E3SM v1.2.0

v1.2.0 used for v1 Cryosphere Science Campaign

This release is on the maint-1.2 branch which was branched from master
on Feb 25, 2019 (7a3e32d), and is the code base for the Cryosphere Science Campaign
v1 simulations. This includes modified v1 versions of the atmosphere (EAM), land model (ELM),
ocean (MPAS-Ocean), sea ice (MPAS-Seaice), and land ice (MALI). A key feature of the E3SM v1
Cryosphere simulations is the inclusion of Antarctic ice shelf cavities in the ocean domain.
This allows the calculation of ice shelf basal melt rates, with a static ice shelf geometry.
Another distinction between standard E3SM configurations and Cryosphere configurations is
the inclusion of prescribed iceberg fluxes (using gridded monthly climatology data from
Merino et al 2016). To account for the explicit representation of Antarctic mass fluxes to
the ocean through prognostic basal melting and prescribed icebergs, standard representations
of runoff from Antarctica, both solid and liquid, are disabled.

Differences from v1.0 DECK simulations include all of those listed in the v1.1.0-beta tag.
Additional differences from the v1.1 BGC simulations are listed in the v1.2.0-beta tag.