Moore, S. E., NOAA/AFSC, Seattle, USA, sue.moore@noaa.gov
Overland, J. E., NOAA/PMEL, Seattle, USA, james.e.overland@noaa.gov

ARE GRAY WHALES AND WALRUS RESPONDING TO 'TIPPING POINTS' IN SEASONAL SEA ICE EXTENT?

Observations indicate that sea ice declines are influencing the phenology of gray whales and walruses in the western Arctic. A 17-fold reduction in gray whale sighting rate in the northern Bering Sea and acoustic evidence for whales over-wintering in the Beaufort Sea suggest that whales are foraging in the Chukchi/Beaufort and remaining there longer. For walrus, the retreat of sea ice rafts them beyond productive Chukchi shelf waters. Responses to ice edge retreats have included pup separation and the unprecedented occurrence of walrus hauling out on land along the northwestern Alaskan coast. Most IPCC AR4 climate models predict a >40 % loss of sea ice area by 2050 relative to 1979-1999. But in 2007, a convergence of natural climate influences created an Arctic sea ice area minimum which was 38 % below the 1979-2000 average. The major uncertainty is whether the present loss of sea ice will continue. That is, have we crossed a tipping point whereby eight years of warm conditions and reduced sea ice cover has altered western Arctic ecosystems sufficient to impact top predators.

Oral presentation

Presentation is given by student: No
Session #:034
Date: 03-04-2008
Time: 10:00