Structure and Causes of the Pulsation Mode in the Antarctic Circumpolar Current South of Australia
The subsurface variability of potential temperature and salinity south of Australia along 1308E is studied over a 25-yr period (1980–2004). The study is done with fields provided by a global eddy-permitting model of the DRAKKARproject forced by atmospheric reanalysis. The analysis performed by C. Su...
| Main Authors: | , , , , |
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| Other Authors: | |
| Format: | Text |
| Language: | English |
| Published: |
2008
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.678.119 http://web.science.unsw.edu.au/%7Ematthew/2011_JPO_Dufour-et-al.pdf |
| Summary: | The subsurface variability of potential temperature and salinity south of Australia along 1308E is studied over a 25-yr period (1980–2004). The study is done with fields provided by a global eddy-permitting model of the DRAKKARproject forced by atmospheric reanalysis. The analysis performed by C. Sun andD. R.Watts with in situ hydrographic data is repeated. Sun andWatts have investigated the EOFmodes in streamfunction space along theWorldOcean Circulation Experiment (WOCE) SR3 section. In particular, they found that an EOFmode, which they called the ‘‘pulsation mode,’ ’ strongly dominates subsurface thermohaline variations. Here, it is found that, in themodel, an EOFmodewith spatial structure similar to the Sun andWatts pulsation mode dominates subsurface thermohaline variations in streamfunction space. The mode displays a maximum of variability at the Subantarctic Front (SAF) between Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW). The associated time series exhibits an intermittent interseasonal frequency (3–6 months), especially during three periods (1983–84, 1990, and 1994–96). Some energy is also found with a 4-yr period. Further analyses reveal that the pulsationmode can also be observed in physical space. The pulsationmode is found to be related tomovements of the SAF constrained by the bathymetry of the Southeast Indian Ridge. The pulsation mode displays many similarities with cold-core eddy events rather than being related to var-iations of the westerly wind stress, as previously proposed. The impact of those events on SAMW properties remains unclear. 1. |
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