WHAT DO YOU DO IN THE DRAKE?

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Transmission from Karen Stamieszkin:

The Drake Passage is infamous for its trying conditions.  It has been a formidable foe to voyagers from all periods of human history because the entire Southern Ocean, which circumvents the Antarctic continent, is squeezed dramatically between the southern extent of South America and the tip of the Antarctic Peninsula.  You can think of it as taking a bunch of marbles rolling them around in a donut-shaped track.  In some places the track gets wider, and the marbles are spread out, but in some places, the track is very narrow, so the marbles have to pile on top of one another to get through.  Likewise, when the Southern Ocean squeezes into the Drake Passage, some water has to go up and some down, making the gigantic waves for which the Drake is known.  We had a relatively smooth crossing this time: only about 15-18 foot seas- no big deal (haha).

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Here, a wave breaks over the lower deck.  I am taking this picture from two decks above the one being covered by the wave.

While traveling through the Drake, which takes 3 to 4 days depending upon conditions, we cannot conduct much science.  We do collect information about temperature and salinity in the upper 900 or so meters of the water column.  We call these collections XBTs and XCTDs, for the instruments used.  Both are small torpedo-like units that are dumped over the side of the boat from a "gun"; as they descend into the water, a very thin copper wire trails behind relaying information about the conditions the probe meets through a cable in the gun, to the computer.  The XBT only reads temperature, while the XCTD reads temperature and conductivity, a proxy for salinity.

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The XBT probe.

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Here, Nathalie holds the XBT gun before launching the probe.  Sidenote: Nathalie is a first grade teacher going to Palmer Station to help study flies that freeze solid in the Antarctic winter, can lose up to 30% of their body moisture, and survive the whole ordeal eating moss.  She will be doing education and outreach.

The temperature profiles tell us about how deep the water is mixed, indicated by a constant temperature.  Maxima and minima following the mixed layer indicate different bodies of ocean water of different origins.

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In this picture, besides half of my face, you can see that there is a lot of noise caused by the rough seas at the surface, then a mixed layer down to about 50 meters, a temperature minimum, and finally a constant temperature to the bottom of the profile.  This cold subsurface layer is thought to be caused by the formation of dense, cold, salty water off of the Antarctic continent, which then sinks below the surface water of the Antarctic Circumpolar Current (ACC).  The water is particularly cold due to the conditions in which it forms.  It is relatively salty because as ice forms, fresh water is taken up and frozen, and salt is excluded, leaving saltier water behind.  The saltier and colder water is, the more dense, or heavy is it; fresher, warmer water is less dense, or lighter.  These principals of water density related to temperature and salinity in large part govern ocean water circulation world-wide.

Other activities that are popular during the Drake crossing include: sleeping, movie-watching, email checking, looking for whales and other critters, and of course, celebrating NEW YEARS! 

Happy 2012 to everyone- may it be a year of adventure and new discoveries!

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This page contains a single entry by Nick Record published on January 9, 2012 6:15 PM.

PUNTA ARENAS, CHILE was the previous entry in this blog.

ARRIVAL AT PALMER STATION- CARNAGE is the next entry in this blog.

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