Sea ice volume, 10 13 m 3
description
Transcript of Sea ice volume, 10 13 m 3
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High resolution modelling of the decreasing Arctic sea ice
Kristine S. Madsen, T.A.S. Rasmussen, J. Blüthgen and M.H. RibergaardPolar Oceanography, Danish Meteorological Institute
Sea ice volume, 1013 m3 Oil drift 17 days after initial spill
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Overview
Model introduction
Sea ice changes– Extend– Volume– Ocean surface temperature
Oil drift modelling– Surface spill– Deep spill– Importance of sea ice
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HYCOM/CICE ocean and sea ice model
• North Atlantic and Arctic oceans
• ~10 km horizontal resolution
• Sea ice: dynamic and thermodynamic
• Ocean: hydrodynamic, 29 vertical levels (hybrid)
• ERA Interim atm. forcing, 2000–2009
• Assimilate sea ice concentration and SST from satellite once a day, nudge towards climatological SSS
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The CICE model
• Hibler-type elastic-viscous-plastic ice model
• Each grid cell has 5 ice thickness categories with 4 vertical layers for each, plus surface snow
• Horizontal resolution and time step same as ocean model (~10 km, 5 minutes)
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Sea ice concentration
Sea ice area (concentration ≥ 30%), 1012 m2
Model Observations
Source: ocean.dmi.dk/arctic
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Sea ice concentration
2001 2007
Units: %
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Sea ice concentrations – September 1O
bse
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Mo
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Source (observations):U. of Illinois
The Cryosphere Today
Units: %
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Sea ice thickness – September 1
2001 2007
Units: m
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Sea ice volume
Units: 1013 m3
Model
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Ocean surface layer temperatureAverage for all ocean points north of 80°N, units °C
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Ocean surface layer temperatureAverage for ocean points w. at least 30% ice, north of 80°N, units °C
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Summary – sea ice
• The model reproduces concentration (within 10%) and timing of min and max sea ice concentration, but builds up ice too fast in the fall.
• The interannual variability is well represented.• Sea ice volume shows continuous build-up from October
to May and strong decrease in June.• 2007 shows large volume decrease and export along
Greenland’s east coast. 2008 and 2009 has lower ice volume than 2007.
• Summer polar ocean surface layer temperature is increased in summer 2007, also underneath the sea ice.
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Oil drift modeling
Existing hydrocarbon exploration & exploitation licences
Applications for new licences 2012/13
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DMI oil drift module
• Purposes: oil combating, “find the sinner”, drifting vessel, man overboard
• Particle model• Passive advection with ocean current• … and additional surface wind drift (3%)• Wind speed is scaled inverse linear with sea ice concentration.• Future work: Ocean speed is scaled inverse linear with sea ice
concentration towards ice velocity.• Buoyant rising (or sinking)• Downward mixing by wind waves (scaled by wind speed + random
distribution)• Turbulent spreading (random walk scaled by current speed)• Oil weathering• 8 pre-defined oil-types - based on fractions of 8 hydrocarbons• Instantaneous or continuous oil spill at any depth• Runs operationally, 15 minutes response 24-7
http://www.itopf.com
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Example of oil driftImaginary surface spill on
August 1-10 2003 south-east of Greenland
2 deg ~200 km
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Oil drift in sea ice affected areas
• Wind drag limited (already included in model)• Oil will partly drift with the ice• Oil will be trapped in pockets under the ice or freeze into
the ice – reducing weathering
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Thank you!
Sea ice volume, 1013 m3 Oil drift 17 days after initial spill