Dr. Jason Box on Warm Arctic, Cold Continents
February 6, 2014
As I begin planning for another Greenland expedition to study ice melt, I decided to explore whether the cold eastern North America, was part of what some scientists are calling the Warm Arctic – Cold Continents pattern. Examination of US NCEP NCAR Reanalysis data reveals that YES, the story has an important Arctic climate dimension.
While it’s easy to understand that abnormal summer warmth promotes high melting, winter warming also promotes melting through the loss of snow, ice, and land “cold content”. The higher the ground temperature, the fewer degrees of heating it takes to reach the melting point. Thus, winter warming preconditions the surface for earlier melt onset and more melting overall.
That’s one reason why this January’s Arctic climate concerns me. Greenland temperatures have remained more than 5 degrees C above average after the first week of the year. The snowpack heating the abnormal warmth increase the likelihood of an earlier melt onset and above average Greenland melting this coming summer.
5 day average running temperature anomaly for the region 61 to 82 deg. north latitude and 30-65 deg. west longitude
The Arctic north of 77 degrees north latitude, essentially the Arctic Ocean has also, according to this climate data, been abnormally warm much of January 2014.
Examining the geographic pattern of temperature departure from normal, a.k.a. the temperature anomalies, we see a Warm Arctic – Cold Continents pattern.
The average of the first 33 days of 2014, above average temperatures prevail for Greenland, Baffin Island, Alaska, the Arctic Ocean, the north Atlantic, and the western US with while the eastern North America, northern Europe and Siberia are feeling anomalous cold.
Below is a map representing the period I was in San Francisco for the AGU meeting. I recall skidding on a thin ice layer the morning of 8 Dec walking across Yerba Beuena park. At this time, the whole US was feeling the cold.
The figure below represents the US for the region bounded by 70 to 105 longitude west and 38 to 55 latitude north. Just as impressive as the cold is the abnormal warmth 10-20 Jan. We call this “weather whiplash”.
A climate change connection?
Dr. James Overland and colleagues at NOAA have reported on the Warm Arctic – Cold Continents pattern, occurring December 2009 and 2010. Overland writes:
“In the last five years, we’ve seen the jet stream take on more a wavy shape (left hand map below) instead of the more typical nice oval around the North Pole (right hand map below). This waviness is leading to colder weather down in the eastern U.S. and eastern Asia. Whether this is normal randomness or related to the significant climate changes occurring in the Arctic is not entirely clear, especially when considering individual events, but less sea ice and snow cover in the Arctic and relatively warmer Arctic air temperatures at the end of autumn suggest a more wavy pattern to the jet stream and more variability between the straight and wavy pattern.”
Thanks Peter Sinclair for some text comments.