Variety of station work – science at its finest

The Southern Ocean pumps air into the World Ocean, especially the oxygen essential for the fauna living on the seafloor. Meteorological conditions at the margins of the Antarctic ice shelves are responsible for the production of so-called “Antarctic Bottom Water (AABW)”. Strong, seaward directed winds cause cooling and formation of new sea ice in the surface water and thus increase the salinity in the water column. Cold and salty water has a high density. Its “heavy weight” pushes it over the (shelf) edge into the abyss from where it spreads northwards in all directions. The reader will immediately notice the important role of the winds in this process which is important for life at the seabed and climate. This brings us back to the laser.

“Polynya” is the Russian word for an ice-free area in a polar sea – a term adopted worldwide. Even A23A has a polynya on its down-wind flank, where – free of any sea-ice obstacles – all gear is deployed during a one-day long station. The value of the collected data and samples is satisfactory for all science disciplines, even if their amount is relatively small. This can be expected for an icy desert which is not an icy jungle after all. Only the oceanographers find sufficient water for filling their bottles anywhere and anytime. At the end of the station we turn eastward around the northern tip of A23A, and immediately “Polarstern” and the sea ice celebrate a crushing and vibrating reunion.

A research vessel is well suited for studying the behaviour of an ocean for several weeks or even months; when it is on a mission to a polar sea preferably during summer time. But what happens during the rest of the year? The oceanographers invented moorings for long-term monitoring and survey: a chain of instruments clamped to a long rope, which is kept on the sea floor by anchor weights and which is kept upright by floaters. After 2-3 years of constant measurements the oceanographers return, “call” the acoustic releaser attached to the wheels and persuade it finally to do its job - and then the mooring resurfaces.

What, if our working area is affected by a huge cover-up? Again the sea ice is dictating what we are (not) allowed to do. The area of the moorings we are heading, to is heavily covered by sea ice, and therefore it is unwise trying to recover them. Moorings that attempt to resurface under ice floes are hard to find. If we wait until the sea ice has disappeared, all our flight tickets home will be invalid. Therefore, we decide to let the sensors measuring for another year – and hope that the batteries will last until then. Despite sea-ice cover (!) three other moorings with their full data sets of precious time series are recovered successfully. This makes especially one of the PhD students on board happy. Her project is the study of the interesting interactions between ice, ocean and the seabed landscape. Until the next weekly letter, we will (among other things) continue to transit through and map the area around the mooring sites.

Crew and ship-board scientific party send best wishes from the ice age!