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Author Topic: Warm Continents Cold Arctic. Negative Feedback? (sometimes)  (Read 1244 times)

Michael Hauber

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The current Arctic cyclone has been quite intense.  968 vs 963 for the GAC.  Looking at Canadian Analysis charts it covers only a fraction of the Arctic basin, compared to GAC covering the majority.  However the squeeze against the high pressure towards the Siberia Sea looks to have produced tighter wind gradients and presumably stronger maximum winds than the GAC, but over a relatively small area.

What struck me with this cyclone is the intensity of the associated warm air mass over Siberia.  After the central Arctic has generally been a little on the cooler side (compared to recent years, but still warm compared to longer term stats).  Temperature contrast plays a big role in cyclogenesis.  And while much has been said about Arctic amplification, and warm arctic cold continents, I think the situation may be reversed in summer.  During summer, particularly early summer the Arctic is still dominated by ice. This pins the surface air temperature close to 0 and the basin is pretty similar to what it was several decades ago.  The surrounding regions are getting warmer, thus we have warm continents, cold Arctic, and increasing frequency/intensity of Arctic cyclones.

And some seasons we see a transition from strong high pressure dominated weather early in the melting season to low pressure dominated weather.  2010 and 2011 really stood out as seasons that early on had severe melting weather, with some dramatic (at the time) early season stats, but then fell flat quite significantly as cyclone dominated weather took hold.  2013 was the year of the persistent arctic cyclone where the cyclones started early and just kept going.  While the surface temperature may be pinned close to 0, the atmosphere above has been getting warmer (eg 925hp temps).  But when we get a significant cyclone, mixing of the air column with the surface pinned at 0, plus clouds etc result in the relatively cool surface extending through a more significant portion of the atmosphere, thus increasing the warm continent cold arctic temperature contrast and making further cyclones more likely.

So negative feedback.  But perhaps only sometimes.  In 2012 we saw both early season cyclones that failed to establish a more persistent cyclone shield, but spread the ice and allowed intermittent high pressure weather to pump lots of heat into the mix of ice and open ocean, and then the very severe GAC.  The GAC was of course followed by massive loss of ice, although there is an argument that the ice had already been set up to melt by previous conditions and the GAC played a relatively minor role.
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bbr2314

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Re: Warm Continents Cold Arctic. Negative Feedback? (sometimes)
« Reply #1 on: July 12, 2018, 12:35:03 AM »
This premise is flawed. The Arctic was / is warmer than the continents in June (and July) and the only cold areas were limited to snow-covered land areas adjacent to increasingly open peripheral sea waters (it looks like the lack of ice in Bering has allowed much more mountain snow to accumulate in NE Siberia, for instance). Actual anomalous cold was centered over Quebec, parts of Russia, and the Alaskan shoreline (which, this year, has a raft of MYI sheltering it from warmth -- in fact Barrow just saw its snowiest July day since 1963). The Arctic has been warm. The adjacent land has been occasionally and in some areas, consistently, cold. This cold is limited to areas that have retained / regenerated albedo anomalies. The feedback is now becoming very obvious and while others may exist the albedo - SST seesaw we are now witnessing may overwhelm everything else.

FredBear

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Re: Warm Continents Cold Arctic. Negative Feedback? (sometimes)
« Reply #2 on: July 12, 2018, 12:30:01 PM »
bbr, actual 2m air temps are generally higher over land than the central Arctic (apart from Greenland), your map shows anomalies.

Michael Hauber

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Re: Warm Continents Cold Arctic. Negative Feedback? (sometimes)
« Reply #3 on: July 13, 2018, 12:59:55 AM »
This premise is flawed. The Arctic was / is warmer than the continents in June (and July) and the

That massive heat dome over Europe looks a lot stronger than the heat over the Arctic.  Also note Greenland, and to some extent the Canadian Archipelago is part of the cold Arctic, that is ice covered regions that are not warming up as fast due to the persistent presence of ice.  I'd say the chart supports my theory.

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DavidR

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Re: Warm Continents Cold Arctic. Negative Feedback? (sometimes)
« Reply #4 on: July 13, 2018, 02:58:52 AM »
In 2012 ...  The GAC was of course followed by massive loss of ice, although there is an argument that the ice had already been set up to melt by previous conditions and the GAC played a relatively minor role.
If we look at that from a volume perspective 2012 didn't lose that much ice after the cyclone.
           Aug 1 Vol          Aug Loss           Aug  Loss after Aug 9
2010   7.283K km^ 3   2.483K km^3    1.764K km^3
2012   6.538K km^3    2.619K km^3    1.774K km^3
2015   8.483K km^3    2.521K km^3    1.944K km^3
2016   7.449K km^3    2.808K km^3    2.006K km^3
2017   6.616K km^3    1.945K km^3    1.264K km^3

As you can see the ice loss in August was greater in 2016 than 2012 and in both 2015 and 2016 the ice loss after August 9 when the GAC was finished was also greater than 2012. Even 2010 went very close to the 2012 loss after August 9. However the 2012 ice was much thinner at the start of August leading to much greater extent  loss in August than in 2010, 2015 or 2016. I think there is a lot of substance to the view that  it was the thinness at the start of August  that  was responsible for the greater extent  loss in 2012. 
« Last Edit: July 13, 2018, 03:16:38 AM by DavidR »
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