Context: A recent study revealed that deep waters (below 1200 metres) in the Andaman Sea are about 2 degrees Celsius warmer than the Bay of Bengal due to internal tide mixing.

• The study was conducted by Indian National Centre for Ocean Information Services (INCOIS).

Key findings

• Internal tide energy dissipation and associated vertical mixing play a major role in maintaining the warmer temperature in the deep Andaman Sea (AS).
• The rate of vertical mixing in the AS is about twice than in the Bay of Bengal.
• This elevated internal tide induced vertical mixing results in the efficient transfer of heat into the deeper layers, which keeps the deep Andaman Sea warm.

Temperature distribution in the deep ocean plays an important role in:

• Regulating the deep ocean circulation
• Water mass formation
• Distribution of chemical properties
• Distribution of marine organisms
• The small exchange of deep waters, and higher temperature decreases the solubility of gases, which contributes to the biogeochemical properties of the sea.
• Andaman Sea contains higher concentration of dissolved Rare Earth Elements compared to Bay of Bengal.

Internal tides

• Internal tides are internal waves forced by the interaction of the barotropic tides with the bottom topography of the oceans.
• They are generated as the surface tides move stratified water up and down sloping topography, which produces a wave in the ocean interior.
• In the deep ocean, tides supply much of the mechanical energy required to sustain mixing via the generation of internal waves.
• They do have a vertical structure.

Andaman Sea
Andaman Sea is a part of Indian Ocean which is located in:

• East of the Andaman & Nicobar Islands (India)
• West of Thailand and South of Burma
• It is also known as Burma Sea.

Additional Information
Tidal-induced deep-sea mixing plays an important role in:

• Controlling the distribution of heat and carbon in the ocean
• Helping drive global ocean circulation
• Force nutrients up from the deep which can be used by tiny plants at the sea surface (base of the ocean’s food web).