Exceptional 2012 Greenland Ice Melt Caused By Jet Stream Changes That May Be Driven By Global Warming

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"Exceptional 2012 Greenland Ice Melt Caused By Jet Stream Changes That May Be Driven By Global Warming"

New research finds that “unusual changes in atmospheric jet stream circulation caused the exceptional surface melt of the Greenland Ice Sheet (GrIS) in summer 2012.”
Prof. Jennifer Francis tells me these changes are consistent with those caused by warming-driven “Arctic Amplification.” And that means GrIS may melt faster than climate models have projected.

Extent of surface melt over Greenland’s ice sheet on July 8, 2012 (left) and July 12, 2012. In just a few days, the melting had dramatically accelerated and an estimated 97 percent of the ice sheet surface had thawed. Credit: NASA.

Back in May, a study found that by 2025, there is a “50-50 chance” of this unprecedented ice melt happening annually simply based on the continued rapid warming of GrIS.

This new study, “Atmospheric and oceanic climate forcing of the exceptional Greenland ice sheet surface melt in summer 2012,” suggests this kind of melt may become commonplace even sooner.

As the news release explains, an international team used a computer model and satellite data “to confirm a record surface melting of the GrIS for at least the last 50 years – when on 11 July 2012, more than 90 percent of the ice-sheet surface melted. This far exceeded the previous surface melt extent record of 52 percent in 2010.” Weather station data “showed that several new high Greenland temperature records were set in summer 2012.”

The research “clearly demonstrates that the record surface melting of the GrIS was mainly caused by highly unusual atmospheric circulation and jet stream changes, which were also responsible for last summer’s unusually wet weather in England.”

What were these changes? Professor Edward Hanna from the University of Sheffield’s Department of Geography explains:

“The GrIS is a highly sensitive indicator of regional and global climate change, and has been undergoing rapid warming and mass loss during the last 5-20 years. Much attention has been given to the NASA announcement of record surface melting of the GrIS in mid-July 2012. This event was unprecedented in the satellite record of observations dating back to the 1970s and probably unlikely to have occurred previously for well over a century.

“Our research found that a ‘heat dome’ of warm southerly winds over the ice sheet led to widespread surface melting. These jet stream changes over Greenland do not seem to be well captured in the latest Intergovernmental Panel on Climate Change (IPCC) computer model predictions of climate change, and this may indicate a deficiency in these models. According to our current understanding, the unusual atmospheric circulation and consequent warm conditions of summer 2012 do not appear to be climatically representative of future ‘average’ summers predicted later this century.

“Taken together, our present results strongly suggest that the main forcing of the extreme GrIS surface melt in July 2012 was atmospheric, linked with changes in the summer North Atlantic Oscillation (NAO), Greenland Blocking Index (GBI, a high pressure system centred over Greenland) and polar jet stream which favoured southerly warm air advection along the western coast.

“The next five-10 years will reveal whether or not 2012 was a rare event resulting from the natural variability of the NAO or part of an emerging pattern of new extreme high melt years. Because such atmospheric, and resulting GrIS surface climate, changes are not well projected by the current generation of global climate models, it is currently very hard to predict future changes in Greenland climate. Yet it is crucial to understand such changes much better if we are to have any hope of reliably predicting future changes in GrIS mass balance, which is likely to be a dominant contributor to global sea-level change over the next 100-1000 years.”

These changes in the jet stream and blocking patterns sounded quite similar to the findings of Francis, NOAA, and others. While the news release says, “The analysis shows that ocean temperatures and Arctic sea-ice cover were relatively unimportant factors in causing the extra Greenland melt,” I asked Dr. Francis if in fact these findings were consistent with her work.

She replied:

Hanna’s findings seem very consistent with the research I’ve been involved with, particularly our observations of an increasing tendency for ridging in the north Atlantic during summer. While I agree with him that sea ice loss per se may not be the primary driver of this behavior, I think it’s likely that Arctic Amplification (AA) IS playing an important role.

Sea ice loss is only one factor driving AA. In spring and summer, the AA appears to be caused mainly by 2 other factors: 1) the decline of snow cover on high-latitude land areas creates an albedo feedback similar to sea ice but is instead involves the earlier drying and heating of the soil under the snow, which promotes an earlier warm season on the continents and contributes to enhanced Arctic warming, and 2) increasing water vapor transport into the Arctic.

As you know, water vapor is a powerful greenhouse gas, it releases heat into the atmosphere when it condenses into clouds, and extra water vapor promotes additional clouds, which are also effective trappers of heat below them. The water vapor effect may be the most important for the summer ridging over Greenland, as it causes warming through a deeper layer of the atmosphere than the snow/ice effects (see Alexeev et al, Climate Dynamics, 2005; Porter et al, JGR, 2012), and thus has a more direct impact on weakening the poleward temperature gradient and consequently the jet-stream zonal winds. There was also a recent study by Von Walden and coworkers showing that cirrus clouds also caused additional surface warming over Greenland last summer, and these are just the type of clouds you’d expect to see under an upper-level ridge of high pressure.

If this ridging pattern continues to be as persistent as it has been since 2007 (see Hanna et al, 2012), then it could be that the climate models are underestimating the amount of surface melt from the Greenland ice sheet.

It would seem that warming-driven nonlinear effects are starting to dominate Greenland ice melt. It may be time to redo projections of sea level rise once again.

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32 Responses to Exceptional 2012 Greenland Ice Melt Caused By Jet Stream Changes That May Be Driven By Global Warming

  1. Paul Klinkman says:

    The second part of this story needs to be told.

    Any ice melt changes the albedo of the ice. A surface of new snow is reflects sunlight back into space. A surface of ice crystals passes the light deep into the ice, where it is converted to heat and where further melt is likely.

    Then comes part three of the story. The meltwater flows down into cracks in the ice, where it re-freezes and where it expands. Think of a bottle of water left in the freezer. The ice expands with tremendous force and the bottle explodes apart. That’s what happens to an ice sheet after a million years of not melting. The sheet builds up pressure until it’s close to popping, then it explodes apart in an hour or so. If the ice sheet in question is the Pine Island glacier or the Wilkins Ice Shelf, then parts of it drift away into the ocean.

    • prokaryotes says:

      Well this here is sea ice and when the WAIS ice cracks up, outflow depends on buttrassing. Though there are some canyons under WAIS…

      And jet stream changes, which were also responsible for blocking Hurricane Sandy’s path, creating a 90 degree change – leading directly into the New Jersey coast.

      • prokaryotes says:

        To clarify, i mean Greenland ice and WAIS … though the Jet Stream is altered as well – and i agree with Jennifer Francis, that you have to account for the sum of forcings, hence arctic amplification.

  2. rollin says:

    How is it progressing this year?

  3. Superman1 says:

    This is one of many recent data points that will show us the real meaning of nonlinear dynamical systems with cross-coupled synergistic positive feedback mechanisms. Mother Nature is unleashing a full-spectrum offensive on land-sea-air; there will be no respite, and there will be no refuge. The end will be violent, and sooner than anyone here is estimating.

    • Joan Savage says:

      “..sooner than anyone here is estimating.”

      I suggest that you retract the “anyone here” level of generality, given insufficient evidence.

      In the CP archives, you could find numerous posts and comments about mass extinction, accelerated rate of climate change, positive feedbacks, “black swans” of risk analysis, and other similarly useful topics.

      We aren’t always raging out loud, but that doesn’t mean we don’t know the risks. Consider that in an emergency room, the ER staff’s calm is usually a sign of their professionalism, not ignorance.

      That said, on one occasion I took an elderly friend to a less-than-alert ER intake, who seemed to think that she was just another person wanting treatment for the flu. I had to push to get them to take vital signs, rather than leave her sitting. Once they saw 67/25 BP, they sped up, rather impressively, and did save her life.

      I see similar vital signs in climate change, that if understood, should galvanize an organized response.

      • Mulga Mumblebrain says:

        If you take away Generalissimo Superman’s generalisations, then, generally, he has not much to say- and he repeats it generously.

  4. prokaryotes says:

    I guess fresh water influx also does contribute significantly to the AA phenomena, since it alters the currents in the northern polar region.

  5. The phenomenon that Paul K describes would be more or less instantaneous. Another sign that something truly dreadful and irreversible may be about to happen far sooner than almost anyone expects.

    • prokaryotes says:

      And we are still collectively sleep walking into this disaster.

      Once the disaster hit, the turmoil unleashed will make climate action even harder to accomplish, we are not very smart when it comes to response.

      • Superman1 says:

        The ‘device’ has already detonated; in the climate change case, it takes thirty years before the shock wave is felt, rather than thirty seconds.

  6. Joan Savage says:

    Nature magazine review of a report in Geophysical Research Letters

    Polar wander linked to climate change
    Melting ice in Greenland may have helped to shift the location of the North Pole.

    “GRACE’s twin probes measure changes in Earth’s gravity field, which can be used to track shifts in the distribution of water and ice. Chen’s team used GRACE data to model how melting ice caps affect Earth’s mass distribution. They found that recent accelerated ice loss and associated sea-level rise accounted for more than 90% of the post-2005 polar shift.”

    http://www.nature.com/news/polar-wander-linked-to-climate-change-1.12994#/b1

    Link to original Chen et al article in GRL:
    http://onlinelibrary.wiley.com/doi/10.1002/grl.50552/abstract

    • Joan Savage says:

      From the Nature article:
      …in 2005, the pole changed course and began galloping east towards Greenland at a rate of more than 7 milliarcseconds per year.

      Erik Ivins, a geophysicist at NASA’s Jet Propulsion Laboratory in Pasadena, California:

      When mass is lost in one part of a spinning sphere, its spin axis will tilt directly towards the position of the loss, he says — exactly as Chen’s team observed for Greenland. “It’s a unique indicator of the point where the mass is lost,” says Ivins.

    • Joan Savage says:

      A threshold for cumulative GrIL icemelt in 2005 could be what is correlated to the more rapid pole shift, otherwise 2005 was not itself a particularly distinctive year for melt rate.

      2005 data:
      http://cires.colorado.edu/science/groups/steffen/greenland/melt2005/

    • prokaryotes says:

      The latest science suggests that past abrupt Greenland warming (so called DO events) may be triggered by the Jet Stream – induced from what we call arctic amplification.

    • Joan Savage says:

      Your review focused on Dansgaard Oeschger events, so I see where you are looking at the Arctic / Jet Stream anthropogenic forcing as that might affect D-O periodicity.

      Perhaps the UK Met Office meeting can shed other light on the topic, as they are including examination of the possible role of the Atlantic Meridional Overturning Circulation in the miserable British weather last year.

      See how it all comes together.

  7. Paul Magnus says:

    Wow we’ve unleash the dragon!

  8. Stephen W says:

    ” … the record surface melting of the GrIS was mainly caused by highly unusual atmospheric circulation and jet stream changes, which were also responsible for last summer’s unusually wet weather in England.”

    And maybe it has a hand in what feels like an almost never ending string of overcast & dull days here in the UK in 2013 since about February. We have had a few days of blue skies and sunny intervals but it’s become a running joke with my partner when we wake up, look out of the window and groan that “it looks like another grey blanket day”.

    Looks like someone’s noticed (if you can get it outside the UK): http://www.bbc.co.uk/news/science-environment-22948138

  9. Mauri Pelto says:

    Imagery from yesterday indicates impact of recent warm summers on NE Greeland glaciers. Zachariae and 79 Glacier

  10. John McCormick says:

    The Jet Stream: Global Warming’s smoking gun

    “Our research found that a ‘heat dome’ of warm southerly winds over the ice sheet led to widespread surface melting. These jet stream changes over Greenland do not seem to be well captured in the latest Intergovernmental Panel on Climate Change (IPCC) computer model predictions of climate change, and this may indicate a deficiency in these models.”

    Reminds me of the joke: The forensics team reported the victim’s cause of death was a bullet in the left frontal lobe. How the bullet got there has yet to be determined. Further investigation is underway.

    The erratic jet stream is our future and likely the determinant of civilization’s capability to survive global warming.

  11. Colorado Bob says:

    Accuweather has a classic jet stream map of this very phenomena

    Alaskan Temperatures Soar to the 90s, Challenge Records

    http://www.accuweather.com/en/weather-news/heat-turns-up-in-alaska-1/14371788

    • Colorado Bob says:

      Baked Alaska: All-Time Record Heat Grips State

      http://www.weather.com/safety/heat/baked-alaska-record-heat-20130618

      Talkeetna, 75 miles north of Anchorage, reached 96 degrees. Just a day earlier, it had tied its all-time record high of 91, also set June 14, 1969 and June 26, 1953. The 96-degree high was hotter than any town in the entire state of Florida on Monday.

      * McGrath hit 94 degrees, crushing its all-time record of 90 set June 15, 1969 and just tied on Sunday. McGrath is deep in the interior of southwest Alaska, 215 miles northwest of Anchorage.

      * Cordova hit 90 degrees, breaking its record of 89 set July 16, 1995. Cordova is on the coast 145 miles east of Anchorage.

      * Valdez touched 90 degrees as well, erasing its record of 87 set June 25-26, 1953. Valdez is on an arm of Prince William Sound, 120 miles east of Anchorage.

      * Seward hit 88 degrees, eclipsing its all-time high of 87 set July 4, 1999. Seward is on the coast of the Kenai Peninsula, 80 miles south of Anchorage.

      • Colorado Bob says:

        The thermometer at the Statoil station in Karasjok in Finnmark read 34 degrees on Saturday (93F), fully 80 degrees higher than on the coldest day last winter, reported newspaper Aftenposten.

        http://www.newsinenglish.no/2013/06/03/sudden-heat-wave-shocked-karasjok/

        • Colorado Bob says:

          Three events in 11 months where 90F degree temps spend 3-4 days in the far north. If one of these sets up for 7-10 days at a time, There will be flash melting everything under it.

      • Mulga Mumblebrain says:

        Rather large and ominous jumps. The discontinuity seems to be occurring very rapidly and at a sobering scale, and still no action is even in sight. Surpassing strange.

  12. SecularAnimist says:

    Superman1 posted the following on June 17, 2013 at 7:28 pm:

    “… the real meaning of nonlinear dynamical systems with cross-coupled synergistic positive feedback mechanisms. Mother Nature is unleashing a full-spectrum offensive on land-sea-air; there will be no respite, and there will be no refuge. The end will be violent, and sooner than anyone here is estimating.”

    You posted this EXACT SAME VERBATIM TEXT on the comment page for “Daddy, Could We Have Our Planet Back Now” on June 16, 2013 at 6:42 PM.

    You have now officially descended from troll to spammer.

    • Mulga Mumblebrain says:

      Perhaps he’s part of a sister program to PRISM, designed to sow confusion. SPASM, perhaps. Superman’s Perennially Annoying Solipsistic Messages, Inc.

  13. Paul Magnus says:

    “or part of an emerging pattern of new extreme high melt years.”

    err, I think it certainly is already part of a more general pattern which Hansen points out in his paper on extreme weather.