Ecological vs. climate uncertainty in future marine ecosystems: lessons learned from krill in a major upwelling region

Krill is a central organism in the food web of many marine ecosystems and
eastern boundary current upwelling regions specifically. Here, a
superensemble of climate and ecological models is used to determine
drivers of future change, variability, and uncertainty in krill abundance
for the California Current. While krill is projected to slowly decrease
throughout the 21st century, the long-term trend consistently exceeds
natural variability only under extreme warming. Similarly, unprecedented
low krill years are expected to progressively increase, but their
frequency of occurrence will depend on background abundances tied to
low-frequency climate variability. The relative contributions of warming
rate and model formulation to projected uncertainty are comparable and
reflect latitudinal changes in the magnitude of climate forcing and
availability of empirical data to parameterize krill models, thereby
warranting a more pragmatic incorporation of anthropogenic and ecological
uncertainty sources when projecting the fate of marine ecosystems in a
changing climate.