Our extreme weather: Arctic changes to blame?
"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.
Related posts
Florida shivers; Hot Arctic-Cold Continents pattern is back
Jet stream moved northwards 270 miles in 22 years; climate change to blame?
Jeff Masters
Reader Comments
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I especially like this one...and must insist, Nea, that you henceforth refer to me in this way: "Dear Leader, who is a perfect incarnation of the appearance that a leader should have"
The original captures the flavor better. Don't ya think?
R.I.P.
More pictures at kim jong-il looking at things.
Thomas Grove and Melissa Akin
Moscow— Reuters
Published Sunday, Dec. 18, 2011 12:29PM EST
Last updated Sunday, Dec. 18, 2011 12:30PM EST
A drilling rig with 67 crew on board capsized and sank off Russia’s far eastern island of Sakhalin on Sunday while being towed through a winter storm, leaving more than 50 dead or missing in the icy Sea of Okhotsk.
Emergency officials said the crew of an icebreaker and tugboat rescued 14 workers alive from the jack-up rig, the ‘Kolskaya’, which was operated by a Russian offshore exploration firm. They recovered four bodies from the water.
SO ALL IN ALL AFTER TEMPERATURES BRIEFLY DIPPED BACK TO NEAR AVERAGE VALUES FOR MID DECEMBER, TEMPERATURES WILL GRADUALLY WARM BEGINNING MONDAY NIGHT AS THE WIND VEERS BACK TO THE EAST TO SOUTHEAST OFF THE WARMER ATLANTIC WATERS AND BY THE MIDDLE OF THE WEEK THROUGH THIS CHRISTMAS WEEKEND WILL REBOUND BACK TO WELL ABOVE NORMAL LEVELS FOR THIS TIME OF YEAR. AS A SIDE NOTE, DOES ANYBODY REMEMBER DECEMBER 2010? IT WAS THE COLDEST DECEMBER ON RECORD FOR MANY S FL SITES AND THIS DECEMBER IS RANKING AS ONE OF THE WARMEST ON RECORD. WHAT A DIFFERENCE A YEAR MAKES.
Living in central New York, it always amuses me (in an annoying way) when Texas and Oklahoma get snow before we do... let alone blizzard warnings. I mean, I know it happens quite a bit actually, but Texas? come on now- we were just getting used to their perpetual fire ball of a drought :P
...its been (relatively) warm with a weekly bout of rain all month... no wintery weather at least through Friday :/
Tropical Cyclone Outlook
Forecast for the Coral Sea west of 160E
1:45 pm EST December 19 2011
===================================
A low situated southeast of Papua New Guinea is moving in a south-southwesterly direction and is expected to develop further over the next couple of days. The low is expected to remain offshore and not affect the Queensland coast.
Tropical Cyclone Formation Potential
======================================
Tuesday: Low
Wednesday: High
Thursday: High
Tropical Cyclone Advisory #47
TROPICAL DEPRESSION, FORMER WASHI
15:00 PM JST December 19 2011
===============================
SUBJECT: Tropical Depression In South China Sea
At 6:00 AM UTC, Tropical Depression, Former Washi (1004 hPa) located at 9.0N 112.0E has 10 minute sustained winds of 30 knots with gusts of 45 knots. The cyclone is reported as moving west southwest at 10 knots
This is the final tropical cyclone advisory from the Japan Meteorological Agency
Would you believe they didn't even feel it, it was to deep and so small it went unnoticed.
It will be Kim Jong Il before then. A nice strong cold front is moving south out of China and it will take care of it. I would say, this is the last of the season for the WPAC.
As you wish.
Today its about +9/c and raining which is more or less set to continue all week with no white Christmas in England, forecast. Interesting to say the least.
We're still thinking about what all that moisture that is going to be whipped up from the projected liquid Arctic ocean and what it is going to do to the northern latitudes. After all, wind blowing over ice compared to wind blowing over an ocean produces 2 entirely different levels of moisture content in the atmosphere.
The system will spread east as rain, but if it were cold enough, it'd be a major winter storm, because there are going to be some hefty rainfall totals across the Ohio Valley and North/Southeast.
DING DONG THE WICKED WITCH IS DEAD!
BY MID/LATE WEEK FCST HIGHS WILL BE SOME 5F DEGREES ABOVE AVG
WITH LOWS SOME 5-10F DEGREES ABOVE AVG. SO OUR WARM DECEMBER
CONTINUES. QUITE THE DIFFERENCE FROM LAST DECEMBER. CASE IN
POINT...TAKE WEST PALM BEACH FOR EXAMPLE...THE AVG LOW SO FAR FOR
THIS DEC IS 68.3F DEGREES. LAST DEC THE AVG LOW THERE WAS 47.5F
DEGREES...THAT`S A +20.8F DEGREE DIFFERENCE!
FOR THE UPCOMING WEEKEND...SHORTWAVE ENERGY PASSES WELL NORTH OF
FLORIDA. GFS SHOWS MORE RIDGING THAN THE ECMWF. ECMWF OUTPUTS A
NOR`EASTER AFFECTING SOUTHERN NEW ENGLAND ON CHRISTMAS DAY WITH
THE TAIL END OF THE COLD FRONT MOVING INTO SOUTH FL BUT
DISSIPATING...SO OF LITTLE CONSEQUENCE. SO EITHER WAY...EXPECT
TRANQUIL WEATHER WITH JUST A SLIGHT CHANCE OF SHOWERS...ALONG
WITH CONTINUED WARM TEMPS. SO A WARM CHRISTMAS IS EXPECTED.
THERE ARE SOME PROSPECTS FOR SOME COOLER WEATHER NEXT WEEK AS PER
THE GFS/ECMWF...BUT DETAILS/FCST CONFIDENCE LOW THIS FAR OUT.
OVERALL PATTERN SUGGEST NO "COLD" AIR IN SIGHT THOUGH.
Been very warm up here as well. Infact low to mid 80's from about Wed on here in C FL. I remember many nights in the teens and 20's last December. Some of the Citrus growers around here are still suffereing from last year's freezes.
Amen to that!
Who says RIP to a brutal dictator that has killed many (thousands)of people and was planning a nuclear war at on point?
I think #10 pretty much covers all of the bases.
Enjoy your Monday.
It snows in Texas every year. Just more in some parts and less to none in others.
Actually the latest models(even the Euro) have a full-latitude trough in the northeast by Saturday(Christmas Eve). Proceeded from a series of disturbances(Tuesday-Friday) trying to break-down the SE Ridge(but only managing to flatten or at least shunt it southeastward by Friday) This should give us a cool/dry Christmas Weekend(similar to this one) in Central Florida.
Once the Euro has something(the synoptics) etched in stone 5 days in advance, that pretty much means it's gonna happen(though there are rare exceptions to that rule).
Though by early next week(Tuesday/27th), models are confused on what'll take place before New Years Eve. Some call for a cool/warm rainy week(subtropical Jet goes haywire). While others opt for a more chilly scenario(60's/40's).
But yeah an active Subtropical Jet with Stratospheric warming going on in Polar Siberia do indeed indicate a massive pattern shift by January/February! Somewhat similar to December 1984.
How Santa could lay the foundation of his workshop on ice in the first place is beyond me. lol
Magic
Its been dry for the most part the past 2 weeks here in T&T but that is going to change,that trough just to our east is supposed to move in and settle in for a few days,when we get troughs in Dec\Jan. it usually floods bad especially during la ninas.
Irony is lost on you.
and compare it to this
I don't see the connection. The jet stream should have weakened long ago. I don't doubt that vast areas of water where there was once ice doesn't affect weather but it seems other things are at work here too.
If I saw anything to correlate the two by eye it would be summer sea ice affects winter jet stream.
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