Climate

Our Extreme Weather: Is Arctic Sea Ice Loss Partly to Blame?

— by Jeff Masters in a Wunderblog repost

“The question is not whether sea ice loss is affecting the large-scale atmospheric circulation…. It’s how can it not?” That was the take-home message from Dr. Jennifer Francis of Rutgers University, in her talk “Does Arctic Amplification Fuel Extreme Weather in Mid-Latitudes?”, presented at last week’s American Geophysical Union meeting in San Francisco.

Dr. Francis presented new research in review for publication, which shows that Arctic sea ice loss may significantly affect the upper-level atmospheric circulation, slowing its winds and increasing its tendency to make contorted high-amplitude loops. High-amplitude loops in the upper level wind pattern (and associated jet stream) increases the probability of persistent weather patterns in the Northern Hemisphere, potentially leading to extreme weather due to longer-duration cold spells, snow events, heat waves, flooding events, and drought conditions.


Figure 1. Arctic sea ice in September 2007 reached its lowest extent on record, approximately 40% lower than when satellite records began in 1979. Sea ice loss in 2011 was virtually tied with the ice loss in 2007, despite weather conditions that were not as unusual in the Arctic. Image credit: University of Illinois Cryosphere Today.

Summertime Arctic sea ice loss: 40% since 1980

The Arctic has seen a stunning amount of sea ice loss in recent years, due to melting and unfavorable winds that have pushed large amounts of ice out of the region. Forty percent of the sea ice was missing in September 2007, compared to September of 1980. This is an area equivalent to about 44% of the contiguous U.S., or 71% of the non-Russian portion of Europe. Such a large area of open water is bound to cause significant impacts on weather patterns, due to the huge amount of heat and moisture that escapes from the exposed ocean into the atmosphere over a multi-month period following the summer melt.


Figure 2. The extent of Arctic sea ice loss in the summer July – August – September period in 2007 was about 1.4 million square miles (3.6 million square kilometers) greater than in 1980, according to the University of Illinois Cryosphere Today. For comparison, the lost ice coverage (orange colors) was equal to an area about 44% of the size of the contiguous U.S., or 71% of the non-Russian portion of Europe.

Arctic sea ice loss can slow down jet stream winds

Dr. Francis looked at surface and upper level data from 1948 – 2010, and discovered that the extra heat in the Arctic in fall and winter over the past decade had caused the Arctic atmosphere between the surface and 500 mb (about 18,000 feet or 5,600 meters) to expand. As a result, the difference in temperature between the Arctic (60 – 80°N) and the mid-latitudes (30 – 50°N) fell significantly. It is this difference in temperature that drives the powerful jet stream winds that control much of our weather.

The speed of fall and winter west-to-east upper-level winds at 500 mb circling the North Pole decreased by 20% over the past decade, compared to the period 1948 – 2000, in response to the extra warmth in the Arctic. This slow-down of the upper-level winds circling the pole has been linked to a Hot Arctic-Cold Continents pattern that brought cold, snowy winters to the Eastern U.S. and Western Europe during 2009 – 2010 and 2010 – 2011.


Figure 3. West-to-east jet stream wind speeds at 500 mb (approximately 18,000 feet or 5,600 meters) in the mid-latitudes (40 – 60°N) over North America between 1948 and 2010. During fall (October – November – December) and winter (January – February – March), jet stream winds weakened by about 20%, from 13 – 14 m/s to 10.5 – 11 m/s. Spring (AMJ) and summer (JAS) winds changed little during this time period.

Arctic sea ice loss may increase the amplitude of jet stream troughs and ridges

The jet stream generally blows from west to east over the northern mid-latitudes, with an average position over the central U.S. in winter and southern Canada in summer. The jet stream marks the boundary between cold polar air to the north and warm subtropical air to the south, and is the path along which rain and snow-bearing low pressure systems ride. Instead of blowing straight west-to-east, the jet stream often contorts itself into a wave-like pattern. Where the jet stream bulges northwards into a ridge of high pressure, warm air flows far to the north. Where the jet loops to the south into a trough of low pressure, cold air spills southwards. The more extreme these loops to the north and south are–the amplitude of the jet stream–the slower the waves move eastward, and consequently, the more persistent the weather conditions tend to be.

A high-amplitude jet stream pattern (more than 1000 miles or 1610 km in distance between the bottom of a trough and the peak of a ridge) is likely to bring abnormally high temperatures to the region under its ridge, and very cold temperatures and heavy precipitation underneath its trough. The mathematics governing atmospheric motions requires that higher-amplitude flow patterns move more slowly. Thus, any change to the atmosphere that increases the amplitude of the wave pattern will make it move more slowly, increasing the length of time extreme weather conditions persist.

Dr. Francis discovered that during the early 1960s, a natural pattern in the atmosphere called the Arctic Oscillation increased the amplitude of the winter jet stream pattern over North America and the North Atlantic by more than 100 miles, increasing the potential for long-lasting weather conditions. The amplitude of the winter jet fell over 100 miles (161 km) during the late 1960s, remained roughly constant during the 1970s – 1990s, then increased by over 100 miles again during the 2000s. This latest increase in wave amplitude did not appear to be connected to the Arctic Oscillation, but did appear to be connected to the heating up of the Arctic due to sea ice loss. A warmer Arctic allows ridges of high pressure to build farther to the north. Since temperatures farther to the south near the bases of the troughs are not changing much by comparison, the result is that the amplitude of the jet stream grows as the ridges of high pressure push farther to the north. Thus it is possible that Arctic sea ice loss and the associated increases in jet stream amplitude could be partially responsible for some of the recent unusual extreme weather patterns observed in the Northern Hemisphere. This is preliminary research that has yet to be published, and much more work needs to be done before we can confidently link Arctic sea ice loss with an increase in extreme weather, though.


Figure 4. A high-amplitude jet stream pattern observed over the U.S. on December 13, 2011. Instead of blowing straight west-to-east, the jet was contorted into a southward-bulging trough of low pressure that brought cold temperatures and a snow storm to Southern California, and a northwards-bulging ridge of high pressure that brought record warm temperatures to portions of the eastern 2/3 of the country. The axis of the jet stream is marked by the strongest winds (green and light blue colors) at the top of the lower atmosphere (200 – 300 mb pressure level.)

Earlier snow cover melt on Arctic land also increases the amplitude of jet stream troughs and ridges

As Earth’s climate has warmed over the past 30 years, the Northern Hemisphere has seen a dramatic drop in the amount of snow cover in spring (April, May, and June.) Spring is coming earlier by an average of three days per decade, and the earlier arrival of spring has significantly reduced the amount of snow on the ground in May. Less snow on the ground means the land surface can heat up more readily, and May temperatures in Arctic have increased significantly over the past 30 years. Dr. Francis found that the upper-level wave amplitude has increased by over 100 miles (161 km) in summer over the past decade, and this change appears to be connected to the decline in May snow cover. Thus, reduced May snow cover due to global warming may be causing higher-amplitude jet stream patterns, potentially leading to slower-moving weather patterns that favor extreme weather in summer, such as heat waves, drought, and flooding. Note that significant changes to the upper-level atmospheric circulation in spring were not observed, so springtime extreme weather events like the 2011 flooding and tornadoes in the U.S. cannot be connected to changes in the Arctic sea ice or high-latitude snow cover using this research.

by Jeff Masters in a Wunderblog repost

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21 Responses to Our Extreme Weather: Is Arctic Sea Ice Loss Partly to Blame?

  1. prokaryotes says:

    The polar ice cover imaginary is eye dropping.

  2. prokaryotes says:

    Howto make our environment, the habitat, mother Earth herself more hostile and in general a less friendly place to inhabit?

    “… extreme weather due to longer-duration cold spells, snow events, heat waves, flooding events, and drought conditions.”

    Oh, this is just the beginning, another stage in an fundamental, cataclysmic chain reaction of epic disaster proportions.

    Welcome to HELL in slow motion…

    Children who are born today will only know this deteriorating climate stage. Not only will a more extreme weather pattern be the new normal, the negative affects are profound and disastrous. It starts with the psychological stage of each inhabitant. Solastalgia ( What Does Climate Change Do to Our Heads? http://www.worldchanging.com/archives/007906.html ) describes this we can start to create poems and tales of past Holozenic conditions.

    And we should do something about climate change. Watching this unfold is not only a bad decision.

    A small yet growing body of evidence suggests that how people think and feel is being influenced strongly by ecosystem transformation related to climate change and industry-related displacement from the land. These powerful stressors are occurring more frequently around the world.

    A case in point: When researchers from the Centre for Rural and Remote Mental Health at the University of Newcastle in Australia conducted interviews in drought-affected communities in New South Wales in 2005, the responses suggested some of their subjects may have been suffering from a recently described psychological condition called solastalgia (pronounced so-la-stal-juh).

    Solastalgia describes a palpable sense of dislocation and loss that people feel when they perceive changes to their local environment as harmful. It’s a neologism that Glenn Albrecht, an environmental philosopher at the University of Newcastle’s School of Environmental and Life Sciences, created in 2003. http://www.worldchanging.com/archives/007906.html

  3. Merrelyn Emery says:

    Yes, it is enough to make you Cry. But keep your eyes on the Antarctic as well. I heard last week that Western Antarctica has actually warmed faster than any place on Earth – about 5C rather than .8C on average.

    Sorry, I can’t remember where I heard it but it was from a scientist who has been studying the Antarctic, ME

  4. wvng says:

    I’ve been waiting to see if the weather pattern of the last two winters is re-established in the East, with very persistent below freezing weather extending into the deep South, to see if this becomes the norm rather than an exception.

  5. Mulga Mumblebrain says:

    I saw an interesting doco on epigenetics where the role of the environment in influencing the expression of genes was discussed (for the layest of lay persons). Apparently the effects of famine could be discerned in people several generations after, because the genetic changes were, contrary to the researchers’ expectations, heritable. I do not doubt that severe psychological stresses might be similarly influential on gene expression, with unknowable consequences. We are compressing millennia of changes, to the environment, ourselves and our societies, into decades, and that cannot be inconsequential or beneficial.

  6. Rabid Doomsayer says:

    So much potential for snap weather changes. How long before some poor schmuck goes out appropriately dressed in shorts and a tee shirt and gets frozen to death in a sudden blizzard? Go into the office after lunch with ninety degrees and come out to minus ten.

    Even the plant world responds better to a long slow deep freeze than a milder but sudden one.

  7. Merrelyn Emery says:

    Epigenetics is a rapidly growing field and I just hope that poor old Lysenko is listening in and saying ‘I told you so!’, ME

  8. harvey says:

    Problems not just with Arctic Ice, but with permafrost as well…

    http://www.permafrost.su/

  9. Tim says:

    On the same subject, the NYT had a decent article yesterday. Deniers were not labeled as the propagandists they are, but rather as “contrarians” and members of “an organization called Center for the Study of Carbon Dioxide and Global Change”. They were, nevertheless, clearly distinguished from “mainstream scientists”.

  10. SecularAnimist says:

    The “Center for the Study of Carbon Dioxide and Global Change” is a propaganda mill funded by ExxonMobil and run by the Idso brothers, who are paid propagandists for the Western Fuels Association. For the New York Times to cite them, in an article that is ostensibly about scientific research, without mentioning that they are an industry-funded propaganda mill — indeed without giving ANY description of the Center or ANY reason why its views are cited, is reprehensible.

    One would have hoped we were past the point where major media organizations felt it necessary to spike every article on climate science with talking points from ExxonMobil’s mouthpieces to “balance” the statments of, well, actual scientists. But sadly, that is not the case.

  11. Colorado Bob says:

    Looking at the cyclone in the Philippines .

    First reports just said that one months rain fell in 12 hours . Now Bloomberg is reporting this :
    ” The storm dumped 181 millimeters of rain per hour compared to the 25 millimeters per hour typical in the region, said Benito Ramos, administrator of the Office of Civil Defense.”
    http://www.bloomberg.com/news/2011-12-17/philippine-storm-kills-177-250-missing-after-flash-floods.html

  12. prokaryotes says:

    Yes me too.

    I did not looked it up but what is going on with the NAO and overall data plotted to current observed events?

    My guess, to warm (temps – for now), to late (season cycle out of balance) and “strange” (precipitation patterns).

  13. prokaryotes says:

    This doesn’t necessarily contradicts the first statement.

  14. Tim says:

    Yes, it was obvious that the “Center for the Study of Carbon Dioxide and Global Change” is a propaganda mill. My point was that although the NYT does devote one short paragraph to their BS, the rest of the article is pretty good…and, as I indicated, at least the NYT did distinguish the propaganda group from “mainstream scientists”.

  15. JeffId says:

    The West Antarctic warmed by about 0.1C/Decade over the last 50 years. Steig et al. overestimated it at about 0.26C/Decade. East Antarctic showed little trend and the Antarctic average temp was not significant or barely significant depending on calculation methods.

    Deep breath folks.

  16. Yvan Dutil says:

    This is a common phenomenon in Calgary, Canada due to the Chinook.

  17. wvng says:

    My organization just facilitated a one day meeting on the challenges of doing environmental restoration in a changing climate. One of the issues is the northward drift of southern species, including pests and invasives. However, if the long cold winter becomes a feature in the mid latitudes, it could effectively block this movement. I’m imagining a yearly cycle with very cold winters, very hot and dry summers, and periodically very very wet springs and falls like this year. Hard for ecosystems to adjust. http://potomacpartnership.org/pwp_resources.html#info

  18. Scrooge says:

    So if I get this right…. with the arctic warming faster the gradient is weaker causing the jets to slow which allows the amplitude to increase…. Does this go along with opening the refrigerator door idea which gives some regions colder winters than normal?

  19. umm what’s the Antarctic got to do with this post about the warming Arctic?

  20. Got to agree with secular on this. No doubt an editor at NYT told the jurno to find a contrary opinion for ‘balance’. It might make sense if the astroturfers actually researched permafrost. Not hard to find some group that will say “no it isn’t!” to the sun rising