Arctic sea ice and the tipping point

lead in sea ice

A lead or large crack in the ice opens up in melting summer sea ice. A seasonally ice-free Arctic is likely some time in the future, and will mark the decline of the ice pack and its stabilizing effects on temperatures. Credit: NSIDC

As Arctic sea ice thins and becomes more vulnerable to melting in summer, the data trend indicates that we may eventually see ice-free summers. The question is when. Could it be sooner than we think, because the weakened ice cover has reached a point of no return? A new study suggests that, in fact, there may be no “tipping point.”

Scientists refer to a tipping point as a threshold after which a system changes irreversibly. For sea ice, a tipping point would mean losing so much ice that its heat-reflecting effects are severely diminished, leading to more and more ice loss. With this vicious cycle in place, ice could not recover to its previous summertime levels. After Arctic sea ice hit a record low in 2007, some scientists considered the possibility that sea ice has already passed this tipping point.

The January study by researchers at the Max Planck Institute in Germany suggested that sea ice could recover quickly, even if all the ice melted in the summer—showing that the feedback effects that would lead to a downward spiral in ice extent may be weaker than suspected.

The new study could be good news for the Arctic. But even without a tipping point, researchers say, Arctic sea ice will likely continue on its downward trend. As climate change continues, the warmer air and ocean will continue to melt the sea ice.

For more information on the topic, read NSIDC Director Mark Serreze’s view in Nature: News & Views.

References:
Serreze, M. C. 2011. Climate change: Rethinking the sea-ice tipping point. Nature 471, 47–48, doi:10.1038/471047a.

Tietsche, S., Notz, D., Jungclaus, J. H. & Marotzke. 2011. Recovery mechanisms of Arctic summer sea ice. J. Geophys. Res. Lett. 38, L02707, doi:10.1029/2010GL045698.

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