The storm had an unusually low central pressure area. “It’s an uncommon event, especially because it’s occurring in the summer,” said Paul Newman, chief scientist for atmospheric sciences at NASA’s Goddard Space Flight Center. “Polar lows are more usual in the winter.” Newman estimated that there have only been about eight storms of similar strength during the month of August over the past 34 years of satellite records.
“It seems that this storm has detached a large chunk of ice from the main sea ice pack,” said Claire Parkinson, a climate scientist at NASA Goddard who studies ice. “This could lead to a more serious decay of the summertime ice cover than would have been the case otherwise, even perhaps leading to a new Arctic sea ice minimum.”
Arctic storms can have a large impact on sea ice, causing it to melt rapidly. Storms can tear off large swaths of ice and push them to warmer sites; they can churn the ice and make it slushier; or they can pull warmer waters up from the depths of the Arctic Ocean. “Decades ago, a storm of the same magnitude would have been less likely to have as large an impact on the sea ice because the ice cover was thicker and more expansive,” Parkinson added.
- Aqua - MODIS
The Visible Infrared Imaging Radiometer Suite (VIIRS) on Suomi NPP captured this view of the storm on August 7, 2012. The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard Aqua captured a natural-color image of the storm as well.
Arctic cyclones are more common during the summer than winter; however, summer cyclones tend to be weaker than the storms that batter the region during the winter. This cyclone’s central sea level pressure reached about 964 millibars on August 6, 2012—a number more typical of a winter cyclone. That pressure puts it within the lowest 3 percent of all minimum daily sea level pressures recorded north of 70 degrees latitude, noted Stephen Vavrus, an atmospheric scientist based at the University of Wisconsin.
The number of cyclones affecting the Arctic appears to be increasing. According to a study of long-term Arctic cyclone trends authored by a team led by John Walsh and Xiangdong Zhang of the University of Alaska Fairbanks, the number and intensity of Arctic cyclones has increased during the second half of the twentieth century, particularly during the summer.
The cause of the increase is an open question, but climate change may be affecting Arctic cyclones. One study published in Atmospheric and Oceanic Science Letters, concluded that the total number of exratropical cyclones in the Northern Hemisphere would decline as the climate changed, but that the Arctic Ocean and adjacent areas would see slightly more and stronger summer storms.
One way climate change may affect Arctic cyclones is by changing the sea ice and ocean temperature. Climate change has caused sea ice to retreat markedly in recent decades and has also warmed Arctic Ocean temperatures. Such changes may be providing more energy and moisture to support cyclone development and persistence, Zhang explained.
However, scientists who study extratropical storms emphasize that pinning down how exactly climate change is affecting the size, frequency, or tracks of Arctic storms remains an important but unresolved question. “This past week’s storm was exceptional, and the occurrence of Arctic storms of extreme intensity is a topic deserving closer investigation,” noted Walsh. “With reduced ice cover and warmer sea surfaces, the occurrence of more intense storms is certainly a plausible scenario. The limitation at present is the small sample size of exceptional events, but that may change in the future.”
- Orsolini, Yvan. (2008, January 16). Projected Changes in Eurasian and Arctic Cyclones Under Global Warming in the Bergen Climate Model. Atmospheric and Oceanic Science Letters.
- Zhang, X. (2004, January 2004). Climatology and Interannual Variability of Arctic Cyclone Activity: 1948-2002. Journal of Climate.
- Suomi NPP - VIIRS
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