Solid Shoreline and Polar Vortex Events
How Does This Happen on the Great Lakes?
How do those twenty foot snow hills form off the shoreline of the Great Lakes?
Having lived near Lake Michigan all my life, I often wondered how that happened. After many years, I finally seized the opportunity to watch the progression! If you look closely at the photo above (click to enlarge) and the video below, you will see waves splashing up over the ice sheet or ice shelf. Sometimes, depending on the wind and weather, the waves will reach 40 feet into the air. Well, every time the waves land on the existing frozen ice shelf, they deposit sand filled ice chunks. The constant barrage of waves and ice chunks gradually build up the mounds into the giant spectacles they are. Once the initial ice sheet spreads farther out from shore, the process stops and the ice mounds remain suspended.
Waves with Ice Chunks Slam into Lake Michigan"s Ice Shelf
Waves Slamming Under The Ice Shelf
But it doesn't end there. The process repeats itself as the ice sheet expands. It creates a fascinating mountain range of ice cliffs with numerous rows or tiers of ice mounds along Lake Michigan's winter shoreline.
The following article will venture deeper into the process with videos and photos, so hang on to your seats to observe this amazing phenomenon. Also, I include photos of the ice shelf before, during and after a polar vortex event, as well as an in-depth look into why it's dangerous to walk on it.
The Beginning of the Ice Shelf
The Freezing Proess
But what is the process whereby the fresh water reservoirs of the Great Lakes suddenly transform from free-flowing into frozen suspension in the first place?
First, the air temperature falls below freezing, and then the surface of the water. Next, ice chunks form—which are often rolled into ice balls by wave action—and float on the surface. If the lake is fairly calm, the ice chunks are slowly pushed towards the shore and stick together. The result is not necessarily a solid sheet, at first, but rather ice balls freezing together on the shoreline. This phenomenon is the beginning of the ice sheet that will continue to spread farther off shore if temperatures stay below freezing.
The following group of photos were taken before the big storm struck showing the progression when the ice sheet initially forms.
Types of Great Lakes Ice
But do you think all ice on the Great Lakes is the same?
That’s not the case. And now scientists have found a way to characterize the differences between the types. The development was reported recently in the International Association for Great Lakes Research using math. It's an important discovery for two major reasons.
- To assist the Coast Guard in breaking up large ice formations
- To help weather scientists predict evaporation that could lead to lake effect snow
Researchers from the National Oceanic and Atmospheric Administration and National Aeronautics and Space Administration developed a radar system and an algorithm to detect types of ice formations on the Great Lakes.
The researchers use radar systems from either satellites or mounted locations to bounce a signal off the ice. The radar sends back a “signature", which can be interpreted using an equation to determine which type of ice lays on the water surface. This signature and resulting information from the equation allows scientists to see things such as density and depth of ice.
Though the algorithm can detect up to 20 different variations of ice formations, the researches boiled those down to five key types:
- Brash ice – Large, thick ice chunks that break off of other larger ice formations
- Pancake ice – Round pieces of ice a few inches thick where the edges often curl up as ice pieces merge together
- Consolidated pack ice – Large ice floes that have frozen together
- Stratified ice – Layered ice with differing thickness and density from top to bottom
- Lake ice – traditional, thin blue ice that forms atop lakes
The algorithm can also detect calm water.
Ice-Breaking Ships on Lake Michigan
When Does the Ice Sheet Spread?
Often during winter in the Great Lakes region (not just during the 2014 Polar Vortex event), freezing temperatures persist for days in a row, and cause the sheet to continue to grow and move out further past the shoreline, especially when the lake is calm. But when the 2014 polar vortex created temperatures in the single digits with wind-chill factors as low as minus 35 degrees Fahrenheit, the ice pack held down the wave action regardless of the high winds. The sheet stretched to the horizon and in some locations, as far as the eye could see! Observe in photos below!
Dangers on the Ice Shelf
About one week after the Polar Vortex event, temperatures rose and quickly began to melt the ice shelf posing unforeseen dangers for adventurers.
I feel the need here to warn people about the dangers of the ice shelf. Every year, someone creeps too close to the edge of the big ice hills and plummets into the freezing water of Lake Michigan below. Hypothermia sets in quickly along with loss of muscle control. Sadly, too many people have lost their lives this way. One incident I recall, in particular, when a young boy fell in and drowned, along with his father trying to save him.
The farther out a person decides to venture, the deeper the lake water, so it's wise to stay closer to shore. The people in the photos above were taking huge risks, especially the guy in the first picture who was so far out that no one could have saved him if he had gotten into trouble. Also, the guy on the top edge of an ice mound in the other photo could have easily fallen in. The temperature was in the 40's and things were melting fast creating slippery surfaces.
DON'T BE FOOLED into thinking the large ice hills are solid. Underneath them are loose cracks and pockets caused by the force of the waves, especially when things start to melt. I can't stress this enough! The pockets grow with warmer weather and you never know when an overhang is going to cave in. Another problem is that people can easily lose footing along the edges as the surfaces get very slippery from the melting and refreezing process.
THE PHOTOS BELOW demonstrate how cracks and crevices develop and expand when the mercury rises, posing threats of falling through.
You may be wondering if I took risks in order to capture these photos? Well, slightly, I admit, but I was careful not to go past the first tier of ice shelf mounds where the water would've been over my head in case I did fall through. Plus, the closer you are to shore, the more solid the ice shelf. If you look closely at the photo below, you can observe three rows or tiers where the splashing ice balls did their thing.
How do the mounds build up in rows that way? It has to do with the wind and temperatures. The first tier becomes stabilized, then weather conditions repeat the process.
I CAPTURED these willing sightseers on the first tier of the ice sheet and that was precarious enough for us all. We did not walk farther out from this spot where the water is deeper and the shelf is shallower. We stayed backed, but watched others foolishly venture out to the distant edges of the ice shelf.
. . . And finally, when temperatures continue to steadily warm, the snow and ice chunks separate once again as seen in the photos below from a later date. The first photo shows a big chunk of snowy ice that stubbornly hung onto the old breakers.
And then you can do this . . .
Which of the Great Lakes have you visited most often?
© 2014 Kathi