A Wis-Spot Update
Written by Betty Trummel
The WISSARD test site (WisSpot as it’s referred to by many) was a busy place again today. Scientists worked until late last night, using the 24 hours of daylight to their advantage. They took time to test a few more instruments.
One of those instruments was Reed’s (NIU) multi-corer. Compared to the huge instrument tested yesterday (the POP, also NIU), the multi-corer is quite small. It weighs about 180 pounds total. This specially designed tool was made in Austria, and has a very compact structure. It has three tubes for simultaneously collecting three sediment cores.
Reed showed us how the multi-corer worked, and also explained the design a bit further. This tool is made to capture sediment samples from what’s called the “sea floor interface,” or in the case of Lake Whillans “lake floor interface.” The interface is where the water in the sea or lake meets the sediment on the bottom of that sea or lake.
Diatoms on the sea or lake floor are of interest to Reed for his scientific studies. He looks for evidence of diatoms (microscopic plants) in this environment. Diatoms live in the surface waters where there is sunlight. Because they are plants, they need sunlight to make their own food (photosynthesis).
When they die, they sink to the bottom. Some diatoms may be carried by currents under the ice shelf. Each sediment core tube can hold a wealth of scientific information for Reed to analyze. The photo below shows the tubes that are inserted into the multi-corer. Each tube is less than a meter in length and has a yellow cap on the top end. The diatoms in these cores provide a record of change in the ice sheet. The diatoms recovered from beneath the ice represent previous times of warmer climate.
The multi-corer also has stainless steel fins that are attached as part of the overall design. These fins make the tool stable as it goes through the borehole. They add some extra weight to the instrument and help guide it through the hole in the ice. Reed compared these fins to ice skates, sliding along the inside wall of the hole, protecting the instrument from knocking against the wall of the borehole. What a clever design!
You can see the fins in the photo below.
The multi-corer is deployed using a smaller, light winch. The weight of the instrument sends it to the sea floor (or lake bottom) and it is pushed into the softer sediments to collect three samples.
This short video below shows one little step of how the sediment is captured after being collected in the tube. The tension is released on the rubber tubing and the little white/black ball snaps down to the bottom of the tub and creates a seal to trap the sediment sample. Later, the black section is left in the bottom of the tube to keep it sealed and the white part is reused for the next round of sampling.
Insert VIDEO HERE!
The light winch that deploys this multi-corer, is also used to deploy other light instruments here at the test site. Only the larger winch, with a much thicker, heavier cable, is used for huge instruments such as the POP and percussion corer. Here is the light winch when it was first unpacked here at the test site. It is mounted on a sled that can be pulled by one person.
The light winch was designed by Robin Bolsey. He worked at Cal Tech University when the winch was first developed in the 1990’s. Robin is a designer, technical assistant and has a strong engineering background. He has seen this machine evolve over time and it’s been very useful in driving various tools and instruments into boreholes for many years.
In the next two photos Robin is helping the grad students put parts of the winch together that will help them rewind the cable onto another spool.
Alex, (a grad student from Montana State), is rewinding the cable onto the alternate spool, making this machine ready to deploy our instruments down the borehole. The light winch can safely handle loads up to 600-700 pounds. Anything heavier than that is deployed with the larger winch.
Alex has to be sure that the cable is rewound and fed onto the new spool in an organized fashion. That way when it’s used with an instrument it will not be tangled or stuck.
Here is the winch, mounted on the drilling deck ready to go.
As we deploy our instruments into the borehole, we’ll be using both winches, depending on the weight of the tool being deployed.
Robin’s winch has a mechanical disk brake, and it’s pulling load is highly variable, with the capability of using four different motors from ¾ horsepower to 2 horsepower. It can trade pulling power for speed if the situation warrants it.
Robin says it’s like an Erector set or Legos because it has lots of mix and match pieces. I think all of you back home should get out those Lego and Erector sets and get building! Someday maybe you can design and build a cool tool like Robin’s winch.