Defining Canada's Extended Continental Shelf

The continental shelf is the submerged area subject to coastal State sovereign rights. UNCLOS provides a general framework for determining the outer limit of the continental shelf where it extends beyond 200 nautical miles. It grants sovereign rights for the coastal state to explore and exploit non-living and sedentary living resources of the continental shelf, and provides a general framework for international sharing of revenue from exploitation of the continental shelf beyond 200 nautical miles.

As a coastal state bordering three oceans, a significant part of the land to which Canada has the exclusive sovereign rights to explore and exploit is submerged land in the 200 nautical mile Exclusive Economic Zone (EEZ) (see red line in Figure). A provisional analysis using the rules of Article 76 of UNCLOS demonstrated that Canada has a large extended continental shelf in both the Atlantic and Arctic Oceans. (seewhiteline in Figure)

Article 76 of UNCLOS provides a complex formula for determining the outer limit of the continental shelf based upon geological and geomorphological characteristics of the seafloor. The continental shelf may not extend beyond 350 nautical miles (648 km) from the baselines from which the territorial sea is measured or, alternatively, not more than 100 nautical miles (185 km) beyond the point at which the seabed lies at a depth of 2,500 metres. A coastal State may select which of these rules it wants to apply in any given area. As a result, in some cases the shelf may extend beyond 350 nautical miles.

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In depth

The implementation of Article 76 of UNCLOS requires the analysis and interpretation of the shape of the seabed, depth of seafloor and thickness of the underlying sedimentary layer. These measurements result in two limits: the formula line, obtained by the application of distance formulas outlined in Article 76, and the constraining line, defining the maximum extend of the outer limit. Figure 1 shows a sketch of a continental shelf and margin. The starting point for the formulae line is the ‘foot of the continental slope (FOS)’, defined as the point of maximum change in the gradient at its base. The location of the line can be found from two formulae: a) a distance of 60 nm from the FOS, or b) the distance to a point where the thickness of the sedimentary layer is at least 1% of the distance to the FOS (Gardiner line). In constructing the combined formulae line, a coastal state may apply at any particular location that formula which is most advantages to its case.

Figure 1 - click here to enlarge

However, the formula line cannot extend beyond the constraining line, which is defined as the most seaward of a line 350 nm from the baselines of the coastal state, or a line 100 nm seaward of the 2500 m depth contour (Figure 2).

Figure 2 - click here to enlarge

To construct the final outer limit, a coastal state chooses at each point the most landward line from the constraining and the formula lines. The final outer limit is defined by straight line segments connecting the points, which cannot be further apart than 60 nm.

Canada's Submission

In 2004, the Federal budget allocated $69 million for Canada to carry out the mapping required to determine the outer limits of its continental shelf. This aimed to secure international recognition of the area where Canada has sovereign rights to explore and exploit natural resources of the seabed and subsoil of the continental shelf beyond our EEZ.

In 2008, an additional $40 million over four years was provided by the Government of Canada for data collection and legal work to enable Canada to present an effective submission to the UN Commission on the Limits of the Continental Shelf (the Commission).

The mapping in which Canada is currently engaged is a legally-established, orderly process. When this process is finished, the Commission will review Canada’s submission and make recommendations regarding the outer limit in accordance with its Scientific and Technical Guidelines. Canada will then establish the final and binding limits of its continental shelf on the basis of the Commission’s recommendations. It is important to note however that only the coastal state can establish the limits of its continental shelf.