Research from the Woods Hole Oceanographic Institution (WHOI) has reconstructed the patterns of historical tropical cyclones in order to improve our understanding of how climate change will likely affect cyclones in the coming years. The findings are published in Nature Geoscience and show that tropical cyclones during the Little Ice Age (when temperatures in the Northern Hemisphere were cooler) occurred more frequently in the southern Marshall Islands than they do today.
According to lead author, James Bramante of the MIT-WHOI Joint Program in Oceanography/Applied Ocean Science and Engineering, their findings illustrate the impacts that differential ocean warming have on atmospheric circulation and resulting weather patterns such as cyclones. Bramante explains that during the Little Ice Age, different parts of the Pacific Ocean experienced unique changes in storm patterns, a phenomenon that we should anticipate in our planet’s future years, but in reverse:
"Atmospheric circulation changes due to modern, human-induced climate warming are opposite of the circulation changes due to the Little Ice Age," notes Bramante. "So, we can expect to see the opposite effect in the deep tropics -- a decrease in tropical cyclones close to the equator. It could be good news for the southern Marshall Islands, but other areas would be threatened as the average location of cyclone generation shifts north," he adds.
To come to these conclusions, Bramante reconstructed 3,000 years of storm history on Jaluit Atoll in the southern Marshall Islands, the hotspot location for tropical cyclones in the western North Pacific. His radiocarbon dating analysis on sediment size showed that tropical cyclones occurred in the region approximately once a century, yet during the Little Ice Age they rose to a maximum of four per century.
Jeff Donnelly, Bramante’s co-author and a WHOI senior scientist, had previously conducted similar analyses to reconstruct the history of hurricanes in the North Atlantic and Caribbean. He echoes the sentiment that these types of reconstruction are essential for understanding of how storms may behave in the future.
"Through the geologic archive, we can get a baseline that tells us how at-risk we really are at any one location," Donnelly says. "It turns out the past provides some useful analogies for the climate change that we're currently undergoing. The earth has already run this experiment. Now we're trying to go back and determine the drivers of tropical cyclones."