Wind speed trends over the Southeastern continental shelf of South America, between 33° and 50° S

Abstract

Surface scalar wind speed trends (from 1979 to 2009) at the southwestern Atlantic Ocean, between 33° and 50°S and 55° and 70°W, were estimated from the NCEP/NCAR I (NR1) and the Climate Forecast System Reanalysis (CFSR) using Sen's slope. Trends were tested using the seasonal Mann-Kendall test. Scalar wind speed trends computed from NR1 database were positive throughout the whole study area, with values ranging from +0.01 to +0.03 m s-1 year-1. On the contrary, wind speed trends computed from CFSR database were rather different to trends obtained from NR1 reanalysis. Wind speed and sea surface temperature (SST) trend patterns, both computed from CFSR database, seem to be quite consistent but, in general, no apparent relationship between both patterns was obtained when different global databases were analysed. Sea surface wind speed data compiled from multiple satellite observations were also used to compute wind speed trends. Computed satellite trends resulted in very good agreement with positive values obtained from NR1 database. NR1 data series presented significant inter-annual to multi-decadal oscillations at the Argentinean continental shelf, but they would not seem to be associated either with the Southern Annular Mode or with El Niño Southern Oscillation. Possible impacts of positive speed wind trends on the mean depth of the ocean mixed layer and on the wind wave climate are briefly discussed.