To understand and model Earth’s climate it is essential that we understand clouds. This means not only knowing how many clouds there are, but also what type and how they were formed.

The Southern Ocean is known for clouds that contain both liquid and ice – a particularly poorly understood cloud type. The ice crystals in clouds form around tiny particles, called ice nucleating particles (INPs), but we know very little about the type and distribution of these particles in the Southern Ocean.

In 2016, Centre of Excellence for Climate Extremes researchers and colleagues measured Southern Ocean INPs for the first time in over four decades. The numbers of these particles were extremely low compared to other oceans and 100 times lower than the previous Southern Ocean measurement program conducted in the 1970s.

The researchers also found ocean-derived INPs were organic, supporting a link between these particles and plankton blooms. It’s a link the researchers will explore further in the future. These data provide a desperately needed benchmark for the number of ice crystals that may form the remote and poorly understood clouds of the Southern Ocean.


  • Paper: McCluskey, C. S., Hill, T. C. J., Humphries, R. S., Rauker, A. M., Moreau, S., Strutton, P. G., Chambers, S. D., Williams, A. G., McRobert, I., Ward, J., Keywood, M. D., Harnwell, J., Ponsonby, W., Loh, Z., Krummel, P., Protat, A., Kreidenweis, S. M. and DeMott, P. J. (2018). Observations of ice nucleating particles over Southern Ocean waters. Geophysical Research Letters doc: 10.1029/2018GL079981.