London, Nov 18 (IANS): Owing to growing international trade, maritime traffic on the world's oceans has increased four-fold over the past 20 years, causing more water, air and noise pollution on the open seas, says a new research.

In the Indian Ocean, where the world's busiest shipping lanes are located, ship traffic grew by more than 300 percent over the 20 year period, the findings showed.

Traffic went up in every ocean during the 20 years of the study, except off the coast of Somalia, where increasing piracy has almost completely halted commercial shipping since 2006.

"The new study is the first to track ship traffic on a global scale," said study author Jean Tournadre, a geophysicist at IFREMER, the French Institute for the Exploitation of the Sea.

"I found it quite worrisome that the ship traffic grew so much, even in very remote regions of the world," Tournadre added, "especially when we know that they are the major source of pollution (on the open ocean)".

The research used satellite data to estimate the number of vessels on the ocean every year between 1992 and 2012.

The number of ships traversing the oceans grew by 60 percent between 1992 and 2002.

Shipping traffic grew even faster during the second decade of the study, peaking at a rate of increase of 10 percent per year in 2011.

Ships powered by fossil fuels dump oil, fuel and waste into the water and pump exhaust into the air.

Shipping is also a major source of noise pollution, which is considered to be potentially harmful to marine mammals, Tournadre said.

The study is forthcoming in the journal Geophysical Research Letters.