April 8, 2009 -- 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 joint European-Australian study. The finding, which appears in the journal Nature Geoscience, 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. Lead author Andrea Dutton, of the Australian National University, said the stalagmites from Argentarola Cave, Italy, provide an ancient archive of sea water levels because they were formed through two different sources. When the water level in the cave was high, the submerged stalagmites were colonized 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). Related Content:
Dutton said 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 (59 feet) and another from 21 meters (69 feet) 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. Dutton said 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 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. 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. Get More NewsSpiders, Scorpions Among World's Oldest CreaturesMany creepy crawlies have been on Earth much longer than previously believed.Blood-Sucking Vampire Bats Sing DuetsWhite-winged vampire bats "harmonize" with separated roost mates.Oldest Hebrew Writing Possibly FoundAncient inscriptions on a 3,000-year-old pottery shard could make history.Rare, Prehistoric-Age Reptile Found in N.Z.A tuatara has been spotted on the New Zealand mainland for the first time in 200 years.Iceman Has No Living RelativesOetzi, the 5,300 year-old frozen mummy, left no living genetic legacy.SLIDE SHOW: Landscapes of TerrorWhat makes a place feel scary? There are scientific explanations.It's Official: People Are Warming the PolesHumans are conclusively to blame for polar warming, say scientists.Eight-Armed Animal Preceded DinosaursWhat may be one of Earth's first animals was no bigger than a coaster and had eight arms.Phoenicians Live on in People's GenesOne in 17 Mediterranean men may be descended from ancient Phoenicians.Pesticides, Fertilizers Linked to Frog DeclineA pesticide is found to promote parasites among amphibians.Hubble Telescope Taking Photos AgainThe Hubble Space Telescope is once again snapping stunning photos of the universe.Andean Mummy Hairs Show Hallucinogen UseScientists find direct evidence of hallucinogenic drug use among ancient Andeans.Opals on Mars Reveal Planet's Long Wet PastOpals found on Mars suggest the planet has been wet for much longer. |
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