In late February or early March each year, the Great Lakes typically witness their annual peak in ice coverage. However, the year 2024 marked an anomaly as the lakes were notably devoid of ice during this period. Unusually warm winter conditions and above-average surface water temperatures contributed to this phenomenon, resulting in historically low ice cover. Satellite-based measurements, dating back to 1973, have consistently recorded an average winter extent exceeding 40 percent ice coverage. Yet, by late February 2024, the ice cover reached only about one-tenth of this average maximum.The VIIRS (Visible Infrared Imaging Radiometer Suite) sensor aboard the Suomi NPP satellite captured this striking image of the lakes on February 24, 2024, highlighting the significant departure from the norm.
The freezing patterns of the Great Lakes exhibit considerable variability, with instances like 2014 witnessing coverage exceeding 80 percent. Nevertheless, a discernible trend has emerged since 1973, indicating a decline in ice levels. Data from NOAA's Great Lakes Environmental Research Laboratory (GLERL) reveals an approximate 5 percent decrease per decade in annual maximum ice coverage. This downward trajectory is attributed to warmer winter conditions prevalent in the Great Lakes region, fostering more frequent occurrences of years with lower ice extents.
Great Lakes,from 1973 to 2024.
The provided chart illustrates the ice coverage during the 2023–2024 winter season (depicted in red) in comparison to the patterns observed over the past 50 winters. The line distinctly reflects the unusually warm start to the current ice season. Typically, the first cold air masses sweep over the upper Midwest in December, initiating the cooling of lake water—a process known as "priming." However, in December 2023, this priming did not occur, leading to the lowest January ice cover on record in 2024. Subsequently, when an arctic chill enveloped much of the U.S. in mid-January, the ice cover reached its probable season maximum, peaking at approximately 16 percent, only to dissipate as warmer temperatures returned.
Jia Wang, an ice climatologist at GLERL, highlights the significant correlation between air temperatures and ice cover over the Great Lakes. Exploring the intricate relationship further, Wang identifies four patterns of climate variability influencing temperatures in the region. In the current year, a noteworthy alignment occurs, with three out of the four patterns—El Niño, the Atlantic Multidecadal Oscillation, and the Pacific Decadal Oscillation—simultaneously contributing to warming effects on the Great Lakes, further impacting the observed patterns of ice cover.
The absence of ice on the Great Lakes not only renders shorelines and infrastructure more vulnerable to damage from powerful wind and waves but also exposes certain fish species to increased risk during their spawning season, lacking the protective barrier that ice cover typically provides against predators. Moreover, the repercussions extend to water levels, as diminished ice cover may facilitate heightened evaporation. As of late February, however, NOAA reported no significant impact on water levels. The similarity between lake and air temperatures has contributed to keeping evaporation rates low, mitigating potential consequences on water levels at this point in the season.
As the Great Lakes ice season extends through March, NOAA experts suggest the potential for sporadic bursts of arctic air that could induce periods of ice formation. Despite this possibility, these cold air events are anticipated to be transient, and a significant shift in weather patterns would be necessary to reverse the current below-average trend in ice coverage for this season. The NASA Earth Observatory images, credited to Michala Garrison and Lauren Dauphin, utilize VIIRS data from NASA EOSDIS LANCE, GIBS/Worldview, along with lake ice data from NOAA's Great Lakes Environmental Research Laboratory. The story is credited to Lindsey Doermann.
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