Abstract
Currently, we lack a systematic and remote method for locating and quantifying diffuse seafloor venting using underwater robotic vehicles. Diffuse flow is characterized by both low temperature and low flux rates, which cannot readily be distinguished using current remote visual, acoustic, or vehicle‐mounted environmental sensors. The result is a poor understanding of the distribution, contribution, and context of diffuse flow sources. An underwater structured light imaging system, also used for high‐resolution seafloor bathymetric mapping, has however shown promise in detecting diffuse flows while completing seafloor imaging surveys at a typical altitude of 3 m. The system creates sequential bathymetric profiles by imaging a laser line projected on the seafloor. In the presence of venting fluids, the laser line exhibits a detectable level of distortion due to variations in the refractive index along the optical path. By characterizing the degree of distortion, it is possible to create maps indicating areas of potential venting with sub‐meter spatial resolution. Results from three distinct vent fields are presented and discussed. Analysis of these data sets indicates this system is capable of detecting both small point source vents and near bottom diffuse flow.
Highlights
Fundamental questions exist regarding the role of diffuse fluid flow in the thermal and chemical exchange budgets of hydrothermal systems and cold seeps
The goal of this paper is to introduce the structured light laser system as a sensor suite capable of systematic, remote detection of diffuse seafloor venting and small point source vents
The vehicle-mounted structured light laser system, originally developed for sub-centimeter bathymetric mapping, shows a sensitivity to index of refraction anomalies associated with active venting fluids during remote surveying and has potential for better assessing this type of flow
Summary
Fundamental questions exist regarding the role of diffuse fluid flow in the thermal and chemical exchange budgets of hydrothermal systems and cold seeps. Due to the elusive nature of diffuse flow it cannot be systematically and remotely detected using current vehicle-mounted tools. While locations of larger point source vents can be determined through the use of acoustic and environmental sensors, understanding the spatial distribution of active diffuse sources within a vent field is elusive. The vehicle-mounted structured light laser system, originally developed for sub-centimeter bathymetric mapping, shows a sensitivity to index of refraction anomalies associated with active venting fluids during remote surveying and has potential for better assessing this type of flow. This paper will discuss detection of diffuse seafloor venting using the structured light laser system beginning with an outline of the geologic value (Section 1.1.1) and an overview of the structured light system (Section 1.1.2).
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