21 December 2016, Climate News Network, Antarctic rifts launch giant icebergs. Satellite images reveal clue to the hidden cause of fractures in Antarctic shelf ice that are calving huge icebergs into the south polar seas. Scientists in the US have identified an ominous trend in the Southern Ocean − the creation of enormous icebergs as rifts develop in the shelf ice many miles inland. And although three vast icebergs have broken from the Pine Island glacier in West Antarctica and drifted north in this century alone, researchers have only just worked out what has been going on. Their first clue came from a telltale shadow in the south polar ice, caught by a NASA satellite and visible only while the sun was low in the sky, casting a long shadow. It was the first sign of a fracture 20 miles inland, in 2013. Two years later, the rift became complete and the 580 sq km iceberg drifted free of the shelf. Significant collapse “It’s generally accepted that it’s no longer a question of whether the West Antarctic Ice Sheet will melt − it’s a question of when,” says study leader Ian Howat, a glaciologist in the School of Earth Sciences at Ohio State University in the US. “This kind of rifting behaviour provides another mechanism for rapid retreat of these glaciers, adding to the probability that we may see significant collapse of West Antarctica in our lifetimes.” The scientists report in Geophysical Research Letters journal that they had discovered that although shelf ice could be expected to wear at the ocean edge, something else was happening in West Antarctica. The Pine Island glacier is grounded on continental bedrock below sea level, which means that warming ocean water could penetrate far inland beneath the shelf, without anyone being conscious of any change. Read More here
Tag Archives: oceans
16 December 2016, Australian Antarctic Magazine › 2016-2020 › Issue 31, Low winter sea-ice coverage bucks trend. Winter sea-ice coverage around Antarctica was noticeably reduced in September this year, with sea ice extent starting its annual retreat early and setting new daily record lows. The result comes two years after winter sea ice extent around Antarctica reached a record high in September 2014, when it exceeded 20 million square kilometres for the first time since satellite measurements began in 1979. This year, Antarctic sea ice began its annual spring retreat roughly four weeks earlier than average, after peaking at 18.5 million square kilometres on 28 August 2016, which was close to the lowest winter maximum on record. Dr Jan Lieser from the Antarctic Climate and Ecosystems Cooperative Research Centre (ACE CRC) and the Australian Research Council-funded Antarctic Gateway Partnership said it was a surprising finding, given the trend in recent years.“Within the space of just two years we have gone from a record high winter sea-ice extent to record daily lows for this point in the season. This is a great reminder that we are dealing with an extremely variable component of the climate system,” Dr Lieser said. “It’s also a reminder of why it can be unwise to leap to conclusions about the link between Antarctic sea ice and climate change on the basis of one or two years of data. It is the long-term trends that are most important, as well as the regional variability, which is high around Antarctica.” Read More here
13 December 2016, Inside Climate News, ‘The Arctic Is Unraveling,’ Scientists Conclude After Latest Sobering Climate Report. The ill winds of climate change are irrevocably reshaping the Arctic, including massive declines in sea ice and snow and a record-late start to sea ice formation this fall. Those were the sobering conclusions of the 2016 Arctic Report Card released Tuesday. The report card is sponsored by the National Oceanic and Atmospheric Administration (NOAA) and co-authored by more than 50 scientists from Asia, North America and Europe. The data shows that the Arctic is warming at double the rate of the global average temperature. Between October 2015 and September 2016, temperatures over Arctic land areas were 2.0 degrees Celsius above the 1981-2010 baseline, the warmest on record going back to 1900. The report, released at the American Geophysical Union meeting in San Francisco, clearly links the Arctic heatwave to a record-late start to formation of sea ice this fall, and to record high and low seasonal snow cover extent in the Northern Hemisphere. If the extreme warmth recorded in the Arctic this fall persists for the next few years, it may signal a completely new climate in the region, scientists said. Jeremy Mathis, director of NOAA’s Arctic Research Program, said the report highlights the clear and pronounced global warming signal in the Arctic and its effects cascading throughout the environment, like the spread of parasitic diseases in Arctic animals. “We’ve seen a year in 2016 like we’ve never seen before … with clear acceleration of many global warming signals. The Arctic was whispering change. Now it’s not whispering. It’s speaking, it’s shouting change, and the changes are large,” said co-author Donald Perovich, who studies Arctic climate at Dartmouth College. Sustained observations of the Arctic is crucial to making science-based policy decisions, he added, a goal threatened by the inclusion of numerous climate deniers in President-elect Donald Trump’s cabinet. This week, Trump’s transition team posted a new “Energy Independence” website that repeats his previous intentions to open up vast areas for fossil fuel development and to scrap existing climate action plans. Arctic ice doesn’t care about politics, and what happens in the region now is critically important to the U.S., said Rafe Pomerance, chair of Arctic 21 and a member of the Polar Research Board of the National Academies of Sciences, Engineering and Medicine. Read More here
8 December 2016, The Conversation, Climate shenanigans at the ends of the Earth: why has sea ice gone haywire? There is no doubt that 2016 has been a record-breaking year for Earth’s climate. We will have to wait another couple of months for the final tally, but 2016 will be the hottest year in recorded history globally. Average temperatures are well above 1℃ warmer than a century ago. Global average temperatures, and “global warming”, often give the impression of a gradual change in Earth’s climate occurring uniformly across the planet. This is far from the truth – particularly at the ends of the Earth. The Arctic and Antarctic are behaving very differently from the global picture. One particular polar change that has caught the attention of scientists and the media this year has been the state of sea ice. The seasonal growth and decay of sea ice over the Arctic and Southern oceans is one of the most visible changes on Earth. But in the past few months its seasonal progression has stalled, plunging Earth’s sea ice cover off the charts to the lowest levels on record for November. Explaining what has caused this unexpectedly dramatic downturn in sea ice is a tale of two poles. Arctic amplifiers The northern polar region is an epicentre for change in our warming world. On average, the Arctic is warming at around twice the global average rate. This is due to several environmental processes in the Arctic that amplify the warming caused by rising atmospheric greenhouse gas levels. One of these amplifiers is the sea ice itself. …The southern story It’s a different story when we look at the ocean-dominated southern hemisphere. Antarctic climate records point to a delay in some of the effects of “global warming”. The reasons are still debated, partly because of the much shorter climate records that scientists have to work with in the Antarctic. But it is likely that the expansive Southern Ocean is an important climate change dampener that is able to “hide” some of the extra heat being absorbed by our planet beneath the ocean surface where we don’t feel it – yet. Read more here