In October 2008, we measured temperature and salinity in hot, hypersaline brine filling the Atlantis II and Discovery Deeps on the Red Sea spreading center west of Jeddah, Saudi Arabia. In agreement with previous observations in the Atlantis II Deep, we found a stack of four convective layers with vertically uniform temperature profiles separated by thin interfaces with high vertical temperature gradients. Temperature in the thick lower convective layer in the Atlantis II Deep continued to slowly increase at 0.1 °C/year since the last observations in 1997. Previously published data show that the temperature of all four convective layers increased since the 1960s at the same rate, from which we infer that diffusive vertical heat flux between convective layers is rapid on time scales of 3-5 years and, thus, heat is lost from the brine pools to overlying Red Sea Deep Water. Heat budgets suggest that the heat flux from hydrothermal venting has decreased from 0.54. GW to 0.18. GW since 1966. A tow-yo survey found that temperature in the upper convective layers changes about 0.2 °C over 5-6. km but the temperature in the lower brine layer remains constant. Temperature in the lower convective layer in the Discovery Deep remains unchanged at 48 °C. To explain these results, we hypothesize that heat flux from a hydrothermal vent in the floor of the Discovery Deep has been stable for 40 years, whereas temperature of the brine in the Atlantis II Deep is adjusting to the change in hydrothermal heat flux from the vent in the Southwest Basin. We found no changes in the upper transition layer at 1900-1990. m depth that appeared between 1976 and 1992 and suggest that this layer originated from the seafloor elsewhere in the rift. © 2012 Elsevier Ltd.
|Number of pages
|Deep Sea Research Part I: Oceanographic Research Papers
|Published - Jun 2012
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): USA 00002, KSA 00011, KSA 00011/02
Acknowledgements: We gratefully acknowledge the financial and logistical support for the R/V Oceanus cruise provided by King Abdullah University of Science and Technology (KAUST), as well as the support of an international group of scientists and technicians during the cruise. This research is based on work supported by Award Nos. USA 00002, KSA 00011 and KSA 00011/02 made by KAUST. Guidance and support in Saudi Arabia was provided by Y. Kattan, A. Al-Suwailem, H. Al-Jandali, and J. Luyten. In the US, ship operations were facilitated by L. Madin, R. Detrick, A. Suchy, L. Capporelli, K. Heywood and B. Costello. We thank the officers and crew of the R/V Oceanus for their assistance at-sea. Instrument operations and data acquisition were ably managed by F. Bahr, M. Swartz, and G. Tupper (WHOI). G. Tupper also did the oxygen and salinity analyses and managed operation of the Hobo sensors. We are very grateful to M. Swartz, who calibrated the Hobos, and to T. McKee, who processed the CTD data and applied corrections for bottle analyses to salinity and oxygen results. Lars-Goran Danielsson kindly provided hydrographic data for the 1976 survey of the R/V Akademik Kurchatouv that appeared in figures of Bubnov et al. (1977). We thank an anonymous reviewer for corrections and helpful suggestions on the manuscript.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.