Day 3 String watch

The bubble buoy on a tether (marked by the red float)

Fred on string watch

Dolphins around the bubble buoy

Albatross pecking at the tether

The science program for today included the spar buoy which measures wave activity. During the experiment the sensors at the foremast and in the hull of the ship measure the concentration of gasses (it's mostly CO2 we're after) in the atmopshere and in the surface layer of the ocean. The difference in CO2 concentration between the two is crucial, as it decides whether CO2 is drawn out of the atmosphere into the ocean or vice versa. The goal of these experiments is to relate the CO2 transfer to wind and wave activity, particularly breaking waves. Waves grow higher and eventually break if the wind is stronger and/or the fetch (length over which the wind blows) is greater. The speed at which CO2 is drawn out of the atmosphere into the ocean depends on a number of these variables - wind speed, fetch length, wave breaking, background sea state, existing gas concentrations in air and water etc. I already talked about the role of bubble formation during wave breaking in previous articles. This aspect is also being investigated here.

Several theories exist for a formula that calculates the rate of CO2 transfer between ocean and atmosphere. But these equations need to be confimed by actual field experiments, and that's why the air-sea gas exchange team is here to take these measurements. Measuring gas concentrations is a tricky business and the instruments needs to be very precise as there are only very small differences in the CO2 concentrations in the atmosphere compared to the oceans. These differences are so tiny that they are close to the accuracy of the instruments. That'ss why it pays to go to the Southern Ocean where the air contains measurably more CO2 than the ocean compared to other parts  of the world.

The spar buoy with its wave sensor was deployed in the water for the entire day, and in the afternoon I took over "String watch" - co called because the buoy is tethered to the ship by a rope (the 'string') and we need to watch it so it doesn't drift into the propellers of the ship. During my round of stringwatching I kept an eye on the tether, but mainly observed the wild life around the ship. Black-browed albatrosses and giant petrels whizzed around the ship and the buoy all day. Rock shags fluttered by, and Gentoo penguins from a nearby colony occasionally popped up at the surface to check us out. The most fun was to watch a pod of Peal's dolphins that kept appearing in regular intervals. Between 3 and 7 of them were visible at the surface at any one time, and once they swam past the buoy in formation. I wonder whether the splash they created (photo above) will be visible in the wave data.

The buoy will be out for a while longer - into the small hours of the morning - and the night shift of string watch will be keeping an eye on everything. Tomorrow we will take up position further south.