Arctic Sea Ice, Climate Change, and Hurricane Sandy

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President and Senior Scientist Dr. Eric A. Davidson

Perhaps it requires a catastrophe such as Hurricane Sandy for the issue of climate change to finally make it into the news this autumn. While inspecting the flooded subway system in New York City, Governor Cuomo noted that “We have to come to the realization that we are dealing with extreme weather events…this is a new reality for us.”

In the aftermath of Hurricane Sandy, we’ll be hearing much more about whether its intensity and path can be attributed in part to human-induced climate change. There is an intriguing hypothesis that this summer’s record melting of Arctic sea ice may have had a role. This is a relatively new area of research, so we won’t have answers for some time, but this fascinating interconnectedness of the global climate system is eloquently explained by meteorologist Jeff Masters:

“A strong ridge of high pressure parked itself over Greenland beginning on October 20, creating a “blocking ridge” that prevented the normal west-to-east flow of winds over Eastern North America. Think of the blocking ridge like a big truck parked over Greenland. Storms approaching from the west (like the fall low pressure system that moved across the U.S. from California to Pennsylvania last week) or from the south (Hurricane Sandy) were blocked from heading to the northeast. Caught in the equivalent of an atmospheric traffic jam, the two storms collided over the Northeast U.S., combined into one, and are now waiting for the truck parked over Greenland to move.  …  As I discussed in an April post, Arctic sea ice loss tied to unusual jet stream patterns, three studies published in the past year have found that the jet stream has been getting stuck in unusually strong blocking patterns in recent years. These studies found that the recent record decline in Arctic sea ice could be responsible, since this heats up the pole, altering the Equator-to-pole temperature difference, forcing the jet stream to slow down, meander, and get stuck in large loops. The 2012 Arctic sea ice melt season was extreme, with sea ice extent hitting a record low. Could sea ice loss have contributed to the blocking ridge that steered Sandy into New Jersey? It is possible, but we will need much more research on the subject before we make such a link, as the studies of sea ice loss on jet stream patterns are so new.”

What if the sea ice had been more extensive, as it was back in the 1980s and earlier? Would the “blocking” effect noted by Masters not been present and the storm have gone out to sea instead of hanging a left at the New Jersey turnpike? We cannot know for sure, but we do know that human-induced warming is the cause of huge changes now underway in the Arctic, and that the Arctic clearly affects weather where we live. On top of that, the ocean water was 5 degrees Fahrenheit warmer this October than normal, also partially the result of climate change, which provided a source of energy for the storm to intensify and persist. The sea level in the eastern US is also about 10 inches higher than in the early 20th century, due mostly to expansion of ocean water as it gets warmer, making the storm surge that much more powerful. Connecting all the dots – an altered jet stream, a super warm ocean, higher sea levels, and a huge storm – you get an extreme event. Such events have happened in the past, to be sure, but as extreme events become increasingly common, this effect of human disruption of the climate system is becoming known as “the climate on steroids.”

Sandy was an extreme event with loss of life and staggering economic and ecological impacts, as was last summer’s drought in the US Midwest. Climate change is as much about global “weirding” as it is about global warming. Science has identified what needs to be done and that effective actions are plausible, such as moving on from fossil fuel dependence and conserving forests throughout the world. Those steps require courage, political will, and leadership.