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Robert Rowland, United States Geological Survey (United States)
Ruth Jackson, Bedford Institute of Oceanography (Canada)
John Shimeld, Bedford Institute of Oceanography (Canada)
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Coastal states with continental margins that extend seaward beyond 200 nautical miles (nm) may use Article-76 of UNCLOS to substantiate their rights to the resources of the sea-bed and sub-soil. Article-76 stresses the "natural prolongation" across the continental shelf and margin. Sub-sea-bottom penetrating seismic systems are a primary tool to map this "natural prolongation" and to calculate the sediment thickness as set forth in Article-76 paragraph 4(a)(i). Seismic surveys are difficult to conduct in polar regions where the sea surface is permanently or seasonally covered by variable and unpredictable ice conditions, ice floes, ice ridges, icebergs, ice islands and ice shelves. This abstract examines the differences that may occur in polar regions, between pre-planned seismic survey lines and the lines that are actually collected. The latter may have data gaps and sinuous tracks even when the survey vessel is an ice-breaker using armored cables to tow depressor sleds that keep the air-gun arrays and seismic streamers beneath the surficial ice.
The 2007 Beaufort Sea seismic survey, from the Canadian icebreaker "Louis St-Laurent" brought these difficulties to the forefront. Long-term forecasts of regional ice conditions were used in planning the 4 survey lines with a total length 1300 nm and a spacing of 50 nm. In the Arctic summer of 2007, sea-ice had the least extent in nearly 30 years of observations. Forecasts and regional conditions, however, may not represent the local ice conditions encountered during the survey. The local ice environment is dependent on the type and amount of ice cover, width and direction of ice-free leads, visibility due to precipitation and fog, and the speed and direction of local winds and currents. Environmental regulations also produce breaks in data continuity. For example, if marine mammals are sighted within a kilometer of the survey ship, seismic operations are shut down. Extreme cold and condensation caused air-gun firing lines to freeze and air-gun pistons commonly froze to their chambers when lifted from seawater into below freezing air temperatures. All of these circumstances, plus impassable ice floes and ice ridges caused numerous gaps and course changes in the planned survey lines.
Article-76 does not take into consideration the practical difficulties of data collection in polar regions and the discontinuities that may result from cold and ice conditions. Of the 130+ states that actively participated in the UNCLOS negotiations, no more than 10%, face the problem of surveying in polar regions: in the Arctic - CA, DK, NO, RU and the USA; in the Antarctic - AR, CH, FR, NZ, NO and the UK. We suggest that the coastal state provide documentation, including satellite images and meteorological and other operational constraints that were encountered while the sailors and scientists made their "best effort possible" to collect the data for the extended continental shelf submission in ice-covered areas.
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