Breaking the Ice

By Marcy Davis

The Canadian Coast Guard vessel Louis S. St-Laurent (front) and the US Coast Guard vessel Healy (back). Photo: Natural Resources Canada

Ice-breaking ships from Canada and the United States last week began a cruise to probe the Arctic Ocean in the continuation of a multi-year mission to survey—and possibly extend—each country's maritime boundaries. The ships departed from Barrow, Alaska, and from Kugluktuk, Nunavut (northern Canada), and are collecting data to build highly detailed three-dimensional maps of the sea floor that may be used to revise maritime boundaries.

The shaded area on this map illustrates where the U.S. is considering collecting and analyzing data and does not represent the official U.S. Government position on where it has extended continental shelf. This map is without prejudice to boundary depictions and future negotiations. Credit:

Dr. Larry Mayer of University of New Hampshire, who is also the co-director of the Center for Coastal and Ocean Mapping, is the chief scientist aboard the U.S. Coast Guard Cutter Healy. His team will map the seafloor using a sophisticated instrument called a multibeam sonar. From the hull of the ship, the sonar emits over one hundred narrowly focused beams of sound to create a swath that travels outward from the ship. Receivers ‘listen’ for the echo of the sound waves as they bounce off the seafloor and reflect back to the ship. Then computers calculate the depth to the seafloor and create a map of the sea floor topography.

The US Coast Guard icebreaker Healy cuts through one of the least known areas of the world--the Arctic. Source: NOAA

The Canadian Coast Guard Ship Louis S. St. Laurent will collect seismic data. Dr. David Mosher of the Geologic Survey of Canada will be the Canadian chief scientist.

The work is part of the Extended Continental Shelf Project, a joint effort to probe the Chukchi Borderland, an underwater promontory which extends north of Barrow, Alaska, into the Artic Ocean to near 80°N. The expedition aims to map the farthest reaches of the North American continent and determine the edge of the continental shelf, information that will be used as the countries ready their claims to extend their maritime boundaries past the current 200 nautical miles offshore mark, as allowed by the United Nations Convention on Law of the Sea. It is here that the U.S. stands to gain the most territory along with whatever natural resources it holds.

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).

Of particular interest to the U.S. claim is the 2,500 meter isobath, the depth upon which many of the mathematical limits and formulae defined in the treaty rely. Mayer’s team also looks for a feature called ‘the foot of the slope,’ a major change in the shape of the sea floor which, according to the treaty, may mark the limit of the U.S. extended continental shelf.  He and his colleagues have mapped more than a million square kilometers of seafloor since 2003.

An aerial view of the Chukchi Borderland from the north, with tracks from 2003, 2004 and 2007 mapping expeditions.

Many countries, including the U.S., will gain territory, although data analysis could take years. Once the United States senate officially accedes to the treaty, the U.S. will have ten years in which to turn over their data and formal claim to the U.N. Meanwhile, the Law of the Sea treaty protects the sea floor and underlying resources under stringent environmental laws.

Armchair sailors can monitor the cruise via several online sources, though transmission limitations in the Arctic Ocean may impact the number/frequency/size of these efforts.