Fieldwork during April/May 2006 north of Canada/Greenland:
OverviewDenmark ratified the United Nations Convention on the Law of the Sea (UNCLOS) in November of 2004. Article 76 of UNCLOS
(PDF-file) specifies a mechanism for extending the limits of the continental shelf beyond the 200 nautical mile exclusive economic zone (EEZ). After ratification of UNCLOS a country has ten years to collect the appropriate information and submit a claim for an extended continental shelf to the United Nations Commission on the Limits of the Continental Shelf (CLCS).
Out to a distance of 350 nautical miles or further, if Denmark can claim the Lomonosov Ridge as a natural prolongation of Greenland land territory, Greenland can exercise specified sovereign rights. These rights include the right to explore and exploit mineral and biological resources on and below the seabed and jurisdiction in matters related to environment and conservation.
Cooperation with Canada
Greenland (Denmark) is adjacent to Ellesmere Island (Canada), and both countries have the possibility of claiming the Lomonosov Ridge, a submarine mountain range, as a natural prolongation of their land territory (see map). Bathymetry, seismic and gravity data are needed to substantiate the claim. A co-operation between Canada and Greenland (Denmark) has been established to acquire the necessary data. Both countries will benefit from a joint plan for the investigation of the Lomonosov Ridge saving cost, sharing personnel resources and maximising the outcome of the data. A joint effort will also reduce the environmental impact by half. On June 27, 2005 representatives from Natural Resources Canada (NRCan) and the Geological Survey of Denmark and Greenland (GEUS) signed a Memorandum of Understanding (MOU) in Ottawa (see press release
Field work We are using the wide angle reflection/refraction technique with explosives as the sound source due to the restrictions imposed by the sea ice and due to the need to present strong arguments to CLCS. The seismic refraction method provides detailed information on the distribution and thicknesses of subsurface layers with characteristic seismic velocities down to a depth of approx. 40 km. In order to have sufficient information to make the case that the Lomonosov Ridge has a similar velocity structure as the polar margin, 11 shots per line need to be fired. The offset shots and the two furthest shots at the end of lines are 400 kg, and the middle shots are 200 kg. We will use Pentolite explosives, Primacord and detonators (Dyno Nobel), suspended 100 m underneath the ice. The sound after it has been reflected and refracted through the layers in the earth is recorded on 150 instruments (digital seismometers) on the sea ice. The recording instruments are small, weigh less than 5 kg, and are removed at the end of the experiment.
A plan for acquisition of seismic refraction data from the Canada/Greenland shelf out along the Lomonosov Ridge (approximately along the unofficial median line) has been drawn up, crossing over the bathymetric trough and also covering the area where the ridge abuts the shelf. Operations will be based in Alert
(see map and photo) with c. 30 people, adding a small emergency camp with three individuals in the middle of the working area for safety, fuel and explosives storage, and weather information. Transport of personnel and equipment out of Alert will be done by a Twin Otter and three helicopters dedicated to the project.
The map shows the planned lines (receiver line in white, shots in red). The white lines will be acquired in one season estimated to be 6 weeks from the beginning of April to early May. The data will be acquired with individual recording instruments spaced at 1.3 km over 200 km at a time, shooting at 11 locations for each of the three sections. The line along the Lomonosov Ridge is 400 km long, and will be acquired in two sections; the line crossing westwards is 200 km long and will be acquired in one section. The red dots off the end of the lines are offset shots.
The overall working sequence is:
- load all shots under the ice, ready for shooting (2 days)
- set out all 150 recording instruments (1 day)
- shoot all shots and collect receivers (2-3 days)
- acquire water depth and gravity reading at receiver sites (while loading shots for next section)
- download data and initiate for next section; which can take place while loading shots for next section.
A section should take 6 days and we are planning for one section per week. A bathymetry and gravity measurement will be made at every second position of the recording instruments, which will greatly aid the interpretation of the wide-angle reflection/refraction data. Operations will start at the end of March 2006 and hopefully be finished early May 2006.
In the Lincoln Sea region offshore North Greenland, the sea ice is several meters thick with little open water. This is due to the prevailing drift of the sea ice in the Arctic Ocean that causes the ice to pile up against the north-eastern islands of the Arctic Archipelago. The ice north of Ellesmere Island is the thickest in the Arctic Ocean and not even the Russian nuclear ice breakers can guarantee safe passage.
Movement of the sea ice can generate sound pressure levels as high as 180 db. The thick ice inhibits marine mammals such as whales from living in the region because there are no areas for them to surface. Biological productivity in the region is low due to the perennial ice cover. The experiment is planned for April 1 to mid May 15, 2006 after the long polar night when biological activity would be further reduced. The acquisition plan requires flying along the lines several times before any sounds are created, thus we will be able to assess if any seals or bear are on the sea ice and take appropriate mitigating actions.
NRCans Geological Survey of Canada - Atlantic, Halifax
Canadian Hydrographic Survey (CHS) of Fisheries and Oceans
Geological Survey of Denmark and Greenland (GEUS)
Royal Danish Administration of Navigation and Hydrography (RDANH)
Danish National Space Center