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
Category Archives: Antarctica
21 May 2016, Climate News Network, Antarctic glacier melt could raise sea level by 3m. A huge glacier in the frozen wastes of East Antarctica, a region previously thought stable, could melt much faster than expected, scientists say. One of Antarctica’s great glaciers could become unstable if global warming continues at the present pace. As warm seas wash the ice shelf, the land-based mass of ice could begin to retreat, cross a critical threshold in the present century and then withdraw 300 kilometres inland. In the course of doing so it would spill tremendous quantities of water into the oceans: enough to raise global sea levels by 2.9 metres and threaten cities that are home to billions. And here is the bad news: glaciologists have known for decades that West Antarctica’s ice sheets are unstable. But the Totten glacier is part of the East Antarctic Ice Sheet, a mass of ice most researchers had believed to be stable and highly unlikely to lose much of its ice, even in a warming world. Scientists from Australia, New Zealand, the US and Britain report in Nature that they explored the underlying geology of the Totten glacier to build up a picture of its advance and retreat over many millions of years. Greater vulnerability “The evidence coming together is painting a picture of East Antarctica being much more vulnerable to a warming environment than we thought,” said Martin Siegert, co-director of the Grantham Institute at Imperial College London. “This is something we should worry about. “Totten Glacier is losing ice now, and the warm ocean water that is causing this loss has the potential to also push the glacier back to an unstable place.” The identification of a weak spot in the bastion of frozen water that embraces East Antarctica is new. But alarm about the rate of melting and the potential for change across the world’s last largely uninhabited continent is not. In the past few years researchers have pinpointed the insidious effect of warming sea currents, and identified immediate hazards to the glaciers of the fast-warming West Antarctic region. Read More here
11 May 2016, The Conversation, Antarctic ice shows Australia’s drought and flood risk is worse than thought. Australia is systematically underestimating its drought and flood risk because weather records do not capture the full extent of rainfall variability, according to our new research. Our study, published today in the journal Hydrology and Earth System Sciences, uses Antarctic ice core data to reconstruct rainfall for the past 1,000 years for catchments in eastern Australia. The results show that instrumental rainfall records – available for the past 100 years at best, depending on location – do not represent the full range of abnormally wet and dry periods that have occurred over the centuries. In other words, significantly longer and more frequent wet and dry periods were experienced in the pre-instrumental period (that is, before the 20th century) compared with the period over which records have been kept. Reconstructing prehistoric rainfall There is no direct indicator of rainfall patterns for Australia before weather observations began. But, strange as it may sound, there is a link between eastern Australian rainfall and the summer deposition of sea salt in Antarctic ice. This allowed us to deduce rainfall levels by studying ice cores drilled from Law Dome, a small coastal ice cap in East Antarctica. It might sound strange, but there’s a direct link between Antarctic ice and Australia’s rainfall patterns. Tas van Ommen, Author provided How can sea salt deposits in an Antarctic ice core possibly be related to rainfall thousands of kilometres away in Australia? It is because the processes associated with rainfall variability in eastern Australia – such as the El Niño/Southern Oscillation (ENSO), as well as other ocean cycles like the Interdecadal Pacific Oscillation (IPO) and the Southern Annular Mode (SAM) – are also responsible for variations in the wind and circulation patterns that cause sea salt to be deposited in East Antarctica (as outlined in our previous research). By studying an ice record spanning 1,013 years, our results reveal a clear story of wetter wet periods and drier dry periods than is evident in Australia’s much shorter instrumental weather record. Read More here
4 May 2016, BBC News, The chasm cutting an Antarctic base adrift. Thirty-six years after he first went there as a young meteorologist, BBC Weather’s Peter Gibbs returned to the current, sixth incarnation of the British Antarctic Survey’s Halley Research Station. There, on “a day with no horizon”, he explored the chasm threatening to cast it adrift. The Brunt Ice Shelf feels like another planet even on the sunniest of days, but when the cloud closes in it turns downright eerie as sky, snow and ice blend into one diffuse white light. Approaching the chasm, the only hint of this 100m-wide gash is a neon glint of blue from the depths of a crevasse in its far wall. Read More here