PMEL Programs and Plans
Accomplishments in FY 99 and Plans for FY 00

Hydrothermal Venting Project

Accomplishments in FY 99

• The discovery of several previously unknown hydrothermal vents south of Axial caldera in a new lava flow.
• High-resolution sea-floor mapping in the northern portion of the new lava flow using the Imagenex sonar system mounted on ROPOS
• An array of seafloor miniature temperature recorders (SMTRs) was deployed near several seafloor vents in the Axial caldera to monitor trends in individual vent temperatures, to correlate temperature changes with geophysical events, if possible, and to compare seafloor temperature changes to changes observed in the water column by annual ship surveys and in situ temperature recording moorings to assess the impact of hydrothermal fluxes from the Axial Volcano.
• Using ROPOS, engineers freed from the new lava the Volcanic Systems Monitor that that had been embedded in lava following the January 1998 eruption.
• For the first time, images and data from a remote seafloor-mounted camera and array of temperature sensors were transmitted in near-realtime via acoustic telemetry and satellite to the laboratory.
• 1999 marked the second year (and third cruise) of monitoring hydrothermal changes resulting from the 1998 eruption on Axial Volcano. A series of CTD tows and casts found that the inventory of hydrothermal heat and particulate matter in the water column over Axial continued to decline. The decrease of both species can be modeled as a power law, with the rate of decline similar to that observed at CoAxial following the 1993 eruption.
• Between the 1998 and 1999 field seasons, Vents scientists improved on the prototype hydrothermal fluid and particle sampler (HFPS) and then used it to collect 120 samples during 5 ROPOS dives at Axial Volcano. A major emphasis of the NeMO project is the investigation of the sub-seafloor microbial biotope, and the HFPS is the primary tool to recover samples. 1999 was our second year of studying the hydrothermal effects of the January 1998, volcanic eruption. The time series and spatial extent of our diffuse vent fluid sampling in the eruption area are unprecedented, and we are gaining new insight to the chemical and microbiological importance of low-temperature reaction particle samples was characterized and revealed very high diversity in both particle-attached and "free-living" microbes.
• The Cleft segment time series plume chemistry studies continued in 1999. Total CO₂ measurements were added to the suite of analytes, to provide background values for future eruptive events in this area.
• The Axial Volcano post eruption monitoring continued in 1999 as well. Significant decreases from 1998 were observed in CO₂, Fe, and Mn.
• The primary objective of the VENTS Suspended Matter Project is to provide a better understanding of the evolution of particulate hydrothermal chemical species, including S and Fe, near deep-sea vents. These chemical species provide the metabolic energy resources for hydrothermal particle-bound bacteria, and the resulting vent-related ecosystems. Towards this end, we are focussing on hydrothermal sources and sinks for particulate sulfur. We have developed a procedure for collection, preservation and analysis of particulate non-volatile and volatile sulfur by x-ray fluorescence spectrometry. Coupled with our SEM methods, these procedures help us to differentiate between biotic and abiotic forms of sulfur (Figure 1). We are working closely with the microbiologists at UW and WWU to identify particle-bound bacteria. Together with the micobiological results, we will elucidate the efficiency of the microbial systems with respect to the chemical species emanating from deep-sea vents.

• Autonomous hydrophones were deployed in the North Atlantic to monitor seismic activity in the mid-Atlantic Ridge. Another array of hydrophones was deployed in the North Pacific and Gulf of Alaska to aid in studying the behavior of marine mammals in that region.
• Thermistor and current measurements at Axial Volcano were used in a inverse calculation to infer active-vent locations that might have been overlooked by sea floor towed-instrument surveys. Results suggest, among other things, the likelihood of hydrothermal sources on the eastern flank of the volcano during 1998, but ones which ceased discharging by summer 1999.
• Numerical experiments of buoyant convection from line segment sources were undertaken for both laboratory and ocean scalings to examine the number of individual bolues into which rising event plumes might break. At ocean rotation rates and stratification, breakup is borderline. Results suggest an event plume source must be actively discharging along more than several kilometers of seafloor before even two plumes at the level of neutral buoyancy could be created.
• Publication of a paper in Earth Planetary Science Letters addressing the way in which event plumes, or megaplumes, are produced during magmatic events on mid-ocean ridges. This paper relied on the helium and heat content in these event plumes to place constraints on the mechanism of their formation.
• Completion of a major expedition exploring hydrothermal vent sites along the southern East Pacific Rise using the deep submersible Alvin.

Vents Program

Plans for FY 00

• Vents scientists remain ready to respond to volcanic events along the northeast Pacific seafloor spreading centers as determined by seismic monitoring utilizing the SOSUS array. Scientists will study the physical, thermal, and chemical characteristics of hydrothermal plumes resulting from the volcanic activity as well as hydrothermal fluids venting on the seafloor. A major goal of the event response is to survey and sample microorganisms which are now known to be venting from new eruption sites.
• The third annual expedition to the NeMO site will take place in July-August 2000 aboard the NOAA Ship Ronald H. Brown. Activities will include deployment of geophysical and hydrothermal instrument systems, sampling and mapping of geochemical, suspended matter, and water column properties, and continued geological mapping of the Axial eruption site. An enhanced monitoring capability will be deployed at Axial, providing continued sampling of the seafloor environment and near realtime delivery of collected data to the laboratory.
• Forces that drive steady and subtidal flows at ridge crest depth are incompletely understood. Measurements often show ridge crest currents have component periods of ~ five days, suggesting meteorological influence. One possible connection between surface and seafloor is through pressure. Numerical experiments will be used to study whether five-day pressure gradient signals might occur at the sea floor as the result of incomplete compensation of atmospheric loading by sea surface elevation.
• A cruise to collect additional bathymetric survey data of the Juan de Fuca Ridge will be accomplished in March.
• Analysis of samples and data collected during the Alvin dives along the southern East Pacific Rise will be undertaken. We will also continue to work on samples and data collected with ROPOS dives on the Juan de Fuca Ridge. A paper describing the distribution of hydrothermal venting in the pull-apart basins along the Blanco Transform system is also in preparation.
• As a part of the NeMO cruise activities in July-August 2000 15-30 temperature sensors will be deployed directly on the seafloor. These sensors will be used to monitor long term variations in the temperature of hydrothermal fluids, variations that may be related to future tectonic or volcanic activity.
• In FY 2000 the Vents Suspended Matter Project will determine the relationships between the magnitude of the hydrothermal emission signals at Axial Volcano and the regional distribution and temporal variability of particulate inside and beyond Axial Summit Caldera. Our research is designed to provide quantitative information on the effects of hydrothermal venting and microbial processes on the chemistry of the water column of the Pacific Ocean. We intend to deploy an in-situ particle sampling system to collect co-located plume samples of vent bacteria and the concentrations particulate Fe, Mn and S, and particulate trace metals within a hydrothermal plume. We envision short term-deployments near the vents for the periods of about 4-5 days to understand high-frequency variability, and also year-long deployments to obtain information on the longer time scales of variability. This research has an excellent potential for a strong Vents Chemistry collaboration with the microbiological efforts of our colleagues at UW, WWU and the University of Hawaii.
• In 2000, vent fluid chemistry results from the first two years of sampling at NeMO will be published. We are working on joint publications with U.W. microbiologist John Baross. We will continue the time series sampling work at Axial Volcano during ROPOS operations on the Ron Brown using the hydrothermal fluid and particle sampler (HFPS).
• The HFPS will also be used during an Alvin/Jason submersible research program to study the effects of tidal perturbations on hydrothermal systems on the Endeavour segment of the Juan de Fuca ridge.
• In FY 2000, work will be undertaken to initiate a volcanic response system based on the use of new technology which will allow moorings and other instrumentation to be deployed from commercial and or military aircraft. When fully implemented this program will allow an air response to submarine volcanic eruptions within 24 to 36 hours of their occurrence as opposed to our current 7-10 day response time using research ships.