Topic outline

  • Issue: Calculate particle sedimentation in the ocean

  • Issue: Calculate and discuss particle sedimentation in the ocean

    •  The formula for Stokes sedimentation is now available in an excel sheet. Entering seawater and particle density, and temperature (viscosity depends on temperature), the sedimentation rate for each particle size can be calculated. It can also be output as a double-logarithmic graph. The yellow cells indicate where to enter numerical values in Excel, and the orange cells indicate where to output them.

       Each person should enter the size of the phytoplankton, the size of the phytoplankton community, the number of attached mineral particles, and the density, and calculate how fast the particles will sediment. Incidentally, the size of mineral particles deposited from the atmosphere to the ocean generally falls in the range of 1 to 5 μm in radius (the most common is about 2 μm).

    •  To calculate the sedimentation rate of the particles, we need to be given density data for the ocean. If you want to use actual density data, you can download it here. The results were observed at the 155°E line in the Northwestern Ocean during the Oshoro Maru oceanographic training (2016).

       Chlorophyll concentration is also available. We can estimate how much phytoplankton was actually distributed and at what depth. If the chlorophyll concentration is below 0.05 μg/L, it should be considered almost zero. (This is below the lower limit of quantitation for chlorophyll analysis.)

       All of the observation sites were at depths of about 5000 m. Some stations made CTD observations only down to 1000 m or 3000 m.

    • The Japan Association of Aerosol Science and Technology has sent out information on Aerosolpedia. The annual deposition of Asian dust in western Japan is reported to be 10 g m-2. This is quite a large amount because of its proximity to the Chinese continent. In the open ocean area of the Pacific Ocean, the amount may be about one-tenth of that. Also note that this is an annual deposition amount.

    • The shape and composition of organic particles collected in a sediment trap placed in the deep ocean were investigated, and they were assumed to be the feces of the large zooplankton, Salpa. Hydrocarbon composition was explored as an indicator substance for the fecal particles. This is a scatology paper.

    • This is a commemorative paper for the Okada Prize of the Oceanographic Society of Japan. Since it is a commemorative paper, it is written about this and that. The paper also uses the results of a sediment trap moored at St. KNOT in the Northwest Pacific Ocean (where the Oshoro Maru goes for oceanographic training).

      There may be some hints for you to consider in your report assignment.

    • Here is another paper by Mr.ONODERA (JAMSTEC): JAMSTEC continues to observe moored systems at Station K2 in the Northwest Pacific subarctic region. The data are analyzed.

    • This is an article by Prof. TANIGUCHI (now at Tokyo University of Agriculture and Technology), an alumna of the Faculty of Fisheries, Hokkaido University. The article includes a chapter titled "Plankton that want to sink".