Subject: Physical Geography

The sea surface temperature (SST) represents the temperature of the ocean's upper layer, which has experienced significant warming due to anthropogenic climate change and natural variability. Oceans absorb nearly 90% of the excess heat trapped by greenhouse gases, leading to a steady increase in sea surface temperatures.

Understanding Sea Surface Temperature Rise

• Global Warming Impact: The Indian Ocean is experiencing a concerning warming trend of 1.7-3.8°C per century, indicating accelerated thermal absorption.

• Regional Variations: While some regions like the equatorial Indian Ocean showed near-average temperatures in March 2025, other areas exhibited above-average SSTs in January 2025.

• Heat Exchange: SST rise affects the ocean-atmosphere interaction, influencing heat flux, evaporation rates, and atmospheric circulation patterns.

Impact on Tropical Cyclone Formation

Formation of Tropical Cyclones

Prerequisites for Cyclogenesis

• Temperature Threshold: SSTs of 28-29°C or higher create favorable conditions for cyclone formation in the Arabian Sea and Bay of Bengal.

• Energy Transfer: Warmer waters enhance heat and moisture transfer to the atmosphere, providing the necessary fuel for cyclone development.

Changes in Cyclone Patterns

• Spatial Distribution: The traditional 4:1 ratio of cyclones between the Bay of Bengal and Arabian Sea is shifting due to warming trends.

• Arabian Sea Intensification: Recent decades have witnessed a 1.2-1.4°C increase in cyclogenesis-supporting SSTs in the Arabian Sea compared to previous decades.

• Rapid Intensification: For instance, Cyclone Amphan (2020) in the Bay of Bengal rapidly intensified into a super cyclone due to SSTs exceeding 30°C

Impact on Cyclone Characteristics

• Rainfall Intensity: Higher SSTs lead to increased precipitation during cyclonic events.

• Wind Velocity: Warmer waters contribute to stronger wind speeds and more intense storms.

• Track Modification: Rising SSTs can influence cyclone trajectories and their geographical distribution.

Rising sea surface temperatures have emerged as a critical factor in shaping tropical cyclone behavior, as evidenced by the increasing frequency of rapid intensification events in regions like the Gulf of Mexico and Caribbean Sea, necessitating enhanced disaster preparedness and climate adaptation strategies.