Monday, October 20, 2014

Current Sea Level Rise is Unprecedented in 6000 Years

Sea levels are rising and according to the latest research they are at a 6000 year high. Two forces are combining to accelerate the trend and both are related to global warming. One factor that is contributing to sea level rise is melting ice and the other is thermal expansion.

As the planet warms ice sheets and glaciers melt and the water runs into the oceans. Although this is hardly a new observation, the most recent research indicates that major ice sheets are melting faster than anticipated. Thermal expansion is the process by which warmer ocean water takes up more place as heat increases the space between water molecules.

Rising sea levels are already in evidence in cities like Miami and island nations like the Maldives. Some have attempted to ascribe these rising sea levels to normal variations, however, new research dispels this notion.

As reported by the Washington Post, a comprehensive new PNAS study reviewing the last 35,000 years, suggests that ocean levels have been static since 4,000 B.C. It was only in the last 150 years with the dawn of the industrial revolution that we began seeing changes in sea level.

The study found that the oceans are experiencing greater sea rise than at any time over the last 6,000 years. According to the study's lead author Kurt Lambeck, a professor at Australian National University. "I think that is clearly the impact of rising temperatures."What we see in the tide gauges, we don’t see in the past record, so there’s something going on today that’s wasn’t going on before...I think that is clearly the impact of rising temperatures"

The cause of these sea level rises appears to be clearly attributable to warming global temperatures. "There is robust evidence that sea levels have risen as a result of climate change," Lambeck said.

The PNAS study is corroborated by Australian government research which stated that sea levels have risen by approximately 20 centimeters since the start of the 20th century. "The rate of sea level rise over the last century is unusually high in the context of the last 2,000 years," the Australian report added.

The rising sea levels over the last 100 years, is "beyond dispute," Lambeck told the Guardian.

"We know from the last interglacial period that when temperatures were several degrees warmer than today there was a lot more water in the oceans, with levels around 4 to 5 meters [13 to 16.4 feet] higher than today," Lambeck told the Guardian.

Once the process of rising seas begins it takes a very long time to reverse. "It’s like if you leave a block of ice on the table, it doesn’t melt instantaneously, there’s always a delay in the system," Lambeck said. "All the studies show that you can’t just switch off this process...Sea levels will continue to rise for some centuries to come if we keep carbon emissions at present day levels. What level that will get to, we are less sure about. But it’s clear we can’t just reverse the process overnight."

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