Tuesday, January 26, 2010

Historical Sea Level Fluctuations

A new study from the University of Haifa suggests sea levels might have fluctuated during historical times far more than previously believed. Dr. Dorit Sivan, who supervised the research, writes that an investigation of underwater ruins along the coast of Israel show short term changes of the sea level of almost a meter during the last 2500 years. We are currently near the highest level.
According to Dr. Sivan, the changing sea level can be attributed to three main causes: the global cause – the volume of water in the ocean, which mirrors the mass of ice sheets and is related to global warming or cooling; the regional cause – vertical movement of the earth's surface, which is usually related to the pressure placed on the surface by the ice; and the local cause – vertical tectonic activity. Seeing as Israel is not close to former ice caps and the tectonic activity along the Mediterranean coast is negligible over these periods, it can be concluded that drastic changes in Israel's sea levels are mainly related to changes in the volume of water.

So far, only a press release version of the study has been released. I'd like to see the complete study when it comes out because this short summary leaves me with more questions than answers. The press release only mentions sites along a short stretch of coast (about forty miles) in the eastern Mediterranean. Has Sivan compared these results to records from any other part of the world? Considering that the Jordan River/Dead Sea valley is a rift zone, how can they be sure that local tectonic activity isn't involved? Do temperature records, such as those obtained the Greenland ice cores of pollen found in lakebed strata, support their sequence? For that matter, what is the sequence? Inquiring minds need to know.

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