Editorial Type:
Article
Article Type:
Research Article

Thermal Fronts Generated by Internal Waves Propagating Obliquely along the Continental Slope

Johannes R. Gemmrich Netherlands Institute for Sea Research, Texel, Netherlands

Search for other papers by Johannes R. Gemmrich in
Current site
Google Scholar
PubMed Close
and
Hans van Haren Netherlands Institute for Sea Research, Texel, Netherlands

Search for other papers by Hans van Haren in
Current site
Google Scholar
PubMed Close
Print Publication:
01 Mar 2001
DOI:
https://doi.org/10.1175/1520-0485(2001)031<0649:TFGBIW>2.0.CO;2
Page(s):
649–655
Restricted access

Abstract

Rapid temperature falls occurring at semidiurnal periods are observed close to the bottom above the continental slope in the Bay of Biscay. Simultaneous current measurements reveal that the abrupt temperature decrease O(0.5 K) within one minute is associated with a brief downslope current, contrary to previous observations. It is suggested that the flow field associated with internal waves propagating obliquely downslope is responsible for advecting denser water higher on the slope than lighter fluid, resulting in a gravitationally unstable stratification. The collapse of this stratification is observed as a thermal front passing the moored instruments.

Corresponding author address: Dr. Johannes Gemmrich, NIOZ, P.O. Box 59, 1790 AB Den Burg, Texel, Netherlands.

Abstract

Rapid temperature falls occurring at semidiurnal periods are observed close to the bottom above the continental slope in the Bay of Biscay. Simultaneous current measurements reveal that the abrupt temperature decrease O(0.5 K) within one minute is associated with a brief downslope current, contrary to previous observations. It is suggested that the flow field associated with internal waves propagating obliquely downslope is responsible for advecting denser water higher on the slope than lighter fluid, resulting in a gravitationally unstable stratification. The collapse of this stratification is observed as a thermal front passing the moored instruments.

Corresponding author address: Dr. Johannes Gemmrich, NIOZ, P.O. Box 59, 1790 AB Den Burg, Texel, Netherlands.

Save
Cover Journal of Physical Oceanography
Journal of Physical Oceanography

  • Armi, L., 1978: Some evidence for boundary mixing in the deep ocean. J. Geophys. Res.,83, 1971–1979.

  • De Silva, I. P. D., J. Imberger, and G. N. Ivey, 1998: Breaking of super-critically incident internal waves at a sloping bed. Physical Processes in Lakes and Oceans, No. 54, Coastal and Estuarine Studies, Amer. Geophys. Union, 475–484.

  • Dunkerton, T. J., D. P. Delisi, and M.-P. Lelong, 1998: Alongslope current generated by obliquely incident internal gravity waves. Geophys. Res. Lett.,25, 3871–3874.

  • Eriksen, C. C., 1985: Implications of ocean bottom reflection for internal wave spectra and mixing. J. Phys. Oceanogr.,15, 1145–1156.

  • Ivey, G. N., and R. I. Nokes, 1989: Vertical mixing due to the breaking of critical internal waves on sloping boundaries. J. Fluid Mech.,204, 479–500.

  • Munk, W. H., 1966: Abyssal recipes. Deep-Sea Res.,13, 207–230.

  • ——, and C. Wunsch, 1998: Abyssal recipes II: Energetics of tidal and wind mixing. Deep-Sea Res. I,45, 1977–2010.

  • Pingree, R. D., and A. I. New, 1989: Downward propagation of internal tidal energy into the Bay of Biscay. Deep-Sea Res.,36, 735–758.

  • Sherwin, T. J., 1991: Evidence of a deep internal tide in the Faeroe–Shetland channel. Tidal Hydrodynamics, B. B. Parker, Ed., Wiley and Sons, 469–488.

  • Thorpe, S. A., 1987: Currents and temperature variability on the continental slope. Philos. Trans. Roy. Soc. London,323A, 471–517.

  • ——, 1992: Thermal fronts caused by internal gravity waves reflecting from a slope. J. Phys. Oceanogr.,22, 105–108.

  • ——, 1997: On the interactions of internal waves reflecting from slopes. J. Phys. Oceanogr.,27, 2072–2078.

  • ——, 1999a: The generation of along-slope currents by breaking internal waves. J. Phys. Oceanogr.,29, 29–38.

  • ——, 1999b: Fronts formed by obliquely reflecting internal gravity waves at a sloping bottom. J. Phys. Oceanogr.,29, 2462–2467.

  • ——, and U. Lemmin, 1999: Internal waves and temperature fronts on slopes. Ann. Geophys.,17, 1227–1234.

  • White, M., 1994: Tidal and subtidal variability in the sloping benthic boundary layer. J. Geophys. Res.,99, 7851–7864.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 510 250 13
PDF Downloads 171 54 0