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- Darelius, E., et al.
(author)
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Downward flow of dense water leaning on a submarine ridge
- 2007
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In: Deep Sea Research Part I. - : Elsevier BV. - 0967-0637 .- 1879-0119. ; 54:7, s. 1173-1188
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Journal article (peer-reviewed)abstract
- Large-scale dense bottom currents are geostrophic to leading order, with the main flow direction along the continental slope. Bottom friction makes the water descend to greater depths, but only at a small angle to the horizontal. Here the effect of a submarine ridge that intersects the slope is considered. It is shown that the presence of a submarine ridge greatly enhances the downward transport. By leaning against the ridge it is possible for the dense water to flow downhill, perpendicular to the depth contours, even though the first-order dynamics are geostrophic. The requirement for downward flow next to the ridge is that the frictional transport that it induces is sufficiently large to counteract geostrophic advection along the isobaths and out of the ridge region. The dynamics are similar to those of downward flow in submarine canyons, but ridges appear to be more effective in channeling the dense water downhill, in particular for narrow ridges/canyons with small seaward slope of the ridge/canyon axis. The downward flow is analyzed using a simplified analytical model and the results are compared to data from the Filchner Overflow, which agree qualitatively with the model.
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| 2. |
- Rebesco, M., et al.
(author)
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Quaternary contourite drifts of the Western Spitsbergen margin
- 2013
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In: Deep-Sea Research Part I-Oceanographic Research Papers. - : Elsevier BV. - 0967-0637. ; 79, s. 156-168
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Journal article (peer-reviewed)abstract
- The study of contourite drifts is an increasingly used tool for understanding the climate history of the oceans. In this paper we analyse two contourite drifts along the continental margin west of Spitsbergen, just south of the Fram Strait where significant water mass exchanges impact the Arctic climate. We detail the internal geometry and the morphologic characteristics of the two drifts on the base of multichannel seismic reflection data, sub-bottom profiles and bathymetry. These mounded features, that we propose to name Isfjorden and Bellsund drifts, are located on the continental slope between 1200 and 1800 m depth, whereas the upper slope is characterized by reduced- or non-deposition. The more distinct Isfjorden Drift is about 25 km wide and 45 km long, and over 200 ms TWT thick. We revise the 13 years-long time series of velocity, temperature, and salinity obtained from a mooring array across the Fram Strait. Two distinct current cores are visible in the long-term average. The shallower current core has an average northward velocity of about 20 cm/s, while the deeper bottom current core at about 1450 m depth has an average northward velocity of about 9 cm/s. We consider Norwegian Sea Deep Water episodically ventilated by relatively dense and turbid shelf water from the Barents Sea responsible for the accumulation of the contourites. The onset of the drift growth west of Spitsbergen is inferred to be about 1.3 Ma and related to the Early Pleistocene glacial expansion recorded in the area. The lack of mounded contouritic deposits on the continental slope of the Storfjorden is related to consecutive erosion by glacigenic debris flows. The Isfjorden and Bellsund drifts are inferred to contain the record of the regional palaeoceanography and glacial history and may constitute an excellent target of future scientific drilling. (C) 2013 Elsevier Ltd. All rights reserved.
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