scholarly journals Seasonal resonance of diurnal coastal trapped waves in the southern Weddell Sea, Antarctica

2016 ◽  
Author(s):  
Stefanie Semper ◽  
Elin Darelius
Keyword(s):  
Dispersion Curve ◽  
Austral Summer ◽  
Tidal Currents ◽  
Shelf Break ◽  
Weddell Sea ◽  
Background Current ◽  
Trapped Waves ◽  
Coastal Trapped Waves ◽  
Near Resonance ◽  
Temperature Depth

Abstract. The summer enhancement of diurnal tidal currents at the shelf break in the southern Weddell Sea is studied using velocity measurements from 29 moorings during the period 1968 to 2014. Kinetic energy associated with diurnal tidal frequencies is largest at the shelf break and decreases rapidly with distance; its magnitude increases from austral winter to summer by on average 50 %. The summer enhancement is observed in all deployments. The observations are compared to results from an idealised numerical solution of the properties of coastal trapped waves (CTWs) for a given bathymetry, stratification and an along-slope current. The frequency at which the dispersion curve for mode 1 CTWs displays a maximum (i.e. where the group velocity is zero and resonance is possible) is found within or near the diurnal frequency band, and it is sensitive to the stratification in the upper part of the water column and to the background current. The maximum of the dispersion curve is shifted towards higher frequencies, above the diurnal band, for low stratification and a strong background current (i.e. winter-like conditions) and towards lower frequencies for strong upper layer stratification and a weak background current (summer). The seasonal evolution of hydrography and currents in the region is inferred from available mooring data and conductivity-temperature-depth profiles. Near-resonance between CTWs and the diurnal tides during austral summer can explain the observed seasonality in tidal currents.

scholarly journals Seasonal resonance of diurnal coastal trapped waves in the southern Weddell Sea, Antarctica

Ocean Science ◽  
2017 ◽  
Vol 13 (1) ◽  
pp. 77-93 ◽  
Author(s):  
Stefanie Semper ◽  
Elin Darelius
Keyword(s):  
Dispersion Curve ◽  
Austral Summer ◽  
Tidal Energy ◽  
Tidal Currents ◽  
Shelf Break ◽  
Weddell Sea ◽  
Austral Winter ◽  
Background Current ◽  
Trapped Waves ◽  
Coastal Trapped Waves

Abstract. The summer enhancement of diurnal tidal currents at the shelf break in the southern Weddell Sea is studied using velocity measurements from 29 moorings during the period 1968 to 2014. Kinetic energy associated with diurnal tidal frequencies is largest at the shelf break and decreases rapidly with distance from it. The diurnal tidal energy increases from austral winter to summer by, on average, 50 %. The austral summer enhancement is observed in all deployments. The observations are compared to results from an idealised numerical solution of the properties of coastal trapped waves (CTWs) for a given bathymetry, stratification and an along-slope current. The frequency at which the dispersion curve for mode 1 CTWs displays a maximum (i.e. where the group velocity is zero and resonance is possible) is found within or near the diurnal frequency band, and it is sensitive to the stratification in the upper part of the water column and to the background current. The maximum of the dispersion curve is shifted towards higher frequencies, above the diurnal band, for weak stratification and a strong background current (i.e. austral winter-like conditions) and towards lower frequencies for strong upper-layer stratification and a weak background current (austral summer). The seasonal evolution of hydrography and currents in the region is inferred from available mooring data and conductivity–temperature–depth profiles. Near-resonance of diurnal tidal CTWs during austral summer can explain the observed seasonality in tidal currents.

Intensified Diurnal Tides along the Oregon Coast

2014 ◽  
Vol 44 (7) ◽  
pp. 1689-1703 ◽  
Author(s):  
J. J. Osborne ◽  
A. L. Kurapov ◽  
G. D. Egbert ◽  
P. M. Kosro
Keyword(s):  
Ocean Circulation ◽  
Circulation Model ◽  
Tidal Currents ◽  
Current Data ◽  
Hf Radar ◽  
Water Model ◽  
Trapped Waves ◽  
Diurnal Variability ◽  
Coastal Trapped Waves ◽  
Diurnal Tides

Abstract Intensified diurnal tides are found along portions of the Oregon shelf (U.S. West Coast) based on analyses of high-frequency (HF) radar surface current data and outputs of a 1-km resolution ocean circulation model. The K1 tidal currents with magnitudes near 0.07 m s−1 over a wider part of the shelf (Heceta Bank complex; 44°–44.5°N), previously predicted by Erofeeva et al., are confirmed here by newly available HF radar data. Intensified diurnal tides are also found along the narrow shelf south of Heceta Bank. In the close vicinity of Cape Blanco (42.8°N), diurnal tidal currents (K1 and O1 constituents combined) may reach 0.3 m s−1. Appreciable differences in diurnal tide intensity are found depending on whether the model is forced with tides and winds (TW) or only tides. Also, diurnal variability in wind forcing is found to affect diurnal surface velocities. For the case forced by tides alone, results strongly depend on whether the model ocean is stratified [tides only, stratified (TOS)] or not [tides only, no stratification (TONS)]. In case TONS, coastal-trapped waves at diurnal frequencies do not occur over the narrow shelf south of 43.5°N, consistent with the dispersion analysis of a linear shallow-water model. However, in case TOS, diurnal tides are intensified in that area, associated with the presence of coastal-trapped waves. Case TW produces the strongest modeled diurnal tidal motions over the entire Oregon shelf, partially due to cross-shore tidal displacement (advection) of alongshore subinertial currents. At Cape Blanco, diurnal tidal variability dominates the modeled relative vorticity spectrum, suggesting that tides may influence the separation of the alongshore coastal jet at that location.

Diurnal tidal currents attributed to free baroclinic coastal-trapped waves on the Pacific shelf off the southeastern coast of Hokkaido, Japan

2018 ◽  
Vol 158 ◽  
pp. 45-56 ◽  
Author(s):  
Hiroshi Kuroda ◽  
Akira Kusaka ◽  
Yutaka Isoda ◽  
Satoshi Honda ◽  
Sayaka Ito ◽  
...  
Keyword(s):  
Tidal Currents ◽  
Trapped Waves ◽  
Southeastern Coast ◽  
Coastal Trapped Waves ◽  
The Pacific

Effect of coastal-trapped waves on the synoptic variations of the Yellow Sea Warm Current during winter

2018 ◽  
Vol 167 ◽  
pp. 14-31 ◽  
Author(s):  
Yang Ding ◽  
Xianwen Bao ◽  
Zhigang Yao ◽  
Dehai Song ◽  
Jun Song ◽  
...  
Keyword(s):  
Yellow Sea ◽  
The Yellow Sea ◽  
Trapped Waves ◽  
Yellow Sea Warm Current ◽  
Warm Current ◽  
Coastal Trapped Waves
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