THE 2,500 METRE ISOBATH (CHAPTER 4) Harald Brekke

The role of the 2,500 m isobath The fixed points comprising the line of the outer limits of the continental shelf on the sea-bed, drawn in accordance with paragraph 4 (a) (i ) and (ii), either shall not exceed 350 nautical miles from the baselines ….. or shall not exceed 100 nautical miles from the 2,500 metre isobath, which is a line connecting the depth of 2,500 metres” (Paragraph 5, article 76)

Relevant bathymetric data Primary data: - Single-beam echo soundings - Multi-beam echo soundings Complementary data: - Bathymetric side-scan sonar measurements - Interferometric side-scan sonar measurements - Seismic reflection-derived bathymetric measurements (See 4.2.1 - 2) A classification of different geophysical data types that are relevant for the mapping and estimation of the thickness of marine sediments.

Ice-covered areas In special cases such as in ice-covered areas the CLCS may regard also the following as primary data: Seismic reflection-derived bathymetric measurements Interferometric side-scan sonar measurements (See 4.2.3)

Selection of points along 2,500 m isobath for delineating the 100 M maximum limit The 2,500 m isobath may occur as multiple repetitions along the continental margin Use the first 2,500 m isobath from the baselines that conforms to the general configuration of the continental margin, unless there is evidence to the contrary (See 4.4.2)