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Climate Change Projected to Exacerbate Impacts of Coastal Eutrophication in the Northern Gulf of Mexico
Author(s) -
Laurent Arnaud,
Fennel Katja,
Ko Dong S.,
Lehrter John
Publication year - 2018
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2017jc013583
Subject(s) - eutrophication , hypoxia (environmental) , ocean acidification , environmental science , upwelling , oceanography , stratification (seeds) , climate change , biogeochemistry , biogeochemical cycle , nutrient , ecology , geology , environmental chemistry , oxygen , chemistry , seed dormancy , biology , germination , botany , organic chemistry , dormancy
The continental shelf in the northern Gulf of Mexico experiences expansive seasonal hypoxic conditions and eutrophication‐driven acidification in bottom waters. Rising surface ocean temperatures, freshwater and nutrient inputs, and atmospheric CO 2 will further exacerbate these conditions. Using a high‐resolution, regional circulation‐biogeochemical model, we simulated the spatiotemporal dynamics of oxygen and inorganic carbon in the northern Gulf of Mexico under present and a projected future (2100) climate state. Results indicate a modest expansion of the hypoxic zone, but more severe hypoxia and greater exposure to prolonged hypoxic conditions. The main drivers underlying these changes are a reduction in oxygen solubility (accounting for 60–74% of the change) and increased stratification (accounting for less than 40%). pH is projected to decrease across the shelf with lowest values in hypoxic waters where aragonite saturation will approach the saturation limit. In the model simulations, acidification is primarily driven by atmospheric and offshore CO 2 levels, while the enhancement in stratification only accounts for 7% or less of the total change in pH. Decreased buffering capacity and increased stratification in the future will enhance respiration‐induced acidification (i.e., a decrease in bottom water pH by respired CO 2 ), which will amplify the climate‐induced acidification. According to the model, the magnitude of future changes varies significantly from year to year. The largest effects are simulated in years with large freshwater discharge and upwelling‐favorable winds.