Regardless of a chilly snap in February, low ice cowl prevailed throughout the lakes in winter 2020-2021.
In any given 12 months, the formation, motion, and timing of ice cowl on the Great Lakes is temperamental—altering considerably with shifts in climate and local weather patterns. The 2020-2021 winter season suits that profile, as wild swings in the climate took Great Lakes ice on a wild trip.
The highs and lows are seen in these natural-color photos, acquired with the Seen Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite tv for pc. On February 20 (picture above), whole ice cowl throughout the lakes was close to the season’s most extent of 46.5 %. By March 3 (picture beneath), ice lined simply 15 % of the lake surfaces.
Curiously, the utmost ice cowl this 12 months was close to the 1973-2020 common of 53 %, in keeping with Jia Wang, an ice climatologist at NOAA’s Great Lakes Environmental Analysis Laboratory.
However that’s the place the averageness ends. A lot of this ice season—which runs from December 1 by April 30—introduced very low ranges of ice cowl. The exception was early February 2021, when ice made a fast however short-lived look throughout a go to of frigid Arctic air. “So, I might name it low ice 12 months, regardless of the February chilly snap,” Wang stated.
The chart above exhibits the development of ice protection in the course of the 2020-2021 season. In response to Wang, air temperatures are the primary issue affecting ice cowl on the Great Lakes. This season began with unseasonably gentle temperatures, as a lot as 8° Fahrenheit (4.5° Celsius) above regular by mid-January. Lake Erie—the shallowest of the Great Lakes and sometimes the primary to freeze—had one of many lowest quantities of ice on report for the time of 12 months.
Early February introduced a dramatic shift. Temperatures plummeted as little as 17° F beneath regular and blue lakes remodeled into white lakes. However when temperatures climbed once more in mid-February, the delicate ice cowl broke up and melted as quick because it had fashioned. “I anticipated chilly climate would stay for an additional two weeks till the tip of February,” Wang stated. “I didn’t count on it to return and go so quick.”
Ice cowl on the Great Lakes can fluctuate dramatically from 12 months to 12 months, managed by 4 patterns of local weather variability: the North Atlantic Oscillation, the Atlantic Multidecadal Oscillation, the Pacific Decadal Oscillation, and the El Niño-Southern Oscillation. The best most ice cowl (94.7 %) on report occurred in 1979, and the bottom most (11.9 %) occurred in 2002. Low ice cowl additionally prevailed in the course of the 2019-2020 season. The long-term pattern in ice cowl has usually been downward, declining about 5 % every decade for the reason that early Nineteen Seventies.
NASA Earth Observatory photos by Joshua Stevens, utilizing VIIRS knowledge from NASA EOSDIS LANCE, GIBS/Worldview, and the Suomi Nationwide Polar-orbiting Partnership and lake ice knowledge from NOAA – Great Lakes Environmental Analysis Laboratory.