Remove melted excess ice and set initiation for subsidence

Removes melted excess ice from the profile and also
set the initiation for subsidence calculations in
1989 (though this threshold should be replaced for
expanding beyond the N Slope of Alaska). Should check
melt profiles carefully as the layer structure may
be inverted.

components/elm/src/biogeophys/ActiveLayerMod.F90

@@ -189,15 +189,22 @@ subroutine alt_calc(num_soilc, filter_soilc, &
                melt_profile(j) = 0.0_r8
             else if (j .eq. k_frz) then
                melt_profile(j) = excess_ice(c,j) + ((z2-alt(c))/(z2-z1))*excess_ice(c,j+1) ! TODO: check indices here!!
+               ! remove melted excess ice:
+               excess_ice(c,j) = 0._r8
+               excess_ice(c,j+1) = excess_ice(c,j+1)*(1._r8 - min(1._r8,(z2-alt(c))/(z2-z1)))
             else
                melt_profile(j) = excess_ice(c,j)
+               ! remove melted excess ice
+               excess_ice(c,j) = 0._r8
             end if
             ! calculate subsidence at this layer:
             melt_profile(j) = melt_profile(j) * dzsoi(j)
          end do
 
          ! subsidence is integral of melt profile:
-         subsidence(c) = subsidence(c) + sum(melt_profile)
+         if ((year .ge. 1989) .and. (altmax_ever(c) .ge. altmax_1989(c))) then
+            subsidence(c) = subsidence(c) + sum(melt_profile)
+         end if
 
          ! limit subsidence to 0.4 m
          subsidence(c) = min(0.4_r8, subsidence(c))