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Tag Archive: Antarctica

  1. ‘Extreme’ Changes Underway in Some of Antarctica’s Biggest Glaciers

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    • The grounding line, where the glaciers become floating ice shelves, is receding as much as 600 feet per year, bolstering fears of a worst-case Antarctic meltdown scenario, with global sea level rising 10 feet by 2100.
    • Eight of the frozen continent’s 65 major ice streams had retreated by more than 410 feet per year—five times the average rate of retreat since the end of the last ice age. The grounding line of some of the glaciers emptying into the Amundsen Sea had retreated by up to 600 feet per year.
  2. Actions today will decide Antarctic ice sheet loss and sea level rise

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    • Each 5-year delay – a peak in 2025 instead of 2020, for example – most likely adds 20 cm of sea level rise by 2300, and could potentially add a full meter due to the uncertainty associated with the large ice sheets

    March 1 2018 by dana1981  read full SkepticalScience Post here

    A new study published in Nature looks at how much global sea level will continue to rise even if we manage to meet the Paris climate target of staying below 2°C hotter than pre-industrial temperatures. The issue is that sea levels keep rising for several hundred years after we stabilize temperatures, largely due to the continued melting of ice sheets in Antarctica and Greenland from the heat already in the climate system.

    The study considered two scenarios. In the first, human carbon pollution peaks somewhere between 2020 and 2035 and falls quickly thereafter, reaching zero between 2035 and 2055 and staying there. Global temperatures in the first scenario peak at and remain steady below 2°C. In the second scenario, we capture and sequester carbon to reach net negative emissions (more captured than emitted) between 2040 and 2060, resulting in falling global temperatures in the second half of the century….

    …The study also shows that it’s critical that our carbon pollution peaks soon. Each 5-year delay – a peak in 2025 instead of 2020, for example – most likely adds 20 cm of sea level rise by 2300, and could potentially add a full meter due to the uncertainty associated with the large ice sheets

    Another new study, published in the Proceedings of the National Academy of Sciences, found that sea level rise has been accelerating. If the rate of acceleration continues – which the lead author notes is a conservative estimate – we would see an additional 65 cm (close to a meter above pre-industrial sea level) of sea level rise by 2100.

    Yet another new study published in The Cryosphere using satellite data found that while the East Antarctic Ice Sheet has remained stable in recent years, ice loss from the West Antarctic Ice Sheet has accelerated….

    Matthias Mengel et al. Committed sea-level rise under the Paris Agreement and the legacy of delayed mitigation action Nature Communications volume 9, Article number: 601 (2018) doi:10.1038/s41467-018-02985-8

  3. Penguins track Antarctic changes

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    • Shifts in food webs and climate are written in penguin feathers and eggshells and revealed through an amino acid isotope technique.
    By Carolyn Gramling February 14, 2018 read full Science News post here

    Penguins preserve records of Antarctic environmental change. The birds’ feathers and eggshells contain the chemical fingerprints of variations in diet, food web structure and even climate, researchers reported February 12 at the American Geophysical Union’s 2018 Ocean Sciences Meeting.

    The Antarctic environment has changed dramatically in recent decades. Overfishing has led to a decline in krill, small swimming crustaceans that are a key food source for birds, whales, fish and penguins in the Southern Ocean. Climate change is altering wind directions, creating open water regions in the sea ice that become hot spots for life….

    …This study highlights the power of this amino acid isotope technique to track environmental change through animal tissues, says Seth Newsome, an animal ecologist at the University of New Mexico in Albuquerque who was not involved in the study. The technique is becoming popular because it can detect both diet and baseline changes in the food web from the same tissue, he says.

    “This 80-year record is just part of a much broader record of change,” McMahon said.

    K. McMahon, C. Michelson and M.J. Polito. Developing compound-specific stable isotope analysis of archival penguin tissues to reconstruct past Antarctic ecosystem responses to climate change and anthropogenic disturbance. American Geophysical Union Ocean Sciences meeting, Portland, Oregon, February 12, 2018.

  4. Ice Apocalypse – Rapid collapse of Antarctic glaciers could flood coastal cities by the end of this century.

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    • High tides would creep higher, slowly burying every shoreline on the planet, flooding coastal cities and creating hundreds of millions of climate refugees. All this could play out in a mere 20 to 50 years — much too quickly for humanity to adapt.
    • Six feet of sea level rise is more likely than three feet. But if carbon emissions continue to track on something resembling a worst-case scenario, the full 11 feet of ice locked in West Antarctica might be freed up, their study showed…
    • Another recent study indicates that Pine Island’s glaciers shattered in a relatively short amount of time at the end of the last ice age.
    • A fast transition away from fossil fuels in the next few decades could be enough to put off rapid sea-level rise for centuries. That’s a decision worth countless trillions of dollars and millions of lives.

    by Eric Hothaus November 21, 2017  Read full Grist article here

    ….Land-based ice, …when it falls into the ocean, it adds to the overall volume of liquid in the seas. Thus, sea-level rise. Antarctica is a giant landmass — about half the size of Africa — and the ice that covers it averages more than a mile thick. Before human burning of fossil fuels triggered global warming, the continent’s ice was in relative balance: The snows in the interior of the continent roughly matched the icebergs that broke away from glaciers at its edges.

    Now, as carbon dioxide traps more heat in the atmosphere and warms the planet, the scales have tipped.

    A wholesale collapse of Pine Island and Thwaites would set off a catastrophe. Giant icebergs would stream away from Antarctica like a parade of frozen soldiers. All over the world, high tides would creep higher, slowly burying every shoreline on the planet, flooding coastal cities and creating hundreds of millions of climate refugees.

    All this could play out in a mere 20 to 50 years — much too quickly for humanity to adapt.

    …A study they published last year was the first to incorporate the latest understanding of marine ice-cliff instability into a continent-scale model of Antarctica. Their results drove estimates for how high the seas could rise this century sharply higher. “Antarctic model raises prospect of unstoppable ice collapse,” read the headline in the scientific journal Nature, a publication not known for hyperbole.

    Instead of a three-foot increase in ocean levels by the end of the century, six feet was more likely, according to DeConto and Pollard’s findings. But if carbon emissions continue to track on something resembling a worst-case scenario, the full 11 feet of ice locked in West Antarctica might be freed up, their study showed….

    At six feet, though, around 12 million people in the United States would be displaced, and the world’s most vulnerable megacities, like Shanghai, Mumbai, and Ho Chi Minh City, could be wiped off the map.

    At 11 feet, land currently inhabited by hundreds of millions of people worldwide would wind up underwater. South Florida would be largely uninhabitable; floods on the scale of Hurricane Sandy would strike twice a month in New York and New Jersey, as the tug of the moon alone would be enough to send tidewaters into homes and buildings…

    In a new study out last month in the journal Nature, a team of scientists from Cambridge and Sweden point to evidence from thousands of scratches left by ancient icebergs on the ocean floor, indicating that Pine Island’s glaciers shattered in a relatively short amount of time at the end of the last ice age….

    …“Every revision to our understanding has said that ice sheets can change faster than we thought,” he says. “We didn’t predict that Pine Island was going to retreat, we didn’t predict that Larsen B was going to disintegrate. We tend to look at these things after they’ve happened.”

    There’s a recurring theme throughout these scientists’ findings in Antarctica: What we do now will determine how quickly Pine Island and Thwaites collapse. A fast transition away from fossil fuels in the next few decades could be enough to put off rapid sea-level rise for centuries. That’s a decision worth countless trillions of dollars and millions of lives. “The range of outcomes,” Bassis says, “is really going to depend on choices that people make.”

    Robert M. DeConto & David Pollard. Contribution of Antarctica to past and future sea-level rise. Nature 531, 591–597 (31 March 2016). doi:10.1038/nature17145

    Matthew G. Wise et al, Evidence of marine ice-cliff instability in Pine Island Bay from iceberg-keel plough marks, Nature (2017). DOI: 10.1038/nature24458
  5. Warm air helped make 2017 ozone hole smallest since 1988

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    • Scientists said the smaller ozone hole extent in 2016 and 2017 is due to natural variability and not a signal of rapid healing.

    November 2, 2017 NASA/Goddard Space Flight Center Read full ScienceDaily article here

    Measurements from satellites this year showed the hole in Earth’s ozone layer that forms over Antarctica each September was the smallest observed since 1988, scientists have announced…

    ….The ozone hole over Antarctica is expected to gradually become less severe as chlorofluorocarbons — chlorine-containing synthetic compounds once frequently used as refrigerants — continue to decline. Scientists expect the Antarctic ozone hole to recover back to 1980 levels around 2070.

    Ozone is a molecule composed of three oxygen atoms that occurs naturally in small amounts. In the stratosphere, roughly 7 to 25 miles above Earth’s surface, the ozone layer acts like sunscreen, shielding the planet from potentially harmful ultraviolet radiation that can cause skin cancer and cataracts, suppress immune systems and also damage plants. Closer to the ground, ozone can also be created by photochemical reactions between the sun and pollution from vehicle emissions and other sources, forming harmful smog.

    Although warmer-than-average stratospheric weather conditions have reduced ozone depletion during the past two years, the current ozone hole area is still large compared to the 1980s, when the depletion of the ozone layer above Antarctica was first detected. This is because levels of ozone-depleting substances like chlorine and bromine remain high enough to produce significant ozone loss.

  6. Intensifying winds could increase east Antarctica’s contribution to sea level rise

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    November 1, 2017 University of Texas at Austin read full ScienceDaily article here

    Totten Glacier, the largest glacier in East Antarctica, is being melted from below by warm water that reaches the ice when winds over the ocean are strong, according to research. The new findings are a cause for concern because the glacier holds more than 11 feet of sea level rise and acts as a plug that helps lock in the ice of the East Antarctic Ice Sheet.

    Chad A. Greene, Donald D. Blankenship, David E. Gwyther, Alessandro Silvano, Esmee van Wijk. Wind causes Totten Ice Shelf melt and acceleration. Science Advances, 2017; 3 (11): e1701681 DOI: 10.1126/sciadv.1701681

  7. The Antarctic ice shelf continues to crack

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    July 19 2017  read full Grist article here

    The new rift in Larsen C emerged days after a Delaware-sized iceberg broke off from the ice shelf.

    Scientists aren’t totally sure of the implications, but it seems the ice shelf isn’t quite done breaking apart yet.

    The same team of British scientists who announced last week’s birth of the humongous iceberg spotted the crack in high-resolution satellite data. The scientists noted the crack “may result in further ice shelf loss” in a blog post published Wednesday. The huge iceberg itself has already begun to break apart.

    Ice shelves are floating extensions of glaciers, so their breakup has virtually no effect on global sea levels. The worry is the new rift is heading in the general direction of the Bawden Ice Rise, which is “a crucial point of stabilization for Larsen C Ice Shelf,” according to the British team. A destabilized Larsen C could speed up the flow of its parent glaciers to the ocean, which would have a slight effect on sea levels.

  8. An Iceberg the Size of Delaware Just Broke Away From Antarctica

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    By JUGAL K. PATEL and JUSTIN GILLIS UPDATED July 12, 2017  Read full story here

    A chunk of floating ice that weighs more than a trillion metric tons broke away from the Antarctic Peninsula, producing one of the largest icebergs ever recorded and providing a glimpse of how the Antarctic ice sheet might ultimately start to fall apart.

    ….Larsen C, like two smaller ice shelves that collapsed before it, was holding back relatively little land ice, and it is not expected to contribute much to the rise of the sea. But in other parts of Antarctica, similar shelves are holding back enormous amounts of ice, and scientists fear that their future collapse could dump enough ice into the ocean to raise the sea level by many feet. How fast this could happen is unclear.

    In the late 20th century, the Antarctic Peninsula, which juts out from the main body of Antarctica and points toward South America, was one of the fastest-warming places in the world. That warming had slowed or perhaps reversed slightly in the 21st century, but scientists believe the ice is still catching up to the higher temperatures….

    The one trillion ton iceberg: Larsen C Ice Shelf rift finally breaks through

    Posted: 12 Jul 2017 08:05 AM PDT  ScienceDaily

    A one trillion tonne iceberg — one of the biggest ever recorded — has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice finally completed its path through the ice…. Whilst this new iceberg will not immediately raise sea levels, if the shelf loses much more of its area, it could result in glaciers that flow off the land behind speeding up their passage towards the ocean. This non-floating ice would have an eventual impact on sea levels, but only at a very modest rate.

  9. Scientists stunned by Antarctic rainfall and a melt area bigger than Texas

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    • An area of West Antarctica more than twice the size of California partially melted in 2016 when warm winds forced by an especially strong El Nino blew over the continent.
    • Harbinger of future in Antarctica?

    Chris Mooney Washington Post  June 15 2017  see full article here

    ….In the Antarctic summer of 2016, the surface of the Ross Ice Shelf, the largest floating ice platform on Earth, developed a sheet of meltwater that lasted for as long as 15 days in some places. The total area affected by melt was 300,000 square miles, or larger than the state of Texas, the scientists report.

    That’s bad news because surface melting could work hand in hand with an already documented trend of ocean-driven melting to compromise West Antarctica, which contains over 10 feet of potential sea level rise.

    “It provides us with a possible glimpse of the future,” said David Bromwich, an Antarctic expert at Ohio State University and one of the study’s authors. The paper appeared in Nature Communications.

    “You probably have read these analyses of West Antarctica, many people think it’s slowly disintegrating right now, and it’s mostly thought to be from the warm water eating away at the bottom of critical ice shelves,” Bromwich continued. “Well, that’s today. In the future, we could see action at the surface of these ice shelves as well from surface melting. So that makes them potentially much more unstable.”…

    From ScienceDaily: Widespread snowmelt in West Antarctica during unusually warm summer Posted: 15 Jun 2017 05:46 AM PDT

    Julien P. Nicolas et al January 2016 extensive summer melt in West Antarctica favoured by strong El Niño Nature Communications 8, Article number: 15799 (2017) doi:10.1038/ncomms15799

    Abstract: Over the past two decades the primary driver of mass loss from the West Antarctic Ice Sheet (WAIS) has been warm ocean water underneath coastal ice shelves, not a warmer atmosphere. Yet, surface melt occurs sporadically over low-lying areas of the WAIS and is not fully understood. Here we report on an episode of extensive and prolonged surface melting observed in the Ross Sea sector of the WAIS in January 2016. A comprehensive cloud and radiation experiment at the WAIS ice divide, downwind of the melt region, provided detailed insight into the physical processes at play during the event. The unusual extent and duration of the melting are linked to strong and sustained advection of warm marine air toward the area, likely favoured by the concurrent strong El Niño event. The increase in the number of extreme El Niño events projected for the twenty-first century could expose the WAIS to more frequent major melt events.

  10. Antarctica- miles of ice collapsing into sea

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    Antarctic Dispatches is a three-part series from the seventh continent. Written by Justin Gillis. We went to Antarctica to understand how changes to its vast ice sheet might affect the world. New York Times.

    Because the collapse of vulnerable parts of the ice sheet could raise the sea level dramatically, the continued existence of the world’s great coastal cities — Miami, New York, Shanghai and many more — is tied to Antarctica’s fate….

    Remote as Antarctica may seem, every person in the world who gets into a car, eats a steak or boards an airplane is contributing to the emissions that put the frozen continent at risk. If those emissions continue unchecked and the world is allowed to heat up enough, scientists have no doubt that large parts of Antarctica will melt into the sea.

    But they do not know exactly what the trigger temperature might be, or whether the recent acceleration of the ice means that Earth has already reached it. The question confronting society, said Richard B. Alley, a climate scientist at Pennsylvania State University, is easier to ask than to answer: “How hot is too hot?”…

    Looming Floods, Cities Threatened Part 2 May 19, 2017

    [Note: California’s coast and cities are tied to Antarctica’s fate as well.  See post with summary here and for a full pdf of the new California report see: Rising Seas in California.]

    The risk is clear: Antarctica’s collapse has the potential to inundate coastal cities across the globe.

    Over tens of millions of years, thin layers of snow falling on the continent — in many places, just a light dusting every year — were pressed into ice, burying mountain ranges and building an ice sheet more than two miles thick. Under its own weight, that ice flows downhill in slow-moving streams that eventually drop icebergs into the sea.

    If that ice sheet were to disintegrate, it could raise the level of the sea by more than 160 feet — a potential apocalypse, depending on exactly how fast it happened. Recent research suggests that if society burns all the fossil fuels known to exist, the collapse of the ice sheet will become inevitable.

    Improbable as such a large rise might sound, something similar may have already happened, and recently enough that it is still lodged in collective memory.

    In the 19th century, ethnographers realized that virtually every old civilization had some kind of flood myth in its literature.

    In the Epic of Gilgamesh, waters so overwhelm the mortals that the gods grow frightened, too. In India’s version, Lord Vishnu warns a man to take refuge in a boat, carrying seeds. In the Bible, God orders Noah to carry two of every living creature on his ark.

    “I don’t think the biblical deluge is just a fairy tale,” said Terence J. Hughes, a retired University of Maine glaciologist living in South Dakota. “I think some kind of major flood happened all over the world, and it left an indelible imprint on the collective memory of mankind that got preserved in these stories.”