Morphologic features, 600-1100 m across and elevated up to 30 m above the surrounding seafloor, interpreted to be mud volcanoes were investigated on the continental slope in the Beaufort Sea in the Canadian Arctic. Sediment cores, detailed mapping with an autonomous underwater vehicle, and exploration with a remotely operated vehicle show that these are young and actively forming features experiencing ongoing eruptions. Biogenic methane and low-chloride, sodium-bicarbonate-rich waters are extruded with warm sediment that accumulates to form cones and low-relief circular plateaus. The chemical and isotopic compositions of the ascending water indicate that a mixture of meteoric water, seawater, and water from clay dehydration has played a significant role in the evolution of these fluids. The venting methane supports extensive siboglinid tubeworms communities and forms some gas hydrates within the near seafloor. We believe that these are the first documented living chemosynthetic biological communities in the continental slope of the western Arctic Ocean.

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Globally, the burning of fossil fuels for energy production produces over 25 gigatons of CO 2 per year and this material is released directly into the atmosphere. While approximately half of the CO 2 has remained in the atmosphere long-term, most of the rest has been absorbed by the surface ocean. This has resulted in a lowering of the surface ocean pH by about 0.1 units since the beginning of the industrial revolution and if society is able to stabilize atmospheric CO 2 levels at twice their pre-industrial concentrations will result in a lowering of surface ocean pH by 0.25 units. While many are asking the question of whether we should pursue direct ocean CO 2 sequestration, the FOCE experiment is asking what will be the impact of the pH change on the ocean. In order to address this question, MBARI science and engineering have designed a smallscale in situ CO 2 enrichment experiment to assess the chemical and biological impacts in a manner analogous to the land-based Free Air CO 2 Enrichment (FACE) experiments. This prototype design is testing the ability to control pH within a fixed but freely exchanging volume of sea water. The technology concept for the experiment is based on a small ring structure using a central valve to direct the flow of pH altering fluid. The initial phase of the project uses concentrated HCl mixed with sea water and includes directional and volume control to achieve a desired pH offset. Control feedback is obtained by using pH sensors in the center of the control volume. Other aspects of the design that address the inherent time delays and noise of the associated pH signal are also discussed. Test results will show the capability of the system to maintain close loop control of pH in a given volume. Sea trials then demonstrate the ability of this initial system at a selected site to control pH to specified average level over a given amount of time. Further discussion includes systems in-situ results analysis, corrective actions, upgrades, and the anticipated next phase for FOCE including the use of CO 2 addition to change the local chemistry.

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