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Grasshoff, Klaus (1969): Chemical observations in the Red Sea and the inner Gulf of Aden during the International Indian Ocean Expedition 1964/65 [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.603890, Supplement to: Grasshoff, K (1969): Zur Chemie des Roten Meeres und des Inneren Golfs von Aden nach Beobachtungen von F.S. "Meteor" während der Indischen Ozean Expedition 1964/65. Meteor Forschungsergebnisse, Deutsche Forschungsgemeinschaft, Reihe A Allgemeines, Physik und Chemie des Meeres, Gebrüder Bornträger, Berlin, Stuttgart, A6, 1-76

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Abstract:
The Red Sea has a special place among the adjacent seas of the world. High evaporation, exclusion of its deep water from contact with the Indian Ocean proper and complete absence of continental drainage may result special conditions of the chemistry of the Red Sea.
This paper aims to describe and explain the peculiarity of the hydrochemical situation. The influence of the topography, of the inflow and outflow through the straights of Bab el Mandeb, of the evaporation, of the stability of the water layers, and of the circulation will be studied. An attempt is made to estimate the apparent oxygen ultilisation in order to obtain an indication of the biological activity. A further attempt is made toward the quantitative estimation of the circulation of the nutrients and also to obtain some information about transport, dissolution, and precipitation of calcium carbonate.
The basis of these investigations are mainly observations of R. V. "Meteor" during the International Indian Ocean Expedition 1964/65.
The determination of dissolved oxygen, dissolved inorganic phosphate, nitrate, nitrite, ammonia, pH, alkalinity, silicate as well as salinity and temperature forms the necessary basis for such an investigation of the chemical conditions. In the first chapter the methods and some modifications for the determination of the chemical properties as applied during the I.I.O.E. cruise of R. V. "Meteor" are described. The new methods, as worked out and tested under sea going conditions during several years by the author, are described in more detail. These are the methods for nitrate, silicate, the automatic determination of dissolved inorganic phosphate and silicate, the automated determination of total phosphorus, the in situ recording of the oxygen tension, and the modification for the determination of ammonia, calcium, and dissolved oxygen. With these revised methods more than 18,000 determinations have been carried out during the Indian Ocean cruise.
The complete working up of the chemical data of the Indian Ocean Expedition of R. V. "Meteor" is devided into four sections: Contributions 1) to the Chemistry of the Red Sea and the Inner Gulf of Aden, 2) to the Gulf of Aden and the Somali Coast Region, 3) to the Western Indian Coast Region, and 4) to the Persian Gulf and the Straits of Oman. This paper presents the first contribution.
The special hydrographical conditions are discussed. It can be shown, that the increase of salinity in the surface waters from the south to the north of the Red Sea is only to about 30 % due to evaporation. The remaining increase is presumed to be due to the admixture of deep water to the surface layers. A special rate for the consumption of oxygen (0.114 ml/ l/a) is derived for the deep water of the Red Sea at 1500 m. Based upon the distribution of the dissolved oxygen along the axii of the Red Sea, a chematic model for the longitudinal circulation of the Red Sea is constructed. This model should be considered as a first approximation and may explain the special distribution of phosphate, nitrate, and silicate.
Based upon the evaluation of the residence time of the deep water a dissolution rate for silicate is estimated as 1 mygat/a. It seems possible to calculate residence times of water masses outside the Red Sea from the silicate content. The increase of silicate and the consumption of oxygen lead to residence times of the water below the thermocine of 30 to 48 years.
The distribution of oxygen in the Straits of Bab el Mandeb is described and discussed. The rate of consumption of the oxygen in the outflowing Red Sea water is estimated to 8.5 ml/ l/a. This rather high rate is explained with reference to the special conditions in the outflowing water.
The Red Sea water is characterized initially by a relative high content of oxygen and a low content of nutrients. The increase in nutrients and the decrease in the oxygen content is a secondary process of the Red Sea water on its way to the Arabian Sea.
Based upon the vertical distribution of the dissolved inorganic phosphate vertical exchange coefficients of 1 - 4 g/cm/sec and vertical current speeds of 10**-5 to 10**-4 cm/sec are calculated for some stations in the Red Sea.
The distribution of phosphate, silicate, nitrate, nitrite and ammonia for the Red Sea and the Straits of Bab el Mandeb are discussed. The special circulation is evaluated and the balance of the nutrients is estimated by means of the brutto transport. The nutrient deficit is assumed to be balanced by sporadic inflow of intermediate water from the Gulf of Aden. An example for such an inflow has been observed and is demonstrated. The silicate-salinity relationships are a suitable way for characterizing water masses in the Red Sea.
Equations for the calculation of the different components from the carbonate system, the ion activities, and the calcium carbonate saturation are evaluated. The influence of temperature and pressure is taken into account. The carbonate saturation is calculated from the determined concentrations of calcium, alkalinity, and the hydrogen ion activity. Saturation values of 320 % are found for the surface layer and of 100% ± 1 for the deep water. The extraordinary equilibrium conditions may explain the constant Ca/Cl ratio and also the sedimentation of undissolved carbonate skelecons even in greater depths. A main sedimentation rate of 2 * 10**-3cm/year is evaluated from a total sedimentation of 10 * 106 to/a of calcium carbonate in the Red Sea. The appendix contains those data, which are not published in the data volume of the I.I.O.E. expedition of R. V. "Meteor".
Coverage:
Median Latitude: 15.068778 * Median Longitude: 42.873364 * South-bound Latitude: 11.116000 * West-bound Longitude: 36.166000 * North-bound Latitude: 25.366000 * East-bound Longitude: 53.466000
Date/Time Start: 1964-11-20T00:00:00 * Date/Time End: 1964-12-21T00:00:00
Event(s):
M1_CTD023 (M1_023) * Latitude: 25.366000 * Longitude: 36.166000 * Date/Time: 1964-11-20T00:00:00 * Elevation: -2248.0 m * Location: Red Sea * Campaign: M1 (IIOE - International Indian Ocean Expedition) * Basis: Meteor (1964) * Method/Device: CTD/Rosette (CTD-RO)
M1_CTD026 (M1_026) * Latitude: 22.133000 * Longitude: 37.950000 * Date/Time: 1964-11-22T00:00:00 * Elevation: -2170.0 m * Location: Red Sea * Campaign: M1 (IIOE - International Indian Ocean Expedition) * Basis: Meteor (1964) * Method/Device: CTD/Rosette (CTD-RO)
M1_CTD028 (M1_028) * Latitude: 21.283000 * Longitude: 38.050000 * Date/Time: 1964-11-22T00:00:00 * Elevation: -2130.0 m * Location: Red Sea * Campaign: M1 (IIOE - International Indian Ocean Expedition) * Basis: Meteor (1964) * Method/Device: CTD/Rosette (CTD-RO)
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
33 datasets

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Datasets listed in this publication series

  1. Grasshoff, K (1969): Ammonia profile of the water column of site M1_CTD023, Red Sea (Table 14). https://doi.org/10.1594/PANGAEA.552474
  2. Grasshoff, K (1969): Oxygen saturation in the Red Sea, site M1_CTD023 (Table 19, 20). https://doi.org/10.1594/PANGAEA.552484
  3. Grasshoff, K (1969): Ammonia profile of the water column of site M1_CTD026, Red Sea (Table 14). https://doi.org/10.1594/PANGAEA.552475
  4. Grasshoff, K (1969): Oxygen saturation in the Red Sea, site M1_CTD026 (Table 19, 20). https://doi.org/10.1594/PANGAEA.552485
  5. Grasshoff, K (1969): Oxygen saturation in the Red Sea, site M1_CTD028 (Table 19, 20). https://doi.org/10.1594/PANGAEA.552486
  6. Grasshoff, K (1969): Ammonia profile of the water column of site M1_CTD029, Red Sea (Table 14). https://doi.org/10.1594/PANGAEA.552476
  7. Grasshoff, K (1969): Ammonia profile of the water column of site M1_CTD039, Red Sea (Table 14). https://doi.org/10.1594/PANGAEA.552477
  8. Grasshoff, K (1969): Calcium carbonate and oxygen saturation in the Red Sea, site M1_CTD039 (Table 19, 20). https://doi.org/10.1594/PANGAEA.552487
  9. Grasshoff, K (1969): Hydrographical and chemical profile of the water column of site M1_CTD039 (Table 16). https://doi.org/10.1594/PANGAEA.552506
  10. Grasshoff, K (1969): Calcium carbonate and oxygen saturation in the Red Sea, site M1_CTD042 (Table 19, 20). https://doi.org/10.1594/PANGAEA.552488
  11. Grasshoff, K (1969): Calcium carbonate and oxygen saturation in the Red Sea, site M1_CTD043 (Table 19, 20). https://doi.org/10.1594/PANGAEA.552489
  12. Grasshoff, K (1969): Calcium carbonate and oxygen saturation in the Red Sea, site M1_CTD045 (Table 19, 20). https://doi.org/10.1594/PANGAEA.552490
  13. Grasshoff, K (1969): Calcium carbonate and oxygen saturation in the Red Sea, site M1_CTD049 (Table 19, 20). https://doi.org/10.1594/PANGAEA.552491
  14. Grasshoff, K (1969): Oxygen profile of the water column of site M1_CTD049, Red Sea (Table 4). https://doi.org/10.1594/PANGAEA.552471
  15. Grasshoff, K (1969): Calcium carbonate and oxygen saturation in the Red Sea, site M1_CTD053 (Table 19, 20). https://doi.org/10.1594/PANGAEA.552492
  16. Grasshoff, K (1969): Calcium carbonate and oxygen saturation in the Red Sea, site M1_CTD055 (Table 19, 20). https://doi.org/10.1594/PANGAEA.552493
  17. Grasshoff, K (1969): Calcium carbonate and oxygen saturation in the Red Sea, site M1_CTD056 (Table 19, 20). https://doi.org/10.1594/PANGAEA.552494
  18. Grasshoff, K (1969): Ammonia profile of the water column of site M1_CTD062, Red Sea (Table 14). https://doi.org/10.1594/PANGAEA.552478
  19. Grasshoff, K (1969): Calcium carbonate and oxygen saturation in the Red Sea, site M1_CTD062 (Table 19, 20). https://doi.org/10.1594/PANGAEA.552495
  20. Grasshoff, K (1969): Ammonia profile of the water column of site M1_CTD066, Red Sea (Table 14). https://doi.org/10.1594/PANGAEA.552479
  21. Grasshoff, K (1969): Calcium carbonate and oxygen saturation in the Red Sea, site M1_CTD066 (Table 19, 20). https://doi.org/10.1594/PANGAEA.552496
  22. Grasshoff, K (1969): Ammonia profile of the water column of site M1_CTD069, Red Sea (Table 14). https://doi.org/10.1594/PANGAEA.552480
  23. Grasshoff, K (1969): Calcium carbonate and oxygen saturation in the Red Sea, site M1_CTD069 (Table 19, 20). https://doi.org/10.1594/PANGAEA.552497
  24. Grasshoff, K (1969): Hydrographical and chemical profile of the water column of site M1_CTD069 (Table 16). https://doi.org/10.1594/PANGAEA.552507
  25. Grasshoff, K (1969): Ammonia profile of the water column of site M1_CTD071, Red Sea (Table 14). https://doi.org/10.1594/PANGAEA.552481
  26. Grasshoff, K (1969): Calcium carbonate and oxygen saturation in the Red Sea, site M1_CTD071 (Table 19, 20). https://doi.org/10.1594/PANGAEA.552498
  27. Grasshoff, K (1969): Hydrographical and chemical profile of the water column of site M1_CTD071 (Table 16). https://doi.org/10.1594/PANGAEA.552508
  28. Grasshoff, K (1969): Ammonia profile of the water column of site M1_CTD072, Red Sea (Table 14). https://doi.org/10.1594/PANGAEA.552482
  29. Grasshoff, K (1969): Calcium carbonate and oxygen saturation in the Red Sea, site M1_CTD072 (Table 19, 20). https://doi.org/10.1594/PANGAEA.552499
  30. Grasshoff, K (1969): Oxygen profile of the water column of site M1_CTD092, Red Sea (Table 4). https://doi.org/10.1594/PANGAEA.552472
  31. Grasshoff, K (1969): Phosphate and silicate profile of the water column of site M1_CTD096 (Table 6). https://doi.org/10.1594/PANGAEA.552500
  32. Grasshoff, K (1969): Phosphate and silicate profile of the water column of site M1_CTD101 (Table 6). https://doi.org/10.1594/PANGAEA.552501
  33. Grasshoff, K (1969): Oxygen profile of the water column of site M1_CTD105, Red Sea (Table 4). https://doi.org/10.1594/PANGAEA.552473