September 16, 2009 – Original Source: Climate Feedback, Nature Magazine. By Kerri Smith
The Greenland ice sheet melted much more rapidly as a result of warmer temperatures in the recent past than previously estimated, a team of international scientists has revealed. They warn that future warming could have more dramatic effects on the ice than researchers have assumed. The research is from this week’s Nature and there’s a news story about it over at Nature News.
This study is the latest in a series to use data from ice cores to fathom out what was going on in Greenland’s climatic past. Between 9,000 and 6,000 years ago, Earth went through an unusually warm period. But puzzlingly, unlike data from many other spots in the Northern Hemisphere, measurements of isotopes in ice cores drilled from the Greenland ice sheet haven’t reflected that temperature change. So models of the ice sheet’s behaviour based on these data have suggested that the height of the ice sheet has remained quite stable during the past 12,000 years.
Now, new data from ice cores drilled in six different places on and around the ice sheet reveal that this unusually warm period affected the GIS too, and that in response to these temperatures — which were 2–3 °C hotter than our current temperature — it lost 150 metres in height at its centre and shrank by 200 kilometres at the edges.
The team was led by Bo Vinther and other scientists from the Ice and Climate team at the Niels Bohr Institute at the University of Copenhagen. Says Bo in the story and in a related interview on the Nature Podcast this week: “When the temperatures were something like 2-3 degrees warmer than they are now in Greenland, then the ice sheet was melting quite rapidly. And that of course gives us an indication that if climate was to warm a few degrees, then the ice sheet might start to lose mass again.”
Also on Nature News this week, there’s a Q&A with Dorthe Dahl-Jensen, also a co-author on Vinther’s paper. She is part of a new effort, the North Greenland Eemian Ice Drilling project, which this year beat previous depth records for drilling in the ice. They have the same aims – drill down to figure out past climate by analysing isotopes and air bubbles in the ice cores.