Remains of three million shipwrecks are thought to be scattered throughout the Earth's oceans. Buried treasure aside, researchers have a growing interest for locating these ships, as modern-era wrecks often leak onboard fuel and have corroded heavy metals, posing serious risk to the environment.
Shipwrecks commonly occur near the shore, where rocks, reefs or other submerged objects make it difficult to navigate. Researchers using data collected by the NASA/USGS Landsat 8 satellite found that shipwrecks near the coast can leave sediment plumes extending over two miles on the water's surface in their wake. This, in turn, reveals their location.
Now, with a quarter of all shipwrecks residing in the North Atlantic, the Council of Europe's Parliamentary Assembly has recommended they be mapped and monitored. The goal, they say, is to mitigate the potential negative impacts the modern-era shipwrecks may have on the environment.
Previous methods used to locate shipwrecks require clear waters and are fairly costly. The Landsat satellite, however, can detect shipwrecks in sediment-laden coastal waters.
Using 21 Landsat 8 images and tidal models, researchers mapped sediment plumes extending from several wreck locations in a coastal area off of the Belgium port of Zeebrugge.
The study was led by authors Matthias Baeye and Michael Fettweis, from the Royal Belgian Institute of Natural Sciences; Rory Quinn from Ulster University in Northern Ireland; and Samuel Deleu from Flemish Hydrography, Agency for Maritime and Coastal Services.
Based on their findings, the authors suggest that the exposed structure of these ships created scour pits that fill with fine sediments - sand, clay or organic matter - when the current is relatively still. Then, during ebb and flood tides, the sediments are re-suspended in the water, leaving a trail for researchers to follow to locate the wreck.
Researchers examined shipwrecks in waters as deep as 50 feet. Depth is important note in terms of their research, as the re-suspended sediment plumes must reach the ocean's surface to be detected by optical satellites like Landsat.
Since most shipwrecks occur in coastal water that are shallow and sediment-laden, researchers believe their new methods could prove useful for marine archaeologists. Their study was recently published in the Journal of Archaeological Science.
