Assessment of Soil Temperature with Depth Methodology Used for Global Climate Change Studies

Witter, Jason D. and Alison Spongberg
Earth, Environmental, and Ecological Sciences Department, University of Toledo, Toledo, OH

Long-term collection of soil temperature data spanning the latitudes is important in determining the effects of global warming. A relationship has been established in recent borehole research defining below ground temperatures as a record-holder for the warming of the planet. The GLOBE program, with 14,000 schools participating internationally, provides an excellent opportunity for climate and soil warming data acquisition. Assessment and refinement of current soil temperature field collection protocols endorsed by the program in order to increase the usability of the data collected is extremely important. Current protocol measures soil temperature at 5 and 10 cm depths in a daily or weekly sampling regime, confounded by diurnal soil temperature cycles. The silty/sandy soils of the Oak Openings Region, northwest Ohio (41°N, 83° W), provide an opportune locale to study this variation. Using the GLOBE protocol based methodology and automated data logging, the temperature gradient to depth of one meter (surface and 10 cm intervals) where quantified for 15 sites. Soil moisture, pH, particle size, and weather parameters were also collected. After one year data show that the diurnal variation ceases at around 40 cm depth, and as air temperature warms the surface lags of 1 to 2 days in August (highest temperatures and widest variability) and 4 to 6 days in January between 10 and 100 cm were observed. The diurnal variability is emphasized with the current protocol, and since the most valuable data to global climate researchers would be retrieved below this plane, describing these depths is very important.

AAPG Search and Discovery Article #90031©2004 AAPG Eastern Section Meeting, Columbus, Ohio, October 3-5, 2004