adding a free surface (#307)

Author: simone-silvestri

src/DataWrangling/ECCO/ECCO_metadata.jl

@@ -168,6 +168,7 @@ ECCO4_short_names = Dict(
     :salinity              => "SALT",
     :u_velocity            => "EVEL",
     :v_velocity            => "NVEL",
+    :free_surface          => "SSH",
     :sea_ice_thickness     => "SIheff",
     :sea_ice_area_fraction => "SIarea",
     :net_heat_flux         => "oceQnet"
@@ -178,6 +179,7 @@ ECCO2_short_names = Dict(
     :salinity              => "SALT",
     :u_velocity            => "UVEL",
     :v_velocity            => "VVEL",
+    :free_surface          => "SSH",
     :sea_ice_thickness     => "SIheff",
     :sea_ice_area_fraction => "SIarea",
     :net_heat_flux         => "oceQnet"
@@ -186,6 +188,7 @@ ECCO2_short_names = Dict(
 ECCO_location = Dict(
     :temperature           => (Center, Center, Center),
     :salinity              => (Center, Center, Center),
+    :free_surface          => (Center, Center, Nothing),
     :sea_ice_thickness     => (Center, Center, Nothing),
     :sea_ice_area_fraction => (Center, Center, Nothing),
     :net_heat_flux         => (Center, Center, Nothing),