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Extended Continental Shelf Project

Office of Coast Survey

Office of Ocean Exploration and Research

NOAA-University of New Hampshire Joint Hydrographic Center

Mapping the Mysterious Arctic Sea Floor

Sea-floor Mapping, NOS Education

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What Lies Beneath: Mapping the Arctic Sea Floor

Arctic view from the U.S. Coast Guard Cutter Healy

Arctic view from the U.S. Coast Guard Cutter Healy.

On August 7, NOAA's Office of Coast Survey, in partnership with the NOAA-University of New Hampshire Joint Hydrographic Center and several other federal and Canadian partners, set sail on its fifth expedition to the Arctic Ocean to map the North American extended continental shelf.

What is the extended continental shelf and why are we mapping it? Well, the continental shelf is the gently sloping underwater fringe of a continent; the shelf ends with a steep drop off. Under international law, the boundaries of a nation’s continental shelf extend 200 nautical miles off the coast. However, if certain geological criteria are met, that shelf may extend even further out. And how much further out matters because coastal nations have sovereign rights over the natural resources of the seabed and subsoil within this shelf area.

Crew from the Healy lower echo sounding equipment into the Chukchi Sea during last summer's expedition.

In 2007, a NOAA-led mapping expedition some 600 nautical miles north of Alaska revealed evidence that the foot of the North American continental slope was much farther out than originally thought. So, this summer’s 41-day mission will build off 2007 research, collecting data to help develop a better understanding of the full extent of the continental shelf.

Researchers aboard the U.S. Coast Guard Cutter Healywill collect multibeam bathymetric data to map the sea floor. Healy will also clear a path through the ice for Canadian Coast Guard Ship Louis S. St-Laurent, which is well equipped to collect seismic data to determine sediment thickness.

In addition to its primary purpose of determining the full extent of the continental shelf, the data collected during the expedition will help scientists learn more about sea-floor processes, ocean circulation, sediment, ecosystems, and navigation safety.

Additionally, the expedition has a broader educational component. Joining the Healy is NOAA Teacher at Sea Christine Hedge, a teacher from Carmel Middle School in Carmel, Indiana. While on board, Hedge will interact with scientists, learning more about hydrography, as well as the ecosystems and resources that lie within the North American extended continental shelf. The knowledge and experience she gains on the mission will be carried back to the classroom.

The Arctic survey is part of a multi-year, multi-agency effort undertaken by the U.S. Extended Continental Shelf Project, led by the Department of State, with vice co-chairs from the Department of the Interior and NOAA. The 2009 mission continues the U.S.-Canada partnership begun last year, and plans are to continue joint operations in 2010. 

Continental shelf illustration

This illustration explains how a country can define its continental shelf. A country may use either constraint line to define the outer limits of its continental shelf: either 350 nautical miles seaward of the baseline, or 100 nautical miles seaward of the 2,500-meter depth contour (isobath). (EEZ: Exclusive Economic Zone, an area that extends 200 nautical miles offshore from the coastline.)