Including an ocean carbon cycle model into &amp;lt;i&amp;gt;i&amp;lt;/i&amp;gt;LOVECLIM (v1.0)

N Bouttes,D M Roche,L Bopp,V Mariotti

doi:10.5194/gmd-8-1563-2015

Abstract

Abstract. The atmospheric carbon dioxide concentration plays a crucial role in the radiative balance and as such has a strong influence on the evolution of climate. Because of the numerous interactions between climate and the carbon cycle, it is necessary to include a model of the carbon cycle within a climate model to understand and simulate past and future changes of the carbon cycle. In particular, natural variations of atmospheric CO2 have happened in the past, while anthropogenic carbon emissions are likely to continue in the future. To study changes of the carbon cycle and climate on timescales of a few hundred to a few thousand years, we have included a simple carbon cycle model into the iLOVECLIM Earth System Model. In this study, we describe the ocean and terrestrial biosphere carbon cycle models and their performance relative to observational data. We focus on the main carbon cycle variables including the carbon isotope ratios δ13C and the Δ14C. We show that the model results are in good agreement with modern observations both at the surface and in the deep ocean for the main variables, in particular phosphates, dissolved inorganic carbon and the carbon isotopes.

Highlights

The carbon cycle is a key component of climate and environmental sciences, both because CO2 is a greenhouse gas (Tyndall, 1861) and has a direct impact on climate, and because it plays an important role in ocean acidification (Orr et al, 2005) which directly impacts marine life
Some are due to errors in the simulation of surface regional features which propagate in the ocean interior, such as the North Atlantic where the high salinity from the Tropics is transported too much northward compared to the data
Another source of error could come from the diffusion which seems too strong in the North Atlantic where the characteristic values of North Atlantic Deep Water (NADW) for salinity, PO4, dissolved inorganic carbon (DIC) and carbon isotopes decrease too rapidly while it penetrates southward

Summary

Introduction

The carbon cycle is a key component of climate and environmental sciences, both because CO2 is a greenhouse gas (Tyndall, 1861) and has a direct impact on climate, and because it plays an important role in ocean acidification (Orr et al, 2005) which directly impacts marine life. The three main carbon reservoirs involved on the timescale of a few thousand years are the atmosphere, the ocean and the land biosphere. The ocean is the biggest of the three reservoirs with around 39 000 GtC, while the atmosphere contains around 589 GtC and the terrestrial biosphere between 1950 and 3050 GtC for the pre-industrial (Ciais et al, 2013). Changes in the ocean temperature will modify the solubility of CO2: the warmer the ocean the less soluble CO2 becomes, which decreases the carbon stock in the ocean and increases atmospheric CO2. Temperature, as well as humidity, influences the development of the terrestrial biosphere and decomposition of terrestrial organic matter. It is necessary to include a model of the carbon cycle within a climate model to understand past changes and anticipate the future evolution of the carbon cycle and climate

Results

Discussion

Conclusion