Thursday, April 16, 2009

Old signs of catastrophic sea level rise

Quirin Schiermeier in Climate Feedback: …That the global sea-level can rise by almost half a metre per decade when huge glaciers melt towards the end of an ice age has already been known. But a paper in Nature today (Editor’s summary) suggests that a similar jump has occurred at the close of the sea-level ‘highstand’ during the warm period, the Eemian Interglacial.

The team, led by Paul Blanchon of the National Autonomous University of Mexico in Cancun, analyzed the age structure of exceptionally well-exposed coral reefs at Xcaret, a popular theme park on the northeast Yucat√°n peninsula. Because no earthquakes have occurred in the more recent geological history of the region, the peninsula is an ideal location to study sea-level behaviour.

The team found that at the end of the last interglacial many reefs were flooded and replaced by new reefs on higher ground. Age and layering of the corals indicate that a rapid 2-3 metres jump in sea-level occurred around 121,000 years ago, possibly within less than one century. Only swift and substantial melting of Greenland and Antarctic ice sheets can explain the extreme rate at which the seal level rose to its highstand some 4-6 metres above today’s sea-level.

The implications for our warming planet are clear. As modern temperatures approach those at the height of the Eemian Interglacial, the rate of seal-level rise could soon – perhaps very soon - shift gear, from modest to catastrophic. The spectacular break-up of the Wilkins Ice shelf off the Antarctic Peninsula is a reminder that we are getting closer to the point where things could get really nasty....

Waves crashing at Pancake Rocks near Punakaiki, New Zealand, shot by Alexander Klink, Wikimedia Commons, under the Creative Commons Attribution 3.0 Unported License

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