7 April 2016, Carbon Brief, Analysis: the ‘highly unusual’ behaviour of Arctic sea ice in 2016. The decline of Arctic sea ice is already setting records in 2016, with the winter peak in March clocking in as the lowest since satellite records began, scientists say. A new and fuller summary of this year’s Arctic winter by the US National Snow and Ice Data Centre (NSIDC) confirms the preliminary announcement last week that sea icereached its annual maximum extent on 24 March this year. Covering an area of 14.52m square kilometers, this year’s peak winter extent is a shade smaller than the previous record low set in 2015. But the new NSIDC report adds a lot more detail about what it calls a “highly unusual” and “most interesting” Arctic winter. With abnormally warm conditions right across the Arctic, some regions experienced temperatures 4-8C higher than average. While this meant slower ice growth in some places, in others it caused a dramatic thinning by 30cm in one week, according to early model results. Reaching a peak Arctic sea ice ebbs and flows with the seasons, reaching a maximum extent for the year in February or March and a minimum in September, at the end of the summer melt period. This year, scientists were still waiting expectantly at the end of March, explains the NSIDC report: “Very early in the month, extent declined, raising anticipation that an early maximum had been reached. However, after a period of little change, extent slowly rose again, reaching the seasonal maximum on March 24.” As late as a week ago, scientists still hadn’t ruled out the possibility of a late season surge. But sea ice extent has dropped off quite a bit since then, suggesting the peak has been and gone. You can see this year’s sea ice behaviour in the graph below from NSIDC, which shows sea ice extent over the 2015/6 winter (blue line) up to 3 April compared to previous years. Read More here
Tag Archives: oceans
5 April 2016, The Conversation, This summer’s sea temperatures were the hottest on record for Australia: here’s why. The summer of 2015-2016 was one of the hottest on record in Australia. But it has also been hot in the waters surrounding the nation: the hottest summer on record, in fact.
Graph above: Difference in summer sea surface temperatures for the Australian region relative to the average period 1961-1990.Australian Bureau of Meteorology While summer on land has been dominated by significant warm spells, bushfires, and dryness, there is a bigger problem looming in the oceans around Australia. This summer has outstripped long-term sea surface temperature records that extend back to the 1950s. We have seen warm surface temperatures all around Australia and across most of the Pacific and Indian oceans, with particularly warm temperatures in the southeast and northern Australian regions. Read More here
30 March 2016, Climate Central, Antarctica at Risk of Runaway Melting, Scientists Discover. The world’s greatest reservoir of ice is verging on a breakdown that could push seas to heights not experienced since prehistoric times, drowning dense coastal neighborhoods during the decades ahead, new computer models have shown. A pair of researchers developed the models to help them understand high sea levels during previous eras of warmer temperatures. Then they ran simulations using those models and found that rising levels of greenhouse gases could trigger runaway Antarctic melting that alone could push sea levels up by more than three feet by century’s end. The same models showed that Antarctica’s ice sheet would remain largely intact if the most ambitious goals of last year’s Paris agreement on climate change are achieved. The new findings were published Wednesday in the journal Nature, helping to fill yawning gaps in earlier projections of sea level rise. The models were produced by a collaboration between two scientists that began in the 1990s. In those models, rising air temperatures in Antarctica caused meltwater to seep into cracks in floating shelves of ice, disintegrating them and exposing sheer cliffs that collapsed under their own weight into the Southern Ocean. Similar effects of warming are already being observed in Greenland and in some parts of Antarctica, as greenhouse gas pollution from fossil fuels, farming and deforestation warms the air. Last year was the hottest on record, easily surpassing a record set one year earlier. The ice sheets are also being melted from beneath by warming ocean temperatures. “Sea level has risen a lot — 10 to 20 meters — in warm periods in the past, and our ice sheet models couldn’t make the Antarctic ice sheet retreat enough to explain that,” said David Pollard, a Penn State climate scientist who produced Wednesday’s study with UMass professor Robert DeConto. “We were looking for new mechanisms that could make the ice more vulnerable to climate warming to explain past sea level rise,” Pollard said. Read More here
29 March 2016, The Guardian, Arctic sea ice extent breaks record low for winter. A record expanse of Arctic sea never froze over this winter and remained open water as a season of freakishly high temperatures produced deep – and likely irreversible – changes on the far north. Scientists at the National Snow and Ice Data Centre said on Monday that the sea ice cover attained an average maximum extent of 14.52m sq km (5.607m sq miles) on 24 March, the lowest winter maximum since records began in 1979. The low beats a record set only last year of 14.54m sq km (5.612m sq miles), reached on 25 February 2015. “I’ve never seen such a warm, crazy winter in the Arctic,” said NSIDC director Mark Serreze. “The heat was relentless.” It was the third straight month of record lows in the sea ice cover, after extreme temperatures in January and February stunned scientists. The winter months of utter darkness and extreme cold are typically the time of maximum growth in the ice cap, until it begins its seasonal decline in spring. With the ice cover down to 14.54m sq km, scientists now believe the Arctic is locked onto a course of continually shrinking sea ice – and that is before the 2016 melt season gets underway. Read More here