Drifting and Meandering of Olive Ridley Sea Turtles in the Bay of Bengal: Role of Oceanic Rossby Waves

Abstract

Olive Ridley turtles in the Bay of Bengal are previously thought to migrate southward from their nesting ground, along the east coast of India (Orissa coast), towards Sri Lanka. Surprisingly, three of the four Platform Transmitter Terminal (PTT) attached turtles in April-June 2001 meandered off the east coast of India for about two months. It is found that these turtles meandered at the peripherals of cold core cyclonic eddy surrounded by warm core eddies on either side. Concentrations of prey for the turtles in those frontal regions are known to be abundant. Only one of the four PTT attached turtles migrated to the south along the frontal regions in the direction of geostrophic currents. It is found that the locations of these thermal fronts in the Bay of Bengal are primarily determined by the Oceanic Rossby waves and local Ekman pumping.

Keywords:

• Bay of Bengal
• circulation
• cyclonic and anti-cyclonic eddies
• Olive Ridley turtles

Acknowledgements

Thanks to CLS Space Oceanography Division and CNES for making the SSHA data available on the Internet. The authors are also thankful to Dr. Mahendra of INCOIS, Hyderabad, for helping us in digitizing the turtle tracks using ERDAS software. The altimeter products (downloaded from ftp://ftp/cls.fr/pub/oceano/msla) were produced by the CLS Space Oceanography Division as part of the Environment and Climate EU ENACT Project (EVK2-CT2001-00117) and with support from CNES. This is NIO contribution No. 4557.