Indian Ocean Dipole - An explainer

Published onĀ Nov 5, 2022

Out of the 5 oceans on the earth, the Indian Ocean is the warmest. The Indian Ocean, the third-largest, is landlocked in the northern area of the Indian subcontinent. It is surrounded by Australia in the east and Africa in the west, being home to a vast ecosystem.

A dipole is nothing but a couple of opposite poles separated by some distance, similar to that of a magnet we usually see.

Now, what does the Indian Ocean have to do with diploes?

Rains are usually guided by the winds and most of the winds we see are a result of pressure and temperature differences. The differences tend to matter a lot when we talk about oceans, which has vast control in the way we live.

IOD or Indian Ocean Dipole refers to the relative heat changes in the tropics of the western Indian Ocean and the eastern Indian Ocean. Two ends that have opposite sides, like a magnet. These changes affect the weather patterns of the countries surrounding it.

The below picture is one such depiction of such differences in temperatures of the Indian ocean.

Source: BBC

IOD could be +ve, -ve, neutral.
If its warmer than average on the west and cooler on the east, then IOD is positive.
If its cooler than average on the west and warmer on the east, then IOD is negative.
If there is a low difference in temperature, then IOD is neutral.

The water inside the oceans moves from the east to the west, causing warmth to circulate. These are nothing but wind patterns. In simple terms, the clouds move in the direction of warmer winds.

Such an increase in the extreme dipole causes the weather to be extreme, either heat or rain or cold.

Warm air creates low pressure inviting more clouds and rainfall to happen.

For example, positive IoD (warmer near the African coast), pushes the southwest monsoon to India. If this tends to be intense then it results in more rain than normal.

And in recent years this has become more common. The recent events in Ethiopia stand a testament. One part of the country face heavy rains while the other had severe droughts.

This is because of the changing ocean temperatures, a result of global warming, causing a shift in how we experience seasons and weather.

How about the Indian monsoon? Is it all down to the same changes in IOD? Not exactly. There is also one more effect in the Pacific Ocean that results in how our seasons behave, which is covered in our next blog

Written by Zodhya

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