EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

A Next Generation Ocean Carbon Isotope Model for Climate Studies

Rolf Sonnerup and Mariona Claret
Rolf Sonnerup and Mariona Claret
  • university of washington, Joint Institute for Study of the Atmosphere and Ocean, United States of America (

The 13C/12C of dissolved inorganic carbon (δ13C DIC ) carries valuable information on ocean
biological C-cycling, air-sea CO2 exchange, and circulation. Paleo-reconstructions of oceanic 13C
from sediment cores provide key insights into past as changes in these three drivers. As a step
toward full inclusion of 13C in the next generation of Earth system models, we implemented 13C-
cycling in a 1° lateral resolution ocean-ice-biogeochemistry Geophysical Fluid Dynamics
Laboratory (GFDL) model driven by Common Ocean Reference Experiment perpetual year
forcing. The model improved the mean of modern δ13C DIC over coarser resolution GFDL-model
implementations, capturing the Southern Ocean decline in surface δ13C DIC that propagates to the
deep sea via deep water formation. The model is used here to quantify controls on modern and
anthropogenic δ13C DIC as well as to test their sensitivity to wind speed/gas exchange
We found that reducing the coefficient for air-sea gas exchange following OMIP-CMIP6
protocols reduces deep sea modern δ13C DIC by 0.2 permil and improves the depth-integrated
anthropogenic δ13C DIC relative to previous gas exchange parameterizations. This is because the
δ13C DIC of the endmembers ventilating the deep sea and intermediate waters are highly sensitive to
the wind speed dependence of the air-sea CO2 gas exchange. Additionally, meridional gradients
of surface modern δ13C DIC are better resolved with OMIP-CMIP6. While this model was initially
constructed to study the anthropogenic 13C response, it has promising applications toward longer
time scales. For example, BLING 13 C includes controls on the biological C-pump thought to be
important in the glacial ocean: light and iron limitation, and controls on 13C of organic matter
formation, and thus on ocean δ13C DIC and its vertical gradient, that depend on pCO2 .

How to cite: Sonnerup, R. and Claret, M.: A Next Generation Ocean Carbon Isotope Model for Climate Studies, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8892,, 2022.