Southern Ocean phytoplankton dynamics and carbon export: insights from a seasonal cycle approach

Abstract

Quantifying the strength and efficiency of the Southern Ocean biological carbon pump (BCP) and its response to predicted changes in the Earth's climate is fundamental to our ability to predict long-term changes in the global carbon cycle and, by extension, the impact of continued anthropogenic perturbation of atmospheric CO 2 . There is little agreement, however, in climate model projections of the sensitivity of the Southern Ocean BCP to climate change, with a lack of consensus in even the direction of predicted change, highlighting a gap in our understanding of a major planetary carbon flux. In this review, we summarize relevant research that highlights the important role of fine-scale dynamics (both temporal and spatial) that link physical forcing mechanisms to biogeochemical responses that impact the characteristics of the seasonal cycle of phytoplankton and by extension the BCP. This approach highlights the potential for integrating autonomous and remote sensing observations of fine scale dynamics to derive regionally optimized biogeochemical parameterizations for Southern Ocean models. Ongoing development in both the observational and modelling fields will generate new insights into Southern Ocean ecosystem function for improved predictions of the sensitivity of the Southern Ocean BCP to climate change. This article is part of a discussion meeting issue 'Heat and carbon uptake in the Southern Ocean: the state of the art and future priorities'.

Carbon Cycle Response to Stratospheric Aerosol Injection With Multiple Temperature Stabilization Targets and Strategies

“…The simulation of the terrestrial carbon cycle here does not include the effect of nitrogen limitation, which would have important effect on the terrestrial carbon cycle response to increasing atmospheric CO 2 and SAI (Duan et al, 2020;Glienke et al, 2015;Tjiputra et al, 2016;Yang et al, 2020). In terms of the oceanic carbon cycle, the responses of marine ecosystem processes and effects on the ocean CO 2 uptake are of substantial uncertainty and merit further studies (Hauck et al, 2015;Moore et al, 2013;Thomalla et al, 2023). In this study, we define permafrost solely by near-surface active layer depth, and do not account for the changes in deep permafrost, which is resistant to surface temperature changes (Morrison et al, 2023).…”

Twenty-six years of phytoplankton pigments reveal a circumpolar Class Divide around the Southern Ocean

“…The majority (85%) of samples were collected in austral summer, primarily in January (56%). Therefore, we do not report on the seasonal dynamics of phytoplankton groups; although seasonal patterns and succession are important (Smith et al, 2014;Arteaga et al, 2020;Thomalla et al, 2023), they are smoothed by zonal averaging. The Antarctic Shelf region (referred as 'Shelf' from here on) was the most sampled, comprising 6,544 (44%) of total samples, largely due to sustained long-term research efforts in the Ross Sea and Western Antarctic Peninsula (WAP).…”

Heat and carbon uptake in the Southern Ocean: the state of the art and future priorities

“…As in the physical and biogeochemical circulation systems, autonomous instrumentation has provided new insights into the fine scale structures of the biological carbon pump, and Thomalla et al . [ 9 ] explore what the new resolution of seasonal timescales can reveal about the impact of climate change on this system.…”