Science questions

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Science questions

• How is the extent, thickness and volume of
  Antarctic sea ice and snow cover changing?
• What are the subsequent impacts on ocean
  circulation and properties?
• What is the feedback to surface energy balance
  and atmospheric circulation?
• What are the impacts on sea ice biomass (due to
  changes in light penetration etc.) and impacts on
  other parts of the SO ecosystem (krill ecology,
  top predator behaviour, etc.)?
• Provision of adequate input to sea ice
  forecasting and climate models?

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CCSM3 sea ice trends, 1900-2100

• Historical forcing for 20th century
• Scenario A1B in 21st century (business as usual)
• Downward trend in Antarctic area and volume from
  1960
• Fastest retreat and thinning in Weddell Sea

Annual average ice area (km2)
Annual average ice volume (m3)
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Sea ice parameters for SOOS

• Ice extent and concentration
• Ice thickness (combined give ice volume)
• Snow cover thickness
• Ice properties (in situ measurements)
• Ice drift (tidal/inertial forcing)
• Distribution/abundance of ice algae
• Process studies very important (flooding,
  microstructure, percolation/convection, wave-ice
  interaction, incorporation of ice algae, Fe,
  etc.)
• Couple with oceanography moorings/CTDs/ARGO/seal
  sensors etc.

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Ice Extent and Concentration

• Daily global coverage from passive microwave
• SOOS should strongly articulate the need for
  continuity of PM sensors
• Reanalysis/reprocessing of PM data needs to be
  done, with rigorous evaluation of available
  algorithms (IGOS-Cryo report).
• Proxies for historical sea ice extent
  (continential ice cores, whale catch data).role
  for SOOS in data recovery?

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Ice and snow thickness

• Ship observations and ice charts
• EM (ship-based and airborne)
• Upward-looking sonar (moorings AUVs)
• In situ measurements
• Altimetry (satellite and aircraft)

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Tracks of 83 ASPeCt voyages 1980 - 2005
Worby et al. JGR, 2008
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2.5 deg latitude 5 deg longitude
Worby et al. JGR, 2008
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Ross Sea structureJanuary 1999
c
b
a
a
c
b
Decorrelation length scale ha 180 km hb
250 km hc 80 km
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US National Ice Centre Ice Charts

• Routine weekly ice charts since the 1970s
• Trained ice analysts discern sea ice
  concentration and during 1995-2000 stage of
  development using a host of available satellite
  data
• Show average ice conditions integrated over 3-5
  day period.
• Represent the only continental scale estimates of
  ice type

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ICECAM - Concept
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IceCam

• An automated system for
• Sea ice observing
• Environmental data logging
• Supplements/quantifies the traditional ice log
• Deployable on Ships-Of-Opportunity (SOO)
• Side-, forward-, and down-looking systems
• Developed by Nick Hughes and Richard Hall, but
  both have subsequently moved jobs.

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Sea Ice and Snow Cover Thickness from Remotely
Sensed Techniques

• EM, radar and laser techniques each have their
  shortcomings
• Knowledge of ice and snow properties is essential

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250 km
Envisat SAR
EM data from Weddell Sea. Courtesy C. Haas
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ULS measurement sites around Antarctica
AWI instruments on top of oceanographic
moorings, at depths of 120-180m Along 0deg, data
since 1996 Interannual, decadal and climatic
variabilility in sea ice thickness
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Autonomous Underwater Vehicles

• Specifications
• Autosub built and operated by National
  Oceanography Centre, UK.
• 7 m long,
• 3.6 tonne
• powered by 500 kg of primary manganese alkaline
  batteries,
• range of 300 km at a speed of 1.8 m s-1.
• depth limit 1600 m.
• The navigation system relied on a Doppler sonar
  system, able to track the seabed at ranges of up
  to 500 m, and an Ixeas-Oceano PHINS, a fibre
  optic gyro -based inertia navigation system,
  positional accuracies of 0.1 of distance
  travelled.

• Scientific Payload
• Dual conductivity, temperature and depth (SBE-911
  CTD)
• Dissolved oxygen sensor (SBE-43)
• Upward (300kHz) and downward (150 kHz) looking RD
  Instruments Acoustic Doppler Current Profilers
• Simrad EM-2000 swath multibeam bathymetric
  mapping system was mounted looking upwards

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Autosub draft PDF
Courtesy Mark Brandon
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Under ice data
SEA ICE
Krill swarms
Brierley, Fernandes, Brandon Science, 2002.
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Measurements of under-ice hyperspectral
irradiance to estimate ice algal biomass
?2 (nm)
Correlation coefficient
Normalised difference index NDIT(?1)-T(?2)/
T(?1)T(?2) (Mundy et al. 2007)
?1 (nm)
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• Illustrates 2 cm range precision of ICESat.
• 2 cm precision is important, because mean
  freeboard is about 30 cm.
• Footprint spacing is 170 m.

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Ron Kwok, JPL
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Laser over the Dalton Iceberg Tonguesurface
elevation m
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Ice drift

• Lagrangian buoys with GPS position
• Pressure/temperature sensors
• Enhanced network, routine deployments (IPAB)
• Fill gaps, particularly in WAP, Ross Sea
• Develop an ice buoy that becomes an ARGO float
  when the ice melts
• More sopisticated versions might include
• Thermistor strings through the ice
• Mass balance
• Radiometer
• Wind

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Antarctic Fast Ice Network (AFIN)

• Observed parameters
• - Fast-ice thickness
• - Snow thickness
• - Freeboard
• - Dates of ice formation and breakout
• Observational methods
• - In situ weekly observations
• - Weekly observations using electro-magnetic
  induction device
• - Autonomous observatories
• - Chain of thermistors (high-resolution)
• - Acoustic pingers ice-air interface
  ocean-ice interface
• - Data logger or remote data uplink to
  satellite.
• - PLUS visual observations during transition
  intervals.

• Current participants
• - Australia (Petra Heil, Rob Massom)
• - France (Catherine Gobin)
• - Germany (TBA after C. Haas' departure)
• - Japan (Shuki Ushio)
• New Zealand (Tim Haskell, Pat Langhorne,
• Joe Troedahl)
• - Norway (Sebastian Gerland)
• - Russia (Andrey Korotkov)

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http//data.aad.gov.au/aadc/seaice
Historical data mining and recovery
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10-20 year plan

• A lot depends on how satellite altimetry
  develops..
• Repeat transects along lines of longitude at
  30-60 degree spacing
• AUVs with sub-surface docking stations (less ship
  time)
• Airborne surveys (EM, laser/radar altimetry,
  UAVs)
• Biomass from under-ice irradiance
• Identify lead agencies for coordinating data
  analysis/archival of different data sets (AWI for
  ULS, AAD for laser altimetry, ?? for AUV etc.)
• Process studies
• Satellite validation
• Small-scale processes (phys/biol/biogeochem)
• Development of agreed protocols where they are
  not already in place (sea ice community lags
  other disciplines)
• Network of integrated fast ice mass balance
  stations
• Ice growth/snow accumulation/radiometer for
  biomass
• Development of micro nitrate/fluorometer sensors
• Enhanced network of Lagrangian drifters, annual
  deployments
• Ice buoys that turn into ARGO floats when the ice
  melts?

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• Possible measurements
• ULS moorings
• AUV transects
• Ship observations
• Aircraft observations
• Layered observations
• Process studies

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Current AADC entries

• Country/ship Ice stations Ice
  cores Transects Snowpits
• Australia
• 1991 Aurora (V1) 11 18 15
• 1991 Aurora (V2) 3 4
• 1992 Aurora (V1) 18 29 3 8
• 1993 Aurora (V9) 23 45 8 17
• 1994 Aurora (V1) 30 36 5 27
• 2003 Aurora (ARISE) 12 27 14 48
• Germany
• 1986 P/stern (WWSP 86 Leg 1) 47 143
• 1988 P/stern (EPOS) 37 29 18
• 1989 P/stern (WWGS 89) 31 78
• 1992 P/stern (WWGS 92) 39 33 24
• Japan
• 1985-88 Syowa station 30 30
• 1990-92 Syowa station 21 21