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Seminar talk: The impact of anthropogenic forcing on the Southern Ocean CO2 sink

On June 13 Precious Mongwe will give a seminar talk at BCCR

Portrett av Precious Mongwe
Precious Mongwe

Short biography:

Researcher at CSIR. I am interested in ocean biogeochemistry, mainly working on the ocean carbon cycle and ocean deoxygenation. Seeking to understand processes that regulate the ocean carbon cycle, the impact of climate change on the ocean CO2 sink and its implications to the biosphere. I recently started working on ocean deoxygenation within the context of marine ecosystems using metabolic theory. I use ocean circulation models and Earth system models as the main tools to study the earth system.



The Southern Ocean (South of 30oS) takes up over 40% of the global ocean anthropogenic carbon dioxide (CO2) and about 75% of heat; it plays a crucial role in slowing down the rate of climate change. The business-as-usual climate scenario projects a warmer climate, higher atmospheric CO2 concentrations, and weakened ocean’s CO2 buffering capacity by the end of the century. In this study, we use seven earth system models (ESMs) to investigate the long-term impact of these changes on the Southern Ocean CO2 sink. We use the socioeconomic pathway 585 (SSP585) climate scenario from the climate model intercomparison project version 6 (CMIP6). We find the net CO2 sink change is almost double in the Antarctic region (south of the polar front) with respect to the Sub-Antarctic region (between the polar front and subtropical front) and Subtropical region (north of the subtropical front and south of 30oS). Warming-driven sea-ice melting enhances SST seasonal amplitudes and shoals the mixed layer depths, which leads to a stronger solubility-driven winter CO2 uptake in the Antarctic region. Consistent with previous studies, we find that decreased CO2 buffering capacity enhances the Southern Ocean biological CO2 uptake in the summer-spring seasons in the future. North of the subtropical front, the net CO2 sink change is relatively modest. CO2 seasonality is primarily regulated by temperature-driven solubility north of the subtropical front, and thus CO2 uptake during cooler seasons (winter-autumn) is almost compensated by weakened CO2 solubility in the warmer seasons (summer-spring). We find that ESM simulated CO2 sink changes in the Southern Ocean shows the largest disagreements in the Antarctic region, where all models show the largest net CO2 sink increase by the end of the century. This outcome postulates that increased efforts toward improving the representation of sea-ice dynamics and mechanisms of CO2 uptake in the Antarctic region in ESMs will aid adequately simulate the long-term role of the Southern Ocean as a sink of CO2 in a changing climate.


Arranged date for the seminar talk: Jun 13, 2022 at 14:15, BCCR lecture room 4020, Jahnebakken 5