Abstract's details
Malvinas Current volume transport at 41°S: a 24-year long time series consistent with mooring data from 3 decades and satellite altimetry
CoAuthors
Event: 2017 Ocean Surface Topography Science Team Meeting
Session: Science II: Large Scale Ocean Circulation Variability and Change
Presentation type: Type Oral
Contribution: PDF file
Abstract:
We combined altimetric data and the in situ data sets from three 10-years apart mooring deployments to compute a coherent and accurate 24 year-long volume transport time series of the Malvinas Current (MC) at 41°S. We used a look-up table method developed in Koenig et al. (2014) for the Antarctic Circumpolar Current in Drake Passage. We explored three types of shear to estimate the uncertainty derived from the lack of velocity data in the upper 300 m.
The mean MC transport over 24 years is 37.1 2.5 Sv and the standard deviation 6.6 1 Sv. Since 1993, annual mean transports have varied from 32 to 41 Sv and the three in situ records corresponded to low annual mean transports. The MC transport time series is not stationary, its spectral content evolves with time showing significant energy at the 30-110 days, semi-annual and annual period. The distribution of the MC volume transport anomalies is asymmetric, negatively skewed with larger negative anomalies than positive anomalies. Transport maxima appear to result from cyclonic eddies shed by the Polar Front that propagate northwestward following the 4000-5000 m isobaths and locally reinforce the circulation on the slope when they reached 41°S. During transport maxima, the northernmost extension of the Subantarctic Front (SAF) remain at its mean location (39.5°S). During minima, the SAF migrates southward, over the mooring line as positive anomalies shed by the Brazil Current overshoot move westward onto the slope. Apart from continental trapped waves, changes in the MC volume transport at 41°S show no correlation with upstream conditions on the continental slope.
The mean MC transport over 24 years is 37.1 2.5 Sv and the standard deviation 6.6 1 Sv. Since 1993, annual mean transports have varied from 32 to 41 Sv and the three in situ records corresponded to low annual mean transports. The MC transport time series is not stationary, its spectral content evolves with time showing significant energy at the 30-110 days, semi-annual and annual period. The distribution of the MC volume transport anomalies is asymmetric, negatively skewed with larger negative anomalies than positive anomalies. Transport maxima appear to result from cyclonic eddies shed by the Polar Front that propagate northwestward following the 4000-5000 m isobaths and locally reinforce the circulation on the slope when they reached 41°S. During transport maxima, the northernmost extension of the Subantarctic Front (SAF) remain at its mean location (39.5°S). During minima, the SAF migrates southward, over the mooring line as positive anomalies shed by the Brazil Current overshoot move westward onto the slope. Apart from continental trapped waves, changes in the MC volume transport at 41°S show no correlation with upstream conditions on the continental slope.