LOMROG/APEX – Lomonosov Ridge off Greenland 2007

  See expedition's Logbook

The LOMROG expedition is focused on the virtually unexplored area of the submarine Lomonosov Ridge ca 350 km north of Greenland. With Swedish icebreaker Oden and support from a Russian nuclear icebreaker, LOMROG will acquire multibeam bathymetry, subbottom and seismic reflection profiles and gravity measurements. In addition to geophysical mapping, geological coring and oceanographic sampling will be carried out. The LOMROG project has two main scientific components:

1. Arctic Ocean paleoceanography/oceanography and glacial history
2. The tectonic evolution of the of the Arctic Ocean


Arctic Ocean glacial history and water mass exchanges between the Eurasian and Canadian basins
One of the reasons for targeting the ice-infested area north of Greenland is that it likely holds answers to key questions regarding the glacial history of the Arctic Ocean, such as whether immense ice shelves existed in the Arctic Ocean during past glacial periods. Previous expeditions to the Lomonosov Ridge with Oden in 1996 and the US nuclear submarine Hawkbill in 1999 (Jakobsson, 1999; Polyak et al., 2001), have demonstrated the occurrence of ice grounding down to 1000 m present water depth at about 87°N (Siberian side) on the Lomonosov Ridge crest. If this ice grounding event resulted from the much debated (e.g., Mercer, 1970; Hughes et al., 1977), but supposedly coherent and large floating ice shelf, the Lomonosov Ridge north of Greenland must also be scoured. To test the hypothesis of a huge Arctic Ocean ice shelf we will map the areas of the Lomonosov Ridge north of Greenland using the new multibeam bathymetry and subbottom profiling system to be installed on the Oden during the spring of 2007 (see below).
The oceanographic component of LOMROG will investigate the pathways of the Atlantic water and deep water across the Lomonosov Ridge between the Eurasian Basin and Canadian Basin. Such a pathway may exist between the Lomonosov Ridge and the Northern Greenland shelf. The knowledge of the shape of the seafloor in this area is therefore critical to this part of the project. The oceanographic work of LOMROG is an extension of work in 2005 when multibeam mapping was carried out from USCGC Healy and we found an overflow of deep water in a similar channel at the central part of the Lomonosov Ridge (Björk et al., submitted).


The tectonic evolution of the of the Arctic Ocean
A key to the tectonic evolution of the Arctic Basin, in particular pre-Gakkel Ridge spreading, is the nature and history of the Lomonosov Ridge. Based on the first continuous bathymetric profile across Lomonosov Ridge, Dietz and Shumway (1961) suggested that the ridge is a fault block rather than a volcanic construction. Subsequently Wilson (1963) envisaged the ridge to be a continental sliver rifted off the outer continental shelf of Eurasia between the northern Svalbard and Severnaya Zemlya during Late Paleocene to Holocene propagation of the Mid-Atlantic Ridge into the Arctic Ocean (e.g. Vogt et al., 1979). The unmapped connection to the Greenland/Canadian continental margin may play a crucial role in understanding the tectonic history of the Arctic Basin, in particular the first opening of the Eurasian Basin.
To gather the seismic data needed for the tectonic studies, the LOMROG project includes a reflection seismic component building on the successful legacy gained from previous Arctic Ocean seismic surveys using the icebreaker Oden. Seismic reflection profiles across the apparent gap between the northern Greenland margin and the Lomonosov Ridge will help to reveal how the ridge is linked to the margin.

Denmark’s Continental Shelf Project – United Nations Convention on the Law of the Sea
Following Denmark’s ratification in 2004 of the United Nations Convention on the Law of the Sea (UNCLOS from 1982), Denmark, Greenland and the Faroe Islands have a period of maximum 10 years to make claims beyond 200 nautical miles (NM) in five potential areas off Greenland and the Faroe Islands; one of them in the Arctic Ocean north of Greenland. Article 76 of UNCLOS is the key to future jurisdiction over resources on and below the seabed beyond 200 NM. The technical data needed for a submission to the Commission on the Limits of the Continental Shelf (CLCS) include geodetic, bathymetric, geophysical and geological data. In order to collect information in the Arctic Ocean GEUS has planned a series of projects where the tectonic component of LOMROG comprise one of them. Please visit the website of the Danish Continental Shelf Project on www.a76.dk.


Field Work
The ice conditions north of Greenland are among the toughest in the Arctic Ocean and the LOMROG geophysical/geological/oceanographic field work, organized by the Swedish Polar Research Secretariat (SPRS), will be carried out using Swedish icebreaker Oden together with a Russian nuclear icebreaker. Starting and ending in Longyearbyen on Svalbard the expedition will take place from mid August to mid September, 2007.

Lomrog planing maps

Intended cruise track for the LOMROG expedition. Red dots mark planned hydrographic stations, orange stars geological coring and the green line seismic reflection data acquisition. Rendezvous between icebreaker Oden and a Russian nuclear icebreaker is planned from about the red star.

 

New deepwater multibeam echo sounder and chirp sonar profiler to be installed on Oden


The concept of a multibeam sonar. A fan-shaped area of the ocean floor is simultaneously and continuously mapped. The width of the multibeam swath in modern deep-sea systems is typically >3-5 times the water depth. A multibeam system provides a high-resolution 3D-portrayal of the seafloor that unravels its true morphological characteristics.  A conventional echo sounder provides a 2D bathymetric profile along the path of the ship from a single beam (right).


Contact information
PIs
Martin Jakobsson
Department of Geology and Geochemistry, Stockholm University, 106 91 Stockholm, Sweden
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Christian Marcussen
Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 10, DK-1350 København K, Denmark
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References
Dietz, R.S. and G. Shumway, 1961, Arctic Basin Geomorphology, Geological Society of America Bulletin, 72, 1319-1330.
Hughes, T. J., Denton, G. H., and Grosswald, M. G., 1977. Was there a late Würm ice sheet? Nature, 266, 596-602.
Jakobsson, M., 1999, First high-resolution chirp sonar profiles from the central Arctic Ocean reveal erosion of Lomonosov Ridge sediments, Marine Geology, 154, 111-123.
Mercer, J.H., 1970. A former ice sheet in the Arctic Ocean? Palaeogeography Palaeoclimatology Palaeoecology, 8, 19-27.
Polyak, L., Edwards, M. H., Coakley, B. J. and Jakobsson, M., 2001, Ice shelves in the Pleistocene Arctic Ocean inferred from glaciogenic deep-sea bedforms, Nature, 410, 453-457.
Vogt, P.R., Taylor, P.T., Kovacs, L.C., and Johnson, G.L., 1979, Detailed aeromagnetic investigation of the Arctic Basin, Journal of Geophysical Research, 84, 1071-1089.
Wilson, J.T., 1963, Hypothesis of earth’s behavior, Nature, 198, 925-929.

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