Option parallel_1d is automatically added to the option list in the run_mom_script if the number of processors is set greater than one. This option enforces a high level parallelism as described in Section 12. When option parallel_1d is enabled, the message passing toolkit ``mpt'' must be available on CRAY T90 platforms. All communication is in terms of Cray specific ``shmem'' calls because it is faster than MPI or PVM on Cray platforms. When executing on the CRAY T3E, option cray_t3e must be enabled.