Ice covers the Great Lakes. (Photo: NASA Earth Observatory)
Think all ice is the same?
That’s not the case on the Great Lakes. And now scientists have found out how to detect the differences.
With math.
The development, reported recently in the International Association for Great Lakes Research, is important because it could help guide freighters through icy seas, assist the Coast Guard in breaking up large ice formations and help weather scientists predict evaporation that could lead to lake effect snow.
Researchers George Leshkevich of the National Oceanic and Atmospheric Administration and Son Nghiem of the 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 what Nghiem and Leshkevich call 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.
Just as the handwriting of two different people will never look the exact same, the different types of ice will return a unique signature that can be deciphered by scientists.
Leshkevich created an algorithm that could differentiate one ice type from another by analyzing data from as far back as 1997. His algorithm allows researchers to differentiate ice types by plugging in the data returned to the radar mechanism, and reading it to see which ice lies below.
It produces data specific to each kind of ice formation, said Nghiem.
“You kind of create a dictionary which can translate the radar signature into a physical environment, like a different kind of ice type,” Nghiem said.
Though the algorithm can detect up to 20 different variations of ice formations, Leshkevich and Nghiem 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.
One application of the data is for the U.S. Coast Guard, which breaks ice for commercial freighters. The data will help the Coast Guard maneuver around the dangerous and damaging ice, which makes the clearing of shipping paths much easier, said Leshkevich.
A United States Coast Guard icebreaker navigates icy water. (Coast Guard Digital Photo)
“Some types of ice, like brash ice, are very problematic to shipping,” he said. “It’s very angular and can get very thick, and this ice is difficult sometimes even for the Coast Guard icebreakers to break through.”
The Coast Guard is anxiously waiting for the technology to be applied in the Great Lakes, said Mark Gill, director of vessel traffic service for the U.S. Coast Guard. However, that is at least a few years away.
“This product will enable us to not only see the ice, but also tell what type of ice is there,” said Gill. “We’re really excited about being to put that into use here as we come into the future domestic icebreaking seasons.”
By being able locate the most troublesome areas of ice, Coast Guard navigators can lessen damage to both their own ships and the ones they create paths for, Gill said.
“Knowing where the brash ice starts, and how we route traffic around it, can mean avoiding damage and unnecessary delays if we know where it’s at,” he said.
The technology can also assist ecologists and fishery workers in understanding how the winter’s ice cover may impact fish populations, said Leshkevich.
“Fisheries are interested in it because some species need a stable ice cover over spawning beds for fish recruitment the next season,” he said. “(They) want to know the extent of the thickness and type of ice.”
The research can even help amateur boaters travel in the spring soon after a thaw by downloading a map that highlights current ice formations, said Nghiem.
“If you have a boat, and you want to go out sometime in the springtime when the ice starts to break up, you can download this map,” he said.
Nghiem plans to post these maps online. Boaters could download them to plot a path that avoids ice and instead heads toward open water.
While all ice may seem the same, knowing the difference can be beneficial for a number of industries. Leshkevich says the technology isn’t yet being applied directly, but he anticipates that in a few years their study will help make the frozen Great Lakes waters a little easier to understand.