资源环境科技发展态势分析平台

We use yearlong vertical temperature profile timeseries (7 thermistors at evenly spaced depth intervals from 10‐70 cm) from five sites in and around the Deep Hole thermal area, southeast of Stevenson Island, Yellowstone Lake, to investigate heat and mass fluxes across the lake floor. The records demonstrate that thermal gradients in surficial sediments are modulated by a rich spectrum of bottom water temperature variations generated by hydrodynamic processes, and that sites inside the thermal area also respond to hydrothermal variations. We develop and implement a new method for estimating the sediment effective thermal diffusivity and pore fluid vertical flow rate that exploits the full spectrum of observed temperature variations to generate the parameter estimates, uncertainties, and metrics to assess statistical signficance. Sediments at sites outside thermal areas have gradients of ∼7.5 °C/m, in‐situ thermal diffusivities of ∼1.6 x 10^‐7 m²/s consistent with highly porous (80‐90%) siliceous sediments, and experience hypolentic flow in the upper ∼20 cm. Sites inside the Deep Hole thermal area exhibit considerable spatial and temporal variabilty, with gradients of 1‐32 °C/m, and higher thermal diffusivities of ∼2‐12 x 10^‐7 m²/s, consistent with hydrothermal alteration of biogenic silica to clays, quartz, and pyrite. Upward pore fluid flow at these sites is observed across multiple depth intervals, with maximum values of ∼3 cm/day. The observed spatial and temporal variability within the thermal area is consistent with upward finger flow combined with short wavelength convection within the porous sediments above a steam reservoir.

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