by Deep Green Resistance News Service | Sep 1, 2013 | Climate Change
By Jeremy Hance / Mongabay
As if ocean acidification and climate change weren’t troubling enough (both of which are caused by still-rising carbon emissions), new research published in Nature finds that ocean acidification will eventually exacerbate global warming, further raising the Earth’s temperature.
Scientists have long known that tiny marine organisms—phytoplankton—are central to cooling the world by emitting an organic compound known as dimethylsulphide (DMS). DMS, which contains sulfur, enters the atmosphere and helps seed clouds, leading to a global cooling effect. In fact, in the past scientists have believed that climate change may actually increase DMS emissions, and offset some global warming, but they did not take into account the impact of acidification.
Researchers, headed by Katharina Six with the Max Planck Institute for Meteorology, tested how acidification affects phytoplankton in the laboratory by lowering the pH (i.e. acidifying) in plankton-filled water tanks and measuring DMS emissions. When they set the ocean acidification levels for what is expected by 2100 (under a moderate greenhouse gas scenario) they found that cooling DMS emissions fell.
Plugging the results into global modeling system, Six says, “we get an extra warming of 0.23 to 0.48 degree Celsius from the proposed impact [by 2100],” adding that “less sulphur results in a warming of the Earth surface.” This creates a positive feedback loop that will likely have impacts that are anything but positive, according to scientists.
To date, the world has warmed approximately 0.8 degrees Celsius in the last century with a variety of impacts including worsening severe weather, rising sea levels, melting glaciers and sea ice, and imperiled species.
Six also notes that a warmer world does not necessarily mean a more productive world for phytoplankton as has been argued by researchers in the past.
“In former times it was assumed that phytoplankton potentially growth better in a warmer ocean,” she explained to mongabay.com. “However, the basis for plant growth is the supply with nutrients. As the oceans will stabilize in the warmer climate, fewer nutrients will be transported into the sunlight zone. Earth system models, like the MPI-ESM that was used for our study, project a decrease in primary production of 17 percent at the end of this century for a moderate climate scenario. The impact from climate change alone led to a decrease in DMS emission of 7 percent.”
The results are still preliminary as researchers have yet to test how DMS emissions will by impacted in tropical and subtropical waters, focusing to date on polar and temperate waters. In addition, further modeling should be done in order to understand possible uncertainties according to Six.
Still, the evidence is strong enough that the researchers write in the paper that “this potential climate impact mechanism of ocean acidification should be considered in projections of future climate change.” Essentially raising current estimates for a moderate climate scenario by around 10 percent.
Ocean acidification, which has been dubbed “climate change’s equally evil twin” by U.S. National Oceanic and Atmospheric Administration (NOAA)’s Jane Lubchenco, is expected to have largely negative impacts on many marine species, including dissolving the shells of crustaceans and molluscs, hampering coral reefs, and even changing how far fish can hear.
So, how do we stop this from happening?
“There is only one answer,” Katharina Six told mongabay.com, “the abatement of fossil fuel emissions.”
From Mongabay: “Bad feedback: ocean acidification to worsen global warming“
by Deep Green Resistance News Service | Aug 30, 2013 | Climate Change, Protests & Symbolic Acts
By Sarah Moles / Generation Alpha
Seven environmental activists today stole a ‘Carbon Bomb’ from the offices of transport company Aurizon (link www.aurizon.com.au) in Brisbane, Australia. The action signified the launch of their shop front hunger strike, pressuring Aurizon to withdraw planned capital from the largest coal complex in the world, planned for the Galilee Basin in their state of Queensland. Burning the coal from this complex is forecast to release over 700 million tons of carbon pollution each year, more than the total emissions Australia, the UK or Canada.
The hunger strike is part of the Over Our Dead Bodies (link www.OverOurDeadBodies.net) campaign, run by 40,000-strong Generation Alpha (link www.facebook.com/GenerationAlpha). Campaign coordinator Ben Pennings told the gathering media:
We’re here because Aurizon plan to bail out debt-ridden Indian company GVK, allowing them to dig up the first 3 coal mines in the Galilee Basin. Mining the Galilee is like setting off a bomb. This amount of carbon pollution is a deadly catastrophe, an environmental crime. So we’ve taken this carbon bomb from Aurizon to symbolize our intentions to stop them.
The campaign is designed to provide unique financial pressure on Aurizon, a rail freight company that specializes in coal. Activists in Australia but also internationally are committing to actions on the campaign website (link www.OverOurDeadBodies.net) that will cost Aurizon significant time and money. These include direct action and civil disobedience aimed at delaying infrastructure, hampering day-to-day operations and even targeting the company’s CEO and board members. Mr. Pennings said:
Aurizon have been ignoring the legitimate concerns of the environment movement for too long. So activists around the country are getting ready for direct action, to make the precarious finances of this complex even more so. Governments aren’t protecting our future, so we will.
The activists included former Australian Senator Andrew Bartlett (link http://en.wikipedia.org/wiki/Andrew_Bartlett). Andrew expressed his frustration with the lack of political engagement on climate change, saying:
We will be on a public hunger strike from today, engaging community members to understand that we can’t have the biggest coal complex on the planet, we can’t ignite this carbon bomb, and still avoid catastrophic climate change. We don’t want short-term mining projects that destroy communities and the environment. We want renewable power and long-term sustainable industries integrated into our communities.
For more on the Over Our Dead Bodies campaign, see http://www.OverOurDeadBodies.net
For the Hunger Strikers blog, see http://www.OverOurDeadBodies.net/blog
Generation Alpha’s Facebook page: http://www.facebook.com/GenerationAlpha
by Deep Green Resistance News Service | Aug 2, 2013 | Climate Change, Toxification
By Fiona Harvey / The Guardian
A major survey of the coral reefs of the Caribbean is expected to reveal the extent to which one of the world’s biggest and most important reserves of coral has been degraded by climate change, pollution, overfishing and degradation.
The Catlin scientific survey will undertake the most comprehensive survey yet of the state of the region’s reefs, starting in Belize and moving on to Mexico, Anguilla, Barbuda, St Lucia, Turks & Caicos, Florida and Bermuda.
The Catlin scientists said the state of the regions’ reefs would act as an early warning of problems besetting all of the world’s coral. As much as 80% of Caribbean coral is reckoned to have been lost in recent years, but the survey should give a more accurate picture of where the losses have had most effect and on the causes.
Loss of reefs is also a serious economic problem in the Caribbean, where large populations depend on fishing and tourism. Coral reefs provide a vital home for marine creatures, acting as a nursery for fish and a food resource for higher food chain predators such as sharks and whales.
Stephen Catlin, chief executive of the Catlin Group, said: “It is not only important that scientists have access to this valuable data, but companies such as ours must understand the impact that significant changes to our environment will have on local economies.”
Globally, coral reefs are under threat. The future of the Great Barrier Reef in Australia is in doubt as mining and energy companies want to forge a shipping lane through it to form a more direct link with their export markets.
Warming seas owing to climate change can lead to coral being “bleached” – a state where the tiny polyps that build the reefs die off. The US government’s National Oceanic and Atmospheric Administration predicts increasing frequency and severity of mass bleaching events as global warming takes effect.
Richard Vevers, director of the project, told the Guardian that one important role of the new survey would be to describe a new “baseline” to establish how far such problems have taken their toll to date, which will enable future scientists to judge how degradation – or conservation – progresses.
He said the team of scientists would also probe the underlying reasons for such degradation, with a view to informing conservation efforts.
The team will use satellite data as well as direct observations to assess the reefs. As part of the survey, they will develop software that marine scientists can apply to other reefs around the world. A new camera has been constructed to assist their efforts.
Vevers said: “The Caribbean was chosen to launch the global mission because it is at the frontline of risk. Over the last 50 years 80% of the corals have been lost due mainly coastal development and pollution. They now are also threatened by invasive species, global warming and the early effects of ocean acidification — it’s the perfect storm.”
From The Guardian: http://www.theguardian.com/environment/2013/aug/01/caribbean-coral-reef-loss
by Deep Green Resistance News Service | Aug 1, 2013 | Climate Change
By Bjorn Carey / Stanford University
The planet is undergoing one of the largest changes in climate since the dinosaurs went extinct. But what might be even more troubling for humans, plants and animals is the speed of the change. Stanford climate scientists warn that the likely rate of change over the next century will be at least 10 times quicker than any climate shift in the past 65 million years.
If the trend continues at its current rapid pace, it will place significant stress on terrestrial ecosystems around the world, and many species will need to make behavioral, evolutionary or geographic adaptations to survive.
Although some of the changes the planet will experience in the next few decades are already “baked into the system,” how different the climate looks at the end of the 21st century will depend largely on how humans respond.
The findings come from a review of climate research by Noah Diffenbaugh, an associate professor of environmental Earth system science, and Chris Field, a professor of biology and of environmental Earth system science and the director of the Department of Global Ecology at the Carnegie Institution. The work is part of a special report on climate change in the current issue of Science.
Diffenbaugh and Field, both senior fellows at the Stanford Woods Institute for the Environment, conducted the targeted but broad review of scientific literature on aspects of climate change that can affect ecosystems, and investigated how recent observations and projections for the next century compare to past events in Earth’s history.
For instance, the planet experienced a 5 degree Celsius hike in temperature 20,000 years ago, as Earth emerged from the last ice age. This is a change comparable to the high-end of the projections for warming over the 20th and 21st centuries.
The geologic record shows that, 20,000 years ago, as the ice sheet that covered much of North America receded northward, plants and animals recolonized areas that had been under ice. As the climate continued to warm, those plants and animals moved northward, to cooler climes.
“We know from past changes that ecosystems have responded to a few degrees of global temperature change over thousands of years,” said Diffenbaugh. “But the unprecedented trajectory that we’re on now is forcing that change to occur over decades. That’s orders of magnitude faster, and we’re already seeing that some species are challenged by that rate of change.”
Some of the strongest evidence for how the global climate system responds to high levels of carbon dioxide comes from paleoclimate studies. Fifty-five million years ago, carbon dioxide in the atmosphere was elevated to a level comparable to today. The Arctic Ocean did not have ice in the summer, and nearby land was warm enough to support alligators and palm trees.
“There are two key differences for ecosystems in the coming decades compared with the geologic past,” Diffenbaugh said. “One is the rapid pace of modern climate change. The other is that today there are multiple human stressors that were not present 55 million years ago, such as urbanization and air and water pollution.”
Record-setting heat
Diffenbaugh and Field also reviewed results from two-dozen climate models to describe possible climate outcomes from present day to the end of the century. In general, extreme weather events, such as heat waves and heavy rainfall, are expected to become more severe and more frequent.
For example, the researchers note that, with continued emissions of greenhouse gases at the high end of the scenarios, annual temperatures over North America, Europe and East Asia will increase 2-4 degrees C by 2046-2065. With that amount of warming, the hottest summer of the last 20 years is expected to occur every other year, or even more frequently.
By the end of the century, should the current emissions of greenhouse gases remain unchecked, temperatures over the northern hemisphere will tip 5-6 degrees C warmer than today’s averages. In this case, the hottest summer of the last 20 years becomes the new annual norm.
“It’s not easy to intuit the exact impact from annual temperatures warming by 6 C,” Diffenbaugh said. “But this would present a novel climate for most land areas. Given the impacts those kinds of seasons currently have on terrestrial forests, agriculture and human health, we’ll likely see substantial stress from severely hot conditions.”
The scientists also projected the velocity of climate change, defined as the distance per year that species of plants and animals would need to migrate to live in annual temperatures similar to current conditions. Around the world, including much of the United States, species face needing to move toward the poles or higher in the mountains by at least one kilometer per year. Many parts of the world face much larger changes.
The human element
Some climate changes will be unavoidable, because humans have already emitted greenhouse gases into the atmosphere, and the atmosphere and oceans have already been heated.
“There is already some inertia in place,” Diffenbaugh said. “If every new power plant or factory in the world produced zero emissions, we’d still see impact from the existing infrastructure, and from gases already released.”
The more dramatic changes that could occur by the end of the century, however, are not written in stone. There are many human variables at play that could slow the pace and magnitude of change – or accelerate it.
Consider the 2.5 billion people who lack access to modern energy resources. This energy poverty means they lack fundamental benefits for illumination, cooking and transportation, and they’re more susceptible to extreme weather disasters. Increased energy access will improve their quality of life – and in some cases their chances of survival – but will increase global energy consumption and possibly hasten warming.
Diffenbaugh said that the range of climate projections offered in the report can inform decision-makers about the risks that different levels of climate change pose for ecosystems.
“There’s no question that a climate in which every summer is hotter than the hottest of the last 20 years poses real risks for ecosystems across the globe,” Diffenbaugh said. “However, there are opportunities to decrease those risks, while also ensuring access to the benefits of energy consumption.”
From Stanford News: http://news.stanford.edu/news/2013/august/climate-change-speed-080113.html
by Deep Green Resistance News Service | Jul 10, 2013 | Climate Change, Mining & Drilling
By Joshua Headley / Deep Green Resistance New York
If you’ve been a sentient being for the last few months, you’ve probably been watching some of the most curious weather events happening throughout the world.
Of particular concern for many scientists has been the Arctic sea ices melt, which dropped to its lowest level on record last summer. In the first few months of this year, large cracks were witnessed in the sea ice, indicating a great possibility that it has entered a death spiral and will disappear completely in the summer months within the next two years.
The rapid melt (and eventual disappearance) of the ice is having drastic affects on the jet stream in the northern hemisphere, creating powerful storms and extreme weather events, largely outside the comprehension of many scientists.
Jeff Masters, meteorology director at the private service Weather Underground states: “I’ve been doing meteorology for 30 years and the jet stream the last three yeas has done stuff I’ve never seen. […] The fact that the jet stream is unusual could be an indicator of something. I’m not saying we know what it is.”
For example, in May there were wildfires caused by excessive heat in California while at the same time there was more than a foot of snow in Minnesota. Spring in Colorado started with early wildfires and was subsequently followed by massive flooding. Massive floods have been devastating much of the northern hemisphere this spring, including Canada, the United States, Europe, India, and Russia.
Last week, Alaska saw its hottest days on record where the town of McGrath, Alaska hit 94 F degrees while just a few weeks earlier the local temperature was 15 F degrees. There have also been extreme heat waves throughout the southwest United States, some temperatures above 130 F degrees, also resulting in wildfires that spread to more than 6,000 acres in two days and killed 19 firefighters in Arizona.
Today, the concentration of carbon dioxide in the atmosphere is at 400 ppm – a level not seen on this planet since the Pliocene epoch, nearly 3 to 5 million years ago when the average global temperature of the planet was 2-3 C degrees warmer than today. The International Energy Agency has recently warned that the planet is on track for 3.6 to 5.3 C degrees warming.
This is catastrophic – most scientists have recognized any significant rise above 1 C will usher in irreversible changes that will threaten nearly all biological life on this planet.
Carbon dioxide has an approximate thirty-year time lag between its release into the atmosphere and its corresponding affect on average global temperature. Even if we stop all emissions today – keeping it at 400 ppm – we still have nearly thirty years of warming and climatic changes to undergo.
And right now, nothing that we are currently observing matches up with any of the models that we have – a stark acknowledgment that this historical moment we find ourselves in exists largely beyond our ability to comprehend it let alone predict its movement.
We are in uncharted territory – we are facing challenges never before experienced in the history of the human species. This presents a grave problem: if the best science we have today cannot accurately offer any model predictions for the path that we are currently on, how can we effectively plan for the future?
The honest truth: we can’t. We cannot effectively plan for a future that is beyond all known human experience.
The best that we can do now is stop exacerbating the problem – stop contributing to the rapidly accelerating decline and destruction of the Earth’s biosphere and ecosystems.
Quite literally: we have to completely dismantle the industrial economy, we have to do it soon, and really, we should have done it yesterday.
But even still, grinding industrial civilization to a complete halt today is only guaranteed to mitigate the pace at which we’re running – it is not yet clear that it will ultimately alter our direction. We have, at minimum, thirty more years of incomprehensible climate disruptions and changes to undergo no matter what happens today or tomorrow. Our only chance to still have a thriving and living planet following the coming decades is by making a complete, radical and rapid shift from the industrial economy.
The logic of industrial civilization and capitalism is immediacy – grow as quickly as possible, generate maximum profits in the shortest time, and deal with consequences and crises later (if at all). Long-term planning and strategizing is antithetical to, and bears no consequence on, the drive for capital accumulation, expansion, and domination.
This process, within the last 30-40 years alone, has resulted in such an expansive project of urbanization around the world that capitalism has triumphed over (read: conquered, murdered, and erased) all other ways of existing on this planet, human and non-human. We now live in a truly global industrial civilization – a monoculture of unprecedented scope; a totality of being and of tyranny.
To oppose this project of endless growth and centralization of control, we need to enter into the logic of a truly oppositional culture – a fundamental and radical break from of our entire material reality. This entails a complete negation of our current standard of living and entire way of being in the world. Anything short of this negation will only exacerbate the problem.
Acknowledging this does not mean that the task at hand is easy or that a majority of people will accept it as truth. In fact, even amidst collapse, most people will not resist the status quo and are likely to fight to the death to protect it.
As Derrick Jensen has stated:
If your experience is that your water comes from the tap and that your food comes from the grocery store then you are going to defend to the death the system that brings those to you because your life depends on that; if your experience is that your water comes from a river and that your food comes from a land base then you will defend those to the death because your life depends on them. So part of the problem is that we have become so dependent upon this system that is killing and exploiting us, it has become almost impossible for us to imagine living outside of it and it’s very difficult physically for us to live outside of it.
But this also does not mean that the task at hand is any less true. It does mean, however, that if we wish to build our struggle for a truly just and sustainable future we must first do away with our delusions, re-focus our strategies to the most effective, and be radically uncompromising in our vision.
On June 25th, Barack Obama – a president whom, despite his rhetoric of care, spent all of the last five years of his presidency completely ignoring climate change – finally addressed the nation in a speech that was supposed to signal a “serious plan forward.”
Many “environmental” groups along with the mainstream media heralded the speech as being progressive and a great commitment to the crisis at hand. In reality, much of the speech was full of nothing more than the doublespeak typical of his presidential legacy.
In a move that many considered to be a “big victory,” the president merely stated that he will ask the State Department not to approve the final construction of the Keystone XL pipeline unless it can first determine that it “will not lead to a net increase in greenhouse gas emissions.”
This is certainly a sly trick designed to pacify a building resistance, an attempt to re-frame the debate and make it appear as if our best interests are dutifully being considered. However, to even pretend that it is at all possible that this pipeline would not lead to a net increase in greenhouse gas emissions is delusional.
While the fight against the KXL has been a fight against a pipeline, it is predominantly being waged as a fight against tar sands oil production entirely. It is incredibly easy to argue that one specific pipeline will not result in significant GHG emissions if we isolate it from the very process that demands its existence in the first place.
It is the extraction process itself that is the net greenhouse gas emitter destroying the planet – not merely the nodes at which its product is transported and consumed. Although this infrastructure should be equally opposed and dismantled, stopping one pipeline being built will only mean that others will replace it or other means will be developed to export its goods.
We should settle for nothing less than a complete end to all extraction processes. It is not even close to a victory until that happens.
Despite his attempt to appease environmentalists with this speech, there were some activist groups that were rightfully confused and enraged with his hypocritical stance. In a speech meant to signal commitment to slow climate change, President Obama continued to praise and support the fossil fuel industry and hydraulic fracturing for natural gas.
Chris Williams, author of Ecology and Socialism, examines the rhetoric and reality of this latest speech, providing a great reminder of whose interests this president actually serves – those of the ruling class. He also outlines some new ideas for Obama’s consideration:
- If you’re serious about stopping global warming, you need to veto KXL.
- If you’re serious about moving away from dirty energy, then there needs to be a strict timeline established for the complete phasing-out of all coal and nuclear plants by 2030 and their replacement, not with natural gas or nuclear, but with wind and solar power.
- If you’re really serious about carbon pollution, you can’t with any honesty discuss solutions without making massive cuts in military spending. The Department of Defense is responsible for 80 percent of the U.S. government’s energy consumption, and the U.S. military is by far the biggest polluter on the planet. Radical reductions in spending on the Pentagon are essential for human survival.
- You made no mention of the need for enormous investment in and expansion of public transit. If you’re serious about addressing climate change and making our cities more livable and the air more breathable, you will take the money you just saved by cutting military expenditures and apply it to the construction of new rail, light rail, tram and bus service, between and within cities, obviating the need for cars.
These ideas are some of the more prevalent solutions that are often tossed around in environmental and social justice circles. While the intention may be sincere, simply advocating for a shift from “dirty energy” (coal, oil, nuclear) to “clean energy” (solar, wind, tidal, geothermal, etc.) does a great disservice for generating informed decision-making at such a critical historical moment.
While these energies have many flaws, one of the greatest problems with their proponents is that they do not fundamentally put into question our standard of living or way of being in the world.
An often-cited study by these proponents is the work of Mark Z. Jacobson who, mere weeks after Hurricane Sandy devastated the Northeast U.S., presented the economic argument for investing in renewable energies. His plan calls for a complete shift off fossil fuels and towards a rapid investment in wind and solar power for the entire state of New York by the year 2030.
Not only was this study completed on the premise that our culture does not dramatically change its standard of living, the study fails to even acknowledge the resources required to build these new energy infrastructures.
These energy sources are not free from fossil fuels and are dependent on rare earth metals and minerals; this sort of rapid technological and social shift will require massive extractive processes – a price we simply cannot afford if we wish to stop the destruction of this planet.
If we wish to create a “sustainable” future that is also just, a question that should be immediately asked is: Where are these resources coming from? From whose land will we steal from in order to build this renewable-energy utopia? Despite the fact that New York State ranks in or near the top third of U.S. mineral production, none of the crucial metals and minerals currently used for the development of solar panels and wind turbines can be found here – we will have to steal these resources from some other land base.
Even more problematic, Jacobson’s study does not entirely take into consideration (to the extent that it is possible) the severe climatic disruptions we are unavoidably set to experience in the coming decades. The disappearance of the Arctic sea ice in the next few years will result in rising sea levels that could displace more than 400 million people globally. Is it worth the investment for an entirely new energy infrastructure that may ultimately be irrelevant by the time it can be actualized?
To continue to advocate for these “solutions,” is to continue living in the delusion that we can have our current standard of living and have a planet too. As Robert Jensen articulates in his article, “Get Apocalyptic: Why Radical is the New Normal“:
…Toughest to dislodge may be the central illusion of the industrial world’s extractive economy: that we can maintain indefinitely a large-scale human presence on the earth at something like current First-World levels of consumption. The task for those with critical sensibilities is not just to resist oppressive social norms and illegitimate authority, but to speak a simple truth that almost no one wants to acknowledge: The high-energy/high-technology life of affluent societies is a dead end. We can’t predict with precision how resource competition and ecological degradation will play out in the coming decades, but it is ecocidal to treat the planet as nothing more than a mine from which we extract and a landfill into which we dump.
We cannot know for sure what time the party will end, but the party’s over.
Our primary goal and vision for the world is a living planet. Nothing else matters. The biggest challenge to that goal is the industrial economy and it’s a moving target. If we have any chance at stopping it we cannot have a strategy that is focused solely on the injustices of today. Our actions and strategies should be based on where we’re heading – and where we’re heading is nothing short of near-term extinction.
This is not hyperbole or metaphor. 200 species went extinct today and another 200 species will go extinct tomorrow. 400,000 people die every year from climate-related deaths. A war has been declared against the living the world and we ought to start articulating which side we’re on, and we ought to seriously start fighting back.
I’m reminded of a recent quote from MEND (Movement for the Emancipation of the Niger Delta), a militant group successful at halting more than 28% of Nigeria’s oil output between 2006 and 2009, which articulates the situation succinctly:
From today, every tanker vehicle we find distributing petroleum products including propane gas has become a legitimate target in our war against injustice, corruption, despotism and oppression.
This is the kind of vigor we need to be generating in our own movement. Never before have the lines between those who seek to destroy this planet and those who seek a radically different future, been so clearly drawn and defined. Yet, there is a degree of hesitancy within the majority of activist circles in the West that is painstakingly paralyzing our movements from reaching its goals.
If we stand in solidarity with all the human and non-human lives that have been lost, or are routinely brutalized to this way of life, we must fundamentally reject our own standards of living and ideals about how to enter into relationship with each other and with the land. Knowing that we have now entered a historical moment of incomprehensible climatic disruptions and changes for the foreseeable future, we’d be better to do away with our delusions sooner rather than later.
BREAKDOWN is a biweekly column by Joshua Headley, a writer and activist in New York City, exploring the intricacies of collapse and the inadequacy of prevalent ideologies, strategies, and solutions to the problems of industrial civilization.
by Deep Green Resistance News Service | Jun 18, 2013 | Climate Change
By NASA
Ocean waters melting the undersides of Antarctic ice shelves are responsible for most of the continent’s ice shelf mass loss, a new study by NASA and university researchers has found.
Scientists have studied the rates of basal melt, or the melting of the ice shelves from underneath, of individual ice shelves, the floating extensions of glaciers that empty into the sea. But this is the first comprehensive survey of all Antarctic ice shelves. The study found basal melt accounted for 55 percent of all Antarctic ice shelf mass loss from 2003 to 2008, an amount much higher than previously thought.
Antarctica holds about 60 percent of the planet’s fresh water locked into its massive ice sheet. Ice shelves buttress the glaciers behind them, modulating the speed at which these rivers of ice flow into the ocean. Determining how ice shelves melt will help scientists improve projections of how the Antarctic ice sheet will respond to a warming ocean and contribute to sea level rise. It also will improve global models of ocean circulation by providing a better estimate of the amount of fresh water ice shelf melting adds to Antarctic coastal waters.
The study uses reconstructions of ice accumulation, satellite and aircraft readings of ice thickness, and changes in elevation and ice velocity to determine how fast ice shelves melt and compare the mass lost with the amount released by the calving, or splitting, of icebergs.
“The traditional view on Antarctic mass loss is it is almost entirely controlled by iceberg calving,” said Eric Rignot of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., and the University of California, Irvine. Rignot is lead author of the study to be published in the June 14 issue of the journal Science. “Our study shows melting from below by the ocean waters is larger, and this should change our perspective on the evolution of the ice sheet in a warming climate.”
Ice shelves grow through a combination of land ice flowing to the sea and snow accumulating on their surface. To determine how much ice and snowfall enters a specific ice shelf and how much makes it to an iceberg, where it may split off, the research team used a regional climate model for snow accumulation and combined the results with ice velocity data from satellites, ice shelf thickness measurements from NASA’s Operation IceBridge — a continuing aerial survey of Earth’s poles — and a new map of Antarctica’s bedrock. Using this information, Rignot and colleagues were able to deduce whether the ice shelf was losing mass through basal melting or gaining it through the basal freezing of seawater.
In some places, basal melt exceeds iceberg calving. In other places, the opposite is true. But in total, Antarctic ice shelves lost 2,921 trillion pounds (1,325 trillion kilograms) of ice per year in 2003 to 2008 through basal melt, while iceberg formation accounted for 2,400 trillion pounds (1,089 trillion kilograms) of mass loss each year.
Basal melt can have a greater impact on ocean circulation than glacier calving. Icebergs slowly release melt water as they drift away from the continent. But strong melting near deep grounding lines, where glaciers lose their grip on the seafloor and start floating as ice shelves, discharges large quantities of fresher, lighter water near the Antarctic coastline. This lower-density water does not mix and sink as readily as colder, saltier water, and may be changing the rate of bottom water renewal.
“Changes in basal melting are helping to change the properties of Antarctic bottom water, which is one component of the ocean’s overturning circulation,” said author Stan Jacobs, an oceanographer at Columbia University’s Lamont-Doherty Earth Observatory in Palisades, N.Y. “In some areas it also impacts ecosystems by driving coastal upwelling, which brings up micronutrients like iron that fuel persistent plankton blooms in the summer.”
The study found basal melting is distributed unevenly around the continent. The three giant ice shelves of Ross, Filchner and Ronne, which make up two-thirds of the total Antarctic ice shelf area, accounted for only 15 percent of basal melting. Meanwhile, fewer than a dozen small ice shelves floating on “warm” waters (seawater only a few degrees above the freezing point) produced half of the total melt water during the same period. The scientists detected a similar high rate of basal melting under six small ice shelves along East Antarctica, a region not as well known because of a scarcity of measurements.
The researchers also compared the rates at which the ice shelves are shedding ice to the speed at which the continent itself is losing mass and found that, on average, ice shelves lost mass twice as fast as the Antarctic ice sheet did during the study period.
“Ice shelf melt doesn’t necessarily mean an ice shelf is decaying; it can be compensated by the ice flow from the continent,” Rignot said. “But in a number of places around Antarctica, ice shelves are melting too fast, and a consequence of that is glaciers and the entire continent are changing as well.”
From NASA: http://www.nasa.gov/topics/earth/features/earth20130613.html
