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- Title
Sudden Reduction of Antarctic Sea Ice Despite Cooling After Nuclear War.
- Authors
Coupe, Joshua; Harrison, Cheryl; Robock, Alan; DuVivier, Alice; Maroon, Elizabeth; Lovenduski, Nicole S.; Bachman, Scott; Landrum, Laura; Bardeen, Charles
- Abstract
A large‐scale nuclear war could inject massive amounts of soot into the stratosphere, triggering rapid global climate change. In climate model simulations of nuclear war, global cooling contributes to an expansion of sea ice in the Northern Hemisphere. However, in the Southern Hemisphere (SH), an initial expansion of sea ice shifts suddenly to a 30% loss of sea ice volume over the course of a single melting season in the largest nuclear war simulation. In smaller nuclear war simulations an expansion in sea ice is instead observed which lasts for approximately 15 years. In contrast, in the largest nuclear war simulation, Antarctic sea ice remains below the long term control mean for 15 years, indicating a threshold that must be crossed to cause the response. Declining sea ice in the SH following a global cooling event has been previously attributed to shifts in the zonal winds around Antarctica, which can reduce the strength of the Weddell Gyre. In climate model simulations of nuclear war, the primary mechanisms responsible for Antarctic sea ice loss are: (a) enhanced atmospheric poleward heat transport through teleconnections with a strong nuclear war‐driven El Niño, (b) increased upwelling of warm subsurface waters in the Weddell Sea due to changes in wind stress curl, and (c) decreased equatorward Ekman transport due to weakened Southern Ocean westerlies. The prospect of sudden Antarctic sea ice loss after an episode of global cooling may have implications for solar geoengineering and further motivates this study of the underlying mechanisms of change. Plain Language Summary: Firestorms from a global nuclear war would generate large amounts of smoke that could enter the Earth's atmosphere and block sunlight. Climate model simulations that inject smoke into the upper atmosphere confirm that this smoke causes rapid global cooling leading to increased sea ice in the Northern Hemisphere. However, sea ice in the Southern Hemisphere actually shrinks in the 2–6 years after a very large nuclear war, mainly caused by a change in the winds around Antarctica. Smoke heats the upper atmosphere and the westerly winds around Antarctica shift closer to the coast. The wind shift causes Ekman transport of the top layer of the ocean away from the coast, which brings up relatively warm water from below, melting sea ice during summer and inhibiting sea ice growth during the winter. A similar response has been found in simulations of supervolcano eruptions. As greenhouse gasses continue to warm up the Earth's oceans, a global cooling event that triggers a similar wind shift may lead to greater reductions in Antarctic sea ice. Key Points: A sudden reduction in Antarctic sea ice occurs despite global cooling after nuclear war in climate model simulationsThe sea ice changes in response to dynamic changes in atmospheric and oceanic circulationEven in a nuclear winter, Antarctic sea ice is vulnerable to wind shifts that cause upwelling of water onto the continental shelf
- Subjects
ANTARCTICA; SEA ice; NUCLEAR warfare; ANTARCTIC ice; VOLCANIC eruptions; WESTERLIES; GLOBAL cooling; CLIMATE change
- Publication
Journal of Geophysical Research. Oceans, 2023, Vol 128, Issue 1, p1
- ISSN
2169-9275
- Publication type
Article
- DOI
10.1029/2022JC018774