Abstract:
Time series records of horizontal current velocity, temperature, light attenuation
and settling particle flux obtained using moored instruments above Endeavour Ridge in
the northeast Pacific Ocean elucidate the dynamics of a deep-sea, neutrally buoyant,
hydrothermal plume. Data collected in four mooring deployments over three years
within 20 km of an active hydrothermal vent field quantify heretofore suspected
temporal and spatial variability in the plume, and provide evidence of causality. Over
time scales of hours to days, local fluctuations in temperature and suspended particle
concentration primarily reflect horizontal transport of hydrothermal effluent by currents.
However, it is dramatic variability in lateral transport of hydrothermal material over
longer time scales (months to years) which profoundly influences the spatial
distribution of settling particle flux. Steering of the hydrothermal plume by horizontal
currents, in concert with seasonal effects linked to production of biogenic particulate
material in the upper ocean, together explain the predominant temporal patterns in
settling hydrothermal particle flux measured within and beneath the plume. Spatial
variability in plume-guiding currents is also pronounced; horizontal flow is nonuniform
over distances of ~ 10 km horizontally and hundreds of meters vertically.
