With the single digit high temperatures and the below freezing lows now behind us, let’s see how those bone-chilling temperatures helped with ice coverage on the Great Lakes. As shown in the graphic above, the total ice coverage on the Great Lakes is roughly 66.1%. This time last year the total lake ice coverage was about 42.2%. The roughly 24% difference from 2018 to 2019 can be attributed to the above-average temperatures in December and the rapid turn-around, (i.e., 80 degree Fahrenheit temperature change), that was experienced once the polar vortex impacted the Great Lakes region.
Believe it or not, ice-coverage is vital to the Great Lakes watershed and various ecosystems therein. Ice coverage acts as an evaporation shield to help keep the lake water from being evaporated into the atmosphere. This also reduces the amount of moisture in the atmosphere which helps to provide a source for extra low-level moisture which can often help fuel winter storms. With less ice coverage, this will produce more evaporation which, in turn, will cause more precipitation. As previously mentioned, ice on the Great Lakes acts as an “evaporation seal”—diminishing the amount of moisture being brought up to the atmosphere. The availability of more moisture in the atmosphere is what helps build winter storms, which feed off of moisture from the Great Lakes. The growing percentage of ice also helps with the region’s albedo. Albedo is the ratio of incoming radiation that is absorbed and reflected. Ice and snow, which reflects incoming solar radiation, have a high albedo due to their high reflectivity. Whereas black pavement for instance, has a low albedo to due to its lack of reflectivity and high absorption of solar radiation. In addition to albedo, ice on the Great Lakes helps regulate the ecosystem. Plankton, for instance, rely on ice to protect their populations because when ice forms over their habitat, they become more resilient and protected from warmer temperatures. Harmful algal blooms that occur in Lake Erie every year are regulated by ice because of the bacteria that causes the blooms, are killed off.
A year with low Great Lakes sea ice and a year with high Great Lakes sea ice are polar opposite in comparison. This year for instance, as of right now, we are above the 55% long-term average for lake ice. For more ice data and historical ice data visit GLERL’s website here.
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©2019 Weather Forecaster Alec Kownacki