For the first time, researchers have been able to observe double whirlpools, and they monitored not just one but nine different pairs through the use of satellite imagery.
The Earth's oceans are filled with currents that are constantly moving in different directions, which is why it is uncommon for opposing currents to pinch off and create circular motions called whirlpools or eddies.
Eddies are mostly harmless and short-lived. They even contribute to healthy marine life by bringing nutrient-rich waters from below the ocean up to the surface. However, there are also some spanning a hundred kilometers across and moving at speeds that could destroy seacrafts.
Modons Prove Double Whirlpool Theories Are Correct
Double whirlpools or modons only existed in theories, as their small scale and fast speed have both made observation difficult. They were only predicted to travel much faster than average eddies while remaining paired up for a long period. These modons have also been thought to be capable of moving to the east, a direction unusual to whirlpools, as they normally travel to the west.
Chris Hughes of the University of Liverpool and Peter Miller of Plymouth Marine Laboratory have proven this theory to be correct as they observed the nine pairs from outer space. Using all satellites distributed by AVISO+, they measured ocean levels as well as the temperature of its surface from 1993 to 2016.
In a study published Dec. 4 in Geophysical Research Letters, the two researchers report spotting eight eddy pairs across Australia's mid-lateral oceans and one in the South Atlantic, west of South Africa. Formations were seen on different dates, but they occurred intermittently within the southern mid-latitude region. This led researchers to believe that formation of modons is possibly localized to such area.
Discovery Of Eddy Pairs Present More Mystery For Researchers
Moreover, Hughes and Miller noted that double whirlpools stayed together for six months and traveled at long distances of more than 1,000 kilometers before they split up. They move 10 times faster than an average whirlpool but are capable of traveling toward the east, a direction that is not commonly taken by eddies.
"The smoke rings require an area of calm water to 'puff' out through, which itself is quite unusual," says Hughes in a statement. "My thinking is that these linked, fast moving eddies could 'suck-up' small marine creatures and carry them at high speed and for long distances across the ocean."
The researchers have also found that modons are made of waters with different content. A double whirlpool spotted in the Tasman Sea carried water with deep oxygen content as well as high salinity value. Both properties made the researchers conclude that double whirlpools are not only ecologically beneficial by replacing nutrient-depleted surface water but are also responsible for sustaining deep-water marine life.