Reconstruction of the 500 year ground surface temperature history of northern Awaji Island, southwest Japan
Abstract
Changes in ground surface temperature (GST) propagate underground and are recorded as a thermal perturbation to the background thermal field. If the thermal propagation of GST change is conduction only, subsurface temperature profile of a depth of several hundred meters potentially contains information of GST change of past several hundred years. By extracting information about GST history from subsurface temperature profiles, we can reconstruct GST history. This study presents a forward model of conductive propagation of GST in a layered material model with uniform thermal properties in each layer and a series of step functions as GST history. This model is expressed as the same mathematical form of that for a uniform thermal property model with a series of step functions as GST history. Subsurface temperature perturbation is calculated by superimposing solutions that solve problem of a layered thermal property model, surface boundary condition of a unit function, and bottom boundary condition of zero-temperature. Using this model, we reconstruct the recent 500-year GST history from temperature data obtained in a borehole in northern Awaji Island, southwest Japan. The reconstructed GST history shows relatively low temperature before the mid-18th century and the onset of recent warming in the mid-18th century to the early 19th century. The GST increased by about 1.2 K until the mid-20th century and decreased by about 0.2 K from the mid- to late 20th century. The GST change in the 20th century fits the trend of mean annual surface air temperature records in Kobe, opposite the coast of northern Awaji Island. The increase in GST resulted in an increase in subsurface heat content. The GST history in northern Awaji Island is different from that in Ulsan in southeastern Republic of Korea located at the same latitude as Awaji Island. Differences of the GST histories of these regions most likely reflect differences in sea surface temperature in these regions.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFMGC51H0820G
- Keywords:
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- 0520 COMPUTATIONAL GEOPHYSICS / Data analysis: algorithms and implementation;
- 1637 GLOBAL CHANGE / Regional climate change