During the twentieth century, sea level rose 20 cm. It is predicted that sea level rise will accelerate during the twenty-first century, but many model predictions still foresee a sea level rise of less than 1 additional meter by 2100.
Regardless of the time scale involved, an analogy to the previous interglacial suggests that a few degrees Celsius of sustained warming can cause enough melting to raise sea level 4-6 m before the ice sheets reach equilibrium. This level of warming is likely to be achieved or even exceeded by 2100 in the absence of intervention to combat climate change, though as above, it would take far longer to realize the full sea level change.
Paul Blanchon and his team have uncovered evidence of extremely rapid sealevel rise 121,000 years ago in one of the warm interglacial periods. Basically by dating coral skeletons at a place called Xcaret (the beautiful place where a fossil Reef lies exposed), Paul was able to document an abrupt reef crest “back stepping” (essentially the reef crest suddenly appearing landward in a very short time). The abrupt loss of the lower reef crest growth but continued growth between the lower and upper reef crests has allowed these paleobiologist to draw the conclusion that this occurred due to a 2-3 m sea level rise. What is the big news, is that it happened over decades. Measurements of the upward growth of some corals at the “ocean surface” occurred at about 36 mm per year!
Paul is scientist who is characterised by rigour and excellence. He is based at Institute of Marine Sciences and Limnology (ICML) of the National Autonomous University of Mexico (UNAM) in Puerto Morelos on the Yucatan Peninsula. As a paleobiologist, he is interested in how the world has changed over thousands of years. For a long time now, Paul has been gathering evidence the great ice sheets the world can break up suddenly over very short period of times. This latest paper is further evidence of the veracity of this idea – follow this link to see the article in Nature.
16 April 2009
An interglacial jump in sea level
The potential for future rapid sea-level rise is perhaps the greatest threat from global warming. But the question of whether recent ice loss from Greenland and Antarctica is the first indication of such a rise is difficult to answer given the limited duration of the instrumental record. New evidence from an exceptionally exposed fossil reef in the Xcaret theme park in Mexico provides a detailed picture of the development of reef terraces, erosion surfaces and sea-level excursions in the region during the last interglacial. A combination of precise uranium-series dating and stratigraphic analysis, together with comparison with coral ages elsewhere, suggests that a sea-level jump of 2 to 3 metres occurred about 121,000 years ago, consistent with an episode of ice-sheet instability towards the end of the last interglacial. On that evidence, sustained rapid ice loss and sea-level rise in the near future are possible.