Processes Influencing Carbon Cycling: Observations of the Lower limb of the Antarctic Overturning (PICCOLO)

The vast, remote seas which surround the continent of Antarctica are collectively known as the Southern Ocean. This region with its severe environment of mountainous seas, winter darkness, strong winds, freezing temperatures and ice is unsurprisingly one of the least explored and under-observed parts of the global ocean. However, because of these extremes, it plays a large and still unquantified role in Earth's climate system. In this region, large amounts of heat and carbon dioxide are exchanged between the atmosphere and the ocean.

The physical mechanisms controlling these atmosphere-ocean exchanges are the subject of the NERC ORCHESTRA programme. We propose within PICCOLO to concentrate on the role that chemistry and biology play within those exchanges. In particular, PICCOLO will focus on understanding the mechanisms that transform the carbon contained in the seawater as it rises to the surface near Antarctica, interacts with the atmosphere, ice, phytoplankton and zooplankton inhabiting the near surface, before descending to the ocean depths.

PICCOLO will undertake an ocean research expedition to the region close to Antarctica, as computer models and satellite images show that these are areas crucial for carbon processes. Freezing seawater in these regions releases salt into the water below, making it denser and therefore causing it to sink. Strong winds cause the sea ice to be pushed away from the Antarctic coastline, leaving areas of open water called polynyas. Within the polynyas the water has enough light during the summer to allow phytoplankton to grow, as well as providing dense waters which sink to the deep, driving a giant ocean conveyor belt which has a large impact upon Earth's climate system.

The PICCOLO team will measure the key variables that control the biological and chemical processes in this region including iron, nutrients, phytoplankton and zooplankton. Crucially the team will study the controlling rate terms between different parts of...