Session: Last Millennium & Past2K
Author: Laura Sobral Verona / email@example.com / Ocenographic Institute of University of São Paulo (IO/USP)
Co-author: Ilana Wainer, Ocenographic Institute of University of São Paulo (IO/USP);
Quantifying how much the climate system is impacted by natural forcing is a key aspect for understanding how the Earth´s climate system is changing. Volcanism is the cause of great non-anthropogenic perturbations on the Earth climate through energy imbalance changes. Which occurs due to injection of sulfuric gases (e.g. SO2 and H2S) in the stratosphere that interacts with the incoming radiation. Thereby causing surface and low troposphere cooling. The climate effects of great volcanic eruptions have been studied mostly for the Northern Hemisphere. There is still much to be uncovered relative to the impacts on the Southern Hemisphere, even more with respect to the Southern Ocean.
The South Atlantic and its Southern Ocean sector response to volcanism are examined using simulation results from the Last Millennium Ensemble Experiment of the Community Earth System Model version 5 (CESM-CAM5-LME), for the period ranging 850-2005. With a composite analysis and Wilcoxon Rank-Sum test, we evaluate significant changes in the air-sea properties due to great tropical and southern eruptions.
The sea surface temperature and salinity anomaly pattern change in the first austral summer (DJF) following the eruption. North of 60S, SST gets ~0.6C colder, as expected because of the higher albedo. Contrarily, near the Antarctic Peninsula we observe a local warming of approximately 0.4C, significant at the 90% level. All surface anomalies seem to disappear after the 5th subsequent year eruptions compared to the composite average of the years before the event. The same happens with the surface salinity. There are not significant changes in the explosion year. However, from the first to the 4th subsequent DJF, a positive salinity anomaly (~0.1) is observed in the northern region off Antarctic Peninsula. On the other hand, volcanism impacts on the associated zonal wind stress are faster. The greatest anomaly is observed during the DJF of the volcano explosion year, which generates an increased zonal gradient.