ANALYSIS OF AIR TEMPERATURES ELECTRONICALLY RECORDED AT SIX WEATHER STATIONS ON THE JUNEAU ICEFIELD FROM 1986 TO 2010
This project started in 1986 to obtain year-round air temperature data in Stevenson shelters at six permanent field camps on the Juneau Icefield. The objective was to supplement the air temperature readings taken manually, starting in 1946. This project marked the first time solid-state data loggers were used on the Juneau Icefield
METHODS:
The first recorders used were manufactured by Ryan Instruments, Inc., Kirkland, WA. The Ryan TempMentors (RTM) were programmed to take a temperature reading every 2 hours for up to one year. Three TempMentors have been replaced by Pocket Loggers from Pace Scientific, Charlotte, NC, which are capable of taking hourly readings for more than 2 years. Annually, the Stevenson shelters were checked for damage and repaired as required, data was downloaded to a laptop PC, batteries were changed and the thermistor probes were re-calibrated in an ice-water bath. Data were entered into a Daily database generated by L’Softworks, Kalispell, MT which stores daily maximum and minimum temperatures. Complied data were analyzed with R, R Development Core Team, Vienna, Austria.
PRELIMINARY RESULTS:
Although there appear to be upward or downward trends for several of the camps, regression analysis showed no significant value for the slopes (p > 0.05). Analysis shows correlation between the various camps in their yearly variation in mean value for each year. Histograms for each of the camps show a consistent bimodal character. This phenomenon previously documented in literature is attributed to maritime and continental weather systems which alternately control weather on the Juneau Icefield.
SUMMARY:
Careful design and dedicated maintenance make possible, long term data from low cost instruments located in remote glacier environments. Follow-on work will emphasize the relationships between camp temperatures by seeking to predict temperatures at one camp from the temperatures at several others. Improved recording systems will facilitate adding additional weather stations to the current network. Enhanced tracking of storm systems (frequency and location) may provide insight to explain the significant loss of glacier mass on the Juneau Icefield (documented by GPS and mass balance measurements) despite relatively constant air temperatures over the years as reported here.