It takes us a little while to get up and running doing science. When we leave port in Punta Arenas we pass through both Chile’s and Argentina’s territorial water. Both countries require permits to collect oceanographic data in their waters. Since our focus is the Antarctic, we don’t have those permits. We have to wait to collect data until we exit both countries’ EEZ (Exclusive Economic Zone- a swath of ocean extending from the shoreline to 200 miles offshore in the open ocean).
Once we clear the EEZs were are free to start collecting data. At this point, we are still too far north to catch the Antarctic critters we are interested in. However, the conditions in the more northerly water could impact the zooplankton living further south. The first science we start involves sampling the water column while we continue to transit further south.
We deploy drifter buoys for colleagues at NOAA studying world oceanographic conditions. The buoys are fitted with an array of sensors such as temperature, salinity, and GPS position. The buoys are also equipped with a satellite link so that the data can be transmitted back to the office without anyone needing to go retrieve them. We deploy the buoys by throwing them over the back of the ship out into the water. It’s super easy.
The other tool we using to sample the water column before we get to our survey grid is the XBT. These are small probes that measure temperature at depth. We launch them using something that looks like a gun. In reality the “gun” is a holster that connects the probe to the ship’s electronic system using a very thin copper wire. This allows us to get real time data. The probe has a lead weight at its front end, then sensors, then a coil of very thin copper wire.The copper wire spooled inside the probe is several kilometers long. The probe sinks to 760 meters before it stops transmitting, the while the ship is travelling away from the probe We launch the probe by gently tipping it overboard using the “gun”. We amuse ourselves by telling the new folks that it is an actual gun and explosions are possible when launching. We try to make them wear truly silly “safety gear”. This year’s target was masters student who has never been to sea before.
Brynn , the newbie, had a picture perfect successful launch. But, she was totally confused as to why there was no “bang”, no nothing other than a little “ploop” as the probe hit the water. It was too hard to contain our laughter, so we let her in on the joke. She was a great sport about it.
When we launch an XBT someone down in the science deck is responsible for data collection. This involves hitting a button to begin collection and watching the temperature plot to make sure that the wire doesn’t hit the ship. When the copper wire hits the metal ship we get really wonky readings.
Temperature plots in polar oceans are the polar opposite (pun totally intended) of the plots you would get in more temperate regions. Here deeper water is warmer than surface water. Near surface water is continually cooled by the cold air temperature. The deeper water holds the heat. So up above is a very typical polar water temperature at depth plot.
It won’t belong now before we settle into our zooplankton sampling routine!