Towards Improved Polar Biogeochemistry: Integrating an Explicit Sea-Ice Biogeochemical Model in NEMO/SI3

Ongoing rapid changes in sea-ice cover require a more accurate representation of their interactions with marine biogeochemistry and cascading impacts on the global carbon cycle. Yet, despite the critical role of polar biogeochemical processes, assessing these interactions remains challenging as sea ice and snow are often treated as biogeochemically inert in most large-scale and climate models.

To address this gap, we present a novel integration of the Biogeochemical Flux Model in Sea Ice (BFMSI) within the three-dimensional global NEMO/SI3 system. This innovative coupling explicitly accounts for dynamic interactions between sea-ice physical properties and biogeochemical processes.

To evaluate this implementation, we perform two sensitivity experiments: one assuming a fixed biologically active layer in the sea ice and another where the thickness of this layer dynamically adjusts based on sea-ice permeability, as derived from the sea-ice model. Model results for 2000–2021 are compared against available observations, providing a brief performance assessment. The two experiments are also analyzed to evaluate the sensitivity of ice and under-ice biogeochemical properties to the biological active layer parameterization and the representation of the light transmission through the ice/snow.

These results aim to provide insights into the interplay between sea-ice properties and ocean biogeochemical processes, informing future studies on the role of sea-ice biogeochemistry in shaping the global carbon cycle and its response to ongoing climatic warming.