As you get near the ocean, the Alsek river flows into Alsek Lake.  Several large glaciers of the Fairweather Range calve icebergs into the lake.  We camped here two nights, and spent the day in between rowing out into the lake to check out the 'bergs.  There was frequent "thunder" from the other side of the lake, miles away, as new bergs were dropped into the water.  This iceberg is about the size of a football field.