In 2019, the Arabian Sea witnessed a meteorological onslaught that defied historical norms, seeing five significant tropical cyclones and nine distinct marine heatwaves in a single year. A team of researchers from the Indian Institute of Technology Bombay and the Indian Institute of Remote Sensing has now pinpointed the cause as a record-breaking extreme positive phase of the Indian Ocean Dipole (IOD).
IOD is a phenomenon where sea-surface temperatures oscillate between the western (warmer, near Africa) and eastern (cooler, near Indonesia) tropical Indian Ocean. This climate phenomenon acted like a giant internal pump, driving massive amounts of heat into the deep waters of the Arabian Sea and creating a buffet of energy that allowed storms to form and intensify back-to-back. The new study shows that the ocean’s surface temperature reached a historical record, exceeding its previous index by 2.1°C, providing the perfect conditions for the most intense cyclone season the region has seen in decades.
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While earlier works often attributed 2019’s storminess to a weak El Niño, this study proves that the extreme Indian Ocean Dipole and its impact on subsurface heat were the primary drivers. It provides a more three-dimensional view of how the ocean stores energy.
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