Indian Ocean: Vertical sections and data sets for selected lines

, page under construction

Send email to ltalley@ucsd.edu.

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Hydrographic data (CTD and discrete bottle data: oxygen, salinity and nutrients) from selected long sections and publically available WOCE Hydrographic Program data (none available for the Indian Ocean) were gridded using a modified version of Roemmich's (1983) application of objective mapping to hydrographic station data. The current set of plots represents just those which were compiled individually over about one year, and so they are not computed uniformly. Gridded data files are not included for now because of the non-uniformity (unlike for the Pacific sections).

Downloading the postscript files: if your web browser attempts to plot the postscript files and you want to save them instead, instructions for netscape are: click with the 3rd right mouse button instead of the leftmost one and answer the dialog question.

Bottle data for each of the sections is made available through this site, in NODC's format and in a straight ascii table which does not include all of the header information in the NODC files but which is easier to manipulate. The few public WHP data sets are available through the WHP Special Analysis Centre in Hamburg and at the WHP SAC mirror site at Scripps Institution of Oceanography. The non-WHP CTD data sets are available in the program "ctdsearch" on the nemo data server at SIO through a public login with a menu.

Map of sections

Method

Plots of vertical sections

Zonal sections

LineLocationShipDatesChief Scientist
ind_32s32 S DarwinNov-Dec, 1987Warren/Toole

Plots are available online in gif format; postscript versions can also be downloaded.

Meridional sections

LineLocationShipDatesChief Scientist
Geosecs West60 E MelvilleDec-Feb, 1977-78Williams/Craig/Weiss
Geosecs Central80 E MelvilleApril, 1978Broecker
Geosecs East100 E MelvilleApril, 1978Spencer
I8I990 E KnorrDec. 1994 - Feb. 1995 McCartney, Gordon


WOCE Hydrographic Programme Office
WOCE Data Information Unit hydrographic data page
WHP Special Analysis Centre
nemo WHP SAC mirror site at SIO
U.S. WOCE Homepage
nemo oceanographic data server at SIO
Scripps Institution of Oceanography local servicees


ind_32s

Charles Darwin cruise, 1987, Toole and Warren.

Pre-WOCE section along WHP section I5.

Toole, J. M. and B. A. Warren, 1993. A hydrographic section aross the subtropical South Indian Ocean. Deep-Sea Res., 40, 1973-2019.

NODC SD2 bottle data: i5_32s.sd2

Flat text bottle data (no header information other than station number, location and date): i5_32s.dat

Property gif plot postscript file
Potential temperature Y Y
Salinity Y Y
Potential density (0) Y Y
Potential density (1000) Y Y
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Geosecs Indian Ocean - Western Section

R/V Melville, 1977-1978

Geosecs Western Indian Ocean section at about 60E

Spencer, D., W. S. Broecker, H. Craig, R. F. Weiss, 1982. Geosecs Indian Ocean Expedition, Volume 6, Sections and Profiles. IDOE, National Science Foundation, 140 pp.

NODC format SD2 bottle data for complete Indian Ocean expedition (edited): geosecs_indian.sd2

Flat text bottle data (no header information other than station number, location and date): geosecs_indian.dat

Property gif plot postscript file
Potential temperature Y Y
Salinity Y Y
Potential density (0) Y Y
Oxygen (umol/kg) Y Y
Silicate (umol/kg) Y Y
Nitrate (umol/kg) Y Y
Phosphate (umol/kg) Y Y
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Geosecs Indian Ocean - Central Section

R/V Melville, 1978

Geosecs Central Indian Ocean section at about 80E

Spencer, D., W. S. Broecker, H. Craig, R. F. Weiss, 1982. Geosecs Indian Ocean Expedition, Volume 6, Sections and Profiles. IDOE, National Science Foundation, 140 pp.

NODC format SD2 bottle data for complete Indian Ocean expedition (edited): geosecs_indian.sd2

Flat text bottle data (no header information other than station number, location and date): geosecs_indian.dat

Property gif plot postscript file
Potential temperature Y Y
Salinity Y Y
Potential density (0) Y Y
Oxygen (umol/kg) Y Y
Silicate (umol/kg) Y Y
Nitrate (umol/kg) Y Y
Phosphate (umol/kg) Y Y
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Geosecs Indian Ocean - Eastern Section

R/V Melville, 1978

Geosecs Eastern Indian Ocean section centered at about 110E

Spencer, D., W. S. Broecker, H. Craig, R. F. Weiss, 1982. Geosecs Indian Ocean Expedition, Volume 6, Sections and Profiles. IDOE, National Science Foundation, 140 pp.

NODC format SD2 bottle data for complete Indian Ocean expedition (edited): geosecs_indian.sd2

Flat text bottle data (no header information other than station number, location and date): geosecs_indian.dat

Property gif plot postscript file
Potential temperature Y Y
Salinity Y Y
Potential density (0) Y Y
Oxygen (umol/kg) Y Y
Silicate (umol/kg) Y Y
Nitrate (umol/kg) Y Y
Phosphate (umol/kg) Y Y
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I9N and I8S (90E)

i9all station track plot (gif image)
i9all station track plot (postscript)

Property gif plot postscript file
Potential temperature Y Y
Salinity Y Y
Potential density (0) Y Y
Potential density (2000) Y Y
Potential density (4000) Y Y
Neutral density (McDougall) Y Y
Bottle salinity(ml/l) Y Y
Oxygen (ml/l) Y Y
Silicate Y Y
Nitrate Y Y
Nitrite Y Y
Phosphate Y Y
i9all station information files (latitude/longitude and distance along the section for each station).

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Methods

Gridding

The original station data were either CTD profiles, mostly at 2 dbar intervals, or discrete bottle data, with up to 36 bottles per station. The data were objectively mapped using Roemmich's (1983) method adapted for producing sections which subjectively were most like those which are hand contoured, and hence smoothed somewhat by eye.

It is assumed that the chief scientist chose appropriate horizontal sampling, with tighter spacing across regions of strong gradients.

CTD and discrete data are mapped differently to account for the sampling differences. The same decay scale and horizontal/vertical scale ratio are used for both.

CTD data: The 2 dbar profiles are first smoothed vertically with a Gaussian with half-width 10 dbar. Data are used from 6 stations at a time, and 6 depths. The mean which is removed is just that of this small rectangle.

Discrete bottle data: Data from 6 stations are used at one time. An Akima cubic spline is fit to the deepest station of the group, and this profile is removed from all stations in the group as a representation of the mean for the group. The residuals are then mapped and the mean added back in.

The programs for gridding the data are available from Lynne Talley (ltalley@ucsd.edu).

Potential density calculations

The potential densities calculated relative to 0, 2000 and 4000 dbar use potential temperature referenced to these pressures and then density referenced to these pressures, respectively. The McDougall neutral density parameter is also used.

References

Jackett, D. R. and T. J. McDougall, 1996. A neutral density variabile for the world's oceans. J. Phys. Oceanogr., submitted.
Roemmich, D., 1983. Optimal estimation of hydrographic station data and derived fields. J. Phys. Oceanogr., 13, 1544-1545.
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Lynne D. Talley, ltalley@ucsd.edu
Scripps Institution of Oceanography
University of California, San Diego
Last updated 21 October, 1996