Ocean circulation, eddies, basin oscillations, and decadal variability of the Argentine Basin

1
Ocean circulation, eddies, basin oscillations,
and decadal variability of the Argentine
Basin Lee-Lueng Fu Jet Propulsion
Laboratory Pasadena, California 7th Decadal
Climate Variability Workshop April 30-May 3,
2007 Waikoloa, Hawaii
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Schematic of South Atlantic Circulation
SSH Standard Deviation
cm
3
Trend of sea level variation (1993-2006) Altimetry
data from TOPEX/Poseidon and Jason
mm/year
4
Yearly running mean of sea level at the center
of the Argentine Basin
mm
5
Components of sea level variations at the center
of the Argentine Basin
total sea level
residual
mm
thermosteric
6
Trend of thermosteric sea level (from XBT data,
courtesy of J. Willis/JPL)
Trend of sea level
mm/year
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Trend of sea level caused by barotropic ocean
circulation
Zapiola Anticyclone
mm/year
at surface
at 3000 m
Dynamic topography (Niiler, Maximenko,
McWilliams, 2003)
cm
8
Eddy SSH standard deviation and propagation
velocity from altimetry
cm
10 km/day
Fu (2006)
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Trend of eddy kinetic energy variation
Divergence of eddy propagation velocity
x
x
(0.01/day)
(cm/sec)2 /year
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Eddy kinetic energy
cm2/sec2
West region
Eddy kinetic energy
East region
cm2/sec2
Sea level
Center region
mm
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Zonal wind stress averaged over (305-325E, 40-50S)
dyne/cm2
Wind stress curl averaged over (305-325E, 40-50S)
10-7 pascal/m
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ECCO eddy-permitting OGCM simulation (18 km
resolution)
Zapiola Anticyclone Circulation
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Eddy kinetic energy in ECCO-2 simulation
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A 25-day oscillation of the basin
3-day snapshots of high-passed SSH (period lt 30
days)
Zapiola Rise
Fu et al (2001)
15
Mesoscale energy vs wave amplitude ( at periods
of 110-150 days)
Fu (2006)
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• Summary
• Satellite altimetry data reveal a decadal trend
  of sea level rise in the center of the Argentine
  Basin.
• The sea level rise is caused by water mass
  accumulated in the center of the basin associated
  with an increase of the barotropic circulation of
  the Zapiola Anticyclone.
• Eddy energy on both sides of the anticyclone
  show an increasing trend on decadal scales.
• Convergence of eddy energy might have driven the
  increase of the anticyclone and hence the sea
  level rise.
• There is also energy exchange between eddies and
  large-scale, 25-day waves rotating around the
  basin.
• Sea level variability in the basin involves
  complex interactions over a wide range scales
  from 25 to 5000 days.