Antarctic sea ice and climate variability over South America

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Antarctic sea ice and climate variability over
South America

• Compagnucci Rosa Hilda
• Barreira Sandra
• Projects X095 UBACYT and PIP 05-5006 CONICET

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OBJECTIVE Association of anomalies of sea ice
concentration in the southern oceans
with atmospheric circulation
conditions precipitation over South America
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• Data
• Monthly sea ice concentration anomalies (SICA)
  Weddell, Amundsen and Bellingshausen Seas (25 km
  x 25 km) for 1979-2000, from the Scanning
  Multichannel Microwave Radiometer and Special
  Sensor Microwave/Imager (Nimbus-7 SMMR and
  DMSP-F8, -F11 and -F13) processed by NASA Goddard
  Space Flight Centre using NASA Team algorithm
• NECP/NCAR reanalysis
• University of Delaware Air Temperature and
  Precipitation

• Methodology
• Patterns of SICA obtained by Principal Component
  (PC) Analysis in T-mode (correlation between SICA
  spatial fields) Varimax rotated
• Composite of the variables for the months
  clustered by the PC

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The 6 PCs Varimax rotated
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WINTER-SPRING
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1st PC Direct Mode
Air temperature anomalies
850 hPa anomalies
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Precipitation anomalies 1º PC direct mode
NCEP/NCAR precipitation rate
Delaware precipitation
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1st PC Inverse Mode
Air temperature anomalies
850 hPa anomalies
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1st PC Direct Mode
Air temperature anomalies
850 hPa anomalies
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Precipitation anomalies 1º PC inverse mode
NCEP/NCAR precipitation rate
Delaware precipitation
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Precipitation anomalies 1º PC direct mode
NCEP/NCAR precipitation rate
Delaware precipitation
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2nd PC
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2nd PC Direct Mode
Air temperature anomalies
850 hPa anomalies
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Precipitation anomalies 2º PC direct mode
Delaware precipitation
NCEP/NCAR precipitation rate
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2nd PC Inverse Mode
Air temperature anomalies
850 hPa anomalies
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2nd PC Direct Mode
Air temperature anomalies
850 hPa anomalies
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Precipitation anomalies 2º PC inverse mode
Delaware precipitation
NCEP/NCAR precipitation rate
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Precipitation anomalies 2º PC direct mode
Delaware precipitation
NCEP/NCAR precipitation rate
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5th PC
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Air temperature anomalies
5th PC Direct Mode
Strong gradient
850 hPa anomalies
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Precipitation anomalies 5º PC direct mode
Delaware precipitation
NCEP/NCAR precipitation rate
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Air temperature anomalies
5th PC Inverse Mode
Weaker gradient
850 hPa anomalies
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Air temperature anomalies
5th PC Direct Mode
Strong gradient
850 hPa anomalies
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Precipitation anomalies 5º PC inverse mode
Delaware precipitation
NCEP/NCAR precipitation rate
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Precipitation anomalies 5º PC direct mode
Delaware precipitation
NCEP/NCAR precipitation rate
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WINTER-SPRING 2006
SICA 5th direct mode derived to 2nd direct mode
negative sea ice concentration over
Bellingshausen / Amundsen seas Winter previous
to the El Niño mature phase waiting for this
summer

• 5th direct mode

• 2nd direct mode

Is the SICA pattern a help to forecast the ENSO
cycle?
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SUMMER
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Air temperature anomalies
3rd PC Direct Mode
850 hPa anomalies
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Precipitation anomalies 3º PC inverse mode
Delaware precipitation
NCEP/NCAR precipitation rate
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Air temperature anomalies
3rd PC Inverse Mode
850 hPa anomalies
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Air temperature anomalies
3rd PC Direct Mode
850 hPa anomalies
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Precipitation anomalies 3º PC inverse mode
Delaware precipitation
NCEP/NCAR precipitation rate
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Precipitation anomalies 3º PC direct mode
Delaware precipitation
NCEP/NCAR precipitation rate
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(No Transcript)
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4rd PC Direct Mode
Air temperature anomalies
850 hPa anomalies
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Precipitation anomalies 4º PC direct mode
Delaware precipitation
NCEP/NCAR precipitation rate
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4rd PC Inverse Mode
Air temperature anomalies
850 hPa anomalies
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4rd PC Direct Mode
Air temperature anomalies
850 hPa anomalies
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Precipitation anomalies 4º PC inverse mode
Delaware precipitation
NCEP/NCAR precipitation rate
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Precipitation anomalies 4º PC direct mode
Delaware precipitation
NCEP/NCAR precipitation rate
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(No Transcript)
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6th PC Direct Mode
Air temperature anomalies
strong gradient
cold
850 hPa anomalies
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Precipitation anomalies 6º PC direct mode
wet
Delaware precipitation
NCEP/NCAR precipitation rate
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6th PC Inverse Mode
Air temperature anomalies
weak gradient
warm
850 hPa anomalies
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6th PC Direct Mode
Air temperature anomalies
strong gradient
cold
850 hPa anomalies
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Precipitation anomalies 6º PC inverse mode
dry
Delaware precipitation
NCEP/NCAR precipitation rate
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Precipitation anomalies 6º PC direct mode
wet
Delaware precipitation
NCEP/NCAR precipitation rate
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CONCLUSIONS

• 3 SICAs PCs patterns prevail in winter. Only 2
  of them are dipolar
• 3 SICAs PCs patterns prevail in summer. Only one
  of them is clearly dipole
• The direct and inverse modes are related to
  opposite circulation anomalies
• The subtropical Jet stream is sensitive to
  changes in meridional temperature gradient that
  is induced by sea ice conditions
• Precipitation shows anomalies related with
  circulation that is in turn associated with SICA
  patterns.
• Opposite precipitation anomalies are usually
  associated with the direct and inverse modes
• During summer-autumn, SICA signals on conditions
  of atmospheric circulation and on South American
  precipitations are weaker than in winter-spring
  and depend on the prevailing pattern.

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• Thank you

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• Several authors relate ENSO cycle with Antarctic
  sea ice.
• Recently Yuan (2004) published a synthesis and
  mechanisms of ENSO-Sea Ice relation. In brief
• The Antarctic Dipole is characterized by an
  out-of-phase relationship between sea ice and
  surface temperature anomalies in the South
  Pacific and South Atlantic, manifesting itself
  and persisting 34 seasons after being triggered
  by the ENSO forcing.
• Warm ENSO events usually generate positive
  (warm) temperature anomalies and negative
  (reduced) sea ice anomalies in the Pacific centre
  of the ADP, but generate an opposite response in
  the Atlantic centre of the ADP.
• The ADP anomalies in the SAT, SST and SIC fields
  are fully developed, amplified and persist while
  the SST anomaly in the tropics is attenuated. The
  strongest anomalies in temperature and ice fields
  occur in the winter.
• EL NIÑO (LA NIÑA) mature phase preceded Amundsen
  negative (positive) SICA that prevalied during
  the following autumn-winter

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• El Niño mature phase (December 0 / April 1)
  1991/92 and 1997/98 SICA were negative over
  Amundsen Sea, which would agree with Yuan.
• However, SICA were positive during 1982/83,
  1986/87 and 1987/88 events.
• There was a shift from more to less sea ice in
  Amundsen sea in 1989/90 .
• SICA during El Niño events previous to 1989/90
  were opposite than those after
• Automn/winter (1) after 1986/87 and 1987/88
  summers SICA patterns changed to a dipolar
  pattern with negative SICA in Amundsen sea.
  1982/83 was an exception
• La Niña mature phase 1984/85 positive SICA in
  Amundsen, the same pattern than during El Niño
  1987/88 (3th PC inverse).
• Other La Niña had negative SICA conditions in
  Amundsen (6ºPC and 4º PC )
• During the following winter (1) for all La Niña
  events, SICA were positive in Amundsen Sea, at
  least for July, which would agree with Yuan.