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To An Underwater Lake

Mussels at the edge of Brine Pool. Photo by Bob Waters
Mussels at the edge of Brine Pool. Photo by Bob Waters

Sitting in a submersible 650 meters beneath the ocean  is a surprisingly serene experience. The pitch and roll that you feel at the surface disappears moments after you’ve submerged, and from then on you exist in a sphere of perfect stability. When the sub reaches the bottom, the pilot adjusts to a neutral buoyancy so that the vehicle hovers, literally weightless, in the water. In clear water it’s easy to imagine that you’re flying over the dry land of Earth, rather than floating over its seafloor.

All of which makes the experience of seeing a lake at the bottom of the ocean a little bit easier to believe.

Brine Pool was first discovered by a navy survey in the early 1980s. It’s a upwelling of highly saline water, the density of which makes it poorly miscible with the ocean around it. This means the brine sits heavy on the seafloor, acting for all of the world like a terrestrial lake. Small brine waves lap up against its shoreline. Animals skitter across its surface. Did I mention it’s surreal?

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Mussel beds make up the beach at Brine Pool, an underwater lake at the bottom of the Gulf of Mexico. Photo by Bob Waters

The ‘shores’ of the Pool are mussel beds, richly populated with invertebrate life. Smaller mussels exist most densely near the edge of the brine, while at the outer edges of the ‘beach’ are mostly bigger, older mussels. Why does this gradation of age groups occur?

The things that are unknown about Brine Pool far outweigh the things that are known. On top of the mussel question, we don’t know how deep it is, or how old it is, or whether it’s growing or shrinking. Very little is known about the consistency of the brine, or if it harbors animal life of its own.

During today’s Alvin dives, the team collected mussels at several different sites along the beach. Tomorrow, a sample of the brine at the center  will be collected and later analyzed. It’s possible that the resulting data will help us understand a bit more about Brine Pool.

But it will remain a very, very strange place.

Alvin dive #4723
Navigation data plot from Alvin dive to Brine Pool. Image by Jer Thorp

The image above is a visualization of my dive to Brine Pool. Tomorrow I’ll share some of the data explorations I’ve done with Alvin‘s data stream.