Tropical Coral Fossils Reveal the Past--And Future--of Polar Ice Sheets

You wouldn't think that you'd find out about polar ice on a tropical island, but that's exactly what's happened. Scientists have examined fossil corals on the balmy islands of Seychelles and have found a bit more about the past, and possible future, of polar ice sheets.

About 125,000 years ago, the average global temperature was only slightly warmer than it is today. However, sea levels rose high enough to submerge the locations of many of today's coastal cities. That's why understanding what caused the seas to rise could be crucial to determining what might happen in the future as our climate continues to change.

By studying these corals, the researchers found evidence that global mean sea level during this warmer period peaked at 20 to 30 feet above current levels. It's likely that a rapid retreat of an unstable part of the Antarctic ice sheet was largely to blame for this sea-level rise.

Some of the sea-level rise in the Last Interglacial period was probably driven by the same processes active today, such as thermal expansion of seawater, melting mountain glaciers and melting polar ice sheets in Greenland and Antarctica. Yet most of it was caused by polar ice sheet melt, according to the researchers.

"Following a rapid transition to high sea levels when the last interglacial period began, sea level continued rising steadily," said Andrea Dutton, one of the researchers, in a news release. "The collapse of Antarctic ice occurred when the polar regions were a few degrees warmer than they are now-temperatures that we are likely to reach within a matter of decades."

In fact, other studies have suggested that this process may have already started. It's possible that another partial collapse of the Antarctic ice sheet could begin which would, in turn, raise sea levels.

The findings are important for better understanding what might happen with sea-level rise in the future. That way, coastal cities can prepare and creature infrastructure that may be able to withstand these rises.

The findings are published in the journal Quaternary Science Reviews.

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