HIGH FREQUENCY SOLAR INFLUENCE REVEALED IN SCLEROSPONGE-DERIVED CARIBBEAN SST RECORD

We present a high-resolution (annual) record of the Caribbean mixed layer temperature at different depths derived from oxygen isotopic ratios obtained from the sclerosponge Ceratoporella nicholsoni. Sclerosponges precipitate their calcium carbonate skeleton in equilibrium with their surrounding environment and are capable of living at depths down to 200 m. The sponges for this project were collected off the coasts of Puerto Rico and the US Virgin Islands in northeastern Caribbean Sea. The records obtained extend from the early 1500’s to the present and suggest that the Northeastern Caribbean was 1 – 2 °C cooler during the Little Ice Age than present conditions. Wavelet time series analysis of our records suggests that Caribbean SST variability is regulated by the 11 year sunspot cycle especially when the total solar irradiance (TSI) reaches a threshold value. When the threshold is surpassed the Caribbean SSTs show high coupling with the sunspot cycle. This threshold was determined to have an average value 1365.29 Wm^-2 until the first half of the 20^th century. Once the threshold was reached, TSI was able to explain more than 35% of the decadal variability observed in our records. Our findings also suggest a SST response to solar influence of 0.62 °C (W/m²)^-1 for the 20^th century which is in remarkable agreement with previously published climate sensitivity to solar radiation.