Forces behind Superstorm Sandy

Superstorm Sandy hit North America's east coast in a devastating way. This justifies an analysis of the forces behind Sandy and the links with global warming and climate change.

Global warming causes temperatures of oceans and the atmosphere to rise. A warming Gulf Stream fuels hurricanes traveling north along North America's east coast.

More heat translates into more wind; specifically, stronger hurricanes are getting stronger over the years, as illustrated by the inmage on the right from James Elsner et al. (2008).

Additionally, sea levels are rising, especially on the Atlantic coast of North America, which is a hotspot of accelerated sea-level rise, as described in a study by Sallenger et al. (2012).

Generally, global warming will cause more extreme weather events, says James Hansen (2012). This is especially the case for heavy rainfall events, since global warming causes more evaporation of seawater, while warm air can also carry more water. According to Kevin Trenberth (2011), the water holding capacity of air increases by about 7% per 1°C warming, which leads to increased water vapor in the atmosphere. Hence, storms, whether individual thunderstorms, extratropical rain or snow storms, or tropical cyclones, supplied with increased moisture, produce more intense precipitation events. All this leads to a greater hurricane danger; they can be expected to be stronger and wetter, causing flooding and further devastation along the east coast of North America.

The situation in the Arctic is making things even worse. Several studies, such as by Jennifer Francis (2012), by Greene et al. (2012) and by Liu et al. (2012), show that atmospheric circulation is changing as a result of sea ice loss. This circulation change results in more frequent episodes of blocking patterns that lead to increased cold surges over large parts of northern continents. Moreover, sea ice loss results in an increase in atmospheric water vapor content in the Arctic region during late autumn, and this provides enhanced moisture sources.

More open water in the Arctic Ocean results in more warming of the overlying atmosphere. This warming can be expected to change precipitation. An analysis by Julienne Stroeve (2011) shows an autumn increase in cyclone-associated precipitation over the past decade, linked to a shift in atmospheric circulation towards more frequent and more intense cyclones in the Atlantic sector of the Arctic.

The authors added that more research was needed; indeed, the devastation caused by Sandy calls for further analysis. Warming in the Arctic is accelerating at a pace several times that of the rest of the world, as a result of multiple feedbacks as described in the post Diagram of Doom; changing of the jet stream is only one out of multiple feedbacks.

Changes to the jet stream were behind Sandy's path inland. A strong and prolonged high pressure area over Greenland blocked Sandy from going north or east. This also caused it to spread out and to hang around for such a long time.

Big changes are taking place in the Arctic, in terms of sea ice loss, snow line retreat and albedo change in Greenland. Without more effective action on climate change, weather events like this can therefore be expected to hit the east coast of North America more often and with increasing force in future.


References

- The increasing intensity of the strongest tropical cyclones, James Elsner et al. (2008)
http://www.nature.com/nature/journal/v455/n7209/abs/nature07234.html

- Hotspot of accelerated sea-level rise on the Atlantic coast of North America, Asbury Sallenger et al. (2012)
http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1597.html

- Perception of climate change, James Hansen et al. (2012)
http://www.pnas.org/content/109/37/E2415

- Changes in precipitation with climate change, Kevin Trenberth (2011)
http://www.cgd.ucar.edu/cas/Trenberth/trenberth.papers/SSD_Trenberth_2nd_proof.pdf

- Linking Weird Weather to Rapid Warming of the Arctic, Jennifer Francis (March 2012)
http://e360.yale.edu/feature/linking_weird_weather_to_rapid_warming_of_the_arctic/2501/

- An Arctic wild card in the weather, Chuck Greene and Bruce Monger (2012)
http://www.tos.org/oceanography/archive/25-2_greene.html
http://www.news.cornell.edu/stories/June12/arcticWildcard.html

- Impact of declining Arctic sea ice on winter snowfall, Jiping Liu et al. (2012)
http://www.lasg.ac.cn/UpLoadFiles/File/papers/2012/2012-pnas.jiping_liu.pdf

- Attribution of recent changes in autumn cyclone associated precipitation in the Arctic, Julienne Stroeve et al. (2011)
http://onlinelibrary.wiley.com/doi/10.1111/j.1600-0870.2011.00515.x/abstract
http://www.tellusa.net/index.php/tellusa/article/view/15846/17736
poster at:
http://soa.arcus.org/sites/soa.arcus.org/files/sessions/2-3-arctic-change-and-natural-variability/pdf/stroeve.pdf

Related

- Warming Gulf Stream causes methane release
http://arctic-news.blogspot.com/2012/10/warming-gulfstream-causes-methane-release.html

- Diagram of Doom
http://arctic-news.blogspot.com/2012/08/diagram-of-doom.html

- Opening further Doorways to Doom
http://arctic-news.blogspot.com/2012/08/opening-further-doorways-to-doom.html

- Climate Change Sandy Says to US: 'Take That, Idiots!'
http://arctic-news.blogspot.com/2012/10/climate-change-sandy-says-to-us-take-that-idiots.html

- Hurricane Sandy moving inland
http://arctic-news.blogspot.com/2012/10/hurricane-sandy-moving-inland.html

- Big changes in Arctic within years
http://arctic-news.blogspot.com/2012/10/big-changes-in-arctic-within-years.html

Climate Change Sandy Says to US: 'Take That, Idiots!'

By Nathan Currier Superstorm Sandy shows signature of human-induced climate change

Nathan Currier, senior climate advisor for Public Policy Virginia

After the second presidential debate, moderator Candy Crowley said, "Climate change -- I had that question, all you climate change people. We just -- you know, again, we knew that the economy was still the main thing, so you knew you kind of wanted to go with the economy." And the media's been talking about low information voters?

Now, along comes Sandy, who says to Candy, "Okay, then, take that!" See, Sandy doesn't get into debating these things, either. Now, let's see what Sandy's bill ends up being -- anyone taking bets? -- then let's sit down and talk some economy. In fact, there's an idea: Maybe a new American pastime could be organized 'disaster gambling,' with states collecting revenue as everyone bets on the tab for each new upcoming climate change disaster in their respective states?

Perhaps some still take issue with the suggestion that a superstorm like this is caused by our human-engendered climate change. But cigarette packages say things like, "cigarettes cause fatal lung disease." This, of course, is just shorthand, a monumental simplification, because in fact causation in complex systems is always a vastly complicated affair, and tobacco companies spent lots of money blowing smoke in the face of all that complexity: but the likelihood of getting lung disease is so greatly increased by smoking that eventually they gave up and we all agreed to go 'low-info' by just saying cigarettes cause fatal lung disease. As I'll demonstrate, in much the same way, we might as well keep it simple and just say this superstorm is caused by our human-made climate change.

I've been writing on the arctic crisis, and in a recent long list of immediate physical changes from loss of summer arctic sea ice, I listed (as #12) its potential impacts on weather at lower latitudes. It so happens that it is just at this time of year that this has the clearest line of causation, since lots of heat and moisture enter the atmosphere from the open waters that had been ice covered, and latent heat is released in the refreezing process, which progresses rapidly as the arctic cools down right around now. As Jennifer Francis of Rutgers University described in a recent paper: "This warming is clearly observable during autumn in near-surface air temperature anomalies in proximity to the areas of ice loss."

And this in turn becomes very important for large-scale atmospheric circulation. For example, Dr. Francis has used the metaphor of a river going down a steep incline, which runs straight, versus a river that runs along a flat plain, which tends to meander. Likewise the jet stream, since the normal energy gradient between arctic air and that of lower latitudes has become more relaxed in tandem with ice extent drops, is tending to meander more, and hence move more slowly as well. As the Francis paper said, "Previous studies support this idea: weaker zonal-mean, upper-level wind* is associated with increased atmospheric blocking events in the northern hemisphere." [*she means high west-east moving winds]

Let's look back again at this superstorm, and you'll see that important features of what you're about to experience stem from the arctic situation I've been discussing. First, arctic air is coming down to hook up with Sandy from the dip of the jet stream. Francis writes (from personal communication),

"The huge ice loss this summer, and subsequent enhanced warming of the Arctic (see attached figure), may be playing an important role in the evolution of Sandy by enhancing the amplitude of waves in the jet stream."

At the same time, high pressure over Greenland, and the extremely negative state of the North Atlantic Oscillation, is creating a blocking event that is impacting the path of Sandy herself, sending her back west over the U.S. Again, Dr. Francis (in personal communication):

"In this case, the effects could be causing strengthening of the block, elongating the block northward, and/or increasing its duration -- and this block is what's driving Sandy on such an unusual track westward into the mid-Atlantic coast."

Now, let's add to all that the underlying and obvious thing -- that Sandy is only surviving as a hurricane so far north, almost in November, because there are record high sea surface temperatures off the U.S. East coast right now. And while the third storm component, the one coming in from the west, might seem less remarkable, that is also something that generally becomes more probable with global warming, as our atmosphere can hold more water vapor as it warms and the evaporation rate is also increased by the warming. Thus, all major components of this superstorm show the signature of human-induced climate change to varying degrees, and without global warming the chance of the three occurring together like this would have a probability of about zero. So, let's make it simple, and just say climate change caused this storm.

I'm in New York City, just as much in the path of Sandy as so many others are, but come on, you do just have to sit back and love it, appreciate the full irony of it all, with Sandy striking right at those most sensitive loins of our American democracy, threatening to interrupt our sacred electoral process, after that process blocked climate change out, and now an atmospheric blocking pattern, created by that very climate change, pushes Sandy back on us. In a time when climate silence trumps climate science, when the candidates seem terrified to mention the 'C-word,' Candy, I hope you enjoy meeting Sandy. Maybe if the election gets as messed up as 2000, you three can even find time to meet up again, and go over a little issue you couldn't quite find time to fit in before? In my next piece I'll get back back to discussing what we should do right away, and hopefully it will at least be a bit clearer that this is serious business.

[First posted at the Huffington Post; posted with author's permission]

Warming Gulf Stream causes methane release

The Gulf Stream (dashed lines on NOAA image below) pushes warm water north.

Phrampus & Hornbach (2012) have analyzed the stability of methane hydrates along the Carolina rise off the east coast of North America using active-source seismic reflection data, with the goal of characterizing hydrate stability below the Gulf Stream.

The study suggests that ocean warming above the Carolina rise, caused by a warming Gulf Stream, is rapidly destabilizing methane hydrate along a broad swathe of the North American margin.

The area of active hydrate destabilization covers at least 10,000 square kilometres of the United States eastern margin, and occurs in a region prone to kilometre-scale slope failures.

The image on the right shows the study area; the pink area is where methane hydrate is destabilizing owing to recent changes in ocean temperature; the approximate location of the Gulf stream is between the two solid black arrows.

Over the past 5,000 years or so, the western North Atlantic margin has been warming by up to eight degrees Celsius. This is now triggering the destabilization of an estimated 2.5 gigatonnes of methane hydrate. The analysis suggests that we are observing the onset of methane hydrate destabilization along an ~300-km span of the North American margin that will continue for centuries unless the Gulf Stream shifts southward or intermediate ocean temperatures cool several degrees.

If continuing hydrate destabilization triggers slope failure at this site, the amount of methane released could be an order of magnitude greater. Furthermore, recent studies have suggested that similar ocean temperature shifts are taking place elsewhere, notably in the Arctic Ocean; the estimate of 2.5 gigatonnes of destabilizing methane hydrate is therefore likely to represent only a fraction of the methane hydrate currently destabilizing globally.

Without action, global warming looks set to increase temperature anomalies in the oceans. The above image shows the sea surface temperature anomalies that are now present along the east coast of North America.

In many ways, the situation in the Arctic is even more dire than in the Carolina rise. A warming Gulf Stream will push warmer water into the Arctic, which has many areas with extremely shallow seas, giving methane little opportunity to be oxidized in the sea. Furthermore, colder water in the Arctic is less friendly toward microbes that can decompose methane in the water. Once methane does reach the atmosphere, there's little hydroxyl in the Arctic atmosphere to decompose the methane there.

Most importantly, the Arctic contains huge amounts of methane and the Arctic is experiencing huge temperature anomalies in summer, due to albedo changes and further feedbacks. Therefore, the Arctic looks set to experience huge abrupt releases of methane that will add to make the situation in the Arctic worse, in a vicious spiral threatening to escalate into runaway global warming.

References

- Recent changes to the Gulf Stream causing widespread gas hydrate destabilization, Phrampus & Hornbach, Nature 490, 527–530 (25 October 2012) doi:10.1038/nature11528
http://www.nature.com/nature/journal/v490/n7421/full/nature11528.html

Related

- Big changes in Arctic within years
arctic-news.blogspot.com/2012/10/big-changes-in-arctic-within-years.html

- Diagram of Doom
arctic-news.blogspot.com/2012/08/diagram-of-doom.html

- How extreme will it get?
arctic-news.blogspot.com/2012/07/how-extreme-will-it-get.html

- The potential impact of large abrupt release of methane in the Arctic
arcticmethane.blogspot.com/2012/05/potential-impact-of-large-abrupt.html

- Methane in the Arctic
arctic-news.blogspot.com/2012/05/video-and-poster-methane-in-arctic.html

Hurricane Sandy moving inland

Hurricane Sandy is moving inland and its impact is forecast to be felt as far away as in Toronto and Ottawa.

Coastal Watches/Warnings and 5-Day Track Forecast Cone
Hurricane SANDY Advisory #019       11:00 PM EDT Fri October 26, 2012
from:  National Hurricane Center (check link for updates!)

Paul Beckwith,
B.Eng, M.Sc. (Physics),
Ph.D. student (Climatology)
and Part-time Professor,
University of Ottawa 

This prompted Paul Beckwith to make the following comments:

All storms veer to the right in the northern hemisphere due to the spinning of the earth (1 revolution per day). Except when there is a tilted high pressure region northward and it has to go left and there is a massive low pressure region left that sucks it there as well. 

Why the high pressure ridge and massive low pressure? Because the jet stream is wavier and slower, a situation that is happening more and more often, because of massive sea ice decline this summer. Which is due to Arctic amplification feedbacks. Which in turn is due to rising greenhouse gases. Which is due to humans.

The situation is further illustrated by the image below, from ClimateCentral.

An atmospheric "blocking pattern" will push Sandy north, then northwestward, into the Mid-Atlantic or Northeast. Click to enlarge the image.     Credit: Remik Ziemlinski, Climate Central.

In an earlier post, Paul Beckwith described that a very rare cyclone churned up the entire Arctic region for over a week in early August 2012, destroying 20% of the ice area by breaking it into tiny chunks, melting it, or spitting it into the Atlantic. Cold fresh surface water from melted sea ice mixed with warm salty water from a 500 metre depth! Totally unexpected. A few more cyclones with similar intensity could have eliminated the entire remaining ice cover. Thankfully that didn't happen. What did happen was Hurricane Leslie tracked northward and passed over Iceland as a large storm. It barely missed the Arctic this time. Had the storm tracked 500 to 600 kilometres westward, Leslie would have churned up the west coast of Greenland and penetrated directly into the Arctic Ocean basin.

We dodged a bullet, at least this year. This luck will surely run out. What can we do about this? How about getting our politicians to listen to climatologists, for starters.

Below, rainfall forecast from the Hydrometereological Prediction Center of the National Weather Service - check the link for updates! 

Related

- Vanishing Arctic sea ice is rapidly changing global climatearctic-news.blogspot.com/2012/09/vanishing-arctic-sea-ice-is-rapidly-changing-global-climate.html

- Storm enters Arctic region

arctic-news.blogspot.com/2012/09/storm-enters-arctic-region.html

- Diagram of Doom
arctic-news.blogspot.com/2012/08/diagram-of-doom.html

- Huge cyclone batters Arctic sea ice
arctic-news.blogspot.com/2012/08/huge-cyclone-batters-arctic-sea-ice.html