The climatic conditions in the Arctic, and observations of the wind-induced drift of ice made in connexion with Fridtjof Nansen’s Fram expedition, led to the discovery 100 years ago by Vilhelm Bjerknes’ pupil, V.W. Ekman, of the importance of the Earth’s rotation in limiting the depth of the wind-induced shear current in the ocean. This essay commemorates the centenary of Ekman’s seminal paper,...

Several computational experiments were carried out with a state-of-the-art ocean general circulation model to identify the northward directed Ekman transport of Antarctic and Subantarctic origin surface water as a mechanism which forces mid-latitude convection. The results indicate that the wind-driven transport of water in the surface layer is most efficient at increasing the depth of convecti...

[1] Abstract: The density structure along the ocean margins carries an integrated imprint of ocean circulation. The difference in pressure between the eastern and western margins of the ocean reflects the net meridional geostrophic transport across the ocean basin. If one assumes that the wind driven circulation is closed in the upper ocean, the wind driven component of the net geostrophic tran...

Adjoint methods of sensitivity analysis were applied to the California Current using the Regional Ocean Modeling Systems (ROMS) with medium resolution, aimed at diagnosing the circulation sensitivity to variations in surface forcing. The sensitivities of coastal variations in SST, eddy kinetic energy, and baroclinic instability of complex time-evolving flows were quantified. Each aspect of the ...

The European Centre for Medium-Range Weather Forecasts (ECMWF) and Institut Francais Pour la Recherche et l’Exploitation de la Mer European Remote-Sensing Satellite, named IFR2, surface wind velocity data products are compared during July 1995 over the Arabian Sea. Substantial differences were found. The central positions of the maximum isotach were separated by 450 km, and the ECMWF maximum is...

The surface current response to winds is analyzed in a two-year time series of a 12 MHz (HF) Wellen Radar (WERA) off the West coast of France. Consistent with previous observations, the measured currents, after filtering tides, are of the order of 1.0 to 1.8% of the wind speed, in a direction 10 to 40 degrees to the right of the wind, with systematic trends as a function of wind speed. This Lag...

The first theory of wind-driven flow is that of Ekman, who assumed a uniform eddy viscosity and derived the velocity spiral that bears his name. Over the years, observations of wind stress and current have improved to the point that frictional momentum transfer in the upper ocean can be quantified. Observations of velocity spirals are reviewed to address such issues as the vertical structure an...

By incorporating the wave-induced Coriolis-Stokes forcing into the classical Ekman model, the wind energy input to the Ekman-Stokes layer is investigated, with an emphasis on the surface wave effects when the direction of Stokes drift deviates from that of wind stress. Theoretical analysis of the kinetic energy balance of the EkmanStokes layer shows that the total wind energy input consists of ...

Anomaly patterns in the Southern Ocean in response to variability in the atmospheric forcing are investigated. To this end we forced the Hamburg large-scale geostrophic ocean general circulation model with surface uxes from the European Centre for Medium{Range Weather Forecasts reanalysis (ERA). ERA covers the period January 1979 through February 1994. First, the atmospheric variability of sea ...

North Pacific decadal oceanic and atmospheric variability is examined from a 650-yr control integration of the Community Climate System Model version 2. The dominant pattern of winter sea surface temperature (SST) variability is similar to the observed “Pacific decadal oscillation,” with maximum amplitude along the Kuroshio Extension. SST anomalies in this region exhibit significant spectral pe...