And thanks to photographer Dawn M. LaPointe, we have a captivating new glimpse of another strange frozen-lake phenomenon: "ice stacking." Filmed on Feb. 13 at Lake Superior in Duluth, Minnesota, LaPointe's video features brittle, glasslike sheets of ice that buckle and jostle as they push against the shoreline.
"While shooting in Duluth's Canal Park, I noticed the ice had pulled away from shore and felt the breeze at my back," LaPointe writes on Facebook. "I anticipated there would be some ice stacking as the massive sheet of ice met the shorelines, so I headed to Brighton Beach. The big lake did not disappoint!"
She filmed for about two hours, but distilled her footage into the 2-minute video above. It's satisfying to watch, with meditative qualities akin to oozing lava. The sights and sounds were "incredible," according to LaPointe, who braved air temperatures as low as minus 8 degrees Fahrenheit (minus 22 Celsius) and minus 20 F with wind chill (minus 29 C) to record the scene. Her results convey eerie beauty, but they're also bewildering. What could possess ice to behave so strangely?
Lake Superior is not only the largest of all five Great Lakes; it's big enough to hold the other four combined, plus three extra Lake Eries. It's also the northernmost Great Lake, though, so swaths of its surface tend to freeze in winter despite its huge size. The lake almost completely iced over in the frigid winter of 2014, but as of mid-February 2016, it's only about 20 percent frozen. "This is the first good sheet of ice I've seen on the lake this year, at this end," LaPointe tells Garret Ellison of MLive.
Ice is concentrated along Lake Superior's shores, as seen in this Feb. 16 map from the U.S. National Oceanic and Atmospheric Administration (NOAA):
A map of Lake Superior ice concentration on Feb. 16, 2016. (Image: GLERL/NOAA)
All that ice averaged more than 2 centimeters thick (about 1 inch) on Feb. 16, according to NOAA data, but its mean thickness was closer to 1 centimeter on Feb. 13. Brisk winds were also blowing from the southwest that day, LaPointe points out, and they might have helped a big ice sheet break free.
"Four hours of 12-15 mph steady winds from the SW led up to the movement of the large sheets of ice," she writes. "Once the ice separated from shore and could gain momentum with the wind, it slowly moved in the direction of Brighton Beach."
The wind faded as LaPointe filmed, but that didn't stop ice flakes from shoving their way ashore. The pieces ranged in thickness from 0.25 to 3 inches (0.6 to 7.6 cm), she estimates, as they stacked into jagged piles on the beach. However exactly this happened, it offers yet another reminder of Mother Nature's uncanny creativity as an ice sculptor. And for LaPointe, it's also a testament to the wild beauty of Lake Superior — aka "Gitche Gumee," a derivation of the lake's Native American name.
"I am at awe and mesmerized by ice stacking ... and spent hours immersed in the sights and sounds of one of my favorite winter occurrences," she writes. "I hope you enjoy this glimpse into an incredible experience along the shores of Gitche Gumee!"