Southern Indian Ocean rapidly losing salt; Scientists warn of global impact

A study has found that salinity levels in parts of the southern Indian Ocean have declined by nearly 30% over the past 60 years.

Post Published By: Sujata Biswal

Updated : 19 February 2026, 1:59 PM IST

The Southern Indian Ocean is losing its salt

New Delhi: For decades, the Indian Ocean has ranked among the saltiest ocean basins on Earth. But new research suggests that this long-standing balance is rapidly shifting.

A study by researchers at the University of Colorado Boulder has found that salinity levels in parts of the southern Indian Ocean - particularly off the west coast of Australia - have declined by nearly 30% over the past 60 years. Scientists warn that such a dramatic drop could have far-reaching consequences for ocean currents, global climate systems, rainfall patterns, and marine ecosystems.

Climate Change Driving the Shift

Using advanced computer simulations, researchers linked the freshening trend directly to climate change. Rising global temperatures are altering surface wind patterns over both the Indian Ocean and the tropical Pacific. These wind shifts are pushing more freshwater from tropical reserves into the southern Indian Ocean.

As seawater becomes less salty, its density decreases - a seemingly small change that can significantly disrupt ocean circulation.

What It Means for India

The findings are particularly significant for India. The Indian Ocean plays a crucial role in shaping the Indian monsoon system. Any disturbance in its salinity and circulation patterns can influence:

• Monsoon rainfall
• Marine fisheries
• Coastal weather systems

Because global oceans are interconnected, even regional changes can affect weather patterns in Europe, Asia, and Africa.

Threat to the Ocean’s “Conveyor Belt”

Ocean circulation operates like a giant conveyor belt, distributing heat, salt, and freshwater around the globe. Variations in salinity help drive this system. While the average global ocean salinity stands at about 3.5%, regional differences are essential to maintaining circulation balance.

The southern Indian Ocean - near southwest Australia - has traditionally been more saline compared to tropical regions stretching toward the western Pacific. That contrast helps power global circulation. Scientists warn that weakening this salinity gradient could disrupt key climate-regulating systems.

Experts say continued freshening may alter critical ocean-atmosphere interactions - with consequences that extend far beyond the Indian Ocean itself.