Our program will explore the interactive physical-chemical processes at play in gradient driven submarine environments by focusing on three key questions within a hydrothermal system on the Endeavour Segment of the Juan de Fuca Ridge. These questions include: 1) What are the physical and chemical consequences of phase separation in black smokers; 2) What is the origin of low-temperature diffusely venting fluids that are associated with high-temperature fields, but which also occur far-field, and 3) How can tidal perturbations be used to explore subsurface chemical and microbiological processes within a single hydrothermal field. Investigation of these questions is important in that phase separation (e.g. boiling), diffuse venting, and tidal forcing operate in many, if not all, ridge crest hydrothermal environments; all of these processes are accessible for direct study in the four hydrothermal fields on the Endeavour. Using a range of in situ physical and chemical sensors and a new strategy for sustained fluid sampling, we will document the effects of tidal perturbations in fluid temperature, pressure, composition, and flow rate in areas of both high- and low-temperature flow. Our goal is to develop a series of interdisciplinary models linking the processes that produce these changes. In addition, observed tidal effects will provide insights into the responses of the entire system to identifiable perturbations and may allow us to develop models of subseafloor flow patterns and permeability structure.
