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Salinity on Earth

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  • Salinity on Earth

    For those who like a good read:

    Source: http://www.windows.ucar.edu/tour/lin.../salinity.html

    Dissolved salts in ocean water make it taste salty. Fresh water has dissolved salts in it too, but not nearly as many as ocean water! These dissolved salts can come from the land, precipitation, or the atmosphere, and are particles that have completely mixed in with the water.

    Ocean water is about 3.5% salt. That means that if the oceans dried up completely, enough salt would be left behind to build a 180-mile-tall, one- mile-thick wall around the equator! And more than 90 percent of that salt would be sodium chloride, or ordinary table salt. The oceans sure contain a lot of salt. How did that salt come to be there?

    All over the globe and from the top of the ocean all the way to the bottom of the ocean, salinity is between ~33-37 ppt or psu (average salinity of the ocean is 35 ppt). The image shown on this page shows salinity measured at the surface of the ocean across the globe. Almost the entire ocean is colored some shade of orange, corresponding to a salinity measurement around 33-36 ppt or psu.

    The oceans are naturally salty. Life in the oceans has adapted to this salty environment. But, most creatures that live in the ocean could not live in fresh water. When the salty waters of the ocean meet fresh water, an estuary is formed. This is a special environment where some creatures have learned to adapt to a mixture of fresh and salt water. Humans have the responsibility to make sure their actions are not causing damage to these special environments where life thrives. For more information on salinity, please use the links below...



    Salinity at the surface is high and then salinity decreases until a depth of about 1,000 meters. Salinity then increases again slightly with increasing depth.

  • #2
    Interesting reading, Edward--note the relationship between the thermocline & halocline Bob
    "There might be something to this ZEOvit"

    Comment


    • #3
      interesting stuff invincible... I saw a show on tv some time back about ocean gravity currents, can't remember the name but it was one of those discovery channel things with the cool CGI animation

      Anyway, while we're all having a salt lesson here are some snippets on gravity currents which make for interesting reading:

      from: http://cpt-gce.org/
      The CPT on Gravity Current Entrainment aims to develop parameterizations of dense gravity currents in the ocean for inclusion in climate models. Dense water formed through cooling or evaporation in marginal seas (e.g. Greenland-Iceland-Norwegian sea, Mediterranean Sea) or coastal shelves (e.g. Antarctic shelf) enters the general ocean circulation by flowing over topographic features including narrow channels (e.g. Denmark Straits, Gibraltar Straits) and down the continental slope. As the dense water descends it entrains ambient water, which mixes with the dense water, modifying the tracer properties and volume of the dense water. Present climate models do not have sufficient resolution to capture the small scale processes responsible for entrainment, and hence cannot correctly simulate the properties of the dense water masses which result, some of which (e.g. North Atlantic Deep Water, Mediterranean Overflow water, Antarctic Bottom Water) play very important roles in the large-scale ocean circulation. The goal of the CPT on Gravity Current Entrainment is to use knowledge gained from recent observations of dense overflows and laboratory and numerical process studies to improve the representation of dense gravity currents and their entrainment in climate models, thereby enhancing their ability to predict current and future climate.
      and another:
      Gravity currents and the release of salt from an inverse estuary

      G. W. Lennon, D. G. Bowers, R. A. Nunes, B. D. Scott, M. Ali, J. Boyle, Cai Wenju, M. Herzfeld, G. Johansson, S. Nield, P. Petrusevics, P. Stephenson, A. A. Suskin & S. E. A. Wijffels

      Spencer Gulf, South Australia, forms a remarkable natural system in which marine gravity currents are regularly observed. The most intense of these forms every autumn, when the gulf waters, which are of high salinity after summer evaporation, are cooled to the point where they are much denser than the waters on the shelf. They then slip out of the gulf along the sea floor to be replaced by a surface inflow of less saline shelf water. Here we report the first complete survey of this outflow during a period when salt exchange was both intense and well-defined. The gravity current has been traced across the floor of the continental shelf to the point where it cascades over the shelf break until it finds its own density level at a depth of 250 m. The speed of the current is estimated to be in the region of 0.1 ms-1, and at that rate it would have to flow for three months to remove the salt accumulated in the gulf during summer. There is evidence that the flow is unsteady in character, and is possibly released in regular pulses.
      rich.

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      • #4
        wow this takes me back to my oceanography class, we studied the exact same thing
        Nam

        Comment


        • #5
          This is a report I got from Fiji (SOPAC). They use a measuring system form Seabird Electronics, a US company which is located in Washington producing such instruments. The sensors of the system logs data in a selected time range while the instrument goes down in the depth.

          This is a typical graph coming from Fiji:



          The data for the above shown graph coming form the Seabird looks like this:

          * Sea-Bird SBE 19 Data File:
          * Software Version 4.234
          * Temperature SN = 2839
          * Conductivity SN = 2839
          * System UpLoad Time = Jan 08 2003 15:08:05
          ** Project:
          ** Latitude:
          ** Longitude:
          ** Time Switched On:
          * ds
          * SEACAT PROFILER V3.1b SN 2839 01/08/03 14:59:61.054
          * strain gauge pressure sensor: S/N = 193463, range = 1500 psia, tc = 52
          * clk = 32768.594 iop = 170 vmain = 11.0 vlith = 5.4
          * mode = PROFILE ncasts = 16
          * sample rate = 1 scan every 0.5 seconds
          * minimum raw conductivity frequency for pump turn on = 2000 hertz
          * pump delay = 15 seconds
          * samples = 10185 free = 76879 lwait = 0 msec
          * SW1 = C8 battery cutoff = 7.3 volts
          * number of voltages sampled = 4
          * logdata = NO
          * S>
          * cast 14 01/08 11:06:25 samples 7077 to 9796 sample rate = 1 scan every 0.5 seconds stop = switch off
          # nquan = 7
          # nvalues = 2720
          # units = specified
          # name 0 = depSM: Depth [salt water, m]
          # name 1 = t090C: Temperature [ITS-90, deg C]
          # name 2 = sal00: Salinity [PSU]
          # name 3 = sigma-t00: Density [sigma-t, Kg/m^3 ]
          # name 4 = oxsatMg/L: Oxygen Saturation [mg/l]
          # name 5 = seaTurbMtr: OBS, Seapoint Turbidity [FTU]
          # name 6 = flag: 0.000e+00
          # span 0 = -0.618, 247.560
          # span 1 = 19.3775, 30.8196
          # span 2 = 1.8459, 35.7987
          # span 3 = -2.6630, 25.4526
          # span 4 = 6.18589, 7.59774
          # span 5 = 0.000, 8.132
          # span 6 = 0.0000e+00, 0.0000e+00
          # interval = seconds: 0.5
          # start_time = Jan 08 2003 11:06:25
          # bad_flag = -9.990e-29
          # sensor 0 = Frequency 0 temperature, 2839, 21-Dec-01
          # sensor 1 = Frequency 1 conductivity, 2839, 21-Dec-01, cpcor = -9.5700e-08
          # sensor 2 = Extrnl Volt 0 oxygen, current, 230874, 17-Dec-01
          # sensor 3 = Extrnl Volt 1 oxygen, temperature, 230874, 17-Dec-01
          # sensor 4 = Extrnl Volt 2 seapoint turbidity meter, 315
          # sensor 5 = Pressure Voltage, 193463, 28-Dec-01
          # datcnv_date = Jan 08 2003 15:18:54, 5.25b
          # datcnv_skipover = 0
          # file_type = ascii
          *END*



          0.047 30.8196 33.4735 20.3013 6.19161 0.000 0.000e+00
          0.047 30.8146 33.6571 20.4404 6.18589 0.000 0.000e+00
          0.180 30.6143 34.1802 20.9011 6.18775 0.000 0.000e+00
          0.313 30.1730 34.3186 21.1563 6.22640 0.000 0.000e+00
          0.579 30.0602 34.4341 21.2814 6.23361 0.000 0.000e+00
          0.446 29.9473 34.5503 21.4070 6.24083 0.000 0.000e+00
          0.579 29.8342 34.6671 21.5331 6.24807 0.000 0.000e+00
          0.712 29.8072 34.6669 21.5421 6.25077 0.000 0.000e+00
          0.845 29.7445 34.7039 21.5911 6.25575 0.000 0.000e+00
          0.845 29.7197 34.7056 21.6009 6.25817 0.000 0.000e+00
          0.845 29.6876 34.7138 21.6179 6.26109 0.000 0.000e+00
          0.845 29.6598 34.7304 21.6397 6.26330 0.000 0.000e+00
          0.712 29.7583 34.6687 21.5600 6.25558 0.000 0.000e+00
          0.845 29.7984 34.6364 21.5222 6.25270 0.000 0.000e+00
          0.845 29.6956 34.7068 21.6099 6.26054 0.000 0.000e+00
          0.845 29.6313 34.7497 21.6639 6.26549 0.000 0.000e+00
          0.845 29.6305 34.7352 21.6533 6.26606 0.000 0.000e+00
          0.845 29.6210 34.7317 21.6539 6.26713 0.000 0.000e+00
          0.845 29.5889 34.7480 21.6770 6.26979 0.000 0.000e+00
          0.845 29.6283 34.7287 21.6491 6.26651 0.000 0.000e+00
          0.845 29.6656 34.6984 21.6138 6.26383 0.000 0.000e+00
          0.845 29.5655 34.7959 21.7208 6.27049 0.000 0.000e+00
          0.712 29.5749 34.7730 21.7004 6.27033 0.000 0.000e+00
          0.712 29.6750 34.7145 21.6227 6.26232 0.000 0.000e+00
          0.845 29.6341 34.7060 21.6302 6.26671 0.000 0.000e+00
          0.978 29.4820 34.8585 21.7960 6.27670 0.000 0.000e+00
          0.978 29.4344 34.8850 21.8319 6.28056 0.000 0.000e+00
          .
          .
          .
          The measurement was done with a Seabird SB19, some facts about it can be found on the companies homepage in the technical data sheet:

          http://www.seabird.com/products/spec...19plusdata.htm

          Many organisations, SOPAC, NOAA, ARGO are using this technology to get such analysis.

          Here are some further reading for example from ARGO about what they are doing:

          http://www-argo.ucsd.edu/

          G.Alexander

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          • #6
            Thnx. Alexander, the ARGO site is fascinating--an interesting educational & awareness organization Bob
            "There might be something to this ZEOvit"

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