The Potential Impact of Nuclear Conflict on Ocean Acidification

We demonstrate that the global cooling resulting from a range of nuclear conflict scenarios would temporarily increase the pH in the surface ocean by up to 0.06 units over a 5-year period, briefly alleviating the decline in pH associated with ocean acidification. Conversely, the global cooling dissolves atmospheric carbon into the upper ocean, driving a 0.1 to 0.3 unit decrease in the aragonite saturation state (Ωarag) that persists for ∼10 years. The peak anomaly in pH occurs 2 years post conflict, while the Ωarag anomaly peaks 4- to 5-years post conflict. The decrease in Ωarag would exacerbate a primary threat of ocean acidification: the inability of marine calcifying organisms to maintain their shells/skeletons in a corrosive environment. Our results are based on sensitivity simulations conducted with a state-of-the-art Earth system model integrated under various black carbon (soot) external forcings. Our findings suggest that regional nuclear conflict may have ramifications for global ocean acidification

Immediate and Long-Lasting Impacts of the Mt. Pinatubo Eruption on Ocean Oxygen and Carbon Inventories

Large volcanic eruptions drive significant climate perturbations through major anomalies in radiative fluxes and the resulting widespread cooling of the surface and upper ocean. Recent studies suggest that these eruptions also drive important variability in air-sea carbon and oxygen fluxes. By simulating the Earth system using two initial-condition large ensembles, with and without the aerosol forcing associated with the Mt. Pinatubo eruption in June 1991, we isolate the impact of this volcanic event on physical and biogeochemical properties of the ocean. The Mt. Pinatubo eruption forced significant anomalies in surface fluxes and the ocean interior inventories of heat, oxygen, and carbon. Pinatubo-driven changes persist for multiple years in the upper ocean and permanently modify the ocean's heat, oxygen, and carbon inventories. Positive anomalies in oxygen concentrations emerge immediately post-eruption and penetrate into the deep ocean. In contrast, carbon anomalies intensify in the upper ocean over several years post-eruption, and are largely confined to the upper 150 m. In the tropics and northern high latitudes, the change in oxygen is dominated by surface cooling and subsequent ventilation to mid-depths, while the carbon anomaly is associated with solubility changes and eruption-generated El Niño—Southern Oscillation variability. We do not find significant impact of Pinatubo on oxygen or carbon fluxes in the Southern Ocean; but this may be due to Southern Hemisphere aerosol forcing being underestimated in Community Earth System Model 1 simulations

The potential impact of nuclear conflict on ocean acidification

We demonstrate that the global cooling resulting from a range of nuclear conflict scenarios would temporarily increase the pH in the surface ocean by up to 0.06 units over a 5‐year period, briefly alleviating the decline in pH associated with ocean acidification. Conversely, the global cooling dissolves atmospheric carbon into the upper ocean, driving a 0.1 to 0.3 unit decrease in the aragonite saturation state ( &Omega;arag) that persists for &sim;10 years. The peak anomaly in pH occurs 2 years post conflict, while the &Omega;arag anomaly peaks 4‐ to 5‐years post conflict. The decrease in &Omega;arag would exacerbate a primary threat of ocean acidification: the inability of marine calcifying organisms to maintain their shells/skeletons in a corrosive environment. Our results are based on sensitivity simulations conducted with a state‐of‐the‐art Earth system model integrated under various black carbon (soot) external forcings. Our findings suggest that regional nuclear conflict may have ramifications for global ocean acidification. Key Points Nuclear conflict has the potential to increase surface ocean pH and decrease aragonite saturation state The decrease in saturation state would exacerbate shell dissolution from anthropogenic ocean acidification A regional nuclear conflict may have far‐reaching effects on global ocean carbonate chemistry</p

CESM-LE Global Mean SST 1950-2005

<p>Community Earth System Model Large Ensemble (CESM-LE) 1950-2005: global mean sea surface temperatures (SST). Each thin line represents annual means of one of 36 ensemble members, bold line represents mean of all ensemble members. All three volcanic eruptions are seen as temperature drops in 1963 (Agung), 1982 (El Chichón), and 1991 (Mt Pinatubo).</p

Nuclear Niño response observed in simulations of nuclear war scenarios

The climate impacts of smoke from fires ignited by nuclear war would include global cooling and crop failure. Facing increased reliance on ocean-based food sources, it is critical to understand the physical and biological state of the post-war oceans. Here we use an Earth system model to simulate six nuclear war scenarios. We show that global cooling can generate a large, sustained response in the equatorial Pacific, resembling an El Niño but persisting for up to seven years. The El Niño following nuclear war, or Nuclear Niño, would be characterized by westerly trade wind anomalies and a shutdown of equatorial Pacific upwelling, caused primarily by cooling of the Maritime Continent and tropical Africa. Reduced incident sunlight and ocean circulation changes would cause a 40% reduction in equatorial Pacific phytoplankton productivity. These results indicate nuclear war could trigger extreme climate change and compromise food security beyond the impacts of crop failure

Alternate Histories: Synthetic Large Ensembles of Sea-Air CO<SUB>2</SUB> Flux

International audienceWe use a statistical emulation technique to construct synthetic ensembles of global and regional sea-air carbon dioxide (CO2) flux from four observation-based products over 1985-2014. Much like ensembles of Earth system models that are constructed by perturbing their initial conditions, our synthetic ensemble members exhibit different phasing of internal variability and a common externally forced signal. Our synthetic ensembles illustrate an important role for internal variability in the temporal evolution of global and regional CO2 flux and produce a wide range of possible trends over 1990-1999 and 2000-2009. We assume a specific externally forced signal and calculate the rank of the observed trends within the distribution of statistically modeled synthetic trends during these periods. Over the decade 1990-1999, three of four observation-based products exhibit small negative trends in globally integrated sea-air CO2 flux (i.e., enhanced ocean CO2 absorption with time) that are within one standard deviation of the mean in their respective synthetic ensembles. Over the decade 2000-2009, however, three products show large negative trends in globally integrated sea-air CO2 flux that have a low rate of occurrence in their synthetic ensembles. The largest positive trends in global and Southern Ocean flux over 1990-1999 and the largest negative trends over 2000-2009 fall nearly two standard deviations away from the mean in their ensembles. Our approach provides a new perspective on the important role of internal variability in sea-air CO2 flux trends, and furthers understanding of the role of internal and external processes in driving observed sea-air CO2 flux variability