ASIS:Nested

3rd party AMR code
We intend to use 3rd party nested grid code. Contenders are:


 * Paramesh
 * Chombo
 * AGRIF
 * SAMRAI

Desirable features of 3rd party code
1.	allows use of our existing fortran90 code with a minimum of changes;

2.	allows parallel computation on a Beowulf-type cluster;

3.	does not prevent inclusion into larger Earth-system model;

4.	able to cope with both implicit (e.g. velocity solver) and explicit (thickness solver) calculations;

5.	has flexibility in terms of which calculations are performed on the adaptive mesh and which are not; and

6.	is actively supported with a wide user base.

Comparison of 3rd party libraries
We have discarded AGRIF on the grounds that it has no parallel option (although its use would require a minimum of change to our fortran90 code)

Paramesh works on 'blocks' of higher resolution, and is designed with explicit schemes in mind. We may need to use multigrid techniques in order to efficiently solve our governing equations explicitly. We have discarded PARAMESH because of its restrictive grid structure (i.e., no clustering) that would make implicit calculation difficult (it is also currently unsupported).

We are currently installing CHOMBO. CHOMBO uses clustering to merge nests, hopefully to a size that will make implicit calculations valid. CHOMBO seems to be well supported with an active community.

We are currently installing SAMRAI. SAMRAI features clustering.

1D nested grid ice sheet model
RG is currently developing a 1D nested grid model, in which nests are continuous regions over which implicit solutions are calculated. It is intended to use this model to simulate grounding line migration.