Arctic Sea Ice and the Atlantic Oscillation


Last week in the article about the Natural Cause of global warming I pointed out that the Atlantic Multidecadal Oscillation (AMO for the rest of the article) correlated to the warming trend that started in the 1970’s. The AMO temperature and the global temperature have gone up together. Since it is known that the AMO is a natural event, the affects of the AMO are also natural.  The difficulty in understanding the AMO is that it happens on a much longer time scale than most people are used to dealing with.  It is a long term cycle, at least on a human time scale.

In the earlier article I pointed out that such a warming in the Northern Atlantic Ocean would certainly have an impact on the Arctic sea ice. Today I am going to show that by going into the comparison of the AMO temperatures and the Arctic sea ice.

Today will also be the first time I put some of the discussion under the label of Science Content. That section will have some added details of the science of this topic. To keep the article from being a long drawn out technical manual (which is what happens when engineers get going) I will keep that part separate.

Measurements of the Arctic sea ice started at the end of 1978. Unfortunately that was after the AMO had already started trending up in temperature. It had already gone up about 0.2 °C by the time the Arctic ice was being measured. So the ice was already being impacted by the warming Atlantic Ocean.

Once more I will show the graph that compares the AMO and Global temperatures from the 1970’s until the current day.

Inconvenient Skeptic

40 Year Comparison of AMO and Global Temperature Anomaly

The impact of the AMO on global temperatures is clearly evident. Now I will show the SST (Sea Surface Temperature) of the Earth and then a more focused section of the Atlantic with the area that is primarily impacted by the AMO.

Inconvenient Skeptic

SST Anom Sep 19, 2010

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Here is the AMO impacted portion of the Atlantic.


Inconvenient Skeptic

Sep 19, 2010 SST Anom, AMO portion only.

Since a strong portion of the warm AMO is around Greenland, it makes perfect sense that the AMO would cause the sea ice to be reduced in that area.  The warmer the AMO gets, the more it should reduce the ice extent.  With that in mind, here is what the sea ice has done in the period of time that the AMO has been transitioning to the warm phase and then been stable in that phase.

Inconvenient Skeptic

AMO impact on the Arctic sea ice extent.

Aside from the overall trend that an increasing AMO correlates to an overall trend in decreasing Arctic extent, there are some very interesting specific correlations as well.  The surge in warm AMO in 88-91 resulted in a drop in extent from 89-91.  Then when the AMO cooled from 92-95, the extent increased in a natural response.

Then in 2003-2006 as the AMO reached a maximum level, the sea ice dropped dramatically. The AMO then dropped for a couple of years and the sea ice then started increasing again. The AMO and the sea ice and the AMO are looking to be comparable for the current year as well.  I will put out an update when this year completes.

This shows that the Arctic sea ice extent appears to be greatly impacted by the warm phase of the AMO and also by the strength of the AMO for any group of years. It is really too bad that there is not satellite data of the sea ice extent from the warming AMO of 1913-1940. That would very likely confirm this correlation of the extent to the AMO.

This does show that one of the main dangers that is attached to global warming is really just another indicator of the natural cycle of the Atlantic Multidecadal Oscillation. There are more of these and in the future I will also be putting together more articles on each of the various impacts that the AMO has on the Earth’s climate. Most of these natural impacts are also being used as “proof” of global warming.

The Earth is always changing. That is first thing that everyone must understand.

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Warning!!!! Science Content Ahead:

Do not drive or operate a vehicle while reading science content. We are not responsible for naps or other sudden issues of falling asleep while reading the following. 😀

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The first step is to understand what is being measured when people discuss the sea ice.

Sea Ice Extent: The sea ice extent is the area that is covered by at least 15% ice.

Sea Ice Area: The amount of area that is completely covered by ice.

There are advantages and disadvantages to each measure, but extent is the one that is used most often and that is the one that I used as well.

Both are measured by daily analysis of satellite pictures taken of the Arctic. The two main problems with the Area measure is that the satellite does not actually take a picture of the very top of the Earth. It is safe to assume that the north pole is always at least 15% sea ice, but that assumption on the area is not a safe assumption.

The other problem with area is its accuracy. It is easy to tell if there is 15% ice in water. It is not always possible to determine if an area is 100% ice. During the summertime, areas that are solid ice get covered with meltwater ponds. Since the ponds are water on top of ice it is difficult to determine from a satellite image if it is water covered ice or just ocean.   So even if the ice is solid, it is beneath melted water that can appear to be open water.

Those two factors mean the error for area will always be greater. Extent is not perfect, but it is accurate and sensitive enough for most purposes.

Data Sources:

Sea Ice Data Source:  I compiled the monthly averages into the annual average.  This has the effect of reducing odd monthly results and also makes comparison easier.

AMO Data Source:  I used the AMO unsmooth long format.  Again made into the annual averages.

Posted in Science Articles - Global Warming by inconvenientskeptic on September 21st, 2010 at 4:00 am.

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This post has 6 comments

  1. I’ve recently started a blog, the information you provide on this site has helped me tremendously. Thank you for all of your time & work.

  2. Here is my comment on the Watts Up with That website.

    http://wattsupwiththat.com/2010/10/04/sea-ice-news-delayed-a-day/

  3. Try this for a proxy: http://en.wikipedia.org/wiki/List_of_Arctic_expeditions – note the frequency variation?

  4. inconvenientskeptic Oct 4th 2010

    It would be an interesting reconstruction to put together. I am confident that it would show the same oscillation that the oceans naturally have.

    It would be circumstantial evidence though. While it would be useful for people that use common sense, I doubt it would convince many people.

    My initial focus would be on the expeditions in the 1920’s and 1930’s. Those are the ones that I would expect to show greatly reduced sea ice.

    What is known is the navigation of the Northwest Passage. The first was in 1906 which was as the AMO was switching to cool. The ship was locked in ice and Roald Amundsen had to walk the end part.

    It wasn’t until 1940 when the AMO was in the full warm phase that it was fully navigated by sea. This was the Henry Larsen from Canada. When he returned in 1944 it only took much less times which would make sense as the ice would have been less based on the duration of the AMO.

    After that technology made it more possible for specially designed trips. I do find it interesting that it was only during the warm AMO that such a trip is possible without modern ice breaker technology.

  5. The first step is as good as half over.

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    Sydney

  6. Great work keep it coming

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