Field Update: Dec. 8, 2010

The team ran the DOCTOR (Downhole Optical Caliper Tool for Observing Roundness) down the hole melted in the ice at Site #2 to continue our observations through the ice shelf and to the seafloor below. This time Mike Williams suggested that they also deploy a CTD (conductivity, temperature and depth) sensor as part of the run, so they were both sent down together.

The camera and the lighting were both focused downward on this trip, with the camera attached above the lighting and the CTD attached below the lighting. You can see the porous nature of the snow layers in the upper part of the hole and how they progressively compact and squeeze together to become ice as we travel down through the firn layer and into the water at about 41 meters below the surface of the ice (mean sea level). You can see the first pilot hole we made (to set the pump in the water) before melting the main hole through the ice shelf – the holes are separated by a thin ice layer.

There’s another 210 meters of ice shelf below the water line to the base of the ice shelf. The ocean that fills the ice shelf cavity extends southward to the grounding line of the West Antarctic Ice Sheet (WAIS), which is located about 700-800 km south of Coulman High.

The two holes merge as we continue downward towards the water line.

Then the camera goes into the water and continues to descend.

The camera helps us to understand the ice we are melting through, which has inclusions of sediment, rock and other debris.

We can see the ice re-freezing in the middle of the ice shelf as the walls become covered in ice crystals. Then we are exiting the ice shelf and entering the dark water of the abyss below. We can see the marks where the cables have melted into the ice walls as they’ve gone in and out of the hole. It’s another world down below the ice – one we’ve only glimpsed and have barely explored – this is truly pioneering work, and lots of fun!!

Bob, Ethan and I will fly out to the Coulman High camp tomorrow from McMurdo. Dick and Will are already on their way back to Woods Hole and are monitoring the data coming from the oceanographic mooring that was deployed through this hole melted in the Ross Ice Shelf. It’s strange to think of the cable hanging down through the ice with the instruments attached to it in the water column and then think of the ice slowly refreezing and closing the hole in the ice around the cable. We’ll come back in another few weeks to re-melt the hole around the cable and pick up this mooring (and the other one at Site #1). No one has done this before, which is both exciting and a little daunting – what if we fail? But for now, the real-time data is streaming up the hole and across the world to show up on a website at WHOI. Maybe someday this site will become part of a Southern Ocean Observing System that can be used to monitor changes happening under the ice shelf in real time. Until then, we’ll keep deploying instruments and collecting data.

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