Visual observations of the Red Sea hot brines

Abstract

The research vessel Akademik Kurchatov has investigated the Red Sea rift zone with the aid of a manned submersible Pisces XI in the winter of 1979–80, as the value of such investigations is now well established^1,2. Our research involved a comprehensive programme of hydrophysical studies in deeps containing thermal brines of the sea axial rift—Atlantis II, Discovery and Valdivia (see Fig. 1). Measurements were made with standard hydrographic stations, the AIST temperature and salinity meter with specially selected temperature and electric conductivity scales on board a towed vehicle Zvouk-4m, and Pisces XI. The present data on water stratification in the Atlantis II, Chain and Valdivia deeps have in general confirmed previously known data^3–9 but have also revealed some new facts. For example, we have recorded an increase of temperature of the hot brine of up to 62 °C in the southwestern basin of the Atlantis II deep since studies aboard the R/V Sonne in 1977. Using data from this expedition, Hartmann⁹ gives a curve of temperature growth in the lower brine constructed from the data of different expeditions since 1965. A multilayer temperature structure of the upper brine and horizontal inhomogeneities have also been found^8–10. Steps in the upper brine of the Atlantis II deep were first described^6,9 from the surveys of the R/V Valdivia (1971–72) and Sonne (1977). Our observations reveal stratification of the deep brine (Table 1) in temperature and electrical conductivity (salinity) and enable their rate of change of thickness to be estimated¹⁰.