Unusually cold air events over Greenland have occurred five times since 2007; the same as the previous 156 years, say scientists. A study found this cold air, or high air pressure, could be linked to climate change, and is potentially the cause of extreme weather in the UK.
Previous studies have found high air pressure over Greenland can 'block' the path of a jet stream, a flow of air current, high in the atmosphere. Acting like stones in a stream, the high pressure forces the jet stream toward mainland Europe. It drags the cold Arctic air along with it, meaning Europe experiences colder temperatures.
Air pressure over Greenland had been recorded by scientists since 1948. Researchers at the University of Sheffield wanted to compare air pressure from recent years to before humans began releasing greenhouse gases into the atmosphere. This could provide evidence that climate change is having an impact on Greenland's air pressure.
The researchers reconstructed air pressure over Greenland back to 1851, by using past observational data. They then compared how the air pressure has changed until 2015. Their results are published in the International Journal of Climatology.
"We found the air pressure [over Greenland] has been increasing since the 1980s," Edward Hanna, leader of the research, told IBTimes UK. "When we looked at the years with the highest air pressures since 1851, we found 2007, 2008, 2009, 2012 and 2015 were all in the top 10."
What causes the high air pressure?
The researchers say the high air pressure is usually a result of strong Arctic warming. As sea ice coverage decreases, the region continues to warm. "Sea-ice coverage throughout the Arctic has significantly reduced in recent years, which we already know is having an amplifying effect on warming in the region. What this study now tells us is that changes in stationary high pressure over Greenland are adding to the change in polar climate," said Hanna.
Hanna says the high air pressure over Greenland in recent years could be responsible for extreme weather events seen across the UK. As the air pressure forces the jet stream toward the UK, it pulls along the cold Arctic air too. He said: "The unusually wet weather seen in the UK in the summers of 2007 and 2012, for instance, is linked to these stationary high pressure systems over Greenland."
The scientists now plan to investigate the atmospheric jet stream above Greenland, to find how it may change with climate change. Hanna says they will have to find a way to reconstruct trends from more data sets to do that, just like they did for this study.