The ocean bomb radiocarbon inventory revisited

in Radiocarbon (in press)

Large discrepancies exist among data-based estimates and model reconstructions of the ocean bomb radiocarbon inventory. In order to resolve this gap, it has been proposed that the CO2 piston veloc- ity ... [more ▼]

Large discrepancies exist among data-based estimates and model reconstructions of the ocean bomb radiocarbon inventory. In order to resolve this gap, it has been proposed that the CO2 piston veloc- ity should be revised downward (Sweeney et al., 2007; Müller et al., 2008). Here we compare the transient 14C distributions in the ocean obtained with different formulations of the isotopic ratio commonly used in modeling studies. It is found that both the CO2 increase and the air-sea CO2 flux significantly contribute to the 1990 ocean bomb radiocarbon inventory, by around 10% each. Moreover, these two processes explain more than 25% of the inventory difference be- tween 1974 and 1990. These results imply that, as already argued by Naegler (2009), inventories based on observations which lack infor- mation about CO2 invasion are underestimated. Further, this work allows to gain insight into the reasons for discrepancies among model results. It suggests that while a comprehensive isotopic formulation is needed when addressing the global radiocarbon cycle, a simplified form is more relevant for model calibration and piston velocity assess- ment based on currently available bomb radiocarbon inventories. [less ▲]

Variability in North Pacific intermediate and deep water ventilation during Heinrich events in two coupled climate models

in Deep-Sea Research Part II, Topical Studies in Oceanography (2012), 61-64

ASsessment of modelling uncertainties in long-TERm climate and sea level change projections"Aster" : final report

Report (2012)

Assessing the World Ocean ventilation timescales with simple analogs - the leaky funnel model

Poster (2011, May)

Oxygen, a tool for assessing ocean tracer transport models

Poster (2011, May)

Evaluating climate model performance with various parameter sets using observations over the recent past

in Climate of the Past (2011), 7

A 3D model of ocean biogeochemical cycles and climate sensitivity studies

Doctoral thesis (2011)

Assessment of modelling uncertainties in long-term climate projections: the ASTER project

Conference (2010, October)

Le réchauffement climatique est réel et l’Homme en est le principal responsable

Article for general public (2010)

Description of the Earth system model of intermediate complexity LOVECLIM version 1.2

in Geoscientific Model Development (2010), 3(2), 603-633

The main characteristics of the new version 1.2 of the three-dimensional Earth system model of intermediate complexity LOVECLIM are briefly described. LOVECLIM 1.2 includes representations of the ... [more ▼]

The main characteristics of the new version 1.2 of the three-dimensional Earth system model of intermediate complexity LOVECLIM are briefly described. LOVECLIM 1.2 includes representations of the atmosphere, the ocean and sea ice, the land surface (including vegetation), the ice sheets, the icebergs and the carbon cycle. The atmospheric component is ECBilt2, a T21, 3-level quasi-geostrophic model. The ocean component is CLIO3, which consists of an ocean general circulation model coupled to a comprehensive thermodynamic-dynamic sea-ice model. Its horizontal resolution is of 3° by 3°, and there are 20 levels in the ocean. ECBilt-CLIO is coupled to VECODE, a vegetation model that simulates the dynamics of two main terrestrial plant functional types, trees and grasses, as well as desert. VECODE also simulates the evolution of the carbon cycle over land while the ocean carbon cycle is represented by LOCH, a comprehensive model that takes into account both the solubility and biological pumps. The ice sheet component AGISM is made up of a three-dimensional thermomechanical model of the ice sheet flow, a visco-elastic bedrock model and a model of the mass balance at the ice-atmosphere and ice-ocean interfaces. For both the Greenland and Antarctic ice sheets, calculations are made on a 10 km by 10 km resolution grid with 31 sigma levels. LOVECLIM1.2 reproduces well the major characteristics of the observed climate both for present-day conditions and for key past periods such as the last millennium, the mid-Holocene and the Last Glacial Maximum. However, despite some improvements compared to earlier versions, some biases are still present in the model. The most serious ones are mainly located at low latitudes with an overestimation of the temperature there, a too symmetric distribution of precipitation between the two hemispheres, and an overestimation of precipitation and vegetation cover in the subtropics. In addition, the atmospheric circulation is too weak. The model also tends to underestimate the surface temperature changes (mainly at low latitudes) and to overestimate the ocean heat uptake observed over the last decades. [less ▲]