Variability of Kuroshio velocity assessed from the sea-level difference between Naze and Nishinoomote

1988 ◽  
Vol 44 (6) ◽  
pp. 293-304 ◽  
Author(s):  
Masaki Kawabe
Keyword(s):  
Sea Level ◽  
Level Difference ◽  
Sea Level Difference

Atlantic to Mediterranean Sea Level Difference Driven by Winds near Gibraltar Strait

2007 ◽  
Vol 37 (2) ◽  
pp. 359-376 ◽  
Author(s):  
Dimitris Menemenlis ◽  
Ichiro Fukumori ◽  
Tong Lee
Keyword(s):  
Mediterranean Sea ◽  
Sea Level ◽  
Wind Stress ◽  
Coastal Current ◽  
Alboran Sea ◽  
Mean Sea Level ◽  
Level Difference ◽  
Gibraltar Strait ◽  
Sea Level Difference ◽  
Alborán Sea

Abstract Observations and numerical simulations show that winds near Gibraltar Strait cause an Atlantic Ocean to Mediterranean Sea sea level difference of 20 cm peak to peak with a 3-cm standard deviation for periods of days to years. Theoretical arguments and numerical experiments establish that this wind-driven sea level difference is caused in part by storm surges due to alongshore winds near the North African coastline on the Atlantic side of Gibraltar. The fraction of the Moroccan coastal current offshore of the 284-m isobath is deflected across Gibraltar Strait, west of Camarinal Sill, resulting in a geostrophic surface pressure gradient that contributes to a sea level difference at the stationary limit. The sea level difference is also caused in part by the along-strait wind setup, with a contribution proportional to the along-strait wind stress and to the length of Gibraltar Strait and adjoining regions and inversely proportional to its depth. In the 20–360-day band, average transfer coefficients between the Atlantic–Alboran sea level difference and surface wind stress at 36°N, 6.5°W, estimated from barometrically corrected Ocean Topography Experiment (TOPEX)/Poseidon data and NCEP–NCAR reanalysis data, are 0.10 ± 0.04 m Pa−1 with 1 ± 5-day lag and 0.19 ± 0.08 m Pa−1 with 5 ± 4-day lag for the zonal and meridional wind stresses, respectively. This transfer function is consistent with equivalent estimates derived from a 1992–2003 high-resolution barotropic simulation forced by the NCEP–NCAR wind stress. The barotropic simulation explains 29% of the observed Atlantic–Alboran sea level difference in the 20–360-day band. In turn, the Alboran and Mediterranean mean sea level time series are highly correlated, ρ = 0.7 in the observations and ρ = 0.8 in the barotropic simulation, hence providing a pathway for winds near Gibraltar Strait to affect the mean sea level of the entire Mediterranean.

scholarly journals On the relation between Meridional Overturning Circulation and sea-level gradients in the Atlantic

2012 ◽  
Vol 3 (1) ◽  
pp. 325-356 ◽  
Author(s):  
H. Kienert ◽  
S. Rahmstorf
Keyword(s):  
Sea Level ◽  
Co2 Concentration ◽  
Meridional Overturning Circulation ◽  
Overturning Circulation ◽  
Simultaneous Application ◽  
Level Difference ◽  
Ocean Winds ◽  
Meridional Overturning ◽  
The Individual ◽  
Sea Level Difference

Abstract. On the basis of model simulations, we examine what information on changes in the strength of the Atlantic Meridional Overturning Circulation (AMOC) can be extracted from associated changes in sea surface height (SSH), specifically from a broad Atlantic north-south gradient as has been suggested previously in the literature. Since a relation between AMOC and SSH changes can only be used as an AMOC diagnostic if it is valid independently of the specific forcing, we consider three different forcing types: increase of CO2 concentration, freshwater fluxes to the northern convection sites and the modification of Southern Ocean winds. We concentrate on a timescale of 100 yr. We find approximately linear and numerically similar relations between a sea-level difference within the Atlantic and the AMOC for freshwater as well as wind forcing. However, the relation is more complex in response to atmospheric CO2 increase, which precludes this sea-level difference as an AMOC diagnostic under climate change. Finally, we show qualitatively to what extent changes in SSH and AMOC strength that are caused by simultaneous application of different forcings correspond to the sum of the changes due to the individual forcings, a potential prerequisite for more complex SSH-based AMOC diagnostics.

scholarly journals On the relation between Meridional Overturning Circulation and sea-level gradients in the Atlantic

2012 ◽  
Vol 3 (2) ◽  
pp. 109-120 ◽  
Author(s):  
H. Kienert ◽  
S. Rahmstorf
Keyword(s):  
Sea Level ◽  
Co2 Concentration ◽  
Meridional Overturning Circulation ◽  
Overturning Circulation ◽  
Simultaneous Application ◽  
Level Difference ◽  
Ocean Winds ◽  
Meridional Overturning ◽  
The Individual ◽  
Sea Level Difference

Abstract. On the basis of model simulations, we examine what information on changes in the strength of the Atlantic Meridional Overturning Circulation (AMOC) can be extracted from associated changes in sea surface height (SSH), specifically from a broad Atlantic north–south gradient as has been suggested previously in the literature. Since a relation between AMOC and SSH changes can only be used as an AMOC diagnostic if it is valid independently of the specific forcing, we consider three different forcing types: increase of CO2 concentration, freshwater fluxes to the northern convection sites and the modification of Southern Ocean winds. We concentrate on a timescale of 100 yr. We find approximately linear and numerically similar relations between a sea-level difference within the Atlantic and the AMOC for freshwater as well as wind forcing. However, the relation is more complex in response to atmospheric CO2 increase, which precludes this sea-level difference as an AMOC diagnostic under climate change. Finally, we show qualitatively to what extent changes in SSH and AMOC strength, which are caused by simultaneous application of different forcings, correspond to the sum of the changes due to the individual forcings, a potential prerequisite for more complex SSH-based AMOC diagnostics.

Relation between mean sea level, current and wind stress on the east coast of Australia

1975 ◽  
Vol 26 (3) ◽  
pp. 389 ◽  
Author(s):  
BV Hamon ◽  
JS Godfrey ◽  
MA Greig
Keyword(s):  
Sea Level ◽  
Wind Stress ◽  
Average Rate ◽  
Clear Correlation ◽  
Similar Data ◽  
Shelf Edge ◽  
Longshore Current ◽  
Mean Sea Level ◽  
Level Difference ◽  
Sea Level Difference

Five-day mean sea level differences between Evans Head (29� 07'S.) and Coffs Harbour 30� 19'S.), and between Coffs Harbour and Crowdy Head (31� 50'S.) were regressed on estimates of longshore current acceleration, mean longshore current and longshore wind stress, with the following results: (i) A relation was found between sea level difference from Coffs Harbour to Crowdy Head, and current acceleration. There was no similar relation for the section Evans Head to Coffs Harbour, and no reason could be found for the difference in behaviour between the two sections. (ii) A weakly defined relation was found, in both sections of the coast, between sea level difference and the square of the mean longshore current (a friction effect). (iii) An apparent relation was found, again in both sections of the coast, between sea level difference and longshore wind stress. This relation was more marked than expected from theory. The longshore currents were obtained from ships' drift, and covered a period of 2 years. The current data show a southward drift of current pattern, at an average rate of 9 km day-1. They also show a clear correlation between currents at the shelf edge (approximately 19 km offshore) and currents nearer shore (approximately 6.5 km offshore). It was found that the nearer-shore currents lagged the shelf-edge currents by between 7 and 10 days. Time and space correlations of the shelf-edge currents confirm earlier estimates from similar data. A frequency spectrum of the shelf-edge currents showed a broad maximum in the period range 50-170 days.

scholarly journals Volume, Heat, and Salt Transports through the Soya Strait and Their Seasonal and Interannual Variations

2017 ◽  
Vol 47 (5) ◽  
pp. 999-1019 ◽  
Author(s):  
Kay I. Ohshima ◽  
Daisuke Simizu ◽  
Naoto Ebuchi ◽  
Shuta Morishima ◽  
Haruhiko Kashiwase
Keyword(s):  
Sea Level ◽  
Velocity Structure ◽  
Volume Transport ◽  
Strongly Correlated ◽  
Volume Heat ◽  
Surface Gradient ◽  
Level Difference ◽  
Strait Time ◽  
Soya Strait ◽  
Sea Level Difference

AbstractVolume, heat, and salt transports through the Soya Strait are estimated based on measurements from high-frequency ocean radars during 2003–15 and all available hydrographic data. The baroclinic velocity structure derived from the climatological geopotential anomaly is combined with the sea surface gradient obtained from radar-derived surface velocities to estimate the absolute velocity structure. The annual-mean volume, heat, and salt transports are 0.91 Sv (1 Sv ≡ 106 m3 s−1), 25.5 TW, and 31.15 × 106 kg s−1, respectively. The volume transport exhibits strong seasonal variations, with a maximum of 1.41 Sv in August and a minimum of 0.23 Sv in January. The seasonal amplitude and phase roughly correspond to those of the Tsushima–Korea Strait. Time series of the monthly transport is presented for the 12 yr, assuming that the baroclinic components are the monthly climatological values. In cold seasons (November to April), the monthly volume transport is strongly correlated with the sea level difference between the Japan and Okhotsk Seas, and an empirical formula to estimate the transport from the sea level difference is introduced. It is likely that the sea level setup by the wind stress along the east coast of Sakhalin determines the sea level difference, which explains the seasonal and interannual wintertime variations of transport through the strait. The annual flux of water through the Soya Strait with a density greater than 26.8σθ, a potential source of Okhotsk Sea Intermediate Waters, is estimated to be 0.18 Sv.

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