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Wednesday, March 2, 2011

S. Tietsche et al., Geophys. Res. Lett., 38 (2011), Recovery mechanisms of Arctic summer sea ice

Geophysical Research Letters, Vol. 38 (2011) L02707; doi: 10.1029/2010GL045698
Recovery mechanisms of Arctic summer sea ice
[Readers, pleaser see comment by Gavin Schmidt below the abstract]

S. Tietsche, D. Notz, J. H. Jungclaus and J. Marotzke
Max Planck Institute for Meteorology, Hamburg, Germany

We examine the recovery of Arctic sea ice from prescribed ice-free summer conditions in simulations of 21st century climate in an atmosphere–ocean general circulation model. We find that ice extent recovers typically within two years. The excess oceanic heat that had built up during the ice-free summer is rapidly returned to the atmosphere during the following autumn and winter, and then leaves the Arctic partly through increased longwave emission at the top of the atmosphere and partly through reduced atmospheric heat advection from lower latitudes. Oceanic heat transport does not contribute significantly to the loss of the excess heat. Our results suggest that anomalous loss of Arctic sea ice during a single summer is reversible, as the ice–albedo feedback is alleviated by large-scale recovery mechanisms. Hence, hysteretic threshold behavior (or a “tipping point”) is unlikely to occur during the decline of Arctic summer sea-ice cover in the 21st century.

The issue is that *if* we reduced emissions and concentrations of anthropogenic greenhouse gases, sea ice would come back, i.e., what is happening is not technically irreversible. However, the recovery is predicated on reducing emissions and concentrations - it is not any kind of prediction. Rather it is a statement about how non-linear the regime is and on whether there are real and large scale tipping points in this system. The whole issue is moot in the absence of emissions reductions. - gavin
Received 1 October 2010; accepted 14 December 2010; published 26 January 2011.
Citation: Tietsche, S., D. Notz, J. H. Jungclaus, and J. Marotzke (2011), Recovery mechanisms of Arctic summer sea iceGeophys. Res. Lett.38, L02707, doi:10.1029/2010GL045698.

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