Submitted as: development and technical paper 22 Apr 2021

Submitted as: development and technical paper | 22 Apr 2021

Review status: this preprint is currently under review for the journal GMD.

The importance of turbulent ocean-sea ice nutrient exchanges for simulation of ice algal biomass and production with CICE6.1 and Icepack 1.2

Pedro Duarte1, Philipp Assmy1, Karley Campbell2,3, and Arild Sundfjord1 Pedro Duarte et al.
  • 1Norwegian Polar Institute, Fram Centre, Tromsø, Norway
  • 2Department of Arctic and Marine Biology, UiT The Arctic University of Norway, Norway
  • 3Bristol Glaciology Centre, University of Bristol, UK

Abstract. Different sea-ice models apply unique approaches in the computation of nutrient diffusion between the ocean and the ice bottom, which are generally decoupled from the calculation of turbulent momentum and heat flux. Often, a simple molecular diffusion formulation is used. We argue that nutrient transfer from the ocean to sea ice should be as consistent as possible with momentum and heat transfer, since all these fluxes respond to varying forcing in a similar fashion. We hypothesize that biogeochemical models which do not consider such turbulent nutrient exchanges between the ocean and the sea-ice underestimate bottom-ice algal production. The Los Alamos Sea Ice Model (CICE + Icepack) was used to test this hypothesis by comparing simulations with molecular and turbulent diffusion of nutrients into the bottom of sea ice, implemented in a way that is consistent with turbulent momentum and heat exchanges. Simulation results support the hypothesis, showing a significant enhancement of ice algal production and biomass when nutrient limitation was relieved by bottom-ice turbulent exchange. Our results emphasize the potentially critical role of turbulent exchanges to sea ice algal blooms, and the importance of thus properly representing them in biogeochemical models. The relevance of this becomes even more apparent considering ongoing trends in the Arctic Ocean, with a predictable shift from light to nutrient limited growth of ice algae earlier in the spring, as the sea ice becomes more fractured and thinner with a larger fraction of young ice with thin snow cover.

Pedro Duarte et al.

Status: open (until 17 Jun 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Pedro Duarte et al.

Data sets

Model forcing Pedro Duarte

Model results Pedro Duarte

Model code and software

CICE-Consortium/CICE: CICE with bottom drag, heat and nutrient turbulent diffusion CICE consortium and Pedro Duarte

CICE-Consortium/Icepack: Icepack with bottom drag, heat and nutrient turbulent diffusion CICE consortium and Pedro Duarte

Pedro Duarte et al.


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Short summary
Sea ice modelling is an important part of Earth System Models (ESMs). The results of ESMs are used by the Intergovernmental Panel on Climate Change in their reports. In this study we present an improvement to calculate the exchange of nutrients between the ocean and the sea ice. This nutrient exchange is an essential process to keep the ice associated ecosystem functioning. We found out that previous calculation methods may underestimate the primary production of the ice-associated ecosystem.