Chief Scientist, Bob Embley.

Science Summary for NeMO 2002

This year's expedition to NeMO at Axial Volcano was shorter than in previous years and so it was particularly intensive with as much science as possible packed into each day on site. We made 4 ROPOS dives, with a total of 69 hours of bottom time, and a total of 58 samples collected. Between ROPOS dives we deployed or recovered 6 oceanographic moorings, deployed or recovered 4 seafloor instrument packages, and conducted 5 CTD casts. One of our main goals at Axial Volcano this year was to install an upgraded NeMO Net system. NeMO Net is a state-of-the-art communication system that links desktop computers on land to instruments on the seafloor. A surface buoy is the heart of the system, which communicates with shore by satellite and to the seafloor via an acoustic link. We have been incrementally developing the capabilities of NeMO Net over the last 3 years, starting with one-way communication from a single camera, to this year's system which has two-way communication with three independent instruments on the seafloor. The 3 instruments include two interactive fluid samplers (called RAS's) and one bottom pressure recorder (BPR). The whole idea of NeMO Net is to be able to get information from the seafloor in order to be able to know when a volcanic event is occurring at Axial Volcano and then be able to respond to such an event immediately, without having to wait until a ship can get out to the site.

During our dives with ROPOS we were also able to recover many instruments and experiments that had been left last summer. These included a RAS sampler at Cloud vent that successfully took 1 fluid sample per week for the year, many probes that had been continuously monitoring temperature at various vent sites, and bacteria traps at some of the same vent sites. Particularly successful was an experiment which offered a variety of artificial and natural substrates in order to see which the larvae of vent animals might prefer. Vent animals were found to colonize in some areas where none are observed on the seafloor, probably due to a lack of appropriate substrate.

Another experiment new to NeMO 2002 uses special "chambers" that can simulate the high pressure that the animals live under at the vents. The chambers provide a means to test hypothesis related to the extreme environmental conditions the animals can tolerate. For example, some observations suggest that worms living on the smoker chimneys can tolerate temperatures up to 176° F (80° C)! The "chamber" experiments with their animals are designed to test this hypothesis.

Pressure measurements were made in two different ways for two different purposes. Bottom pressure recorders (BPRs) record continuously over a year and look for sudden deflation events that signal the onset of a volcanic eruption or intrusion. But these instruments have a long-term drift rate so they are not good at measuring volcanic inflation, which occurs at a gradual rate over long periods of time. To try to measure the inflation signal we are using another pressure sensor that ROPOS can carry to seafloor benchmarks. With this instrument we can determine the relative depths of the benchmarks and determine if the ones inside the caldera are being uplifted relative to the one located outside the caldera. We repeat these measurements annually to look for changes. These data take several weeks to analyze, so this year's results are not yet available.

We plan to be back at NeMO again next summer to recover and deploy these kinds of long-term experiments and monitoring instruments so that we can continue to learn about the NE Pacific's most active submarine volcano. We know relatively little about how submarine volcanoes work, as compared to more accessible volcanoes on land, but with long-term seafloor observatories like NeMO we are making dramatic progress in our understanding.