by CJ@RESPEC » 2009-09-27, 15:27
Very interesting! How is the temperature being measured (appears to be on an logger) and where? If the temperature was being measured in a location where it is being impacted by earth tides, you may be able to see subtle temperature ups and downs because fluid being forced "in" our "out" near the gauge could have different temps because of geothermal gradient. For example, I have observed in well bores (with temperature sensor is in casing) that increases in pressure can cause increases in pressure and conversely pressure drops cause temperature drops. This is because increasing pressure "pushes" warmer fluid past the gauge and when the pressure drops it "pulls" cooler fluid past the gauge. I wonder if a similar situation could occur in your example. However my gut reaction is that the swings you are observing are too large (0.1 degrees C). Assuming is deep enough to be in geothermal regime and know gradient, one could back calculate what difference in depth would be required to get this result and could rule out my explanation.
Cheers,
CJ