Down to the Deep: NOAA's Serious Mapping Mission Makes for Fascinating Exploration

March 6, 2012

NOAA's National Geophysical Data Center researchers created this image and a related "flythrough" of the whole trench from bathymetry data archived in Boulder, Colo. More: http://bit.ly/GBjiBD. CREDIT: NOAA NGDC or NOAA National Geophysical Data Center [click image to enlarge]

Hollywood director James Cameron saw the deepest known spot on the ocean floor on March 25, 2012, when he made history by becoming the first solo diver to reach the bottom of the Mariana Trench, which is 6.8 miles (10,900 meters) below the surface.

Cameron and his colleagues have been on the tiny Pacific island of Guam for weeks, practicing dives in a submersible built to withstand crushing pressures. Cameron's goal is to be the third person in history to reach the deepest known point in the Mariana Trench, called the "Challenger Deep."

"Ninety percent of our oceans remain unmapped, so we don't really know where the deepest point is,"said Susan McLean with NOAA's National Geophysical Data Center (NGDC). "We know more about the surface of Mars than we do about our own seafloor."

McLean and her colleagues are trying to change that. McLean leads NOAA's Marine Geology and Geophysics Division , which part of NGDC and located incongruously in Boulder, CO., nearly 1,000 miles from the nearest ocean. Her team manages the Nation's seafloor data and helps create world-class maps of the ocean floor. Those maps are critical for tsunami modeling, mapping fisheries habitat, assessing coastal flooding risk, as well as for marine planning and protection.

The deepest known spot in the Atlantic Ocean is in the Puerto Rico Trench, north of the island. CREDIT: NOAA NGDC or NOAA National Geophysical Data Center. [click image to enlarge]

NOAA's geophysical data are also key to the effort to delineate the U.S. extended continental shelf. A country's continental shelf can extend beyond the normal 200-miles in some places if exacting criteria, including geophysical measures are met. The process involves accurate measurements of the shape, depth and composition of the sea floor. NOAA's NGDC-in collaboration with partners-compiles, archives, and makes accessible those data.

With a few clicks online, McLean can show a viewer exactly how quickly the sea floor drops off the coast of Puerto Rico; for example, steep curtains mark the end of a gentle underwater slope and the beginning of the sea floor's deep dive toward the Puerto Rico Trench, home to the deepest known spot in the Atlantic Ocean.

NGDC recently released a new method to explore these marine data and related models of the seafloor. NOAA's Office of Coast Survey collects data primarily for nautical charting to ensure safe and efficient maritime commerce. These data are available and depicted in relief with color-shading in the new map viewer.

"These are more than pretty pictures,"said Kelly Carignan, a digital elevation modeler at NGDC. "They are also critical data for modeling coastal flooding, from tsunami to hurricane storm surge."

Still, the data are fascinating to explore for those without an immediate need to navigate around an underwater seamount or prepare emergency evacuation routes. As part of NOAA's National Environmental Satellite, Data, and Information Service (NESDIS), McLean's group makes all data freely and publicly accessible, which makes possible innovative projects such as animated "fly-through" of the Mariana Trench ( See http://www.youtube.com/watch?v=PzdsRFwM9i8).

The first depth measurements of the Challenger Deep date back to the late 1870s, when ship crews used sounding ropes to come up with a measurement of 4,475 fathoms (~26,850 feet or 8,180 m).

Today, NOAA's mapping tools are far more sophisticated. Multibeam bathymetry, for example, uses echo sounding technology to bounce sound waves off broad swaths of the seafloor. From a ship, researchers with multibeam technology can gather data with tremendous precision, down to the centimeter level in shallow water. During three recent missions to gather data on the Mariana Trench region, NOAA and its partners at the Center for Coastal and Ocean Mapping (CCOM), pinned the depth of the Challenger Deep at more than 10,900 meters (35,750 feet or 6.8 miles).

Dr. Jim Gardner of CCOM, chief scientist on the extended continental shelf surveys of the Mariana Trench, estimates the error in the multibeam measurements of the bottom of Challenger Deep is about plus or minus 40 m (130 feet).

"The Mariana Trench is deeper than Mount Everest is tall,"McLean said.

For comparison, at least several thousand people have summitted Everest. Only two, so far, have traveled to the Challenger Deep-a Swiss engineer named Jacques Piccard and U.S. Navy Lieutenant Don Walsh, in 1960.

McLean admitted that she gets terribly seasick at the sight of open ocean. "So the videos and fly-throughs generated based on the observations of these scientist-explorers are the closest I and many others will come to getting to see the last frontiers on Earth."