![]() "Higher temperatures correspond with higher rates of sea level change and vice versa." 'The temperature and sea level reconstructions were determined independently from each other, and yet each shows what we would expect based on the other," said Mann. The results tallied well with other reconstructions, and with local and global tidal gauge records. They were dated accurately using a combination of radiocarbon and pollen sequences. ![]() These contain foramnifera, microscopic fossils which can tell scientists the depth of the overlying waters. In order to work out the level of the sea over the last two-thousand years, the team looked at thick slices of muddy sediment in the sheltered waters of the Pamlico Sound. That makes deciphering which sea-level changes are down to temperature fluctuations more difficult.īut the marshes off of the US east coast have had a much simpler history - so taking account of the slow resettling of the earth's foundations is much easier here. Previous sea-level reconstructions are in those parts of the world still on the move - due to tectonic shifts, or where the land is rebounding from the burden of the last Ice Age. The international team of scientists turned to North Carolina, in part because this area of the world has been geologically quiet for many millennium. The results are published online in today's Proceedings of the National Academy of Sciences. That's what a research team, including Penn State's Michael Mann, have done - looking to North Carolina's salt marshes for a fresh insight into the sea-level conundrum. Tie these records tightly enough to detailed temperature records, and scientists may get a better grasp on what their models should be showing. One way to help knock down that uncertainty is to turn to past records of sea-level fluctuations, to see if they can point to the future. But what about the melting of the land-based ice-sheets of Greenland and Antarctica? And the disappearing mountain glaciers of the Rockies and the Andes? How will a warming world spill these frozen waters into the sea, and so back onto our low-lying cities? Those questions are something that climate scientists try to model, but which they still find difficult to predict. We know that warming water expands - and so coastal communities will be threatened, as the sea swells in response to rising temperatures. Sea-level rises from global warming remain one of the big unknowns in the jostling crowd of climate threats.
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