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Cruise ANTARKTIS XI114 of RV Pol

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					Cruise ANTARKTIS XI114
of RV "Polarstern" in 1995:
CTD-Report


   Sildam
Jür




Ber. Polarforsch. 178 (1995)
ISSN 0176 - 5027
Contents


1 Introduction

2 Instrumentation

3 Data Processing

4 CTD Profiles

5 Sections

6 Similarity of non dimensional density profiles
7 References
Introduction


The report presents the results of the CTD measurements carried out in the
Bellingshausen Sea    - an area rare of CTD measurements. The main part of the
report consists of the brief description of the CTD data acquisition and
processing routines, the vertical profiles of temperature, salinity and density, and
of the plots of the distribution of these properties along the hydrographic
sections. The final part of the report deals with the notably similar structure of the
vertical density distribution at different locations if presented as a function of a
non dimensional vertical C;-ordinate.    It is pointed out that such a distribution
could be an asymptotic limit of stationary mixing along neutral surfaces,
Tab. 1: The list of CTD Stations

Station AWI-No     Date      Start Max depth Latitude Longitude Water Meas.
                            (UTC) (UTC)      Deg. min Deg. min Depth Depth
   -100             -95         -90                 -85             -80
                           W Longitude /deg


Figure 1. Positions of CTD stations during ANTXIIl4 cruise of R N "Polarstern".
Instrumentation



Hydrographie casts were occupied by 24        -   place General Oceanic Rosette
equipped with 12 - litre bottles and Sea-Bird 91 1 plus (SB) CTD. SB had a single
temperature (pressure protected thermistor), a Paroscientific Digiquartz pressure
and a conductivity Sensor. Flow pumped at a constant rate via TC duct ensured
that the conductivity and temperature sensors measured the Same water with a
fixed time difference. Initial accuracies of measurements as provided by SB
specifications were for conductivity 0.0003 Slm, for temperature 0.002 ' C and for
pressure 0.0150h    of full scale (here 6800 dbar). The temperature and
conductivity sensors were calibrated prior to and after the cruise. Checks of CTD
temperature and salinity values versus reversing thermometers and salinity
                         n
bottle values (analysed O Guidline Autosal 8400 salinometer) respectively were
performed at the deep CTD stations.
Data Processing


Data acquisition and processing was carried out according to standard routines
of Sea Bird 911 1 CTD data processing. It consisted of the following steps: 1)
converting of the raw data to pressure, temperature (IPTS-68) and conductivity;
2) aligning of conductivity relative to pressure by -0.01 seconds which was

            n
determined O the basis of experience from previous cruises (Budeus 1995,
personal communication); 3)         conductivity cell thermal       mass correction
(alpha=0.03 and 1/beta=9.0); 4) low pass filtering of pressure with a time
constant of 0.15 seconds; 5) removal of the scans where the CTD was travelling
backwards; 5) averaging of data into 2 dbar bins. Finally, salinity (PSS-78) and
density were calculated.


Comparison of the CTD temperature with the reversing thermometers showed
that the differences at the deep stations did not exceed the accuracy of the
reversible thermometers i.e. 0.002 'C. Comparison of the pre- and postcruise
calibration results showed that drift of the temperature Sensor between the two
calibrations carried out in March 02 and July 29, was less than 0.001 'C. So, no
corrections for temperature measurements were introduced.


Comparison of the CTD salinity measurements with the salinity bottle values,
taken at the deep stations showed the existence of a mean shift of 0.0033 with
the higher values of the bottle salinities. No statistically significant time trend was
observed. Introducing the postcruise calibration slope with the precruise
calibration coefficients resulted in the increase of salinity of the CTD data on an
average by 0.0034. Thus salinity was calculated using the precruise calibration
coefficients and the slope determined from the postcruise calibration as
suggested by an application note of SBE.
4 CTD Profiles


On the following pages the CTD profiles from all hydrographic stations are
displayed. To provide the possibility of comparision of the profiles with each
other, the Same scale has been used for all profiles. For this reason, the shallow
CTD casts (200-600 m) that have been carried out additionally to the deep ones
at some stations to satisfy the water requirement of the different groups are not
shown in the present report.
                           Station: 1                        ANT XI114           1995

                                                   Density, sigma-t / kg/m**3



                                              Potential Temperature /deg C




            . .. .   . ,   .       Density                                                                          -
        -
            -   -                  Salinity
                                   Temperature
                                                                                                                    -
5   0   O        0             -     l   l     l     l   l   1   l   l   l   l   1   l   l    l     l   l   l   1   l   -
    33.0                                     33.5                    34.0                    34.5                   35.0
                                                             Salinity
                   Station: 2               ANT XI114           1995

                                   Density, sigma-t / kg/m**3



                                   Potential Temperature /deg C
      -       2    -     1        0 1 2 3 4 5 6 7                           8         9       1    0
  0




                                                                                                       7
                                                                                                       (D
                                                                                                       0-l
                                                                                                       W
                                                                                                       C
                                                                                                       (D




                       Density
              --   -   Salinity                                                                   -
                       Temperature
          -                                                                                       -
5000     I         I    I    I      ~   I    I   I      I   ~    I     I 1 I 1   I1       1   1
    33.0                     33.5                34.0                  34.5                       35.0
                                            Salinity
                         Station: 3                 ANT XI114          1995

                                          Density, sigma-t / kg/m**3



                             Potential Temperature ldeg C
    - 2 - 1 0 1 2 3 4 5 6 7                                                                 8           9       1        0
  0 m , . l .l. . l I , , , , l , l 1 , I l [ I , ,
          ,                    , ,
                          ..
     -                                                                                                                  -
                                                                                                                        -
       -

1000   -                                                                                                                -
       -                                                                                                                -
       -
                                                                                    \
                                                                                        \
                                                                                                                        -
                                                                                                                             -Å
2000 -                                                                                          \
                                                                                                                        -    8
                                                                                                                             Ÿ
     -
       -
                                                                                                                        -    2
                                                                                                                        - Q.
       -                                                                                                                - 8
                                                                                                                          0"
3000 -                                                                                                                  - (U
     -                                                                                                                  -
       -

                                                                                                                        -
4000   -                                                                                                                -
           , . .   ....    Density
           - - - Salinity                                                                                               -
                           Temperature
       -                                                                                                                -
5000     I           I     I     I    I     I   I   I   I    1 1   1   1   1    1           1       1       1       1
    33.0                             33.5                   34.0               34.5                                     35.0
                                                    Salinity
                   Station: 5               ANT XI114           1995

                                   Density, sigma-t 1 kg/m**3




                                   Potential Temperature Ideg C
      -       2    -     1        0 1 2 3 4 5 6 7                                             8           9       1        0
  0                          ..                                                               l l l l l l l l l l l l ,
          -                                                                                                           -
                                                                                                                      -

     -                                                                                                                -

1000 -                                                                                                                -
                                                                      1
                                                                      '
          7                                                               \                                           -
                                                                              \
          -                                                                       \                                   -
                                                                                      \
                                                                                          \



2000 -
          -
                                        1                                                     \
                                                                                                  \
                                                                                                                      -
                                                                                                                      -
                                                                                                                               W
                                                                                                                               (D
                                                                                                                               0)
                                                                                                                               0)
     -                                                                                                                -        5
                                                                                                                               (D
          -                                                                                                           -
                                                                                                                               Q.
          -                                                                                                           -        s.
                                                                                                                               er
3000 -                                                                                                                - &)
     -                                                                                                                -

          -
                                                                                                                      -
4000      -                                                                                                           -
          - ..... ..   Density                                                                                        -
          ----         Saliniiy                                                                                       -
                       Temperature
          -                                                                                                           -
5000     I         I    I    I      ~   I    I   I      I   ~     I           I           I           I       ~        I            I   I   I
    33.0                     33.5                34.0                         34.5                                     35.0
                                            Salinity
                         Station: 6                                ANT XI114           1995

                                                   Density, sigma-t Ikg/m**3




                                            Potential Temperature Ideg C
       -        2         -       1        0 1 2 3 4 5 6 7                                                  8        9       1       0
  0                                   ..
                                               ,   .
           -
           -                                                                                                                     -
           -                                                                                                                     -
1000 -
                                                                                           \
           -                                                                                                                     -
                                                                                               \
           -                                                                                        \                            -
                                                                                                        \
                                                                                                        \
           -                                                                                                                     -
2000
     -1                                                    /                                                \\                   -   ?
                                                                                                                                     Ÿ
                                                                                                                                     0
           -
           -
                                                                                                                                 -   C
                                                                                                                                 - Q.
           -                                                                                                                     - 8
                                                                                                                                     er
3000 -                                                                                                                           -F
                                                                                                                                 -
       -

4000   -                                                                                                                         -
       -       ... ....       Densiiy
       - - - - Saliniiy                                                                                                          -
                              Temperature
       -                                                                                                                         -
5000     l           l        I   l        1           1       1    11    /    1   1   1   1    1           1    1       1   1
    33.0                               33.5                              34.0                  34.5                              35.0
                                                                   Salinity
        Station: 7             ANT XI114             1995

                        Density, sigma-t Ikg/m**3



                       Potential Temperature Ideg C
-   2   -    1     0      1   2      3       4   5    6     7   8   9   1   0




            Salinity
            Temperature




                                  Salinity
                  Station: 8                  ANT XI114           1995

                                     Density, sigma-t 1kg/m**3



                               Potential Temperature Ideg C
     -       2     -       1   0 1 2 3 4 5 6 7                                    8      9       1        0
 0                                                                          l l l l l l l l l l l l ^ ~
                                                                                                     -
                                                                                                     -
                                                                                                     -
                                                                                                     -
                                                                    \
                                                                        \
                                                                            .
                                                                            '                        -




                 ...   Density
             -    - Salinity                                                                         -
                       Temperature
         -                                                                                           -
5000     ~             l         l        l        ~          l     ~            ~           ~            ~   ~   ~   l   l
    33.0                       33.5                    34.0                 34.5                     35.0
                                               Salinity
                   Station: 10              ANT XI114          1995

                                  Density, sigma-t 1 kg/m**3



                             Potential Temperature Ideg C
    - 2 - 1 0 1 2 3 4 5 6 7 8 9 1 0
  0  l l l l ~. ' .r. l l. .~ .~ m i ~ I . ~ I 1 1 1 1 I I l l l l ll ~ l ~l Il l l l l l l f l
             .                                                        l

                                                     \                                        -




          - - - Salinity                                                                     -
                     Temperature
      -
5000     1     1     1   1    1     1   1   1   I    1 1   1   1   1 1       1   1   1   1
    33.0                     33.5                   34.0              34.5                   35.0
                                            Salinity
                  Station: 11                 ANT XI114      1995

                                      Density, sigma-t Ikg/m**3



                                      Potential Temperature Ideg C
     -       2        -     1        0 1 2 3 4 5 6 7                                       8       9   1        0
 0
         -
         -                                                                                                  -
         -
1000 -                                                                                                     -
                                                                  \
         W                                                            Si                                    -
                                                                           \
         -                                                                     \
                                                                                   \
                                                                                                           -
                                                                                       \
         -                                                                                                 -
                                                                                           \                -0
2000 -                                                                                         \           -8
                                                                                                            cn
         -

         -
                                                                                                           -    3
                                                                                                           - Q.
                                                                                                           - $
                                                                                                                er
3000 -                                                                                                     - &>
     -                                                                                                     W




                                                                                                           -
                                                                                                           -
4000 -                                                                                                     -
         - . ......       Density
         --   -           Salinity
                                                                                                           -
                          Temperature
     -                                                                                                     -
5 0 0 0 ~ 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
   33.0      33.5      34.0       34.5      35.0
                                             Salinity
                     Station: 12                ANT XI114           1995

                                   Density, sigma-t / kg/m**3




                                      Potential Temperature /deg C
    - 2 - 1 0 1 2 3 4 5 6 7                                                                      8           9       1        0
  0 r l 1 1 1 1 , ,.,I . . 11 .1 . 1. .1 . L , 1
                                                                                                                             -
       -
       -                                                                                                                     -

1000   -                                                                                                                     -
                                                                        \
       -                                                                    \                                                -
                                                                                s.
       -                                                                             \
                                                                                                                             -
                                                                                         \
                                                                                             \
                                                                                                                             -
2000   -                                /
                                                                                                 \
                                                                                                     \                       -:   W
                                                                                                                                  W
       -                                                                                                                          C
                                                                                                                             -    (D
       -
                                                                                                                             - Q.
       -                                                                                                                     -    i?.
                                                                                                                                  0"
3000 -                                                                                                                       -    su
       -
       -                                                                                                                     -
       -
4000 -                                                                                                                       -
           . ..   ....   Densiiy                                                                                             -
       - - - - Salinity                                                                                                      -
                         Temperature
       -                                                                                                                     -
5000     I           I    I    I    ~       I     I   I      I   1 ~1   II           1 1                 1       1       1
    33.0                      33.5                    34.0                      34.5                                         35.0
                                                Salinity
             Station: 13           ANT XI114           1995

                           Density, sigma-t 1 kg/m**3
    26                       27                        28             29


                        Potential Temperature ldeg C
    -    2   -    1    0 1 2 3 4 5 6 7 8 9 1 0
0                       ..            l l I U I I I I ~ ! ~ ! ! ! ! ~ ! ! ! i j ! ~
                                                '-Â¥




                 Densiiy




                                   Salinity
            Station: 14       ANT XI114         1995

                      Density, sigma-t 1 kg/m**3



                     Potential Temperature Ideg C
    -   2   -   1   0 1 2 3 4 5 6 7                    8   9   1   0
0                          llllllllll'~1,1ll
                                            \
                        Station: 17                           ANT XI114          1995

                                                 Density, sigma-t 1 kg/m**3




                                            Potential Temperature ldeg C

  0
       -

           -
               2 - 1
           ~ 1 1 1 1 , [ . ., ., , I ., ,
                                   .        .,   ,,,, ,
                                            0 1 2 3 4 5 6 7
                                                  ..
                                                                                                        8           9       1

                                                                                                                                -
                                                                                                                                    0


           -                                                                                                                    -
           -                                                                                                                    -

1000 -                                                                                                                          -
                                                                                  \
           -                                                                                                                    -
           -                                                                                \                                   -
                                                                                                \
                                                                                                    \
           -                                                                                                                    -
                                                                                                                                        -Å
2000 -                                                                                                      \                   -       8
                                                                                                                                        Co
           -                                                                                                                    -
                                                                                                                                        2
           -                                                                                                                    -    \
                                                                                                                                        Q.
                                                                                                                                -       8
                                                                                                                                        er
3000       -                                                                                                                    -W
           -                                                                                                                    -
           -                                                                                                                    -
           -                                                                                                                    -
4000       -
           - . . . . . . . Density                                                                                              -
             - - - Salinity                                                                                                     -
                             Temperature
           -                                                                                                                    -
5000     I              I       I       I         ~       I    I   I     I   ~    I     I               I       I       ~       I        I   I   I
    33.0                                33.5                       34.0                 34.5                                    35.0
                                                              Salinity
        Station: 19            ANT XI114      1995

                       Density, sigma-t Ikg/m**3



                      Potential Temperature Ideg C




 ....      Densiiy
           Salinity

L-         Temperature




                               Salinity
                  Station: 21                 ANT XI114          1995

                                   Density, sigma-t / kg/m**3



                              Potential Temperature /deg C
    -       2     -     1    0 1 2 3 4 5 6 7                                                  8                9   1       0

        -                                                                                                              -
                                                                                                                       -


1000 -
        -                                                            \
                                                                         's
                                                                                                                       -
                                                                              \
        -                                                                         \                                    -
                                                                                      \
                                                                                          \                            -
        -
                                                                                              \                         -0
2000 -                                                                                                                 -$
                                                                                                  \                     0)
     -                                                                                                \                -
        -                                                                                                 l            -
                                                                                                                               Q-
        -                                                                                                 \            -       8
                                                                                                           \                   0"
3000 -                                                                                                        l
                                                                                                                       -       su
     -                                                                                                        l        -
                                                                                                              I        -
                                                                                                              I        -
                                                                                                              I
4000    -                                                                                                     I        -
                                                                                                              I
            -   - - Sal nity                                                                                  1        -
        -
                       Teriperature                                                                           1        -
                                                                                                               I

5000     l         l     l     l     ~    l      l       l   l   ~            l           l                    l   l I ~            l   l   ~
    33.0                     33.5                    34.0                         34.5                                 35.0
                                              Salinity
Station: 23          ANT XI114       1995

             Density, sigma-t Ikg/m**3



            Potential Temperature Ideg C




  Density




                    Salinity
                      Station; 26                ANT XI114          1995

                                        Density, sigma-t 1 kg/m**3



                                       Potential Temperature Ideg C
      -       2       -       1       0 1 2 3 4 5 6 7 8 9 1 0
  0                                                               !!!!!!!!!u4~llll
                                                                                                   -




                          Density
          - - - - Salinity                                                                         -
                          Temperature
          -                                                                                        -
5000     1        1       I       I      ~   I    I    I     I   1 ~1   1 1
                                                                        I          I   I   1   1
    33.0                              33.5            34.0                  34.5                   35.0
                                                 Salinity
                       Station: 28                    ANT XI114          1995

                                         Density, sigma-t Ikg/m**3




                                         Potential Temperature Ideg C
       -       2       -       1        0 1 2 3 4 5 6 7                                      8                    9     1         0
  0                                                                                      l                          !         ~            ~   ~   \   ~
           -                                                                                                                  -
           -
           -                                                                                                                  -
1000       -                                                                                                                 -
           -
                                                                             \
           -                                                                     \
                                                                                     \                                       -
                                                                                         \
           -                                                                                 \                               -
2000 -
                                                                                                 \
                                                                                                 \
                                                                                                                             -        ?
                                                                                                                                      Ÿ


           -
                                                                                                     \                                Ÿ


                                                                                                         \                   -        2
           -                                                                                                 \               - Q.
                                                                                                              l              -        s.
                                                                                                                                      0"
3000       -                                                                                                   l             - CU
           -
                                                                                                               l
                                                                                                                I
                                                                                                                I            -
                                                                                                                I
           -                                                                                                   l             -
4000
                                                                                                               I
                                                                                                              I              -
           -                                                                                                  I
                           Ternperature
           -                                                                                                  I              -
5000    I          I       I       I     ~    I   I     I   I    ~   I   I   :           I           I              \ I II
    33.0                               33.5                 34.0                 34.5                                         35.0
                                                      Salinity
                      Station: 30                    ANT XI114           1995

                                            Density, sigma-t Ikg/m**3



                                            Potential Temperature Ideg C
       -        2         -        1       0 1 2 3 4 5 6 7                                           8               9       1        0
  0
           -                                                                                                                      -
           -
           -                                                                                                                      -
1000       -                                                                                                                     -
                                                                             \
           -                                                                     \                                                -
                                                                                     \
           -                                                                             \
                                                                                                                                  -
                                                                                             \
                                                                                                 \
           -                                                                                                                      -
                                                                                                     \
                                                                                                         \                            n
2000 -                                                                                                       I
                                                                                                                                 -8   Ÿ
           -                                                                                                                          C
                                                                                                                                 -    ro
           -
                                                                                                                                 - Q.
           -                                                                                                                     -    g.
                                                                                                                                      a-
3000 -                                                                                                                           - W>
     -                                                                                                                           -
           -                                                                                                                     -
           -
4000       -                                                                                                                     -
               ... ....       Densiiy                                                                                            -
           - - - - Salinity                                                                                                       -
                              Ternperature
           -                                                                                                                      -
5000     I            I        I       I     ]   I   I    I      I   ~   I           I           I               I       ~       I        I   ~   I
    33.0                               33.5                   34.0                       34.5                                     35.0
                                                     Salinity
                   Station: 32                 ANT XI114                1995

                                  Density, sigma-t Ikg/m**3




                                  Potential Temperature Ideg C
    -       2      - 1 0 1 2 3 4 5 6 7 8 9 1 0
0                    l ~ l. .l . l . l. ,~ l l l l ~ l l l l ~ l l l l ~ l l~l .l 4l -~ ~ l- ^ l l l ~ l l l
                                                                                       LU
                                                                    \




            ...,




        E   --     -   Salinity
                       Ternperature




                                               Salinity
              Station: 37              ANT XI114          1995

                               Density, sigma-t Ikg/m**3




                              Potential Temperature ldeg C




4000




5000
       1-
       . . ....,




    33.0
              I
                   Density
                   Salinity
                   Temperature

                   I    I      /
                            33.5
                                   I   I   I      I
                                               34.0
                                                      ~   I   I    I 1 I 1 ~1
                                                                  34.5
                                                                                1
                                                                                    -
                                                                                    -
                                                                                    -

                                                                                    -

                                                                                    35.0
                                       Salinity
                    Station: 45              AMT XI114       1995

                                    Density, sigma-t / kg/m**3




                                    Potential Temperature ldeg C
     -       2      -    1         0 1 2 3 4 5 6 7                                       8           9 1 0
 0       ~                     ~   .,,,, .I. , [  ~                  ~                                ll~llll
                                                                                                         ~            ~       ~




                                                                                                             -
                                                                                                             -
                                                                                                             -
                                                                 \
                                                                     \                                       -
                                                                         \
                                                                             \
                                                                                 \
                                                                                                             -
                                                                                     \
                                                                                         \                   -
                                                                                             \                   -Å
                                                                                                 \           -   2
                                                                                                                 W
                                                                                                             -
                                                                                                                 ti




             ....       Densiiy
         7
             ---        Salinity                                                                             -
                        Temperature
                                                                                                             -

5000     ~                               ~                       ~                                           ~            ~
    33.0                       33.5                   34.0                   34.5                            35.0
                                             Salinity
                 Station: 47                ANT XI114          1995

                              Density, sigma-t 1 kg/m**3



                          Potential Temperature Ideg C
     -       2   -   1    0         1   2      3       4   5   6      7   8   9   1   0
 0                             ..
         -                                                                            -
         -                                                                            -

                                                                                      -

1000     -
         b




                                            Salinity
Station: 55       ANT XIV4         1995

          Density, sigma-t / kg/m**3




         Potential Temperature /deg C




                  Salinity
       Station: 60       ANT XI114       1995

                 Density, sigma-t 1kg/m**3




33.0          33.5            34.0              34.5   35.0
                         Salinity
Station: 80       ANT XI114       1995

          Density, sigma-t / kg/m**3



         Potential Temperature /deg C




                  Salinity
            Station: 91                ANT XI114           1995

                            Density, sigma-t Ikg/m**3




                           Potential Temperature ldeg C
    -   2   -     1        0   1     2  3   4    5       6       7
0
                                                                -
                                  I-^U.UIJI - IJI I I 1 1 I I I 1 1 1 1
                                        ..   I
                                                       ---           -




                Density
                Salinity
                Temperature
         Station: 103          ANT XI114          1995

                      Density, sigma-t Ikg/m**3



                    Potential Temperature Ideg C




   [_ - - -   Salinity

   l-         Temperature

5 0 0 0 ' l l 1 1 1 1 1 1 1 1 1 1 i l l l l l 1 1
   33.0       33.5      34.0      34.5       35.0
                              Salinity
Station: 104        ANT XI114          1995

          Density, sigma-t 1 kg/m**3



         Potential Temperature Ideg C




                  Salinity
Station: 135            ANT XI114          1995

               Density, sigma-t Ikg/m**3



              Potential Temperature Ideg C




    I
   Density
   Salinity
   Temperature
            Station: 138              ANT XI114          1995

                            Density, sigma-t 1 kglm**3




                         Potential Temperature ldeg C
    -   2    -    1     0 1 2 3 4 5 6 7 8 9 1 0
0                                ~ H {. .4 . l 4 ~ U l l ~ l l l ~ l l l l ~ l l l l ~ l l l l ~ l l l l ~
                                               - - -   - --
                                                                '.N.




        ......


                 i nsity
                   linity
                 Temperature
                                                                       I
                                                                       1I
                          Station: 141                 ANT XI1/4           1995

                                         Density, sigma-t / kg/m**3



                                    Potential Temperature /deg C
      -           2       -     1 0 1 2 3 4 5 6 7 8 9 1 0
  0                             llllllll1^1^U(Jlll~llll~llli~llll~llll~llll~
          7
                                                . ,
                                                           .       -----.
                                                                               ¥-

          -                                                                          -\
                                                                                          \                   -
                                                                                              t>

          -                                                                                                  -
1000      -                                                                                                  -
          -                                                                                                   -
                                                                                                              -

          -                                                                                                   -
                                                                                                                   -Å
2000 -                                                                                                       - $
                                                                                                               n
                                                                                                               r
     -                                                                                                       - C
                                                                                                                   (D
          -                                                                                                   -    \
                                                                                                                   Q
          -                                                                                                   -    8
                                                                                                                   er
3000      -                                                                                                  -tu
          -                                                                                                   -
          -                                                                                                   -
          -                                                                                                   -
4000      -                                                                                                  -
          - ..    ,   ...,    Density                                                                         -
          -   -   -   V
                              Salinity
                              Ternperature
          -                                                                                                   -
5000    I                 I    I    I     ~   I        I       I   I   ~   I     I            I    I   ~ I     I        I   I
    33.0                            33.5                       34.0             34.5                          35.0
                                                      Salinity
Station: 154       ANT XI114          1995

          Density, sigma-t Ikg/m**3




         Potential Temperature Ideg C




                  Salinity
            Station: 162              ANT XI114           1995

                          Density, sigma-t Ikg/m**3



                         Potential Temperature Ideg C




     -XI
     -
                 1
                S linity
                T mperature                                            I
                                                                       I
                                                                       I

5000    I   I    I   I    ~   I   I    1I 1   1   1   1    1     1 1   1   1   1 1
    33.0             33.5                34.0                  34.5             35.0
                                  Salinity
       Station: 166       AMT XI114          1995

                 Density, sigma-t Ikg/m**3




33.0          33.5            34.0              34.5   35.0
                        Salinity
              Station: 172            AMT XI114          1995

                             Density, sigma-t Ikg/m**3



                          Potential Temperature Ideg C
     -   2    -    1     0 1 2 3 4 5 6 7                                    8                    9   1   0
 0
                                                .--. -k,
                                                           È
                                                                \
                                                                    \
                                                                        \
                                                                            s
                                                                                \
                                                                                    \
                                                                                        \

                                                                                            \
                                                                                                \
                                                                                                 l
                                                                                                             ?
                                                                                                             W
                                                                                                             W
                                                                                                             C
                                                                                                             (D




                  Density
             --   Salinity
                  Temperature


5 0 0 0 . 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
   33.0       33.5       34.0       34.5        35.0
                                     Salinity
       Station: 177       ANT XI114           1995

                 Density, sigma-t 1 kg/m**3




                Potential Temperature ldeg C




33.0          33.5            34.0               34.5   35.0
                         Salinity
            Station: 182        AMT XI114          1995

                      Density, sigma-t / kg/m**3




                     Potential Temperature /deg C
    -   2   -   1   0 1 2 3 4 5 6 7                       8   9   1   0
0
               Station: 186              ANT XI114          1995

                                Density, sigma-t Ikg/m**3



                               Potential Temperature Ideg C




3000




4000
       . .. .. ..   Density
                    Salinity
                    Temperature




                                        Salinity
                          Station: 207                        ANT XI114                            1995

                                                 Density, sigma-t I kg/m**3




                                              Potential Temperature /deg C
       -        2             -     1        0 1 2 3 4 5 6 7 8 9 1 0
  0
                                                               l l l ~ l ~ l l ~ l l l l ~ l l l l ~ l l ~ ~ ~ ~ ~ ~ ~
           -                                                            b        '
                                                                                          -
                                                                 /
                                                                            '.
           -
                                                                            Ã


                                                                                 I
                                                                                 -
                                                                                 .                                                                  -
                                                                                       "È
           -                                                                                 ^-1
                                                                                                   \
1000       -                                                                                           \
                                                                                                           \
                                                                                                                                                -
                                                                                                               \
                                                                                                                   \
                                                                                                                       \
                                                                                                                           \                        -
                                                                                                                               \
                                                                                                                                1
           -                                                                                                                                        -
                                                                                                                                \                       7
2000 -                                                                                                                              \           -       8
                                                                                                                                                        m
                                                                                                                                     I              -   2
           -                                                                                                                          I             -   \
                                                                                                                                                        n.
                                                                                                                                      I
                                                                                                                                      l
                                                                                                                                                  g.
                                                                                                                                                  0-
                                                                                                                                                    -
3000       -                                                                                                                          1         - W
           -                                                                                                                            I           -
           -                                                                                                                        I
           7
                                                                                                                                    l               -
                                                                                                                                    I
4000       -                                                                                                                        1           -
               . ... .   ..                                                                                                         I
           --       -             Sa inity                                                                                          I               -
           -                      Te-nperature                                                                                      1
                                                                                                                                                    -
                                                                                                                                    l
5000     I                    I      I       I      ~     I      I      I            I ; ]
                                                                                       ~            1I     1           1            t       1   1
    33.0                                 33.5                    34.0                                      34.5                                     35.0
                                                         Salinity
5 Sections


Presented sections show the distribution of the properties in the region of
Antarctic Intermediate Water (stations 1-14 and 14-47) and across the Antarctic
Circumpolar Current. Numbers of the stations are indicated On the top of the
plots.
LOT,
Similarity of non dimensional density profiles.


Qualitative inspection of potential density distribution (CS@) reveals notable

similarity in the vertical profiles that can be recognised if one follows three
adjacent density isolines in an increasing order (for example 27.5, 27.6 and 27.7
kg-m-3 numbered as isolines 1, 2 and 3 respectively; See Page 55). It can be

Seen that the vertical distance of the isoline 2 relative to the isolines 1 and 3
remains constant over a long spatial distance whereas the absolute vertical layer
thickness confined between these isolines changes considerably. Otherway
stated, it means that any density difference in the considered layer, normalised
by the maximum density difference of the layer, is a function of the non
dimensional vertical CO-ordinate:




Here the superscript stands for an isoline number, pà =--P - P          is a non
                                                        P -P
dimensional vertical CO-ordinateand p    -   a pressure level of the corresponding
isopycnal. Figure 2 shows the vertical profiles of non dimensional density,
calculated for the layer confined between the isopycnals 27.5 and 27.7 k g m 3 . It

can be Seen that similarity is characteristic to an area about 1500 km wide which
locates in the region of water mass transformation from Sub Antarctic- to
Antarctic waters.


Physical reasons, responsible for the observed similarity are not evident.
Figure 2 . Non dimensional density profiles 0 = ( 0 ; - oa) ( ; 0 : ) (where
                                                           / 0-

o ,= 27.5kgrn" 1 .G;= 21.7 p \
 '                 '
                         k            aa < oa 5 0 ; ) as a function of non dimensional layer
thickness   p,= ( p - P)1 ( P ' -   calculated for the deep stations: 14, 21, 28, 37, 47, 55, 6 0 ,
Following simple arguments show that similarity can be regarded as a limiting
case of stationary mixing along neutral surfaces in the continuously stratified
ocean with a constant horizontal pressure gradient which is balanced by the
Coriolis force (i.e. one has constantly sloping isopycnals as it is the case in the
region of the Antarctic Circumpolar Current). In this limiting case, temperature
and salinity gradients along isopycnic surfaces are Zero. It appears then also that
all vertical temperature and salinity profiles coincide in a potential temperature -
salinity diagram and hence the surfaces of potential densities referenced to
different reference pressures and neutral surfaces coincide with each other in
the     X,   y, z space. Figure 3 gives such example and demonstrates that in the
region of the Antarctic Circumpolar Current potential density surfaces,
referenced to Zero and 2000 dbar level, are to a good approximation parallel.
The other way to state the Same argument is to use the definition of the neutral
surfaces (McDougall1987)




                           j is a neutral surface gradient operator,   X   and y are

horizontal CO-ordinates and i and       j   are unit vectors in these directions and


                    is a coefficient of adiabatic and isentropic compressibility
 = (:$)e,s

(subscripts mean that potential temperature and salinity being kept constant). (1)
multiplied by a characteristic distance L, can be rewritten in the form of finite
differences:
        36.8
                    27.6              27.7           27.8                     27.9
                                  sigma-theta 1 kg/m**3


Figure 3. G, - G o diagram. Shows that the isolines of potential density surfaces referenced to

different pressure levels are in X, y, z space to a good approximation parallel. Calculated for the

stations: 14, 17, 19, 21, 23, 26, 28, 30, 32, 37, 45, 47, 55, 60, 138, 141, 154, 162, 166, 172, 177,

182, 186, 207.
                       0-r = P - P Y ( P - P ~ ) *                        (2)
where 0 - = a(Q,S,pr) is a particles' density referenced to a pressure level p and
p = p(9,S, P )   - in situ density. (2) expresses the fact that the local tangent plane of
an isopycnic surface coincides with the tangent plane of a neutral surface
(McDougall, 1984). Fixing any of the reference pressure levels while moving in
the direction of increasing or decreasing pressure means that (2) can be used
for the calculation of a potential density surface that in general case do not
coincide with a neutral surface. Noting now that potential density, referenced to
Zero pressure can be expressed as                    OP   p-p,yp   (where p, is a constant), (2)

can be rewritten in the form:




For a water particle that moves adiabatically and isentropically in the ocean, (3)
is constant for a fixed pressure reference level or changes proportionally to the
latter if the reference pressure is changing. For a couple of water particles:




Now making use of non linearity in the equation of state a2p/Qpa@ and
a 2 p / 3 p 9 S , the finite difference for adiabatic and isentropic compressibility for any

pair of water particles can be expressed as following:
where a = - 11 p(3p/a0)s,p and à = 11p(ap/as)^          are the thermal expansion

coefficient and saline contraction coefficient.


If the isopycnals of the potential density surfaces are parallel in x,y,z space then
(4) remains constant for any fixed pressure reference level. Figure 4 which
shows the dependence of pc(-AoAO+AßAS'on a layer thickness Ap, confirms

that in the case of the considered hydrographic section the right side of (4)
combined with (5) is to a good approximation constant for any fixed pair of
potential density surfaces. The shape of the curve is determined by vertical
temperature   -   salinity stratification (for the respective 0 - 5 diagram See Figure
5) and by the upper isopycnal chosen.


Finally, similarity of vertical non dimensional density profiles considered at the
beginning of the paragraph, follows also from (4) and (5) if written in the
normalised form:
             0             1000           2000       3000               4000          5000
                                             Ap / dbar


Figure 4. c = p,.(-(a at)(@
                    -                - 0 ' )+ (Ã - P')(.?-   S I ) )as a function of the layer thickness

&P = ( p - P ' ) , where    ,@',SI     are the values of pressure, potential ternperature and salinity on

the isopycnal G = 36.8 k g ~ n - 3
               :                 and       p,@,S are the respective values for G?> 0 ; . Calculated
for the stations: 14, 17, 19, 21, 23, 26, 28, 30, 32, 37, 45, 47, 55, 60, 138, 141, 154, 162, 166,
172, 177, 182, 186, 207.
                                          Salinity


Figure 5. 0-   5' diagram calculated for 0,> 4 = 36.8 k g m 3 .Calculated for the stations: 14,
17, 19, 21, 23, 26, 28; 30, 32, 37, 45, 47, 55, 60, 138, 141, 154, 162, 166, 172, 177, 182, 186,
207.
7 References


McDougall, T.J., 1984: The Relative Roles of Diapycnal and Isopycnal Mixing on
                                   .
Subsurface Water Mass Conversion, J Phys. Oceanogr., 14, 1577-1589.


                                        J.
McDougall, T.J., 1987: Neutral ~urfac'es, Phys. Oceanogr., 17, 1950-1964.

				
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