Physical Scientist, NOAA Okeanos Explorer Program
Elizabeth (Meme) Lobecker, a Physical Scientist with the NOAA Office of Ocean Exploration and Research (OER), is currently assigned to CCOM. She spends approximately 2-3 months per year offshore supporting the mapping efforts on the NOAA ship Okeanos Explorer.
Within the NOAA fleet, the Okeanos Explorer is, as the name implies, the only ship dedicated solely to exploring the ocean in the name of discovery and the advancement of knowledge. The unofficial motto of the ship and crew is “Always Exploring,” which for the onboard mapping team often translates into 24-hour data collection. And mapping using a state-of-the-art mulitbeam sonar is Meme Lobecker’s primary job when she’s onboard the 224-foot vessel.
“The EM 302 Kongsberg multibeam echosounder was chosen for its ability to explore nearly all of the global ocean’s depths as well as collect data about the contents of the water column. Because the ship is dedicated to ocean exploration and this sonar can map the seafloor from less than 100 to 7,000 meters, it’s ideal for most ocean basin water depths,” Lobecker says. “Last year, while transiting over the Mariana Trench en route to Indonesia, we had the opportunity to test the system’s maximum depth detection capability. The sonar detected the bottom at 8,000 meters, 1,000 meters deeper than the manufacturer’s spec.”
She notes further that by choosing a half-degree by one-degree system, the finest possible resolution is achieved due to the fact that the smaller the angle, the finer the data. And another plus for the EM 302 is that it is also capable of collecting water column backscatter data using the same beam that reads the bathymetry; the water column backscatter data is channeled into a different file.
The end result of all this is, of course, loads of data to cull through, clean up, and compile – a process Lobecker begins as soon as the data rolls in onboard the ship.
“When you collect multibeam data it’s not perfect. Sometimes you get fliers, or erroneous data points, and you have to clip them out, and we do all that in the field. We actually do most of the data processing while we’re at sea,” Lobecker says.
These fliers can be due to bad weather that sends bubbles down the hull of the ship and causes the sonar’s signal to bounce off the air bubbles instead of actually getting all way to seafloor and bouncing back. Bad data points can also occur when the angle the sonar hits a steep slope causing false bottom detection. Side-lobe detection, which happens when the sonar array locks onto the echo from minor lobes of sound on either side of the main signal, can also cause false bottom detection.
The good, the bad, and the quirky
But learning how to ferret out and filter these bad data points is all just part of the job, according to Lobecker.
“Every ship and every sonar has its own quirks and once you’ve looked at a lot of the data you come to know what to expect in terms of data artifacts. So, in the field we do the initial cleaning and, once that’s done, I come back here and look at the areas I expect we’re going to have problems. These might occur over features – like if you’re driving up and over a seamount – we often see data artifacts that need attention over seamounts.” She adds, “And this is one of the things we track. We do long-term troubleshooting so once we start to notice a pattern with these errors we provide feedback to manufacturer.”
Back at CCOM, Lobecker first checks the quality of the field processing, organizes the data into any logical sub areas, and then turns them into a standard suite of value-added products, including GeoTIFFs and IVS 3D Fledermaus objects, so that end users don’t have to deal with the raw data.
All of that all happens within three weeks of the end of a cruise, and then the data goes to the National Coastal Data Development Center. NCDDC generates metadata records, packages it all together with the hydrographic data, and sends it to the National Geophysical Data Center, which makes the data publicly available from their website (http://www.ngdc.noaa.gov/).
Metadata is information that actually describes the data itself; it gives the geographic extent of a file, the equipment used to collect the data, a little information about the specific project or cruise the data was collected on, why it was collected, and who to contact for further information.
Says Lobecker, “The metadata is designed to make data usable into the future, so that there’s a file associated with it that a person can read and understand the specifics of the data package.”
The concept of metadata came about in the late 1990s in step with the ever-growing wealth of mapping data being collected and an increase in web access and file sharing.
Multibeam in the blood
Back in 2001, Lobecker decided she wanted to go to graduate school for marine policy but knew she wanted to gain field experience before hitting the books. So she took a job in her hometown, Newport, RI, with a government contractor doing primarily shallow water hydrography. With a father who worked in the marine technology industry, multibeam was already in her blood and she stuck with it after finishing graduate school.
“So, I’m still doing the mapping but doing it for a different purpose. I’ve done a lot of commercial mapping work, too, for cable route surveys and pipeline inspections. I’ve worked in the North Sea and in the Mediterranean, but working for Office of Ocean Exploration and Research and seeing how the data is used by scientists for further exploration is far more interesting.”
In addition to mapping, the Okeanos Explorer’s work includes deploying remotely operated vehicles (ROVs) that conduct visual surveys of the seafloor. The ship is also telepresence-enabled meaning it can stream seafloor images and interviews from sea over standard Internet connections to bring the excitement of ocean exploration and discoveries live into classrooms, newsrooms, and living rooms in an effort to help raise ocean literacy.
Through half a dozen Exploration Command Centers located around the country, including one at CCOM/JHC, the telepresence capability allows scientists to be directly involved in the exploration of uncharted waters without being onboard the ship.
The technology was used most recently in the August 2011 cruise to the deepest part of the Caribbean Sea, where a team of international scientists both at-sea and on shore conducted interdisciplinary investigations of the Mid-Cayman Rise – an ultra-slow spreading center where two plates gradually move apart and upwelling magma creates new crust and the adjacent Cayman Trough.
“It was incredibly exciting being onboard for the Mid-Cayman Rise cruise. The scientists we partnered with on the ship and on shore were so enthusiastic about the data and the discoveries that were made,” Lobecker says.
The exploration was focused on oceanic core complexes and the hydrothermal vent communities that result. According to Lobecker, the immediate discoveries were biological in nature: the ROV footage shows the vents are home to an abundance of shrimp that are substantially different in appearance than those observed at the Mid-Atlantic Ridge vents, the first ever live tubeworm seen in the Atlantic, and the first ever observance of chemosynthetic tube worms and shrimp inhabiting the same vent site.
“Every night we would collect new multibeam data, and the next day’s ROV dive track would be planned based on that data. The seabed backscatter data proved very useful to determine likely sites for venting,” says Lobecker. She adds, “It’s the concept of ‘Doctor’s on Call’ that enables scientists who are interested in a particular area to be involved in the mission, to see and even direct where we map next and where the ROV dives next.”
And the Okeanos Explorer never rests. “Because we have the motto of always exploring, we’re always prepared to collect the multiple kinds of data we’re equipped for. We staff the ship for 24-hour mapping during transits. We watch data quality and if we see a problem due to weather or speed or some other factor, we’ll see if we can adjust the system or ship direction to improve the data quality – if there’s time.”
– David Sims