Antarctic climate change – the exception that proves the rule?

Antarctica has been in the news recently because two large icebergs (one about 60 miles long and the other about 50) have broken off the continent. These “calving” events often occur naturally and these ones are probably not linked to climate change, although they might affect the global ocean circulation.

But I thought that this would be a good opportunity to have a look at the general climate situation in the South Pole region…

The clearest signal is rapid warming that has been seen on the Antarctic Peninsula (the bit that points up to South America) over the last 50 years.

The picture for the rest of the continent is not so clear, mainly because of the lack of data. For comparison, the USA has over 1000 climatological observing stations, some of which go back to the late 1800s; Antarctica currently has around 55 stations, very few of which go back to before 1957, (plus a similar number of automatic weather stations, which tend to not be maintained for long periods) and these data are used to represent a much bigger land area.

Antarctica compared to the USA[Image from NASA]

Nonetheless, there have been some high profile studies looking at Antarctic temperature trends, some finding cooling, some finding warming and nearly all being controversial.

So why is the warming on the Peninsula so clear?

The reason is that the warming is mostly driven by atmospheric circulation changes and not the increase in the greenhouse gas concentrations (although global climate change patterns forced by GHGs can include atmospheric circulation changes).

Ozone "hole"The key factor is that the ozone hole above the South Pole has changed the wind patterns – when ozone is removed from the stratosphere, less solar UV radiation is absorbed so the polar stratosphere cools. This increases the temperature change as you move away from the pole and, in turn, has changed the westerly (clockwise) winds that circle the pole – they are now further south and faster.

This wind pattern spreads down through the atmosphere towards the planet’s surface and has, therefore, brought more warm air from over the Southern Ocean to the Peninsula. This circulation change has less effect on the Antarctic interior and possibly even isolates it from the rest of the Earth system.

This climate change pattern is really interesting to study and we can even use ice core data from the Antarctic to look at how these winds have changed in the past – I’ve recently reviewed the literature on this subject (Russell and McGregor 2010).

Korhonen et al. (2010) have even found another mechanism of how these wind changes have affected the climate. As the wind speed over the ocean increases, it throws up more spray and this means that more clouds can form over the Southern Ocean and Antarctica (I’ll write a post later about how clouds form). If there are more, bright clouds around then these reflect away more incoming sunlight, which will cool the region beneath these clouds.

So, to bring all this together, if the Antarctic continent has been cooling (which isn’t clear) then this could be because the normal rules don’t apply to Antarctica. Does this mean that we can say that Antarctic climate change is the exception that proves the rule of GHG forced climate change?

Probably not, but it does highlight just how complicated the climate system is and how much more there is find out about it!

References:

ResearchBlogging.orgKorhonen, H., Carslaw, K., Forster, P., Mikkonen, S., Gordon, N., & Kokkola, H. (2010). Aerosol climate feedback due to decadal increases in Southern Hemisphere wind speeds Geophysical Research Letters, 37 (2) DOI: 10.1029/2009GL041320

ResearchBlogging.orgRussell, A., & McGregor, G. (2009). Southern hemisphere atmospheric circulation: impacts on Antarctic climate and reconstructions from Antarctic ice core data Climatic Change DOI: 10.1007/s10584-009-9673-4

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14 Responses to “Antarctic climate change – the exception that proves the rule?”

  1. Icebergs, Ice Hockey, and Other News « 350 or bust Says:

    [...] In response the icebergs breaking off the Antarctic ice sheet and floating towards Australia, Andy Russell’s weather-related blog examines the general climate situation in the South Pole region, with great pictures and links to peer-reviewed articles.  Check it out the posting, Antarctic Climate Change – The Exception That Proves the Rule? here. [...]

  2. JohnR Says:

    For a summary of the odd things going on with those temperature readings in Antarctica, see the following link. Plenty more in the WUWT Category “Antarctica” from early 2009. Rapid warming? Not so much.

    http://wattsupwiththat.com/2009/05/29/steig-et-al-falsified/

    • andyrussell Says:

      I used the term “rapid warming” in relation to the Antarctic Penisula – this is not disputed anywhere, not even in the post you link to! I agree that the climate of the continental interior is less clear (as I also said in my blog post) but are there any better criticisms of Steig et al. than WUWT?

  3. scienceofdoom Says:

    Thanks for an interesting post.

    Do you have any data, a graphic (or a link) of the change in stratospheric temperature profile as a result of the ozone hole. Or is it in one of those papers?

    • andyrussell Says:

      Most of the cooling occurs in Spring when the photochemistry that leads to the ozone depletion occurs. There’s a nice figure showing the temperature decline above various stations in this paper: Randel and Wu (1999) “Cooling of the Arctic and Antarctic Polar Stratospheres due to Ozone Depletion” Journal of Climate, 12, 1467-1479.

      Randal and Wu

      I still think that the atmospheric dynamics of the mechanism driving this stratosphere/troposphere coupling needs more work i this is something that I’m hoping to do in the future.

      • scienceofdoom Says:

        Thanks, I got the paper. Fig 15b has the profile I was interested in. I have only scanned the paper so far, it looks like they tied 15a (ozone change vs height) and 15b together but a pity they are different periods. Perhaps the best data that was available..

      • andyrussell Says:

        That paper’s been cited quite a lot so I suspect that there might be something more up to date.

  4. kriss Says:

    that info sux!!!!!!!!!!!

  5. kriss Says:

    i wanna no is climate change effecting antarctica!?!?!?!?!?!?!? u putt that info on the rong Qi sugest u delete it imidiatly

    • andyrussell Says:

      Part of the problem with assessing Antarctic climate change is that we don’t have a lot of data to work with. It also depends what we mean by “climate change”? The climate of the Peninsula is definately changing but it is not certain how much of that is do with greenhouse gas changes. Anyway, probably some interesting points that deserve a post on their own…

  6. My blogging review of 2010 « Our Clouded Hills Says:

    [...] Antarctic climate change – the exception that proves the rule? March 2010 10 comments 5 [...]

  7. diogenes Says:

    well at least you make no reference mto the comprehensively debunked Steig paper that got the people at Nature so fired up.

    • andyrussell Says:

      Not sure it was “comprehensively debunked” – O’Donnell described his work thus:

      “I would hope that our paper is not seen as a repudiation of Steig’s results, but rather as an improvement.”

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