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Tag Archive: ice

  1. 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.

  2. 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.

  3. Black carbon persists in snow and ice globally; distant forest fires deposit soot thousands of miles away, accelerating melt

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    • The influence of distant forest fires on melt events on the Greenland ice sheet shown from chemical analyses
    • researchers used molecular analysis of the black carbon along with analysis of wind patterns to show that Greenland’s ice sheet had recently seen clear effects of wildfires burning thousands of miles away in the Canadian Arctic
    • black carbon accelerates ice melt

    Black carbon varies, but stubbornly persists, in snow and ice around the world

    Posted: 30 Jun 2017 11:07 AM PDT

    A new study comparing dissolved black carbon deposition on ice and snow in ecosystems around the world (including Antarctica, the Arctic, and alpine regions of the Himalayas, Rockies, Andes, and Alps) shows that while concentrations vary widely, significant amounts can persist in both pristine and non-pristine areas of snow.

    ….Black carbon is the soot-like byproduct of wildfires and fossil fuel consumption, able to be carried long distances via atmospheric transport. Because these black particles absorb more heat than white snow, the study of black carbon concentrations in glaciers is important for predicting future melt rates….

    While the exact sources of black carbon are often difficult to pinpoint in remote areas, the researchers used molecular analysis of the black carbon along with analysis of wind patterns to show that Greenland’s ice sheet had recently seen clear effects of wildfires burning thousands of miles away in the Canadian Arctic. “We could tell that the carbon was fresh from these fires…”

    …Wildfires are anticipated to increase in future years, a trend that could compound the effects of longer summer melt seasons and allow for more black carbon deposition. “More black carbon exposure on the ice could continue to drive a feedback loop of further melt,” ….”The influence of distant forest fires on melt events on the Greenland ice sheet is inherently challenging to demonstrate and these clear chemical results provide another line of evidence for this connection…

    lia L. Khan, Sasha Wagner, Rudolf Jaffe, Peng Xian, Mark Williams, Richard Armstrong, Diane McKnight. Dissolved black carbon in the global cryosphere: Concentrations and chemical signatures. Geophysical Research Letters, 2017; DOI: 10.1002/2017GL073485

  4. Larsen C Iceberg on Brink of Breaking Off

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    By Brian Kahn Published: May 31st, 2017  full ClimateCentral article here

    …the Larsen C crack is… in the final days of cutting off a piece of ice that will be one of the largest icebergs ever recorded….The crack has spread 17 miles over the past six days, marking the biggest leap since January.

    …The vast majority of ice shelves are losing volume due to rising ocean and air temperatures. That’s helped prime parts of West Antarctica for what might be unstoppable melt that could raise sea levels at least 10 feet. Researchers also recently found meltwater ponds are much more common than previously thought. They even discovered a roaring seasonal waterfall on the Nansen Ice Shelf.

    These and other findings make clear that the Larsen C crack is just one of many changes happening to Antarctica. Global warming has pushed temperatures up to 5°F higher in the region since the 1950s and they could increase up to 7°F further by the end of the century, putting more stress on ice…

  5. 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.”

  6. Arctic meltdown propels globe to second-warmest April on record

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    • Arctic sea ice tied for lowest in April 2017 even without El Nino
    • Arctic warming 2x faster than global average

    by Andrew Freedman Mashable May 16 2017 full article here

    Continued freak warmth in the Arctic helped propel global average temperatures to the second-warmest level on record for the month of April, NASA reported on Monday.

    The new findings illustrate how the planet is still setting climate milestones even in the absence of other factors that tend to elevate global air and sea temperatures, such as an El Niño event.

    This makes clear the growing influence of human-caused global warming on the planet’s climate, month after month, year after year, as the amounts of planet-warming greenhouse gases in the atmosphere continue to rise to levels unseen during all of human history. …The top 3 hottest months of April to occur since instrument records began in 1880 have all taken place since 2010.

    …For April of 2017, the story is dominated by unusual warmth in parts of the Arctic, including across Siberia, parts of China, Alaska and the northwest portions of the Arctic Ocean. Greenland, however, had below average temperatures for the month, though that weather pattern reversed itself in early May.

    Arctic warming (red) compared to the global average (black).

    Arctic sea ice tied for for the lowest level on record during the month of April, after setting record lows throughout the fall and winter. The sea ice cover, which has been declining since satellites first began keeping tabs on it in 1979, is now far thinner and younger than average as it enters the summer melt season. (Older, thicker ice has a higher chance of surviving the summer melt.) …

     

  7. Climate Change Altering the Arctic Faster Than Expected

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    By Brian Kahn Published: April 25th, 2017 full article here

    Evidence continues to mount that climate change has pushed the Arctic into a new state. Skyrocketing temperatures are altering the essence of the region, melting ice on land and sea, driving more intense wildfires, altering ocean circulation and dissolving permafrost.

    A new report chronicles all these changes and warns that even if the world manages to keep global warming below the targeted 2°C threshold, some of the shifts could be permanent. Among the most harrowing are the disappearance of sea ice by the 2030s and more land ice melt than previously thought, pushing seas to more extreme heights.

    The findings, released Monday in the Snow, Water, Ice and Permafrost in the Arctic (SWIPA) assessment, come after a winter of extreme discontent for the region. Sea ice receded a bit in November, a rare occurrence, and hit a record-low maximum for the third year in a row. Temperatures averaged 11°F above normal, driven by sustained mild weather that was punctured by periods of almost unheard of heat when temperatures reached up to 50°F above normal.

    This past winter is just the latest in a string of bizarre years and the report, authored by 90 Arctic experts, is the latest in a long line of increasingly dire warnings for the fastest-warming region on the planet. If carbon pollution isn’t slowed, parts of the Arctic could warm a whopping 16°F by the 2050s….

    The new analysis shows that the average number of days with sea ice cover has dropped by 10-20 days per decade since 1979….

    The massive rush of freshwater into the Arctic Ocean is also reshaping ocean circulation and the ecology of the region. Researchers have seen a marked slowdown in North Atlantic circulation as cold, fresh water off Greenland’s southern tip has acted as a roadblock to the currents that steer water through the region. That has the potential to mess with ocean circulation as well as weather patterns, particularly in Europe.

    The changes in the Arctic are a harbinger of what’s in store for the planet if we continue to emit carbon pollution. Some of these changes are likely irreversible. But the report does note that if the world sticks to its goal in the Paris Agreement, the region could reach an equilibrium that while different from its present state, is still less radical than the fate it faces if we keep going down the current carbon path.

  8. Greenland’s Coastal Ice Passed Climate Tipping Point 20 Years Ago, Melting 3x Faster, Study Says

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    • Faster-than-expected melting of Greenland’s ice fields is worrisome news for … sea level rise.

    Ice caps and glaciers along the coast of Greenland passed a tipping point in 1997, when a layer of snow that once absorbed summer meltwater became fully saturated. Since then, the coastal ice fields—separate from the main Greenland Ice Sheet—have been melting three times faster than they had been, according to a new study published Friday in the journal Nature Communications.

    “The melting ice caps are an alarm signal for the ice sheet. It means long-term ice mass loss is inevitable. It will increase and accelerate if nothing changes,” said lead author Brice Noël, a scientist at the  University of Utrecht Institute for Marine and Atmospheric Research. “It’s very unlikely the ice caps will recover. It’s a climate tipping point—the time at which a change or an effect cannot be stopped.

    Climate scientists are wary of tipping points, when a series of small changes make a much larger change inevitable. The fear is a total meltdown of the Greenland Ice Sheet, which would raise global sea level by 24 feet, Noël said. Overall, the rate of ice sheet melting is accelerating, according to peer-reviewed studies cited in the most recent Arctic report from NOAA.

    On a warming planet, there will be less snow and more rain. That will limit the formation of healthy snow that could absorb the runoff in summer. Additional melt will just run off toward the ocean, raising sea level,” he said. “What we saw there in normal conditions, before 1997, is that the snow was able to absorb most of the melt and then refreeze. So the melting was not contributing to sea level rise before 1997, even though warming was already ongoing.

    The new study, which included scientists from the Netherlands, Switzerland, Norway, Denmark and the United States, focused on coastal ice caps and glaciers at 12 locations around Greenland, tracking the melt-freeze cycle from 1958 to 2015. The sites represent a total of 38,000 square miles of ice, a little larger than Indiana….

    B. Noël et al A tipping point in refreezing accelerates mass loss of Greenland’s glaciers and ice caps Nature Communications 8, Article number: 14730 (2017) doi:10.1038/ncomms14730

     

  9. Arctic ice melt could trigger uncontrollable climate change at global level

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    Scientists warn increasingly rapid melting could trigger polar ‘tipping points’ with catastrophic consequences felt as far away as the Indian Ocean

    Arctic scientists have warned that the increasingly rapid melting of the ice cap risks triggering 19 “tipping points” in the region that could have catastrophic consequences around the globe.

    The Arctic Resilience Report found that the effects of Arctic warming could be felt as far away as the Indian Ocean, in a stark warning that changes in the region could cause uncontrollable climate change at a global level.

    Temperatures in the Arctic are currently about 20C above what would be expected for the time of year, which scientists describe as “off the charts”. Sea ice is at the lowest extent ever recorded for the time of year.

    “The warning signals are getting louder,” said Marcus Carson of the Stockholm Environment Institute and one of the lead authors of the report. “[These developments] also make the potential for triggering [tipping points] and feedback loops much larger.”

    arctic

    Climate tipping points occur when a natural system, such as the polar ice cap, undergoes sudden or overwhelming change that has a profound effect on surrounding ecosystems, often irreversible….