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Riding the Waves of Change: How Does the Indian Ocean Dipole (IOD) Impact Marine Life in the Andaman Sea?


The Indian Ocean Dipole (IOD), also known as the Indian Niño, is a climatic phenomenon that significantly impacts marine ecosystems across the Indian Ocean, including the Andaman Sea, which serves as our home turf for the Asia Pacific region.


Similar to the El Niño Southern Oscillation (ENSO) in the Pacific Ocean, the IOD is characterized by fluctuations in sea surface temperatures and atmospheric pressure between the western and eastern parts of the Indian Ocean.


In the Andaman Sea, which is a vital habitat for marine life and a focal point of Shark Guardian's conservation efforts, the effects of the IOD are particularly pronounced. For instance, during December 2023, sea temperatures plummeted as low as 24°C (75.2°F), averaging around 26°C (78.8°F) so far during 2024, compared to the typical 29°C (84.2°F). These deviations from the norm are clear indicators of the influence of the IOD, especially its negative phase.


A graphic of jhow an IOD works
The IOD Oscillates like a Pendulum

The IOD functions as a climate pattern, oscillating like a pendulum and exerting influence over weather and oceanic conditions throughout the Indian Ocean region and beyond. It manifests in two distinct phases – positive and neg


During a positive Indian Ocean Dipole event, warmer-than-average sea surface temperatures in the western Indian Ocean contribute to enhanced rainfall over eastern Africa and drier conditions in southeastern Australia.


A negative IOD event, which is what we’re currently seeing,  leads to decreased sea surface temperatures and the formation of thermoclines, which are boundaries between water layers of different temperatures. Such changes in oceanic conditions have profound effects on marine ecosystems, including the diverse array of species that call the Andaman Sea their home, such as sharks.


A bullshark swimming in the sea in Thailand
A bull shark captured in February 2024 at Koh Haa, Thailand by Fabian Clinton

Rarely observed (in this area) marine life, such as the Longrakered Trevally, have been commonly sighted during this phenomenon in the Andaman Sea, possibly attracting the seldom-seen bull shark, which has also been spotted frequently this year.

A longrakered trevally photographed in the Andaman Sea
Longrakered trevally - photo taken by Fabian Clinton (@foffo4) at Koh Haa, Thailand

For Shark Guardian, understanding the dynamics of the IOD and its impacts on marine environments is crucial for effective conservation efforts. By closely monitoring these fluctuations, we can assess the health of shark populations and their habitats in the Andaman Sea and beyond. 


Shark Guardian may adapt its conservation strategies in response to changing environmental conditions, implementing measures such as habitat protection and educational initiatives to address the challenges posed by climate variability in these vital marine ecosystems. Through these efforts, we strive to ensure the long-term survival and prosperity of sharks and other marine species in our home turf and beyond.


We are solely relying on donations to fund our conservation efforts. If you'd like to help, please go to our donation page or treat yourself to something fabulous from our online shop!














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