Recent changes in the upper oceanic water masses over the Indian Ocean using Argo data

Area of Science:

• Oceanography
• Climate Science
• Geophysics

Background:

• The Indian Ocean is a critical region for global climate regulation.
• Understanding thermohaline circulation changes is vital for predicting future climate scenarios.

Purpose of the Study:

• To analyze thermohaline changes in the Indian Ocean upper 700m from 2003-2019.
• To decompose thermohaline trends into spice and heave components.
• To identify the primary drivers of salinity and temperature changes in regional water masses.

Main Methods:

• Utilized Argo float data from 2003 to 2019.
• Analyzed thermohaline trends in the upper 700m of the Indian Ocean.
• Decomposed trends into spice and heave components, linking them to pure heave, freshening, and warming processes.

Main Results:

• Widespread warming observed, except in the Southern Indian Ocean; salinity increased across most regions, excluding the Bay of Bengal and Southern Indian Ocean.
• Consistent patterns include spice dominating heave below 300m, freshening as the primary driver below 300m, and spice influencing salinity along isobars.
• Regional variations noted: Arabian Sea warming driven by spice, Indian Equatorial Water by heave, and Bay of Bengal freshening by heave and pure freshening.

Conclusions:

• Thermohaline changes in the Indian Ocean are complex, with spice and heave dynamics playing crucial roles.
• Freshening, particularly below 300m, is a significant factor influencing salinity trends.
• Understanding these processes is key to predicting the impact of climate change on the Indian Ocean.