its value at the start of consumption, R/H = 0.70, to ensure that the well shape is
continuous at the transition from period 2 to period 3.
Figure A7 shows the resulting composite well shape. Use of R/H = 0.70 for pe-
riod 1 yields a bell-shaped cavity that is qualitatively consistent with the observed
shape. It predicts a radius of 10 m at the level of the freeze-back ice cover, consistent
with the observed value of 8 2 m. However, R/H = 0.70 probably overpredicts the
cavity size near its upper level. Thus, Figure A7 shows a conical wall shape that
should underpredict the prefire cavity size. Figure A7 also shows ellipsoidal pools
as they would have existed immediately before the 1994 fire and just following our
1995 collector deployments.
Ice volume and mass melted
We may use Figure A7 to estimate the volume and mass of ice melted that con-
tributed micrometeorites to the well. The prefire cavity volume ranges between
3,300 m3 and 4,400 m3 for the conical and R/H = 0.70 shapes, respectively. Using
the average value and applying a 20% uncertainty, we estimate the prefire ice vol-
ume melted as 3,900 800 m3. The period 3 analysis yields a cavity volume of 2,200
m3 with an ellipsoidal pool of 4,700 m3. Assuming 10% uncertainty, the period 3
ice volume melted is 6,900 700 m3. Combining these values yields a total volume
of ice melted as 11,000 1,000 m3. Accounting for the variation of density with depth,
we estimate the total ice mass melted as 8,100 900 tonnes.
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