Geo-clustering using SQL Server 2012 Enterprise with AlwaysOn
You are essentially trying to create a DR node. Availability Groups in SQL Server 2012 and above supports this scenario. Your node has to be part of the same windows cluster. The SQL Server instance on the secondary site can be configured as a secondary replica for the existing availability group. Once that is done, you will be able to sync changes from primary replica to the secondary replica. Your scenario is documented here: https://msdn.microsoft.com/library/hh781257.aspx