A warm Arctic, a meandering jet stream, Europe, eastern US cold, wet and stormy. What do all these things have in common? According to Jennifer Francis, loss of Arctic sea ice.
“The sea ice is going rapidly. It’s 80% less than it was just 30 years ago. There has been a dramatic loss. This is a symptom of global warming and it contributes to enhanced warming of the Arctic,” said Jennifer Francis, research professor with the Rutgers Institute of Coastal and Marine Science in an interview with the Guardian yesterday.
Francis noted that persistent cold weather in the US and Europe could be attributed to the polar jet stream forming abnormally large, persistent ridges and troughs over the same regions for long periods of time. These blocking patterns are events that Francis attributes to loss of sea ice in the Arctic.
“This is what is affecting the jet stream and leading to the extreme weather we are seeing in mid-latitudes,” Francis said in the Guardian’s report. “It allows the cold air from the Arctic to plunge much further south. The pattern can be slow to change because the [southern] wave of the jet stream is getting bigger. It’s now at a near record position, so whatever weather you have now is going to stick around,” she said.
Weather Stuck in Extreme
For much of the 2013 winter and early spring, temperature patterns in the Northern Hemisphere have been stuck. The eastern and northern US remain abnormally cold. The west, warm. Europe, cold. And central east Asia, warm. Notably, the Arctic has also been much warmer than usual. As a result, the global temperature map has looked much the same during this time period.
(Image source: NOAA Earth Systems)
In the above image, we can see that most of the globe shows average or above average temperatures. But extreme cold has invaded the eastern US and Europe. As Francis notes, these extremes are caused by persistent waves in the jet stream called blocking patterns.
Last year, the US was stuck on the other side of this kind blocking pattern — the hot, drier side. Then, we saw conditions that led to a record 55 year drought. In the fall, a powerful blocking pattern helped to spawn the devastating hybrid superstorm Sandy. Now, the climate has switched to the opposite of the extremes we saw last year. Though February was the 9th hottest globally, weather remained stuck in a cold, wet pattern in Europe and the eastern US. The result was unprecedented winter storms for much of these regions.
It is not that we haven’t been warned of the increasing weather extremes sometimes referred to as global weirding. In fact, many scientists around the globe raised a loud alarm last year and continue to do so. Here is a statement from NOAA scientists who warned about the increasing tendency of weather patterns to switch from one extreme to the next in a recent paper:
“With more solar energy going into the Arctic Ocean because of lost ice, there is reason to expect more extreme weather events, such as heavy snowfall, heat waves, and flooding in North America and Europe.”
Extreme variation, in other words, now represents a new normal.
Former UK chief science adviser Sir John Beddingham notes that “The [current] variation we are seeing in temperature or rainfall is double the rate of the average. That suggests that we are going to have more droughts, we are going to have more floods, we are going to have more sea surges and we are going to have more storms. These are the sort of changes that are going to affect us in quite a short timescale.”
Extreme variations in climate were also warned of in a 2012 study conducted by James Hansen of NASA’s GISS division. The study paper noted that “Cool anomalies as extreme as -2σ still occur, because the anomaly distribution has broadened as well as moved to the right. In other words, our climate now encompasses greater extremes.” The paper found that extreme temperature events were ten times more likely than during the period of 1950-1981.
NASA researchers noted extreme events also took place during times of persistent atmospheric blocking patterns — yet another validation to work done by Francis and others.
What to Expect?
Unfortunately, we can continue to expect extreme weather events as Arctic sea ice declines. Sea ice volume is currently near record lows. Extent and area are about 6th lowest for the winter of 2013. And thick, multiyear ice is at its lowest level ever. Large sea ice cracking events occurring 50 days ahead of schedule are just one more sign that sea ice may well be on its way to another record melt come 2013.
Since scientists are increasingly drawing a link between sea ice erosion and extreme weather events driven by blocking patterns, and since extreme heating events are becoming more common, we can expect weather to continue to worsen as sea ice erodes and global average temperatures inch ever higher.