Primary production response to seasonal-scale extremes in the Bering Sea simulated by the Community Earth System Model, version 1

Abstract

The biological response to long-term trends and the co-occurrence of seasonal extremes of the physical environment and primary production in the eastern Bering Sea, as simulated by the Community Earth System Model (CESM1), are presented. This analysis covers the late-twentieth century (1950–2005) and focuses on critical drivers of the eastern Bering Sea ecosystem, including air temperature, sea ice area, wind mixing, and mixed layer depth. Primary production showed strong linear relationships to both air temperature and sea ice area during winter and spring. The only season that had a positive linear correspondence between wind mixing and primary production was summer. Over the fifty-five year period the CESM1 simulates a trend toward warmer air temperatures and a subsequent reduction in sea ice for every season; however, no trends were seen in seasonally averaged wind mixing or mixed layer depth. Corresponding to the air temperature increase was an increase in occurrence of positive seasonal extremes in primary production, as well as a reduction in negative production extremes. There were some instances of seasonal production extremes coinciding with seasonal extremes in the physical environment; however, neither these co-occurrences, nor the direction of the biological response to the physics, were robust throughout the study period.