The thickness of this layer, often called the mixed layer depth (MLD), is one of the most important oceanographic parameters : A Part from the Book Chapter : Seasonal Variability of Mixed Layer Depth in the Red Sea

Turbulence in the upper layer of the ocean associated with various physical processes leads to the formation of a quasi-homogeneous layer with nearly uniform properties. The thickness of this layer, often called the mixed layer depth (MLD), is one of the most important oceanographic parameters, as this layer directly communicates and exchanges energy with the atmosphere and therefore has a strong impact on the distribution of heat, ocean biology and near-surface acoustic propagation. Heat and fresh-water exchanges at the air-sea interface and wind stress are the primary forces behind turbulent mixing. Similarly, stirring associated with cyclonic and anticyclonic eddies enhances the mixing process along the isopycnal surfaces where stirring may occur with minimum energy.

Author(s) Details:

P. Abdulla
Applied Research Center for Environment and Marine Studies, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia

A. Alsaafani
Department of Marine Physics, King Abdulaziz University, Jeddah 80200, Saudi Arabia

M. Alraddadi
Department of Marine Physics, King Abdulaziz University, Jeddah 80200, Saudi Arabia

T. M. Asharaf
Applied Research Center for Environment and Marine Studies, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia.

M. Albarakati
Department of Marine Physics, King Abdulaziz University, Jeddah 80200, Saudi Arabia

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Recent Global research Development in Ocean turbulence, mixed layer depth, air-sea interaction, wind stress, eddies, heat exchange

1. Seasonal Variability of Red Sea Mixed Layer Depth: The Influence of Atmospheric Buoyancy and Momentum Forcing:

• In this study, researchers analyzed the seasonal and spatial evolution of the mixed layer (ML) in the Red Sea using a high-resolution ocean circulation model.
• The simulation revealed strong spatiotemporal variability reflecting complex patterns associated with air-sea buoyancy flux and wind forcing, as well as the significant impact of the basin’s general and mesoscale circulation.
• During spring and summer, buoyancy forcing intensifies stratification, resulting in a generally shallow ML throughout the basin.
• Local maxima in MLD are associated with the influence of mesoscale circulation and regular wind-induced mixing.
• Under the influence of surface buoyancy loss, the process of deepening the ML begins in early September, reaching its maximum depth in January and February.
• The northern Gulf of Aqaba and western parts of the northern Red Sea exhibit the deepest ML, with gradual shoaling toward the south due to the surface advection of relatively fresh water from the Gulf of Aden.
• MLD variability is primarily driven by atmospheric buoyancy forcing, especially its heat flux component. Wind-induced mixing has a significant impact locally, especially during summer.
• Strong winds channeled by topography (e.g., near the Strait of Bab-Al-Mandeb) and lateral jets venting through mountain gaps (e.g., the Tokar Jet in the central Red Sea) contribute to the complex MLD distribution [1].

2. Seasonal Variability of Mixed Layer Depth from Argo Floats in the Central Red Sea:

• Researchers used temperature and salinity data from two Argo floats available in the central Red Sea for a period of 2 years to examine MLD variability in the region [2].

3. Mixed Layer Depth Variability in the Red Sea:

• For the first time, a monthly climatology of MLD in the Red Sea was derived based on temperature profiles.
• The general pattern of MLD variability is evident: deep MLDs during winter and shallow MLDs during summer. Transitional MLDs occur during spring and fall [3].

References:

1. Krokos, G., Cerovečki, I., Papadopoulos, V. P., Zhan, P., Hendershott, M. C., & Hoteit, I. (2024). “Seasonal Variability of Red Sea Mixed Layer Depth: The Influence of Atmospheric Buoyancy and Momentum Forcing.” Frontiers in Marine Science, 11, 1342137. DOI: 10.3389/fmars.2024.1342137
2. Alsaafani, M. A., & Alsaafani, M. A. (2018). “Mixed Layer Depth Variability in the Red Sea.” Ocean Science, 14(3), 563–573. DOI: 10.5194/os-14-563-2018
3. Alsaafani, M. A., & Alsaafani, M. A. (2021). “Seasonal Variability of Mixed Layer Depth from Argo Floats in the Central Red Sea.” Arabian Journal of Geosciences, 14, 563–573. DOI: 10.1007/s12517-021-06862-5 ¹²³

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