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> August 1, 2006 - Using the Seacat, Collecting Water Chemistry Data
Maggie_Kane
post Aug 2 2006, 09:31 AM
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Today I got to work in the boat with Mike, Ben and Bennet. This was really fun for me because I didn’t know much about the projects on the lake yet, or the equipment that will be used. The lake is a really important area of study as it literally collects a lot of the sediment that comes out of the glacier and river and holds it in layers at its bottom. If we can look at a core of it taken up in a tube, we can “read” the sediment transport and climate like rings in a tree. Caroline will be collecting some cores from the little perched lake, Kongress, as soon as conditions are good. It is really tricky to core the bottom of a deep lake, because the boat never stays still for long.

Some of the Coring Tools
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Bennet will be doing the coring in Linnevatnet in the next two weeks, but today we were gathering information on the water chemistry. We are collecting data from the same places in the lake every time (and for the past 3 years), but don’t have buoys above the water to mark the spots. There are buoys below the surface so that the ice cover in the winter won’t attach to them and move them along their anchored bottom, but these are hard to find. We use a GPS unit to locate the coordinates over and over again. Have you ever used a GPS unit? This stands for Global Positioning System and they are pretty neat tools.

Leif Learning the GPS Unit with Mike
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To study the water chemistry we use a really cool device called a Seabird Seacat CTD. This collects water as it is lowered and records the depth and water temperature every 2 seconds. Along with this, the Seacat measures conductivity (fee ions in the water, like salt), dissolved oxygen, and light transmission for turbidity (relates to the amount of sediment swirling around in the water). The instrument is lowered carefully to the lake bottom, and then pulled back up. When we get back on dry land it is connected directly to a computer and the data is downloaded. We use a special field computer that is considered water resistant. You can see it in use in several of these pictures.

Deploying the Seacat
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We also collected data from some flow meters that Bennet and Ben set up a few days ago. These are attached to a little red boat that they anchored to the lake bottom. The flow meters are designed to collect the speed that the lake water is moving as it emerges from the river and enters the lake. They are attached to a “brain” that collects this data and then can be downloaded onto the computer. The hardest part of this is getting from our boat into the little boat – it is very small and always a difficult dive!

Bennet in Little Red Boat
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Not a bad office, eh? Doesn’t Bennet look like all he needs is a latté?!

Our third task today was to climb up onto the basalt sill (a long ledge) where Ben placed the automatic camera. This is one of the instruments that uses one of the really heavy batteries and a solar panel. Together, they will power the camera to take pictures every 3 hours during our field season, and continue to take daily pictures throughout the winter months.

Ben with Camera on top of the Sill
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The camera is positioned looking toward the lake inlet, where the river water (and any sediment it is carrying) enters the lake water. We noticed a clear plume of tan colored sediment fanning out into the blue-greenish lake, taking different shapes each day. We think that the shape has something to do with wind direction buffeting the top layer of water one way while the underflow moves another. We can start to coordinate our plume observations with our weather station data (wind speed and wind direction) once we know more.

Me Sitting Down on the Job! (see the glacier, river and lake in the background?)

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We have learned from the high volume of sediment from some of our evening ISCO river samples that the peak of the sediment load is in the middle of the night. This sediment pulse migrates downstream with the water and arrives at the lake sometime in the early morning hours. Once we pull and download the level loggers (remember the tube cigar shaped instruments we placed in the river to help us “see” water depth?) it will help pinpoint this timing. Ben has set up the camera to capture images of this sediment plume in varying weather conditions throughout the day.

Question of the day: Why would we see the highest quantity of sediment entering the lake in the middle of the night?

A few things that might help you answer:
• The distance from the glacier to the lake is approximately 10 k
• The sun is up all the time, but circles around at what feels like a 2:00 in the afternoon position.
• The valley points toward the north where it eventually meets the Arctic Ocean.
• The valley has relatively high walls on the east and west sides.

I really want to hear your ideas on this! Please post within the “Ask the Scientist or Teacher” forum where you might otherwise pick “Teacher Journals”. The entry with the best answer gets a prize!



Answer from my last question: the huge whale skull shown two days ago in my journal is from a Bowhead whale (Baleine boreale). There are very few if any of these marvelous creatures left in this area. According to “Birds and Mammals of Svalbard” by Fridtjof Mehlum, “Today the bowhead whale is regarded as having been eradicated from Svalbard waters, but was previously very numerous in the fiords and along the coast of Spitsbergen. Large quantities of enormous bones can still be seen along the shores of Svalbard, a witness to the hunting of previous times”.
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