Satellite Derived Predicted Bathymetry: Essential Tool for UNCLOS 'article 76' on the extension of the legal continental shelf beyond 200 nautical miles
Walter Roest(1) , Martin Patriat(1) , Benoit Loubrieu(1) , Roland Vially(2) , and Samy Youssef(3)
(2) IFP, 1, Avenue Bois Préau, 92500 Rueil-Malmaison, France
(3) SHOM, 13 rue Chatellier, 29200 Brest, France
Article 76 of the United Nations Convention on the Law of the Sea (UNCLOS, Montego Bay, 1982) allows coastal states to claim a legal continental shelf extending beyond the 200 nautical miles that presently limits their exclusive economic zone (EEZ). As part of a claim submitted to the UN Commission on the Limits of the Continental Shelf (CLCS), coastal states have to demonstrate natural prolongation of their landmass and fulfill certain geomorphological and geological criteria. A number of geophysical and geological observations, needed to respond to these criteria, are laid out in Article 76, and further explained in the Scientific and Technical Guidelines published by the CLCS in 1999. Although these requirements present a tremendous opportunity for the acquisition of bathymetric, seismic (both reflection and refraction) and other data, the costs of such operations may be prohibitive, in particular for developing countries. Also, the time lines for data acquisition are relatively short as coastal states have a nominal 10 year period after ratification of the convention to complete their claims for an extended continental shelf. In fact, for a large number of states, the deadline is 2009, but others have more time. Satellite derived bathymetric data is therefore an essential tool for any outer continental shelf program: Firstly, due to its uniform coverage, it is a more coherent data set than those derived from ship tracks only (e.g. Gebco). For a preliminary study of potential extension, Etopo-2 provides results that are quite acceptable, and allow for an accurate planning of additional data acquisition. Secondly, given the hydrographic standards required by the CLCS, it may well be that for the determination of the foot of the slope in relatively deep areas (deeper than ~3000 m), the existing satellite derived bathymetric data approaches the quality needed to substantiate a legal shelf claim. A higher resolution satellite altimeter mission will surely help a significant number of countries in constituting their submission to the UN, in an efficient and cost-effective manner.