Friday, January 18, 2013
Forrest McCarthy was a mountaineer on our PIG expedition. Mountaineer is a strange term, since it is about as flat as it gets there. But he, together with Einar Steinarsson, was responsible for safe conduct in the heavily crevassed areas. He put together this nice video of field impressions
Thursday, January 17, 2013
The Pine Island Glacier flows into the ocean. It loses mass by melting of ice by warm ocean water from underneath and by calving big ice bergs. Calving happens every few years, when a big ice berg is released into the ocean. The satellite image below (collected by TerraSAR X) shows a crack where the next ice berg is about to be released. This radar picture was taken in early January. Not only does it show the crack, but the linear feature at the lower right shows the snow machine traverse track between our different field camps!
Our field site was only 20 km away from the crack, so we got to fly over and have a look.
|Snow drifting into the crack|
|The crack in early December. It is almost entirely connected across the shelf|
|Airplane shadow in the crack|
Wednesday, January 16, 2013
Dale Pomraning (here with Penn State grad student Kiya Rivermann) is our hot-water drill extraordinaire. When we came back to the main camp at PIG, the camp manager, Dean Einarsson introduced us as: “Dale Pomraning and Martin Truffer, master driller and PI”. The way he said it seemed to refer to me as master driller, so Dale's feelings were hurt. Dean corrected this the next day with an official apology, which went along the following lines:
“Dale invented drilling in 1801. Before that people were mostly just digging in the sand with their bare hands. Since then he has been involved in many projects. Some of you might be familiar with Old Faithful? Since 1973, he has continuously drilled in Antarctica. He is the master driller for the PIG project. Martin does not know anything about drilling and mostly just stands around.”
Dale accepted the apology.
Tuesday, January 15, 2013
The PIG is the Pine Island Glacier in Antarctica. It is a huge glacier that drains into the ocean. The last part of it actually floats on the ocean and is melted from below by relatively warm ocean water. It is this melting that makes PIG such an important contributor to sea level rise from ice loss.
We spent most of December and parts of January drilling several holes through about 500 m of ice and then putting instruments into the ocean below. The instruments measure temperature and salinity of the ocean water underneath and the rate of melt at the bottom of the ice sheet.
It is a great relief to successfully complete this season after last year was essentially a total bust. We had fantastic support from NSF and the logistics people, which made this possible.
Our camp was put in with a Twin Otter on loan from the British Antarctic Survey. The Twin Otter is the workhorse of Antarctica. Once on the ground we moved all our equipment and camp with snow machines.
The camp consisted of two larger tents, one a kitchen, and one a galley for up to 14 people. We slept in the smaller mountaineering tents.
The hot water drilling operation works by pumping water out of a pool, heating it up to about 70 deg Celsius and pumping it down a hole. The water is then recovered and pumped back into the pool.
The heaters are essentially the same that are used to produce high pressure hot water at car washes. The pump is in the back left and is configured to pump a constant 20 gal/minute at high pressure.
The hot water is routed into the borehole via a capstan winch. We drilled at a speed of between 65 and 95 meters per hour. The drilling speed decreases with depth, because the water at the drill tip gets colder as the hose descends into the borehole.
The orange hose behind the winch is used to pump water back out of the hole for recirculation.
Once the hole is finished a variety of science takes place. We used a borehole camera to image the hole, we dropped a sediment corer to the bottom of the ocean to find a record of past glacier advance and retreat, and then installed instruments to measure salinity, temperature, and water fluxes in the ocean below the shelf. In this picture Jim and Tim from the Naval Postgraduate School in Monterey lower a flux package instrument with a string of thermistors to measure ice temperatures in the bottom part of the ice shelf.
Hot water drilling offers great benefits, such as a warm hose for naps, hot water for showers, hot tubs, and laundry.