With no land masses except Antarctica as the southern boundary, the Southern Ocean is characterised by latitudinal fronts. Four frontal zones are recognised:
- the Sea Ice Zone (SIZ) with the northern limit being defined as the maximum northern winter extent based on the 15% ice cover threshold,
- the Permanent
Open Ocean Zone (POOZ) between the SIZ and the Polar Front, which lies within the
ACC but displays a marked change in temperature and salinity,
- the Polar Frontal Zone (PFZ), between the Polar Front and the Sub-Antarctic Front, which is the northern boundary of the Antarctic Circum-polar Current (
ACC),
- and the Sub-Antarctic Zone (SAZ), north of the Sub-Antarctic Front, which is a noted biogeographic boundary for
zooplankton.
Data within each frontal zone have also been subdivided into the eastern Antarctic Sector and the Ross Sea sector.
See www.sahfos.org for further details.
The data is derived from
zooplankton sampled by Continuous Plankton Recorders (CPRs). CPRs are typically deployed from commercial ships on their normal routes of passage. The
CPR is a robust mechanical device towed behind ships in the near-surface waters (usually commercial ships but also research, military and fishing vessels) that filters plankton from the water along the ship’s path onto a length of 270 µm mesh. The mesh is divided into separate 18.5 km samples after the sampling (9.25 km in the Southern ocean Survey), with time, date and position of each sample calculated from ship’s log information or recorded underway GPS/environmental data. The plankton are identified with a microscope and counted. Full details of the methodology can be found in Batten et al. (2003) and Hosie et al. (2003), and details on data analysis and utility in Richardson et al. (2006).
Batten, S.D., Clarke, R.A., Flinkman, J., Hays, G.C., John, E.H., John, A.W.G., Jonas, T.J., Lindley, J.A., Stevens, D.P., Walne, A.W. (2003)
CPR sampling – The technical background, materials and methods, consistency and comparability. Progress in Oceanography, 58, 193-215.
Hosie, G.W., Fukuchi, M., Kawaguchi, S. (2003) Development of the Southern Ocean Continuous Plankton Recorder Survey. Progress in Oceanography 58 (2-4), 263–283
Richardson, A.J., Walne, A.W., John, A.W.G.J., Jonas, T.D., Lindley, J.A, Sims, D.W., Stevens, D., and Witt, M. (2006) Using continuous plankton recorder data. Progress in Oceanography, 68, 27-74.