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
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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
11 March 2016, YALE Climate Connections, Aspen 3rd City in U.S. to Go 100% Renewable. Aspen, Colorado . . . home to a winter playland of skiing, snowshoeing, trekking, and now, 100 percent clean energy. Aspen started transitioning away from fossil fuels in the 1980s with two hydroelectric dams. Then last summer, the city purchased enough wind energy to meet the last 25 percent of its energy needs – the equivalent of taking 4,000 cars off the road for a year. Aspen joined Burlington, Vermont and Greensburg, Kansas in relying solely on clean energy. David Hornbacher, Aspen’s director of utilities and environmental initiatives, says although every community is unique, each one can put together a portfolio of clean power. HORNBACHER: “We’re the third municipal electric utility in the nation to achieve this and each did it by a different route. So let’s let each of these organizations inspire others to find their path to one-hundred percent renewable.” Now Aspen’s renewable energy portfolio includes wind, water, and solar power. By using the forces of nature to power the community, Aspen hopes to inspire other communities to take action. Read More here
11 March 2016, Washington Post, United Airlines is flying on biofuels. Here’s why that’s a really big deal. On Friday, United Airlines will launch a new initiative that uses biofuel to help power flights running between Los Angeles and San Francisco, with eventual plans to expand to all flights operating out of LAX. It’s the first time an American airline will begin using renewable fuel for regular commercial operations, and the occasion is part of a bigger movement when it comes to clean transportation in the U.S. The renewable fuel used to power United’s planes will be coming from a Los Angeles refinery operated by AltAir Fuels, which is using the facility to produce both renewable jet fuel and diesel fuel using a technology developed by Honeywell UOP, a major supplier and technology licenser in the petroleum industry. Back in 2013, AltAir and United announced their partnership, in which United will purchase up to 15 million gallons of biofuel over a three-year period. Friday’s launch will be the first application of that agreement. The flights will use a mixture of 30 percent biofuel and 70 percent traditional fuel, and United says that the biofuel will help reduce greenhouse gas emissions by about 60 percent compared with regular fuel. In general, the idea behind renewable fuels is to use a biological source — for example, plant or animal matter — rather than a geological one, like oil. The Honeywell UOP technology that’s being applied at the AltAir refinery can utilize a range of difference sources, from used cooking oil to algae. The technology has been in the works since 2007, when the company was awarded a grant from DARPA to develop green jet fuel, according to Veronica May, vice president and general manager of renewable energy and chemicals at Honeywell UOP. Currently, its technology allows for the production of diesel fuel that can be used in any proportion with existing diesel engines — up to 100 percent. Its jet fuel can replace up to 50 percent of petroleum fuel in existing aircraft. Altogether, both fuels can offer up to about an 80 percent reduction in greenhouse gas emissions compared with traditional fuel, the company says. Read More here