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Key Part of World’s Largest Ice Shelf Melting 10 Times Faster Than Average

Climate
The front of the Ross Ice Shelf floats in the Ross Sea, as seen from the cockpit of an LC130 aircraft flown by the New York Air National Guard. Matt Siegfried / Flikr

Parts of the world's largest ice shelf are melting 10 times faster than the shelf's average rate, and this could have worrying implications for sea level rise.

The finding is part of a study of the Ross Ice Shelf, a block of ice about the size of France, which plays an important role in stabilizing the rest of Antarctica, as BBC News reported.


"Previous studies have shown that when ice shelves collapse, the feeding glaciers can speed up by a factor or two or three," study co-author Dr. Poul Christoffersen of Cambridge's Scott Polar Research Institute said in a University of Cambridge press release. "The difference here is the sheer size of Ross Ice Shelf, which over one hundred times larger than the ice shelves we've already seen disappear."

The study, published in Nature Geoscience Monday, was based on four years of observation of how the Ross Ice Shelf's north-west sector interacted with the ocean surrounding it. Researchers found that the sun was warming surface ocean water, which was in turn melting the shelf at rates higher than they had expected.

"The stability of ice shelves is generally thought to be related to their exposure to warm deep ocean water, but we've found that solar heated surface water also plays a crucial role in melting ice shelves," first author Dr. Craig Stewart from the National Institute of Water and Atmospheric Research (NIWA) in New Zealand said in the press release.

The finding that the ice shelf is so sensitive to surface ocean temperatures means it is likely to melt even faster in the future, Stewart said, since climate change is likely to melt sea ice in the Ross Sea, leading to a warmer ocean surface.

The researchers stressed that the ice shelf is currently stable, but is more vulnerable than previously thought. That vulnerability is enhanced by where the sped up melting is taking place. The warm surface water is flowing into a cavity near a pinning point: a place where the Ross Ice Shelf pushes against Ross Island, helping to stabilize the shelf. If pressure on that pinning point is reduced, the ice shelf could become less stable, British Antarctic Survey (BAS) oceanographer Keith Nicholl said, as CNN reported.

"These ice front pinning points help control the flow of a lot of Antarctic ice shelves, and so the study demonstrates another vulnerability of ice shelves to climate change," Nicholl said.

That means that melting in this one area could have a wide impact on surrounding glaciers.

"The observations we made at the front of the ice shelf have direct implications for many large glaciers that flow into the ice shelf, some as far as 900 km (approximately 559 miles) away," Christoffersen said.

If all the major ice shelves in the world collapsed, BAS said sea levels could rise several meters or more, CNN reported.

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A volcano erupts on New Zealand's Whakaari/White Island on Dec. 9, 2019. Michael Schade / Twitter

A powerful volcano on Monday rocked an uninhabited island frequented by tourists about 30 miles off New Zealand's coast. Authorities have confirmed that five people died. They expect that number to rise as some are missing and police officials issued a statement that flights around the islands revealed "no signs of life had been seen at any point,", as The Guardian reported.

"Based on the information we have, we do not believe there are any survivors on the island," the police said in their official statement. "Police is working urgently to confirm the exact number of those who have died, further to the five confirmed deceased already."

The eruption happened on New Zealand's Whakaari/White Island, an islet jutting out of the Bay of Plenty, off the country's North Island. The island is privately owned and is typically visited for day-trips by thousands of tourists every year, according to The New York Times.

Michael Schade / Twitter

At the time of the eruption on Monday, about 50 passengers from the Ovation of Seas were on the island, including more than 30 who were part of a Royal Caribbean cruise trip, according to CNN. Twenty-three people, including the five dead, were evacuated from the island.

The eruption occurred at 2:11 pm local time on Monday, as footage from a crater camera owned and operated by GeoNet, New Zealand's geological hazards agency, shows. The camera also shows dozens of people walking near the rim as white smoke billows just before the eruption, according to Reuters.

Police were unable to reach the island because searing white ash posed imminent danger to rescue workers, said John Tims, New Zealand's deputy police commissioner, as he stood next to Prime Minister Jacinda Ardern in a press conference, as The New York Times reported. Tims said rescue workers would assess the safety of approaching the island on Tuesday morning. "We know the urgency to go back to the island," he told reporters.

"The physical environment is unsafe for us to return to the island," Tims added, as CNN reported. "It's important that we consider the health and safety of rescuers, so we're taking advice from experts going forward."

Authorities have had no communication with anyone on the island. They are frantically working to identify how many people remain and who they are, according to CNN.

Geologists said the eruption is not unexpected and some questioned why the island is open to tourism.

"The volcano has been restless for a few weeks, resulting in the raising of the alert level, so that this eruption is not really a surprise," said Bill McGuire, emeritus professor of geophysical and climate hazards at University College London, as The Guardian reported.

"White Island has been a disaster waiting to happen for many years," said Raymond Cas, emeritus professor at Monash University's school of earth, atmosphere and environment, as The Guardian reported. "Having visited it twice, I have always felt that it was too dangerous to allow the daily tour groups that visit the uninhabited island volcano by boat and helicopter."

The prime minister arrived Monday night in Whakatane, the town closest to the eruption, where day boats visiting the island are docked. Whakatane has a large Maori population.

Ardern met with local council leaders on Monday. She is scheduled to meet with search and rescue teams and will speak to the media at 7 a.m. local time (1 p.m. EST), after drones survey the island, as CNN reported.