Ocean Acidification on a Crossroad

Principal Investigator

Enhanced respiration, upwelling, increasing atmospheric CO2, and their interactions in the northwestern Gulf of Mexico

Human society has had significant influence on the global ocean carbonate chemistry (also known as “ocean acidification” or “OA”) through fossil fuel combustion, deforestation, and cement production over the past 250 years. In the coastal ocean, however, other forces such as continental nutrient input and physical oceanographic changes can have stronger impacts on both the magnitude of short-term variations and the long-term trends in carbonate parameters (pH, carbonate saturation states). Among the National Oceanographic and Atmospheric Administration (NOAA) designated Large Marine Ecosystems, the Gulf of Mexico (GOM) remains poorly understood in terms of its current OA conditions, despite its ecological and economic significance. In the northwestern GOM (nwGOM), decadal acidification has been observed in the shelf-slope region, with metabolic production of CO2 contributing to a larger fraction of CO2 accumulation than uptake of anthropogenic CO2, and the observed rate of acidification is significantly greater than that in other tropical and subtropical areas. Unfortunately, whether the observed OA in this region represents a short-term phenomenon or a long-term trend is unknown.

It is hypothesized that increasing atmospheric CO2, increasing terrestrial nutrient export due to an enhanced hydrological cycle, and enhanced upwelling due to climate change will cause the continental shelf-slope region in the nwGOM to acidify faster than other tropical and subtropical seas. It is imperative to employ sustained monitoring in this region because it is rich in coral reefs, banks, and other topographic features and is therefore ecologically sensitive to changing ocean chemistry.

To test this hypothesis, both field and modeling studies are proposed. HRI Chair for Ecosystem Science and Modeling Dr. Xingping Hu is working in collaboration the Department of Mathematics and Statistics at Texas A&M University-Corpus Christi, Department of Oceanography at Texas A&M University, the Cooperative Institute for Marine and Atmospheric Studies at the University of Miami, and NOAA’s Atlantic Oceanographic and Meteorological Laboratory.

The fieldwork will include high spatial (wave glider) and temporal (fixed in-situ sensors) resolution measurements in surface and shallow waters, respectively, discrete water sample collection and analysis for the entire water column (up to 1,000 meters), and underway surface measurements on board a research vessel. This project will also incorporate the newest data from an upcoming large scale nwGOM survey, and oceanographic and statistical modeling will be used to integrate the chemical signals into the models to hindcast/predict spatial and temporal variations of OA signals for the optimization of monitoring design and implementation. This project will have the Gulf Coast Ocean Observing System (HRI Systems Architect Felimon Gayanilo) as an integral member for the data management and sharing tasks.

An advisory committee consists of experts in monitoring, modeling, natural resource management, and infrastructure management. These experts will guide the progress and direction of this field-intensive project and ensure that the outputs and outcomes of this project will meet the long-term goal of optimizing OA monitoring in the nwGOM and will provide documentation of methodology that can be used in similar efforts in the future.

This project will benefit NOAA’s Ocean Acidification Program by intensively examining an area in the poorly understood GOM Large Marine Ecosystem by producing the first ever high-resolution data that are from not only the surface water, but also subsurface waters, and directing the future deployment of in-situ monitoring devices in this ecologically and economically important region. Broad dissemination of data and modeling products will be carried out via open-access data services and peer-reviewed publications. Educational activities — including trainings for graduate students from underrepresented groups, public seminars, and participation in 9th-12th grade curriculum development — are planned and will be carried out throughout the duration of this project.