The Vulnerable History at the Bottom of Lake Superior

Isle Royale National Park is a treasure trove of shipwrecks, but they may not last

In June of 1928, Louis Coutu, a Canadian trapper working at the mouth of the Agawa River in Lake Superior, happened upon a corked bottle carrying a startling note. Signed “Al, who is dead,” the message-in-a-bottle described the harrowing story of Alice Bettridge, the lone survivor of the SS Kamloops, shipwrecked during a blinding storm in December 1927. Bettridge wrote, “I am the last one left alive, freezing and starving to death on Isle Royale. I just want mom and dad to know my fate.”

When divers finally discovered the Kamloops in 1977, the ship was 270 feet beneath the surface of Lake Superior — and only a stone’s throw from the north coast of Isle Royale National Park. Remarkably, even after 50 years of submersion, the Kamloops remained intact, protected by deep, frigid freshwater that limits the bacteria that usually destroy shipwrecks. Equally preserved by these unique conditions was the body of “Old Whitey,” trapped in the engine room. His ghost, according to diver’s lore, still stalks explorers of the wreckage.

Wheel of the SS Kamloops

But Kamloops is hardly unique in Isle Royale National Park. Located along a once popular shipping lane off the Minnesota coast, the island chain’s jagged rocks and shallow reefs have claimed ten major shipwrecks and menaced generations of lakefarers in the blizzard-plagued, fog-drenched weather of Lake Superior. Despite the dangers, people have made the voyage to Isle Royale for thousands of years: Indigenous groups established an elaborate network of copper mines on the islands; French fur traders, active in the region during the eighteenth century, were attracted to Isle Royale for its beaver population; and in the nineteenth century, ship captains carrying people and goods to Duluth or Port Arthur, both burgeoning Minnesota port towns, navigated the island chain daily.

Today most visitors are drawn to Isle Royale by its dual status as a national park and UNESCO Biosphere Reserve, celebrated for its pristine conifer forests, nighttime panoramas of the Northern Lights, and isolated populations of moose and gray wolves. But it’s the unique conditions that have preserved its extraordinary number of shipwrecks that make Isle Royale an especially appealing destination for freshwater diving.

As climate change warms Lake Superior, though, the stable underwater environment that made time capsules of Isle Royale’s shipwrecks is becoming more volatile, creating new hazards that leave the wrecks — and the maritime histories they preserve — vulnerable to decay and collapse. These sites offer a glimpse into the delicate balance of underwater ecosystems and how easily they are disturbed by a warming planet.

Speaking to The Minnesota Star Tribune, Professor Jay Austin, an oceanographer who studies Lake Superior at University of Minnesota Duluth, described Superior as “one of the more rapidly warming” lakes not only in the region but, according to a NASA-backed study, the entire world. Austin added that his own research — which demonstrates a four-degree temperature increase between 1979 and 2007 — also documents a “significant reduction” in lake ice that’s likely to continue in decades ahead.

Isle Royale National Park

Lake ice serves a critical role in the larger ecosystem of Lake Superior. More than a bridge for species to cross between the mainland and islands, lake ice acts as an insulator, reflecting the sun’s energy back into space and creating a colder underwater environment that has preserved Isle Royale’s shipwrecks. As Superior’s ice melts earlier in spring each year, the lake absorbs more days of sunlight and undergoes incremental warming.

Once loosened, the formerly protective layers of ice are transformed into indiscriminate weapons, thrown against the masts and bows of shallow shipwrecks by increasingly unpredictable storms. And while deeper wrecks avoid damage from weakened ice sheets, they cannot escape the destructive impact of warming water, especially the growth of bacteria and microbes that speed the decay of wood and the corrosion of metal.

Warmer water also provides a better breeding habitat for zebra mussels, an invasive species of shellfish. These shellfish, which reproduce faster in higher temperatures, are filter feeders that survive on algae and small particles from the solid surfaces they envelope, including shipwrecks. In addition to corroding shipwrecks with their acidic feces, researchers report that as zebra mussels pile atop one another on wrecks, the creatures not only obscure the original structures but often create enough weight to cause their collapse.

Speaking to Newsweek about the proliferation of zebra mussels in the other Great Lakes, Durrell Martin, president of Save Ontario Shipwrecks, said, “Shipwrecks are disintegrating at a faster rate than we have ever seen.” He continued, “Shipwrecks we thought would be here another 200 years from now and we could enjoy, we realized probably within the next 10 to 20 years, they’ll all be gone. They’ll be piles of lumber on the bottom.” “We can’t stop this,” Martin lamented.

So far, the invasion of zebra mussels -- which has been devastating across the Great Lakes -- has been mild in Superior, largely due to its colder water, lower calcium levels, and relative isolation.

Zebra mussels

But in 2009, zebra mussels were finally spotted in Isle Royale National Park. And because the mussels thrive in warmer, shallower water, where sunlight fuels the microscopic algae on which they feed, researchers and rangers are particularly concerned about the park’s shallowest shipwrecks — especially the SS America, the most popular and accessible of the major wrecks.

In fact, the SS America is the wreck most at-risk from various climate-related hazards and the one with the deepest ties to local history. As a long-running passenger steamship that carried mail, critical supplies, and news to people along Lake Superior’s isolated western shore, the America represented a connection to the outside world. Lives were built around the ship, and communities were sustained by it. And its sinking remains the source of local legend. Some residents still speculate that the accident – survived by everyone except a dog tied to the stern – was an attempt to make a fraudulent insurance claim as the newly built Highway 61 threatened America’s business with an alternative, land-based supply route.

Historians, however, hew to the standard narrative that the ship reached its end in 1928 when John Wick, its first mate, accidentally struck a submerged reef while departing Isle Royale. Although the stern settled about 85 feet under water, the bow initially remained above the surface, making it a popular site for visitors -- and an enduring reminder of the region’s history. Today, even after a century of damage from ice, the bow begins only two feet beneath the water, still easily visible to boaters and great for divers but also highly vulnerable to unstable ice and zebra mussels, which thrive at depths between six and 30 feet.

Wreck of the SS America

Park officials in Isle Royale have taken extraordinary measures to stop the mussels before they harm the SS America and the unique historical lens it preserves of Lake Superior’s once isolated western shore. Researchers have conducted dives to scour underwater rocks for zebra mussels, prying them off one-by-one to remove them from the lake. Park rangers have even turned back ships with mussels attached to their hulls.

But thousands of ships enter Isle Royale each year, and the park is home to more underwater rocks than any small team can scour, raising questions about whether protecting wrecks will become a sisyphean battle as water warms and invasive mussels proliferate. It doesn’t help that the park staff is likely to shrink with the Trump Administration’s payroll cuts for the National Park Service.

The dangers ahead for Isle Royale’s shipwrecks remind us that climate change is a many-headed monster, threatening both ecosystems and the physical history of how humans have interacted with them. As Lake Superior warms, the conditions that preserved its shipwrecks are disappearing, and its future as a one-of-a-kind underwater museum is no longer guaranteed.