SO&P: Data for Deliverable 12
Simulated sea-level from GCM simulations

The following simulated sea level data sets have been diagnosed from the GCM experiments used within the SO&P project, and together they represent deliverable 12 of the project (see deliverables list).

• HadCM3
  
  
  • The reference for this data set is (see SO&P publications for reprints):
    • Gregory JM, Lowe JA and Tett SFB (2006) Simulated global-mean sea-level changes over the last half-millennium. Journal of Climate, in press.
    
    
  • Global-mean sea level diagnosed from ocean thermal expansion, the estimated contribution from melting of glaciers and small ice caps, and the sum of these two components are available on the SO&P HadCM3 model global-mean sea level data page.
    
    
  • Other large area averages of sea level are available on the SO&P HadCM3 model sea level time series and data page.
    
    
  • Spatial patterns of sea level diagnosed from 3D patterns of ocean temperature change are available on the SO&P HadCM3 model sea level patterns data pages for
    • the all simulation
    • the nat simulation
    • the control simulation
  • Note that these data represent only deviations from the global-mean sea level. The global-mean sea level must be added on to these deviations to get the patterns of total sea level change for HadCM3.
    
    
  • The following three figures show the zonally-average changes in sea level simulated by HadCM3 during the 'nat' and 'all' simulations, and the difference 'all' minus 'nat' shows an estimate of the anthropogenic component (though this estimate includes contributions of internal variability from both simulations, so is quite noisy).
    
    
    
    
    
    
  
  
  
• ECHO-G
  
  
  • The ECHO-G Erik simulation used within the SO&P project has proved difficult to use for analysing past sea level variations, for two reasons that are both related to the artificial drift (towards cooler conditions) that is present during this simulation due to starting from unrealistically warm initial conditions. More details about this drift are provided in:
    • Osborn TJ, Raper SCB and Briffa KR (2006) Simulated climate change during the last 1000 years: comparing the ECHO-G general circulation model with the MAGICC simple climate model. Climate Dynamics (doi:10.1007/s00382-006-0129-5).
    • See SO&P publications for reprints.
    
    
  • This drift is large in the interior ocean and dominates over changes in sea level related to ocean thermal expansion that are caused by the volcanic, solar and greenhouse gas forcings. So the thermal expansion component of sea level cannot be estimated reliably from this simulation.
    
    
  • Although this drift is smaller in the surface temperature, it is extremely large (especially for summer temperature) in a very small number of grid boxes in which snow dramatically accumulates during the simulation. But it is the summer temperature from these problem grid boxes that is needed for estimating the contribution of glacier and small ice caps to sea level variations, and so this component of sea level cannot be reliably estimated from this simulation either.
    
    
  • As a result of these problems, a decision was made to exclude the ECHO-G Erik simulation from the sea level workpackage of the SO&P project.