Filament intrusions are observed in high-resolution temperature (T) measurements from a 100-m and several month-long mooring in the Fram Strait in around 400-m water depth at the continental slope West of Svalbard (Spitsbergen, Norway). In this dynamic environment, a wide variety of intrusive layers are observed with thicknesses between 5 and 80 m with warmer water between cooler waters above and below. The layers typically last from several hours up to 1 day, exceeding the local buoyancy period but not lasting as long as intrusive layers in the open ocean. The intrusions are a result of an intermingling of Arctic and North-Atlantic waters and generated in the basins interior and locally via internal wave steepening upon the sloping bottom. Freely propagating semidiurnal lunar internal tides cannot exist without background vorticity at these high latitudes. Strongly nonlinear turbulent bores are not observed at the tidal periodicity, but wave fronts occur at the sub-inertial frequency of dominant baroclinic instability. The fronts are in part associated with near-buoyancy frequency internal waves (breaking). The details of the moored T observations and their spectral content demonstrate the non-smooth, relatively turbulent development including convective overturning and shear-induced instabilities when intrusions disperse in presumably salinity-compensated isopycnal layers.
High-resolution temperature observations West Svalbard Poleward of critical lunar tidal latitude Intrusions High-frequency internal wave breaking Non-smooth isopycnal dispersal
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We thank the captain and crew of R/V Helmer Hanssen for their assistance. We greatly thank M. Laan for the design and construction of the NIOZ temperature sensors and assistance in mooring preparation. J. Greinert received support via COST Action ES0902 (PERGAMON) to join research cruises to acquire data. The research is also part of the Centre of Excellence: Arctic Gas Hydrate, Environment and Climate (CAGE) funded by the Norwegian Research Council (grant No. 223259). Request for data can be directed to email@example.com.
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