Sampling the Ocean and Not the Ship

Posted on January 25, 2011 by Whitney King

Metal-free Niskin Sampler

In my last post I described our workhorse sampler, a rosette holding twelve Niskin bottles.   This is a great sampler for many analytes like dissolved oxygen, salinity, and major nutrients (nitrate, phosphate, silica, and ammonia) because the sampler is not made of these things.   However, the rosette and hydrowire are made of iron.   If you look carefully at the surface water as you deploy the rosette you can see the rust streaming off the hydrowire that connects the rosette to the ship.   This is can be a real problem if you job is to measure iron.   It wasn’t until oceanographers like John Martin (Colby class of 1962) developed metal free sampling techniques that collecting uncontaminated samples for metal analysis was possible. Continue reading →

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Life in the Low Latitudes

Posted on January 21, 2011 by Angela Warner

Sunset in the South Atlantic

As I hear about all the snow that has hit the northeast in the past week, I realize how grateful I am to be enjoying summer weather here in the Southern hemisphere.  The past few days we have been working our way up to 32 degrees South, the point on our cruise closest to the equator.  Once we reach this destination, we will shift our course towards 60 degrees South.  Our cruise track has been slightly altered from the original plan in order to account for inclement weather we may experience later on in the trip.  I was excited to hear that this new route will bring us within six miles of the island of South Georgia! Continue reading →

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Sampling at Sea: Everyone Must Obey the Bottle Cop

Posted on January 20, 2011 by Whitney King

Rosette Sampler with 12 bottles

In one of my earlier posts I described the scheduling challenge of stopping to take samples while still moving the ship eastward toward Cape Town.   We are now at station 22 out of a total of 120 stations.   This puts us about one day behind schedule and Barney has decided to eliminate six stations to put us back on track and to allow for at least one day of bad weather.   The crew doesn’t like to deploy gear over the side when the wind is blowing over forty knots, and any wind over thirty makes sampling VERY interesting.    It has been blowing between twenty to thirty knots for most of the trip and we are getting pretty good at collecting samples in rough weather.

The scientists on the ship use at least five different sampling systems.  As a bit of background, it is important to know that the ocean is not uniform top to bottom.  The surface water is warmer than the deep water and can have very different concentrations of oxygen, nutrients, and dissolved metals.   On this cruise we use different sampling gear to collect samples from just a few centimeters below the surface to over 5000 meters in depth. Continue reading →

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