PMEL Programs and Plans
Accomplishments in FY 96 and Plans for FY 97
 
Figures (a) Digital camera image showing contact between new lava
flow at the Gorda Ridge
and the surrounding lava , and
(b) Cross section of a ridge crest hydrothermal system.
Ocean Environment Research Program
Accomplishments in FY 96
The VENTS project studies
hydrothermal venting systems. A multi-institutional, interdisciplinary rapid response
effort utilizing the NOAA Ship McArthur
and UNOLS vessel Wecoma
was carried out to study an active
volcanic eruption on the northern Gorda Ridge in March and April. Several
event plumes (megaplumes) were discovered during these rapid response cruises
and a fresh lava flow was mapped using a towed camera system. This is only the
second time a deep volcanic eruption along a portion of the global seafloor spreading
center has been detected and studied while the eruption was active. This event,
along with an eruption
in 1993 on the Juan de Fuca Ridge, is providing a wealth of new insights into
how such eruptions, the most common volcanic eruptions on Earth, affect the ocean
s chemical, thermal, and biological environments. The Gorda and Juan de Fuca eruptions
were detected and located using NOAA/PMEL's unique acoustic T- phase monitoring
system.
During the eruption event response, a novel new experiment was
successfully accomplished which made it possible, for the first time,
to track and study the evolution of the hot, chemically enriched plumes
associated with deep eruptions. This was done using a float which was
precisely ballasted to remain within the plume as it was carried by
deep ocean currents away from the eruption site. The float, which
regularly recorded its position, surfaced after two months of traveling
in the plume. Oceanographers were then able to map the movement of the
plume and study the plume s chemical and thermal evolution.
Collaborations continued with microbiologists at the University of
Washington to determine influences of hydrothermal fluid chemistry and
geology on the ecology of a vast, newly discovered subseafloor
biosphere as well as the species diversity of its microbial
inhabitants. A NOAA initiative is being considered to begin a major
research effort to understand and exploit this newly discovered
microbial resource.
Major new features of the helium tracer field were discovered and
published in Science. These new results, which include the first
detailed map of the Loihi seamount helium plume, provide a much clearer
map of deep ocean circulation in the north Pacific.
VENTS scientists completed an exhaustive three-year monitoring project
of the 1993 Juan de Fuca Ridge seafloor eruption. Among many notable
results, this effort yielded the first quantitative determination of
heat and mass fluxes from both episodic and quasi-steadystate
hydrothermal vent discharge during the entire life cycle of a
volcanically-generated hydrothermal system. The effort also resulted
in high- resolution, co-registered sidescan sonar and bathymetric maps
of the region where the eruption occurred.
In FY 96, the VENTS Program successfully deployed and then later recovered
very high-quaity acoustic data from an array of VENTS hydrophones which were designed to
augment the acoustic
monitoring being conducted using the Navy's SOSUS hydrophone arrays. The
VENTS hydrophones are currently deployed in the eastern equatorial Pacific where
they are monitoring seismic and volcanic activity along the most active portion
of the Earth s seafloor spreading center system.
VENTS physical oceanography studies focused on the central portion of
the Juan de Fuca Ridge, revealed the patterns of deep circulation that
transport plume water and hydrothermal effluent away from the vent
sources and incorporate them into the regional ocean circulation.
These studies showed that hydrothermal venting generates unstable
eddies that detach from vent plumes and transport plume material up to
at least 1000km away from the venting source.
A three-dimensional eddy simulation convection model was completed
which is now being used to investigate hydrothermal dispersion
processes and the distribution of chemical and thermal constituents in
and around hydrothermal plumes in the benthic water column. The model
is effective in evaluating methodologies adopted for the analysis of
hydrographic field data from hydrothermal venting regions.
Ocean Environment Research Program
Plans for FY 97
- Expand continuous plume monitoring program from north Cleft to south Cleft and Axial Volcano on the Juan de Fuca Ridge.
- Continue on ridge-crest processes and monitoring to determine flow changes affecting plume detachment from its source, effects of rift walls of circulation and plume dispersion and maintain moorings at N/S Cleft and Axial.
- Build and deploy an array of new instruments to measure seafloor spreading, as part of RIDGE Observatory.
- Analyze and publish results from CoAxial and Gorda Ridge expeditions.
- Continue to develop and use high-performance numerical models to look at the effects of hydrothermal discharge on the benthic ocean.
- Construct and ballast additional RAFOS floats for future volcanic event responses.
- Begin interpretation of FY 96 hydrothermal gas chemistry results in collaboration with U.S. and Japanese colleagues.
- Continue to broaden understanding of the interplay of chemical and geological processes with the volcanic and microbiology environments.
- Maintain SOSUS and autonomous hydrophone arrays/analysis.
- Begin development of real-time data link to autonomous hydrophones.
- Organize and lead expedition on NOAA Ship Ron Brown to map deformation of the Gorda Plate.
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