Plenary 3: modeling ocean acidification progression in the Gulf of Mexico during recent decades (text & video)

OA Week 2021, Plenary Session 3 GOA-ON Goal #3 – Acquire and exchange data and knowledge necessary to optimize modeling for OA and its impacts

Dr. Fabian Gomez, Research Scientist, Northern Gulf Institute, Mississippi State University, and NOAA Atlantic Oceanographic and Atmospheric Laboratory, USA


Ocean Acidification (OA) progression is affected by multiple factors, such as ocean warming, biological production, and river runoff. Here we used an ocean-biogeochemical model to examine the drivers of the OA spatiotemporal variability in the Gulf of Mexico (GoM) during 1981-2014. The model showed negative pH and aragonite saturation state trends (ΩAr), linked to increasing levels of atmospheric CO2, which were close to values reported for the Subtropical North Atlantic. However, significant departures from the basin-mean trends were obtained over the northern GoM inner shelf, where the sign of the trends was positive. Model sensitivity analyses showed that OA progression in this last region was counteracted by enhanced alkalinity from the Mississippi-Atchafalaya River System (MARS). The model results also showed interdecadal changes in the OA indicators linked to the 1997-98 climate shift. We detected a stronger OA in the northern GoM shelf during 1999-2014, driven by interdecadal changes in the MARS’s ratio of alkalinity to dissolved inorganic carbon. Away from the northern GoM shelf, surface warming during 1981-1998 and a weak surface cooling during 1999-2014 promoted a stronger positive trend for ΩAr while counteracted the trend changes for pH and partial pressure of CO2. Our findings highlight that river alkalinity is a key driver of the low-frequency carbon system variability and emphasize the need for considering realistic freshwater chemistry fluxes to properly assess acidification in coastal waters.

Ocean Acidification Week 2021 was sponsored by the following organizations:

(1) GOA-ON, the Global Ocean Acidification Observing Network,

(2) NOAA, the United States National Oceanic & Atmospheric Administration,

(3) IAEA OA-ICC, the International Atomic Energy Agency – Ocean Acidification International Coordination Centre, and

(4) IOC-UNESCO – the Intergovernmental Oceanographic Commission of the United Nations Educational, Scientific and Cultural Organization

For more information, please visit

GOA-ON, YouTube, 24 September 2021. Text and video.

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