Krill Growth and Climate Change In The Presence of Internal Climate Variability In The Southern Ocean

Sylvester, Zephyr T

Graduate Thesis Or Dissertation

Krill Growth and Climate Change In The Presence of Internal Climate Variability In The Southern Ocean Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/vt150k28h

Abstract

Climate change is rapidly altering the habitat of the most abundant keystone species of the Southern Ocean food web, Antarctic krill (Euphausia superba). Krill support a growing commercial fishery, however, there remains limited understanding of how krill habitat is impacted by changing oceanic conditions. In addition to trends forced by global-scale, humandriven warming, the Southern Ocean is highly dynamic, displaying large fluctuations in surface climate on interannual to decadal timescales. The dual roles of forced climate change and natural variability affecting Antarctic krill productivity complicate interpretation of observed trends and contribute to uncertainty in future projections. This research uses the Community Earth System Model Large Ensemble (CESM-LE) coupled with an empirically-derived krill growth model to detect and attribute trends in krill growth to the forced trend of human-driven climate change superimposed on natural variability within the system. Our findings indicate that the forced trend in krill growth habitat is characterized by a poleward contraction of optimal krill growth conditions and an overall reduction in Southern Ocean krill habitat. However, the natural climate is dynamic, such that these trends cannot be formally distinguished from natural variability over much of the Southern Ocean by 2100. Our results illustrate how natural variability can strongly modulate regional trends in krill growth and can mask the forced trend from detection until late in the 21st century. This research demonstrates an approach for determining ecosystem impacts from climate change and variability that can be used to inform krill management in the Southern Ocean.

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