Diving on the Wrong Side of the Indian Ocean Dipole

Unusually cold water and poor visibility in the Andaman Sea have led to below average dive conditions in Southeast Asia so far this year. To blame is the Indian Ocean Dipole.

Unusually cold water and poor visibility in the Andaman Sea, unseen for the last 60 years, have created below average dive conditions in Southeast Asia this year, although conditions have also led to new marine encounters. For both, the Indian Ocean Dipole is to blame.

Scuba divers are often at the whim of the weather and the ocean. Booking a dive vacation months in advance usually involves research into the seasons and the weather in the area when we wish to go. Unfortunately, all the research in the world can’t always save you from the guiles of mother nature.

This was the case this year in areas of Southeast Asia, including the Mergui Archipelago in Myanmar. Normally, divers can fairly confidently plan a trip to this part of the world to avoid the monsoon or hot seasons. The best diving here is typically from November until April. But in early 2020, a climatological phenomenon known as an Indian Ocean Dipole foiled the plans of many divers in this part of the world.

What is the Indian Ocean Dipole?

The Indian Ocean undergoes yearly changes in surface temperature, called the Indian Ocean Dipole (IOD). This occurrence, discovered in 1999 by climate researchers, alternates between three distinct phases, which reoccur every three to five years. These phases affect the weather systems in the surrounding land and water masses in different ways. The neutral phase brings warm water from the Pacific Ocean throughout Indonesia and westerly winds along the Equator, which keep temperatures relatively normal across the tropical seas. Positive and negative phases tend to create a gradient in temperature across the ocean, which affects surface temperatures and rainfall on either side of the vast body of water.

This year saw a particularly strong positive phase, the likes of which hasn’t happened for six decades. Westerly winds became weaker, which caused a shift in those warm waters toward the western side of the ocean. This resulted in little rainfall and rising cold waters from the depths on the west coast of Thailand and Myanmar and surrounding seas.

“We’ve never had such cold water in nine years,” said Franck Fogarolo, owner of The Smiling Seahorse, an expert when it comes to diving Myanmar since 2012. With temperatures as low as 68 F (20 C) on some dives, guides loaded the boat with extra shorties to offer as extra layers on top of long wetsuits.

Unique ocean encounters

While a bit cold, the divers visiting this season did encounter some fairly special creatures. The cold water brought a lot of nutrients to the shallow areas, attracting a lot of marine life not usually visible in the first 100 feet (30 m). “We saw over 40 guitarfish on a single dive in Black Rock in March 2020,” Fogarolo said enthusiastically.

This past season featured unique sightings such as silvertip sharks, guitarfish (otherwise known as the long-snout shovelnose ray), and little dragonfish. Although this season was not representative of the usual diving conditions in the Mergui Archipelago, the return of better conditions for seasons to come is expected.

Experts say that in an average 30-year period, the ocean will undergo roughly four each of positive and negative phases, which last about six months each. Models also suggest that consecutive positive phases will only occur twice over every 1,000 years. This past season may have brought rare conditions, including cold water, poor visibility and strong thermoclines, but warm, clear waters are likely on tap for the coming 10 years.

Located off the coast of Myanmar, the Mergui Archipelago is made up of more than 800 islands, for the most part uninhabited. The MV Smiling Seahorse, a new liveaboard launched in November of 2018, can bringing up 16 divers to some of the most unexplored dive sites of Southeast Asia.