Increasing anthropogenic carbon dioxide emissions have led to clearly observable changes in carbon cycling throughout the global oceans. Repeat Gulf of Mexico Ecosystems and Carbon Cycle (GOMECC) cruises, led by NOAA, provide critical climate-grade carbonate chemistry datasets for monitoring ocean acidification (OA). The GOMECC surveys represent the only Gulf-wide research missions that have collected inorganic carbon parameters (i.e., pH, total alkalinity, total dissolved inorganic carbon, and partial pressure of CO₂) simultaneously across the entire basin (and shelf-basin continuum). As such, these datasets are uniquely suited to evaluate acidification in the Gulf of Mexico and its implications for ocean ecosystems. Four GOMECC summertime surveys conducted between 2007-2021, encompassing ~346 stations, offer unparalleled insights into natural and anthropogenic OA dynamics in both the coastal and open-Gulf water column. Across the GOMECC time-series, three shelf-basin transects had full water-column sampling (Tampa, Louisiana, Texas Transects). Here we present observations of declining in situ pH and quantify anthropogenic contributions. For the three full water-column transects in the open-Gulf (>1000m water depth), an average pH decrease of 0.005 units was observed in the upper 500m and the observed yearly pH decrease in the surface mixed layer (~150m) was -0.0013/yr, consistent with the observations of Gomez et al., 2021. Consistent with expectations, pH changes at depths greater than 1000 meters were insignificant.

Primary Presenter: Macarena Martín Mayor, University of South Florida (mmartinmayor@usf.edu)

Authors:

Macarena Martín Mayor, University of South Florida  (mmartinmayor@usf.edu)

Emily Osborne, NOAA - AOML  (emily.osborne@noaa.gov)

Leticia Barbero, NOAA - AOML  (leticia.barbero@noaa.gov)

Robert Byrne, University of South Florida  (rhbyrne@usf.edu)