The Caribbean Sea and Gulf of Mexico

[See also: OAPS for the East Coast of the USA]

Several significant improvements have been made to the existing OAPS. Specific algorithms describing TA-SSS/SST relationships have been introduced for the Mississippi outflow region and Galveston area. A newer version of SST data was used that eliminated many of the artifacts seen in the previous iteration. All the data for 2014-2017 has been reprocessed.

Scientists of the ACCRETE (Acidification, Climate, and Coral Reef Ecosystems Team) Lab of AOML’s Ocean Chemistry and Ecosystems Division (OCED) have constructed a tool to monitor ocean acidification over the wider Caribbean and Gulf of Mexico. This tool utilizes satellite data and a data-assimilative hybrid model to map the components of the carbonate system of surface water. This effort represents an update to the experimental Ocean Acidification Product Suite (OAPS) developed by Coral Reef Watch (

To resolve the seawater carbonic acid system, we use the partial pressure of CO2 (pCO2) and pH. Surface pCO2 is approximated by taking total tropospheric column CO2 from the AIRS mid-tropospheric CO2 and AMSU instruments on board the Aqua satellite ( and adjusting it for the marine boundary layer by replacing the annual cycle of the observed AIRS data with that from the NOAA Marine Boundary Layer ( Following this adjustment, seawater pCO2 is estimated using an empirical model relating the differential between sea surface and atmospheric CO2 partial pressure to changes in CO2 gas solubility (K0).

Since 2017 the AIRS data is no longer available, as a temporary solution surface pCO2 was obtained from a multi model global climate model ensemble. For 2017 onwards the variable spco2 from CMIP6 models with SSP5-8.5 forcing was used. SSP5-8.5 is a high emission scenario, but similar to current emissions.

Total alkalinity (TA) is calculated using three separate algorithms for three distinct areas derived from Cai et al. (2006).

Galveston area, 27°N – 31°N and 264°E – 267°E, and SSS < 35
TA = 8.8 * SSS + 1996.7

MS outflow area, 27°N – 31°N and 267°E – 276°E, and SSS < 35
TA = 2.8 * SSS + 2400

Caribbean Sea
TA = (57.3 * SSS) + 296.4

Sea surface temperature is derived from an optimal interpolated, multi-sensor L4 foundation SST product v05.0 from Remote Sensing Systems at 9km resolution (

The updated v5.0 MW+IR data removed many of the artifacts seen in the previous iteration of the OAPS (Fig.1).

OAPS: comparison of previous and current productsFigure 1: Comparison of previous (left) and current (right) OAPS pCO2 fields. Note the artifacts around northern Cuba and the Bahamas present in the previous version, but absent in the current OAPS.

Salinity is obtained from 0.25º SMAP Salinity V4 from ( These measurements, together with pCO2 and TA, allow calculation of the complete carbonate system. Data are updated monthly at a 9km resolution. Initial results indicate good agreement with observed values from cruises and MAPCO2 buoys, but further testing and refinement of algorithms is planned.

The following animations show the monthly progression of pH, surface pressure of CO2, total alkalinity, aragonite saturation state (Ωarag) and calcite saturation state (Ωcalc) in 2020. Clicking any animation will load it in its original, full-sized format.

The monthly progression of pH in 2020

The monthly progression of surface pressure of CO2 in 2020

The monthly progression of total alkalinity in 2020

The monthly progression of aragonite saturation state (Ωarag) in 2020

The monthly progression of calcite saturation state (Ωcalc) in 2020

For each of the variables, a netCDF file can be downloaded that has 12 monthly values on a grid with 205 cells latitude, 398 cells longitude. The domain is bounded by 14°N to 32°N, 95°W to 60°W. The variables that can be downloaded (by clicking the desired data year in the list below) are:

For further details about this product, contact Dr. Ruben van Hooidonk. The development and maintenance of this product is supported by the NOAA Ocean Acidification Program.

Cai, W.‐J., X. Hu, W.‐J. Huang, L.‐Q. Jiang, Y. Wang, T.‐H. Peng, and X. Zhang (2010), Alkalinity distribution in the western North Atlantic Ocean margins, J. Geophys. Res., 115, C08014, doi:10.1029/2009JC005482.