Oceanographic investigation in the Southeastern Pacific Ocean by satellite radiometry and altimetry data

Ten-day sea level anomalies (SLA) charts, based on the TOPEX/Poseidon (T/P) altimetry data for 1992–2003, as well as corresponding charts of sea surface dynamic heights constructed by the superposition of SLA distributions over the climatic dynamic topography, were used to study main oceanic currents in the region 45°S–20°S, 110°W–70°W. Spatial and seasonal variability of the South Pacific Current has been investigated based on the maps of dynamic topography (DT) gradients. Also maps of the temperature gradients at the ocean surface were used to study the mesoscale variability related to the Subtropical Front (STF) in the Southeastern Pacific. The analysis allowed to distinguish the zones with different degree of variability in the current and front positions. The variability is minimal at 99°W, where the current is most intensive. Westward of 105°W, the RMS of the STF position may reach 3° of latitude. This is accompanied by a pronounced spectral peak with a period of 350 days in its temporal variability. Eastward of 105°W, there is no dominant peak in the frequency spectra describing the variability of the current and front. Comparison of the satellite derived front and current positions with in situ data acquired during R/V “Atlantida” expedition in November–December 2002 shows a good correspondence. Zones of high dynamic topography gradients and sea surface temperatures gradients coincide within the physical errors of the method. The analysis of pelagic fish distribution patterns in the Southeastern Pacific Ocean based on acoustic survey data and synoptic variability of the dynamic topography reveals that most dense fish concentrations relate to dynamic heterogeneities, which are located at the northern periphery of the Subtropical Front.