The Great Lakes are taking one last shot in 2025 to remind everyone their waves can be more fierce than what the vast oceans typically conjure up.
Gale force winds producing waves not seen since the sinking of the Edmund Fitzgerald in 1975 are expected through Dec. 29 and continue into Tuesday before tapering off. That means waves in some parts of Lake Superior could reach more than 20 feet, and may occasionally pop over 30 feet.
There are several reasons the Great Lakes can be more dangerous than an ocean.
Lake storms are volatile, build up fast
On the Great Lakes, the wind cuts from every direction, waves build without warning and water churns with a cold, erratic energy. Waves are steeper and packed closer together than on the ocean.
That volatility can make navigating the Great Lakes particularly dangerous.
Paul Christensen, vice president of vessel operations for Interlake Maritime Services — who has sailed on both the ocean and Great Lakes — said that waves on the Great Lakes build up much faster than on the ocean. Christensen compared it to the difference between a swimming pool and a bathtub — it doesn’t take as much energy to get water moving in a smaller space.
Choppy lake waves versus smooth ocean swells
In the Great Lakes, waves are created by wind from storms nearby. They are referred to as locally generated seas, said John Lenters, a climate and lake scientist at the University of Michigan. These seas tend to be small and irregular, causing choppy conditions.
If a storm is sitting right on top of a vessel, it can feel like being inside a hurricane, Lenters said.
Oceans are much more vast, so vessels are much more likely to be dealing with swells — which are older, leftover waves coming from distant storms, Lenters said. Swells are smoother and the salt in ocean water can help weigh the waves down, although only slightly.
It’s a lot more comfortable to be on a 20-foot swell in the ocean than it is to be on 20-foot seas in Lake Superior, Lenters said.
Ships can ride multiple waves at once on Great Lakes
Besides being a rougher ride, waves travel much closer together on the Great Lakes than they do in the ocean.
In the ocean, waves usually travel more than 10 seconds apart, providing enough distance for large ships to sail in between them, Lenters said.
In the Great Lakes, Lenters said, typical wave periods can be between two and five seconds — so a large ship can sit on multiple waves at once.
If the bow and stern of a heavy-laden ship are both sitting on a wave crest, the ship’s hull can sag. Likewise, if a wave crest is midship, the hull can bend upwards, draping over the crest, which is referred to as hogging.
The constant bending every few seconds can cause metal fatigue, which is why some ships have been known to snap in half eventually on the Great Lakes.
Freshwater freezes faster than salt water
Freezing temperatures can be more of a hazard during rough seas on the Great Lakes compared to the ocean, Christensen said.
Freshwater sprayed onto ships from waves and rain freezes faster than salt water does. That’s because salt lowers the freezing point of water, meaning it has to be colder for salt water to freeze.
Not only can a ship become coated in ice quicker on a lake, Lenters said, but that ice can add significant weight to ships.
Crew prepares to search for shipwrecks on the bottom of Lake Michigan
A crew with NOAA and Great Lakes Environmental Research lab searches for shipwrecks on the bottom of Lake Michigan
Caitlin Looby covers the Great Lakes and the environment for the Milwaukee Journal Sentinel. Reach her at [email protected] and find her on X @caitlooby. All of her work and coverage decisions are overseen solely by Journal Sentinel editors.
Caitlin is an Outrider Fellow whose reporting also receives support from the Brico Fund, Fund for Lake Michigan, Barbara K. Frank, and individual contributions to the Journal Sentinel Community-Funded Journalism Project. The project is administered by Local Media Foundation, tax ID #36-4427750, a Section 501(c)(3) charitable trust affiliated with Local Media Association.
