Borehole Climatology: Continental Energy and Climate Change

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We are witnesses to increased research about the climate system stimulated by concerns about projections of a warmer Earth. However, ascertaining climate models' projections requires that they be validated with the climate of the past. Only by properly simulating paleoclimate, will a model inspire confidence in its projections. In this avenue, underground temperature data have contributed significantly to our understanding of the climate of the last millennium. Climate reconstructions from these data assume that surface air temperatures are coupled to ground surface temperatures, and the latter propagate to the subsurface by thermal diffusion superimposing on the background steady-state geothermal field. That is, if the temperature at the Earth's surface changes, then a quantity of heat will be gained (warming) or lost (cooling) by the ground; these changes in the energy balance at the surface propagate and are recorded underground as perturbations to the background thermal regime. Analysis of these underground anomalies provides the base of the geothermal method of paleoclimate reconstruction. Climate reconstructions from borehole climatology are unique; their inferences are a measure of long-term climate, independent from meteorological records. This area of research has been the focus of my work for the last few years because of the great potential to shed light on the understanding of climatic change in its natural state. Results from the research program I propose will allow a more complete understanding of the heat transfer regime at the atmosphere-ground interface. My long-term objectives are to characterize the heat transfer regime from the atmospheric boundary layer to the first few hundred meters of the Earth's crust. Such characterization would be very useful for incorporation into climate models to study the climate system; in particular, to understanding the evolution of permafrost. Thermal data from the subsurface are fundamental to understanding the energy balance at the Earth's surface and also provide long-term boundary conditions at the ground surface for climate models. Graduate students will work on adapting the latest version of the Community Land Model - CLM4, to extend its bottom boundary placement to allow the use underground temperatures to understand the changes in the ground surface energy balance and thus the energy partition at the air-ground interface at century and millennia time scales. We intent to perform a millennium-scale ensemble simulation of a global climate model with a fully coupled continental component. In order to use the continental heat storage as a measure of performance of land surface models, we will continue gathering additional geothermal data from underrepresented continental areas of the world; for example, Chile, Argentina and Brazil. I plan to continue involving PhD and MSc students throughout all aspects of this project.