Melting Greenland ice now source of 25% of sea level rise, researchers say
PARIS – Sea levels increased 50 percent faster in 2014 than in 1993, Greenland ice sheet melting water is currently providing 25 percent of the total sea level rise over just 5 percent 20, researchers said on Monday.
The results add to the growing concern of scientists that the global watermark increases faster than expected for only a few years, with potentially devastating consequences.
Hundreds of millions of people in the world live in the vulnerable low delta, especially when rising seas combined with the sinking of the earth due to the depleted water table or lack of soil formed sediments retained by the prey.
Major coastal cities are also threatened, while some small island states already provide the day of their drowning nation will no longer be habitable.
“This is significant because the Intergovernmental Panel on Climate Change (IPCC)” – the United Nations scientific advisory body – “made a very conservative projection of the full sea level rise by the end of the century” 60 to 90 cm (24 to 35 inches), said Peter Wadhams, a professor of ocean physics at Oxford University who was not involved in the research.
This estimate, he said, assumes that the rate at which ocean levels will increase will remain constant.
“However, there is compelling evidence – including the acceleration of the Greenland and Antarctic mass loss – the reality rate increases and increases exponentially.”
Greenland alone contains enough frozen water to raise the oceans by about 7 meters (23 feet), although experts do not agree on the global warming threshold for irreversible melting, and how long will it take one once put into March.
“Most scientists expect the total increase to be much larger than a meter by the end of the century,” Wadhams said.
The new study, published in Nature Climate Change, brings for the first time two distinct measures of sea level rise.
The first was looked at one by one in three contributions: the expansion of the ocean due to global warming, changes in the amount of water stored in the earth and loss of land ice from glaciers and ice sheets in Greenland and Antarctica.
The second came from satellite altimetry, which measures the altitude of the Earth’s surface from space.
The technique measures the time it takes for a radar pulse to travel from a satellite antenna to the surface and then to a satellite receiver.
So far, elevation data have shown few changes in sea level over the last two decades, although other measures leave little doubt that the oceans are noticeably improving.
“We have set a small but significant part in the first decade of satellite records,” co-author Xuebin Zhang, a professor at the National Marine Science and Technology Laboratory in Qingdao, Shandong Province, told AFP.
Overall, the rate of increase in mean sea level increased by about 2.2 mm per year in 1993 to 3.3 mm per year, two decades later.
In the early 1990s, they found that thermal expansion fully justified half of the millimeters added. Two decades later, that figure was only 30 percent.
Andrew Shepherd, director of the Center for Polar Observation and Modeling at the University of Leeds in England, emphasized caution in interpreting the results.
“Despite decades of measurements, it is difficult to be sure if there was a steady acceleration of sea-level rise during the satellite era, because the change is so small,” he said.
Individual sources unravel – like solid piece of ice above Greenland – is even more difficult.
However, other researchers said the study should signal an alarm.
“This is a serious warning about the dangers of an increase in sea level, which will continue for many centuries even after global warming has stopped,” said Brian Hoskins, president of the Grantham Institute at Imperial College London.