Unusual narwhal sea ice entrapments and delayed autumn freeze-up trends Laidre, Kristin ; Heide-Jørgensen, Mads Peter ; Stern, Harry ; Richard, Pierre Abstract Publication: Polar Biology Pub Date: January 2012 DOI: 10.1007/s00300-011-1036-8 Bibcode: 2012PoBio..35..149L