text: Media playback is unsupported on your device Media caption Four things you should know about Antarctica 
   
   Antarctica is shedding ice at an accelerating rate. 
   
   Satellites monitoring the state of the White Continent indicate some 200 billion tonnes a year are now being lost to the ocean as a result of melting. 
   
   This is pushing up global sea levels by 0.6mm annually - a three-fold increase since 2012 when the last such assessment was undertaken. 
   
   Scientists report the new numbers in the journal Nature. 
   
   Governments will need to take account of the information and its accelerating trend as they plan future defences to protect low-lying coastal communities. 
   
   The researchers say the losses are occurring predominantly in the West of the continent, where warm waters are getting under and melting the fronts of glaciers that terminate in the ocean. 
   
   "We can't say when it started - we didn't collect measurements in the sea back then," explained Prof Andrew Shepherd, who leads the Ice sheet Mass Balance Inter-comparison Exercise (Imbie). 
   
   "But what we can say is that it's too warm for Antarctica today. It's about half a degree Celsius warmer than the continent can withstand and it's melting about five metres of ice from its base each year, and that's what's triggering the sea-level contribution that we're seeing," he told BBC News. 
   
   Media playback is unsupported on your device Media caption Andrew Shepherd: "The study incorporates 24 independent satellite assessments" 
   
   Space agencies have been flying satellites over Antarctica since the early 1990s. Europe, in particular, has an unbroken observation record going back to 1992. 
   
   These spacecraft can tell how much ice is present by measuring changes in the height of the ice sheet and the speed at which it moves towards the sea. Specific missions also have the ability to weigh the ice sheet by sensing changes in the pull of gravity as they pass overhead. 
   
   Imbie's job has been to condense all this information into a single narrative that best describes what is happening on the White Continent. 
   
   Glaciologists usually talk of three distinct regions because they behave slightly differently from each other. In West Antarctica, which is dominated by those marine-terminating glaciers, the assessed losses have climbed from 53 billion to 159 billion tonnes per year over the full period from 1992 to 2017. 
   
   On the Antarctic Peninsula, the finger of land that points up to South America, the losses have risen from seven billion to 33 billion tonnes annually. This is largely, say scientists, because the floating ice platforms sitting in front of some glaciers have collapsed, allowing the ice behind to flow faster. 
   
   East Antarctica, the greater part of the continent, is the only region to have shown some growth. Much of this region essentially sits out of the ocean and collects its snows over time and is not subject to the same melting forces seen elsewhere. But the gains are likely quite small, running at about five billion tonnes per year. 
   
   And the Imbie team stresses that the growth cannot counterbalance what is happening in the West and on the Peninsula. Indeed, it is probable that an unusually big dump of snow in the East just before the last assessment in 2012 made Antarctica as a whole look less negative than the reality. 
   
   Globally, sea levels are rising by about 3mm a year. This figure is driven by several factors, including the expansion of the oceans as they warm. But what is clear from the latest Imbie assessment is that Antarctica is becoming a significant player. 
   
   "A three-fold increase now puts Antarctica in the frame as one of the largest contributors to sea-level rise," said Prof Shepherd, who is affiliated to Leeds University, UK. 
   
   "The last time we looked at the polar ice sheets, Greenland was the dominant contributor. That's no longer the case." 
   
   In total, Antarctica has shed some 2.7 trillion tonnes of ice since 1992, corresponding to an increase in global sea level of more than 7.5mm. 
   
   Image copyright ESA Image caption Artwork: European satellites in particular have an unbroken record going back to 1992 
   
   The latest edition of the journal Nature has a number of studies looking at the state of the continent and how it might change in a warming world. 
   
   One of these papers, led by US and German scientists, examines the possible reaction of the bedrock as the great mass of ice above it thins. It should lift up - something scientists call isostatic readjustment. 
   
   New evidence suggests where this process has occurred in the past, it can actually constrain ice losses - as the land rises, it snags on the floating fronts of marine-terminating glaciers. 
   
   "It's like applying the brakes on a bike," said Dr Pippa Whitehouse from Durham University. "Friction on the bottom of the ice, which was floating but has now grounded again, slows everything and changes the whole dynamic upstream. We do think the rebound (in the future) will be fast, but not fast enough to stop the retreat we've kicked off with today's warming. 
   
   "Ocean warming is going to make the ice too thin for this process to help." 
   
   Media playback is unsupported on your device Media caption Pippa Whitehouse: "Push a balloon filled with honey - it rebounds when you remove your hand" 
   
   In Imbie's last assessment, the contribution of Antarctica to global sea-levels was considered to be tracking at the lower end of the projections that computer simulations had made of the possible height of the oceans at the end of the century. The new assessment sees the contribution track the upper end of these projections. 
   
   "At the moment, we have projections going through to 2100, which is sort of on a lifetime of what we can envisage, and actually the sea-level rise we will see is 50/60cm," said Dr Whitehouse. "And that is not only going to impact people who live close to the coast, but actually when we have storms - the repeat time of major storms and flooding events is going to be exacerbated," she told BBC News. 
   
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   In this 2011 photo provided by researcher Hamish Pritchard, summer clouds swirl around the Staccato Peaks of Alexander Island off the Antarctic Peninsula. In a study released Wednesday, June 13, 2018, an international team of ice experts said the melting of Antarctica is accelerating at an alarming... (Associated Press) 
   
   WASHINGTON (AP) — The melting of Antarctica is accelerating at an alarming rate, with about 3 trillion tons of ice disappearing since 1992, an international team of ice experts said in a new study. 
   
   In the last quarter century, the southern-most continent's ice sheet — a key indicator of climate change — melted into enough water to cover Texas to a depth of nearly 13 feet (4 meters), scientists calculated. All that water made global oceans rise about three-tenths of an inch (7.6 millimeters). 
   
   From 1992 to 2011, Antarctica lost nearly 84 billion tons of ice a year (76 billion metric tons). From 2012 to 2017, the melt rate increased to more than 241 billion tons a year (219 billion metric tons), according to the study Wednesday in the journal Nature . 
   
   "I think we should be worried. That doesn't mean we should be desperate," said University of California Irvine's Isabella Velicogna, one of 88 co-authors. "Things are happening. They are happening faster than we expected." 
   
   Part of West Antarctica, where most of the melting occurred, "is in a state of collapse," said co-author Ian Joughin of the University of Washington. 
   
   The study is the second of assessments planned every several years by a team of scientists working with NASA and the European Space Agency. Their mission is to produce the most comprehensive look at what's happening to the world's vulnerable ice sheets in Antarctica and Greenland. 
   
   Outside experts praised the work as authoritative. 
   
   Unlike single-measurement studies, this team looks at ice loss in 24 different ways using 10 to 15 satellites, as well as ground and air measurements and computer simulations, said lead author Andrew Shepherd of the University of Leeds in England. 
   
   It's possible that Antarctica alone can add about half a foot (16 centimeters) to sea level rise by the end of the century, Shepherd said. Seas also rise from melting land glaciers elsewhere, Greenland's dwindling ice sheet and the fact that warmer water expands. 
   
   "Under natural conditions we don't expect the ice sheet to lose ice at all," Shepherd said. "There are no other plausible signals to be driving this other than climate change." 
   
   Shepherd cautioned that this is not a formal study that determines human fingerprints on climate events. 
   
   Forces "that are driving these changes are not going to get any better in a warming climate," said University of Colorado ice scientist Waleed Abdalati, a former NASA chief scientist who wasn't part of the study team. 
   
   In Antarctica, it's mostly warmer water causing the melt. The water nibbles at the floating edges of ice sheets from below. Warming of the southern ocean is connected to shifting winds, which are connected to global warming from the burning of coal, oil and natural gas, Shepherd said. 
   
   More than 70 percent of the recent melt is in West Antarctica. 
   
   The latest figures show East Antarctica is losing relatively little ice a year — about 31 tons (28 metric tons) — since 2012. It was gaining ice before 2012. 
   
   So far scientists are not comfortable saying the trend in East Antarctica will continue. It is likely natural variability, not climate change, and East Antarctica is probably going to be stable for a couple decades, said study co-author Joughin. 
   
   Another study in Nature on Wednesday found that East Antarctic ice sheet didn't retreat significantly 2 million to 5 million years ago when heat-trapping carbon dioxide levels were similar to what they are now. 
   
   Twila Moon, a research scientist at the National Snow and Ice Data Center who wasn't part of the studies, said "ice-speaking, the situation is dire." 
   
   ___ 
   
   Follow Seth Borenstein on Twitter: @borenbears . His work can be found here . 
   
   ___ 
   
   The Associated Press Health & Science Department receives support from the Howard Hughes Medical Institute's Department of Science Education. The AP is solely responsible for all content.
target: – Scientists monitoring ice loss in Antarctica have chilling news: The melting rate has accelerated alarmingly and the ice sheet is now shedding more than 200 billion tons a year, according to a study involving 88 scientists published in the journal Nature. The researchers say the rate of ice loss has tripled over the last decade and the melting ice sheets are now pushing up sea levels around the world by around a half-millimeter every year, reports the BBC. Antarctica was losing around 49 billion tons of ice a year in the mid-1990s, which went up to an average 219 billion tons a year between 2012 and 2017, the study found. The researchers, who used satellite data going back more than 25 years, say most of the melting ice comes from the West Antarctic sheet, parts of which are in a "state of collapse"—and modest ice growth in the East Antarctic is nowhere near enough to offset it. "The increasing mass loss that they’re finding is really worrying, particularly looking at the West Antarctic, the area that’s changing most rapidly," University of Waterloo glaciologist Christine Dow tells the Washington Post. "And it’s the area that we’re most worried about, because it’s below sea level." Antarctica has lost a total of around 3 trillion tons of ice since 1992 and will be contributing more and more to sea level rise if the current trend continues, warn researchers, who say climate change is the only plausible explanation for the ice loss. "I think we should be worried. That doesn't mean we should be desperate," says study co-author Isabella Velicogna of the University of California Irvine, per the AP. "Things are happening. They are happening faster than we expected."