Boxes
We had some science excitement today. A shipping container with most of the scientific data collection instruments was shipped from Christchurch, New Zealand to McMurdo on yesterdays C17 flight. We opened it up today and started unloading the equipment – just as the weather took a major change from light winds to higher winds. The winds make working outside a lot harder because anything that’s not tied down will blow away. The condition levels went from three (good, do anything outdoors) to two (limit outdoor activity). The winds also closed down both the Sea Ice runway and Pegasus Field, the ice shelf runway. So yes, it was getting windy. [a side note – my roommate in the dorm is a mountaineer who has been trying to get out to his field site for three days now. Last night his team took off at 6:00 P.M. in an LC 130 to land on a glacier. They came back at 2:00 A.M. after circling over the glacier for two hours and being unable to land because of the wind. I didn’t hear him come in, but sometime after that I heard him and realized he was back.] Weather is a big deal here in the Antarctic.
The equipment that was unloaded will be used to check for water currents, measure water chemistry, and take samples of the sediments that are under the glacier. I’ll get some pictures of the equipment when we get more of it unloaded, but for now here’s what some of them do:
- Water current speed – this uses the Doppler effect to measure the speed of water flowing past it. If you remember the Doppler effect, we usually think of it as how sound changes if the source of the sound is moving toward or away from us. If you are standing on a sidewalk and a siren passes you, it sounds different as it gets closer, then changes again as it move away. This is because the sound waves get shorter (compress) as the sound moves toward you and the sound waves get longer (expand) as the sound moves away from you. Our instrument will send out a sound wave into the water. If that wave hits a particle in the water, the wave will be reflected back to the instrument. If the particle is moving away from the instrument, the wave will stretch out. If the particle is moving toward the instrument, the wave will compress. Either way, you can measure how much change there is and turn that into a speed measurement.
The doppler effect causes the sounds you hear when a siren passes by to change. As the sound approaches you, it's as if the wave is compressed. As the sound passes by you, it's as if the wave is expanded.
In this diagram, imagine that the cars are the particles in the water. By calculating how the wave length changes based on if the particle is moving toward you or away from you, you can determine the speed of the particle and the rate at which a current is moving.
Water Chemistry – There are many different water tests that will be done. Some will be measured in place or within the drill hole. Others will use a sample of water taken in the drill hole but then brought up to the surface for analysis in a lab.
Percussion Core – this tool will bring back a “core” of sediment from the bottom of the subglacial lake. A core is a round column of rock and soft sediments. To get the core, the team will use a strong piece of pipe that is five meters (about fifteen feet) long and hammer it into the sediments and rock at the bottom of the subglacial lake. After it is driven in, it will be pulled out and hopefully the pipe will be full of the rock that is at the bottom of the hole. The hammering is done by the tool itself, which can raise and drop a heavy weight at the top of the core pipe over and over until it has hammered the pipe into the ground. It’s a very simple process, but remember it’s happening at the bottom of a deep hole drilled in the ice and you can’t actually see it working. If you’ve ever seen a pile driver working at a construction site, the percussion corer works like that.
This is a drawing of the percussion coring device. It is about 20-25 feet long. The hammer moves up and down and pounds it down into the sediments.
Computers and Data Collection
Many students record the data they collect when doing labs in school by hand. In the WISSARD project, almost all of the data will be collected by computers that are attached to the instrument. One of the team members of the WISSARD project is a computer programmer. His job is to make sure that we can capture the data that the instruments like the Doppler water current speed instrument send us. Here John is debugging his data collection code to make sure it’s working. His computer is plugged into the tool using the wires that you see going between the laptop and the water current speed tool.
The data tool is in the box. The computer has been set up to test the data collection from the tool into the computer.
No, this isn't the normal way to connect the data collection tool to the computer, but when you are in the lab and testing things, it works OK.
Blowing Snow
Today we had our first day of Condition 2 weather (Con 2 as they say here). It wasn’t everywhere, but it did cause some reduction in activities due to limited visibility. I was out at Spotsa (the name that has been given to our current WISSARD setup location), working in one of the containers when there was a noise like a truck driving over the crunchy snow. It lasted for a long time and I finally looked out the door and saw that the wind had really picked up and there was a lot of snow blowing along the ground. The clouds had also increased over the mountains to the south. There was a definite change in the weather. I shot a short bit of video to show you what it looks like.
http://youtu.be/7rWSNWDeWOw