Friday, 19 August 2016

Miscellaneous reports on climate change - 08/18/2016

Dazzling blue lakes are forming in Antarctica — and they’ve got scientists worried

By Chris Mooney

HANDOUT PHOTO: Satellite image shows a group of lakes atop Langhovde Glacier, East Antarctica. (Satellite image courtesy of DigitalGlobe, Inc.)

17 August, 2016
In a new study, scientists who study the largest ice mass on Earth — East Antarctica — have found that it is showing a surprising feature reminiscent of the fastest melting one: Greenland.
More specifically, the satellite-based study found that atop the coastal Langhovde Glacier in East Antarctica’s Dronning Maud Land, large numbers of “supraglacial” or meltwater lakes have been forming — nearly 8,000 of them in summer between the year 2000 and 2013. Moreover, in some cases, just as in Greenland, these lakes appear to have then been draining down into the floating parts of the glacier, potentially weakening it and making it more likely to fracture and break apart.
This is the first time that such a drainage phenomenon has been observed in East Antarctica, the researchers say — though it was previously spotted on the warmer Antarctic Peninsula and was likely part of what drove spectacular events there like the shattering of the Larsen B ice shelf in 2002.
When it comes to East Antarctica, however, “that’s the part of the continent where people have for quite a long time assumed that it’s relatively stable, there’s not a huge amount of change, it’s very, very cold, and so, it’s only very recently that the first supraglacial lakes, on top of the ice, were identified,” said Stewart Jamieson, a glaciologist at Durham University in the U.K. and one of the study’s authors.
The study was led by Emily Langley of Durham, who worked along with Jamieson and Chris Stokes from her university and Amber Leeson of Lancaster University. The work was recently published online by Geophysical Research Letters.
The research raises concern, for the following reason: Mounting evidence suggests one reason that Greenland has been melting so fast lately is precisely these kinds of lakes. In the summer as air temperatures warm, lakes form on top of the ice sheet, and on its finger-like glaciers that extend outwards into deep ocean fjords.
These lakes can then suddenly disappear all at once, or flow into rivers that drain into the ice below, lubricating the ice and helping to increase the lurch forward of glaciers. Sometimes, researchers have even been able to document fresh water flowing outward directly into the sea from the base of a glacier. That injection of cold fresh water into salty water can then create tornado-like underwater flow patterns at the submerged glacier front that cause further ice loss.
In the new study, Langley and her colleagues find large numbers of lakes forming atop Langhovde Glacier, both inland from, and outward from, the so-called “grounding line,” which is where the marine glacier touches the seafloor far below the ice surface. Past the grounding line, the glacier’s ice begins to float and forms an ice shelf, extending out across the surface of the ocean.
The occurrence of these lakes was strongly related to surface air temperatures — they formed when temperatures rose above zero Celsius, or, above freezing, and formed most frequently in the summer of 2012-2013, which saw 37 days with temperatures above the freezing point.
What we find is that the appearance of these lakes, unsurprisingly, is correlated directly with the air temperature in the region, and so the maximum number of lakes, and the total area of the lakes, as well as the depth of the lakes, all of these things peak when the air temperatures peak,” said Jamieson.
The study found in particular that atop the Langhovde ice shelf, lakes not only formed but appeared to sometimes drain downward, as rapidly as in five days in one case (which is considerably slower than the fastest drainage events in Greenland).

Drainage of some of Langhovde’s supraglacial lakes over a 12 day period between the 14th (left) and 26th (right) of January 2005. Images are compiled from ASTER data provided by the Land Processes Distributed Active Archive Center (LP DAAC) managed by the NASA Earth Science Data and Information System (ESDIS) project.

This raises the concern that these events could possibly be weakening the ice shelf by widening or exploiting fractures within it. But Jamieson said the study could not prove that, in part because it is much harder to observe the consequences of lake draining events in Antarctica than it is in Greenland.
When glaciers lose large parts of their ice shelves, they become less stable and flow faster towards the ocean, contributing to an increased rate of global sea level rise.
The size of the lakes … are probably not big enough to do much at present, but if climate warming continues in the future, we can only expect the size and number of these lakes to increase. So that’s what we’re looking at,” Jamieson said.
He added that the mid-sized Langhovde Glacier is not special when it comes to East Antarctic meltwater lakes — other parts of coastal Antarctica see them too. The reason the study focused on Langhovde is simply that there was a lot of satellite and temperature data available.
In Greenland, when meltwater from the ice sheet’s surface flows out from beneath glaciers and enters the sea, it often takes with it sediment from the glacier bedrock, washing it out as well. This leads to the appearance of what are called “meltwater plumes” in the ocean near glaciers, areas of water with significantly different coloration due to high levels of sediment concentration.
So far, such plumes have not been observed around East Antarctica, Jamieson said.
Still, the lakes, and especially the apparent drainage events, raise a distinct worry about the future of Antarctica, which contains vastly more ice than Greenland and which, thus far, has not been losing nearly as much. “The parallels between these mechanisms, and those observed on Greenland/the Antarctic Peninsula, suggest that lakes may similarly affect rates and patterns of ice melt, ice flow and ice shelf disintegration in East Antarctica,” the study concludes.
Richard Alley, a glaciologist at Penn State who was not involved in the study, noted in an email comment that seeing some Antarctic surface melt is not too surprising. “Across many sensors and studies, there is summertime melting on the surface of Antarctica around the edges, and sometimes in some places extending farther inland than you might think,” he said.
However, Alley continued, we should be very concerned about such melting increasing. Alley referred to a study from earlier this year, by Rob DeConto of the University of Massachusetts, Amherst, and David Pollard of Penn State, which found that surface melt is one factor that could greatly speed total Antarctic ice loss, by increasing the tendency for “hydrofracture” to occur, in which meltwater helps to break apart ice shelves.
The lesson of DeConto and Pollard was that, based on current understanding, avoiding a major expansion of surface melting in Antarctica is taking out insurance against a very large and rapid sea-level rise,” Alley said. “This new work is part of the body of science needed to help us learn just how much warming may be too much if we wish to avoid large and rapid sea-level rise.”
For now, scientists plan to use the instruments available — mainly, at the moment, satellites — to further study the Antarctic lakes.
It’s not hitting the glacier really hard at the moment, this process, but of course, as things warm up, we’d expect it to start doing more damage, like we see in Greenland,” said Jamieson.

The Looming Extinction of Humankind, Explained

For most people, driving with a seat belt tightly strapped around their bodies is a smart habit. Not only is racing down the highway without it illegal—“click it or ticket,” as the slogan goes—but seat belts also “reduce serious crash-related injuries and deaths by about half.” Yet as we've previously estimated, your chances of dying in a car crash are at least 9.5 times lower than dying in a human extinction event.

If this sounds incredible—and admittedly, it does—it’s because the human mind is susceptible to cognitive biases that distort our understanding of reality. Consider the fact that you’re more likely to be killed by a meteorite than a lightning bolt, and your chances of being struck by lightning are about four times greater than dying in a terrorist attack. In other words, you should be more worried about meteorites than the Islamic State or al-Qaeda (at least for now).

A changing climate means less rain and lower water supplies in regions where many people live and much of the planet’s food is produced: the mid-latitudes of the Northern and Southern hemispheres, including the U.S. Southwest, southern Europe and parts of the Middle East, southern Africa, Australia and Chile. As WRI-Aqueduct’s future scenarios for water supply show, diminished water supplies will be apparent in these areas by 2020 — less than four years away — and are expected to grow worse by 2030 and 2040.
Now a new study in the journal Nature provides some of the first evidence that this widely-predicted phenomenon — the movement of clouds and rainfall from the mid-latitudes towards the North and South poles — is already taking place. Just like the retreat of glaciers and polar sea ice, now clouds and rain are retreating poleward.

Arctic Sea Ice Minimum Volumes 1979-2015

This is an animated visualization of the startling decline of Arctic Sea Ice, showing the minimum volume reached every September since 1979, set on a map of New York with a 10km grid to give an idea of scale. It is clear that the trend of Arctic sea ice decline indicates that it'll be ice-free for an increasingly large part of the year, with consequences for the climate.

The rate of ice loss in the Arctic is staggering. Since 1979, the volume of Summer Arctic sea ice has declined by more than 80% and accelerating faster than scientists believed it would, or even could melt.

Based on the rate of change of volume over the last 30 years, I expect the first ice-free summer day in the Arctic Ocean (defined as having less than 1 million km² of sea ice) to happen between 2016 and 2022, and thereafter occur more regularly with the trend of ice-free duration extending into August and October.

Here is some hopeful researc on methane – hopeful, that is, if you see things isolation, rather than take a system approach

Rethinking Methane In the Arctic

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