We present here a test of convection uncertainty within a single model framework driven by the same meteorological fields. Our primary goal is to explore to what extent do convection schemes impact atmospheric CO₂ distribution, by testing three referred cloud convection schemes ranging from a very simple to a relatively complex form [Table 1]. Our second goal is to examine the sensitivity of atmospheric CO₂ to its regional emission/sink uncertainty [Fig. 1] constrained by IPCC 2001 at a “fixed” convection scheme to clarify the pros and cons of the convection schemes.

We will present our design of a new autonomous, inexpensive, and robust CO₂ analyzer (AIRCOA), a description of our quality control procedures, and data examples from ongoing deployments.  Our current AIRCOA units require less than $10K (USD) in components, show intercomparability better than 0.1 ppm during laboratory tests, and are designed to run autonomously for months at a time.

A discrepancy exists between current estimates of the Southern Ocean air-sea flux of CO₂.  The most recent estimate using a combination of direct and climatologically-derived pCO₂ measurements [Takahashi et al., 2002] (herein referred to as T02) suggests a Southern Ocean CO₂ sink that is nearly two times greater that that suggested from general circulation models, atmospheric inverse models [Gurney et al., 2002] and oceanic inverse models [Gloor et al., 2003]. Here we employ an independent method to estimate the Southern ocean air-sea flux of CO₂.  Our method exploits all available surface measurements for Dissolved Inorganic Carbon (DIC) and total alkalinity (ALK) from 1986 to 1996. We show that surface age-normalized DIC can be predicted to within ~8mmol/kg and ~10mmol/kg for ALK using standard hydrographic properties, independent of season.  The predictive equations are used in conjunction with World Ocean Atlas (2001) climatologies to estimate an annual cycle of DIC and ALK, while the pCO₂ distribution is calculated using standard carbonate chemistry.  For consistency we use the same gas transfer relationship and wind product from Takahashi et al, [2002] however, we include the effects of sea-ice. We estimate a Southern Ocean CO₂ sink (>40°S) of -0.19±0.26 Pg C for 1995. Our estimates are smaller than those estimated by Takahashi et al, [2002], but consistent with atmospheric / oceanic inverse methods, general circulation models and provides further evidence that the Southern Ocean CO₂ sink in relation to its oceanic surface area, is moderate on a global scale.

Over the last decade the TransCom group has coordinated a number of intercomparisons. The latest project focuses on the diurnal and synoptic behaviour of transport models.  The poster will describe the experiment, introduce the participating models and present a sample of preliminary results.

CO₂ emissions from fossil-fuel combustion can be estimated at the state or monthly level even when full data on fuel combustion are not available. Our hypothesis is that a representative proxy can accurately estimate the pattern of CO₂ emissions if a sufficient fraction of the total can be represented, even if the dataset used does not cover all energy consumption sectors. Our approach employs monthly sales data for each state from the U.S. Department of Energy’s Energy Information Administration (EIA). This is used to estimate the relative proportions of solid, liquid and gaseous fossil fuels for each state for each month.

Quantifying the uptake of anthropogenic carbon by the oceans is a crucial component of understanding the global carbon cycle. Accordingly there has been considerable research in the area, and recently global estimates of the inventory and decadal uptake of anthropogenic carbon have been made using carbon measurements [Sabine et al., 2004] and CFC measurements [McNeil et al., 2003].  However, these methods introduce several assumptions that may introduce systematic biases.  In particular, both methods assume that mixing plays a negligible role in the transport.  Here we estimate the ocean uptake, inventory, and distribution of anthropogenic carbon (C_ant) in the oceans using the transit-time distribution (TTD) method (see Hall et al. 2004, Waugh et al. 2004), which avoids the assumption of weak mixing.

Inverse modeling methods are now commonly used for estimating surface fluxes of carbon dioxide, using atmospheric mass fraction measurements combined with a numerical atmospheric transport model. Michalak et al. [2004] recently developed a geostatistical approach to flux estimation that takes advantage of the spatial and/or temporal correlation in fluxes and does not require prior flux estimates. In this work, a geostatistical implementation of a fixed-lag Kalman smoother is developed and applied to the recovery of gridscale carbon dioxide fluxes for 1997 – 2001 using data from the NOAA-CMDL Cooperative Air Sampling Network.

The inventory of nuclear bomb produced ¹⁴C (bomb ¹⁴C) in the ocean is a major constraint of CO₂ exchange between the atmosphere and ocean in numerical models and analytical estimates of gas exchange. New ¹⁴C data in the ocean, improved methods of separating the bomb ¹⁴C from the natural background of ¹⁴C in the ocean, and reassessment of previous inventories are challenging the canonical estimates of the air-sea gas transfer. An improved method of separating natural ¹⁴C from the observed ¹⁴C distribution is being used to estimate the bomb ¹⁴C distribution and inventory. We use GEOSECS ¹⁴C data to represent the global distribution in 1975, and the new WOCE dataset for 1995 to get two time representations of inventory. To reduce the bias error for averaging zonal bomb ¹⁴C inventories from limited observation stations during the GEOSECS times, we use zonal averages given by Peacock [2004] for re-evaluation of 1975 air-sea CO₂ exchange rates. Zonal inventories for 1995 will be from GLODAP mapping results using WOCE data [Key et al. 2004]. Lateral transport models developed by Broecker et al. [1985] are used to assess the regional air-sea CO₂ exchange rates as well as an appropriately weighted global mean. Four independent methods of estimating bomb ¹⁴C inventory in the ocean show that the original estimate by Broecker et al. [1995] could be about 25% too high, the air-sea CO₂ exchange rates derived from this original bomb ¹⁴C inventory could also be too high by a similar amount. Results of this assessment will be presented.

We present 16 months of semi-continuous Ar/N₂ data measured at the Scripps Pier in La Jolla, CA. The concentration of atmospheric Ar/N₂ depends on air-sea heat flux. As the ocean takes up heat, both argon and nitrogen are degassed to the atmosphere; as the ocean cools, they are taken up. This record is the beginning of a long-term monitoring program that will parallel the O₂/N₂ and CO₂ measurement programs at Scripps and may help resolve the oceanic contribution to atmospheric CO₂ variability.

We examine the growth-rate of atmospheric CO₂ in 2002 and 2003. Observations show consecutive increases of greater than 2 ppmv per year for the first time on the Mauna Loa record. We use a statistical regression to show that increasing anthropogenic emissions and ENSO activity are unable to account for the CO₂ growth-rates of 1992 and 1993 following the Pinatubo volcanic eruption, or the anomalously high growth-rate of 2003. Increased forest fires in the northern hemisphere, consistent with remote-sensing and carbon monoxide measurements, seem likely to have contributed significantly to the 2003 anomaly. We hypothesise that the hot and dry Eurasian summer of 2003 led to an increase in forest fire emissions from Siberia, and may also have directly suppressed land-carbon uptake. Model results lead us to expect a steady increase in airborne fraction as climate change weakens the natural carbon sink and accelerates CO₂ rise.