Update README.md

pcmdi_metrics/sea_ice/README.md

@@ -62,6 +62,7 @@ A [demo parameter file](https://github.com/PCMDI/pcmdi_metrics/blob/405_sic_ao/p
 * **obs_area_template**: File path of grid area data. If unavailalbe, skip and use "obs_cell_area".
 * **obs_area_var**: Name of reference area variable, if available. If unavailable, skip and use "obs_cell_area".
 * **obs_cell_area**: For equal area grids, the area of a single grid cell in units of km2. Only required if obs area file is not available.
+* **pole**: Set the maximum latitude for the Central Arctic and Arctic regions to exclude ice over the pole. Default is 90.1 to include all ice.
 
 
 ## Reference