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(This story is part of a multimedia series on climate change.Full coverage: https://tmsnrt.rs/2xvdzOS)
GREENLAND, Sept. 19 (Reuters) – While flying over East Greenland, NASA scientists observed a Gulf Stream jet following the precise course they had taken in previous years, using radar to map ice loss.
In the subway, flight engineer David Elliott said the team had managed to cross the sea ice covering 80% of the largest island in the world. Through the window, chunks of broken ice looked like splinters of salt on the water.
The March mission was part of the NASAs Oceans Melting Greenland (OMG) project, a five-year, $ 30-million effort to improve sea-level rise projections by understanding how ocean warming is melting. the ice caps. date.
Rising seas threaten cities, islands and low-altitude industries around the world. However, the projections for the height and speed of the climb vary widely, in part because scientists lack clarity about the speed at which the oceans warm up melt the polar ice caps. Uncertainty confuses the preparations of governments and businesses and feeds the arguments of skeptics about climate change.
(For more stories, graphics and videos from the interactive Greenland Project series, see: https://tmsnrt.rs/2xvdzOS)
A draft report by the United Nations Intergovernmental Panel on Climate Change (IPCC), for example, predicts that the sea will likely increase by 33 centimeters to 1.33 meters by 2100, a wider range than the estimate of 28 to 98 centimeters from the last IPCC 2013 Assessment.
The IPCC projections, which have been reviewed by Reuters, have not yet been published.
Until now, most glacier research has focused on warming the air that melts the ice sheets, but ocean warming plays a crucial role, said Josh. Willis, Senior Researcher, OMG
It's not just an ice cube and a hair dryer, he said, offering a metaphor often used to say that warmer air melts glaciers. Really begin to understand how these icecaps will behave in a warming world.
The OMG project aims to clarify how Greenland itself contributes to the rise of the seas, but also to apply this knowledge to the study of the much larger Antarctic region, which has much more ice and could play a much more important role in elevation. And while most of Greenland's ice is above sea level, large parts of the western Antarctic ice cap are below sea level, making them more vulnerable to global warming.
According to NASA, melting ice in Greenland is currently adding 0.8 millimeters of water to global ocean levels, more than any other region. It's enough water to fill 115 million Olympic pools.
The scientists in the IPCC study, which is expected to be the most reliable sea level assessment to date, refused to discuss the preliminary findings of the record. Hans-Otto Poertner, one of the leaders of the IPCC report, said the document would be subject to review and further revision before its publication in September 2019.
The range provided for sea level rise, however, should not be more precise, said a scientist working on the project under cover of anonymity.
The range of sea level rise is expanding, according to the scientist.
HOLES IN THE DATA
Better projections would be invaluable to governments around the world. Britains Environment Agency, for example, is planning improvements to a Thames River barrier to protect London against 90 centimeters of sea level rise by 2100, but could alter plans to account for a disaster. 2.7 meters.
A 2017 study published by American scientists in a journal of the American Geophysical Union estimated that by 2100, a 50-centimeter increase would plunge the lands that currently shelter about 90 million people, mainly in China, Vietnam, and China. Bangladesh. According to one study, a 1.5-meter rate would overwhelm the homes of more than 150 million people worldwide.
A 2016 study published in a journal of the US National Academy of Sciences predicted that an event comparable to Hurricane Sandy, which flooded large swaths of the New York area in 2012, would be 17 times more likely. likely by 2100 if the seas rose 1 meter.
The high seas are already creating more dangerous storm surges, according to the IPCC, exacerbating floods or coastal erosion from the US Gulf Coast to the Maldives in the direction of China. Some low-lying island nations, such as Fiji and Vanuatu, have displaced some coastal communities to higher areas.
According to the IPCC project, the rate of sea level rise in 2100 will largely depend on governments' efficiency in reducing fossil fuel pollution, which has been the main cause of global warming since the mid-20th century. century.
However, according to David Holland, a New York University oceanographer who has studied Greenland glaciers for 12 years, it is difficult to predict how the melting glaciers will contribute to the rise of the seas.
Modeling is like Swiss cheese, Holland said. Its entering the most difficult projections and unknown physics.
DEPTH, HOT WATER
Some of Greenland's glaciers are disappearing faster than others and understand why is a key goal of NASA's mission.
New NASA data on water temperature, depth and salinity have helped explain why the ice-loss rate in northwestern Tracy Greenland is almost four times faster than that of the Heilprin Glacier . The researchers found that Tracy's freshwater, which rests on deeper bedrock, mixes with a warm, salty layer of water off the coast of Greenland, accelerating the process of fusion.
Many more Greenland glaciers have similar problems. The researchers found last year that 67 glaciers were connected to the warmer and deeper layer at least 200 meters below sea level, at least twice as much as previously known.
In June, a four-mile-wide iceberg detached from the Helheim Greenlands Glacier and cracked into a process called calving, an event that may be caused by warming oceans. Scientists fear that calving will occur on a disastrous scale in Antarctica, where it is believed that the much larger Thwaites Glacier would be a hub of the western Antarctic ice cap.
If the Thwaites behaved like Helheim, we have no idea how fast it could erode, said Robert DeConto, professor of geoscience at the University of Massachusetts-Amherst and a member of the IPCC team producing the sea. report of increase to expected level expected next year.
The IPCC project suggests that Antarctica alone could contribute up to half a meter of sea level this century and cites more and more evidence that the process may be irreversible.
The sound of the alarm
The importance of glacier change for sea-level rise in this century has been widely understood in the scientific community only recently. In 1995, the Second Assessment of the IPCC indicated that few changes in the extent of the ice caps of Greenland and Antarctica are expected over the next 50 to 100 years.
In 2007, he said the new data show that ice losses in Greenland and Antarctica most likely contributed to sea-level rise from 1993 to 2003, but did not contribute to melting ice.
At first, people thought, just assume these things are stable, said climate scientist Gavin Schmidt, who heads NASA's Goddard Institute for Space Studies. Even today, he said, there are very few climate models that present a credible simulation of any dynamic behavior of the ice sheet.
Scientific uncertainty is a political problem, said Tad Pfeffer, a professor at the University of Colorado and a former IPCC author. Skeptics, including US President Donald Trump, are attacking the science of climate change as an unproven and politically motivated attack on the fossil fuel industries and last year said he would pull the United States out of business. 2015 climate agreement that includes nearly 200 countries.
"The public, especially if they are driven by unscientific opinions, takes uncertainty as saying: These scientists do not know what they are doing," Pfeffer said. (Report by Alister Doyle in Oslo, Norway, Elizabeth Culliford in New York and Lucas Jackson in Greenland Additional reportage by Travis Hartman in Greenland and Christine Chan in New York Editing by Richard Valdmanis and Brian Thevenot)
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