Sequential changes in ocean circulation and biological export productivity during the last glacial–interglacial cycle: a model–data study

• Published in: Climate of the Past
• Main Authors: C. M. O'Neill, A. McC. Hogg, M. J. Ellwood, B. N. Opdyke, S. M. Eggins
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2021
• Subjects: Environmental pollution; TD172-193.5; Environmental protection; TD169-171.8; Environmental sciences; GE1-350; Southern Ocean; Sea ice
• Online Access: https://doi.org/10.5194/cp-17-171-2021; https://doaj.org/article/3b804084f86f4f28989c9732d2b762ce

We conduct a model–data analysis of the marine carbon cycle to understand and quantify the drivers of atmospheric CO 2 concentration during the last glacial–interglacial cycle. We use a carbon cycle box model, “SCP-M”, combined with multiple proxy data for the atmosphere and ocean, to test for variations in ocean circulation and Southern Ocean biological export productivity across marine isotope stages spanning 130 000 years ago to the present. The model is constrained by proxy data associated with a range of environmental conditions including sea surface temperature, salinity, ocean volume, sea-ice cover and shallow-water carbonate production. Model parameters for global ocean circulation, Atlantic meridional overturning circulation and Southern Ocean biological export productivity are optimized in each marine isotope stage against proxy data for atmospheric CO 2 , δ 13 C and Δ 14 C and deep-ocean δ 13 C, Δ 14 C and CO <math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mrow><mn mathvariant="normal">2</mn><mo>-</mo></mrow></msubsup></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="13pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="251ba50b55c42c0a54fe7c72731888ef"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cp-17-171-2021-ie00001.svg" width="13pt" height="17pt" src="cp-17-171-2021-ie00001.png"/></svg:svg> . Our model–data results suggest that global overturning circulation weakened during Marine Isotope Stage 5d, coincident with a ∼ 25 ppm fall in atmospheric CO 2 from the last interglacial period. There was a transient slowdown in Atlantic meridional overturning circulation during Marine Isotope Stage 5b, followed by a more pronounced slowdown and enhanced Southern Ocean biological export productivity during Marine Isotope Stage 4 ( ∼ −30 ...