Interannual variability of the Antarctic Circumpolar Current strength based on merged altimeter data

Linlin Zhang,Che Sun,Dunxin Hu

doi:10.1007/s11434-012-5040-3

Linlin Zhang, Che Sun + Show 1 more

Open Access

https://doi.org/10.1007/s11434-012-5040-3

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Abstract

Interannual variability of the Antarctic Circumpolar Current (ACC) strength is studied in stream-coordinate with twenty-year Absolute Dynamic Topography data from satellite altimetry. The stream-coordinate projection method separates the ACC from adjacent subtropical and subpolar gyres, enabling consideration of the zonal asymmetry of the ACC rather than assuming that the ACC is a purely zonal flow. It is shown that the ACC strength has large interannual variations with two recent peaks around 2000 and 2009. The interannual variability appears mainly in the Indo-Pacific sector of the Southern Ocean and the strongest signal is located south of Australia. The intensification of the westerly wind in 1998 and 2008 appears to cause the strengthening of the ACC via baroclinic processes.

Highlights

Interannual variability of the Antarctic Circumpolar Current (ACC) strength is studied in stream-coordinate with twenty-year Absolute Dynamic Topography data from satellite altimetry
In this study we further examine the interannual variability of the ACC strength based on the Absolute Dynamic Topography (ADT) data and explore its relationship with the westerly wind
To check whether the interannual signal of the ACC strength holds on the circumpolar scale, we calculated the ACC strength at different longitudes (Figure 3(b))

Summary

Data description

The ADT data from AVISO are used in this study. The ADT data consist of a mean dynamic topography and merged sea level anomalies (SLA). The mean dynamic topography is estimated from the combination of the latest geoid model, altimetric mean sea surface heights and in-situ measurements with an inverse technique [10]. The data are interpolated onto a global grid of 0.25° resolution between 82°S and 82°N and are archived in weekly averaged frames (available from October 1992 to the present). The tidal and sea level pressure corrections are incorporated into the data. Geostrophic currents are calculated from the ADT data. The mapped data combine measurements from ascending, descending, and neighboring tracks and are able to estimate the geostrophic currents better than the along-track data

Stream-coordinate projection method

Results

Discussion