Climate Inferences from Geothermal Measurements in South America

Abstract:

Analysis of borehole temperature data have contributed significantly to estimating the last millennium surface temperature changes. Additionally, recent analysis have contributed to evaluate the Earth’s energy balance by providing a quantitative value for the energy absorbed by the continents in the later part of the 20th century. Knowledge of the surface energy flux is important for understanding the solid Earth – atmosphere boundary condition, land cover changes, and their impact on regional and global climate models.

We present data and analysis of 19 borehole temperature versus depth profiles from South America. The dataset includes 10 new borehole logs measured during 2012 at three sites in northern Chile (Vallenar, Sierra Gorda and Sierra Limon Verde). These new measurements complement six temperature logs measured during 1994 in the same region (sites near Michilla and Sierra Limon Verde; Springer et al., Tectonophysics, 1998) and four logs obtained from the NOAA Paleoclimatology Borehole Database located in Villa Staff, Toquepala and Talara in Peru.

These data were analyzed for climate variability signals of the surface temperature and changes in the Earth’s surface energy balance. The analysis suggests a cooling trend during the 19^th century of approximately -0.5ºK. Furthermore, results show regionalized temperature changes in ground surface temperatures during the last 50 years with estimates of -0.4ºK in Vallenar, and approximately +1ºK in the Atacama Desert of Northern Chile. We place the results within the context of surface air temperature yearly means obtained from existing meteorological and proxy paleoclimatic data between Peru and Northern Chile. The use of geothermal measurements for climate variability studies provides a further understanding of the climatic and energy cycles of the Southern Hemisphere, where meteorological data can be scarce to non-existent.