“Ocean warming may well turn out to be the greatest hidden challenge of our generation”. – Explaining Ocean Warming, ICUN 2016

The world’s oceans are getting warmer. The recent increase of ocean temperatures is the greatest that has occurred in the past 1000 years, and the ocean off the coast of Alaska has warmed far more rapidly than other areas. Warming of the upper ocean is reducing its biological productivity, affecting the food web and resulting in changes in fisheries and other important human activities dependent on ocean productivity (adapted from Chavez et al. 2011).  Models project that continued ocean warming will reduce the abundance of Pollock, the most commercially valuable fish stock in the Bering Sea, by 32–58% (Mueter et al. 2011) and reduce the health of juvenile sockeye salmon, potentially resulting in decreased overwinter survival (Farley et al. 2005).

The Importance of Being Warm Or Cold

“Over the next several decades, climate models predict that the southern Bering Sea will more frequently experience warm years with reduced sea ice. In the warmer southern waters, scientists observed a sharp decrease in the availability of key prey for young of-the-year pollock, including krill and large copepods. The reduced numbers these prey limited the survival of fish during their first winter, and multiple consecutive warm years ultimately resulted in low recruitment to adult pollock populations.” (Hunt et al. 2011).

How are Other Ocean Characteristics Changing?

Changes in Ocean Salinity? Recent data show that Alaska’s ocean waters are getting less salty due to increased rainfall instead of snow in some regions, melting glaciers and sea ice, and changes in freshwater input from rivers.  Changes in salinity – in particular a layer of fresh water at the mouth of streams, may delay or otherwise alter normal passage of salmon from ocean into streams.

Changes in Storm Intensity?

A number of researchers have investigated trends in storm intensity in the Bering Sea.  While there is no doubt that increasing open water, due to declining sea ice, is creating waves with greater intensity and frequency, it is less clear that storm intensity has increased.  “Multiple lines of investigation suggest that there has been no statistically change in autumn Bering Sea storminess or intensity, at least since mid-20th century. (Rick Thoman, Climate Science and Services Manager, Environmental and Scientific Services Division, National Weather Service Alaska Region.).  In contrast, local observers believe storms and winds are changing, in particular, noting more regular and intense fall storms. In the future researchers and their models are showing increasing frequencies of extreme storms and related winds.