We once again focused our studies on the Mt Troy and Showboat areas today. Our fieldwork requires a great deal of time to examine, test, and record the data, and this area is among the few places sheltered enough from the NE wind so we can do our work during cold spells. The area also has some of the weaker layers, ones that we want to track changes in over time.

The winds were gusting to NE 25 m/sec on the mainland ridges this morning, transporting snow to lee slopes. But the wind was hitting only the tops of Mts Troy and Stewart on Douglas Island today. We found near-calm field conditions. It was our coldest field day so far this season, and the rapid change from mild to cold weather produced the strongest temperature gradients we have found this winter.

The top layer of the Dec 23 to 24 faceted melt freeze at 105 to 115 cm was again the principal weak layer in our block tests today. It has become very sugary but is overlain by a hard melt freeze crust that is runneled and has refrozen percolation structures beneath the runnels that bond it solidly to the harder layers beneath in many locations, so it has high spatial variability. Our AK Block and Rutschblock tests had identical results today, though, requiring multiple hard jumps (#6) for Quality 3 (irregular shear) release on 40°.

Slope tests were more revealing. We triggered fast sluffs in the 10 cm of new snow on slopes of 40° or more, releasing easily in the buried surface hoar beneath it. Some of the sluffs were slabby, with boundaries and bed surfaces partially present, and a couple were clearly small slabs. In most locations tested, the new snow was not affected by wind and is rapidly becoming faceted. The faceted new snow had little cohesion to propagate fracture with, but the new snow showed sensitivity wherever it was even slightly wind affected.

In the most wind exposed locations, the NE winds last week swept everything down to the hard December 23 to 24 thaw crust. Those areas now have 10 cm of new snow over the crust, a reasonable bond except wherever there is surface hoar on the crust. Other areas had small windslabs that may still be sensitive, and any fresh windslabs will be very easily triggered.

We were intrigued to observe facets forming in the thawed 380 Kg/m3 melt freeze we exposed to today's cold air near the bottom of the pit. We calculated that the 1mm thick layer that was freezing in the first few minutes was experiencing a 25° temperature difference, a gradient of 250°/cm (2500°/m), far in excess of the 0.1°/cm (10°/m) threshold required for facet growth to be the dominant process, even without factoring in the heat released by the phase change from liquid to solid. No wonder the grains were growing facets!

The faceted melt freeze layers all displayed crisp fresh well-formed facets today, unlike the slightly rounded facets observed during the flatter temperature gradients this weekend.