Sheldrake River

Created: 2014-01-30 15:02:09
Modified: 2014-08-19 15:59:17

Since the change of our technician, we have checked all our equipment in the field and upgraded all our recording sites. This took a lot of time and travel. We also hired somebody to put our database in order. I was very unsastified with the quality of our data up to now. But now everything looks better.

In the case of Shedrake, previous data have been corrected and new data is added, to 1997 included. Until then our thermistor cable was recording at the following depths:

As glitches were appearing in the data from 1995 on, we decided in 1998 to put a new cable. It goes down to 3 m. For two years, we operated the site only with this cable, which is about 4 m away from the first one. As we thereafter realized that the first cable was repairable, we put this summer the two cables on a dataloger, with a multiplexer. Therefore, after the readings are done in summer 2002, we will be able to have continuous data of high quality from the beginning. And we will be increasing the depth of the recordings.

- Depth of active layer (i.e. 0 C isotherm):

1990: 1.21 m, on 8 December
1991: 1.34 m, on 12 December
1992: 1.08 m, on 22 December
1993: 1.31 m, on 30 November
1994: 1.34 m, on 1st January 1995
1995: ND: insufficient data
1996: 1.54 m, on 4 January 1997
1997: 1.57 m, on 31 december

The values are rounded to the nearest centimeter. They values are interpolated linearly on the thermal gradient between the reading at the level above 0 C and the reading at the level just below 0 C when the temperature reaches its warmest point at that level. In all years, the surface layers had started to freeze back at the time of maximum Zero isotherm penetration.

The thermal curves in the permafrost (1.4 m and 2.0 m) show clearly that the climate cooled somewhat from 1990 to 1992, 1992 being the coolest year in the series (the Pinatubo year). It warmed up then from 1996 to the present, with the exception of 1997 which was more an average year.