August 22: Shelf Team Returns to Oden

08-23_IceTeamReturnsWe accomplished lots of things today.  Gale warnings came in the weather report, so we decided to work non-stop, finishing up our current work in Canadian waters and heading back over to Petermann Fjord, which is more sheltered.  That meant we could speed up the transfer of the ice shelf team back to the ship – they have finished their work on the ice, so we want to use a trip back to the fjord to get them and all their gear – 12 tons takes more than a day to move via helicopter.  But all of this foretold a long day ahead.

In the wee hours we finished a transect of sites measuring water temperature and salinity across southern Robeson Channel – the pathway to the Arctic Ocean.  The ice prevented us from getting as far north as we would have liked, but we got far enough and near the Canadian coast and found warm-salty water flowing in from the Arctic near the bottom, as predicted.  Hooray, theory works!  This water will eventually find its way into Petermann Fjord through the convoluted pathway of channels we have mapped.  Lots of ideas are bouncing around the ship about how this might actually work – we suspect that more warming is in store for Petermann Fjord in coming years, and this is probably not good news for the ice shelf.  We took a sediment core on the Canada side of the channel as well, hoping to trace changes in these water-masses through time in the chemistry of the preserved foraminifera that lived there.  This will be an analytical challenge, but worth the effort.

The beach team reported a beautiful outcrop of sediment yesterday on the Judge Daly Promontory of Ellesmere Island providing evidence for retreat of a glacier into Archer Fjord.  Dropstones in the marine clay reveal a graveyard of ancient dirty icebergs loaded with rocks from many sources, including Greenland. This is like taking a sediment core by walking around… but of course we must figure out the complications of being uplifted onto land.  It will be worth dating this sequence.

On the way back to Petermann Fjord we filled some gaps in our map of the sea floor in Hall Basin, focusing on some unmapped bathymetric highs that might be old grounding lines of a much larger Petermann Ice Shelf; we hypothesize that the ice shelf jumped backwards into the fjord as it abandoned former grounding lines and retreated from its past glory.  Figuring that out for sure means some precise coring operations, and we can do that now that we have a complete map.

In Petermann Fjord by lunchtime, to our delight we found that the predicted storm dissipated; the waters calmed to a glassy sheen. This pleasant surprise opened a new opportunity! 08-23_Weather

08-23_SkidbladnerIn the calm waters we deployed the small boat R/V Skidbladner to map the shallows where Oden cannot go. While Skidbladner was mapping, the rest of the team recovered five superb sediment cores – one long core was taken from a place that was under the ice shelf three weeks ago but is now under open water. We are exploring new sea-floor territory that was inaccessible until now.  A couple of the new cores contain iceberg dropstones, similar to those we found across the way in Canada.

 After we got back to Petermann Fjord, both our helicopters were deployed all day long to pick up the ice shelf team and move some of their equipment to the ship.  All the instruments that hand under the ice to document temperature and salinity variations over the next few years are reporting back data – this is a huge accomplishment.  And the ice shelf team brought back a batch of new sediment cores recovered through the ice.  Helicopter use today and tomorrow while moving the ice shelf team has grounded the boulder and beach teams, but that’s OK because with all the new sediment cores in the lab, we need help from everybody to get it archived.  Everyone is now on the ship except the biology team, which is camping on Ellesmere Island.  Every team is reporting success.

08-23_IceShelfHelo
This was an amazingly productive 22-hour workday. Now for some sleep.  We are planning the last week of expedition operations.

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