Climate Fact: Lake Effect Snow on the Upswing
In Brief: Less ice cover on the Great Lakes is contributing to more snow regional lake effect snow.
Over much of the U.S., the 20th century warming trend means less snow and more rain. In most areas, the lack of cold limits snowfall, but this is not true in the Great Lakes region. Here, temperatures are below freezing throughout much of the year and it is lack of moisture that limits snowfall. Much of the moisture that makes up the region’s snow comes from the Great Lakes. As frigid winds from the Canadian interior pass over the relatively warmer waters of the Great Lakes, the cold air picks up moisture which is deposited as snow in areas downwind – a phenomenon termed “lake effect snow.” Two of these downwind areas rank as the third and fourth snowiest areas in the United States – Marquette, Michigan (180 inches annually) and Syracuse, NY (120 inches annually). Once the lakes freeze, however, there is no more exposed water and the moisture source disappears.
- Throughout the region, lake effect snow levels have been increasing, a trend linked to warmer lakes with less ice. Since at least the 1970′s, ice cover on the Great Lakes has been declining.
- Ice cover on Lake Superior, which has been warming by 1.2 degrees Fahrenheit per decade since 1985, used to cover on average 25 percent of the lake area but now covers less than 15 percent. Water temperatures in all of the lakes have been rising. October-April temperatures averaged over all the Lakes rose by one degree Fahrenheit between 1995 and 2000.
- In Syracuse, NY, snowfall levels increased by 50 percent between 1913 and 2000.
(Source: Burnett, AW et al. “Increasing Great Lake-Effect Snowfall during the Twentieth Century: A Regional Response to Global Warming.” Journal of Climate 16 (2003): 3535-3542.)
