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.
Highlights
The Arctic Ocean includes the northernmost loop of the global ocean circulation system
The multibeam data we have at hand together with the general morphology of the Lomonosov Ridge (LR) provided by Version 3.0 of International Bathymetric Chart of the Arctic Ocean (IBCAO), suggest a sill shallower than 1700 m somewhere south of 81◦15 N, 141◦30 E (Fig. 2a)
Our study suggests that the exchange flows across the LR have a rather different character in the southern and the northern passages
Summary
The Arctic Ocean includes the northernmost loop of the global ocean circulation system. Warm water from the North Atlantic flows through Fram Strait between Svalbard and Greenland and continues into the central Arctic Ocean basin as a warm core along the northern Barents Sea shelf slope (Fig. 1). Another branch of Atlantic water flows across the Barents Sea where it undergoes significant cooling by heat loss to the atmosphere before entering the central Arctic Ocean further east in the St. Anna Trough (Schauer et al, 2002). Several warm pulses on decadal scales have been observed, as well as sudden changes in the core temperature (Dmitrenko et al, 2009; Woodgate et al, 2001)
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