Giant boulders and Last Interglacial storm intensity in the North Atlantic

As global climate warms and sea level rises, coastal areas will be subject to more frequent extreme flooding and hurricanes. Geologic evidence for extreme coastal storms during past warm periods has the potential to provide fundamental insights into their future intensity. Recent studies argue that...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences
Main Authors: Rovere A, Casella E, Harris DL, Lorscheid T, Nandasena NAK, Dyer B, Sandstrom RM, Stocchi P, D’Andrea W.J, Raymo M R
Other Authors: Rovere, A, Casella, E, Harris, Dl, Lorscheid, T, Nandasena, Nak, Dyer, B, Sandstrom, Rm, Stocchi, P, D’Andrea, W. J., Raymo, M R
Format: Article in Journal/Newspaper
Language:English
Published: 2017
Subjects:
North Atlantic
Online Access:https://hdl.handle.net/11576/2726018
https://doi.org/10.1073/pnas.1712433114
Description
Summary:As global climate warms and sea level rises, coastal areas will be subject to more frequent extreme flooding and hurricanes. Geologic evidence for extreme coastal storms during past warm periods has the potential to provide fundamental insights into their future intensity. Recent studies argue that during the Last Interglacial (MIS 5e, similar to 128-116 ka) tropical and extratropical North Atlantic cyclones may have been more intense than at present, and may have produced waves larger than those observed historically. Such strong swells are inferred to have created a number of geologic features that can be observed today along the coastlines of Bermuda and the Bahamas. In this paper, we investigate the most iconic among these features: massive boulders atop a cliff in North Eleuthera, Bahamas. We combine geologic field surveys, wave models, and boulder transport equations to test the hypothesis that such boulders must have been emplaced by storms of greater-than-historical intensity. By contrast, our results suggest that with the higher relative sea level (RSL) estimated for the Bahamas during MIS 5e, boulders of this size could have been transported by waves generated by storms of historical intensity. Thus, while the megaboulders of Eleuthera cannot be used as geologic proof for past "superstorms," they do show that with rising sea levels, cliffs and coastal barriers will be subject to significantly greater erosional energy, even without changes in storm intensity.

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