August 13, 2015: Throwing Darts

Today was a day of comings and goings, coring and toy boats. Well, not really a toy boat (although it seems like that compared to Oden) more like our secret weapon.  R/V Skidbladner.  That was the magic boat of Norse mythology that fit in a pocket but carried all the gods through sea, land, and sky.  Reincarnated as the 6-meter Stockholm University mapping boat, the new Skidbladner is equipped with state-of-the-art multibeam sonar and advanced positioning systems, coupled to a land transmitter that corrects for waves and tides, yielding superbly precise sea floor maps in shallow water where Oden can’t go. Co-chief scientist Martin Jakobsson and bathymetry god Larry Mayer deployed off Hall land to map the delta and iceberg features.

Skidbladner PerchSkidbladner Water

I waved goodbye to Skidbladner and took Oden and the rest of the team (less the two helicopters that left for beach and boulder surveys) coring in a transect of four sites crossing the glacial moraines left by a retreating Petermann Glacier. We expected these to lie in the ocean, connected to where the Petermann Moraine, really a side (lateral) moraine has been mapped on land.  Our goal was to core through the sediment cover and “kiss” the gravelly moraine beneath, from the oldest moraine back to the fjord itself.

Piston Corer

This is the piston corer, which reaches greater depths through a weight and lever device.

Core Catcher

This conical catcher keep the mud from sliding out upon extraction.

A problem:  the coring targets are tiny pockets of sediment, sometimes just a few 100 meters across. The wind and currents are strong, blowing Oden in nearly unpredictable directions at speeds up to 2 knots (about 2 miles per hour).  And it takes about an hour to deploy a core and get it to the bottom.  Oden is designed to break ice, with strong engines, not to stay on station. So for a coring station we must turn the engines off and drift. A lot.  We start a station about 1-2 miles up current (or at least the direction we guess is up current), lower the coring gear as fast as we can almost to the sea floor, the wait to drift across the target area and the drop it as fast as possible.  This worked perfectly today – we hit bottom within two meters (about 6 feet) of our target. Think about throwing a dart from a moving train two miles, then letting it drop through a half mile of water, and hitting a bullseye. We did that today.  High fives and smiles all around.  And the core achieved our goals of recovering material to date the retreating ice.  We’ll do that back in the lab at home.

Core Extraction

After that scientific feast, for dessert we lowered a CTD and water bottles and sampled the deepest waters that flow into Petermann Fjord.  A pretty much perfect day… 18 hours of work went by in a flash.

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