A remarkable paper coming in the Jan. 31 issue of Geophysical Research Letters has a title that says it all: “Abrupt onset of the Little Ice Age triggered by volcanism and sustained by sea-ice/ocean feedbacks.”
The paper uses evidence and modeling to explain how the sun-blocking impact from a 50-year stretch of unusually intense eruptions of four tropical volcanoes caused sufficient cooling to produce a long-lasting shift in the generation and migration of Arctic Ocean sea ice, with substantial consequences for the Northern Hemisphere climate that lasted centuries and left a deep imprint on European history. [More from Richard Black of the BBC.*]
The driver of the larger-scale shifts was the impact of increased flows of Arctic sea ice on the North Atlantic Ocean, as a news release from the American Geophysical Union, which publishes the journal, describes:
Since sea ice contains almost no salt, when it melted the surface water became less dense, preventing it from mixing with deeper North Atlantic water. Without mixing taking place, the water that flowed back to the Arctic was colder, helping sustain large areas of sea ice and creating a self-sustaining feedback loop long after the effects of the volcanic aerosols subsided…. [Read the rest.]
The research, ranging from fieldwork on the remains of Arctic plants on Baffin Island to supercomputer climate simulations at the National Center for Atmospheric Research, was led by Gifford H. Miller, a geologist affiliated with the University of Colorado, Boulder, and Institute of Earth Sciences of the University of Iceland, Reykjavik.
I’m sending the paper around for reactions from a variety of climate researchers. [The findings are relevant to efforts to clarify how a warming prod from greenhouse gases could, through similar mechanisms, change large-scale climate patterns around the Northern Hemisphere. The research also is important to consider in gauging any effort to geo-engineer the climate using sun-blocking aerosols.*] Stay tuned for more.
| *Bracketed sections are updates. |