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Tropical storms pose a significant risk to coastal populations, including those throughout the Caribbean and along the Atlantic and Gulf coasts of North America. The impact of climate change on tropical storms is multifaceted, and patterns of sea surface temperature (SST) change may play a role in shaping future tropical storm risk. While the SST fingerprints associated with changes in the Atlantic Meridional Overturning Circulation (AMOC) may be uncertain, the North Atlantic Warming Hole (NAWH) and enhanced SST warming near the Gulf Stream are robust features of both past and projected future climate change. Here we use the Community Earth System Model version 2 (CESM2) to highlight the remote contributions of both of these potential SST fingerprints of AMOC decline to changes in tropical cyclone (TC) genesis potential in the Atlantic basin, and thus to uncertainty in future coastal climate risk. Both the NAWH and enhanced warming near the Gulf Stream lead to significant changes in TC genesis potential, particularly in the western North Atlantic (between Bermuda and the Bahamas), the northeastern Gulf of Mexico and the Caribbean Sea, where changes are on the order of ±10% over the full Atlantic hurricane season, with considerably stronger responses focused in the two halves of the season. Diagnosis of the Genesis Potential Index (GPI) indicates that changes in mid-tropospheric humidity and vertical wind shear are the most important factors driving these responses. The simulated changes in GPI occur in regions of considerable historical TC genesis, highlighting the need to further understand the historical and projected future patterns of SST change in the North Atlantic Ocean, including their relationship to AMOC and its potential decline.
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Enhanced precipitation in the Gulf of Mexico during the Eocene − Oligocene transition driven by interhemispherical temperature asymmetry
Studies reveal that the sea-surface temperature (SST) of the Northern Hemisphere decreased at a smaller amplitude than that of the Southern Hemisphere during the Eocene−Oligocene transition (EOT). This interhemispheric temperature asymmetry has been associated with intensified Atlantic Meridional Overturning Circulation (AMOC) that may have driven enhanced precipitation and weathering in low latitudes and the subsequent drawdown of atmospheric carbon dioxide. However, no quantitative constraints on paleo-precipitation have been reported in low latitudes to characterize the AMOC effect across the EOT. Here, we present the results of high-resolution (ca. 6 k.y. per sample) isotopic and biomarker records from the Gulf of Mexico. Reconstructed precipitation using leaf wax carbon isotopes shows an increase of 44% across the EOT (34.1−33.6 Ma), which is accompanied by a secular increase in SST of ∼2 °C during the latest Eocene. We attribute the enhanced precipitation in the Gulf of Mexico to the northward shift of the Intertropical Convergence Zone that was driven by an enlarged polar-tropic temperature gradient in the Southern Hemisphere and an invigorated AMOC. Our findings link changes in meridional temperature gradient and large-scale oceanic circulation to the low-latitude terrestrial hydroclimate and provide paleohydrological evidence that supports CO2-weathering feedback during the EOT “greenhouse” to “icehouse” transition.
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- Award ID(s):
- 2022282
- PAR ID:
- 10324079
- Date Published:
- Journal Name:
- GSA Bulletin
- ISSN:
- 0016-7606
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1130/B36103.1
