The Role of Volcanic Activity in Climate and Global Change

Volcanic activity is an important natural cause of climate variations because tracer constituents of volcanic origin impact the atmospheric chemical composition and optical properties. Volcanic eruptions force all elements of the climate system, producing long-term climate signals in ocean. At present, a weak volcanic activity results in gas and particle effusions in the troposphere (lower part of atmosphere), which constitute, on an average, the larger portion of volcanic mass flux into the atmosphere. However, the products of tropospheric volcanic emissions are short-lived and contribute only moderately to the emissions from large anthropogenic and natural tropospheric sources. Chemical transformations and gasto-particle conversion of volcanic tracers form a volcanic aerosol layer that remains in the stratosphere for 2-3 years after an eruption, thereby impacting the Earth's climate, because volcanic aerosols cool the surface and the troposphere by reflecting solar radiation, and warm the lower stratosphere, absorbing thermal IR and solar near-IR radiation. Volcanic eruptions produce long-term impacts on the ocean's subsurface temperature and steric height that accumulate at the current frequency of explosive volcanic events. The vertical distribution of the ocean temperature change signal is asymmetric at high latitudes. A cooling signal penetrates to depth at high southern latitudes, while a warming signal penetrates to depth at high latitudes of the Northern Hemisphere. This chapter focuses on recently discovered forced stratosphere-troposphere dynamic interaction and long-term ocean response to volcanic forcing. © 2009