Bathymetry and oceanic flow structure at two deep passages crossing the Lomonosov Ridge

Abstract

Abstract. The Lomonosov Ridge represents a major topographical feature in the Arctic Ocean which has a large effect on the water circulation and the distribution of water properties. This study presents detailed bathymetric survey data along with hydrographic data at two deep passages across the ridge: a southern passage (80-81 • N), where the ridge crest meets the Siberian continental slope, and a northern passage around 84.5 • N. The southern channel is characterized by smooth and flat bathymetry around 1600-1700 m with a sill depth slightly shallower than 1700 m. A hydrographic section across the channel reveals an eastward flow with Amundsen Basin properties in the southern part and a westward flow of Makarov Basin properties in the northern part. The northern passage includes an approximately 72 km long and 33 km wide trough which forms an intra-basin in the Lomonosov Ridge morphology (the Oden Trough). The eastern side of the Oden Trough is enclosed by a narrow and steep ridge rising 500-600 m above a generally 1600 m deep trough bottom. The deepest passage (the sill) is 1470 m deep and located on this ridge. Hydrographic data show irregular temperature and salinity profiles indicating that water exchange occurs as midwater intrusions bringing water properties from each side of the ridge in well-defined but irregular layers. There is also morphological evidence that some rather energetic flows may occur in the vicinity of the sill. A well expressed deepening near the sill may be the result of seabed erosion by bottom currents.

Deposition History and Paleo‐Current Activity on the Southeastern Lomonosov Ridge and its Eurasian Flank Based on Seismic Data

“…The Lomonosov Ridge (LR) is one of the most prominent topographic features in the Arctic Ocean (Figure 1). It forms a large morphological barrier with a pronounced influence on ocean currents, which in turn influenced climate, sedimentation conditions, and even the setting of ecosystems in the adjacent Amundsen (AB) and Makarov Basins (MB, e.g., Björk et al., 2018; Jakobsson et al., 2007). In this respect, the tectonic evolution and subsidence history of the ridge, as well as the opening of the Fram Strait as a deep‐water connection to the North Atlantic are key constituents.…”

The International Bathymetric Chart of the Arctic Ocean Version 4.0

“…1). (a) Systematic multibeam surveys in 2014 by Swedish icebreaker Oden mapped a trough formed in the ridge crest, Oden Trough, and a critical sill depth influencing water exchange across the ridge 6 . In addition, lineations were mapped on the ridge crest, interpreted to be formed by a grounded ice shelf during the penultimate glaciation at about 140 000 years ago 37 .…”

“…A broad range of Arctic climate and environmental research, including questions on the declining cryosphere and the geological history of the Arctic Basin, require knowledge of the depth and shape of the seafloor 1 – 3 . Bathymetry provides the geospatial framework for these and other studies 4 and has impact on many processes, including the pathways of ocean currents and, thus, the distribution of heat 5 , 6 , sea-ice decline 7 , the effect of inflowing warm waters on tidewater glaciers 8 , and the stability of marine-based ice streams and outlet glaciers grounded on the seabed 9 – 11 . Bathymetric data from large parts of the Arctic Ocean are, however, not available or extremely sparse due to difficulties, both logistical and political, in accessing the region 12 .…”

“…8 ). Examples include surveys that have been individually published revealing critical sills that influence water exchange across the Lomonosov Ridge 6 , ice-shelf grounding on the ridge crest 37 , and where the foot of the slope is located along the ridge flanks, identified for the purpose of substantiating Denmark’s submission under Article 76 of the United Nations Convention on the Law of the Sea (UNCLOS) 38 .

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On the circulation, water mass distribution, and nutrient concentrations of the western Chukchi Sea

“…analyzed onboard using a laboratory salinometer (Autosal, Guildline Instruments). The calibration and processing procedures for the 2014 SWERUS-C3 data are described in Björk et al (2018).…”