Biogeosciences, 12, 5715-5734, 2015
https://doi.org/10.5194/bg-12-5715-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
08 Oct 2015
A latitudinally banded phytoplankton response to 21st century climate change in the Southern Ocean across the CMIP5 model suite
S. Leung1,2, A. Cabré2, and I. Marinov2 1School of Oceanography, University of Washington, Seattle, Washington, USA
2Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, Pennsylvania, USA
Abstract. Changes in Southern Ocean (SO) phytoplankton distributions with future warming have the potential to significantly alter nutrient and carbon cycles as well as higher trophic level productivity both locally and throughout the global ocean. Here we investigate the response of SO phytoplankton productivity and biomass to 21st century climate change across the CMIP5 Earth System Model suite. The models predict a zonally banded pattern of phytoplankton abundance and production changes within four regions: the subtropical (~ 30 to 40° S), transitional (~ 40 to 50° S), subpolar (~ 50 to 65° S) and Antarctic (south of ~ 65° S) bands. We find that shifts in bottom-up variables (nitrate, iron and light availability) drive changes in phytoplankton abundance and production on not only interannual, but also decadal and 100-year timescales – the timescales most relevant to climate change. Spatial patterns in the modelled mechanisms driving these biomass trends qualitatively agree with recent observations, though longer-term records are needed to separate the effects of climate change from those of interannual variability. Because much past observational work has focused on understanding the effects of the Southern Annular Mode (SAM) on biology, future work should attempt to quantify the precise influence of an increasingly positive SAM on SO biology within the CMIP5 models. Continued long-term in situ and satellite measurements of SO biology are clearly needed to confirm model findings.

Citation: Leung, S., Cabré, A., and Marinov, I.: A latitudinally banded phytoplankton response to 21st century climate change in the Southern Ocean across the CMIP5 model suite, Biogeosciences, 12, 5715-5734, https://doi.org/10.5194/bg-12-5715-2015, 2015.
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Short summary
Using the latest earth system models, we find that shifts in nutrient and light availability with future climate warming drive latitudinally banded changes in Southern Ocean phytoplankton distributions, which have the potential to significantly alter nutrient cycling as well as higher trophic level productivity throughout the global ocean. Spatial patterns in the modelled mechanisms driving these predicted phytoplankton trends qualitatively agree with recent observations.
Using the latest earth system models, we find that shifts in nutrient and light availability...
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