The effect of volcanic eruptions on the North Atlantic ocean temperatures over the past millennium (800–2000 AD)

Abstract:

Several studies suggest that the North Atlantic Ocean is of particular importance for the climate variability, especially that of western Europe (Schlesinger M. E. & Ramankutty 1994, Knight J., Folland C. K. & Scaife A. 2006). The changes in North Atlantic sea surface temperatures are related to the thermohaline's circulation strength (Kushnir Y., 1994) and affected by volcanic eruptions (Church J.A, White N.J. & Arblaster J.M. 2005), due to their release of aerosols into the stratosphere.

In this study we examine the signal of tropical volcanic eruptions in the temperatures of the North Atlantic Ocean in various depths (6, 100, 560 and 3070 m from the sea surface), for the past millennium. The temperatures are derived from the comprehensive COSMOS Earth System Model (ECHAM5-OM at T30 spatial resolution) and are presented for a control run and for three fully forced ensemble simulations including changes in orbital, solar, volcanic, land use and greenhouse gas changes.

The model shows a response in the years following volcanic eruptions, being mostly pronounced after the large eruptions that took place between 1200 and 1300 AD, as well as at the beginning of the 19^thcentury. The strongest impact on the ocean temperatures, due to the increased atmospheric optical depth, is evident in the uppermost level, especially for two out of the three ensemble simulations. In these simulations a pronounced decrease in the ocean temperature between 1400 and 1500 AD is observed due to the increase of the aerosol effective radius. In the mixed ocean layers the response to volcanic aerosols is more obvious in the third ensemble simulation, whereas in the deep ocean the temperatures do not seem to be strongly affected by volcanic eruptions.

Schlesinger, M. E. & Ramankutty, N. An oscillation in the global climate system of period 65–70 years. Nature 367, 723–726 (1994).

Kushnir, Y. Interdecadal variations in North Atlantic sea surface temperature and associated atmospheric conditions. J. Clim. 7, 141–157 (1994).

Knight, J., Folland, C. K. & Scaife, A. Climate impacts of the Atlantic multidecadal oscillation. Geophys. Res. Lett. 33, L17706 (2006)

Church J.A, White N.J. & Arblaster J.M. Significant decadal-scale impact of volcanic eruptions on sea level and ocean heat content. Nature 438, 74-77 (2005)