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Predicted Effects of Climate Change on Northern Gulf of Mexico Hypoxia
Citation:
Lehrter, J., D. Ko, L. Lowe, AND B. Penta. Predicted Effects of Climate Change on Northern Gulf of Mexico Hypoxia . Chapter 8, Modeling Coastal Hypoxia: Numerical Simulations of Patterns, Controls, and Effects of Dissolved Oxygen Dynamics. Springer, New York, NY, , 173-214, (2017).
Impact/Purpose:
The purpose is to investigate via numerical modeling the potential impacts of a future climate on northern Gulf of Mexico hypoxia. The future scenario is developed from the IPCC (2014) report and other published literature.
Description:
We describe the application of a coastal ocean ecosystem model to assess the effect of a future climate scenario of plus (+) 3 °C air temperature and + 10% river discharge on hypoxia (O2 < 63 mmol m−3) in the northern Gulf of Mexico. We applied the model to the Louisiana shelf as influenced by the runoff from the Mississippi River basin. The net effect of the future climate scenario was a mean increase in water temperature of 1.1 °C and a decrease in salinity of 0.09 for the region of the shelf where hypoxia typically occurs (<50 m depth). These changes increased the strength of water column stratification at the pycnocline and increased phytoplankton biomass. In the future scenario, the hypoxic area was only 1% larger than the present. A more significant effect was in the duration and extent of severe hypoxic areas. Severe hypoxic areas, defined as model cells having hypoxia for more than 60 days in the year, had a mean increase in hypoxia duration of 9.5 days (a 10% increase). The severely hypoxic area also increased by 1,130 km2 (an 8% increase) in the future scenario. The results confirm that a warmer and wetter future climate will, on average, worsen the extent and duration of hypoxia in this system. Thus, it is probable that long-term Mississippi River nutrient management for hypoxia will need to be adapted for climate change.
