Melting glaciers and ice sheets have contributed more to rising sea levels in the past decade than expansion from warming water, according to modelling in the latest report by the Antarctic Climate and Ecosystems (ACE) Cooperative Research Centre.
Before 2000 thermal expansion was the biggest factor in rising sea levels.
The shift was “a fairly sure sign that you’re getting out of the normal balance”, said report author Dr John Hunter, an oceanographer and expert in rising sea levels at the ACE.
Report Card: Sea Level Rise 2012 provides a summary of the past decade of peer-reviewed scientific research into sea-level rise, and is the most recent update since a report in 2008.
During the 20th century sea levels rose at a rate unmatched for 6,000 years, the report says. Satellite measurements have confirmed the global average rise of 1.9mm a year, as measured in tide gauges. “This present sea-level rise is due to a combination of thermal expansion of a warming ocean and the melting of glaciers and ice sheets.”
Dr Hunter explained that modelling had improved since the last update, at which time the contribution to sea levels from melting glaciers and ice sheets was not well understood.
“We’ve been better able to match up two things: observed sea level rises – which we get by looking at tide gauges until about 20 years ago, then after that tide gauges and also records from satellites – and estimates of sea level rises, which we get by looking at ocean temperatures and observing ice on land, the two biggest components, among other things,” Dr Hunter said.