Antarctic Mud Tells Tales of Ancient Ocean Rise
Two complementary studies are showing the potential result of Antarctic ice melt on ocean levels and indicating that the effects of increased greenhouse gases stay with us long after the emissions have stopped.
On July 15 a study by the Potsdam Institute for Climate Impact Research indicated that sea levels could rise 2.3 meters for each degree Celsius increase in global temperatures. Moreover, the changes being wrought at this very moment will not be reversed easily, said the study published in the journal Proceedings of the National Academy of Sciences.
“CO2, once emitted by burning fossil fuels, stays an awful long time in the atmosphere,” said Anders Levermann, the study’s lead author and the research domain co-chair at the Potsdam Institute for Climate Impact Research, in a statement from the Potsdam Institute. “Consequently, the warming it causes also persists.”
Pointing out that the oceans and ice sheets are too massive to respond immediately to these changes, Levermann said it is why sea levels at the moment are only rising a few millimeters annually.
“The problem is: once heated out of balance, they simply don’t stop,” Levermann said.
The study combines evidence from Earth’s most ancient climate history with computer simulations that the researchers created by plugging in the physical models of all four major contributors to long-term global sea-level rise, the Potsdam Institute said. Those are the thermal expansion of the oceans, the melting of glaciers in mountain ranges and the melting of the ice sheets over Greenland and Antarctica.
The ice-sheet melting over Greenland and Antarctic “will be the dominant contributors within the next two millennia,” according to the findings, with half of that increase coming from the loss of Antarctic ice. Currently that is contributing less than 10 percent to global sea-level rise, Levermann said.
Of special concern is the effect of the ocean rise and the ice melt on the climate, said one scientist who was not involved in this study.
"It's not about chasing people up the beach or the changing shape of coastlines," said David Vaughan, head of the Ice2sea project, which aims to home in on the ways that melting ice will affect sea levels, to Reuters. "The big issue is how the storms will damage our coasts and how often they occur. That'll increase even with small levels of sea rise in coming decades."
The moment of Antarctic ice sheet melting truth may be upon us sooner than we think, a second study shows. Out this week from the Grantham Institute for Climate Change at Imperial College London is the finding that the last time greenhouse gases were at current levels—that would be during the Pliocene epoch, which occurred from 5.3 million to 2.6 million years ago, according to NBC News.com—ocean levels were 60 feet higher than they are today.
During that era, there simply were no West Antarctic and Greenland ice sheets, said the researcher, Carys Cook, to NBC News.com. To arrive at her conclusions, Cook and her team studies the chemical composition of sediments and found rock types that only occur inland, far from ice sheets, NBC News said. These findings were published in the journal Nature Geoscience, NBC News said.