Traces of meteoritic impact in ice cores?

Hi Ice and Climate researchers

I'd be very interested to know if the ice-core showed any evidence confirming the newly-published details of the 'micro-diamond layer' from the explosion of a meteorite over the Great Lakes, melting the glacier there some time before the 'golden spike'.

Is there thought to be a connection?
 
Regards 
J. T.

Answer from ice core researcher Jørgen Peder Steffensen, Ph.D. Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen

We are aware that a meteoritic impact might have occurred close to the end of the last glacial period. However, the time is a bit uncertain. Some suggest the impact has occurred around 12,700 B.P. and that it could have been the trigger of the Younger Dryas cold event. So at present the dating of the impact - if it occurred at all - is too uncertain to connect it to any climate system change. So far nobody have detected any "unusual" layers in the ice cores, marking a possible meteoritic impact.

The 11,700 last glacial termination, or golden spike, is defined as the last year where glacial weather conditions existed over the Greenland Ice Sheet. The ice age as such reached it's culmination with maximum glacier ice extent and minimum sea levels around 25,000 - 20,000 years ago. Already 17,500 years ago the Canadian and Scandinavian ice sheets had retreated significantly.

All through the last glacial period climate in the North has been flipping between very cold and just plain cold. 26 of these "flips" have been recorded in the ice cores, and we believe that the Younger Dryas and thus also the very last termination of the glacial was one of these "flips". The flips are called stadial-interstadial oscillations and they are part of the bi-polar climate see-saw. We doubt therefore, that the Younger Dryas and the Glacial Termination have been caused by a meteor, because it is difficult to imagine 26 similar meteors causing all the other flips. 

In 1965 the biggest meteorite to hit Britain was
heading for the East Midlands village of Barwell.
(Credit: BBC)

We are quite a few ice core people that are interested in the issue of meteoritic impacts. We are on the outlook for a parameter, or a set of parameters that will enable us to find and identify meteor events, just as we are able to do with volcanic eruptions.

A lot of people have searched in several ice cores for traces of the early 20th century Tunguska meteoritic explosion, so far no conclusive evidence has been found. The issue is interesting.

Best regards
Jørgen Peder Steffensen, Ph.D. Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen