There is much more supercooled ocean water on planet Earth than previously noticed

Dr. Alexander Haumann is an Associate Research Scholar at the program in Atmospheric and Oceanic Sciences at Princeton University, USA. He is interested in the interaction between the ocean, ice, and atmosphere in the Southern Ocean and how these processes affect our climate through their influence on the exchange of heat and carbon between the deep ocean and the atmosphere. In a new study, he analyzed MEOP, Argo and ship-based observations to provide first estimates of the horizontal and vertical extent of supercooled waters in the Southern Ocean and analyzed their underlying processes.    

Supercooled ocean water refers to seawater that has a temperature lower than the reference freezing point. In our analysis, we combine all available data collected by instrumented marine mammals, data from profiling floats, and ship-board observations in the Southern Ocean to study this process. While supercooling has been previously found in certain coastal locations due to melting of Antarctic glaciers, we here show that it not only occurs in most of the coastal ocean, but also far away from the coast under the sea ice that forms in winter. This latter process has not yet been observed in the Southern Ocean. The supercooled water sinks from the surface under the sea ice down to more than a hundred meters in the form of convective plumes. These sinking supercooled plumes might be an important process to exchange heat, carbon, oxygen and nutrients between the surface and the deeper layers of the ocean, but they are not yet represented in global climate models.

Southern elephant seals appear to preferentially dive in such freezing cold waters along the sea-ice edge or in polynya regions, which is why the signal is very prominent in the MEOP database. An interesting question is if they prefer these waters because of environmental conditions, such as feeding. 

Check out the paper: Haumann, F. A., Moorman, R., Riser, S. C., Smedsrud, L. H., Maksym, T., Wong, A. P. S., Wilson, E. A., Drucker, R., Talley, L. D., Johnson, K. S., Key, R. M., Sarmiento, J. L. (2020). Supercooled Southern Ocean waters. Geophysical Research Letters, 47, e2020GL090242.

The paper and the importance of data collected by Southern elephant seals were highlighted in Nature (21 October 2020, © MEOP consortium 2015