Southern Hydrate Ridge (PN1B)
Methane is a powerful greenhouse gas and, therefore, quantifying the flux of methane from the seafloor into the hydrosphere is critical to understanding carbon-cycle dynamics and the impacts of global warming on methane release.
Location: 44.6ºN 125.1ºW Water Depth: 780-771 meters
The Southern Hydrate Ridge study site (~10 km north of Primary Node PN1B) hosts abundant deposits of frozen methane (methane hydrates) that are buried beneath the seafloor. The deposits vent methane-rich fluids and bubbles that escape through seeps on the ocean bottom. Dense and fascinating communities of microbes and animals are fueled by these escaping gases. Methane is a powerful greenhouse gas and, therefore, quantifying the flux of methane from the seafloor into the hydrosphere is critical to understanding carbon-cycle dynamics and the impacts of global warming on methane release.
Southern Hydrate Ridge is an important observatory site to define the temporal evolution of methane hydrate systems in response to seismic events. It is also an important area to quantify material fluxes from the seafloor and the impacts of methane release on overlying ocean chemistry. It provides an excellent opportunity to understand biogeochemical coupling associated with gas hydrate formation and destruction.
The real-time and interactive capabilities of the cabled observatory are critical to studying gas-hydrate systems because many of the key processes may occur over short time scales. Events such as bubble plume formation, the creation of collapse zones, and increased seepage in response to earthquakes will require adaptive response and sampling capabilities that include full-resolution sampling by upward-looking sonars, fluid and gas sampling, long-term duration collection of plume and seep imagery from cameras, and in situ manipulation of chemical sensors, which, coupled with flow meters, provide estimates of transient and more stable chemical flux.
During the UW-RSN-OOI-NSF VISIONS'13 Expedition, two uncabled benthic flow meters were deployed at this site in preparation for the full installation of infrastructure here in 2014. A caisson was also buried in the sediment for follow-on installation of a broadband seismometer to study local and regional seismic events.
The chemical, biological, and geophysical sensors that will be installed at this site in 2014 will allow the first long-term, detailed investigation of such questions as the effects of seismic events on the release of hydrates and methane gas into the overlying ocean, and the changes in microbial and animal communities over time. In situ cameras, flow sensors, and a mass spectrometer will allow investigation of how changes in fluid flow and chemistry impact the biological communities that thrive in this environment.
Instruments to be installed at this site include the the following:
3 Benthic Flow Sensors (2 installed in 2013)
1 Osmo Fluid Sampler
1 Broadband Seismometer with an accelerometer
1 Low-frequency Hydrophone
3 Short-period Seismometers
1 Mass Spectrometer
1 Digital Still Camera
1 Current Meter
1 Pressure Sensor