Thwaites Glacier

satellite of the European Space Agency. It shows the glacier, the ice shelf on its eastern side, and the remains of the ice tongue in the west, now reduced to a "mélange" of icebergs which is much less effective at supporting the glacier and preventing calving events. Thwaites Glacier is located at the northern edge of the West Antarctic Ice Sheet, next to Pine Island Glacier. Both glaciers continually shed ice from their grounding line into Pine Island Bay, which is part of the Amundsen Sea. The fastest flows of ice occur between east of Mount Murphy, where they can exceed per year. Due to this immense size, enormous mass is shed when the repeated ice calving events occur at the glacier's marine terminus—the point where grounding line is in contact with water. The largest events, on the glacier's more vulnerable western side, are seismically detectable at ranges up to . The third Antarctic expedition of Richard E. Byrd in 1940 is believed to be first official sighting of the coastline of Thwaites. Detailed mapping of the glacier's surface took place between 1959 and 1966. McMurdo Station is used by researchers studying the glacier, such as the International Thwaites Glacier Collaboration (ITGC). but as parts of the iceberg tongue continued to calve, it diminished in size (to long and wide). Post-2010 break-up and current state Thwaites Glacier Tongue had also experienced destructive changes, eventually shortening to long and wide. In 2023, scientists found that ice tongue retreat rates are subject to wide fluctuations after its break-up: over six years of observations, annual retreat accelerated by as much as 40% (from around to per year) twice, before slowing back down. These researchers have also repurposed a machine learning algorithm normally used in microbiology to identify crevasses in the remains of the ice tongue and project how they may affect its stability. Iceberg B-22a On 15 March 2002, a notable calving event took place, when the National Ice Center reported that an iceberg named B-22 broke off. This iceberg was about long by wide, with a total area of some , comparable to Rhode Island. While most of the iceberg broke up quickly, the largest piece, B-22A, with an area of around or "twice the size of Houston, Texas", drifted in the vicinity of the glacier even as the rest of the glacier tongue continued to break up. In 2012, it got stuck on seafloor, away from the ice tongue, where its presence had some stabilizing impact on the rest of the glacier. In October 2022, it finally started moving again, rapidly drifting to the northwest. It is likely to end up as one of the longest-lived icebergs in history. Thwaites Ice Shelf Glaciers in Antarctica commonly have ice shelves, which are large bodies of sea ice that are permanently floating just offshore, and whose presence helps to stabilize the glacier. Though the Thwaites Ice Shelf has a width of and some research suggests that the loss of the ice shelf would result in almost no change to glacier's trajectory. Subglacial features nearly twice the global average, and about 3.5 times larger in hotspots. By 2017, scientists have mapped 138 volcanoes beneath the West Antarctic Ice Sheet, with 91 of them previously unknown. Marie Byrd Land, the location of Thwaites and Pine Island Glaciers, was found to harbor around one volcano per every of area. This density is relatively high, though it is lower than in other global hotspots such as the East African Rift (one per ) or even Antarctica's own central rift (one per ). The heat from magma flows beneath these volcanoes can affect melting, and the risk of volcano eruptions increases as more ice is lost as a consequence of isostatic rebound. ==Importance==

over that period. , the location of both Thwaites (TEIS refers to Thwaites Eastern Ice Shelf) and Pine Island Glaciers These concerns were reiterated by Mercer's 1978 follow-up study and by another study in 1973. In 1981, scientists also advanced the theory that "the weak underbelly" of the WAIS lay in the Amundsen Sea region, with the collapse of Thwaites and Pine Island Glaciers serving as the trigger for the subsequent collapse of the entire ice sheet. This theory was informed by radar measurement data from research flights over West Antarctica in the 1960s and 1970s, which had revealed that in Pine Island Bay, the glacier bed slopes downwards at an angle, and lies well below the sea level. This topography, in addition to proximity to powerful ocean currents, makes both glaciers particularly vulnerable to increases in ocean heat content. Subsequent research reinforced the hypothesis that Thwaites is the single part of the cryosphere that would have the largest near-term impact on the sea levels, and that it is likely to disappear even in response to climate change which had already occurred. Similarly, there is now widespread agreement that its loss is likely to pave the way for the loss of the entire West Antarctic Ice Sheet, and it has subsequently been used more widely. many others, including leading researchers like Ted Scambos, Eric Rignot, Helen Fricker and Robert Larter have criticized it as alarmist and inaccurate. ==Observations and predictions==

Early observations In 2001, an analysis of radar interferometry data from the Earth Remote Sensing Satellites 1 and 2 by Eric Rignot revealed that the grounding line of Thwaites Glacier had retreated by between 1992 and 1996, while its strongly negative mass balance (annual loss of around 16 billion tonnes of ice, equivalent to 17 km3 of volume) meant that the retreat was going to continue. Further analysis of this data suggested that each increase in ocean temperature would accelerate annual bottom-up melting by . In 2002, a team of scientists from Chile and NASA on board a P-3 Orion from the Chilean Navy collected the first radar sounding and laser altimetry survey of the glacier, confirming the acceleration in thinning and retreat, and concluding that local seabed topography provides no obstacles to rapid retreat. These discoveries prompted an extensive airborne campaign in 2004–2005 by the University of Texas at Austin, followed by NASA's IceBridge Campaign in 2009–2018. Geophysical data collected from IceBridge campaign flights showed that the most vulnerable parts of Thwaites Glacier sit below the sea level. In early 2013, a minor speedup of ice flow was detected, which was later attributed to the activity of subglacial lakes upstream of the grounding line. Altogether, annual ice loss had increased substantially since Rignot's 2001 analysis: from around 16 billion tonnes of ice between 1992 and 1996 International Thwaites Glacier Collaboration In 2017, British and American research institutions founded a five-year research mission named International Thwaites Glacier Collaboration (ITGC). The mission involves over 100 scientists and support staff, with an estimated cost of $50 million across the entire research period. Follow-up ITGC research published in 2023, which observed the underside of the glacier over nine months through a borehole and a robotic mini-submarine called Icefin, found numerous unexpected cracks, or crevasses, where melting proceeded much faster. Crevassed areas amount to 10% of the glacier's underside, yet 27% of its current ice loss. At the same time, their research had also found that stratification between the fresh meltwater from the glacier and the salty ocean water caused the overall melting rate to proceed "far less rapidly than predicted by models". This would lead to a greater outflow from the glacier, increasing its annual contribution to sea level rise from 4% to 5% in the near term. A model created in 2023 suggested that as the outer ice at Thwaites melts due to warm water currents, it erodes in a way which strengthens the flow of those currents. While this climate change feedback was not a surprise, the model estimated that over just the past 12 years, this feedback accelerated melting by 30%, or as much as what is expected from a whole century of a high-emission climate change scenario in the absence of this feedback. If confirmed, this would mean that the melting of Thwaites Glacier can be expected to accelerate at a similar rate for the next century, regardless of whether ocean temperature keeps going up, or stops increasing at all. Other 2023 research suggests that over the 21st century, water temperatures in the entire Amundsen Sea are likely to increase at triple the historical rate even with low or "medium" atmospheric warming and even faster with high warming, which further "worsens the outlook" for the glacier. In 2024, research indicated that instead of a relatively narrow grounding line which separates the parts of the glacier exposed to water and those safely behind them, there is a wider grounding zone of which is regularly exposed to water. Some areas of the glacier are additionally exposed to meltwater flowing another inwards during the strong spring tides. This increased exposure to meltwater would increase the rate of ice loss, potentially doubling the rate of the previous projections. Predicted timelines for glacier collapse A 2014 study, using satellite measurements and computer models, predicted that only the lowest possible warming offered any chance of preserving Thwaites Glacier: otherwise, it will inevitably reach the point of "rapid and irreversible collapse" in the next 200 to 900 years. Once that happens, its retreat would add over 1 mm to the global annual sea level rise, up until it disappears. A 2022 assessment of tipping points in the climate system did not consider Thwaites Glacier on its own, but it did note that the entire West Antarctic Ice Sheet would most likely take 2,000 years to disintegrate entirely once it crosses its tipping point, and the minimum plausible timescale is 500 years, and could be as long as 13,000 years. It also noted that this tipping point for the entire ice sheet is no more than of global warming away, and is very likely to be triggered around the near-future levels of : at worst, it may have even been triggered by now, after the warming passed in the early 21st century. In May 2023, a modelling study considered the future of Thwaites Glacier over the course of 500 years. Due to computational limitations, it was only able to simulate about two-thirds of the glacier catchment (volume of ice equivalent to of the global sea level rise, rather than the contained in the full glacier). It found that the uncertainty about glacier bed friction was almost as important as the future ocean temperature. Another finding was that lower-resolution models (those which simulated the glacier as a mesh of areas) consistently estimated faster break-up than the more detailed models with mesh size of . While in the less-detailed models, practically the entirety of the simulated area was lost around a 250-year mark under the combination of high warming and low friction, higher-resolution simulation showed that about quarter would remain under those conditions, to be lost over 100 more years. Under high warming yet high seabed friction, a quarter was still left at the end of 500 years in the detailed simulations. The same outcome occurred under low warming and low friction. With low warming and high friction, over half of the studied area remained after 500 years. ==Engineering options for stabilization==

in Greenland, as a test. To achieve this, the curtains would have to be placed at a depth of around (to avoid damage from icebergs which would be regularly drifting above) and be long. The authors acknowledged that while work on this scale would be unprecedented and face many challenges in the Antarctic (including polar night and the currently insufficient numbers of specialized polar ships and underwater vessels), it would also not require any new technology and there is already experience of laying down pipelines at such depths. == See also ==