The future of ice sheets and sea ice: Between reversible retreat and unstoppable loss
Edited by Hans Joachim Schellnhuber, Environmental Change Institute, Oxford, United Kingdom, and approved September 22, 2009 (received for review March 3, 2009)
We discuss the existence of cryospheric “tipping points” in the Earth's climate system. Such critical thresholds have been suggested to exist for the disappearance of Arctic sea ice and the retreat of ice sheets: Once these ice masses have shrunk below an anticipated critical extent, the ice–albedo feedback might lead to the irreversible and unstoppable loss of the remaining ice. We here give an overview of our current understanding of such threshold behavior. By using conceptual arguments, we review the recent findings that such a tipping point probably does not exist for the loss of Arctic summer sea ice. Hence, in a cooler climate, sea ice could recover rapidly from the loss it has experienced in recent years. In addition, we discuss why this recent rapid retreat of Arctic summer sea ice might largely be a consequence of a slow shift in ice-thickness distribution, which will lead to strongly increased year-to-year variability of the Arctic summer sea-ice extent. This variability will render seasonal forecasts of the Arctic summer sea-ice extent increasingly difficult. We also discuss why, in contrast to Arctic summer sea ice, a tipping point is more likely to exist for the loss of the Greenland ice sheet and the West Antarctic ice sheet.
dirk.notz@zmaw.de
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1 comment:
Worth reading this one to the end, where the conclusion shows how delicately scientists feel they have to tread when communicating findings.
"Given these results, we believe that researchers should take great care in the public interpretation of the recent retreat of sea ice as a possible tipping point of the climate system, in order not to lose credibility with respect to the possible existence of real climactic tipping points [for the loss of the large sheets covering Greenland and West Antarctica] and their possible far-reaching consequences."
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