Interannual Variability and Trends of Sea Surface Temperature Around Southern South America

Published in	Frontiers in Marine Science 9
Authors	Risaro, Daniela B. Chidichimo, María Paz Piola, Alberto R.
Publication year	2022
DOI	http://dx.doi.org/10.3389/fmars.2022.829144
Affiliations	Departamento de Oceanografía, Servicio de Hidrografía Naval, Buenos Aires, Argentina Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina Departamento de Ciencias de la Atmósfera y los Océanos, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina CNRS-IRD-CONICET, UBA Instituto Franco-Argentino para el Estudio del Clima y sus Impactos (UMI 3351 IFAECI), Buenos Aires, Argentina
IAI Program	Inter-American Institute for Global Change Research (IAI) CRN3070 which is supported by the U.S. National Science Foundation (grant no. GEO-1128040) and IAI grant no. SGP-HW 017.
IAI Project	SGP-HW 017
Keywords	sea surface temperature Southwest South Atlantic interannual variability climate variability trends sea-air interaction atmospheric forcing
	Interannual Variability and Trends of Sea Surface Temperature Around Southern South America.pdf

Abstract

The interannual variability and trends of sea surface temperature (SST) around southern South America are studied from 1982 to 2017 using monthly values of the Optimally Interpolation SST version 2 gridded database. Mid-latitude (30°&ndash50°S) regions in the eastern South Pacific and western South Atlantic present moderate to intense warming (~0.4°C decade&minus1), while south of 50°S the region around southern South America presents moderate cooling (~ &minus0.3°C decade&minus1). Two areas of statistically significant trends of SST anomalies (SSTa) with opposite sign are found on the Patagonian Shelf over the southwest South Atlantic: a warming area delimited between 42 and 45°S (Northern Patagonian Shelf NPS), and a cooling area between 49 and 52°S (Southern Patagonian Shelf SPS). Between 1982 and 2017 the warming rate has been 0.15 ± 0.01°C decade&minus1 representing an increase of 0.52°C at NPS, and the cooling rate has been &ndash0.12 ± 0.01°C decade&minus1 representing a decrease of 0.42°C at SPS. On both regions, the largest trends are observed during 2008&ndash2017 (0.35 ± 0.02°C decade&minus1 at NPS and &ndash0.27 ± 0.03°C decade&minus1 at SPS), while the trends in 1982&ndash2007 are non-significant, indicating the record-length SSTa trends are mostly associated with the variability observed during the past 10 years of the record. The spectra of the records present significant variance at interannual time scales, centered at about 80 months (~6 years). The observed variability of SSTa is studied in connection with atmospheric forcing (zonal and meridional wind components, wind speed, wind stress curl and surface heat fluxes). During 1982&ndash2007, the local meridional wind explains 25&ndash30% of the total variance at NPS and SPS on interannual time scales. During 2008&ndash2017, the SSTa at NPS is significantly anticorrelated with the local zonal wind (r = &ndash0.85), while at SPS it is significantly anticorrelated with the meridional wind (r = &ndash0.61). Our results show that a substantial fraction of the interannual variability of SSTa around southern South America can be described by the first three empirical orthogonal function (EOF) modes which explain 28, 16, and 12% of the variance, respectively. The variability of the three EOF principal components time series is associated with the combined variability of El Niño&ndashSouthern Oscillation, the Interdecadal Pacific Oscillation and the Southern Annular Mode.