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1. Regional patterns and temporal evolution of ocean iron fertilization and CO2 drawdown during the last glacial termination

   https://doi.org/10.1016/j.epsl.2020.116675  

   Lambert, Fabrice ; Opazo, Natalia ; Ridgwell, Andy ; Winckler, Gisela ; Lamy, Frank ; Shaffer, Gary ; Kohfeld, Karen ; Ohgaito, Rumi ; Albani, Samuel ; Abe-Ouchi, Ayako ( January 2021 , Earth and Planetary Science Letters)

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2. Highly bioavailable dust-borne iron delivered to the Southern Ocean during glacial periods

   https://doi.org/10.1073/pnas.1809755115  

   Shoenfelt, Elizabeth M. ; Winckler, Gisela ; Lamy, Frank ; Anderson, Robert F. ; Bostick, Benjamin C. ( October 2018 , Proceedings of the National Academy of Sciences)

   Changes in bioavailable dust-borne iron (Fe) supply to the iron-limited Southern Ocean may influence climate by modulating phytoplankton growth and CO₂fixation into organic matter that is exported to the deep ocean. The chemical form (speciation) of Fe impacts its bioavailability, and glacial weathering produces highly labile and bioavailable Fe minerals in modern dust sources. However, the speciation of dust-borne Fe reaching the iron-limited Southern Ocean on glacial−interglacial timescales is unknown, and its impact on the bioavailable iron supply over geologic time has not been quantified. Here we use X-ray absorption spectroscopy on subantarctic South Atlantic and South Pacific marine sediments to reconstruct dust-borne Fe speciation over the last glacial cycle, and determine the impact of glacial activity and glaciogenic dust sources on bioavailable Fe supply. We show that the Fe(II) content, as a percentage of total dust-borne Fe, increases from ∼5 to 10% in interglacial periods to ∼25 to 45% in glacial periods. Consequently, the highly bioavailable Fe(II) flux increases by a factor of ∼15 to 20 in glacial periods compared with the current interglacial, whereas the total Fe flux increases only by a factor of ∼3 to 5. The change in Fe speciation is dominated by primary Fe(II) silicates characteristic of glaciogenic dust. Our results suggest that glacial physical weathering increases the proportion of highly bioavailable Fe(II) in dust that reaches the subantarctic Southern Ocean in glacial periods, which represents a positive feedback between glacial activity and cold glacial temperatures.

    

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3. Connecting Antarctic sea ice to deep-ocean circulation in modern and glacial climate simulations: SEA ICE AND GLACIAL AMOC

   https://doi.org/10.1002/2017GL073936  

   Marzocchi, Alice ; Jansen, Malte F. ( June 2017 , Geophysical Research Letters)
4. Weak overturning circulation and high Southern Ocean nutrient utilization maximized glacial ocean carbon

   https://doi.org/10.1016/j.epsl.2018.05.038  

   Muglia, Juan ; Skinner, Luke C. ; Schmittner, Andreas ( August 2018 , Earth and Planetary Science Letters)
5. Strong glacial-interglacial variability in upper ocean hydrodynamics, biogeochemistry, and productivity in the southern Indian Ocean

   https://doi.org/10.1038/s43247-021-00148-0  

   Tangunan, Deborah ; Berke, Melissa A. ; Cartagena-Sierra, Alejandra ; Flores, José Abel ; Gruetzner, Jens ; Jiménez-Espejo, Francisco ; LeVay, Leah J. ; Baumann, Karl-Heinz ; Romero, Oscar ; Saavedra-Pellitero, Mariem ; et al ( December 2021 , Communications Earth & Environment)

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   Abstract In the southern Indian Ocean, the position of the subtropical front – the boundary between colder, fresher waters to the south and warmer, saltier waters to the north – has a strong influence on the upper ocean hydrodynamics and biogeochemistry. Here we analyse a sedimentary record from the Agulhas Plateau, located close to the modern position of the subtropical front and use alkenones and coccolith assemblages to reconstruct oceanographic conditions over the past 300,000 years. We identify a strong glacial-interglacial variability in sea surface temperature and productivity associated with subtropical front migration over the Agulhas Plateau, as well as shorter-term high frequency variability aligned with variations in high latitude insolation. Alkenone and coccolith abundances, in combination with diatom and organic carbon records indicate high glacial export productivity. We conclude that the biological pump was more efficient and strengthened during glacial periods, which could partly account for the reported reduction in atmospheric carbon dioxide concentrations. 

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