Seasonal variations of hydrographic parameters off the Sudanese coast of the Red Sea, 2009–2015

Elsheikh B. Ali, James H. Churchill, Knut Barthel, Ingunn Skjelvan, Abdirahman M. Omar, Tor E. de Lange, Elfatih B.A. Eltaib

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

The variations of temperature and salinity in the Sudanese coastal zone of the Red Sea are studied for the first time using measurements acquired from survey cruises during 2009–2013 and from a mooring during 2014–2015. The measurements show that temperature and salinity variability above the permanent pycnocline is dominated by seasonal signals, similar in character to seasonal temperature and salinity oscillations observed further north on the eastern side of the Red Sea. Using estimates of heat flux, circulation and horizontal temperature/salinity gradients derived from a number of sources, we determined that the observed seasonal signals of temperature and salinity are not the product of local heat and mass flux alone, but are also due to alongshore advection of waters with spatially varying temperature and salinity. As the temperature and salinity gradients, characterized by warmer and less saline water to the south, exhibit little seasonal variation, the seasonal salinity and temperature variations are closely linked to an observed seasonal oscillation in the along-shore flow, which also has a mean northward component. We find that the inclusion of the advection terms in the heat and mass balance has two principal effects on the computed temperature and salinity series. One is that the steady influx of warmer and less saline water from the south counteracts the long-term trend of declining temperatures and rising salinities computed with only the local surface flux terms, and produces a long-term steady state in temperature and salinity. The second effect is produced by the seasonal alongshore velocity oscillation and most profoundly affects the computed salinity, which shows no seasonal signal without the inclusion of the advective term. In both the observations and computed results, the seasonal salinity signal lags that of temperature by roughly 3 months.
Original languageEnglish (US)
Pages (from-to)1-10
Number of pages10
JournalRegional Studies in Marine Science
Volume18
DOIs
StatePublished - Jan 10 2018
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2022-06-21
Acknowledged KAUST grant number(s): KSA00011, USA00001, USA00002
Acknowledgements: The SPS surveys were funded by the Norwegian Norad’s Program for Master Studies and organized by IMR–RSU in Port Sudan. We thank the captain and crew of the Sudanese Marine Security Department ships, which were used for sampling. The PSH surveys were organized and funded by IMR–RSU though the local Environmental Monitoring Program. The mooring and attached instrumentation were funded by the Michelsen Centre for Research-based Innovation in Measurements Science and Technology (MIMT) in Bergen. We are grateful to the captain and crew of the Sudanese Sea Port Corporation tugboat used for deployment. We are thankful to Prof. Abdel Gadir D. El Hag and Prof. Mohamad E.A. Hamza (former directors of IMR) for their support, and also to the IMR staff for making the data collection possible.

NCEP Reanalysis-2 data and NOAA High Resolution SST data were obtained from the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA (http://www.esrl.noaa.gov/psd/). The central Red Sea mooring data were acquired as part of a WHOI–KAUST collaboration funded by Award Nos. USA00001, USA00002, and KSA00011 to the WHOI by the KAUST in the Kingdom of Saudi Arabia. The work of I. Skjelvan and A.M. Omar was partly supported by the Research Council of Norway through the MIMT Center for Research-based Innovation. This work is part of a Ph.D. project at GFI–UiB funded by the Norwegian Quota program .
This publication acknowledges KAUST support, but has no KAUST affiliated authors.

ASJC Scopus subject areas

  • Animal Science and Zoology
  • Ecology, Evolution, Behavior and Systematics
  • Aquatic Science
  • Ecology

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