Measuring fluid flow and heat output in seafloor hydrothermal environments

Autor: J. E. Smith, Robert P. Lowell, Robert Samuel Hurt, Leonid N. Germanovich, Gence Genc
Rok vydání: 2015
Předmět:
Zdroj: Journal of Geophysical Research: Solid Earth. 120:8031-8055
ISSN: 2169-9356
2169-9313
DOI: 10.1002/2015jb012245
Popis: We have designed, built, calibrated, and tested new anemometer and turbine flow meter devices to measure fluid velocity at high- and low-temperature focused and diffuse discharge sites at oceanic spreading centers. The devices perform at ocean floor depths and black smoker temperatures, and can be used to measure flow rates ranging over two orders of magnitude. Flow velocity is determined from the rotation rate of the rotor blades or paddle assembly. These devices have an open bearing design that eliminates clogging by particles or chemical precipitates as the fluid passes by the rotors. The devices are compact and lightweight enough for deployment from either an occupied or remotely operated submersible. The measured flow rates can be used in conjunction with vent temperature or geochemical measurements to obtain heat outputs or geochemical fluxes from both vent chimneys and diffuse flow regions. The devices have been tested on 30 Alvin dives on the Juan de Fuca Ridge and 3 Jason dives on the East Pacific Rise (EPR). We report 102 new measurements over a wide range of discharge temperatures (5° – 363°C), velocities (2 – 199 cm/s), and depths (1517 – 2511 m). These include the first advective heat output measurements at the High Rise vent field and the first direct fluid flow measurement at Middle Valley. Our data suggest that black smoker heat output at the Main Endeavor vent field may have declined since 1994 and that after the 2005–2006 eruption, the high=temperature advective flow at the EPR 9°50′N field may have become more channelized, predominately discharging through the Bio 9 structure. We also report first direct advective measurements in the Lau Basin and at the EPR 9°39.5′N with flow meters that predated devices described in this work and were used in the process of their development. We discuss potential error sources and how they may affect the accuracy of measurements by our and other devices. In particular, we use the turbulent plume theory to evaluate the effect of entrainment of ambient seawater.
Databáze: OpenAIRE
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