Meso-scale eddies and the impacts on variability of carbonate chemistry over deep coral reefs in the Florida Straits

Mingshun Jiang, Florida Atlantic University, Harbor Branch Oceanographic Institute, Boca Raton, FL, United States, Chudong Pan, Harbor Branch Oceanographic Institute, Ft. Pierce, FL, United States, Leticia Barbero, Atlantic Oceanographic and Meteorological Laboratory, Miami, FL, United States, Chuanmin Hu, University of South Florida, St. Petersburg, FL, United States, John Reed, Florida Atlantic University, Harbor Branch Oceanographic Institute, Fort Pierce, FL, United States, Joseph Salisbury II, University of New Hamsphire, United States and Richard H Wanninkhof, NOAA AOML, Ocean Chemistry and Escosystem Division, Miami, FL, United States
Abstract:
Abundant and diverse cold-water corals and associated fish communities can be found in the deep waters of the Florida Straits. Preliminary evidence suggests that corals in these deep coral habitats are living under sub-optimal conditions with the ambient aragonite saturation state (Ω) being only marginally above 1. Yet little is known regarding the temporal variability of carbonate chemistry parameters and their dynamic drivers in these critical habitats. In this presentation, we addressed this issue by using a recently developed circulation model and in situ data collected during two research cruises: the second Florida Shelf Edge Exploration Expedition (FloSEE2) in September 2011 and the second Gulf of Mexico East Coast Carbon Cruise (GOMECC2) in July 2012, both supported by NOAA. A numerical simulation was carried out for 2011-2012. In particular, we focused on two contrasting habitats: Pourtalès Terrace (200-450m) and Miami Terrace (270-600m) in the Florida Straits. The results suggest that there is strong weekly to seasonal variability in the bottom water properties including temperature, salinity, total CO2 and total alkalinity on the upper slope of the Straits. In particular, the minimum saturation state over Pourtalès Terrace can be as low as 1.5 whereas even at the top of Miami Terrace, Ω can be very close to 1. Further analysis suggests that the variability of water properties in the upper slope is largely driven by the large-scale transport, and upwelling of cold and CO2-rich deep waters due to meandering of Florida Current, and/or associated meso-scale eddies. In contrast, the water properties at the bottom of the slope are very stable but with much lower aragonite saturation state. The roles of local biochemical processes including the potentially elevated productivity and export driven by meso-scale eddies are yet to be explored. We further project that the aragonite saturation state in deep waters of the Florida Straits may be further decreased to around or below 1 in 2050 under the IPCC RCP 8.5 scenario.
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