Science Gazette

Researchers have discovered that the world’s glaciers contain less ice than previously assumed

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The results of research on glacier speed and depth have changed the prognosis for freshwater supply and sea level rise.

According to new research, glacial ice volume estimations have been revised, implying that there is less ice in the world’s glaciers than previously assumed. Freshwater and global sea level rise are both affected by the results.

According to experts from the Institute of Environmental Geosciences (IGE) and Dartmouth College, the first atlas to assess the movement and thickness of the world’s glaciers provides a clearer, but varied picture of the world’s ice-bound freshwater supplies.

The study, which was published in Nature Geoscience, monitors the velocity and depth of over 250,000 alpine glaciers all around the globe. The findings contradict prior estimates of glacial ice volume, implying that there is 20% less ice accessible for sea level rise in the world’s glaciers than previously assumed.

The findings have global implications for water supply for drinking, power generation, agriculture, and other purposes. The results also alter forecasts for climate-driven sea level rise, which is predicted to have an impact on people all across the world.

“Knowing how much ice is stored in glaciers is a critical step in predicting the impacts of climate change on civilization,” Romain Millan, a postdoctoral fellow at IGE and the study’s primary author, said. “With this knowledge, we will be closer to determining the size of the largest glacial water reserves and planning for a future with fewer glaciers.”

“The discovery of less ice is significant and will affect millions of people throughout the globe,” said Mathieu Morlighem, the Evans Family Professor of Earth Sciences at Dartmouth and a research co-author. “However, even with this study, we still don’t have a complete picture of how much water is really locked up in these glaciers.”

98 percent of the world’s glaciers are included by the new atlas. Many of these glaciers, according to the study, are shallower than previously thought. Previous data sets were additionally muddled by double counting of glaciers around the peripheries of Greenland and Antarctica.

The research discovered less ice in some areas and more ice in others, resulting in a global finding of less glacial ice than previously assumed.

The tropical Andes mountains of South America have about a quarter less glacial ice, according to the study. According to the findings, there is up to 23% less freshwater stored in a region on which millions of people rely in their daily lives. The loss of this much freshwater is the same as Mono Lake, California’s third biggest lake, completely drying up.

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The Himalayan ranges in Asia, on the other hand, were discovered to contain nearly a third more ice than previously thought. Although the continent’s glaciers are rapidly melting, the study shows that roughly 37% additional water resources might be accessible in the area.

“The general warming and mass loss trend has not altered. This research gives models the information they need to make more accurate estimates of how much time these glaciers have left “Morlighem said.

One of the primary reasons of increasing sea levels is the melting of glaciers as a result of climate change. Glaciers are thought to contribute 25-30% of global sea level rise, posing a hazard to around 10% of the world’s population who live less than 30 feet above sea level.

The 20 percent decrease in glacial ice accessible for sea level rise lowers the potential for glacial contribution to sea level rise by 3 inches, from 13 inches to little over 10 inches. Except for the two massive ice sheets of Greenland and Antarctica, which have a far bigger potential contribution to sea level rise, this prediction incorporates contributions from all of the world’s glaciers.

Millan said, “Comparing worldwide changes with earlier estimates is merely one side of the issue.” “When you start looking locally, the differences are much more noticeable. Capturing precise features is even more significant than overall volume for projecting the future growth of glaciers.”

According to the research, just approximately 1% of the world’s glaciers have previously had depth measurements, and most of those glaciers had only been partly investigated.

According to the research team, the glacial ice estimations that existed before to the current study were nearly wholly unclear. The absence of ice flow data revealing the location of thick and thin ice, all of which is acquired via indirect means, contributes to the uncertainty.

The study team analyzed over 800,000 pairs of satellite photos of glaciers, including enormous ice caps, narrow alpine glaciers, sluggish valley glaciers, and rapid tidewater glaciers, to generate the vast ice flow database. The high-resolution photos were captured by NASA’s Landsat-8 satellite and the European Space Agency’s Sentinel-1 and Sentinel-2 satellites during 2017 and 2018. At IGE, more than 1 million hours of computing were used to analyze the data.

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“We usually think of glaciers as solid ice that melts in the summer,” Morlighem said, “but ice really flows like thick syrup under its own weight.” “Ice goes from higher altitudes to lower elevations, where it finally melts and becomes water. We can trace the movement of these glaciers from space on a global scale using satellite photography, and then calculate the quantity of ice all over the planet.”

The resultant first worldwide map of flow velocities encompasses the majority of the world’s terrestrial glaciers, including areas where no prior mapping had been done, such as South America’s southern cordilleras, the sub-Antarctic islands, and New Zealand.

Despite the fact that the new atlas represents a significant advance in estimations of glacial ice and water potential, the thickness distribution of the world’s glaciers is still prone to massive gaps in data.

“Our estimates are getting closer, but they’re still unpredictable,” Millan added, especially in areas where many people depend on glaciers. “Collecting and exchanging measurements is difficult due to the fact that glaciers are dispersed over so many nations, each with its own research interests.”

The estimation of glacial freshwater supplies would remain unknown, according to the study, without actual field observations.

The research recommends re-evaluating the development of the world’s glaciers in numerical models, as well as firsthand measurements of ice thicknesses in the tropical Andes and Himalayas, which are key water towers but are understudied.

Jérémie Mouginot and Antoine Rabatel of Grenoble Alpes University’s Institute of Environmental Geosciences (IGE), the French National Center for Scientific Research (CNRS), the French National Research Institute for Sustainable Development (IRD), and Grenoble INP Graduate Schools of Engineering and Management contributed significantly to the research. Part of the study was done at the University of California, Irvine, by Millan and Morlighem. Millan is also linked with the CNRS and the University of Copenhagen’s Department of Geosciences and Natural Resources Management. The National Center for Space Studies in France funded the research (CNES).

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