Sea surface temperature anomalies, seasonal cycle and trend regimes in the Eastern Pacific coast
JOSE ALEJANDRO RAMOS RODRIGUEZ
DANIEL BERNARDO LLUCH COTA
SALVADOR EMILIO LLUCH COTA
ARMANDO TRASVIÑA CASTRO
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"We used the extended reconstruction of sea surface temperature (ERSST) to analyze the variation of surface temperature and the seasonal cycle along the coast of the eastern Pacific (60_ N–60_ S, 61 pixels alongshore) from 1950 to 2010 (732 months). First we analyzed the monthly anomalies and looked for a relationship of such anomalies with Total Solar Radiation (TSI) and then the Regime Shift Detector (RSD) was applied to detect possible temperature regimes in the series. Afterwards, we calculated a yearly temperature range per pixel (amplitude of seasonal cycle) and through the subtraction of a latitudinal theoretical curve of temperature based on solar irradiance, the residuals of the seasonal cycle were obtained. The results showed an almost complete spatial synchrony and dominance of negative anomalies from 1950 to mid-late 1970’s, with a switch to near-zero and positive anomalies in the late 1990’s when a shift to negative values was detected. Such a shift lasted until the early 2000’s when positive anomalies appeared again but there was a change to negative anomalies in the late 2000’s. These results were supported by the RSD. The TSI variability shows a clear relationship with that of sea surface temperature anomalies and with the regime changes. This is probably due to a difference in the amount of energy received from the sun. Comparing the “cool regime” versus the “warm regime”, the second one received 0.39% more energy (approximately 3×108 Jm−2) from the sun. Seasonal cycles show larger range at northern latitudes (>40_N), northern tropical-temperate transition zone (20_–26_ N) and in the tropical-equatorial band (0_–30_ S). The smaller ranges occur at 0_–16_ N and 50_–60_ S. The residuals (seasonal minus the theoretical curve) indicated a clear modulation due to advection by ocean currents."
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