Using a coupled 3D hydrodynamic-biogeochemical model system for the Northwest-European shelf we simulated the years 1993-96, which exhibit an extremely strong transition from a NAOI-high to a NAOI-low regime. The induced temperature-shift had two consequences for the carbon budget of the North Sea: Firstly it increased the CO₂ solubility and secondly it destabilized the water column in spring 1996. The latter effect was the precondition for mixing events which brought new nitrogen for primary production into the upper layer. Consequently the air-sea flux was 540 Gmol C a^-1 in 1996, the NAOI-low year, and it was 203 Gmol C a^-1 in 1995, the year with the highest NAOI.

A Time Dependent Inverse (TDI) model is used to estimate CO₂ fluxes for 64 regions of the globe from atmospheric data in the period January 1988–December 2001. These estimated are then used for understanding interannual variability in fluxes and simulating the CO₂ concentrations at various sites. The NIES/FRCGC transport model driven by interannually varying meteorology is used in both part of the analysis. Estimated atmospheric CO₂ concentrations agree closely with those observed at various sites globally.

The Amazon region of South America plays a significant role in global cycles of water, energy and carbon, yet it is also one of the most challenging biogeographical areas of the world to model correctly. Numerous global climate models have problems with anomalous die-back of the Amazon rain forest variously attributed to inadequate representation of rainfall, faulty soil moisture dynamics or an inability to correctly simulate the drought tolerance of the vegetation. Such misrepresentation of the Amazon in global climate models can cause larger than observed excursions of the global carbon cycle. This poster explores soil moisture and drought stress for Amazonia with the Simple Biosphere Model (SiB3) and possible reasons and solutions to the rain-forest die back problem, which should lead to more reasonable estimates of carbon fluxes at the ecosystem scale.

Increasing ocean stratification associated with global warming has been posited to serve as a positive feedback on global warming, reducing the oceanic uptake of anthropogenic carbon dioxide. We suggest that a poleward shift of westerly winds combined with future increases in atmospheric carbon dioxide may drive an increase in the CO₂ uptake in the Southern Ocean, representing a negative feedback on atmospheric anthropogenic CO₂.

The mixing ratios of atmospheric CO₂ were observed at the summit of Mt. Fuji by using a system for continuous measurements during September 2002-February 2003 and May 2003-May 2004. The observed CO₂ variations at Mt. Fuji showed a seasonal cycle of the background level with a maximum around April and a minimum around August. A lot of episodic events with a large enhancement of CO₂ were found, and the episodic enhancements of CO₂ at Mt. Fuji were well associated with increased CO peaks observed at the same time. The enhancement ratios of CO to CO₂ mixing ratios (ΔCO/ΔCO₂) mainly showed lower values of less than 0.03 due to urban/industrial sources, while relatively higher ΔCO/ΔCO₂ ratios up to 0.08 were also found for the episodic events due to the biomass burning emissions. Three-dimensional transport model simulations of CO suggested that the major contributions for the increased events at Mt. Fuji were from China (~50%) and the other major regions were Southeast Asia and South Asia (~10%).

In a Carbon Cycle Data Assimilation System (CCDAS) one infers the values of the parameters controlling the function of a process model using various observations. One can then calculate quantities of interest from the optimized parameters and the model. One can also calculate the uncertainties on the parameters and propagate these to uncertainties of the calculated quantities. In Rayner et al. [2005] we assimilated atmospheric observations over two decades, into a terrestrial model and calculated fluxes over this period. Here we extend this work by calculating the response of the calibrated terrestrial biosphere to a GCM simulation of future climate. Using this combination we are able to comment on the fate of terrestrial carbon pools and fluxes under climate change, calculate the uncertainties of the response, and determine which parameters in the model are responsible for this uncertainty. We include an extra parameter that scales the climate change signal from the GCM projection. We thus extend the sensitivity and uncertainty analysis to include the climate sensitivity.

An idealized general circulation model is constructed of the ocean’s deep circulation and CO₂ system that reproduces the main features of glacial-interglacial CO₂ cycles, including the tight correlation between atmospheric CO₂ and Antarctic temperatures, the lead of Antarctic temperatures over CO₂ at terminations, and the shift of the ocean’s ¹³C minimum from the North Pacific to the Atlantic sector of the Southern Ocean. The model is based on a new idea about the nature of the glacial-interglacial cycles in which the driving force is independent of the orbital forcing and is not in the ocean. The key to glacial-interglacial transitions, we claim, is a relationship between the mid-latitude westerly winds, atmospheric CO₂, and the mean state of the atmosphere. Cold glacial climates seem to have equatorward-shifted westerlies, which allow more respired CO₂ to accumulate in the deep ocean. Warm climates like the present have poleward-shifted westerlies that flush respired CO₂ out of the deep ocean.

In recent years attention has focused on the role of terrestrial biosphere dynamics in the climate system, and the possibility of large land-atmosphere carbon cycle feedbacks under human-induced future climate warming. During the 1990s rapid development of Dynamic Global Vegetation Models (DGVMs) led a growing community to soon recognize the need for model evaluation and intercomparison. In Cramer et al. 2000 six DGVMs were run using identical forcing data based on the HadCM2 GCM climatology (1860-2100) and the IS92a emission scenario.

In this study we evaluate the individual and combined impacts of CO₂, climate and Ozone on future terrestrial carbon storage using the computationally efficient GCM analogue model coupled to the MOSES/TRIFFID land surface carbon cycle model. Ozone is modelled to have a significant detrimental effect on future plant productivity and hence terrestrial carbon storage, opposing the enhanced production and terrestrial carbon storage associated with elevated atmospheric CO₂ concentrations.

Soil moisture measurements in an Australian tropical savanna show accumulating soil water under three years of Free Air CO₂ Enrichment (FACE).  Most of this accumulation is occurring below the rooting depth of grasses.  Although this increase in stored soil water is only a fraction (< 0.3% yr^-1) of annual rainfall, it is cumulative and may advantage deep-rooted woody plants.