A new study suggests the diminishing ice cover in the arctic might be playing an important role in the weather patterns Wisconsin experiences.
The ice cover in the arctic has been rapidly shrinking over the past few years. By September of this year it was at a record low, down an area about the size of Texas since the last record set in 2007. This loss of arctic ice could affect climate in the mid-latitudes, according to Steve Vavrus, a climate expert and senior scientist in the Nelson Institute Center for Climatic Research at the University of Wisconsin-Madison.
The mid-latitudes are the temperate regions of the earth, falling between the tropics and the Arctic and Antarctic regions. The warming in the arctic could slow the jet stream that normally steers weather from west to east in the mid-latitudes, causing more persistent weather. It could also cause more extreme weather, as the waves in the atmosphere become stretched.
“The combination of those two, the waviness promoting more extreme weather and the greater persistence making those weather events last longer, that combination will become noticeable as heat waves, droughts, floods and cold snaps,” Vavrus said.
In a paper published in the Journal of Geophysical Research Letters last spring, Vavrus and co-author Jennifer Francis of Rutgers University speculate that based on current and future trends, the warming in the arctic could cause a change in mid-latitude weather patterns in favor of more frequent extreme conditions.
Extreme weather has been occurring at a greater frequency in the past several years, according to the National Oceanic and Atmospheric Administration’s U.S. Climate Extremes Index. Although weather trends fluctuate between years, the past several years have seen an increase in overall extreme weather, with 2012 currently setting a record for extreme weather.
Other research has pointed toward global warming producing more extreme weather of certain types, including heavy rainfalls, heat waves and droughts.
The arctic is particularly sensitive to warming. The expansive snow and ice cover reflects sunlight back, absorbing little energy. However as the snow and ice melt, more land and ocean become available to absorb energy. The atmosphere around the arctic is also particularly thin, so there is less area for the heat to spread out over.
The increase in global warming is likely to continue, according to Vavrus. The main cause of the warming relates to greenhouse gases like carbon dioxide, which traps heat in the atmosphere. Industrialization, the burning of fossil fuels and agriculture have all contributed to a dramatic increase in the amount of carbon dioxide in the atmosphere.
“The levels of carbon dioxide in the atmosphere are higher than they have been in at least 800,000 years, we know that from ice core records … We have fundamentally changed the atmosphere composition in just a very short amount of time,” Vavrus said.
Although there is a lot of year-to-year variability in the weather patterns, the upward trend is very apparent in the arctic and is likely to continue in coming years and possibly accelerate.
“Like stopping a freight train, we can’t talk about reversing it until we slow it to a halt. Right now that is the hope, that we will slow down the rate of emissions,” Vavrus said. “In terms of actually reducing the levels of carbon dioxide concentrations in the atmosphere, that is a tall order because we are going so fast in the other direction.”
Wisconsin has experienced some extreme weather this year, including an unusually warm March, a cold snap in April and a drought throughout the summer. Based on Vavrus’ proposal, some may wonder if this increase in instances of extreme weather is related to the loss in arctic ice.
Vavrus’ answer? Maybe. The weather is generally variable, and these events may have occurred regardless of any climate change.
“But the warming climate... changing climate is the backdrop to all of our weather events, Vavrus said. “And the more climate change takes hold the stronger that contribution will be.”