Oceanography The Official Magazine of
The Oceanography Society
Volume 32 Issue 04

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Volume 32, No. 4
Pages 174 - 183

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Radar Observations of Ocean Surface Features Resulting from Underwater Topography Changes

By Lisa Nyman , Björn Lund, Hans C. Graber, Roland Romeiser, and Jochen Horstmann 
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Article Abstract

The near-surface response to underwater topography changes is of great importance for navigational safety near regions of strong bathymetry gradients, such as around the islands of the Republic of Palau. There, mean underwater inclines can be as much as 25% of the horizontal distance, leading to a depth change of up to 85% within 26 km. Many processes associated with oceanic flows produce surface manifestations that are readily imaged from afar by synthetic aperture radar (SAR) or ship-based X-band Doppler marine radar (DMR). SAR and DMR imagery complement each other, with SAR providing a large-scale snapshot of the region on the order of 50 km or more and the DMR offering a mobile smaller-scale look at a particular area on the order of about 6 km with the ability to measure near-surface currents (1–5 m depth) in the vicinity of the ship. In this paper, we discuss the results from an analysis of thousands of DMR images around the islands of Palau. Three types of ocean surface features were identified: internal waves, surface slicks, and convergent fronts. Internal waves and convergent fronts are directly influenced by abrupt topography, and surface slicks can aid in the surface feature imaging process if their shapes are modulated by spatially varying surface currents. These ocean surface features are examined with respect to their associations with changes in the seafloor thousands of meters beneath them.

Citation

Nyman, L., B. Lund, H.C. Graber, R. Romeiser, and J. Horstmann. 2019. Radar observations of ocean surface features resulting from underwater topography changes. Oceanography 32(4):174–183, https://doi.org/10.5670/oceanog.2019.423.

References
    Alpers, W., and I. Hennings. 1984. A theory of the imaging mechanism of underwater bottom topography by real and synthetic aperture radar. Journal of Geophysical Research 89(C6):10,529–10,546, https://doi.org/10.1029/JC089iC06p10529.
  1. Alpers, W. 1985. Theory of radar imaging of internal waves. Nature 314(6008):245–247, https://doi.org/​10.1038/314245a0.
  2. Alpers, W., G. Campbell, H. Wensink, and Q. Zhang. 2004. Underwater topography. Pp. 245–262 in Synthetic Aperture Radar: Marine User’s Manual, C.R. Jackson and J.R. Apel, eds, US Department of Commerce, National Oceanic and Atmospheric Administration, National Environmental Satellite, Data, and Information Serve, Office of Research and Applications.
  3. Braun, N., F. Ziemer, A. Bezuglov, M. Cysewski, and G. Schymura. 2008. Sea-surface current features observed by Doppler radar. IEEE Transactions on Geoscience and Remote Sensing 46(4):1,125–1,133, https://doi.org/10.1109/TGRS.2007.910221.
  4. Carrasco, R., J. Horstmann, and J. Seemann. 2017. Significant wave height measured by coherent X-band radar. IEEE Transactions on Geoscience and Remote Sensing 55(9):5,355–5,365, https://doi.org/10.1109/TGRS.2017.2706067.
  5. Colin, P.L. 2009. Marine Environments of Palau. Indo-Pacific Press, 416 pp.
  6. da Silva, J.C.B., S.A. Ermakov, I.S. Robinson, D.R.G. Jeans, and S.V. Kijashko. 1998. Role of surface films in ERS SAR signatures of internal waves on the shelf: Part 1. Short-period internal waves. Journal of Geophysical Research 103(C4)8,009–8,031, https://doi.org/​10.1029/97JC02725.
  7. Gade, M., V. Byfield, S. Ermakov, O. Lavrova, and L. Mitnik. 2013. Slicks as indicators for marine processes. Oceanography 26(2)138–149, https://doi.org/​10.5670/oceanog.2013.39.
  8. Hovland, H.A., J.A. Johannessen, and G. Digranes. 1994. Slick detection in SAR images. Pp. 2,038–2,040 in Proceedings of IGARSS ’94, 1994 IEEE International Geoscience and Remote Sensing Symposium, https://doi.org/10.1109/IGARSS.1994.399647.
  9. Hühnerfuss, H., and W. Alpers. 1983. Molecular aspects of the system water/monomolecular surface film and the occurrence of a new anomalous dispersion regime at 1.43 GHz. The Journal of Physical Chemistry 87(25):5,251–5,258, https://doi.org/​10.1021/j150643a039.
  10. Kobayashi, K. 2004. Origin of the Palau and Yap trench-arc systems. Geophysical Journal International 157(3):1,303–1,315, https://doi.org/​10.1111/j.1365-246X.2003.02244.x.
  11. Lamb, K.G. 1994. Numerical experiments of internal wave generation by strong tidal flow across a finite amplitude bank edge. Journal of Geophysical Research 99(C1)843–864, https://doi.org/​10.1029/93JC02514.
  12. Lund, B., H.C. Graber, K. Hessner, and N.J. Williams. 2015a. On shipboard marine X-band radar near-​surface current “calibration.” Journal of Atmospheric and Oceanic Technology 32(10)1,928–1,944, https://doi.org/10.1175/JTECH-D-14-00175.1.
  13. Lund, B., H.C. Graber, H. Tamura, C. Collins III, and S. Varlamov. 2015b. A new technique for the retrieval of near-surface vertical current shear from marine X-band radar images. Journal of Geophysical Research 120(12):8,466–8,486, https://doi.org/10.1002/2015JC010961.
  14. Lund, B., B.K. Haus, J. Horstmann, H.C. Graber, R. Carrasco, N.J. Laxague, G. Novelli, C.M. Guigand, and T.M. Özgökmen. 2018. Near-surface current mapping by shipboard marine X-band radar: A validation. Journal of Atmospheric and Oceanic Technology 35(5):1,077–1,090, https://doi.org/​10.1175/JTECH-D-17-0154.1.
  15. Lyzenga, D.R. 1991. Interaction of short surface and electromagnetic waves with ocean fronts. Journal of Geophysical Research 96(C6):10,765–10,772, https://doi.org/10.1029/91JC00900.
  16. Nyman, L., B. Lund, R. Romeiser, H. Graber, and J. Horstmann. 2019. A new empirical approach to detect surface currents using Doppler marine radar. In Proceedings of the 2019 IEEE/OES Twelfth Current, Waves, Turbulence Measurement and Applications (CWTMA), IEEE.
  17. Senet, C.M., J. Seemann, and F. Ziemer. 2001. The near-surface current velocity determined from image sequences of the sea surface. IEEE Transactions on Geoscience and Remote Sensing 39(3)492–505, https://doi.org/​10.1109/​36.911108.
  18. Valenzuela, G.R. 1978. Theories for the interaction of electromagnetic and oceanic waves: A review. Boundary-Layer Meteorology 13(1–4):61–85, https://doi.org/10.1007/BF00913863.
  19. Wolanski, E., P. Colin, J. Naithani, E. Deleersnijder, and Y. Golbuu. 2004. Large amplitude, leaky, island-generated, internal waves around Palau, Micronesia. Estuarine, Coastal and Shelf Science 60(4)705–716, https://doi.org/10.1016/​j.ecss.2004.03.009.
  20. Wright, J. 1968. A new model for sea clutter. IEEE Transactions on Antennas and Propagation 16(2)217–223, https://doi.org/​10.1109/TAP.1968.1139147.
  21. Young, I.R., W. Rosenthal, and F. Ziemer. 1985. A three-dimensional analysis of marine radar images for the determination of ocean wave directionality and surface currents. Journal of Geophysical Research: Oceans 90(C1):1,049–1,059, https://doi.org/10.1029/JC090iC01p01049.
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