An ancient reef that has been uncovered in the Pacific may give us clues as to what will happen when sea temperatures rise.

Researchers from Australia and New Zealand have found a huge 9,000-year-old reef surprisingly far south.

Lord Howe Island is about 400 miles east of the Australian mainland and is home to a small modern coral reef, the furthest south in the world.

The ancient reef, however, is almost 30 times larger than the modern reef.

Colin Woodroffe lead the team of scientists from the University of Wollongong in Australia and researchers from Geoscience Australia, found a large ridge about 30m under water in the Tasman sea.

Their work has been published in Geophysical Research Letters.

The team thinks that it could be an ancient reef. The size and shape of the ridge was mapped out using a type of sonar called multi-beam echo sounding. The researchers were not sure it was was coral, and had to take samples.

Drilling for samples in the Tasman Seas is heavily dependent on weather and the sea can be rought, the process involves lowering a submersible drill from a boat.

The samples found that it was, in fact, coral and radiocarbon dating confirmed the age.

Other ancient reefs, called relict reefs, have been discovered before, but none as south as this.

They estimate that the reef died when it was flooded when the sea levels rose about 7,000 years ago, but modern temperature at that latitude also limits coral growth, which is why the relict reef is so much bigger than the modern reef.

Since sea temperatures are rising, reefs may start to get bigger at higher latitudes.

The relict reef does not have an complex modern reef attached, but it does have some individual corals, which are younger, that are from the last 2,000 years.

This shows that there is a suitable habitat for corals that might grow into a larger reef when temperatures get warmer.

The Northern Hemisphere has both Florida and Bermuda with small reefs, thought they are at the northern limits for coral life.

It is possible that a large relict reef might also be found in more northern waters. Like the Tasman Sea relict reef, these could potentially house new growth.

Rising sea temperatures are dangerous to coral reefs at hotter, more tropical latitudes, but it could mean that we will see new reef growth at the far southern, and northern, limits of current reefs.