Tag Archives: melts

Undersea ‘Storm’ Melts Ice Shelf of Terminal Glacier

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Thwaites Glacier, West Antarctica

NASA/ZUMA wire/shutterstock

A submerged “storm” is eroding the ice shelf that shields Antarctica’s Thwaites “Terminal” glacier, prompting concerns that scientists may be underestimating future sea level increases.

These storm-like currents, referred to as “submesoscale” features, can extend up to 10 kilometers wide and begin to form when water with varying temperatures and densities collides in the open ocean. This process is akin to hurricanes that arise from gas mixtures in the atmosphere. Similar to hurricanes, these currents can surge toward the coast, with Antarctica predominantly consisting of ice shelves—floating extensions of glaciers that project tens of kilometers into the ocean.

“Their movements are so unpredictable that halting them is quite challenging,” states Mattia Poinelli from the University of California, Irvine. “The only course of action is for them to become trapped beneath the ice.”

Poinelli and colleagues’ modeling indicates that these submesoscale formations were responsible for one-fifth of the total ice melt in the Thwaites Mountains and nearby Pine Island over a nine-month timeframe. This research marks the first attempt to quantify the influence of these storms across the entire ice shelf.

Ice shelves play a crucial role in hindering the movement of glaciers into the sea and shielding them from wave erosion. The vulnerable Thwaites Glacier annually loses 50 billion tons of ice and could raise sea levels by 65 centimeters if it collapses.

In the Antarctic waters, hundreds of meters of cold, fresh water float above warmer, saltier, deeper water. When a storm becomes enveloped within a cavity beneath an ice shelf, its swirling motions push cold surface water away from the center of the vortex, pulling warmer, deeper water into the cavity and melting the ice shelf from below.

This triggers a feedback mechanism where the melting cold freshwater interacts with the warmer, saltier water, amplifying the rotation of the underwater storm and increasing melting.

In 2022, a deep-sea float that measured temperature, salinity, and pressure was “captured” by a large rotating eddy trapped beneath the ice tongue of Stancombe Wills at another location along the Antarctic coast. The data retrieved from the captured floats showed that Katherine Hancock from Florida State University and her team estimated that the swirl causes 0.11 meters of annual melting beneath its ice tongue.

“This highlights the importance of understanding rotating eddies beneath ice shelves,” says Hancock.

The smaller submesoscale storms from Poinelli’s research are likely causing similar effects, she adds, indicating that swirling water bodies of varying sizes are contributing to significant ice melting. “There’s a need for more precise quantification,” Hancock emphasizes.

As temperatures rise and additional fresh snowmelt escapes from Antarctica, these underwater storms may increase in intensity, possibly leading to greater sea level rise than currently anticipated.

Tiago Dot of Britain’s National Oceanography Centre stated that the “unexpected” findings necessitate further observations beneath the ice shelf.

“Considering the shifts in wind patterns and sea ice around Antarctica, how much are we genuinely overlooking by not monitoring these smaller scales?” he questions.

topic:

  • climate change/
  • Antarctica

Source: www.newscientist.com

Unprecedented Arctic Heat Wave Melts 1% of Svalbard’s Ice

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Svalbard experienced unprecedented heatwaves in the summer of 2024

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During the summer of 2024, six weeks of exceptional heat resulted in significant ice melt on Svalbard, an island in the Arctic. By summer’s end, 1% of the archipelago’s land ice had vanished, contributing to a global sea level rise of 0.16 mm.

“It was incredibly startling,” said Thomas Schuler from the University of Oslo, Norway. “This wasn’t just a minor record; the melt was nearly double the previous highs.”

Over half of Svalbard is covered in ice. Snowfall during winter contributes to the ice, while summertime sees glacial currents flowing into the ocean and surface, resulting in ice retreat.

Schuler’s team utilizes a combination of field measurements, satellite imagery, and computer simulations to assess changes in the total ice mass of the archipelago.

Since 1991, summers have typically seen the melting of Gigatonnes of ice. However, four of the last five years have recorded new highs in summer ice loss. Last summer alone, approximately 62 Gigatonnes melted, predominantly due to surface melting, not ice flowing into the ocean.

In 2024, Schuler and his colleagues observed land rising by a record 16mm at one location, consistent with predictions of ice loss.

This extraordinary melting results from record high air temperatures. The average August temperature reached 11°C (52°F), compared to about 7°C (45°F) in recent decades. This extreme phenomenon stemmed from warm ocean temperatures and persistent weather patterns bringing warm winds from the south, coupled with a dramatic increase in global warming.

While such severe summer heat is currently rare, climate models predict that as global temperatures rise, similar events will become more common. Indeed, even under low emissions scenarios, over half of the summers leading to 2100 could surpass this temperature threshold.

Schuler’s team has yet to predict future ice loss under various emission scenarios. Although winter snowfall is expected to increase slightly as the atmosphere becomes more humid, it will not be sufficient to counterbalance the significantly larger summer melting.

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Source: www.newscientist.com

Ancient forests hidden beneath the Rocky Mountains emerge as ice melts.

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exposed white bark pine

Gregory Pederson

Melting ice in the Rocky Mountains has led to the discovery of a 5,900-year-old white bark pine forest. Scientists discovered more than 30 trees during an archaeological survey on Wyoming's Beartooth Plateau at about 3,100 meters above sea level, 180 meters above the current tree line.

This, he says, “allows us to learn about past conditions at high altitudes.'' Kathy Whitlock at Montana State University. Japanese white pine (Albicari pine) These plants needed to grow during warmer weather, she says, because they don't currently grow at this elevation.

To understand the history of the lost forests, Whitlock's team analyzed tree rings and used carbon dating to find out how old the forests were. They discovered that the tree lived between 5,950 and 5,440 years ago, a time when temperatures were steadily dropping.

Data from ice cores in places like Antarctica and Greenland suggest that these temperature drops were influenced by centuries of volcanic eruptions in the Northern Hemisphere. These produced enough aerial deposits to block sunlight and lower global temperatures until the environment became too cold for these high-altitude trees to survive.

Although the newly discovered tree was lying flat, it was in exceptional condition, indicating that it was rapidly preserved after death. Although there is no evidence of avalanche cover, there are traces consistent with the current expansion of the ice sheet.

Climate models suggest that more continuous volcanic eruptions occurred in Iceland 5,100 years ago, causing further temperature drops, team members say Joe McConnell at the Desert Research Institute in Nevada. These temperature drops led to the expansion of the ice belt, and “the fallen trees were buried in the ice and protected from the elements for the next 5,000 years,” he says.

Only in recent decades have temperatures warmed enough to free trees from their ice cellars. The current tree line is “likely to shift upward as temperatures rise in the coming decades,” Whitlock said.

“This discovery was made possible thanks to anthropogenic climate change. Rising temperatures are exposing areas that have been buried under ice for thousands of years,” she says. “While discoveries like this are scientifically interesting, they are also a sad reminder of how vulnerable alpine ecosystems are to climate change.”

“This study is a very elegant and careful use of a rare 'time capsule' that tells us not only about these mountain forests 6,000 years ago, but also about the climatic conditions that allowed them to exist.” '' he says. Kevin Antukaitis at the University of Arizona.

These trees are not the first such finds that researchers have unearthed from Rocky Mountain ice. Previous research had found “fragments of wooden shafts used for arrows and darts,” Whitlock said. One of the shafts has been radiocarbon dated to be more than 10,000 years old, “which tells us that people have been hunting in high-altitude environments for thousands of years,” she says.

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Source: www.newscientist.com