How melting Arctic ice is driving harsh winters

by Nick Breeze

The very least 'global warming' could do for us is to give us warmer winters, right? Wrong, writes Nick Breeze, who met climate scientist and meteorologist Jennifer Francis in his attempt to understand the complex interactions of jet stream, polar vortex, the melting Arctic, and the extreme snowfall that's hitting the northeast US right now.

"Historic" snowfalls have the US northeast this week, with Buffalo, New York under an astonishing 2.4m (8ft) of snow - enough to cause some roofs to cave in under the pressure.

It's just the latest chapter in 2014 unprecedented range of weather extremes - from persistent storms that battered, and flooded much of the UK at the beginning of the year, before going on to record the hottest October since records began.

And in the US, extremes have ranged from California's record drought, to the early snows now under way in the northeast - and let's not forget the 'polar vortex' that hit much of the US in January, bringing Arctic conditions as far south as Texas and Florida, causing flights to be cancelled in Chicago as aviation fuel froze in the -38.3C (-37F) temperatures.

Scientists now have evidence that these persistent extreme weather patterns are increasing in their frequency, due to the rapid heating up of the Arctic that is changing the behaviour of the jet stream, and in turn, the polar vortex.

And Jennifer Francis of Rutgers University, one of the leading US scientists studying the relationship between Arctic warming and changes in the jet stream, believes that it's thanks to 'global warming' that northern hemisphere weather is becoming more extreme - and it's not about to get any better.

Screenshot from Youtube video further below

The 'vast river of wind' that makes our weather

"The Arctic is generally very cold", she told me, "and the areas farther south are warm, and that difference in temperature between those two areas is really what fuels that vast river of wind moving high over our head that we call the jet stream."

"The jet stream in turn creates most of the weather that we feel all around the northern hemisphere and the middle latitudes, so anything that affects this jet stream is going to affect weather patterns. So as the Arctic warms up much faster than the areas farther south, we're seeing this temperature difference between these two regions get smaller."

The result of that, she explains, is that the atmospheric forces driving the jet stream's circular motion are getting smaller - and that means the winds themselves in the jet stream are getting weaker, and moving more slowly.

"When that happens, the jet stream tends to take a wavier path as it travels around the northern hemisphere and those waves are actually what create the stormy patterns and the nice weather patterns. As those waves get larger because of this weakening of those winds of the jet stream, they tend to move more slowly from west to east."

"That means it feels like the weather patterns are sticking around longer, because those patterns are moving much more slowly and this then makes it more likely to have the kind of extreme events that are related to persistent weather patterns."

Youtube video

Are critical findings influencing policy?

These changes in climate have huge implications. As Dr Francis points out, there are "people who worry about whether there is enough fresh water to supply cities, whether there is enough snowpack on mountains to supply reservoirs, and for agriculture ..."

"Drought and agriculture is a big problem. Storminess in certain areas is another big problem. Yes, it has a huge impact for a whole range of issues that affect the way we live."

It's no wonder then that Dr Francis and her colleagues have attracted the attention of President Obama's chief science advisor, Dr John Holdren.

Dr Holdren has been reporting directly to the President on the real time effects of climate change and is keen to understand what this new research tells us about the future impact of changes to the jet stream.

Asked about this sudden interest in her work from the US Presidency, Francis muses thoughtfully. "Yes, we've had a lot of interest from policy makers", she acknowledges.

"I think we're starting to make a lot of progress now in getting policymakers to understand that this is a big problem they have to face ... I think decision makers and the policymakers at the local level get it much better because they're already seeing effects on their local areas.

"Sea level rise is an obvious one. They're already seeing changes in drought and agricultural problems and dealing with fresh water issues. It is really at the local level that we're having more success."

New research supports the case that Arctic sea ice loss is driving climate changes

So to understand the changes in the jet stream it's important to research how the vast atmospheric river of weather above our heads is connected to other climate mechanisms.

"It appears that over the north Atlantic, and towards Asia, there's a mechanism that appears to be quite robust, and several groups have found this mechanism using completely different analysis techniques", says Francis referring to new research by colleagues at the University of Alaska that has emerged in the last couple of months.

"So what we're finding is that there's an area, north of Scandinavia in the Arctic, where the ice has been disappearing particularly rapidly. When that ice disappears ... there is unfrozen ocean underneath, and that ocean absorbs a lot more energy from the sun through the summertime. So it becomes very warm there."

"Then as the fall comes around, all that heat that's been absorbed all summer long, where the ice has retreated, is put back in the atmosphere and that creates a big bubble of hot air ... over that region where the ice was lost."

And in turn, that goes on to disrupt the circumpolar winds whose behaviour determines much the weather across the northern hemisphere.

The gigantic bubble of warm air "tends to create a northward bulge in the jet stream", and in turn, "that creates a surface high pressure area that circulates in the clockwise direction. That sucks cold air down from the Arctic over northern Eurasia, and that creates a southward dip in the jet stream."

Youtube video

The bulging jet stream disrupts the polar vortex

"So what we're getting is this big northward bulge up over Scandinavia and a southward dip over Asia ... creating, first the tendency for a larger wave in the jet stream, which tends to move more slowly, but also we're seeing this mechanism that creates these colder winters that have been observed over Central Asia."

"Once the jet stream gets into this wavier pattern, it sends wave energy up into the highest levels of the atmosphere, which is called the stratosphere, where we have the polar vortex, which is kind of similar to the jet stream but it's much higher up in the atmosphere and it travels much faster."

"So as that wave energy gets sent up from this larger wave below, up into the stratosphere, it breaks down that polar vortex so that it becomes wavier as well. That wavier polar vortex sends energy back down to the lower atmosphere and it creates an even wavier jet stream in February."

"So we're seeing this connection of mechanisms that starts with Arctic sea ice loss and it makes a wavier jet stream for different reasons all the way through winter."

Will the jet stream continue to cause changes in climate?

By identifying these mechanisms and linking them back directly to loss of the Arctic sea ice, Dr Francis and her colleagues are demonstrating how man-made global warming is creating feedbacks that are changing the climate conditions in the northern hemisphere - and not for the better.

It may be counterintuitive, and it when it first happened it took scientists by surprise - but now it looks like this is one of the most important ways in which 'global warming' is hitting North America. Melting ice in the Arctic Ocean is indirectly pushing frigid Arctic air south across the continent, creating the perfect conditions for massive snowfall.

Which is all very well ... but what's coming next? "We are using these climate models, or computer simulations ... to try and project what we're expecting to see happen in the future, as greenhouse gases continue to increase.

"The early indications are that these large wavy patterns in the jet stream are going to become more frequent in the future, as far as we can tell. It is preliminary research that I haven't published yet but it does look as if they are going to increase."

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Nick Breeze is a film maker and writer on climate change and other environmental topics. He has been interviewing a range of experts relating to the field of climate change and science for over four years. These include interviews with Dr James Hansen, Professor Martin Rees, Professor James Lovelock, Dr Rowan Williams, Dr Natalia Shakhova, Dr Michael Mann, Dr Hugh Hunt, among others.

Additional articles can also be read on his blog Envisionation.

Jennifer Francis is a research professor at the Institute of Marine and Coastal Sciences at Rutgers University, where she studies Arctic climate change and the link between Arctic and global climates. She has authored more than 40 peer-reviewed publications on these topics. She was also the co-founder of the Rutgers Climate and Environmental Change Initiative.

Article earlier posted at TheEcologist.org

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Related

- Wild Weather Swings
http://arctic-news.blogspot.com/2014/10/wild-weather-swings.html

- Buffalo’s Climate Change Driven Mega Snow-Flood
http://robertscribbler.wordpress.com/2014/11/21/buffalos-climate-change-driven-mega-snow-flood/

Post by Sam Carana.

More extreme weather can be expected

The heaviest rains and floods in 120 years have hit Serbia and Bosnia this week, Reuters and Deutsche Welle report.

The animation below shows the Jet Stream's impact on the weather. Cold temperatures have descended from the Arctic to Serbia and Bosnia in Europe and all the way down to the Gulf of Mexico in North America, while Alaska, California, and America's East Coast are hit by warm temperatures. In California, 'unprecedented' wildfires and fierce winds lead to 'firenadoes', reports CNN.

The image below shows that on May 15, 2014, the wind approaching Serbia and Bosnia at 700 hPa reached speeds of up to 120 km per hour (75 mph), as indicated by the green circle on the main image and inset.

The image below, from skeptical science, shows the cyclonic spin that can be expected in a through such as the one that hit Serbia and Bosnia recently.

As the Jet Stream changes, more extreme weather events can be expected. What makes the Jet Stream change? As the Arctic is warming up faster than the rest of the world, the temperature difference between the Arctic and the equator decreases, in turn decreasing the speed at which the Jet Stream circumnavigates the globe. This can cause 'blocking patterns', with extreme weather events hitting an area longer than before.

As the jet stream becomes wavier, cold air can more easily descend from the Arctic down to lower latitudes in a downward through of the Jet Stream, while warm air can more easily reach higher latitudes in an upward ridge of the Jet Stream.

This spells bad news for many areas across the world that can be expected to be hit by more extreme weather events such as heatwaves, wildfires fuelled by stronger winds and more intense drought, storms and floods.

Heatwaves are a huge threat in the Arctic, especially when followed by storms that can cause warm surface water to mix down to the bottom of the sea and warm up sediments under the seafloor that can contain huge amounts of methane in the form of hydrates and free gas. The situation is dire and calls for comprehensive and effective action, as discussed at the Climate Plan blog.


Related

- Extreme weather strikes around the globe - update
http://arctic-news.blogspot.com/2014/02/extreme-weather-strikes-around-the-globe-update.html

- Escalating extreme weather events to hammer humanity (by Paul Beckwith)
http://arctic-news.blogspot.com/2014/04/escalating-extreme-weather-events-to-hammer-humanity.html

- Our New Climate and Weather (by Paul Beckwith)
http://arctic-news.blogspot.com/2014/01/our-new-climate-and-weather.html

- Our New Climate and Weather - part 2 (by Paul Beckwith)
http://arctic-news.blogspot.com/2014/01/our-new-climate-and-weather-part-2.html

- Changes to Polar Vortex affect mile-deep ocean circulation patterns
http://arctic-news.blogspot.com/2012/09/changes-to-polar-vortex-affect-mile-deep-ocean-circulation-patterns.html

- Polar jet stream appears hugely deformed
http://arctic-news.blogspot.com/2012/12/polar-jet-stream-appears-hugely-deformed.html

Post by Sam Carana.

Extreme weather strikes around the globe - update

As the weather gets more extreme, disaster strikes around the globe. The Guardian reports three people killed as storms continue to batter southern UK. The Vancouver Sun reports that a U.S. Northeast snowstorm kills 25. And the Sacramento Bee reports Six dead and 1,000 injured in fresh Japan snow storm.

What is the story behind these extreme weather events? The image below tells the story. The Arctic has been much warmer than it used to be, due to numerous feedbacks that accelerate warming in the Arctic. This reduces the temperature differential between the Arctic and lower latitudes, which changes the Jet Stream and Polar Vortex, in turn making the weather at many places ever more extreme.

 earlier forecasts by cci-reanalyzer.org

Above image illustrates the situation, showing an Arctic Ocean that is warmer than the higher latitudes of the Asian and North American continents.

Arctic sea ice has meanwhile reached record lows, as illustrated by the image below.

The situation can be expected to get even worse. The image below shows sea ice extent, as measured by the NSIDC, which is one day ahead compared to above image.

Below, two regular contributors to the Arctic-news blog comment on the situation.

Paul Beckwith: Paul Beckwith with sign (arrows highlighted by Sam Carana, from earlier post) In the video below, Paul Beckwith discusses the above sign and the situation in general.

Dr. Malcolm Light, Earth Scientist, comments: The volume of water transported by Gulf Stream off the east coast of the United States has increased by three times since the 1940s due to a massive increase in wind drag. This increase in the south westerly wind drag is a result of the continuously increasing pressure difference set up between the continental air mass over North America, heated by fossil - fuel generated carbon dioxide, and the marine air of the Atlantic. The increased energy entering the Gulf Stream as heat and its associated winds and storm systems are what are now pummeling Great Britain and Europe. This heat is also transported further north by branches of the Gulf Stream into the Arctic Ocean, where it is destabilizing the subsea methane hydrates, releasing increasing volumes of methane into the Arctic atmosphere and causing temperature anomalies this last winter of more than 20 degrees Celsius. As a consequence of the extremely high Arctic temperatures and pressures, the normal freezing Arctic air has been displaced into Canada and the United States, causing catastrophic blizzards that have never been seen before. When the floating Arctic ice cap melts towards the end of next year, the Arctic Ocean will then become more aggressively heated by the sun and the northern offshoots of the Gulf Stream. Under these circumstances, the cold Arctic air will be confined over the Greenland ice cap and the Arctic atmosphere will rotate anticlockwise around Greenland, transferring the fast-increasing amounts of its atmospheric methane to Canada and the United States and causing a further increase in the energy of the Gulf Stream. Therefore the United Kingdom and Europe must brace themselves for even more catastrophic weather systems, widespread flooding and massive wind damage from the start of the last quarter of next year.

Below is a comparison of methane readings for the week from February 9 to 16, 2014, compared to the same period in 2013.

The comparison shows that there is a lot of methane over the Arctic Ocean that wasn't there last year. Furthermore, high methane readings show up where currents move the sea ice out of the Arctic Ocean, in areas such as Baffin Bay. This indicates that methane that is released from the seafloor of the Arctic Ocean appears to be moving underneath the ice and entering the atmopshere where the sea ice is fractured or thin enough to allow the methane to pass through.

Also note that more orange areas show up on the southern hemisphere in 2014, indicating that more methane from the northern hemisphere is now spreading south beyond the equator. This in addition to indications that more methane is rising and building up at higher altitudes, as discussed in an earlier post.

As said before, the situation calls for comprehensive and effective action, as discussed at the Climate Plan blog.

Post by Sam Carana.

Extreme weather strikes around the globe

Editorial note: this post has meanwhile been updated as Extreme weather strikes around the globe update.

As the weather gets more extreme, disaster strikes around the globe.

Here's a snapsnot from today's news. In London, the BBC reports, flooded homes along the River Thames are being evacuated and thousands more are at risk. In Japan, reports Reuters, eleven people died, more than a thousand were injured and tens of thousands lost power when the worst snowstorm in decades hit Tokyo and areas around the Japanese capital before heading north to blanket the tsunami-hit Pacific coast. Many countries in the Middle East were hit by snow. The BBC reports that heavy snow in northern Iran has left around 480,000 homes without power and some towns and villages cut off.

What is causing these extreme weather events? The image below tells the story. While at times it has been cold at many places around the world, when averaged over the past 30 days, temperatures around the globe have actually been several degrees higher than they used to be. The Arctic has been hit hardest, with anomalies as high as 21°C over this 30 day period. This affects the Jet Stream and Polar Vortex, which in turn is making the weather ever more extreme.

The situation is further illustrated by the cci-reanalyzer.org forecasts below.

And while the sea ice didn't look too bad at the start of the year, growth has meanwhile stopped, as illustrated by the image below.

Added below are two videos by Paul Beckwith, further discussing the situation.

Editor's note: Reanalysis of temperature anomaly Jan 12 - Feb 10, 2014.

Meanwhile, I've added another image (above), created with NOAA's reanalysis, which compares temperatures to a larger dataset, and the colors look a lot different, so NOAA may indeed have mixed the colors up somewhat in the initial image, as Albert suggested at the Facebook discussion (click on image below).

Anyway, the point made in the post remains, i.e. that as global warming continues, warming in the Arctic accelerates more rapidly than at lower latitudes, which weakens the polar vortex and jet stream in a self-reinforcing feedback that causes the Arctic to warm up even further compared with lower latitudes.

As said, the situation calls for comprehensive and effective action, as discussed at the Climate Plan blog.

Post by Sam Carana.

As continental U.S. freezes, Alaska gets record high temperatures

While much of the continental United States endured several cold snaps in January 2014, record-breaking warmth gripped Alaska. Spring-like conditions set rivers rising and avalanches tumbling. NASA Eartobservatory illustrates the above words with the two images below.

Above map depicts land surface temperature anomalies in Alaska for January 23–30, 2014. Based on data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite, the map shows how 2014 temperatures compared to the 2001–2010 average for the same week. Areas with warmer than average temperatures are shown in red; near-normal temperatures are white; and areas that were cooler than the base period are blue. Gray indicates oceans or areas where clouds blocked the satellite from collecting usable data.

A persistent ridge of high pressure off the Pacific Coast fueled the warm spell, shunting warm air and rainstorms to Alaska instead of California, where they normally end up. The last half of January was one of the warmest winter periods in Alaska’s history, with temperatures as much as 40°F (22°C) above normal on some days in the central and western portions of the state, according to Weather Underground’s Christopher Bart. The all-time warmest January temperature ever observed in Alaska was tied on January 27 when the temperature peaked at 62°F (16.7°C) at Port Alsworth. Numerous other locations—including Nome, Denali Park Headquarters, Palmer, Homer, Alyseka, Seward, Talkeetna, and Kotzebue—all set January records.

The combination of heat and rain has caused Alaska’s rivers to swell and brighten with sediment, creating satellite views reminiscent of spring and summer runoff. On January 25, 2014, the Aqua satellite collected this image of sediment flowing into the Gulf of Alaska from numerous rivers along the state’s southeastern coast.

All of the heat, moisture, and melting snow has elevated the risk of avalanches. A series of extremely large avalanches in late January sent snow and debris crashing onto the Richardson Highway, blocking the road and cutting the port town of Valdez off from highway access. The avalanches dumped a mound of snow 100 feet (30 meters) tall and up to 1,500 feet (460 meters) long on the highway.

Below are two videos with forecasts for the period from February 4, 2014, to February 11, 2014. The top video shows temperature forecasts and the bottom video shows temperature anomaly forecasts.

Warmer temperatures over the Arctic have resulted in a slowdown of sea ice are growth, as illustrated by the image below (yellow line top left shows 2014 values).

Related posts

- Forecast: America to be hit by temperatures as low as minus 40 degrees
http://arctic-news.blogspot.com/2014/01/forecast-america-to-be-hit-by-temperatures-as-low-as-minus-40-degrees.html

- The Biggest Story of 2013
http://arctic-news.blogspot.com/2013/12/the-biggest-story-of-2013.html

- Polar jet stream appears hugely deformed
http://arctic-news.blogspot.com/2012/12/polar-jet-stream-appears-hugely-deformed.html

Post by Sam Carana.

Forecast: America to be hit by temperatures as low as minus 40 degrees

The image on the right shows that large parts of North America, the Arctic Ocean and Siberia are experiencing low temperatures.

What many people may not realize is that temperatures in the Arctic are actually a lot higher than they used to be around this time of year.

Temperatures in the Arctic have risen due to feedbacks as described in the post The Biggest Story of 2013.

As a result, temperature anomalies above 20 degrees Celsius now feature in the Arctic. As the image on the right illustrates, the once-common temperature difference between the Arctic and lower latitudes has been shattered, and this is weakening the Jet Stream and the Polar Vortex, in turn making it easier for cold air to flow down to lower latitudes and for warmer air to enter the Arctic, as described in posts at this blog for years, e.g. this post.

This is illustrated by the image below, showing that the Arctic is hit by an overall temperature anomaly of 6.55 degrees Celsius, while some areas in the Arctic feature anomalies above 20 degrees Celsius.

Forecasts show that on February 2nd, 2014, 1200 UTC, the Arctic will be hit by a temperature anomaly of 7.85 degrees Celsius, while on February 6th, 2014, 1200 UTC, the U.S. will be hit by temperatures as low as -40 degrees, as illustrated by the image below.

The video below shows temperature forecasts from February 1to February 8, 2014.

The video below shows temperatire anomalies from February 2 to February 9, 2014.

Meanwhile, the Gulf Stream keeps pushing warm water into the Arctic Ocean, as illustrated by the image below.

Click on image to enlarge - view updated animation at earth.nullschool.net 

The image below shows how high sea surface temperature anomalies stretch out from the point where the Gulf Stream travels at high speeds, off the coast of North America, all the way into the Arctic Ocean.

This has already resulted in methane eruptions from the seafloor of the Arctic Ocean that started several months ago and are continuing to date - ominous signs of more to come. The image below, which compares peak methane levels at two altitudes between January 2013 and January 2014, suggests that January 2014 peak levels have increased strongly, compared to January 2013 peak levels. Furthermore, that the rise in average peak readings has been most dramatic at the higher altitude.

This suggests that huge quantities of methane have indeed been released from hydrates under the Arctic ocean, and that much of the methane is rising and building up at higher altitudes. The increasing appearance of noctilucent clouds further confirms indications that methane concentrations are rising at higher altitudes.

Of course, the above analysis uses a limited dataset, but if verified by further analysis, it would confirm a dramatic rise in the presence of methane in the atmosphere due to releases from hydrates. Moreover, it would confirm the immensity of threat that releases from the Arctic Ocean will escalate and trigger runaway warming, as high methane concentrations over the Arctic are contributing to the anomalously high temperatures there. The risk that this will eventuate is unacceptable, which calls for comprehensive and effective action such as discussed at the ClimatePlan blog.

Post by Sam Carana.

Changes to Polar Vortex affect mile-deep ocean circulation patterns

Sept. 23, 2012 – A University of Utah study suggests something amazing: Periodic changes in winds 15 to 30 miles high in the stratosphere influence the seas by striking a vulnerable “Achilles heel” in the North Atlantic and changing mile-deep ocean circulation patterns, which in turn affect Earth’s climate.

“We found evidence that what happens in the stratosphere matters for the ocean circulation and therefore for climate,” says Thomas Reichler, senior author of the study published online Sunday, Sept. 23 in the journal Nature Geoscience.

Simplified artist’s conception showing how changes in polar vortex winds high in the stratosphere can influence the North Atlantic to cause changes in the global conveyor belt of ocean circulation.  Credit: Thomas Reichler, University of Utah.

Scientists already knew that events in the stratosphere, 6 miles to 30 miles above Earth, affect what happens below in the troposphere, the part of the atmosphere from Earth’s surface up to 6 miles or about 32,800 feet. Weather occurs in the troposphere.

Researchers also knew that global circulation patterns in the oceans – patterns caused mostly by variations in water temperature and saltiness – affect global climate.

“It is not new that the stratosphere impacts the troposphere,” says Reichler, an associate professor of atmospheric sciences at the University of Utah. “It also is not new that the troposphere impacts the ocean. But now we actually demonstrated an entire link between the stratosphere, the troposphere and the ocean.”

Funded by the University of Utah, Reichler conducted the study with University of Utah atmospheric sciences doctoral student Junsu Kim, and with atmospheric scientist Elisa Manzini and oceanographer Jürgen Kröger, both with the Max Planck Institute for Meteorology in Hamburg, Germany.

Stratospheric Winds and Sea Circulation Show Similar Rhythms

Reichler and colleagues used weather observations and 4,000 years worth of supercomputer simulations of weather to show a surprising association between decade-scale, periodic changes in stratospheric wind patterns known as the polar vortex, and similar rhythmic changes in deep-sea circulation patterns. The changes are:

– “Stratospheric sudden warming” events occur when temperatures rise and 80-mph “polar vortex” winds encircling the Artic suddenly weaken or even change direction. These winds extend from 15 miles elevation in the stratosphere up beyond the top of the stratosphere at 30 miles. The changes last for up to 60 days, allowing time for their effects to propagate down through the atmosphere to the ocean.

– Changes in the speed of the Atlantic circulation pattern – known as Atlantic Meridional Overturning Circulation – that influences the world’s oceans because it acts like a conveyor belt moving water around the planet.

Sometimes, both events happen several years in a row in one decade, and then none occur in the next decade. So incorporating this decade-scale effect of the stratosphere on the sea into supercomputer climate simulations or “models” is important in forecasting decade-to-decade climate changes that are distinct from global warming, Reichler says.

“If we as humans modify the stratosphere, it may – through the chain of events we demonstrate in this study – also impact the ocean circulation,” he says. “Good examples of how we modify the stratosphere are the ozone hole and also fossil-fuel burning that adds carbon dioxide to the stratosphere. These changes to the stratosphere can alter the ocean, and any change to the ocean is extremely important to global climate.”

A Vulnerable Soft Spot in the North Atlantic

“The North Atlantic is particularly important for global ocean circulation, and therefore for climate worldwide,” Reichler says. “In a region south of Greenland, which is called the downwelling region, water can get cold and salty enough – and thus dense enough – so the water starts sinking.”

It is Earth’s most important region of seawater downwelling, he adds. That sinking of cold, salty water “drives the three-dimensional oceanic conveyor belt circulation. What happens in the Atlantic also affects the other oceans.”

Reichler continues: “This area where downwelling occurs is quite susceptible to cooling or warming from the troposphere. If the water is close to becoming heavy enough to sink, then even small additional amounts of heating or cooling from the atmosphere may be imported to the ocean and either trigger downwelling events or delay them.”

Because of that sensitivity, Reichler calls the sea south of Greenland “the Achilles heel of the North Atlantic.”

From Stratosphere to the Sea

In winter, the stratospheric Arctic polar vortex whirls counterclockwise around the North Pole, with the strongest, 80-mph winds at about 60 degrees north latitude. They are stronger than jet stream winds, which are less than 70 mph in the troposphere below. But every two years on average, the stratospheric air suddenly is disrupted and the vortex gets warmer and weaker, and sometimes even shifts direction to clockwise.

“These are catastrophic rearrangements of circulation in the stratosphere,” and the weaker or reversed polar vortex persists up to two months, Reichler says. “Breakdown of the polar vortex can affect circulation in the troposphere all the way down to the surface.”

Reichler’s study ventured into new territory by asking if changes in stratospheric polar vortex winds impart heat or cold to the sea, and how that affects the sea.

It already was known that that these stratospheric wind changes affect the North Atlantic Oscillation – a pattern of low atmospheric pressure centered over Greenland and high pressure over the Azores to the south. The pattern can reverse or oscillate.

Because the oscillating pressure patterns are located above the ocean downwelling area near Greenland, the question is whether that pattern affects the downwelling and, in turn, the global oceanic circulation conveyor belt.

The study’s computer simulations show a decadal on-off pattern of correlated changes in the polar vortex, atmospheric pressure oscillations over the North Atlantic and changes in sea circulation more than one mile beneath the waves. Observations are consistent with the pattern revealed in computer simulations.

Observations and Simulations of the Stratosphere-to-Sea Link

In the 1980s and 2000s, a series of stratospheric sudden warming events weakened polar vortex winds. During the 1990s, the polar vortex remained strong.

Reichler and colleagues used published worldwide ocean observations from a dozen research groups to reconstruct behavior of the conveyor belt ocean circulation during the same 30-year period.

“The weakening and strengthening of the stratospheric circulation seems to correspond with changes in ocean circulation in the North Atlantic,” Reichler says.

To reduce uncertainties about the observations, the researchers used computers to simulate 4,000 years worth of atmosphere and ocean circulation.

“The computer model showed that when we have a series of these polar vortex changes, the ocean circulation is susceptible to those stratospheric events,” Reichler says.

To further verify the findings, the researchers combined 18 atmosphere and ocean models into one big simulation, and “we see very similar outcomes.”

The study suggests there is “a significant stratospheric impact on the ocean,” the researchers write. “Recurring stratospheric vortex events create long-lived perturbations at the ocean surface, which penetrate into the deeper ocean and trigger multidecadal variability in its circulation. This leads to the remarkable fact that signals that emanate from the stratosphere cross the entire atmosphere-ocean system.”

References:

Stratosphere Targets Deep Sea to Shape Climate - North Atlantic 'Achilles Heel' lets Upper Atmosphere Affect the Abyss - University of Utah News Center.
http://unews.utah.edu/news_releases/stratosphere-targets-deep-sea-to-shape-climate/

A stratospheric connection to Atlantic climate variability

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo1586.html

Opening further Doorways to Doom

Until now, the Arctic has been protected from overheating in a number of ways.   Negative Arctic Oscillation conditions are associated with higher pressure in the Arctic and a weakened polar vortex (yellow arrows). A weakened jet stream (black arrows) is   characterized by larger-amplitude meanders in its trajectory and a reduction in the wave speed of those meanders. Credit: Cornell University, C. Greene & B. Monger, 2012 Snow and ice that grows in winter will act as a buffer when temperatures rise in summer. A bright snow and ice cover will reflect most sunlight back into space. Furthermore, a lot of the sunlight that isn't reflected will be consumed by the process of turning snow and ice into water, which occurs while temperatures remain at the melting point of 0°C (32°F, 273.15 K). The Arctic is further protected from overheating by the polar vortex and jet stream, which act to keep cold air in the Arctic and keep warm air out. However, accelerated warming in the Arctic is now causing the polar vortex and jet stream to weaken.  Accelerated warming in the Arctic alters the polar jet stream by slowing its speed and by increasing its waviness. Larger swings in the jet stream allow frigid air from the Arctic to plunge farther south, as well as warm, moist tropical air to penetrate northward, explains Jennifer Francis, research professor at the Institute of Marine and Coastal Sciences at Rutgers University. The polar jet stream can travel at speeds greater than 100 mph. Here, the fastest winds are colored red;  slower winds are blue. View animated version here. Credit: NASA/Goddard Space Flight Center What is described above can be regarded as an "open doors feedback". It's like leaving the doors open when it's cold inside and hot outside. Accelerated warming in the Arctic comes with many such feedbacks, e.g. higher temperatures and more open water in the Arctic can also be expected to increase the danger that storms will batter the sea ice with greater ferocity. This is depicted in the image below. In many ways, this is opening the doorways to doom. The biggest danger is that temperature rises will cause Arctic methane stores to weaken, resulting in huge amounts of methane to be released, triggering warming that could escalate into runaway global warming.   The image below shows the sea surface temperature anomaly for August 27, 2012, by the National Oceanic and Atmospheric Administration (NOAA). Rising temperatures in the Arctic threaten to trigger methane releases, as shown on the poster below. You can order printed copies of the poster.  The poster is also part of the presentation below:

 

Why act now, and how from SamCarana