Saturday, May 15, 2010

This May we had what turned into the most interesting call of the year by far. At around 0930 Fleet Ops was working the ice with a bulldozer on the McMurdo Ice Road Transition. A little geography: McMurdo is on a little 10-mile longish spit that sticks out to the south from an island built of three massive volcanos. The permanent ice of the Ross Ice Shelf is hundreds of feet thick and stretches for hundreds of miles south of us. Gravity and ice fed in by glacial flows push the ice north towards the open sea at the rate of 5-10'/day. McMurdo's site was chosen by early explorers because it was the furthest point south on the continent with open water in summer. (although in modern times, for poorly understood reasons that may have to do with massive icebergs, temperature gradients between pole and lower latitudes, and current changes, the harbor doesn't open up naturally anymore). The Ross ice shelf also provided a convenient, relatively flat route deep into the continent towards the Pole. The thick permanent ice meets the thinner (12-20') seasonal ice at McMurdo. I've heard the edge of the permanent ice described as a towering blue wall elsewhere, but at McMurdo the two ice types just seem to flow together relatively seamlessly.
The ice shelf crunches into Ross Island on the Scott Base side of our little spit. On that side it buckles up into pressure ridges. These can be 10-20' high depending on the season. The summer road to Pegasus Airfield loops out around these ridges and runs along the permanent ice. On the McMurdo side of the spit, there seems to be sort of an eddy that creates a jumbled mess of cracked, broken, upheaved ice in front of town. The shorter spring road to Pegasus runs right through this and out over thinner ice. This spot has to be groomed and smoothed in preparation for summer use.
So Fleet Ops was out there with a dozer around 0930 Tuesday morning and they dropped one track into a big tidal crack. The rig was at about a 45degree angle with one track in the water and one in the air, so they had to call in a second machine to pull it out. As chance would have it, one of our firefighters was out on the road at that moment and he took pictures. The first pullout attempt was unsucessful when a cable broke and the dozer settled back into place.
At around 1030 the EOC (Emergency Operations Committee- station lead, NSF lead, fire captain, and other leaders) was activated. They went to their planning room in MacOps and took charge of the incident. Fleet Ops attempted a second pull-out but broke another cable. This time the dozer settled in much deeper and was now at a 65 degree angle with the track fully submerged.
By dinnertime ice profiling had been done and showed that the ice in the area ranged from 3-6'. 3' around the dozer. The decision was made to put someone in the dozer and attempt another extrication rather than leave it there to freeze in place until summer or later. Three tractors were hooked to the dozer with snatch blocks and pulled on it from solid ice. Another rig pushed against the blade of the trapped dozer.
The fire department and SAR were asked to standby to provide icewater rescue if necessary. Unfortunately neither the AFD or SAR are trained or equipped for ice rescue. This is odd since vehicles constantly travel on ice roads here, the station is surrounded by areas with open cracks, and major ship offload activities take place once a year in icewater. We ended up scrounging a couple drysuits left in the closed-up dive shack. Two of us that have had ice rescue training squeezed into those. I drew the short straw and ended up in some insulated foul-weather gear topped off with a harness. The crew put together an incredibly weird rope system and we stood by with fingers crossed. Fortunately the final pull got the tractor our sucessfully, and nobody got (too) wet.

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