Since all Ice Barrier monsters are WATER monsters, you can use "A Legendary Ocean" to reduce your monsters Levels by 1, this will allow you to attack with Level 4 monsters as they will now be level 3.
In a tight pinch where your other Ice Barrier monsters are in danger of attack, use "Call of the Haunted" during your opponent's turn to revive "Cryomancer", who can hold off high-leveled attacks for a turn. Then dispose of him, either for tribute for a Tribute Summon or as Synchro Material, so that you may attack on your turn.
During the End Phase, Special Summon this card from your Graveyard with the effect of "General Gantala of the Ice Barrier" to prevent your opponent's monsters from attacking; then, in your turn, use this card for a Normal/Synchro Summon, and during the End Phase Special Summon it again. This way, you're gonna keep the control of the field and only your opponent will be unable to attack.