Table VII (Cont'd), 



Mecbanically manipulated surfaces 



13. Ski-doo track, compacted vegetation 



14. Weasel track, wet 



15. Cat track, wet soil, bare 



16. Road, gravel pad, wet 



Oil spills on dry ground 



17. Oil plot, ground-soaked 



18. Fertilized oil plot 



19. Oil plot, oil-soaked plants 



Representative albedo value (or total area 



Albedo 



21 

 15 

 13 

 11 



S2 

 20 

 17 



20 



Soil thaw and model validation 



Jerry Brown* 



Yoshisuke Nakano*t 

 Vaughn Rockney 

 Don Vietor 

 Richard McGaw 



USA CRREL 

 USA CRREL 

 USA CRREL 

 USA CRREL 

 USA CRREL 



Duwayne Anderson 

 Leander Stroscheint 

 Joseph Przybylat 

 Gregor Fellorst 



USA CRREL 



USA Natick Laboratories 



USA CRREL 



USA CRREL 



The seasonal thaw of arctic soils is a sensitive indicator of near-surface energy exchange and 

 seasonal climate. The structure and composition of the vegetative and litter layers significantly 

 modify the soil thermal regime, thaw, and plant growth responses. For example, the hypothesis has 

 been offered that accumulation in litter reduces soil thaw and soil temperatures to the degree that 

 nutrient availability may be limited. In terms of summer climate, soil thaw can be characterized in 

 terms of air temperature and precipitation. During dry cool summers thaw is at a minimum and 

 conversely during warm wet summers thaw is at a maximum. 



Soil thaw has been measured at site 8 since 1962. During this period, extremes in the secular 

 thaw pattern have probably been observed; 1968, the deepest thaw and 1964, the shallowest thaw. 

 The following values were averages of the same 200 points measured at site 8 since 1962: 1962 - 

 40 cm, 1963 - 38 cm. 1964 - 29 cm, 1965 - 37 cm, 1966 - 36 cm, 1968 - 41 cm, and 1970 - 36 cm. 

 The 1970 season produced about an average thaw at Barrow. 



The objectives of the current program were twofold: 



1. Determine the initial response or sensitivity of soil thaw to a variety of man-made and 

 natural perturbations. These studies were done in cooperation with the several biological and 

 pedologic projects. 



2. Validate a soil thaw-temperature model by measuring soil temperatures and actual thaw 

 under a range of surface and soil variables. 



In order to accomplish these objectives soil thaw was measured by probing on all plots at sites 



1 and 2 at 10-day intervals. Site 1 plots and adjacent sites covering the complete range in soil 

 variability were instrumented with stacks of thermocouples. Thermocouple spacings were at every 



2 cm in the upper 10 cm and 5- to 10-cm intervals below. Temperatures were automatically recorded 

 half-hourly on a paper punch tape data logger. Approximately 200 sensors were monitored through- 

 out the season. Temperatures were also recorded for other subprojects including leaf and canopy 

 temperatures. 



•Principal authors. 



tNot at Barrow during 1970. 



21 



