Adjoint Advances
story by Helen Hill
Two MITgcm adjoint activities are (i) the development of an open-source, extensible automatic differentiation tool, OpenAD and (ii) the configuration of an ~18km resolution global ocean and sea-ice experiment as part of the ECCO2 project.
The OpenAD project involves Jean Utke and Paul Hovland at Argonne National Laboratories and Chris Hill and Patrick Heimbach at MIT. It has reached the point where an adjoint of a full three-dimensional, global ocean MITgcm experiment can be automatically generated. The animated image to the left shows output from an experiment in which a cost function is defined as the integrated heat transport across 24°N in the Atlantic. The animation shows the sensitivity of that transport to ocean temperature at depth over the preceding 10 years. For more information on this work visit the OpenAD website – contact Chris Hill.
ECCO2 CS510 Adjoint
Sensitivity of model observation difference to SST over 16 months.
As part of the ECCO2 project Hong Zhang and Dimitris Menemenlis at JPL are working with Chris Hill, Patrick Heimbach and Gael Forget on an adjoint configuration of the ECCO2 cs510 cube-sphere simulation. The animation on the left shows the sensitivity to SST of the root-mean-square model data difference from a preliminary 16 month test. This gradient information is being used to guide an optimazation procedure that updates controls space fields of the simulaiton to fit the simulation trajectory to observations. You can read more about this project at the ECCO2 web-site – contact Chris Hill.