Climate-mediated changes to mixed-layer properties in the Southern Ocean: assessing the phytoplankton response

• Main Authors: Boyd, P. W., Doney, S. C., Strzepek, R., Dusenberry, J., Lindsay, K., Fung, I.
• Other Authors: NIWA Centre for Chemical and Physical Oceanography, Department of Chemistry, Department of Marine Chemistry and Geochemistry (WHOI), Woods Hole Oceanographic Institution (WHOI), Climate and Global Dynamics Division Boulder (CGD), National Center for Atmospheric Research Boulder (NCAR), Department of Earth and Planetary Science UC Berkeley (EPS), University of California Berkeley (UC Berkeley), University of California (UC)-University of California (UC)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2007
• Subjects: [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO]; [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph]; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Southern Ocean
• Online Access: https://hal.science/hal-00297943; https://hal.science/hal-00297943/document; https://hal.science/hal-00297943/file/bgd-4-4283-2007.pdf

International audience Concurrent changes in ocean chemical and physical properties influence phytoplankton dynamics via alterations in carbonate chemistry, nutrient and trace metal inventories and upper ocean light environment. Using a fully coupled, global carbon-climate model (Climate System Model 1.4-carbon), we quantify anthropogenic climate change relative to the background natural interannual variability for the Southern Ocean over the period 2000 and 2100. Model results are interpreted using our understanding of the environmental control of phytoplankton growth rates ? leading to two major findings. Firstly, comparison with results from phytoplankton perturbation experiments, in which environmental properties have been altered for key species (e.g., bloom formers), indicates that the predicted rates of change in oceanic properties over the next few decades are too subtle to be represented experimentally at present. Secondly, the rate of secular climate change will not exceed background natural variability, on seasonal to interannual time-scales, for at least several decades ? which may not provide the prevailing conditions of change, i.e. constancy, needed for phytoplankton adaptation. Taken together, the relatively subtle environmental changes, due to climate change, may result in adaptation by resident phytoplankton, but not for several decades due to the confounding effects of climate variability. This presents major challenges for the detection and attribution of climate change effects on Southern Ocean phytoplankton. We advocate the development of multi-faceted tests/metrics that will reflect the relative plasticity of different phytoplankton functional groups and/or species to respond to changing ocean conditions.