Model simulated change in ocean net primary production after a US-Russia nuclear war in 2020 clouded the skies by depositing 150 Tg of black carbon in the atmosphere. The resulting global cooling and the reduction in surface photosynthetically active radiation (PAR) causes a rapid reduction in NPP In the first few years (panels a-d). In some regions, such as the subpolar North Atlantic highlighted in blue, NPP collapses completely (panel b), while the global reduction amounts to about 50% (panel a). NPP rebounds after about a decade, but does not return to the initial state (panel e). Instead, ocean productivity remains reorganized with some mid-latitude regions experiencing higher productivity (such as the Sargasso Sea highlighted in blue). Credit: Harrison et al., 2022, Figure 1
Source: AGU Advances
Editors’ Highlights are summaries of recent papers by AGU’s journal editors.

As the war in the Ukraine reminds us, the threat of a nuclear conflict is real. What consequences would such a war have for life in the ocean? Harrison et al. [2022] report on results from model simulations where they looked at the impact of a large-scale war that would deposit 150 Tg (150 billion kg) of sunlight-absorbing black carbon into the atmosphere. This scenario causes a global-scale cooling of sea-surface temperature of nearly 6°C. Even though the associated deepening of the mixed layer brings additional nutrients to the surface, the lack of light reduces net primary production (NPP) by more than 50% globally, with some regions experiencing a complete collapse of biological productivity. NPP recovers slowly after a decade alongside sea-surface temperature, but does not return to pre-war levels even after many decades. This highlights the long-lasting threats of a nuclear war, especially through the non-linear response of the ocean.

Citation: Harrison, C. S.,  Rohr, T.,  DuVivier, A.,  Maroon, E. A.,  Bachman, S.,  Bardeen, C. G., et al. (2022).  A new ocean state after nuclear war. AGU Advances,  3, e2021AV000610.

—Nicolas Gruber, Editor, AGU Advances

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