Abstract
Sea surface temperature (SST) in the Intra-Americas Sea (IAS), which includes the Caribbean Sea and Gulf of Mexico (GOM), plays a vital role in the climate and hydroclimate of the Americas and understanding of how SST impacts this region is critical. Despite advancements in global climate models (GCMs), coupled atmosphere-ocean GCMs reveal the IAS has a cold bias ( approximately 2 degrees C) in mean SST calling into question future climate predictions for SST thresholds such as coral bleaching and tropical cyclone formation. We are building a network of SST reconstructions using the massive coral Siderastrea siderea for the past approximately 250 years, Holocene, and Last Interglacial (LIG) to provide temporal targets for diagnosing GCMs and the IAS cold bias. Calibration and replication studies for this coral species from GOM to Brazil are yielding consistent transfer equations allowing us to assess absolute SST for past intervals as well as seasonal to decadal variability. The 20th century reconstructions reveal the GOM (Flower Garden Banks and Dry Tortugas) has the greatest seasonality and quasi-consistent variability between the north and southeast GOM whereas corals from Haiti and Little Cayman have less seasonality and distinct interannual variability compared with the GOM corals. A 75-year long LIG (128 ka) coral SST reconstruction from Hispaniola in the northern Caribbean reveals mean SST similar to today with greater seasonal, interannual, and decadal variability whereas the Community Climate System Model version 3 (CCSM3) 125 ka simulation suggest approximately 2 degrees C colder mean SST and suppressed interannual and decadal variability yet CCSM3 does have the same seasonal range as the coral. The cold bias is reduced, but the seasonal range increases in a 127 ka simulation from the Community Earth System Model 2. A mid-Holocene coral (5.6 ka) from Little Cayman Island (LIC) in the central Caribbean is slightly warmer with less seasonality with suppressed interannual variability compared to today whereas other corals from this island dated to 1.25 ka suggest slighter cooler intervals later in the Holocene. These storm-washed corals were transported inland several meters over sand dunes suggesting storm surge from major hurricanes impacted LIC during the Holocene when summer temperatures exceeded 28 degrees C, the SST threshold for a hurricanes in the Atlantic Ocean.