PP53C-2356
Comparison of coral δ18O with pseudocorals derived from in situ sea surface salinity and temperature measurements
Friday, 18 December 2015
Poster Hall (Moscone South)
Kristine L DeLong1, Nazanin Chaichi2, Christopher R Maupin3,4, Julie N Richey5, Terrence M Quinn4 and Richard Z. Poore5, (1)Louisiana State University, Geography and Anthropology, Baton Rouge, LA, United States, (2)Louisiana State University, School of the Coast and the Environment, Baton Rouge, LA, United States, (3)Texas A&M University, Department of Geography, College Station, TX, United States, (4)University of Texas at Austin, Austin, TX, United States, (5)USGS, St. Petersburg, FL, United States
Abstract:
Paleoclimatologists use pseudocorals and forward modeling of coral oxygen isotopes (δ18O) to assess δ18O variations for comparison with climate model output in order to understand past tropical oceanic-atmospheric variability. Oxygen isotopic (δ18Ocoral) variability in shallow water coral skeletons is dependent on sea surface temperature (SST) and δ18O of seawater (δ18Osw), which varies with sea surface salinity (SSS). However, measurements of δ18Osw and SSS are sparse; therefore, simulated SSS (e.g., SODA) is typically used in pseudocoral investigations. Our study site is the Dry Tortugas National Park (DRTO; 24º42'N, 82º48'W) in the southeastern Gulf of Mexico (GOM) where hourly SST and SSS measurements are available from NOAA buoys (1992–2002) and the Florida Keys National Marine Sanctuary (FKNMS; 2011–2014). Here we use bivariate forward modeling of monthly average buoy SSS and SST to develop a time series of pseudocoral δ18O (δ18Op = –0.22(‰/ºC)SST + 0.11(‰/psu)SSS) for DRTO that are compared with δ18Ocoral variations from three Siderastrea siderea coral colonies growing in close proximity within the park. We use the relationship for δ18Osw and SSS determined for Flower Garden Banks coral reef in the northern GOM (27º52'N, 93º49'W) since no measurements of δ18Osw are currently available for DRTO. δ18Op co-varies with δ18Ocoral (r2 = 0.59) with a root mean square error (RMSE = 0.32‰) greater than the intercolony δ18Ocoral variability (r2 = 0.80; RSME = 0.07‰). Discrepancies between δ18Op and δ18Ocoral may be related to the lack of a local SSS-δ18Osw relationship for DRTO or uncertainties in subannual time assignment for δ18Ocoral. A new source of SSS is the NASA satellite Aquarius (2012–2014), which may be useful in future pseudocoral studies, that is evaluated along with high resolution simulated SSS (Global Ocean Physics Reanalysis GLORYS2V3; 1993–2012). We find similar correlation between Aquarius-derived SSS and FKNMS SSS (r2 = 0.68; RMSE = 0.24 psu) and between simulated SSS and buoy SSS (r2 = 0.68; RMSE = 0.35 psu).
