Nature Geoscience’s latest issue highlights the challenges of understanding fluctuating sea level – from 70 million years ago to the future (sea level content free to registered users). A collection of commentaries and research papers look at how sea level has changed in the past and try to project its future evolution. In addition, the issue provides insights into some of the societal impacts of sea level change, and how some countries are planning for the future.
Dennis P. Lettenmaier and P. C. D. Milly look at how water on land and small glaciers affect sea level, while Pavel Kabat and the Delta Committee describe the challenges and opportunities facing the Netherlands in the twenty-first century. And Robert Nicholls reviews Orrin Pilkey and Robert Young’s latest book, The rising sea, about changing coastal communities.
Glenn Milne and colleagues sum up the current knowledge about the mechanisms of sea level change past, present and future in a review article.
Looking to the past, Kenneth G. Miller discusses whether early ice sheets on Antarctica drove sea level variations when dinosaurs roamed the Earth. In the ‘more recent’ past, Eelco Rohling and colleagues have reconstructed sea level fluctuations over the past five glacial cycles. They find a very strong correlation between sea level and atmospheric CO2. Applying this relationship to today’s CO2 levels, they find that equilibrium sea level is up to 25 metres higher than present, although they caution that it will take a few millennia for that pan out. For the most recent glacial termination, Jason Briner and colleagues reconstructed the retreat of a Canadian outlet glacier through a fjord, a similar setting as many Greenland outlet glaciers. They found that the bulk of the retreat occurred fairly quickly, and that once the glacier fell back into the deepest part of the fjord, the retreat was irreversible.
In a sobering study of the Mississippi Delta, Mike Blum and Harry Roberts find that the amount of sediment delivered to the delta over the past 12,000 years was almost twice as high as it is today, due to the effects of upstream dams and the construction of levees. They estimate that, even if the sediment delivery is restored, 10,000 square kilometres or more of the delta could be lost by the end of the century, as the sediment compacts and the seas rise. The office of Louisiana governor has also weighed in on the results.
And in a unique feature, John Underhill presents evidence that one modern Greek isle was actually two islands about 2,000 years ago, suggesting that this lost island is actually the Ithaca described by Homer in The Odyssey.