Increased sea surface cooling from hurricanes observed along the Southeast Coast of the United States in recent decades

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Changes in Tropical cyclone (TC) cold wakes with respect to distance from coast within 500 km of the U.S. (a) Southeast coast (SEC) and (b) Gulf coast during the period 1982–1999 (blue), 2000–2020 (yellow). Nearshore Atlantic hurricane track locations within 200 km of the U.S. (c) SEC and (e) Gulf coast. Blue dots represent the period 1982–1999 and yellow dots represent the period 2000–2020. Probability distributions of sea surface temperature cooling for the periods 1982–1999 (blue), 2000–2020 (yellow) and their difference (gray) in the near coastal regions (within 200 km) of the U.S. (d) SEC and (f) Gulf coast. The mean TC cold wake magnitude for each period, their difference and the p-value for statistical significance based on a Student's t-test are also shown. Credit: Geophysical Research Letters (2024). DOI: 10.1029/2024GL110087

Utilizing satellite observations and ocean reanalysis datasets, researchers have analyzed the change in sea surface cooling induced by hurricanes and the corresponding ocean-atmosphere environment along the Gulf and Southeast coastal regions of the United States.

The study, published in the journal Geophysical Research Letters, found the magnitude of sea surface cooling increased by about 0.20 °C in the nearshore regions of the Southeast Coast over the period 1982–2020. However, there was no significant change in storm-induced cooling along the Gulf Coast, which highlights the regional nature of these responses to global warming.

To gain a mechanistic understanding of the physical processes responsible for the enhanced hurricane cold wakes near the Southeast United States, investigators used ocean reanalysis datasets. An examination of the oceanic environment revealed that the increased magnitude of cold wakes along the Southeast Coast has likely resulted from a cooling of subsurface waters in that region. Further analysis suggests that the latter can be attributed to an increase in pressure gradient across the land–sea boundary.

This results in a strengthening of alongshore winds, which in turn increases upwelling of colder subsurface water. The findings from the Coupled Model Intercomparison Project Phase 6 (CMIP6) models indicate that anthropogenic forcings are likely driving these changes in the atmospheric circulation along the Southeast Coast. These findings shed light for the first time on how interactions between hurricanes and upper-ocean conditions are changing under a warming climate near the U.S. Southeast Coast.

More information: Effy B. John et al, Observed Increase in Tropical Cyclone‐Induced Sea Surface Cooling Near the U.S. Southeast Coast, Geophysical Research Letters (2024). DOI: 10.1029/2024GL110087

Journal information: Geophysical Research Letters

Provided by Pacific Northwest National Laboratory