STABILITY OF THE SOUTHERN OCEAN THERMOHALINE CIRCULATION

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STABILITY OF THE SOUTHERN OCEAN THERMOHALINE
CIRCULATION

• Simon Marsland
• CSIRO Complex Systems Science
• Southern Ocean Postdoctoral Fellow
• CSIRO Marine Research
• CSS Workshop, Coffs Harbour, 10-12August 2004

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STABILITY OF THE SOUTHERN OCEAN THERMOHALINE
CIRCULATION

• Simon Marsland
• CSIRO Complex Systems Science
• Southern Ocean Postdoctoral Fellow
• CSIRO Marine Research
• CSS Workshop, Coffs Harbour, 10-12August 2004

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STABILITY OF THE SOUTHERN OCEAN THERMOHALINE
CIRCULATION

• Simon Marsland
• CSIRO Complex Systems Science
• Southern Ocean Postdoctoral Fellow
• CSIRO Marine Research
• CSS Workshop, Coffs Harbour, 10-12 August 2004

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A hemispherocentric viewWhere are the Southern
Ocean formation sites?
Schmidt, 1995
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THERMOHALINE CIRCULATION AND GLOBAL
WARMINGSHUTDOWN OF DEEP OVERTURNING?
IMPLICATIONS CHANGES TO CIRCULATION
PATTERNS CHANGES TO CLIMATE
CHANGES TO UPTAKE OF
ATMOSPHERIC CO2
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A collapse in the ocean overturning circulation
would be a first order change in the climate
system
Hirst and OFarrell, CSIRO Atmosphere
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VARIOUS CLIMATE STATES IN RESPONSE TO SURFACE
FORCING GLACIAL CYCLES?
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DEEP WATER FORMATION SITES
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CENSUS OF GLOBAL OCEAN BELOW ZERO CELSIUS
UP TO 25 FROM AUSTRALIAN ANTARCTIC BASIN Q?
WHERE IS THE DEEP WATER FORMED
Rintoul, Antarctic Res, Ser.,75, 1998
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COASTAL POLYNYAS
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COASTAL POLYNYAS
Massom et al., Annals of Glaciol, 33, 391-398,
2001
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Mertz Polynya global ocean/sea ice model

• Max Planck Institute Ocean Model
• Marsland et al, Ocean Modelling, 5, 91-127, 2003
• horizontal 150x130 curvilinear orthogonal grid
• vertical 31 levels, 8 in upper 200 m
• timestep 300 seconds
• approx. 1 model year per week on 4 cpus (SGI
  Origin)
• 20 year spin-up with OMIP (ECMWF) climatology
• 1990-2000 variability run with NCEP-NCAR daily
  forcing
• 1996-99 sensitivity runs with perturbed
  heat/freshwater forcing

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MertzHOPE spatial discretisation
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Marsland et al., J. Geophys. Res (Oceans), in
press, 2004.
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Marsland et al., J. Geophys. Res (Oceans), in
press, 2004.
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SOUTHERN HEMISPHERE SEA ICE SENSITIVITYTO
SURFACE AIR TEMPERATURE
AREA (x106 km2)
VOLUME (x1012 m3)
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SOUTHERN HEMISPHERE SEA ICE SENSITIVITYTO
PRECIPITATION
AREA (x106 km2)
VOLUME (x1012 m3)
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• Predicted that both air temperature and
  precipitation will increase under global warming
  scenario
• Ice decreases with increasing air temperature
• Ice increases with increasing precipitation
• Partially compensating (Marsland and Wolff, JGR,
  2001)
• What about the polynya effect??
• Small spatial scales currently unresolved by
  global models

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POLYNYA DENSE WATER FORMATIONSENSITIVITY TO
CLIMATE CHANGE

• STRONG FORMATION PHASE
• WEAK RESPONSE TO TEMPERATURE
• NO RESPONSE TO PRECIPITATION
• WEAK FORMATION PHASE
• STRONG REPONSE TO TEMPERATURE
• WEAK RESPONSE TO PRECIPITATION
• CONCLUSION BREAKDOWN IN THERMOHALINE CIRCULATION
  SEEN IN OCEAN/ICE/ATMOSPHERE GENERAL CIRCULATION
  MODELS WILL BE AMPLIFIED AS THE MODEL RESOLUTION
  BECOMES SUFFICIENT TO RESOLVE THE COASTAL
  POLYNYAS (APPROX 2010)
• MANUSCRIPT IN PREPARATION

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COMPLEX SYSTEMS?

• MEME BOTTOM WATER SOURCE IS COASTAL POLYNYAS
• ASSUME CONTINUOUS SPACE/TIME AND THEN MODEL
  DISCRETELY
• WHAT EMERGES? SHUTDOWN IN THERMOHALINE
  CIRCULATION
• AMPLIFIED UNDER GLOBAL WARMING
• WHEN SMALL SPATIAL SCALES
  CONSIDERED
• HUMAN/LANDSCAPE INTERACTION???

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To survive they ate in December the remaining
dogs. This caused the death of Xavier Mertz. On
1 January 1913 he started to suffer from heavy
stomach aches. The following days his situation
got worse and on 7 January he died. Now Mawson
was all alone.
www.70south.com/resources/history/
chapters/chapter17
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P.J. ORourke, Eat the Rich
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Schmidt, 1995
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THREE BODY PROBLEM?
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WITH THANKS TO

• John Church, Steve Rintoul
• CSIRO Marine Research
• Nathan Bindoff, Guy Williams, Bill Budd, Matt
  Paget
• Antarctic Climate and Ecosystems
  Cooperative Research Centre
• Mojib Latif, Helmuth Haak, Johaan Jungclaus
• Max Planck Institute for Meteorology
• Tony Hirst, Siobhan OFarrell
• CSIRO Atmospheric Research