Date of Award
2007
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Geology
First Advisor
W.D. Gosnold Jr.
Abstract
The study of borehole paleoclimatology aids scientists in determining past climate changes and in understanding current climate trends. Accurate borehole temperature logs are necessary to obtain a useful temperature profile. However, as many climate workers have discovered, borehole temperature profiles can have many causes of inaccuracy. Uncertainties associated with borehole data include errors stemming from temperature measurement, depth measurement, thermophysical property measurements, and terrain effects. Terrain effects include topography, changes in land cover over time, direct and diffused sun radiation, and groundwater flow.
This study focused on specific terrain effects influencing borehole temperature profiles in the United States borehole dataset included in the International Heat Flow Commission global dataset. The objective is to determine severity of influence and the feasibility of correcting terrain effects on United States boreholes.
Large amounts of terrain-influenced boreholes included in the dataset will affect the reliability of using the entire dataset in climate modeling. Methods used to identify terrain effects include inverse modeling, comparison of observed borehole data with synthetic modeling created using meteorological station weather data, and remote sensing.
Research indicates approximately 34% of the 136 United States borehole profiles in the IHFC dataset have some degree of terrain effect. The severely influenced boreholes comprise approximately 15% of the United States dataset. The three main categories of terrain effects include topographical, water and land cover. Of the 63 boreholes included in this report, 21 exhibit land cover effect, 15 show topographical effects, 15 show minor effects, and 12 show water effects.
In addition, a study on the accuracy of grouped boreholes and the variation of borehole profiles in the regional area of North Dakota, South Dakota, and Nebraska was conducted. Numerous borehole profiles show variation within a given area. Averaging terrain-influenced borehole profiles with undisturbed profiles will affects results. The magnitude of effect is dependent on the type of modeling and intended use of the data.
Recommended Citation
Heinle, Shannon M., "Resolving Terrain Effects in Borehole Temperature Profiles" (2007). Theses and Dissertations. 132.
https://commons.und.edu/theses/132