Stalagmites reveal rapid sea level rises caused by global warming 200,000 yrs ago

April 9th, 2009 - 5:35 pm ICT by ANI  

Sydney, April 9 (ANI): A joint European-Australian study has determined that ancient stalagmites from a submerged Italian cave have revealed sea level rises caused by global warming more than 200,000 years ago.

According to a report by ABC News, the finding suggests the current melting of ice sheets may happen faster than expected.

Their publication adds weight to the release of an international report showing up to one-third of all Antarctic sea ice is likely to melt by the end of the century.

The stalagmites from Argentarola Cave, Italy, provide an ancient archive of sea water levels because they were formed through two different sources, according to lead author Dr Andrea Dutton, of the Australian National University.

When the water level in the cave was high, the submerged stalagmites were colonised by aquatic worms that encased it in a tube made from biogenic calcite.

When the level dropped, the stalagmites formed from water drops from the cave ceiling (spelean calcite).

Dutton said that the difference between the two types of calcite is stark with the water from the ceiling leaving a darker deposit.

The researchers removed two stalagmites from the cave, one from 18 meters and another from 21 meters below current sea level.

Uranium isotope dating techniques showed the stalagmites recorded water levels in the cave as far back as between 190,000 and 245,000 years ago.

Bracketing of the marine calcite by the spelean calcite also allowed the researchers to accurately gauge the duration of the sea water-level rise.

According to Dutton, although it was previously known there were three peaks in sea water levels during this time, they “hadn’t been well dated”.

“Most direct evidence of sea level changes only go back as far as 20,000 years,” she said.

Dutton said that the strength of the stalagmite archive is that it is not as susceptible to alteration by the environment when compared with coral reef clusters that are also commonly used to date sea water rises.

She said that the findings are critical in determining how the natural processes during climate change work.

They provide a benchmark and help determine which reconstruction models used to determine sea water levels are accurate.

“If we are relying on models it is important for us to know which models to rely on,” said Dutton. “And this study gives us a benchmark on which to judge them,” she added. (ANI)

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