Mapping Antarctica\u2019s ice anchors By stitching together three decades of satellite observations, the team produced the first continent-wide record of grounding line movement since the mid-1990s.<\/p>\n Their results show that 77 percent of Antarctica\u2019s coastline has remained stable since 1996. Elsewhere, concentrated retreat has removed about 4,950 square miles of grounded ice over 30 years.<\/p>\n \u201cThe grounding line is where continental ice meets the ocean, and measuring the movement of grounding lines with satellite-based synthetic aperture radar has been our gold standard for documenting ice sheet<\/a> stability,\u201d said lead author Eric Rignot, a professor of Earth system science at UC Irvine.<\/p>\n \u201cWe\u2019ve known it\u2019s critically important for 30 years, but this is the first time we\u2019ve mapped it comprehensively across all of Antarctica over such a long time span.\u201d<\/p>\n Where ice meets ocean<\/p>\n The grounding line is a kind of hinge point. Upstream, ice is grounded on bedrock. Downstream, it becomes afloat as an ice shelf.<\/p>\n When the grounding line retreats inland, it can signal that the ice sheet is losing its grip on Antarctica, making further loss easier in some settings.<\/p>\n The new map turns that concept into a measured history. Across the full ice sheet, the team calculated an average retreat rate equivalent to 171 square miles per year at the grounding line.<\/p>\n That headline number hides the real story. Most places barely moved. A smaller set of regions moved significantly.<\/p>\n The biggest retreats were concentrated in West Antarctica, the Antarctic Peninsula<\/a>, and sections of East Antarctica.<\/p>\n In those hotspots, the grounding line shifted inland on Antarctica enough to represent sustained withdrawal of grounded ice. Over the full study period, the cumulative loss of grounded area reached nearly 5,000 square miles.<\/p>\n The most dramatic changes took place in West Antarctica\u2019s Amundsen Sea and Getz sectors, where glaciers retreated by about 6 to 25 miles (10 to 40 kilometers).<\/p>\n Several well-known glaciers stood out. Pine Island Glacier retreated by roughly 21 miles, Thwaites Glacier<\/a> retreated by 16 miles, and Smith Glacier receded by about 26 miles.<\/p>\n Rignot links those patterns to the ocean\u2019s role in undercutting ice from below. In many places, the decisive factor is whether relatively warm ocean water can reach the base of floating ice and the grounding zone, thinning the ice and encouraging retreat.<\/p>\n \u201cWhere warm ocean water is pushed by winds to reach glaciers, that\u2019s where we see the big wounds in Antarctica,\u201d Rignot explained.<\/p>\n \u201cIt\u2019s like the balloon that\u2019s not punctured everywhere, but where it is punctured, it\u2019s punctured deep.\u201d<\/p>\n That metaphor captures what the map shows. Antarctica isn\u2019t responding as one uniform system. It\u2019s responding unevenly, with intense change in certain corridors and remarkable stability elsewhere.<\/p>\n Mapping Antarctica from space<\/p>\n The team combined satellite records from multiple countries and space agencies, relying heavily on synthetic aperture radar (SAR).<\/p>\n Unlike optical satellites, SAR can see through clouds and operate during the long polar night, critical advantages in places like Antarctica.<\/p>\n The dataset combined radar observations from major international missions, including ESA\u2019s ERS-1\/2 and Sentinel-1; Canada\u2019s RADARSAT series; Japan\u2019s ALOS\/PALSAR-2; Italy\u2019s COSMO-SkyMed; Germany\u2019s TerraSAR-X; and Argentina\u2019s SAOCOM.<\/p>\n Commercial satellites join the effort<\/p>\n The project did not rely only on government satellites<\/a>. The researchers also incorporated commercial radar data, marking an important step for NASA\u2019s Commercial Satellite Data Acquisition program.<\/p>\n Private providers such as Airbus U.S. and ICEYE US expanded coverage in key regions. Additional observations came through collaboration with ICEYE Ltd. in Finland, which has supported other studies of rapidly changing Antarctic glaciers.<\/p>\n Study co-author Bernd Scheuchl from UC Irvine\u2019s Earth system science program pointed out that combining commercial SAR data with long-running agency missions effectively creates a \u201cvirtual\u201d radar constellation.<\/p>\n This dramatically increases how often scientists can observe critical polar areas.<\/p>\n \u201cThis work shows how commercial SAR data can be used to augment the program of record from agency-run missions,\u201d said Scheuchl.<\/p>\n With access to near-daily observations layered onto decades of international space agency data, researchers can now track polar change with unprecedented consistency.<\/p>\n The result is not just a snapshot. It is a long-term record detailed enough to test why certain regions are especially fragile and to check whether climate models align with what is actually happening on the ice.<\/p>\n Retreat without warm water<\/p>\n Most of the observed retreat patterns line up with the warm-water explanation. But the study highlights one area that doesn\u2019t fit neatly: significant grounding line migration along the northeast Antarctic Peninsula.<\/p>\n \u201cA lot of these places have warm ocean water<\/a> in proximity, but on the east coast of the peninsula, there\u2019s substantial retreat, and we don\u2019t have evidence for warm water,\u201d Rignot said. \u201cSomething else is acting \u2013 it\u2019s still a question mark.\u201d<\/p>\n In that region of Antarctica, several ice shelves had already collapsed before the study period began, and a number of glaciers have since retreated.<\/p>\n Edgeworth Glacier lost 10 miles. Boydell, Sjogren, Bombardier, and Dinsmoor also retreated substantially. <\/p>\n The Hektoria, Green, and Evans glaciers calved 13 miles, 10 miles, and 6 miles past their 1996 grounding line positions.<\/p>\n That cluster of changes suggests an ongoing instability, but one whose exact driver is not yet pinned down by the evidence the team has.<\/p>\n What this means for sea level<\/p>\n Beyond documenting change, the grounding line record is meant to be used. Ice sheet models estimate future sea level rise<\/a>, but they need real-world benchmarks.<\/p>\n \u201cModels have to demonstrate they can match this 30-year record to claim credibility for their projections,\u201d Rignot said.<\/p>\n \u201cThat\u2019s the real value of this observational record. If a model can\u2019t reproduce it, the team will need to go back to the drawing board and figure out what boundary condition or physics are missing.\u201d<\/p>\n The dataset also helps explain why different measurement methods sometimes disagree, particularly in East Antarctica. Confirming that 77 percent of the continent has remained highly stable provides an anchor point for interpreting conflicting signals.<\/p>\n At the same time, the record highlights where losses are actively occurring and where risks are concentrated.<\/p>\n \u201cThe flip side is that we should perhaps feel fortunate that all of Antarctica isn\u2019t reacting right now, because we would be in far more trouble,\u201d Rignot said. \u201cBut that could be the next step.\u201d<\/p>\n The study is published in the Proceedings of the National Academy of Sciences<\/a>.<\/p>\n \u2014\u2013<\/p>\n Like what you read? Subscribe to our newsletter<\/a> for engaging articles, exclusive content, and the latest updates.<\/p>\n Check us out on EarthSnap<\/a>, a free app brought to you by Eric Ralls<\/a> and Earth.com<\/a>.<\/p>\n \u2014\u2013<\/p>\n","protected":false},"excerpt":{"rendered":"Antarctica doesn\u2019t change all at once. It shifts in pieces. For decades, most of the continent\u2019s icy edge…\n","protected":false},"author":2,"featured_media":327841,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[61,60,82],"class_list":{"0":"post-327840","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-ie","9":"tag-ireland","10":"tag-science"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/327840","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/comments?post=327840"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/327840\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media\/327841"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media?parent=327840"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/categories?post=327840"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/tags?post=327840"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
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