Drake Passage adventures
Our second last day on the Plancius. We woke up to a slightly rough sea on the Drake Passage, however, it was much calmer than expected. The morning was quiet as we went about our routine marine mammal and seabird surveys. We were however, given an insight into one of the afternoon activities – deploying an Argo float from the ship.
The Argo float was scheduled to be deployed at 2 pm and as people gathered around the back of the ship to see science in action we were given an explanation of what the float does. A simplistic way to describe an Agro float is as a large, self-sufficient, passively floating, CTD, which has been discussed in previous blog posts. The float is large, as tall as a small person. Once the float is deployed it will descend to around 2km depth, drift for about 10 days and ascending again. This cycle will be repeated for about 4 to 5 years. On the ascent the Argo float measures the temperature and salinity of the water and transmits this data when it reaches the surface via satellite to a ground station. The temperature and salinity of water are important measures as together they determine the density if the water. Generally water density increases with increasing salinity and decreasing water temperature. The density of water is an important measure as it plays a role in understanding currents and sea level. The float that was deployed today will send important information to scientists for use around the world.
As the Argo float was being deployed, there were also exciting sights! A number of people, including myself, who had vacated the crowded recommended 4th deck viewing area in search of a less populated area had spotted something more interesting at the bow of the ship – Hourglass dolphins! Hourglass dolphins have a distinct black and white hourglass pattern which is easily identifiable from both the side and top of their bodies. We were lucky to witness the dolphins swimming gracefully on both side of the ship, seemingly ducking under the bow to go quickly from one side to the other. The dolphins stayed with the ship and swam in this way for around 30 minutes. This was such a great experience as only a few of us had seen hourglass dolphins in the Drake Passage heading down to Antarctica, and those who had seen them had spotted them for only a few seconds.
Throughout the day, between Argo launch, hourglass dolphin sightings and surveys all of the students were working hard to compile a presentation for the passengers about what we had been doing on the ship and the different animals that we had seen throughout our expedition. Although we were short on time we worked together and produced graphs and a presentation with time to spare for a practice run. We were ready to present during the evening recap. The presentation began with life size cloth replicas of an hourglass dolphin and a mike whale. This certainly got the passengers’ attention and they were all ears for our presentation. We described the surveys we had carried out and the secchi disk and CTD measurements we had taken. We also presented graphs and pictures of where we had seen certain species of animals, which acted as a nice recap of sightings for both students and passengers. Although many students were understandably nervous about presenting we received nothing but praise and thanks from the passengers (and lecturers!) who had enjoyed our small recap of our trip, making our hard work today really worthwhile.
written by Kathleen Herbison