Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa, 2017, Vol. 14, No. 4, pp. 169-178
Sea level fluctuations and mesoscale eddies in the Northern Atlantic Ocean
V.A. Rozhkov
1 , Yu.P. Klevantsov
2 1 Saint Petersburg State University, Saint Petersburg, Russia
2 Saint Petersburg Branch of the State Oceanographic Institute, Saint Petersburg, Russia
Accepted: 07.07.2017
DOI: 10.21046/2070-7401-2017-14-4-169-178
A statistical analysis of the ensemble of space-time level fields from the data of satellite altimeter measurements performed in the Northern Atlantic Ocean (5°S – 70°N and 20°E – 80°W) with the discreteness of one day (1993–2013) is completed. Estimations of sea level fluctuations in synoptic, seasonal, and interannual variability ranges are made. The contributions of each range to level variability are compared; the annual makes the largest contribution. The spatial inhomogeneity of sea level fields driven by the system of currents and ocean divergence (convergence) zones, energy-active zones of ocean-atmosphere interaction, and centres of atmospheric action is shown. The largest average values (60 cm) of level are registered in the northern subtropical convergence, the least average values (–30 cm) in the area of Iceland. The method of probability analysis of a space-time field ensemble in view of its nonstationarity and inhomogeneity is suggested. The nonstationarity of level fields is determined by the parameters of trend and annual rhythm, the inhomogeneity is determined by the level field gradient vector. To estimate the direction and velocity of Rossby waves propagation, we applied the antenna method based on cross covariation analysis of realizations located in the points of net domain of wave propagation or in the antenna directivity. It is shown that those waves propagate west. The interpretation of sea level gradient fields is suggested in terms of eddy structures of gradient current velocity characterized by the divergence and rotor of vector space-time field. Their average values, variances, and covariation functions are estimated.
Keywords: Atlantic Ocean, altimetric measurements of sea level, space-time fields, gradients of current velocity and sea level, statistical analysis, Rossby waves
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