RVIB Nathaniel B. Palmer NBP-1102/S04P Weekly Scientific Report 08, 14 April 2011
from Jim Swift, SIO, Chief Scientist, and Alex Orsi, TAMU, Co-Chief Scientist
ca. 67°S, 92°W 1900 Z 14 April (1400 local) -2.6 degC (27 degF)
winds 14 knots from SW on station 123
Not everything on a research cruise goes as planned or hoped. We headed south last Saturday on a dual-purpose mission. The NOAA research ship Ronald Brown had stopped southward progress at an iceberg corridor near 69°S in 2008 when doing the north-to-south “P18″ cruise for our long-term program. We hoped to extend their work south to the Antarctic continental shelf break somewhere near 100°W. There was also the issue of mooring recoveries in that same general area for LDEO investigator Stan Jacobs. We knew from satellite images sent to the ship that sea ice covered nearly 100% of the surface in the area, but the Palmer can handle sea ice if not too thick. Still, we decided to first see how long it took us to get to our desired end point near the shelf break, allotting a certain maximum amount of time to icebreaking (in accord with our master plan for the remainder of the cruise), at which point we would know how much time we had for our work plus the icebreaking and steaming as we headed back north. Admittedly success with the mooring recoveries seemed remote because those could not be done in full ice cover, but one never knows until trying.
We reached the ice edge at the expected point along the track and progressed well at first. Then the going got tough, not so much because of ice thickness as because of the large amount of snow on the ice. Snow rubs against the ship’s hull much like sand would, sapping power and momentum as the ship presses forward. Only about 20 miles into the ice (20 miles straight line, but many more miles as we worked around large snow-covered floes) the Captain and Ice Pilot decided enough was enough. In the morning conditions looked no better, so we took advantage of being in a large floe to have a brief ice party for those on board, i.e. a chance to be on the ice a bit. We had a good time – playing soccer, walking around, playing in the snow. After everybody was back aboard we pulled into a nearby opening in the ice and did a CTD cast. That cast showed nothing remarkable compared to nearby data from 2008. There we were, nearly 50 miles from our targets – either the shelf break or Jacobs’ moorings – but we could not go further south. There being no point to lingering, we headed back north to the main 67°S line.
Thus we were not able to extend the P18 line south through the ice to the continental shelf break, and we were not able to recover any of Stan Jacobs’ ice-covered moorings. The only benefit of the way this worked out was that we spent one day’s time and fuel less on the excursion than planned so now have some weather time in the schedule before the end of science activities in five and a half days. This should enable us to not only reach the eastern end of the S04P section, but also to sample its eastern boundary region appropriately.
We always enjoy our trips through the ice. We did not see many penguins this time (though there were a few, including Emperor penguins) but there were many seals hauled out onto the thicker floes. The leads (openings in the ice) are freezing over and there are many 4 to 10-foot holes punched up through the thin ice. The culprits? Orcas (Killer Whales) on the lookout for seals on the thicker ice nearby. Jim saw a pair of them stick their heads out of one of the holes to take a look-see.
The weather has been unusually good. That may well change, but we are back on “the line” and for now we are mowing down the final stations one by one, making very good progress. Everyone has their sights set on keeping steady and focused: Get the job done. Then go to port!
All is well on the Nathaniel B. Palmer.
Jim and Alex