A fossil coral reef, lying several metres above today's high tide mark at Foul Bay near Margaret River, points to the high point of the last major sea level rise.
Investigators from the ARC Centre of Excellence for Coral Reef Studies (CoECRS) consider the reef ?the most southerly coral reef yet known ?is a harbinger of what could happen again as global CO2 levels and temperatures rise during the 21st century.
"We've dated the reef to about 128-125,000 years ago, right in the middle of the last interglacial, or the last period of global warming before our most recent ice age," says Professor Malcolm McCulloch, deputy director of CoECRS and an earth scientist at The Australian National University.
"The reef lies about 2.5 metres above the current high tide zone, which means that for it to survive and grow, sea levels would have had to be at least 3 to 4 metres higher than at present.
"There is some evidence ?still controversial ?that sea levels may briefly have been as much as 6 metres higher."
The coastline of WA, being geologically stable, has a number of both living and fossil coral reefs along it, the results of the Leeuwin current bringing coral larvae down from Indonesia and northern Australia over many tens of thousands of years. Together these reefs indicate what occurred during the last big sea level rise.
"At the time when this reef grew we know that atmospheric CO2 levels were high, climate had warmed, that the northern icesheets had melted significantly and that sea levels rose - before dropping by around 130 metres again as the ice-age returned and locked up water," Prof. McCulloch says.
"Water temperatures off Margaret River would then have been more like water temperatures off Geraldton today, allowing the corals to flou
Source:James Cook University