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Climate change in the Arctic is messing with our weather
Posted on 16 March 2015 by John Abraham
There has been a lot of attention on the influence of rapid warming of the Arctic on weather in the Northern Hemisphere mid-latitudes. Much of the work has focused on changes to the Jetstream amplitudes and association of these changes to ice loss in the Arctic.
We know that the Arctic is heating faster than the planet as a whole. Consequently, there is more energy in the Arctic which can be transmitted to the atmosphere. Much of the excess heat is transferred to the atmosphere in the late fall or early winter. This extra energy is connected to what’s called Arctic geopotential height, which has increased during the same times of the year. As a consequence, the Jetstream might weaken in the cold seasons.
But what about summer? Have these changes been detected then too? Well just recently, a paper was published in that answered this question. The authors, from the Potsdam Institute for Climate Impact Research and from the University of Potsdam reported on three measures of atmospheric dynamics (1) zonal winds, (2) eddy kinetic energy, and (3) amplitude of the fast-moving Rossby waves. Rossby waves are very large waves in the upper atmospheric winds. They are important because of their large influence on weather.
Dr. Dim Coumou. Photograph: Potsdam Institute for Climate Impact Research
The authors found that the summer zonal winds have weakened. The reason for the weakening is that since the Arctic is warming faster than the rest of the planet, the temperature difference between the Arctic and the lower latitudes is getting smaller. It is this temperature difference which maintains the wind speeds. The authors also found that eddy kinetic energy is decreasing.
So what does all this mean? Well two things. First, it means that there are either fewer or less intense summer storms or a combination of both. But secondly, it means that weather patterns can get “stuck”. Storms are excellent at breaking up persistent weather patterns, and bringing cool and moist air from ocean regions to land zones. With fewer storms, “warm weather conditions endure, resulting in buildup of heat and drought.”
The authors looked to the future to inquire about how things would continue to change. They find that continued global warming will increase the risk of heat waves. We all know that the warming temperature will make heat waves more likely. But added to this, “stickiness” of weather patterns will play a big role as well.
Whether it is the heat wave in Europe of 2003, the Russian heat wave of 2010, the heat waves in the USA in 2011 or 2012, or last year’s (and still continuing heat in California), these events have economic and human consequences. It is crucial to understand how our current climate works if we have any hope in predicting what will happen in the future. This study makes a great contribution to putting the puzzle of the Earth’s climate together.
I asked colleague Dr. Stefan Rahmstorf about this work and he said,
Despite the reduction of the arctic ice, there is still an awful lot of it reflecting EM radiation back into space. Even now we see the jet stream weakening and wobbling, presumably due to the slower rotation of the Polar Hadley cell. The PHC is powered in the same way the air coming out of an open fridge is. The air radiates heat into space, the air gets heavy, flows downward and south as it hits the ground. What happens when the Arctic is open water for, say, all of August and half of September. Will this not reverse the Polar Hadley cell and suck climate zones northward. This effect should also be seen in the fall as the land rapidly cools off but the huge store of heat in the ocean is warming the air above it. It would likely be extended as freezing starts and Latent Heat is released. Interesting that if this happens it will be just as the grain crops of the Northern Hemisphere are ripening.
http://mtkass.blogspot.co.nz/2008/07/arctic-melting-no-problem.html
[JH] Link activated.
Arctic sea ice hit its annual peak early this year, and climate scientists say the region's below-average ice conditions made this year's maximum extent the lowest on record.
Every year, Arctic sea ice — ice that forms and floats in Arctic waters — grows during the winter and typically reaches its peak in March. A new report from the National Snow & Ice Data Center (NSIDC), however, reveals this year's Arctic sea ice likely reached its maximum extent earlier than expected, on Feb. 25. At this peak, sea ice covered 5.61 million square miles (14.54 million square kilometers) — the lowest maximum extent since satellite record keeping began in 1979.
The authors of the NSIDC report also found below-average ice conditions everywhere except in two regions of the North Atlantic Ocean: the Labrador Sea and the Davis Strait. [Images of Melt: Earth's Vanishing Ice]
Researchers have seen fluctuations in the date of the sea ice's peak, with it occurring as early as Feb. 24 in 1996 and as late as April 2 in 2010. Still, this year's maximum extent occurred 15 days earlier than the March 12 average calculated from 1981 to 2010.
The Arctic ice cap grows and shrinks with the seasons, and changes in the region's ice cover are largely dictated by variations in sunlight, temperature and weather conditions.
This year's maximum extent was 425,000 square miles (1.10 million square km) below the average from 1981 to 2010 of 6.04 million miles (15.64 million square km). This year's ice cover was also 50,200 square miles (130,000 square km) lower than the previous record low set in 2011.
Ice growth this winter lagged behind last year's progress, partly due to unusual patterns in the jet stream in February that created warm pockets over the Bering Sea and the Sea of Okhotsk, in the western Pacific Ocean, according to the NSIDC.
Yet, officials say a late-season boost in ice growth may still be possible.
"Over the next two to three weeks, periods of increase are still possible," NSIDC scientists wrote in the report. "However, it now appears unlikely that there could be sufficient growth to surpass the extent reached on February 25."
The NSIDC is expected to release a full analysis of this winter's sea-ice conditions in early April.
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