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The Southern Hemisphere is Stormier Than the Northern, and We Finally Know Why
UChicago research offers first concrete explanation for difference, and show it is getting even stormier over time [uchicago.edu]:
For centuries, sailors who had been all over the world knew where the most fearsome storms of all lay in wait: the Southern Hemisphere. "The waves ran mountain-high and threatened to overwhelm [the ship] at every roll," wrote one passenger on an 1849 voyage rounding the tip of South America.
Many years later, scientists poring over satellite data could finally put numbers behind sailors' intuition: The Southern Hemisphere is indeed stormier than the Northern, by about 24%, in fact. But no one knew why.
A new study led by University of Chicago climate scientist Tiffany Shaw lays out the first concrete explanation for this phenomenon. Shaw and her colleagues found two major culprits: ocean circulation and the large mountain ranges in the Northern Hemisphere.
The study also found that this storminess asymmetry has increased since the beginning of the satellite era in the 1980s. The increase was shown to be qualitatively consistent with climate change forecasts from physics-based models.
[...] Looking over past decades of observations, they found that the storminess asymmetry has increased over the satellite era beginning in the 1980s. That is, the Southern Hemisphere is getting even stormier, whereas the change on average in the Northern Hemisphere has been negligible.
[...] It may be surprising that such a deceptively simple question—why one hemisphere is stormier than another—went unanswered for so long, but Shaw explained that the field of weather and climate physics is relatively young compared to many other fields.
But having a deep understanding of the physical mechanisms behind the climate and its response to human-caused changes, such as those laid out in this study, are crucial for predicting and understanding what will happen as climate change accelerates.
Journal Reference:
Tiffany A. Shaw, Osamu Miyawaki, and Aaron Donohoe, Stormier Southern Hemisphere induced by topography and ocean circulation, PNAS, 119, 2022. DOI: https://doi.org/10.1073/pnas.2123512119 [doi.org]
