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
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Tropical Cyclone Outlook
15:00 PM RET December 18 2011
=================================
The low at 1005 hPa, which has developed over the last 48 hours between 70E to 80E, crossed the 30 South parallel last night. It became fully extra-tropical and is moving southeastward.
According to last ASCAT (0327Z) data, 25-30 kt winds still exist in the South of the system, mainly due to the gradient effect with the subtropical high pressures.
East of a low pressure area centered on the South of Madagascar (1006 ha), convective activity is moderate to strong from south-southeast of Madagascar to Mascarenes Islands. 0647Z ASCAT pass shows winds at about 20-25 kt off southern Madagascar. All available NWP models are in good agreement for rapid development of a low during next night or Monday morning in the area between 23S/25S and 48E/50E. Indeed, last observations of eastern coast of Madagascar (0900Z) seem to suggest a start of deepening within this area (-4.6 hPa/24h at Farafangana). This cyclogenesis seems clearly to be due to baroclinic factors (enhanced instability with a mid to upper level cold low over low level warm air). It is expected that this low gets around the southern coast of Madagascar westward and so evolves over SST in the range of 25-27C and benefits from a weak vertical wind shear under the upper level cold trough. So, it appears that this low could gain thereafter some subtropical hybrid characteristics (ie tropical and extra-tropical influences).
Regardless of the nature of this system, it should be associated with strong winds (30-35 kt and
perhaps 40 kt at least in the southern semi-circle with the gradient effect) and strong convective
activity between Madagascar and the Mascarenes islands.
For the next 36 hours, potential for development of a subtropical depression is fair to good.
Tropical Cyclone Advisory #43
TROPICAL STORM WASHI (T1121)
3:00 AM JST December 19 2011
===============================
SUBJECT: Category One Typhoon in South China Sea
At 18:00 PM UTC, Tropical Storm Washi (1000 hPa) located at 9.8N 114.3E has 10 minute sustained winds of 35 knots with gusts of 50 knots. The cyclone is reported as moving west southwest at 7 knots
Dvorak Intensity: T2.5
Gale Force Winds
===============
120 NM from the center in northern quadrant
80 NM from the center in southern quadrant
Forecast and Intensity
======================
24 HRS: 7.2N 109.3E - Tropical Depression
bob breck
Link - AO analysis/forecast from CPC.
Yesterday I surmised that a certain level of complacency about the potential impacts of tropical storms might have contributed to the limited reaction of the people in this area, and it seems I was right.
However, what is striking me today is the information I'm reading about the changes in land use over the last few years. Logging, mining and farming in areas previously covered by tropical forest seem to have played a pivotal role in the unprecedented effects of Washi on Mindanao island. Perhaps areas that were severely impacted by 15 - 30 feet of water due to this storm were less likely to flood 30 or 40 years ago, creating a kind of complacency that seemed quite justified to the people experiencing it. Of course, there are obvious parallels here for similar river valleys in other parts of the world [e.g. the Susquehanna, where the Binghamton area was severely impacted this year due to torrential rains and flash flooding] where land use has changed dramatically over the last 100 years in ways that exacerbate this kind of disaster.
CI# /Pressure/ Vmax
2.9 /1002.0mb/ 43.0kt
Raw T# 2.6
Adj T# 2.6
Final T# 2.6
Scene Type: CURVED BAND with 0.38 ARC in MD GRAY
JB
ECMWF apparently won't show his message.
:(
Yes and no.
If you're only looking at sea level impacts, then the melting arctic isn't going to have too much of an impact (unless you throw in Greenland as well). However, weather wise it will have a substantial impact. And then there's the melting permafrost which will contribute additional GHG's.
The arctic will probably be ice free in the summer within the next decade or so, barring some unforeseen event. However, Greenland and the Antarctic aren't going to fully melt for quite some time.
so the ECMWF says the following:
-------------------------
REMOTE LINKING DISABLED
-------------------------
LOL!!!!!!!!!
It's 76 degrees outside...better wear my jacket! XD
Pfft.
Pasadena, MD
35.9 °F
your showing us nothing but a block box they you have too up lode it too imageshack then up lode it too the blog
In Puerto Rico, it's rare to get below 60 degrees, even in winter.
In fact, it's rare to get below 75 degrees
near the coastline...
your always here to say that, lol. i have been waiting for that =P
Selfish ECMWF.......
i wish it was that here...45 right now in my area. and i was outside wearin a T-shirt lol
It's going to be an above average hurricane season, but not as active as 2010 and 2011. Something similar to 2004.
14-15 named storms. 8-9 hurricanes. 4-5 major hurricanes.
When I used to get up at 6am, like two years ago, the normal morning temp in my area was 68 - 69 F.
So going below 75F is normal for Puerto Rico, now, going below 65F is rare(unless you're in the mountains).
My area's (Carolina's Coast) record is 59F.
So I agree... 75 is reason to take out the jacket.... lol
I have friends who recently moved from FL to the Denver, CO area... I think they're going to be extra cold this winter...
how many times do i have too keep saying this you guys that are posting from that site you can this link them here too the blog you are SHOWING US NOTHEING BUT A BLACK BOX of nothing you have too up lode it too imagsack and then post them here
It doesn't have to be accuweather.com pro. Follow the Henry Margusity Fan Club on Facebook... He posted that map a few hours ago.
No Texans on tonight.. today in Austin we had the odd clouds that aren't mammalia, but close to it, look like the plastic forms that good imported pears and apples sit on. Supposedly a good chance of extreme weather in TX tomorrow.
never listen to 30 Hz bass notes while having a headache. it makes it worse xD
SOPA will take care of that.
?
People are not supposed to post images from Pro AccuWeather, which is why people have to pay. I believe it is illegal to post images in public.
:( That's kind of ridiculous.....
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