by Joseph Morris
I was sitting in my comfy recliner staring out the patio door at the pile of snow from the November snowstorm. Lake effect snow requires an unfrozen Lake Erie. I wondered how climate change was impacting Lake Erie ice coverage. So, I did some research and found this chart on the GLISA
(Great Lakes Integrated Sciences and Assessment) website. GLISA is a joint effort of the US NOAA (National Oceanic and Atmospheric Administration) and the University of Michigan. The GLISA chart shows the maximum ice coverage, i.e., how much of Lake Erie is covered with ice, by year since the 1970s. The higher the blue bars, the more of the lake is covered with ice. The frequency of low ice coverage years (the white spaces) has been increasing in the recent decades. This pattern goes along with the general expectations about the impact of the warming associated with climate change. But the GLISA website also included the following statement: “Years with strong El Niño Southern Oscillation (ENSO) events contribute to lower maximum ice coverage, while years with polar vortex intrusions (La Niña) generally lead to higher maximum ice coverage.” Just what does this mean?
The ENSO Cycle is a recurring climate pattern resulting from changes in Pacific water temperature. El Niño and La Niña are the two extremes of the ENSO cycle. El Niño occurs when the waters in the central and eastern Pacific are warmer than normal, and the trade winds slow or even change direction. With El Niño (rightmost illustration), the Pacific Jet Stream (the red arrow) flows over the US, keeping the Polar Jet Stream (blue arrow) north in Canada. During La Niña (left illustration), the Pacific waters are colder than normal, weakening the Pacific Jet Stream to allow the Polar Jet Stream to flow further south, bringing colder air into the Northeast and Upper Midwest. In general, La Niña winters in the northeastern US are colder with more total snowfall, while El Niño winters are milder with less snow.
However, for Buffalo, milder winters also means less ice coverage and warmer waters in Lake Erie (and Lake Ontario). So, while El Niño leads to warmer, drier winters, the snowstorms that occur will likely be lake effect snowstorms. It also seems that due to climate change, El Niño periods are growing longer, which may mean more consecutive winters with El Niño conditions. The ENSO cycle is not the only climate cycle that impacts our weather, but there seems to be a correlation between ice coverage and ENSO. So, it probably means we can look forward to more lake effect snows that may be more intense. To paraphrase Richard Dreyfuss in Jaws, “We may need a bigger snow blower.”