Variability of bottom carbonate chemistry over the deep coral reefs in the Florida Straits and the impacts of mesoscale processes

Journal Article · Fri Jan 03 00:00:00 UTC 2020 · Ocean Modelling

DOI: https://doi.org/10.1016/j.ocemod.2019.101555 · OSTI ID:1986607

Jiang, Mingshun ^[1]; Pan, Chudong ^[2]; Barbero, Leticia ^[3]; Reed, John ^[4]; Salisbury, Joseph E. ^[5]; VanZwieten, James H. ^[4]; Wanninkhof, Rik ^[3]

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1. Florida Atlantic Univ., Boca Raton, FL (United States); Florida Atlantic University
2. Florida Atlantic Univ., Boca Raton, FL (United States); National Oceanic and Atmospheric Administration (NOAA), Silver Spring, MD (United States)
3. National Oceanic and Atmospheric Administration (NOAA), Miami, FL (United States). Atlantic Oceanographic and Meteorological Laboratory
4. Florida Atlantic Univ., Boca Raton, FL (United States)
5. Univ. of New Hampshire, Durham, NH (United States)

Abundant and diverse cold-water coral and fish communities can be found in the deep waters of the Florida Straits, which are believed to be living under suboptimal conditions impacted by increasing oceanic CO₂ levels. Yet, little is known regarding the spatial-temporal variability of bottom carbonate chemistry parameters and their dynamic drivers in this area. To address this issue, we present results from numerical simulations of a coupled physical-biogeochemical model for the south Florida shelf and Florida Straits. Our exploratory analysis focuses on two well-known deep-coral habitats: Pourtalès Terrace (200-450 m) and Miami Terrace (270-600 m). Results suggest that bottom waters along the northern/western slope of the Straits are comprised primarily of the North Atlantic Central Water (NACW) and Antarctic Intermediate Water (AAIW), driven by upwelling associated with the bottom Ekman transport of the Florida Current. Over the Pourtalès Terrace, both the meandering of the Florida Current and mesoscale eddies modulate the upwelling (downwelling) of cold (warm) waters. In contrast, Florida Current makes a sharp turn at the southern end of the Miami Terrace leading to persistent island wakes, frequent occurrences of a transient eddy, and strong upwelling of deep waters toward the platform of the terrace. Passage of the transient eddy often accompanies strong downwelling of warm waters and a return (southward) flow on top of the platform. Overall, bottom water properties including temperature (T), dissolved inorganic carbon (DIC) and total alkalinity (TA) show strong variability on weekly to monthly time-scales over entire Pourtalès Terrace and on the platform of Miami Terrace mostly driven by physics. In deeper areas (>400 m), bottom water properties are fairly stable with both DIC and TA showing narrow ranges. Interestingly, waters over the southeastern portion of the Pourtalès Terrace show consistently warmer temperature, lower DIC, and higher TA than those on top of this terrace. The aragonite saturation state (Ω) ranges 1.2-2 on top of the Pourtalès Terrace and 1.2-1.7 both on top of Miami Terrace and on the upper slope of Pourtalès Terrace. In the deeper slope areas (> 400 m), it is nearly constant at 1.2-1.3. Further, this modeling effort suggests that remote forcing and biogeochemical processes along the transport paths, from the Gulf of Mexico to the Straits, are significant but second-order contributors to the variability of bottom carbonate chemistry. The impacts of benthic biogeochemical processes along the transit paths are not resolved.

• Research Organization: Florida Atlantic Univ., Boca Raton, FL (United States)
• Sponsoring Organization: National Oceanic and Atmospheric Administration (NOAA); USDOE
• Grant/Contract Number: EE0000319; EE0004200
• OSTI ID: 1986607
• Journal Information: Ocean Modelling, Journal Name: Ocean Modelling Vol. 147; ISSN 1463-5003
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English