Submitted by Anonymous on Sat, 08/08/2009 - 11:11
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Alaska Climate Variation 09

At what depth do you take the samples and what determines the depth that you take the samples??Get back safely=====Curtiss

Mon, 08/10/2009 - 08:57

Barney Peterson

Good morning Curtiss,  I am not sure whether or not my reply got to you as it is not appearing on this page so I will repeat.
Sampling starts at the surface and goes down: short cores are up to 55 cm or so and long cores (the goal) are hopefully more than a meter.  We use polycarbonate tubes tamped down into the lake bottom to get the short cores.  The long cores require a floating derrick contraption that allows us to raise and lower a heavier weight onto the top end of the polycarbonate or PVC tubes which are usually up to 3 meters long.  So far we have not gotten a core longer than 1 meter to come up without losing suction and starting to drop away out the open end of the tube.  This is a big challenge that we keep trying new things to overcome.  Since the water is sometimes up to 60 meters deep where we are coring we never know until we start pulling the rig up whether we have a full tube or not, sometimes the tube lets go of the sediments just as we get to the surface and before the tube is capped.  Then it is start all over again.  Tubes that are partially filled with muddy water and loose sediment material are of no use as our research depends upon keeping the layers intact.
I am safe, if wet, and doing well.
TCL
Barney Peterson