Rapid 20th century warming in the Caribbean and impact of remote forcing on climate in the northern tropical Atlantic as recorded in a Guadeloupe coral

Abstract

We have generated 104-year long (1895-1999) monthly δ18O and Sr/Ca time series from a fast-growing Diploria strigosa coral core drilled off Guadeloupe Island, Lesser Antilles. Coral Sr/Ca reliably records interannual to decadal surface air temperature (SAT) variations in the region and shows a pronounced warming of approximately 1.5°C since 1950, with the strongest warming (1.2°C) occurring since 1975. This warming is also evident in SAT measured at Guadeloupe, which ends in 1951. Thus, our Sr/Ca series extends the air temperature record by 56years. We find that the past few decades are the warmest years over the entire period of record. The accelerated warming since 1950 is accompanied by a pronounced decrease in regional precipitation. This dampens the warming signal indicated by coral δ18O, which is too low (only 0.7-0.8°C since 1951). Consistently, δ18Osw estimated from the coral proxies also shows a strong decrease since 1950. Our data suggest an inverse relationship between SAT and precipitation (i.e. warmer and drier) for the latter half of the 20th century with the strongest trends since the mid-1970s. This is consistent with recent observational and model data, which report that while over the tropical oceans rainfall has increased due to an increase in sea surface temperatures, precipitation over land regions is reduced. A continuation of this warming and drying trend over Caribbean land regions would have severe societal consequences, especially in the context of anthropogenic warming. The El Niño Southern-Oscillation (ENSO) and the North Atlantic Oscillation (NAO) are the two major climate modes affecting large-scale SST variability in the northern tropical Atlantic. Both Sr/Ca and δ18O show a close relationship to ENSO and the NAO. A quantitative comparison between extremes in mean March-May coral δ18O and the Nino3 and NAO indices imply that climate variability in the northern tropical Atlantic is mainly forced by tropical Pacific and North Atlantic variability. Spectral analysis suggests that the relative importance of ENSO and the NAO is frequency dependent, with ENSO dominating at interannual, and the NAO dominating at interdecadal time scales. © 2010 Elsevier B.V.