The flow of heat from the interior of the Earth through the sea floor is of fundamental importance because it relates to or reflects a wide variety of Earth System processes. In spite of its increasing importance related to methane seeps, hydrothermal flow, gas hydrates (a potential alternative energy source), and other applications, there has been a gradual decline of U.S. heat flow measurement capability. Currently, there is no heat flow system available to the US research community. This project will establish and maintain a U.S. heat flow capability at modest cost, using existing equipment under the umbrella of the coring facility at Oregon State University. The broader impacts are clear; the proposed heat flow facility will save the U.S. heat flow capability, thereby enabling essential research.
Marine heat flow observations provide critical constraints on physical, chemical and biological processes occurring near and below the seafloor. The primary goals of this collaborative project were to develop a capability for U.S. academic researchers to access technology (hardware, software, expertise) to run heat flow surveys from UNOLS vessels. This capability is being built around two sets of instruments: (1) a multipenetration probe that allows multiple measurements of heat flow, the product of the thermal gradient and thermal conductivity, with a single instrument transit to the seafloor, and (2) outrigger probes that can be mounted on gravity and piston cores to return thermal gradients, with thermal conductivity data provided by a needle probe system. The multipenetration system being adapted for this purpose was developed and maintained by E. Davis and colleagues at the Pacific Geoscience Center, Geological Survey of Canada. Transition of this system to the U.S. was overseen by lead co-PI R. Harris (OSU). The second part of the project focuses on preparation of the outrigger probe and needle probe systems and was overseen by co-PI A. Fisher (UC Santa Cruz). This capability is now operational and active. The capability provides access to an initial set of accurate, robust, and relatively simple instrumentation to address scientifically important problems. Many proposals have been written and funded to use the heat flow capability demonstrating an interest and need by the scientific community. This capability is also being used by the U.S. Geological Survey and has led to partnerships with industry. We have conducted at sea training in the theory and practice of making and interpreting heat flow measurements for post-docs and graduate students. Academic projects have included a thermal investigation of the Cascadia margin offshore Washington. This data is critical to understanding the thermal regime and fluid flow associated with this margin that plays a role in influencing seismic processes. Upcoming acadmic projects include a heat flow survey in the Panama Basin to better understand the evolution of oceanic crust and a heat flow survey across the Hikurangi margin, New Zealand, to investigate the thermal environment of slow-slip earthquakes observed there.
