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
Category Archives: Antarctica
29 November 2016, Carbon Brief, Guest post: Misleading media coverage of Antarctic sea ice paper. Dr Jonathan Day is a polar climate scientist at the University of Reading. His work focuses on understanding and predicting changes in sea ice in the Arctic and Antarctic. Last week, my colleague Tom Edinburgh and I published an article estimating the extent of Antarctic sea ice in the early 1900s, using sea ice observations recorded by explorers of the time. It received an overwhelming amount of coverage in the media. This was largely because it combined a human-interest story about the conditions faced by the early Antarctic explorers with an illuminating result regarding the thorny issue of Antarctic sea ice trends. Despite significant increases in global average temperature, sea ice in the Antarctic has been slightly increasing in extent over recent decades (1979 – present). Although much of the coverage was very well reported, there were other examples of the results being wrongfully interpreted, perhaps wilfully so. Some of the errors led to confusion, such as conflating sea ice with land ice. Others attempted to cast doubt on the link between greenhouse gases and global mean temperature, which was inappropriate and misleading. Read More here
28 November 2016, Geophysical Research Letters (REPORT) Pine Island Glacier has undergone several major iceberg calving events over the past decades. These typically occurred when a rift at the heavily fractured shear margin propagated across the width of the ice shelf. This type of calving is common on polar ice shelves, with no clear connection to ocean-ice dynamic forcing. In contrast, we report on the recent development of multiple rifts initiating from basal crevasses in the center of the ice shelf, resulted in calving further upglacier than previously observed. Coincident with rift formation was the sudden disintegration of the ice mélange that filled the northern shear margin, resulting in ice sheet detachment from this margin. Examination of ice velocity suggests that this internal rifting resulted from the combination of a change in ice shelf stress regime caused by disintegration of the mélange and intensified melting within basal crevasses, both of which may be linked to ocean forcing. Read More here
27 October 2016, Aust Antarctic Division, Impact of East Antarctic glacial melt on sea-level rise. The Australian Antarctic Program will study two glaciers, the Totten and Sørsdal, in East Antarctica this summer to better understand the impact ice melt is having on global sea-level rise. The Totten Glacier, near Australia’s Casey research station, is the largest glacier in East Antarctica, and is showing signs that it is sensitive to warm ocean waters that can increase melt at the base of the ice shelf. Australian Antarctic Division Glaciologist, Dr Ben Galton-Fenzi, said researchers want to better understand how much this glacial melt is driving sea-level rise. “Since the 1900s the global sea-level has risen by around 20 centimetres and by the end of the century it’s projected to rise by up to one metre or more, but this is subject to high uncertainty,” Dr Galton Fenzi said. “These estimates depend critically on understanding Antarctic glaciers, both how much and how fast they melt in a warming climate. This summer researchers will look at how warmer ocean water is melting glaciers and ice shelves from below. “We will land helicopters on the Totten to deploy six GPS units to measure glacial flow speeds and surface elevation changes. Read More here