You can go to Aleroth and return to the fjords (using the zeppelin, dragon stone, or by the teleporter shrines in the marketplace or ministry).
Unfortunately, once you get the battle tower, you can no longer finish most quests in Broken Valley or Sentinel Island (you can still enter the quarry tower in Broken Valley, and find the boat in a tree around Sentinel Island, though you may want to use the item yourself, rather than turn in the quest), and most NPCs will be unavailable.
If you have a save before entering the summoning chamber (where Talana gave a warning about proceeding) you can reload, and make sure you finish everything else first (though you've already done a fair bit in the fjords, so it may not be worth it).