by Kip Evans,
SEAlliance Director of Expeditions and Photography
Deep Worker (c) Kip Evans
In 1977, Alvin, the first untethered manned submersible, was used to confirm theories of seafloor spreading along the Mid-Atlantic ridge. Much to the amazement of scientists, the area was home to a thriving community of organisms living in extremely hot, sulfuric rich water. This discovery, along with hundreds of others, has made Alvin and other manned submersibles, one of the most valid oceanographic tools in the world.
During the past 30 years there has been a lot of debate about the need for using manned submersibles. After all, we have high-tech remotely operated vehicles (ROVs) capable of probing the ocean depths without depositing a single person in the water. They are less expensive to operate, safer, and in some ways easier to maintain.
But as a submersible pilot, I have experienced first-hand the profound importance of human observation. As a first person observer, you have the ability to see and sense objects around you that are nearly impossible to catch on a television monitor from the deck of a ship. In 2000, while diving in deepwater off the coast of Lanai Hawaii, chief scientist Dr. Sylvia Earle noticed a large figure hanging in the water column just outside the beams of her lights. At first she thought it was a piece of trash, but after investigating, she came upon a large deep-sea octopus. The encounter as it turns out, would be one of the highlights of the expedition and quite possibly her career. Had she been relying on just an ROV for the expedition, she would have missed this opportunity. It’s also safe to say that thousands of people would have not been touched by the story Dr. Earle has told countless times during her travels around the world.
Manta Rey / Flower Garden Banks (c) Kip Evans
During a 2001 cruise to the Flower Garden Banks with the Sustainable Seas Expeditions, I was participating in a 4-hour dive to look for methane gas seeps. The Flower Garden Banks are about 100 miles (160 kilometers) off the coast of Galveston Texas and is a National Marine Sanctuary site that is known for its’ immense boulder corals, schooling fish, and large pelagic visitors. During my dive, I caught a glimpse of a sizable animal trailing off the starboard-rear portion of the sub. The animal was uninterested in the sub’s bright HID lights, but he or she was very curious about the vessel. Because I sensed the problem, I turned-off the starboard side light and the animal immediately came to the front of the sub. As it turns-out, it was a large manta ray, with a 12-15 foot (4-5 meter) wingspan. For over an hour, the ray swam in front of the camera guiding me over one large reef section after another. We never did find the methane seep, but it was trivial compared to the encounter with the ray, possibly one of the few encounters of this type ever documented.
Deep Worker (c) Kip Evans
The benefit of using manned submersibles goes beyond the wonderful encounters described above. For example there are technical considerations that make manned submersibles a better option. Most ROVs are tethered to the surface by a large umbilical cable, which can be a major disadvantage. As an ROV dives deeper, the cable becomes heavier and creates more drag on the vehicle. This drag can create problems while diving in heavy currents, complicated terrain, or in substantial swells. Untethered subs on the other hand, allow a pilot the flexibility to move about freely without the restrictions of that trailing weight. Today there are untethered ROVs called autonomous underwater vehicles (AUVs), which can run for long distances without an umbilical cord. Utilization of AUVs will surely expand, however no technology currently can compare to being there in person – intellect that is lost through the use of such devices.
|Unmanned Submersible (c) Kip Evans|
However, manned submersibles also have their limitations. In locations with hazardous bottom terrain, rough seas, tight quarters, or a high likelihood of bottom entanglement, submersibles are nearly impossible to deploy. In these situations ROVs are clearly the better choice.
Looking towards the future, I think we will continue to see growth and development of submersibles and AUVs, both of which can substantially improve oceanographic research opportunities. Are subs the clear choice for SEAlliance expeditions? At this point yes, as they provide a better platform for not only exploration, but also raising awareness – one of our core objectives. The biggest challenge of course is making use of these vehicles at an affordable price.