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Greenland Ice Sheet Melting 7% Faster Than Previously Thought

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Greenland Ice Sheet Melting 7% Faster Than Previously Thought

By Jeremy Deaton

You might know the feeling—after months of encouraging news from your bathroom scale, you discover the device is broken. The outlook on your weight-loss goal is worse than you realized.

Scientists just went through something similar, except instead of a scale, it was a system of satellites, and instead of your winter weight, it was the Greenland ice sheet.

Zachariae Isbrae, in northeast Greenland.Anders A Bjork/The Ohio State University

Researchers have been tracking Greenland's ice sheet melt by measuring the shrinking mass of the island via satellite. It now seems there was an error in measurement. A new study published in the journal Science Advances finds the ice is melting 7 percent faster than previously thought.

Scientists use satellites to map Earth's gravity field, gathering information about the distribution of mass around the globe. Earth doesn't exert gravity equally in all directions. Where there is more mass, satellites detect a stronger gravitational pull.

Using satellite data, scientists can measure various geophysical phenomena, including the melt of the Greenland ice sheet. As ice dissolves, the island loses mass and exerts a weaker gravitational pull—at least that's the idea.

An artist's rendering of NASA's Gravity Recovery and Climate Experiment satellites measuring Earth's gravity field.NASA/JPL-Caltech

In practice, it's a little more complicated. Satellites can only detect a change in mass. They can't determine how much of that mass is ice, how much is land and how much is mantle ebbing and flowing beneath the Earths' crust.

"[The system] cannot tell the difference between ice mass and rock mass," said study co-author Michael Bevis, professor of Earth sciences at Ohio State. "So, inferring the ice mass change from the total mass change requires a model of all the mass flows within the Earth."

Here's where this gets interesting.

A cross-section of Earth. The Earth's crust rests on a thick layer of mantle. Below that lies the Earth's solid core.NASA/JPL, Université Paris Diderot and the Institut de Physique du Globe de Paris

Tectonic plates are always moving. The plate under North America—including Greenland—has been traveling northwest for millions of years. Around 40 million years ago, Greenland slid over an extra hot column of partially molten rock. This hot spot softened up the crust below the island's east coast. (The hot spot now rests beneath Iceland, where it is driving all manner of volcanic activity—warming hot springs and fueling the country's geothermal power plants.)

The softening of Earth's crust beneath Greenland had consequences during the last ice age, when Greenland's ice sheet was significantly thicker. The weight of all that ice caused the island to sink into the supple crust below. When the ice age passed and the ice began to melt, the island rebounded. Mantle flowed in beneath Greenland, causing the land to rise again. It's still rising today.

You can imagine how this would interfere with satellite readings. The loss of ice is weakening Greenland's gravitational pull. At the same time, the accumulation of mantle is strengthening its gravitational pull.

One of dozens of GPS units researchers used to measure the rise of land.Dana J. Caccamise II/The Ohio State University

Scientists previously accounted for the flow of mantle, but they underestimated its effect. The study's authors used GPS technology to measure the rise of land at various points along Greenland's east coast. They discovered that mantle is gathering beneath Greenland more quickly than they had realized.

What this means is that scientists have been underestimating ice loss by 20 billion metric tons per year. More of the melting is occurring along Greenland's east coast than previously thought.

Water overflow from a lake formed from melted ice carved this 60-foot canyon into the Greenland ice sheet.Ian Joughin, University of Washington

"By refining the spatial pattern of mass loss in the world's second largest—and most unstable—ice sheet, and learning how that pattern has evolved, we are steadily increasing our understanding of ice-loss processes, which will lead to better-informed projections of sea-level rise," said Bevis.

The study has implications for Antarctica—the 800-pound gorilla of global sea-level rise. Scientist will need to deploy more GPS measurement stations at Earth's southern pole to accurately measure the flow of mantle beneath the continent and get a better reading of Antarctic ice melt.

Better data will allow scientists to predict future sea-level rise more accurately. That could prove crucial for coastal cities preparing for the impacts of climate change.

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An illustration depicts the extinct woolly rhino. Heinrich Harder / Wikimedia Commons

The last Ice Age eliminated some giant mammals, like the woolly rhino. Conventional thinking initially attributed their extinction to hunting. While overhunting may have contributed, a new study pinpointed a different reason for the woolly rhinos' extinction: climate change.

The last of the woolly rhinos went extinct in Siberia nearly 14,000 years ago, just when the Earth's climate began changing from its frozen conditions to something warmer, wetter and less favorable to the large land mammal. DNA tests conducted by scientists on 14 well-preserved rhinos point to rapid warming as the culprit, CNN reported.

"Humans are well known to alter their environment and so the assumption is that if it was a large animal it would have been useful to people as food and that must have caused its demise," says Edana Lord, a graduate student at the Center for Paleogenetics in Stockholm, Sweden, and co-first author of the paper, Smithsonian Magazine reported. "But our findings highlight the role of rapid climate change in the woolly rhino's extinction."

The study, published in Current Biology, notes that the rhino population stayed fairly consistent for tens of thousands of years until 18,500 years ago. That means that people and rhinos lived together in Northern Siberia for roughly 13,000 years before rhinos went extinct, Science News reported.

The findings are an ominous harbinger for large species during the current climate crisis. As EcoWatch reported, nearly 1,000 species are expected to go extinct within the next 100 years due to their inability to adapt to a rapidly changing climate. Tigers, eagles and rhinos are especially vulnerable.

The difference between now and the phenomenon 14,000 years ago is that human activity is directly responsible for the current climate crisis.

To figure out the cause of the woolly rhinos' extinction, scientists examined DNA from different rhinos across Siberia. The tissue, bone and hair samples allowed them to deduce the population size and diversity for tens of thousands of years prior to extinction, CNN reported.

Researchers spent years exploring the Siberian permafrost to find enough samples. Then they had to look for pristine genetic material, Smithsonian Magazine reported.

It turns out the wooly rhinos actually thrived as they lived alongside humans.

"It was initially thought that humans appeared in northeastern Siberia fourteen or fifteen thousand years ago, around when the woolly rhinoceros went extinct. But recently, there have been several discoveries of much older human occupation sites, the most famous of which is around thirty thousand years old," senior author Love Dalén, a professor of evolutionary genetics at the Center for Paleogenetics, said in a press release.

"This paper shows that woolly rhino coexisted with people for millennia without any significant impact on their population," Grant Zazula, a paleontologist for Canada's Yukon territory and Simon Fraser University who was not involved in the research, told Smithsonian Magazine. "Then all of a sudden the climate changed and they went extinct."

A large patch of leaked oil and the vessel MV Wakashio near Blue Bay Marine Park off the coast of southeast Mauritius on Aug. 6, 2020. AFP via Getty Images

The environmental disaster that Mauritius is facing is starting to appear as its pristine waters turn black, its fish wash up dead, and its sea birds are unable to take flight, as they are limp under the weight of the fuel covering them. For all the damage to the centuries-old coral that surrounds the tiny island nation in the Indian Ocean, scientists are realizing that the damage could have been much worse and there are broad lessons for the shipping industry, according to Al Jazeera.

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A quality engineer examines new solar panels in a factory. alvarez / Getty Images

Transitioning to renewable energy can help reduce global warming, and Jennie Stephens of Northeastern University says it can also drive social change.

For example, she says that locally owned businesses can lead the local clean energy economy and create new jobs in underserved communities.

"We really need to think about … connecting climate and energy with other issues that people wake up every day really worried about," she says, "whether it be jobs, housing, transportation, health and well-being."

To maximize that potential, she says the energy sector must have more women and people of color in positions of influence. Research shows that leadership in the solar industry, for example, is currently dominated by white men.

"I think that a more inclusive, diverse leadership is essential to be able to effectively make these connections," Stephens says. "Diversity is not just about who people are and their identity, but the ideas and the priorities and the approaches and the lens that they bring to the world."

So she says by elevating diverse voices, organizations can better connect the climate benefits of clean energy with social and economic transformation.

Reposted with permission from Yale Climate Connections.

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