So although most of us are finally basking in some warm summer weather, we have all come to associate British summer time with rain and rather mild weather , with only a few warm, sunny weeks dotted around. New research conduced by climate change experts at the University of Sheffield have finally given us a link to why rainy conditions are becoming the traditional British summer weather. And we can blame it all on Greenland!
A team led by Professor Edward Hanna have identified changes in weather systems over Greenland that have changed in recent decades, leading to the extreme weather witnessed over Europe. Greenland, as one of the fastest warming regions in the world has become a focus for much scientific research in recent years. Over the last two decades, an increase of up to 10 °C during the winter months, has been recorded on the west coast of the island.
The Greenland Blocking Index (GBI) measures the occurrence and strength of atmospheric high pressure systems. These systems often remain stationary, bringing with them a period of stable, calm weather, blocking storm systems moving into the region. Professor Hanna’s team studied the GBI between 1851 and 2015, discovering an increasing occurrence of the ‘blocking’systems throughout the year, since the 1980’s. This increase can be linked to the significant warming in Greenland and the wider Arctic region and the affects are compounded to the rest of the world. The strongest ‘blocking’ systems were observed in the summer and led to a move in northward-meandering branch of the atmospheric jet stream, pumping warm air into the north of the Greenland region. These changes in Greenland also affect worldwide weather systems downstream of Greenland, including the UK’s.
Global wind patterns and the jet streams
These ‘blocking’ systems have also become more variable in recent years, leading to increasing destabilisation of the atmospheric weather systems. The variability seen in late autumn/ early winter, can in part, be linked to the dramatic declines in Arctic sea ice. Professor Hanna explained ‘Sea ice coverage throughout the Arctic has significantly decreased 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 over Greenland are adding to the change in polar climate’.
Melting sea ice in the Arctic. (picture: albanydailstar.com)
Hanna, E., Cropper, T.E., Hall, R.J., Cappelon, J. 2016. Greenland Blocking Index 1851-2015: A Regional Climate Change Signal. 10.1002/joc4673
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