Three-dimensional dense distributed temperature sensing for measuring layered thermohaline systems

Abstract

Distributed temperature sensing has proven a useful technique for geoscientists to obtain spatially distributed temperature data. When studies require high-resolution temperature data in three spatial dimensions, current practices to enhance the spatial resolution do not suffice. For example, double-diffusive phenomena induce sharp and small-scale temperature patterns in water bodies subject to thermohaline gradients. This article presents a novel approach for a 3-D dense distributed temperature sensing setup, the design of which can be customized to the required spatial resolution in each dimension. Temperature is measured along fiber-optic cables that can be arranged as needed. In this case, we built a dense cage of very thin (1.6 mm) cables to ensure that interference with flow patterns was minimal. Application in water bodies with double-diffusion-induced sharp temperature gradients shows that the setup is well able to capture small-scale temperature patterns and even detects small unsuspected seeps and potential salt-fingers. However, the potential effect of the setup on the flow patterns requires further study.