Modeling the volcanic aerosol distribution and climatic response of high-latitude volcanic eruptions.

摘要

High-latitude volcanic eruptions can significantly impact the climate system. Simulations were conducted with the Goddard Institute for Space Studies (GISS) modelE general circulation model of the Katmai (58°N) as well as one with 3x the optical depth of Katmai (3x Katmai), and the Laki (64°N) eruption to determine the climate response of high-latitude volcanic eruptions. I have found that high-latitude Northern Hemisphere volcanic eruptions, unlike tropical eruptions, do not have strong impacts on winter atmospheric circulation. Also, I have found that they weaken the summer Indian and African monsoon, reducing precipitation over India and northern Africa, and reducing the flow of major African rivers. During boreal summer, the strong cooling over the Northern Hemisphere land masses causes a decrease in the temperature gradient between Asia and Europe and the Atlantic and Indian Oceans, which results in weakened monsoon circulations. These simulations show that the radiative impact of a high-latitude volcanic eruption is much larger than the dynamical impact at high latitudes. I conducted simulations of the atmospheric transformation and transport of the emissions from the Laki eruption using the GISS modelE climate model coupled to a sulfur cycle chemistry model. I show for the first time the modeled areal distribution of sulfate deposition following the Laki eruption, compared to 23 ice cores taken across Greenland. These simulations show that the majority of the deposition of Laki to the Greenland ice sheet occurs during the latter half of 1783. Also, I offer an explanation for an ice core study which dated Laki sulfate as being deposited in 1784. The Laki eruption climate model runs reproduce the extensive radiative cooling (-1 to -3°C) that occurred during the summer of 1783 across much of Asia, Canada, and Alaska. In the winter of 1783-1784 our model reproduces the significant negative temperature anomalies over the Northeastern United States, but only slight cooling was produced over Europe.