Earth Institute News
Contact: Mary Tobin
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Reports From the Field
The Antarctic AnSlope Expedition
February 25 through April 11, 2003
AnSlope Cruise 1, Week 3
Tuesday, March 18, 2003, from Arnold L. Gordon, Chief Scientist
Aboard the R/V NATHANIEL B. PALMER, Ross Sea, Antarctica...
For the third week of the AnSlope cruise, we moved to the eastern end of our study area, somewhat north of the continental slope of the Ross Sea. In order to understand the impact of the margins on ocean stratification and overturning, we have to stand a bit away from those margins to see what waters drain away from the complicated margin processes, hence our northern boundary condition transect. Along the northern route, as we make measurements of the ocean from top to bottom, we passed through pancake ice. Pancake ice is newly formed ice, with thin small floes that do little to impede the foreword motion of the ship. They remind one of pancakes (the real thing is available for breakfast nearly every day aboard the ship). As the cold weather progresses, these pancakes gets wider, thicker, freeze together, and soon become a field of impassible ice. We reached older larger ice floes towards the eastern end of the northern boundary section, and rather than use fuel to break the last 20 nm to the intended end-point, we turned to the south at 175°W, back to the continental margins to investigate the margin processes that stir up the ocean in that part of the Ross Sea. Our progress southward was often slow, but we occasionally found some north-south trending leads, or breaks in the ice that enables rapid movement. The skill of the Captain Joe [Capt'n Joe Borkowski III] and ice pilot Vladimir Repin in finding these leads by 'reading' the subtleties of the ice, even as weather conditions obscure the view, is so important to our program.
We believe that in the east, the dense shelf water is not as salty as more melt water from the great floating masses of glacial ice to the south reach the continental margin. Some of this melt water contributes to the dense plumes that descend into the deep ocean. We also think we see evidence that not all of the glacial melt descends to the deep -- some seems to spread out horizontally at depths near 100 m. This is important if we are to describe the complete glacial melt role in structuring the ocean stratification.
We wonder what surprises await us as we look at the ocean condition in this part of the Ross Sea, which can be considered the upstream source of some of the water characteristics we see in the western Ross where the AnSlope moorings are situated. We have an idea of what is happening, but "real-world" science has a habit of surprising our over simplified views of how things work, and experience has us ready to be surprised. This is what exploration is all about.
We did have a nice deviation from the ice breaking and data collecting routine with a three hour stop at a thick ice floe. We were free to wander off the ship and walk on 1-meter thick ice floating over 2 kilometers of seawater. A long way down, and cold, with the air at -12°C and the seawater just below the ice at -1.9°C. Luckily no wind, and a little bit of sun. Seeing the ship, our home for the 45-day cruise, is quite a sight. A group of Emperor Penguins were near by, but following Antarctic Convention, we let them be; though a few good pictures were snapped (or more accurately recorded on flash cards). What did they think of us, in our bright red coats? I think it might not have been too flattering.
I often refer to the adventure of exploration and our sense of discovery that is characteristic of field science, but I should also stress the long hours of tedium. Like your corner convenience store, we are a 24/7 operation. As mentioned in earlier reports, this does bring the group together in a shared experience, and the humor and fun is the stuff that forms fond memories brought up years from now.