HR: 09:35h
AN: PP31E-07    [Abstracts]
TI: Impact of Big Tambora Eruption on ENSO, Ocean Heat Uptake, and Sea Level
AU: * Stenchikov, G
EM: gera@envsci.rutgers.edu
AF: Department of Environmental Sciences, Rutgers University, 14 College Farm Rd., New Brunswick, NJ 08901, United States
AU: Ramaswamy, V
EM: V.Ramaswamy@noaa.gov
AF: NOAA Geophysical Fluid Dynamics Laboratory, 201 Forrestal Rd., Princeton, NJ 08540, United States
AU: Delworth, T
EM: Tom.Delworth@noaa.gov
AF: NOAA Geophysical Fluid Dynamics Laboratory, 201 Forrestal Rd., Princeton, NJ 08540, United States
AB: Strong explosive volcanic eruptions could produce global stratospheric aerosol clouds that last for 2-3 years reflecting solar radiation and cooling the earth's surface. The climate response to volcanic impact forms as a result of interaction of associated thermal and dynamic perturbations with the major modes of climate variability. The paleo proxy data even suggest that strong tropical eruptions could increase the likelihood of El Niño. E.g., the strongest explosive events of 19th and 20th centuries, Tambora eruption in 1815 and the Mt. Pinatubo eruption in 1991, occurred in El Niño years. After volcanic impacts surface air temperature relaxes typically for 7 years but cooling accumulated in the ocean can be seen for about a century in the sub-thermocline waters. Decrease of deep ocean temperature is associated with negative anomalies of sea level. This provides a mechanism of how short-term volcanic radiative impacts could produce perturbations in climate system that last for centuries producing a cumulative cooling effect. In this study we have employed a coupled climate model (GFDL CM2.1) for calculating impacts of the Big Tambora, and Pinatubo eruptions. The aerosol cloud of Tambora eruption was about 3 times of that from the Pinatubo eruption therefore it produced much stronger climate effect. Here we consider Tambora climate effect in context of a well observed Pinatubo impact because this adds in confidence of simulation results. To synchronize volcanic eruptions and ENSO we have chosen initial conditions from those years of a control run that exhibited, specific ENSO phase and conducted ten 20-year ensemble runs with El Niño, La Niña, and Neutral initial conditions, for each volcano. We found that maximum cooling for El Niño cases tends to shift to the second year after an eruption therefore notorious Tambora's year without a summer was simulated in 1816 as observed. In La Niña cases maximum cooling appears in the year when eruption occurred. In the runs with El Nino initial conditions volcanic cooling decreases amplitude of El Nino but causes dynamic warming of the equatorial SST in the year following an El Nino event. In the runs with the neutral initial conditions volcanic impact tends to produce El Nino-like response in the second year after volcanic eruption that might explain Volcano-El Nino statistical relation, observed in the paleo-data analysis. This robust warming effect gets stronger in the runs with weaker El Nino and with increase of volcanic forcing. Simulated ocean cooling caused by Tambora eruption decreased the mean sea level by about 14 mm versus 5 mm after the Pinatubo eruption. The later figure agrees well with Church et al. (2005). Because of extremely long relaxation time of ocean subsurface temperature the perturbations caused by Tambora eruption could affect climate state in the mid 19th century used to initiate IPCC AR4 simulations. The sea level decrease forced by Tambora eruption might have to be accounted for estimating the sea level trends caused by Global Warming.
DE: 0370 Volcanic effects (8409)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1641 Sea level change (1222, 1225, 4556)
DE: 4928 Global climate models (1626, 3337)
DE: 8408 Volcano/climate interactions (1605, 3309)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting