

confidence: 99%

The effects of tides on the water mass mixing and sea ice in the Arctic Ocean

et al. 2015

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In this study, we use a novel pan-Arctic sea ice-ocean coupled model to examine the effects of tides on sea ice and the mixing of water masses. Two 30 year simulations were performed: one with explicitly resolved tides and the other without any tidal dynamics. We find that the tides are responsible for a $15% reduction in the volume of sea ice during the last decade and a redistribution of salinity, with surface salinity in the case with tides being on average $1.0-1.8 practical salinity units (PSU) higher than without tides. The ice volume trend in the two simulations also differs: 22.09 3 10 3 km 3 /decade without tides and 22.49 3 10 3 km 3 /decade with tides, the latter being closer to the trend of 22.58 3 10 3 km 3 /decade in the PIOMAS model, which assimilates SST and ice concentration. The three following mechanisms of tidal interaction appear to be significant: (a) strong shear stresses generated by the baroclinic clockwise rotating component of tidal currents in the interior waters; (b) thicker subsurface ice-ocean and bottom boundary layers; and (c) intensification of quasi-steady vertical motions of isopycnals (by $50%) through enhanced bottom Ekman pumping and stretching of relative vorticity over rough bottom topography. The combination of these effects leads to entrainment of warm Atlantic Waters into the colder and fresher surface waters, supporting the melting of the overlying ice.

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Tidally induced mean flow over bathymetric features: a contemporary challenge for high-resolution wide-area models

Cited by 21 publications

References 7 publications

Interactions between barotropic tides and mesoscale processes in deep ocean and shelf regions

Interactions between barotropic tides and mesoscale processes in deep ocean and shelf regions

The Yermak Pass Branch: A Major Pathway for the Atlantic Water North of Svalbard?

The effects of tides on the water mass mixing and sea ice in the Arctic Ocean

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