Dive 09: Deep-sea Detectives
A chance discovery in the submersible Alvin in 2015 by deep-diving colleagues from Duke University and Woods Hole Oceanographic Institution revealed the faint “ghost” of a wooden shipwreck more than a hundred miles off the coast of North Carolina in several thousand feet of water. We returned to the Blake Ridge Wreck with NOAA Ship Okeanos Explorer to better understand the site and to create a detailed, three-dimensional “map” of the wreck with our colleagues from the Bureau of Ocean Energy Management, other agencies, universities, the private sector, and the interested public. Click here to read the full caption.
Video courtesy of the NOAA Office of Ocean Exploration and Research, Windows to the Deep 2018. Download larger version (mp4, 37.6 MB).
The dive today visited an Underwater Cultural Heritage (UCH) site. This shipwreck was briefly visited during a human operated vehicle (HOV) Alvin dive in 2015, while surveying chemosynthetic communities associated with methane seeps. Based on the initial data collected by Alvin, archaeologists believed this to be the remains of a 19th century wooden shipwreck.
Located in deep water, much of the wooden hull of this vessel and whatever wooden artifacts that were once onboard have long since deteriorated, leaving only metal, ceramic, and other non-degradable artifacts where they would have been found originally in the ship. The purpose of today’s dive was to collect data that will be used to create a three-dimensional rendering of the vessel and to take a closer look at these artifacts to help date and identify the wreck. This reconstruction technique is called photogrammetry or structure from motion and by taking three or more pictures of the same item from different angles, scientists can create a three-dimensional model of it. Click here to learn more about photogrammetry techniques.
The remotely operated vehicle (ROV) Deep Discoverer was on the seafloor from 13:41:28 - 19:16:25 UTC and spanned a depth range of 2,156 - 2,163 meters (7,073 - 7,096 feet). The dive started with the ROV making multiple slow passes over the wreck in order to collect as many images as possible for the three-dimensional reconstruction. Once these passes were complete, the archaeologists, who had called in to participate in the dive, identified a number of artifacts that they wanted to see in zoomed-in detail. One of these items was an octant. An octant is generally an older version of a sextant which is used for navigation on the ocean. It was used for measuring the altitudes above the horizon and can usually measure to 90 degrees; whereas, the sextant can provide more accuracy because it can measure to at least 120 degrees. During the dive, scientists also observed biological fauna including shrimp, squat lobsters, sponges including glass sponges, urchins, sea stars, and brittle stars. Stay tuned for the dive summary for a more comprehensive list of the species observed.
With this dive complete, partners at the Bureau of Ocean Energy Management (BOEM) generated a three-dimensional reconstruction of the wreck using approximately 2,800 images and a dense point cloud consisting of over 18,000,000 points; you can find the three-dimensional reconstruction here . NOAA Ship Okeanos Explorer will be mapping overnight tonight during transit and once the mission team reaches the area of the new dive site, the team will pick a specific site to explore from the newly collected data. Follow along live!