If you follow science and climate news even a bit closely, you likely have heard that the sea ice in the Arctic region this year has been way below average. It’s so low that even without any sun right now in that region, the ice isn’t expanding. This lower ice coverage itself isn’t new; scientists have noticed for years that the extent and the depth of the ice in the Arctic has been shrinking.
The image below shows the current extent of Arctic ice. Note how low it is this year.
Our reliable data for sea ice only goes back to 1979, which is a relatively short period. However, the trend is clear, and the ice is shrinking. While of course nearly everyone cares about the planet’s health, many of us might not understand how something like Arctic sea ice can affect the weather in New England.
A few years ago, a research paper about the diminishing sea ice appeared in IOP Science. It was written by Jennifer A. Francis from the Institute of Marine and Coastal Sciences at Rutgers University and Stephen J. Vavrus with the Center for Climatic Research at the University of Wisconsin-Madison.
What was interesting about this paper was how it equated the disappearing ice with changes to the jet stream over the mid-latitude part of the planet—where we all live. The research found that the jet stream has become wavier and parts of it have become stuck in places for longer periods of time.
The reason for this change, it was hypothesized, was as the Arctic warms and there is less of a gradient of temperature between the north and the south, the jet stream weakens and moves in a more erratic way.
While the mechanisms are complicated, the basic premise was this: As the ice disappears or thins, heat from the oceans, which had been capped by the ice, is allowed to escape into the atmosphere. This leads to warming, a weaker jet stream, and a jet stream that becomes stuck for longer periods of time in one position. That leads to some areas being exceedingly cold, others warm, some dry and some wet—in other words, more extremes. The more wavy the jet stream, the more extreme the weather. The jet stream typically oscillates with some regularity between a flat state or zonal flow and a wavy one or meridional flow.
Below is one of the images from the research paper. The top panel shows how the thickness of the atmosphere has changed in winter leading to warm temperatures. The middle panel indicates a more amplified jet stream, and the bottom panel uses an index, called the Meridional Circulation Index or MCI, to show how the waviness of the pattern is increasing.
All of this can mean much stormier winters with wide swings in temperatures. This has real impact on not only what we experience, but how we live. Extreme periods of snow and cold followed by dramatic warming can ruin a ski season. Warm weather followed by unusual cold, even a day or two, can damage entire fruit crops, like what happened this spring when the entire peach crop was destroyed. Other flora and fauna can also be hurt when atypical weather occurs.
With the polar night in full swing right now, the ice will hopefully begin to build back in the coming days and weeks. However, the climate is clearly changing, and with it will come more surprises and forecasting challenges ahead.