Maritime
Archaeology
The
Stellwagen Bank National Marine Sanctuary uses a variety of tools
and techniques to locate and document shipwreck sites. Since the
sanctuary's seafloor lies at depths ranging from 65 to 600 feet,
sophisticated equipment is often needed to conduct archaeological
research. Sanctuary researchers have used SCUBA, side scan sonar,
remotely operated vehicles (ROVs), and autonomous underwater vehicles
(AUVs). Through its partnerships, the sanctuary strives to use
cutting-edge technology to bring to life New England's maritime
history.
Divers
onboard the R/V Connecticut prepare to investigate a shipwreck.
Courtesy of NOAA/SBNMS, NURC-UConn, UConn, and NUWC.
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The
towfish registers the reflected sound and a computer on
board the research vessel interprets the sound into a seafloor
image. Side scan sonar can only locate shipwrecks that protrude
above the seafloor.
Another
tool used to locate shipwrecks is a magnetometer. Magnetometers
are also towed behind a research vessel, where they detect
variations in the earth's magnetic field that may be caused
by the iron or other magnetic materials on or embedded in
the seafloor. A magnetometer can detect shipwreck features
such as anchors, cannons, and machinery
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A
side scan sonar (yellow) uses sound to image seafloor. A
magnetometer (orange)
detects iron objects on the seafloor.
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A
side scan sonar image of the steamship Portland.
Courtesy of Klein Sonar Associates.
Once
a shipwreck is located it is time to get in the water. Sanctuary
researchers use SCUBA diving equipment to slip below the ocean's
surface and examine the shipwrecks first hand. SCUBA equipment
allows the researchers to comfortably breathe and stay warm in
the cold New England water. Archaeological divers carry measuring
tapes, slates, and pencils to create scaled drawings of the shipwrecks.
The scaled drawing are analyzed and compared to information in
the historical record that might reveal when the ship was in service
and what kind of vessel it was. Divers also use video and still
photography to document the site.
Sanctuary
divers examine and photograph the remains of shipwrecks to determine
their archaeological and historical significance. Courtesy of
Tane Casserley, NOAA's MHP.
Shipwrecks
in deeper sections of the sanctuary are explored with remotely
operated vehicles (ROVs). ROVs are tethered robots that "fly"
through the water, allowing sanctuary scientists to spend hours
gathering archaeological data without being limited by the cold
water, air supply, and depths. Equipped with lights and video
cameras, ROVs are launched and controlled from a research vessel
positioned above the shipwreck. Archaeologists study the video
transmitted through the tether to determine the age, characteristics,
and possible identity of the shipwreck. The sanctuary conducts
yearly ROV cruises, in partnership with the National Undersea
Research Center at the University of Connecticut (NURC-UConn)
and other institutions.
The
NURC-UConn ROV Hela is launched from the
research vessel to image shipwrecks in the depths of the sanctuary.
Courtesy of Anne Smrcina, NOAA/SBNMS.
The
newest technology used by the sanctuary is an autonomous underwater
vehicle (AUV). AUV's are un-tethered robots programmed to maneuver
along a predetermined path and fulfill a specific function, such
as taking photographs or sampling the water. After the AUV completes
its mission, it returns to the surface where researchers retrive
up the vehicle and download the data collected during the mission.
AUVs used by the sanctuary to investigate maritime heritage resources
have been outfitted with downward facing cameras to gather images
that will be pieced together to build a photomosaic.
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The
sanctuary has conducted AUV surveys on shipwrecks in partnership
with Woods Hole Oceanographic Institution (WHOI), the Naval
Undersea Warfare Center (NUWC), and NURC-UConn. |
Two
REMUS AUVs. The vehicle on the right (with its cover removed)
is having data download and its batteries charged. Courtesy of
NOAA/SBNMS, NURC-UConn, UConn, and NUWC.
Maritime
archaeologists use their tools and techniques to fulfill the sanctuary's
requirements to locate, assess, protect, and interpret its maritime
heritage resources. Technological advancements will undoubtedly
allow archaeologists to better tell the human stories represented
by the sanctuary's historic shipwrecks.
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