Abstract
The Gulf of Mexico (GOM) is highly sensitive to oceanic and atmospheric variability in the Atlantic and Pacific Oceans. Interannual variability in the El Nino-Southern Oscillation (ENSO) and decadal variability in the Atlantic Multidecadal Oscillation (AMO) drive significant annual differences in the amount of rainfall and, therefore, freshwater runoff that is discharged into the Gulf of Mexico via the Mississippi River. Average annual Mississippi River discharge is 600,000 cfs at New Orleans, which is equivalent to 4,488,000 gallons per second or 1.42 X 10 (super 14) gallons of water per year. However, discharge can vary from as low as 100,000 cfs during drought years to greater than 1.4 million cfs. This wide range of freshwater input into the northern Gulf of Mexico can have a profound impact on the salinity and seawater oxygen isotope values of the GOM. Oxygen isotope (delta (super 18) O) variability in shallow water coral skeletons and other marine carbonates is dependent upon the sea surface temperature (SST) and delta (super 18) O of the seawater, which varies with seawater salinity. Using a paired coral Sr/Ca-derived SST record and new delta (super 18) O data from a Siderastrea siderea coral from the Flower Garden Banks (FGB; 27 degrees 52.5'N, 93 degrees 49'W), we use the previously established relationship between seawater delta (super 18) O and salinity to reconstruct salinity variations in the northern Gulf of Mexico from 1930-2005. The reconstructed salinity record will be compared to modeled (e.g., SODA) and in-situ salinity data as well as pseudocoral models. The coral Sr/Ca-SST calibration equation for S. siderea is the same for 48 corals in the Gulf of Mexico and Caribbean Sea when calibrated using in situ or SST data products (i.e., high resolution satellite SST estimates) with the exception of a different intercept for FGB, which is a deeper reef (reef top of 18 m). This stable calibration allows us to better constrain the coral delta (super 18) O seawater reconstruction especially when coupled with the known seawater delta (super 18) O to salinity relationship for FGB, and the available in situ SST and salinity data. It is rare for a coral reconstruction site to have these data sets and will be valuable in assessing the paired coral Sr/Ca and delta (super 18) O reconstructions. Of particular interest will be whether decadal salinity variability in the GOM is correlated with the AMO, ENSO, and the Dust Bowl of the 1930s.