Wednesday, 26 September 2012

Yes- Sea water level rise Over Continental Shelves !!!!

       Since the Last Glacial Maximum (LGM; about 21,000 years ago) sea level has risen by 130 meters (430 feet), resulting in continental shelf submergence and a massive expansion of the surface area of shelf seas. Although shelf seas only account for 7 percent of the oceanic surface area, recent observations demonstrate that they host significant fluxes of carbon dioxide (CO2) between the ocean and atmosphere.

A scientific report endorsed by the United Nations states that unless greenhouse gas emissions are curtailed, average global temperatures may rise between one and three degrees Celsius (two and six degrees Fahrenheit) in the next hundred years. The ramifications of a temperature change at just the low end of this range would be severe. A one-degree Celsius (two-degree-Fahrenheit) change in temperature is predicted to result in a one-meter (three-foot) rise in sea level, which would displace millions of people in coastal cities and low-lying islands. For example, virtually all of the agricultural land in Bangladesh would be covered in seawater and rendered unusable. Another consequence of increased global temperatures would be an acceleration of glacial melt in mountain valleys, which would in turn result in massive flooding in their drainage basins. 

           Further, dissolved and particulate carbon is thought to be transported from shelf areas into sinks in the deep ocean through a mechanism called the "continental shelf pump." Through reconstructions of shelf geography stretching to the LGM, Rippeth et al. analyze the effect of sea level rise and consequent flooding of continental shelves on the growth of the continental shelf pump.

Combining these reconstructions with contemporary estimates of carbon flux between the ocean and atmosphere allows the authors to conclude that expanding shelf seas have significantly influenced the global carbon cycle via the continental shelf pump, with weaker pumping during times when shallower shelf seas were present.

More at: Tom P. Rippeth et al. Impact of sea-level rise over the last deglacial transition on the strength of the continental shelf CO2 pump. Geophysical Research Letters, DOI: 10.1029/2008GL035880

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