How Global Warming Enhanced Glacial Melt to Expand Sea Ice in Antarctica

antarctica

Overall, worldwide sea ice totals have been declining over the past few decades. This trend has been led by a massive summer collapse of sea ice in the Arctic. But, on the other side of the world, in Antarctica, sea ice area and extent have been slowly expanding. This seeming contradiction recently spurred researchers to take a closer look at Antarctica to determine why sea ice would be expanding even though worldwide atmospheric and ocean temperatures are on the rise.

What they found was an amazing and complex combination of forces driving a moderate sea ice expansion in the southern hemisphere. Warmer waters coming into contact with submerged glaciers slowly melts the ice. In addition, a warming Antarctic continent disgorges large volumes of water each year. This fresh melt water, flushing into the ocean at a rate of 250 gigatons each year, then expands, covering the ocean surface in a thin layer surrounding Antarctica. Not only does this fresher water freeze at higher temperatures, it keeps warmer waters from rising up to melt the sea ice from below. The result is that sea ice is both insulated and made of fresher water. So until atmospheric and ocean temperatures rise enough to overwhelm this dynamic, Antarctic sea ice will remain protected by insulating processes coming from melting glaciers.

Warmer water trapped in the ocean depths surrounding Antarctica has also played a role in heating the world’s deep oceans. This heating was recently detected in a new study conducted by Kevin Trenberth and colleagues. The study found that a significant portion of the last decade’s heating had been sequestered in the deep ocean. Now it’s apparent that glacial melt in Antarctica may have played a role.

The Arctic sea ice, thus far, hasn’t benefited from a similar insulating process. The result was an 80 percent sea ice volume loss since 1979 and a high risk that sea ice will completely melt one summer between now and 2020. It’s possible that Greenland melt may continue to increase, freshening the Arctic’s waters, and providing a similar benefit at the cost of enhanced sea level rise and more extreme weather. But ocean currents, geography, and salinity dynamics for the Arctic are different from that of the Antarctic. So it is uncertain if melt will play as large a role in insulating northern hemisphere sea ice as it has in the southern hemisphere.

It is worth noting that rapid glacial melt, though it drives more extreme weather events even as it more rapidly increases sea level, tends to put a powerful damper on global temperature increases once glacial melt reaches the 1 meter mark. The heat energy goes more into melting the ice and less into warming the atmosphere and oceans. The negative feedback of fresher ocean waters in the polar regions as well as iceburgs floating in rapid glacial melt zones also has a net cooling effect. The result is that a degree or more of global temperature increases may be ‘held in check’ as the ice melts. Rapid ice melt decades may result in brief periods of relative cooling (where temperature increases back off from 1.5 or 2 degrees above average to around .9 to 1.3 degrees above average).

It’s a balancing effect and trade-off where you end up with more changes to the Earth’s environment and less overall heating in the short-term. This delayed heating effect of ice melt should not be seen as a good sign, however. As mentioned above, it comes at the severe cost of increased weather extremes and more rapid ocean level increases. In the end, once the messy transition decades are passed, a more liquid ocean results in more water vapor in the atmosphere, warmer Arctic and Antarctic environments that pump more greenhouse gasses into the atmosphere, receding glaciers and snow cover reducing the Earth’s reflectivity and adding further warming, and a warmer deep ocean resulting in more ocean methane release.

To get an idea how Greenland and Antarctic melt might dramatically impact world weather while putting a short-term dampening on global warming over the coming decades, take a look at this paper by James Hansen:

Update of Greenland Ice Sheet Mass Loss: Exponential?

It is worth noting that the scenarios examined in the paper come as a result of a relatively moderate increase in human greenhouse gas emissions: the A1B scenario. However, current emissions have increased more along the A1FI scenario which would likely result in even more climate volatility than the Hansen paper suggests.

The thing to take away from this new study is that both the Arctic sea ice collapse and the slower expansion of Antarctic sea ice are caused by the same forcing — human caused global warming — and that the glacial melt now resulting in localized cooling is also driving enhanced sea level rise and more extreme weather.

Please find more information on these new, ground-breaking studies here:

Global Warming Expands Antarctic Sea Ice

Oceans Continue to Warm, Especially in the Deeps

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7 Comments

  1. klem

     /  April 3, 2013

    Wait a minute, wasn’t it just last year climate alarmists were screaming that Antarctic ice was melting due to anthropogenic global warming? Now you’re saying this year the same anthropogenic global warming is causing Antarctic ice to grow. Oh come on now. Sorry pal, but either climate scientists were wrong last year or they are wrong this year, they can’t have it both ways. AGW can’t cause ice extent decreases one year and increases the next.

    You know, when mother nature shows climate models are wrong, someone has to stand up and admit it.

    This is exactly why climate change is a non issue with the public now.

    Keep up the great work. Lol!

    Reply
  2. Glacial melt on the Antarctic continent is increasing, currently contributing 250 billion tons of cold, fresh water to the ocean each year. This melt is caused by global warming. The cold, fresh water transferring to the ocean’s surface provides a negative feedback that temporarily enhances surface sea ice growth.

    Net global sea ice area and extent are falling. And, in the Arctic, we have the opposite effect — massive collapse of sea ice far out pacing Antarctic sea ice growth due to a local negative feedback.

    All of this is caused by human global warming. But, apparently, that’s a little too hard for you to understand?

    I know what you deniers will say once the big glaciers start melting, sea levels start rising, and we get a pause or slow-down in atmospheric warming. You’ll say that global warming doesn’t exist, despite the coastlines submerged and the major storms that will make Sandy look like a walk in the park.

    Read the science and learn something. Now there’s a novel suggestion.

    Reply
  3. klem

     /  April 4, 2013

    “Glacial melt on the Antarctic continent is increasing, currently contributing 250 billion tons of cold, fresh water to the ocean each year.”

    Um, 250 billion tons is about 250 cubic km of ice, sounds like alot. However Antarctica has 30 million cubic km of ice. It would still take 125,000 year to melt completely at that increased rate. Actually 250 cubic kms is roughly .0008% of the ice in Antarctica, it’s such a tiny amount I’m not sure it can be measured with confidence. I’ll bet it’s merely a guess.

    Just helping you out.

    cheers

    klem

    Reply
    • Sorry, Klem. You’re not helping, just confusing the issue.

      First, the paper and article were about natural feedbacks to Antarctic glacial melt at the rate of 250 billion tons per year (average) over the past decade. The result of that research showed a negative feedback that produced slowly expanding sea ice at the expense of glacial melt.

      The issue you bring up focuses on rate of melt, total sea level rise, and final melt date of all ice on Antarctica. These are separate issues entirely. So to address this issue you have to look at separate points.

      First, context. The current context involves CO2 in atmosphere and the rate at which we expect CO2 to increase over the next century. At current levels of CO2 (around 400 ppm) end melt resulted in a 15 to 75 foot rise in sea level with West Antarctica and Greenland mostly melting out. You see this by looking at paleoclimate during the recent geologic past 2-4 MY before present. So that’s the long term melt we have dialed in already if CO2 levels remain the same or inch higher.

      At 600 ppm CO2 long term melt results in all glacial ice disappearing. Reference paleoclimate 4-6 MY before present.

      Pace of sea level rise and pace of melt. Again, Context. And by examining Antarctic melt rates we find the pace of melt is not linear. In the 1980s Antarctica was gaining mass at the rate of 250 billion tons per year. The average loss for recent years is 250 billion tons per year. The average pace of melt increase is 14 gigatons per year. At that pace of melt+increase in melt rate, Antarctica loses enough ice to raise seas by 70 feet over 1000 years.

      And that’s just Antarctica. It doesn’t include Greenland, thermal water expansion, CAA or other land glaciers.

      Now let’s go back to current rate of sea level rise and what’s expected for end of century sea level rise. At the present pace of sea level rise (not accounting for the pace of melt increase), we get between 1 and three feet of sea level rise by the end of this century. The reason for the range is due to the fact that the past two years have seen sea level increase by 1 centimeter each year. However, taking into account the rate of glacial melt increase from Greenland, Antarctica, the CAA and land glaciers, we get to around 3-9 feet of sea level rise by the end of this century.

      Last of all, we should take a look at paleoclimate to determine what might be a proper range for sea level increase in the event of a powerful forcing. And what we find is that rates of sea level rise can meet or exceed 10 feet per century during drastic events.

      So there’s the context for the data you’ve cherry picked.

      Reply
      • klem

         /  April 25, 2013

        “At that pace of melt+increase in melt rate, Antarctica loses enough ice to raise seas by 70 feet over 1000 years.”

        The assumption here is that the rate will remain the same or increase. Some assumption there Rob, but even with your fear based compounding increase in melt rate, we still have a millennium. Wow, that’s quite a lot of time. Looks like we can put off cap&trade or building more of those fruity wind turbines for awhile yet. Thanks.

        “..taking into account the rate of glacial melt increase from Greenland, Antarctica, the CAA and land glaciers, we get to around 3-9 feet of sea level rise by the end of this century.”

        According to Wikipedia, sea level rise has averaged about 2 feet per century for the past 200 centuries, with periods of much slower rise as well as periods with faster sea level rise. For example, at one time sea level rose about 3.5 feet per century for about 9000 years straight. Therefore, your full blown 3-9 feet sea level rise by the end of this century seems to be well within normal variability, at least over the more recent geologic past.

        Thanks for this Rob.

        Just helping you clarify your context for the data I cherry picked.

        cheers

        Reply
        • 3 feet of sea level rise will put more than 50% of coastal cities in jeopardy of severe flooding. 9 feet is enough to take out most major cities.

          The problem with your laisser faire assessment is that, though we find comparable rates of sea level increase at the end of the last ice age, 3.5 billion people didn’t live in legacy infrastructure at or near the coastline as they do today.

          As for your cherry picked sea level rise data, it continues… Over the past 20 centuries sea level has been essentially flat. The exception being the 20th century, which saw a rise of about a foot, the most in more than 2000 years.

          Your flat averaging is a cherry pick because it doesn’t take into context the fact that since major civilization developed, sea level rise has been very slow or flat. Your ‘average rise of 2 feet’ is simply yet one more red herring in a long list, I’m sorry to say. Our context is not one of rising seas for much of human civilization. It is one of stable seas. And the rate of change will be between 3 and 9 times what we saw during the 20th century. Slower if we cut carbon emissions sooner, faster if we don’t.

          Stabilized CO2 at 600 ppm or more means no ice left, long term, and a rapid transition at a pace that makes coastal development mostly impossible during that period.

          I provide valid warning, which you continue to irrationally ignore. You, on the other hand, can’t even support your arguments without mangling the data…

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