Ocean/ice stress from CICE

COSIMA
1

Hii, question for anyone here familiar with CICE.

I’m looking at the diagnostic ocean/ice stress, called strocnx_m. It is not clear to me whether

  • It is the stress the ocean feels due to ice or the stress the ice feels due to the ocean ;
  • Depending on the answer above, if it is the stress the ice feels, since it is a cell average, to convert it to the stress the ocean feels, do I need to weight by sea ice concentration?

I will be eternally grateful for any help !

2

We caught up in person, but for the future reader:

  • For a cice diagnostic of ocean/ice stress (strocn), it will be positive for “thrust” onto ice and negative for “drag” onto ice. For the mom diagnostic, it would be negative for “drag” onto the ocean, so sign should be reversed between ice and ocean diagnostic of the same stress term.
  • Ocean surface stress (typically tau) is a combination of ocean/ice stress and ocean/atmosphere stress. They are combined using sea ice concentration. Ocean surface stress should equal ocean/ice stress when sea ice concentration is 1. Sea ice concentration is a center point (T-cell) quantity, and stresses are corner point (U-cell) quantities. To combine the centre and corner point quantities, ocean/ice stress is interpolated onto the centre point before being combined with ocean/atm stress and then interpolated back to the corner point after being combined. All stress diagnostics are corner point quantities.
  • In the tripole region / north of 65°N, stresses are aligned with positive x/y on the grid, which are rotated from true north/east.
4

I was a little confused by this terminology, so I thought I’d clarify for other readers that the sign of the stress components is not dependent on whether it accelerates or decelerates an existing flow (of ice or water) in its existing direction of motion. So for example a “drag” may actually speed up the flow.