Physical Oceanography, Vol. 16, No. 3, 2006
SEASONAL VARIABILITY OF GEOSTROPHIC CURRENTS IN THE
ATLANTIC OCEAN ACCORDING TO THE ALTIMETRY DATA
Yu. V. Artamonov
UDC 551.46 (269.4)
The monthly average values of the anomalies of the ocean level (according to the satellite data
for 1992–2002) and the annual average dynamic heights (hydrological data) are used to compute
the seasonal cycle of geostrophic currents on the surface of the Atlantic Ocean. It is shown that
the west and east currents are intensified with a phase difference of several months. At the same
time, their latitudinal displacements are quasisynchronous. A delay of the seasonal signal in the
east–west direction of about
months (on the average) is typical of currents in the tropical
zone of the Northern Hemisphere. On the contrary, in the South Atlantic, the seasonal signal
propagates in the west–east direction and its phase delay can be as large as almost six months.
The generalization of the results of numerous investigations devoted to the circulation of waters in the At-
lantic Ocean shows that the indicated circulation can be regarded as a system of cyclonic and anticyclonic gyres
alternating in the meridional direction with well-pronounced zonal boundaries in the form of large-scale currents.
As the main currents of this sort, we can mention the North Atlantic (NAC) and North Equatorial (NEC) Cur-
rents, the North Equatorial Countercurrent (NECC) and its north branch (NB-NECC), the Lomonosov Current
(LC), three branches (north, central, and south) of the South Equatorial Current (NB, CB, and SB SEC), the
South Equatorial Countercurrent (SECC), the recirculation branch of the Brazil Current (RB BC), the South At-
lantic Current (SAC), and three branches (north, central, and south) of the Antarctic Circumpolar Current (NB,
CB, and SB ACC). The annual harmonic (especially well pronounced in the tropical zone) is predominant in the
seasonal variations of currents over the most part of water area of the Atlantic Ocean. At present, the regional
specific features of the seasonal cycles of NEC, NECC, and LC are described in detail in [1–5]. At the same, the
data on the seasonal variability of the other currents are, for the most part, quite poor. In the South Atlantic, the
data on the seasonal cycles of currents are practically absent because this region is characterized by much lower
intensity of observations than the North Atlantic.
In the last decades, the data of satellite measurements of the ocean level are extensively used for the inves-
tigation of the circulation of waters. Thus, these data were applied for the analysis of the seasonal cycles and
synoptic variability of currents in the northwest part of the Tropical Atlantic [6, 7], in the Indian Ocean , and
in the Southern Ocean . The cited works are, for the most part, based on relatively short
observations that do not cover a typical period of interannual variations
yr). This means that the conclu-
sions made in these investigations are inapplicable to the mean climatic seasonal cycles. At present, the series of
accumulated satellite altimetry data covers a period of about ten years. The aim of the present work is to study
the seasonal variability of the anomalies of level and geostrophic currents on the surface of the Atlantic Ocean on
the basis of the contemporary satellite data array.
Marine Hydrophysical Institute, Ukrainian Academy of Sciences, Sevastopol.
Translated from Morskoi Gidrofizicheskii Zhurnal, No.
60–71, May–June, 2006. Original article submitted December 30, 2004;
revision submitted March 9, 2005.
0928-5105/06/1603–0177 © 2006 Springer Science+Business Media, Inc. 177