Field Update: Nov. 20, 2010

Gravity coring continued today, but with less success than previously. We are puzzling out what we can do differently after getting two runs with no sediment recovery. There is mud on the end of the plastic core barrel, but nothing inside, so we’re trying to figure out what to do differently. On the first core that we collected yesterday, we let the core barrel run on the cable all the way to the bottom and captured 17 cm of sediment. For the next few runs we have been dropping the barrel from different distances above the seafloor, but haven’t been getting anything back because either the trigger mechanism hasn’t released, or the core is bouncing off a hard surface (perhaps a glacial till that is close to the surface, or a rock), or we’re losing the mud on the way up through the water column to the surface of the ice.

JR and Hedley work hard to figure out a solution, while the rest of the team thinks about “what-if” scenarios to try to contribute to a solution. Hedley checks the seals on the inner part of the barrel and discusses the sensitivity of the trigger mechanism with JR and Tristan. They decide to make a few modifications and then change our strategy about how high to drop the barrel above the seafloor. We’ll go back to having a zero drop distance and then gradually pull back up above the seafloor to see what happens.

We have another failed attempt, but then success and a new discovery!

We’ve captured a sponge and a network of worm tubes filled with sediment. We’ve recovered life from the seafloor at Coulman High! Now we know what to do, and we continue to get increasing length cores. It’s a good day!

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