5 July 2016, Washington Post, This new Antarctica study is bad news for climate change doubters. or a number of years now, climate change skeptics have argued that there’s a key part of the Earth’s climate system that upends our expectations about global warming, and that is showing trends that actually cut in the opposite direction. This supposed contrary indicator is the sea ice that rings the Antarctic continent, and that reached a new all-time record extent of 7.78 million square miles in September 2014 (see above). As that record suggests, this vast field of ice has been expanding in recent years, rather than shrinking. That means it’s doing the opposite of what is happening in the Arctic, where sea ice is declining rapidly — and also that it’s doing the opposite of what we might expect in a warming world. [Climate change skeptics may be about to lose one of their favorite arguments] Scientists don’t fully understand why Antarctic sea ice is growing — suggested explanations have posited more glacial melt dumping cold fresh water into the surrounding seas, or the way the Antarctic ozone hole has changed the circulation of winds around the continent. In a new study in Nature Geoscience, though, researchers with the National Center for Atmospheric Research (NCAR) in Boulder, Colo., along with colleagues from the University of Washington in Seattle and Australia, suggest that the phenomenon is simply the result of natural variability of the climate system — driven, in this case, by changes in the tropical Pacific Ocean that reverberate globally. Read more here
Tag Archives: oceans
8 June 2016, Climate News Network, Puzzle of Antarctica’s long-term ice loss. Analysis of satellite data records reveals that the worrying loss of hundreds of square kilometres of ice along West Antarctica’s coastline has been occurring for decades. Parts of Antarctica are not only losing ice to the ocean, they have been doing so for 40 years. Geoscientists from the University of Edinburgh and a US colleague report in Geophysical Research Letters that they looked at satellite imagery of West Antarctica’s coastline along a 2,000 km stretch and found that the region has lost 1,000 square kilometres of ice in four decades. The surprise is not that melting occurs, but that it has been happening for such a long time. Frazer Christie, a PhD student, and partners analysed data from NASA, the US Geological Survey and the European Space Agency to find that ice has been retreating along almost the entire coast of Antarctica’s Bellingshausen Sea since satellite records began. Some of the largest changes – where ice has thinned rapidly and retreated several kilometres since 1975 – matched those places where the ice front is deepest. “We knew that ice had been retreating from this region recently, but now, thanks to a wealth of freely available satellite data, we know this has been occurring pervasively along the coastline for almost half a century,” Christie says. Colder water He and his colleagues blame warmer ocean waters, rather than warmer atmosphere.But, paradoxically, a study from the University of Washington in Seattle, US, reports that the waters lapping the continent are not warming substantially − because of a steady upwelling of much colder water from the depths of the Southern Ocean. Read More here
7 June 2016, Washington Post, ‘We’ve never seen anything like this’: Arctic sea ice hit a stunning new low in May. The 2016 race downward in Arctic sea ice continued in May with a dramatic new record. The average area of sea ice atop the Arctic Ocean last month was just 12 million square kilometers (4.63 million square miles), according to the National Snow and Ice Data Center (NSIDC). That beats the prior May record (from 2004) by more than half a million square kilometers, and is well over a million square kilometers, or 500,000 square miles, below the average for the month. Another way to put it is this: The Arctic Ocean this May had more than three Californias less sea ice cover than it did during an average May between 1981 and 2010. And it broke the prior record low for May by a region larger than California, although not quite as large as Texas. This matters because 2016 could be marching toward a new record for the lowest amount of ice ever observed on top of the world at the height of melt season — September. The previous record September low was set in 2012. But here’s what the National Snow and Ice Data Center has to say about that: Daily extents in May were also two to four weeks ahead of levels seen in 2012, which had the lowest September extent in the satellite record. The monthly average extent for May 2016 is more than one million square kilometers (386,000 square miles) below that observed in May 2012.In other words, for Arctic sea ice, May 2016 was more like June 2012 — the record-breaking year. Going into the truly warm months of the year, then, the ice is in a uniquely weak state. “We’ve never seen anything like this before,” said Mark Serreze, who directs the center. “It’s way below the previous record, very far below it, and we’re something like almost a month ahead of where we were in 2012.” Granted, the NSIDC called the May numbers “tentative” because of problems with the satellites that scientists rely on to observe the Arctic, but added that they are “supported by other data sources.” Read More here
27 May 2016, The Conversation, Antarctica may not be as isolated as we thought, and that’s a worry. For a long time, we have thought of Antarctica as isolated from the rest of the world. The continent is entirely surrounded by the Southern Ocean, which heaves with giant waves whipped up by intense winds, and is home to the world’s strongest ocean current, the eastward-flowing Antarctic circumpolar current (ACC). The Southern Ocean is associated with several circumpolar oceanic fronts (see image below), where sharp transitions in ocean temperature and salinity occur. One of the most significant of these is the Antarctic polar front, a convergence zone where cold Antarctic water sinks under warmer sub-Antarctic water. Ocean barrier The polar front was considered as a barrier blocking movement of marine plants and animals into and out of Antarctica. Many groups of organisms show strong differences on either side of the front, suggesting northern and southern populations have been separated for a long time. We know from genetic work that some species, such as some molluscs and crustaceans, have managed to cross the front in the past, but there is little evidence that biological movement across the front can or does still occur. Read More here