Warm summers melted ice age

Written by Press Trust of India | London | Updated: Aug 26 2009, 05:34am hrs
It wasnt only warm summers in the northern hemisphere, but also in the southern hemisphere that melted the ice age, a new study has revealed.

An international team, led by Russell Drysdale of Newcastle University, has found that warm summers in both the northern and southern hemispheres may have ended the ice age, the Science journal reported. Previous research had identified precisely when these orbital wobbles occurred, but it had not been possible to accurately date the records of the Earths response to them, which are found in marine sediment on the ocean floors.

Drysdale said ocean sediment cores contain information about past global climate but beyond about 50,000 years ago it is difficult to determine the exact age of sediments.

To overcome this, we studied isotope variations in three stalagmites collected from an Italian cave, and found that these variations relate to ocean temperature changes recorded in sediment cores from the nearby sea floor.

Stalagmites from limestone caves can be very precisely dated using trace amounts of uranium incorporated within their structure. We applied the accurate timescale of the stalagmite record to the sea floor sediment data. A key property of sea-floor sediments is that they detect the growth and decay of ice sheets, Drysdale said.

Drysdale added: So we have effectively provided an accurate timescale for the collapse of the ice sheets that ended the penultimate ice age. This collapse started at around 141,000 years ago.