Climate patterns in the tropics help determine how much snow falls from year to year on Antarctica, among the coldest, windiest, driest places on Earth. New research from the University of Utah shows that tropical conditions and the oceans also influence the continent\u2019s massive ice sheets.<\/p>\n
By analyzing ice cores recovered from the West Antarctic Ice Sheet (WAIS)<\/a> and 20th-century weather data, an interdisciplinary team of scientists demonstrated that what happens in the tropics, especially in the Pacific and Indian oceans, affects how much snow falls in West Antarctica. Tropical climate patterns, such as El Ni\u00f1o and the Madden\u2013Julian Oscillation (MJO), send atmospheric ripples called Rossby waves<\/a> south toward Antarctica. These waves alter wind patterns and storm tracks, influencing how much moisture reaches the ice sheet, according to Ella Hunter, a graduate student in atmospheric sciences.<\/p>\n Her recently published study documented the variability of snow accumulations on the ice sheet over the 20th century.<\/p>\n \u201cOur biggest takeaway was the influence of the tropics on snowfall in Antarctica. Rossby waves can affect temperature, winds and precipitation across the globe,\u201d said Hunter, first author of the paper in JGR Atmospheres<\/a>. \u201cTropical convection or heating in the tropics from sea surface temperatures can create storms that propagate these Rossby waves\u201d\u2014named for meteorologist Carl-Gustaf Rossby. \u201cAnd they are really effective at transporting heat and moisture down to the Antarctic ice sheet,\u201d Hunter said.<\/p>\n The next best thing to weather stations<\/p>\n These findings are based on the research team\u2019s analysis of 25 ice cores, some of which were recovered by geography professor Summer Rupper<\/a> of Utah\u2019s School of Environment, Society & Sustainability, a co-author on the paper.<\/p>\n \u201cWhat\u2019s unique about this study is leveraging all these cores together to look more carefully at the drivers of the variability, not just the trends. We tend to focus on the trends, but variability matters a lot for ice sheet stability,\u201d said Rupper, an expert on Earth\u2019s cryosphere, the parts covered in frozen water, such as glaciers, pack ice and ice sheets. Ancient ice preserves a record of past climate and atmospheric composition, and these regions serve as bellwethers for ongoing climate change.<\/p>\n Much smaller than its eastern counterpart, the WAIS covers 760,000 square miles, with an average thickness of 3,400 feet of ice. If it all melted, its water would raise global sea levels by more than 15 feet.<\/p>\n The U team analyzed West Antarctic ice cores that recorded snow accumulations between 1900 and 1999, along with historical climate datasets, to understand how the ice sheet\u2019s surface mass balance, or SMB, changed over time. SMB is the net gain or loss of ice at the surface, mainly from snowfall and wind redistribution.<\/p>\n Rupper extracted some of the 5-centimeter-diameter cores used in the study during field excursions to Antarctica in 2010 and 2011. They were cut into 1-meter lengths, sliced in half lengthwise, then extensively studied over the years. Rupper retains samples in special freezers on the university\u2019s Salt Lake City campus, along with cores from Greenland\u2019s ice sheet.<\/p>\n To recover the cores, Rupper\u2019s lab used a portable drill that can bring up ice cylinders from the ice sheet\u2019s upper 50 meters, representing snow that fell only in the last century or two.<\/p>\n That\u2019s fairly shallow, but such cores are essential for reconstructing weather patterns from recent decades. Weather stations don\u2019t hold up in Antarctica\u2019s remote, harsh conditions.<\/p>\n \u201cYou can\u2019t keep weather stations maintained. They just get buried by snow. They get blown over. We think about the deep cores, but these shallow cores are essentially filling the gaps of weather stations,\u201d Rupper said. \u201cWithout them, we wouldn\u2019t have any knowledge of the weather of that system. Ice cores can\u2019t record the same things that a weather station would, but we have proxies. What I like about this study is it\u2019s taking advantage of these.\u201d<\/p>\n A tale of two West Antarcticas<\/p>\n A key finding from the study is that West Antarctica does not behave as a single uniform system. The researchers identified two regions\u2014east and west\u2014that respond differently to climate influences.<\/p>\n The ice cores showed that the eastern part of the WAIS received twice as much snow per year as the western part: about 350 millimeters of water equivalent per year compared with 175 millimeters. But more importantly, the study documented the year-to-year variations in accumulations and connected those variations with tropical weather. The team also documented how accumulations trended upward on the eastern part of the ice sheet, but decreased on the western part.<\/p>\n Over the 20th century, the surface mass balance in the east increased at a rate of 0.224 millimeters of water equivalent per year, whereas the west decreased by a rate of 0.087 millimeters per year, Hunter said.<\/p>\n Snowfall was higher in parts of West Antarctica associated with high pressure, which initially perplexed research team leader Court Strong, a professor of atmospheric sciences, until Hunter found an explanation.<\/p>\n \u201cElla did some really helpful detective work by looking at different levels in the atmosphere,\u201d Strong said. \u201cShe found the pattern at the bottom, essentially showing storm systems headed toward the region end up getting deflected inland by that ridge of high pressure. That\u2019s what brings higher snowfall to that part of West Antarctica.\u201d<\/p>\n The study, \u201cTropical controls on West Antarctic Ice Sheet surface mass balance interannual variability in the twentieth century<\/a>,\u201d was published in JGR Atmospheres on May 28. Funding came from the National Science Foundation, with additional support provided by the U.S. Department of Energy\u2019s Biological and Environmental Research<\/a> program, the National Oceanic and Atmospheric Administration Climate Program Office and the NOAA Earth System Research Laboratory Physical Sciences Laboratory. Co-authors include U graduate students Christopher Mitchell and Joey Kruger and former postdoctoral researcher Husile Bai, who is now an assistant professor at Vanderbilt University.<\/p>\n","protected":false},"excerpt":{"rendered":"Climate patterns in the tropics help determine how much snow falls from year to year on Antarctica, among…\n","protected":false},"author":2,"featured_media":615811,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[111,2055,139,69,147,50188],"class_list":["post-615810","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-new-zealand","tag-newswise","tag-newzealand","tag-nz","tag-science","tag-university-of-utah"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/615810","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/comments?post=615810"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/615810\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media\/615811"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media?parent=615810"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/categories?post=615810"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/tags?post=615810"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}