14 March 2016, The Guardian, Severe coral bleaching worsens in most pristine parts of Great Barrier Reef. Expert blames global warming, as coral bleaches when water temperatures go above a certain threshold for an extended period of time. Damage to parts of the Great Barrier Reef has worsened, leading authorities to raise the alert to the second-highest level, indicating severe local coral bleaching. The bleaching is worst in the most pristine and remote parts of the reef north of Cairns, according to Terry Hughes, convenor of the National Coral Taskforce. “It’s the jewel in the crown of the Great Barrier Reef and it’s now getting a quite a serious impact from this bleaching event,” he said. “The northern reefs are bleaching quite badly now.” Hughes said it appeared there was some coral death occurring in northern reefs. Russell Reichelt, the chairman of the Great Barrier Reef Marine Park Authority said the area around Lizard Island, 250km north of Cairns, and sites further north, had fared the worst. The US National Oceanographic and Atmospheric Administration predicts bleaching conditions to worsen over the coming weeks. The world is currently in the grips of the third global coral bleaching event. Coral bleaches when water temperatures are raised above a certain threshold for an extended period of time. Hughes, director of the ARC centre of excellence for coral reef studies at James Cook University, said although the strong El Niño occurring now is partly to blame for the bleaching event, the real culprit is global warming caused by carbon emissions. Read More here
Tag Archives: oceans
14 March 2016, The Conversation, Tipping point: how we predict when Antarctica’s melting ice sheets will flood the seas. Antarctica is already feeling the heat of climate change, with rapid melting and retreat of glaciers over recent decades. Ice mass loss from Antarctica and Greenland contributes about 20% to the current rate of global sea level rise. This ice loss is projected to increase over the coming century. A recent article on The Conversation raised the concept of “climate tipping points”: thresholds in the climate system that, once breached, lead to substantial and irreversible change. Such a climate tipping point may occur as a result of the increasingly rapid decline of the Antarctic ice sheets, leading to a rapid rise in sea levels. But what is this threshold? And when will we reach it? What does the tipping point look like? The Antarctic ice sheet is a large mass of ice, up to 4 km thick in some places, and is grounded on bedrock. Ice generally flows from the interior of the continent towards the margins, speeding up as it goes. Where the ice sheet meets the ocean, large sections of connected ice – ice shelves – begin to float. These eventually melt from the base or calve off as icebergs. The whole sheet is replenished by accumulating snowfall. Floating ice shelves act like a cork in a wine bottle, slowing down the ice sheet as it flows towards the oceans. If ice shelves are removed from the system, the ice sheet will rapidly accelerate towards the ocean, bringing about further ice mass loss. A tipping point occurs if too much of the ice shelf is lost. In some glaciers, this may spark irreversible retreat. Read More here
14 March 2016, Nature Geoscience, Impacts of warm water on Antarctic ice shelf stability through basal channel formation. Antarctica’s ice shelves provide resistance to the flow of grounded ice towards the ocean. If this resistance is decreased as a result of ice shelf thinning or disintegration.1 , acceleration of grounded ice can occur, increasing rates of sea-level rise. Loss of ice shelf mass is accelerating, especially in West Antarctica, where warm seawater is reaching ocean cavities beneath ice shelves 2 . Here we use satellite imagery, airborne ice-penetrating radar and satellite laser altimetry spanning the period from 2002 to 2014 to map extensive basal channels in the ice shelves surrounding Antarctica. The highest density of basal channels is found in West Antarctic ice shelves. Within the channels, warm water flows northwards, eroding the ice shelf base and driving channel evolution on annual to decadal timescales. Our observations show that basal channels are associated with the development of new zones of crevassing, suggesting that these channels may cause ice fracture. We conclude that basal channels can form and grow quickly as a result of warm ocean water intrusion, and that they can structurally weaken ice shelves, potentially leading to rapid ice shelf loss in some areas. Read More here. See also Washington Post article here
10 March 2016, Climate News Network, Antarctic techno-fix cannot slow rising seas. Pumping seawater onto the Antarctic landmass to form ice and stop sea levels rising stands little chance of success, scientists say. Sea level rise is likely to be a problem too big to handle. Geoengineers will not be able to magic away the rising tides, according to new research. In particular, they will not be able to pump water from the sea and store it as ice on the continent of Antarctica. That is because, unless they pump it enormous distances, that will only accelerate the flow of the glaciers and it will all end up back in the sea again, a study in the journal Earth System Dynamics says. Geoengineering is sometimes produced as the high-technology solution to the environmental problems of climate change: if humans don’t change their ways and start reducing greenhouse gas emissions, say the proponents of technofix, human ingenuity will no doubt devise a different answer. But, repeatedly, closer examination has made such solutions ever less plausible. Scientists have dismissed the idea that the melting of the Arctic can be reversed, have only tentatively conceded that technology could dampen the force of a hurricane, and have found that – instead of cooling the Earth – attempts to control climate change could either make things worse or seriously disrupt rainfall patterns. On balance, scientists believe that most of the big geo-engineering ideas won’t work. Deep freeze And now a team from the Potsdam Institute for Climate Impact Research has poured cold water on the idea of pouring cold water onto the ice cap. The idea is a simple one. Are sea levels rising 3mm a year because the world is warming? Then pump the sea high onto the Antarctic landmass where it will freeze and stay frozen for a millennium. But to be sure of that, say the Potsdam team, at least 80% of the water would have to be pumped 700 km inland. That would take more than 7% of the annual global primary energy supply just to balance the current rate of sea level rise.But even in a world recently committed to a warming of less than 2°C, the seas are going to go on rising. Sea levels could rise at least 40cms by the end of the century – or possibly 130cms, with devastating consequences for low-lying coastlines: rich megacities might be able to build defences, but the poorest communities would be swept away. Read More here