Tuesday, September 16, 2008

Entering the Southern Ocean

Since we left Punta Arenas the ride has gotten progressively rockier. The weather is still very good with no big waves but there are long rollers and the boat sways with each one of these. Last night I figured out that if I stuffed my pillows between me and the edge of the bunk I didn't roll so much and I could get to sleep.

All morning we continued our path south through seemingly endless steel gray water. And then in the afternoon, something changed. We went through a dense fog bank and then I could feel the air temperature cool. I went down to the lab to see the sea monitors so I could watch the sea surface temperature. The water was getting colder, seemingly by the minute, when I glanced at the monitor it was actually below freezing, about -1 deg C. We were entering the Antarctica Circumpolar Current and the Drake Passage.

At the bottom of the world, the waters of the Atlantic, Pacific and Indian Oceans meet and swirl around in a wind driven fury. Sailors commemorate these storm tossed waters according to their lines of latitude as the “roaring forties”, the “furious fifties”, and finally the “screaming sixties”. As the ominous names suggest, the waters of this ocean are turbulent. Persistent westerly winds generate strong swells and, sometimes, mountainous seas. At about 60 deg south the Antarctic Circumpolar current separates the subtropical waters of the other oceans from the body of water known as the Southern Ocean. This is the world’s biggest ocean current, flowing eastward at an astonishing rate of 153 million cubic meters per second, roughly a hundred times the flow of all the world's rivers.
Our entry into the Southern Ocean was through the very young Drake Passage. The Drake opened when Antarctica moved away from South America 30 to 34 million years ago; this separation of the continents allowed the formation of the Antarctic Circumpolar Current which chilled the formerly forested continent and covered it is glaciers. The Drake and the Southern Ocean are deep: 13,000 to 16,000 feet over most of its extent, as compared to an average depth of 12,000 feet for the other oceans. If you want to read more about the Drake or the South Ocean, there is a good website here: http://www.ecophotoexplorers.com/antarctica_southocean.asp

As we entered The Drake, my shipmates and I became ocean researchers. Understanding the interaction of the Southern Ocean with its neighbors is important to an understanding of global climate, and so, every 20 minutes we collected data. In shifts we measured the temperature, salinity, oxygen concentration, pH and other parameters of surface water. Probes dropped over the side transmitted additional data to 1500 feet.

Standing outside we began seeing more wildlife. Southern Giant Petrels were in sight most of the time as were Wandering Albatross, Greater Shearwaters, Snowy Petrels, Wilson’s Storm Petrels, and Cape Petrels. All of these birds are great wanderers who live 90% of their lives over the ocean. To deal with the salt water, they have evolved salt glands that takes the salt out of the water and secretes it through their nostrils. Sometime later a Minke whale passed us headed the other direction.

Late in the afternoon we sailed into a field of sea ice. Wow. We had seen ice off in the distance a few times but this was the first time we had to travel through it. The ice was in crusty plates about 2 foot thick called "pancake ice" and as the ship slowed to 3 knots and plowed into it we could hear resounding booms as it hit the outer hull. Lots of people crowded onto the bridge and the mate let us all try a turn steering through the ice.

As afternoon gave way to evening, the ice grew thicker and the ship's crew turned on spotlights to see the path ahead. It seemed we were barely moving but the sound of the ice was a constant "knock, knock" on the hull. The mate swung the spotlights from side to side like giant eyes as he drove, looking for icebergs. Staring into the night from the bow was an unreal feeling. The powerful lights which apparently looked out a mile were eaten up by the darkness. I went to my cabin swaying with the ship and wondering what the next day would be like.

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