Chris Sabick dives the Phoenix shipwreck, photographed by Kotaro Yamafune

A Sinking Feeling: Climate Change and Underwater History

By Chris Sabick, Interim Co-Director and Director of Research and Archaeology

The historic rainfall and flooding in Vermont this summer have impacted people, businesses, and watersheds, Lake Champlain included. While I’m grateful that our Museum exhibits and collections remain safe, I am keenly aware of the challenges the floods created for our staff and community, and the impact that flooding and other climate change events have on the lake, as well as the history underwater in Lake Champlain.

Lake Champlain Maritime Museum is dedicated to inspiring people to make personal connections to Lake Champlain through our region’s history, ecology, and archeology. For the Museum’s archaeology team, this work of making connections includes conducting ongoing archeological research, on land and underwater; caring for our collection of artifacts and research; and managing the lake’s underwater cultural resources and the Lake Champlain Underwater Historic Preserves, a unique system of shipwrecks in the lake open for divers to explore each May–October.

The flooding and ongoing climate change are threats to our work, our lake, and the lake’s shipwrecks and other underwater cultural resources. Let’s talk about why.

How many shipwrecks are there in Lake Champlain?

Lake Champlain is a great historical record and research space for shipwrecks. Humans have been living around and traveling on Lake Champlain for over 12,000 years. And the lake’s depth and location make it deep, dark, and cold which is the ideal environment for preserving shipwrecks. We estimate there are 200-300 shipwrecks in Lake Champlain, and they cover pretty much all eras of the lake’s history. There are dugout or birch bark canoes from the Native American period; gunboats, galleys, and transportation vessels from the Military Period; a wide variety of canal boats and steamboats from the Commercial Period; and sailing craft, rowing boats, and other vessels from the present Recreation Period.

How is climate change impacting the lake?

The Lake Champlain Basin is a watershed of 8,234 square miles. The basin encompasses all the waterways that are connected to Lake Champlain and what happens in one impacts the whole basin. So what’s happening? According to a 2020 report from the Nature Conservancy, the mean annual air temperature increased by 2.1 degrees Fahrenheit between 1967 and 2005, with most of those temperature increases happening during the winter months. As a result, the lake is freezing over less frequently and later each year. According modeling from the Lake Champlain Basin Program, the lake freezes over about once every four years now, and the Basin Program’s researchers estimate that by 2050, the lake may freeze just once per decade. In addition, annual precipitation has increased, as we are keenly aware of this year, and there are more frequent intense storm events. As the Basin Program notes, heavy rainfall can affect water quality by causing erosion, flooding, and sewer overflows which carry pathogens and sediments through tributaries and into the lake. Lake Champlain Sea Grant predicts that annual average precipitation will continue to increase in our region, including more extreme precipitation events that could increase the frequency and intensity of floods.

How does flooding impact our work and shipwrecks?

Flooding like we experienced last month causes runoff into the lake and increased siltation. Compare the two pictures below of a hand truck at the shipwreck of the canal boat OJ Walker, located just outside of Burlington Harbor. On the left is a photo from the late 1980s and on the right from 2019.

An underwater view of a hand truck by the shipwreck of the OJ Walker in the 1980s
The hand truck discovered underwater by the shipwreck of the OJ Walker in 2019, almost completely obscured by zebra mussels and silt.

Above Left: The hand truck from the OJ Walker shipwreck in the 1980s. / Right: The same hand truck in 2019.

In the image from the 1980s, you can see the two-wheel hand truck is sitting on the lake bottom surrounded by brick and drainage tile, which is what this ship was carrying when it sank. In the picture on the right, you can see all those details are obscured by the extensive siltation that’s happened in recent years. The hand truck is also obscured by globs of zebra mussels, an invasive species that will continue to spread as the lake keeps warming – more on that below.

Siltation obscures history, access, and complicates future research. And, most recently, it has prevented us from opening two of the dive sites in the Lake Champlain Underwater Historic Preserves as flood waters continue dumping silt and mud on the shipwreck sites of the Water Witch and the Diamond Island Stone Boat.

What about warmer winters and shipwrecks?

Warmer winters mean less ice and higher water temperatures, which creates a longer growing period for the summer biological activity including the growth of invasive species and harmful cyanobacteria blooms. While invasive species have been infesting the lake since the 1800s, in 2020 there were 51 documented invasive species in Lake Champlain.

Among these invasives, zebra mussels are a significant threat to shipwrecks as they create these enormously thick colonies that coat the shipwrecks and their structures. Compare the two images below of an anchor before and after the arrival of zebra mussels.

An anchor resting in place on a shipwreck in the 1980s

Above left: An anchor resting in place on a shipwreck in the 1980s. / Right: The anchor has been completely covered by zebra mussels.

Within zebra mussel colonies, a sulfate-reducing bacteria begins to thrive, feeding on the iron components of shipwrecks. Over time the destruction of the iron and the tremendous weight of thousands of mussels can cause a shipwreck to collapse. And while Lake Champlain’s deep, cold water has protected deeper shipwrecks in the past – zebra mussels don’t like cold water and they have colonized the lake only to 100 feet below the surface – as the water temperature increases each year, the mussels will be able to move into deeper water and colonize those previously protected wrecks.

An urgent, imminent example of how all threats impact our lake’s history is the Spitfire, a Revolutionary War gunboat that sunk in deep water on the New York side of Lake Champlain. The vessel sits on the lake bottom, virtually intact with the mast still standing on this vessel and the bow gun in place as depicted in the painting below. It’s a beautifully-preserved shipwreck that our team is actively studying. But even in deep water, it’s not immune.

Painting of the Spitfire by Ernie Haas.

In recent surveys, as you can see in the pictures below, we have discovered there is a huge mass of weeds at the bow gun, specifically Eurasian Milfoil, another invasive species in Lake Champlain. Milfoil normally grows in warm, shallow water but this batch was dislodged during a major storm and became entangled on the Spitfire. It also carried along zebra mussels, which you can see have relocated to the shipwreck and can now be seen around the back of the bow cannon. They won’t be going away anytime soon. It’s scary to think what can happen to even the wrecks we once considered protected in the very deep waters of Lake Champlain.

A tumble of Eurasian Milfoil at the bow gun of the Spitfire.

Zebra mussels have been noted on the back of the ship’s bow cannon.

What is lost?

Flooding events and climate change limit create unsafe conditions where we can’t get in the water as researchers or avocational divers. We lose direct access to our underwater historical resources.

When invasive species, siltation, and floods erode, damage, and obscure shipwrecks we also lose data, evidence, and the ability to continue learning about our past. New generations of archaeologists, scientists, and historians will not be able to help us uncover new information when the evidence is gone.

When we lose access and evidence, we also lose our sense of our place, identity, and change. Connecting to our past helps us feel connected to our community in the present and plan for a better future for our community and lake. When evidence of the past no longer exists, what happens to those connections and our future?

What’s next?

As we recover from the floods with a keen awareness that climate change and severe weather events will continue in our future, we are all thinking about how to protect our state, our people, and our environment in the future. I hope you will join me in also considering how to protect our history and see our underwater cultural resources as both a treasure to be preserved and a tool for identifying and stopping climate change.

Our community citizen scientists, organizations like the Lake Champlain Basin Program, divers, researchers, and even the shipwrecks themselves can be part of the solution because it’s not too late. There’s more that all of us can do to protect our environment, our history, and our community. Thank you for doing that with us and joining us as we continue this work.  

Top image: Chris Sabick dives the shipwreck Phoenix, photograph by Kotaro Yamafune.