SOPHOCLES Update Bergen St Petersburg Meeting Summaries

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SOPHOCLES Update Bergen St Petersburg Meeting
Summaries

• Siobhan OFarrell, ACE CRC, CMAR,CAWCR, WFO

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SOPHOCLES AIMS

• How well do the models represent Southern ocean
  water masses, methods of formation/transformation,
  ocean mixing processes and dynamics of the major
  currents and thermohaline circulation?
• How can ice and ocean model parameterizations be
  improved to better represent the interaction
  between the ocean and the Southern Hemisphere
  cryosphere?
• How can we best use satellite observations and in
  situ data sets including those gathered during
  IPY and through SOOS to constrain the models?

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Scope of project-1

• To examine how well existing models (including
  IPCC-AR4, WGOMD-CORE, regional and global eddy
  permitting models) represent Cryospheric-ocean
  processes and broader Southern ocean processes,
  (eddies, down-slope flows convection, mixing
  etc).
• Identify gaps and the need for improved or new
  parameterizations of processes not included
  particularly interaction with the cavity under
  ice shelves and freshwater input from glacial ice
  sources, including icebergs.
• Verify how well the models perform against the
  best available data set, including satellite
  data, ARGO and SOOS, repeat WOCE lines, and IPY
  observational programmes of both the ice (ASPECT)
  and ocean (CASO-SOIP, SASSI-iAnzone)
  observational communities

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Scope of Project-2

• Test new parameterizations of sea ice, polynyas,
  ice shelf ocean fluxes and glacial fluxes in
  global ice-ocean models, devise experiments to
  study sensitivity to warmer climate conditions.
• Increase the number of regional models that
  include ice shelf cavities to study a range of
  processes both within the cavity and the exchange
  with open ocean. Examine the sensitivity to
  warmer climate conditions.
• Build these new parameterizations into the
  ocean/ice components of climate simulations
  (include as many international groups that can be
  persuaded to participate), undertake 20th Century
  and 21st century scenario runs.

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Observed and Model Simulated AAIW Salinity
minimum layer in Eastern Indian Ocean (100oE)
Observed depth and latitude extent of AAIW
salinity (psu) minimum is overlain on model
salinity distribution. Potential density black
contours.
SloyanKamenkovich 2007
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March
September
Number of IPCC AR4 models with gt15 sea ice
(1980-99) vs obs (HadISST) Adapted from Arzel
(2006).
Improving sea ice formulations, but only modest
progress in simulations of observed sea-ice since
the TAR caused by biases in atmosphere and ocean
model.
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Salinity Errorat 30W
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Polynya process, role in bottom water formation
OBS Formation and
Export of Dense Shelf Water
from the Adelie Depression,
East Antarctica
Williams et
al, JGR, 2007 MODELS
Antarctic Coastal Polynya Response to Climate
Change
Marsland et al., JGR,
2007
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Iceberg drift patterns ( AWI)
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Calving at the ice fronts represents the main
mass loss of the Antarctic ice sheet

• Calving 2020 Gt/a gt 75 mSv
• Basal Melting 550 Gt/a gt 17 mSv
• 910 Gt/a gt 28 mSv
• In Weddell Sea 410 Gt/a gt 15 mSv

(Gladstone et al. 2001)?

• NCEP Precipitation 39 mSv (12 mSv)?
• 2.7 x 106 km2 circumpolar continental shelf

These estimates were Before Rignot et al (2008)
estimate who put basal melting and calving 50/50
Melting icebergs provide cold freshwater during
drift and final decay, GFDL and NCAR are now
testing code to account for drifting icebergs in
GCMs
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(Schodlok)
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Impact of ice shelves on sea ice extent, blue
with ice shelves, red without ice shelves
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Ben Galton-Fenzi
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Three proposed COREs

• CORE-I 500 year spin-up with repeating Normal
  Year Forcing (NYF) (Griffies et al 2008).
• CORE-II 50 year retrospective with interannually
  varying forcing (details of design under
  investigation by WGOMD and collaborators).
• CORE-III Fresh water melt perturbation
  idealizing the melt of water around Greenland

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Weddell Sea September 1999
KAB036 mixed layer depth
KAB036 ice concentration
KAB042 mixed layer depth
KAB036 ice-ocean heat flux
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Interannual variability in Salinity for KAB042
run at 100m depth, September case, Ross Sea and
Adelie coastline
1997
1998
1999
2000
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Zonal averaged conditions in Weddell Sea 25 years
in AusCOM simulation.
TempMar
Temp Sep
Salinity Mar
Salinity Sep
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Experiments where the momentum flux is affected
by local sea ice area and sub-grid scale effects.
Figures show differences to reference experiment
over Weddell Sea.
Local Richardson number
Wind stress
Ice velocity
Ice thickness
Ice concentration
Sensible heat flux
Stossel et al, 2008
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• Antarctic sea ice-ocean modelling
• in Belgium
• Martin VancoppenolleUCL Louvain-la-Neuve
• Coll. Hugues Goosse, Anne de Montéty, Thierry
  Fichefet, Sylvain Bouillon, Chris König Beatty

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Ice thickness
September
model - clim
obs from Worby et al. (2008)
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Ice salinity
march
september

• Accounting for ice salinity variations ...
• Increases sea ice volume by 10-20
• Induces more ice formation with less salt
  rejection
• Reduces vertical mixing in the upper ocean
• Reduces the oceanic heat flux
• Increases sea ice formation

obs include various sources from Worby, Lytle,
Perovich, Jeffries, Gow, Eicken, Tison, Hellmer
coauthors
Vancoppenolle et al., 2008b
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LIM Model issues

• Difficult at this stage to say which part of the
  model is wrong
• Model physics ?
• Ice growth frazil, pancakes, snow ice, flooding
  
• Deformation
• Ocean heat input ?
• Forcing (wind)
• Need for longer / more comprehensive data sets
• Ice thickness
• Ice deformation
• Forcing (winds, temperatures, snowfall, clouds,
  radiation, humidity, ...)
• Process studies (frazil, pancake, snow ice
  growth, flooding, tides, ocean heat input...)
• High interannual variability .vs. Short
  validation time series

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OPEN QUESTIONS

• Lead and polynya processes
• Ice shelf cavities
• Circulation of icebergs
• Fresh-water budget, runoff
• Over-flows
• How does resolution impact on water mass formation

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Modelling Activities

• Continue to develop the next generation of high
  resolution ice-ocean Southern Ocean model (mostly
  in specialized Antarctic Southern ocean groups)
• Develop a standard set of metrics for models in
  order to evaluate processes - formation rates of
  water masses, positions of major fronts, water
  mass characteristics in regional and global
  models. Develop metrics to assess/validate
  ice-shelf circulation models.
• Examine a subset (5-10) IPCC AR4 models in the
  Southern Ocean using some of the basic statistics
  in Russell et al. 2006 and other studies out of
  the 24 models in PCMDI repository.
• Conduct wide spread diagnostics of water mass
  transformation rates / water mass pathways
  obtain a detailed understanding of the model
  processes in the Southern Ocean.
• Work with WGOMD to develop improved approaches
  for CORE-II experiments based on analysis of
  existing CORE-II experiments to improve results
  in the Southern Ocean.
• Compile a list of available models, detailing
  resolutions, forcing (interannual etc) contact
  details and www links for Southern Ocean region.

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Fill Gaps in model representation of
Cryosphere-Ocean Interaction

• Discuss with other groups (e.g. FRISP, CliC Theme
  2 and 3, US Ice sheet Community ) and research
  institutes ways to improve the representation of
  ice shelves, icebergs in ocean models, and
  mechanisms. (There is a need for better initial
  conditions in the cavities, e.g. sub cavity
  hydrography, topography, etc? There already is
  expertise in ice-shelf ocean interaction/dynamics
  within the SOPHOCLES group though there is a need
  to engage with others within FRISP).
• Use high resolution ice shelf cavity models to
  calibrate ice shelf cavities that may be included
  at climate resolution (1o) as at climate
  resolution any cavity will not fully resolve the
  detailed processes.
• Undertake sensitivity experiments in regional or
  global models of the glacial and ice shelf FW
  fluxes and response to warming climate.
• Consider how polynyas can be more realistically
  parameterized so that their effects can be
  included in climate models, also improve the
  micro-physics in the sea ice for Antarctic
  conditions.
• Include the FW flux of melting icebergs along
  observed drift routes, as far north as ACC.
  Consider role of FW flux from runoff from coast
  and local melting of glaciers/under ice shelves.
  Rely on statistics from satellite data to
  determine both fluxes and the new GFDL and CICE
  schemes.

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Links to Observations/SOOS

• Extend time series of bottom pressure sensors
  and moorings in Drake Passage, continue repeat
  sections at inflow and outflow regions of Weddell
  and Ross Seas, continue repeat sections on
  continental shelf/slope and extend WOCE lines on
  to shelf and into sea ice
• Consolidation of ocean data sets around
  ice-sheets and shelves to monitor freshening in
  deep ocean
• Encourage SOOS and National programmes to
  increase ice shelf cavity measurements for
  mixing, circulation, and thermodynamic quantities
  and ocean measurements adjacent to ice-shelf
  regions to test against models.

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Follow up issues

• No access to WGOMD-CORE1 runs, Repeat annual
  cycle runs the models were not intended for
  public use, the project was more proof of
  concept.
• They encourage active participation to CORE2,
  have strong links with tropical modelling
  group(s), 40 years however is not long enough for
  high latitude watermass studies inter-annual
  forcing needs to be repeated many times over.
• New CORE2 data released by Large and Yeager
  available from GFDL website.
• Discussions with Adrian Jenkins (re FRISP), he
  sees SOPHOCLES focusing on integration the
  ice-shelf ocean circulation into the large scale
  climate and regional models, whilst they focus
  more on the cavity modelling and observations
• Links to ecosystem/biogeochemical modelling
  groups, SOPHOCLES focus is on the physical
  process but the outcomes are needed by other
  groups. Joellen Russell involved closely, I have
  had contacts with ICED and a suggestion from
  Eileen Hoffman at the CCAMLR/IWC suggest a joint
  meeting with this community in the next couple of
  years.