The incredible journey to the bottom of a glacier that revealed its weaknesses | Antarctica

Scientists who study the vast Thwaites Glacier of Antarctica – which some call the Last Judgment Glacier, due to its size and the damage that its collapse is thought to cause they say the hot water is seeping into its weak spots, worsening the thaw caused by the rise in temperature. The warning appears in two articles published in the journal Nature this wednesday. The results reveal varied patterns of ice loss and suggest complex interactions with other glaciers that will play a key role in the future of this glacier.

It was already known that the Thwaites collapse, which is roughly the size of Great Britain or the size of the US state of Florida, could represent more than half a meter of potential global sea level rise over the next 200 years, and could destabilize neighboring glaciers which, in turn, have the potential to cause another ten-foot rise.

The summary of nature regarding the two projects, he notes that the position of this icy platform makes it “particularly vulnerable to instabilities that could lead to a rapid and irreversible loss of ice”. The truth is, this is one of the most rapidly changing ice systems in Antarctica. “Ocean conditions, ice loss and flow rates are known to influence glacier baseline retreat, where it breaks off the ground and begins to float, but exactly how these factors work remains to be seen. misunderstood.”

As part of the international Thwaites Glacier collaboration – the largest field campaign ever undertaken in Antarctica – a team of 13 US and British scientists spent around six weeks on the glacier in late 2019 and early 2020.

Crevasses on Thwaites Glacier in 2020

Icefin took us to the base of the ice

Using an underwater robot vehicle known as Icefin, along with other data and sensors, the scientists monitored the line where the glacier sits, where the ice slides off the glacier and meets the ocean for the first time.

In an attempt to understand the full vulnerability of Thwaites Glacier, the two groups of scientists report observations of ice melt rates and the properties of the glacier and the surrounding ocean. “These measurements were taken through an access hole drilled through approximately 587 m of ice approximately 1.5-2.0 km downstream of the glacier baseline.”

On the one hand, the researchers went 1.5 meters below the ice shelf, to measure ocean temperature, salinity, velocity, and rate of melting over time. “They found warm water under the floating ice shelf, and realized that this stratification separates these waters from the ice, thus suppressing melting”, states the abstract of the articles adding that “these findings show that the rapid retreat of the Thwaites Glacier can occur without a extensive basal melt”.

In one of the works, led by scientist Britney Schmidt, from Cornell University in the US, researchers found that warmer water was entering crevices and other openings, causing lateral melting of 30 meters or more per year. “The warm water is getting into the weakest parts of the glacier and weakening it,” Schmidt told Reuters.

The team coordinated by this scientist also used an underwater vehicle to measure oceanic properties, focusing more on the shape of the ice over a wider region. “They found that high melt rates occur where ice is steeply tilted at the oceanic interface, while melting is suppressed at flat interfaces. These observations demonstrate the influence of ice morphology on ice loss.”

“This is the kind of thing we should all be very concerned about”, said the scientist about these discoveries that reinforce how the climate change are hitting isolated Antarctica. With the Icefin robot, scientists managed to reach areas that were almost impossible to monitor.

The Icefin robot to be placed in the hole as part of the study coordinated by Britney Schmidt

The fragile balance of ice

In another article now published in Nature, on which Britney Schmidt also collaborated, the researchers reveal a glacier melt of between two to five meters per year near the baseline of the glacier. It is less than what the most pessimistic models previously predicted, but even so, the scientist warns that this thaw remains a cause for great concern.

Peter Davis, oceanographer at the British Antarctic Survey (BAS)​ and lead author of this study​made measurements of the ocean through a 600-metre-deep borehole about two kilometers from the baseline, created by a warm-water drill in late 2019. “These measurements were compared with melt rate observations made in five other locations beneath the ice shelf. Over a nine-month period, the ocean near the baseline became warmer and saltier, but the melt rate averaged 2 to 5 meters per year: less than previously modeled”, says the BAS press release.

“Our results are a surprise, but the glacier is still in trouble. If an ice shelf and a glacier are in equilibrium, the ice that leaves the continent will correspond to the amount of ice that is lost through the melting of the iceberg. What we’ve found is that despite small amounts of melting, there’s still rapid retreat from the glacier, so it doesn’t look like it takes much to push the glacier out of balance,” explains Peter Davis, quoted in the statement.

“We’re seeing less melting…but that doesn’t change the fact that it’s receding,” insists Britney Schmidt.

The two teams from the two projects (MELT and Icefin) on Thwaites Glacier in 2020

See more, find out more

Scientists have previously relied on satellite imagery to show ice behavior, making it difficult to get more detailed data about this gradual process. The articles published now represent the first time a team has been to the baseline of a large glacier, providing an incredible glimpse into where “the action begins”, says Britney Schmidt.

In the BAS communiqué on this international collaboration for the study of the Thwaites Glacier it is also stated that it was possible to see that “a layer of fresher water between the bottom of the ice shelf and the underlying ocean, slows down the rate of melting along the flat parts of the ice shelf”. “But the authors were surprised to see that the melt had formed a ladder-shaped topography [terraços] along the bottom of the ice shelf. In these areas, as well as in the fissures in the ice, rapid melting is taking place.”

Thus, the researchers note that “although vertical melting along the base of the ice shelf was lower than expected, melting along the sloped ice in these crevasses and terraces is much higher and may be a significant factor in ice loss. through Thwaites Glacier, especially as large cracks are progressing along the ice shelf and could become the main trigger for ice shelf collapse”.

The results will help in the development of climate change models, explained Paul Cutler, director of the Antarctic Science program at the National Science Foundation and who helped review the papers but was not involved in the research. The rapid retreat of Thwaites Glacier in West Antarctica appears to be driven by different processes under its floating ice shelf.

“These conclusions can now be taken into account in the models that will predict the future behavior of this glacier, and that was exactly the objective of this work”, he concludes.

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