But Shipwrecks Are Already Underwater! The Impacts of Changing Climate on Underwater Archaeological Sites

North Carolina Heritage at Risk

Imagine that you are a passenger on the USS Huron in November 1877; a surveyor bound for Havana to survey Cuba’s coastline. After leaving Hampton Roads in Virginia, the first day at sea is peaceful. But as night descends, dark clouds are seen on the horizon and soon you and your shipmates find yourselves in the middle of a powerful storm strikes. Unbeknownst to you, the ship's compass is malfunctioning, adding to the challenges. The ship comes to a sudden stop on a sandbar, and you realize you're only two hundred yards from the shore, but you're unsure of your exact location. The water is freezing cold, and waves crash over the sides of the vessel. Swimming to shore seems tempting, but the icy temperatures make you reconsider, hoping someone from land will come to your aid. Throughout the night, the relentless storm takes a toll on you, your fellow sailors, and the ship itself. The powerful waves break the ship apart, forcing everyone to end up in the water. Thankfully, you manage to reach the shore, but sadly, many of your fellow sailors have lost their lives at sea.

Since this traumatic event, the USS Huron has mostly stayed intact on the ocean floor, about 250 yards from the beach. However, the elements have taken a toll, causing erosion and covering the site with marine growth and concretion. This has led to ongoing environmental challenges that may further break up the vessel.

North Carolina's coastline and interior waterways are dotted with shipwrecks like the USS Huron, providing a glimpse into the state's rich maritime history. The Underwater Archaeology Branch has documented over 1,000 shipwreck sites, ranging from ancient dugout canoes to colonial sailing vessels, Civil War shipwrecks, and 19th and 20th-century steamboats. These shipwrecks offer homes to various aquatic organisms and enrich our understanding of North Carolina's past.

Besides shipwrecks, North Carolina's aquatic waterways and shorelines hold other cultural resources, such as historic ports, bridge crossings, plantation landings, and harbor developments, all of which shed light on the state's social, economic, and political growth.

As we have discussed in previous blogs, the waterways and oceans are undergoing changes that put North Carolina's submerged resources at risk. The stability of these sites relies on physical, chemical, and biological processes in their local environment. However, the changing conditions, including warmer temperatures, increased acidity, stronger storms, and shifts in fish populations, are impacting these environments and affecting the stability of the submerged sites.

Let’s examine the wreck of the USS Huron as an example of how underwater cultural resources are influenced by these changes. The iron-hulled gunboat now sits about 250 yards off shore in the shallow waters of the Atlantic Ocean near Nags Head, North Carolina.

• Since the ship wrecked in 1877, global ocean temperatures have risen by approximately 2°F, about 0.14°F per decade. This warming affects the preservation conditions of the wreck, leading to increased corrosion in the iron hull structure. The warmer waters have also caused tropical organisms like fish, mussels, invertebrates, and microorganisms to move farther north, altering the biological interactions at the site. This can result in the breakdown of remaining wooden features by common shipworms, damage caused by larger fish, and the introduction of invasive species with uncertain consequences.
• Over the past century, oceanic carbon dioxide levels have risen due to increased carbon dioxide in the air. This has made the ocean more acidic and disrupted the balance of minerals in the water, impacting metal corrosion rates. Acid-soluble metals will likely face quicker rates of corrosion than before. Additionally, changes in calcium carbonate production may affect the formation of concretion material, which safeguards iron materials from corrosion.
• Sea levels have also been rising since the loss of the USS Huron, with an average increase of about 0.06 inches per year over the past century, a rate that has nearly doubled in the past four decades. This rise affects the submerged site, potentially reducing the impact of wave energy and sediment movement. As a result, the seasonal sediment movement that exposes and buries the wreck may be less pronounced with deeper waters, possibly leaving it continuously exposed or permanently buried.

It's essential to recognize that similar changes are affecting underwater archaeological sites worldwide. Studies are ongoing in North Carolina and other regions to understand how climate change is impacting submerged resources. In our state, the OSA is conducting a survey of state-owned shorelines and waterways to document eroding, uncovered, and potentially damaged underwater archaeological resources. This study aims to comprehend the effects of stronger and more frequent storms on these sites and develop strategies to protect them proactively and reactively in the future. Stay updated on the progress of this ongoing project by following the OSA on Facebook for fieldwork and result updates in the coming months!

Main image: USS Huron as it left Hampton Roads, VA in November 1887 (Courtesy of NC UAB)

This material was produced with assistance from the Emergency Supplemental Historic Preservation Fund, administered by the National Park Service, Department of the Interior. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the Department of the Interior.

Sources:
North Carolina Office of State Archaeology 
2022     USS Huron Historic Shipwreck Preserve. NC Heritage Dive Sites. NC Office of State Archaeology Underwater Archaeology Branch.

United State Environmental Protection Agency (EPA)
2022     Climate Change Indicators: Ocean Acidity. Climate Change Indicators. United States Environmental Protection Agency.
2022     Climate Change Indicators: Sea Level. Climate Change Indicators. United States Environmental Protection Agency.
2022     Climate Change Indicators: Sea Surface Temperature. Climate Change Indicators. United States Environmental Protection Agency.

Wright, Jeneva
2016     Maritime Archaeology and Climate Change: An Invitation. Journal of Maritime Archaeology, 11(3):255-270.