Sunday May 5, 2019
By Milafel Dacanay
Using satellite data, NASA scientists learn more about the giant vortex (not the picture) that grows annually near Somalia, Africa. Called the Great Whirl, it may be large enough to have significant impact on India’s monsoon season. It may also be bigger than Colorado. ( Pixabay )
Somewhere along the coast of East Africa is a giant ocean vortex NASA scientists couldn't research well until they began to look into the satellite data covering 23 years.
The information they obtained revealed so much more about the Great Whirl, including its boundaries and size that makes it much larger than previously thought.
The Challenges Of Measuring The Ocean Vortex
Many people already know that the Great Whirl exists. One of the earliest accounts went back to 1866 when Alexander Findlay, English geographer, mentioned it in his navigational directory.
He described it as a big current whirl, which develops every time the winds that blow across the Indian Ocean change direction to west from east.
It also appears every year, and for the scientists back then, it was as large as Colorado. They couldn't exactly get the right measurements of the boundaries.
They could consider putting trackers into the ocean, but the threat of Somali pirates prevented them from coming near the area.
This method of monitoring can also mean a long period, even years, to provide a more thorough observation of the phenomenon.
They also knew that the whirls meant strong currents and waves, and their presence tend to coincide with the official monsoon season of India.
The limitations forced NASA to think of other ways to keep track of its appearance, which led them to satellite images.
They learned that the center point of the giant vortex rises above the sea level. The currents, meanwhile, then revolve around the center. They then could already define the boundaries of the whirl.
They looked into the satellite data of sea levels within the area from 1993 to 2015. From these, they discovered how the whirl's size changes over time, how long it appears, and its behavior at different climatic conditions.
How Big Is The Great Whirl?
Based on their analysis now published in Geophysical Research Letters, the Great Whirl is truly massive. Although the year-over-year sizes can vary, the average size within the studied period was 275,000 square kilometers (106,000 square miles). It is therefore bigger than Colorado.
A 2013 research cited the width can span not less than 500 kilometers (300 miles), which makes it longer than the Grand Canyon.
The circular currents, meanwhile, can be deep. It can travel as deep as 1 kilometer (0.62 miles) in certain areas.
When it comes to their duration, the satellite data revealed it can be different annually. However, it's much longer than scientists predicted at 140 and 166 days.
Their analysis revealed they tend to stay for more than six months or 198 days, on average.
The current is at its deepest and strongest during June to September, which matches that of the monsoon season of India. In some cases, though, it can linger all the way to the following year.
The Implications Of The Whirl
The information from the satellite data may bode well for the people in India's agriculture, which is a trillion-dollar economy.
"If we're about to connect these two, we might have an advantage in predicting the strength of the monsoon, which has huge socioeconomic impacts," said Bryce Melzer, lead author of the study.
The methods may also help them understand the other whirlpools around the world, including one in Gulf of Mexico.