Long-term variability in Southern Hemisphere Δ14CO2 observed at Wellington, New Zealand
Abstract:Atmospheric Δ14CO2 measurements have been made at Wellington, New Zealand, since December 1954. This is the longest 14CO2 record available from anywhere in the world, predating the 14C bomb spike by several years and documenting the movement of the bomb spike into the Southern Hemisphere and other parts of the global carbon cycle. In more recent times, the spatial and temporal changes in Δ14CO2 are thought to be dominated by two main drivers: (i) the addition of 14C-free, fossil-fuel derived CO2, which occurs mainly over Northern Hemisphere continents, and (ii) the net flux of 14C-depleted CO2 into the atmosphere from the oceans, most strongly from the Southern Ocean. Thus Δ14CO2 measurements can provide key information on both the source and fate of fossil fuel CO2 emissions. In particular, Southern Hemisphere Δ14CO2 records have the potential to elucidate the mechanisms that drive Southern Ocean carbon exchange, a key component of the global carbon cycle.
We will present an updated Wellington Δ14CO2 record. It is primarily based on ~2 week integrated samples collected by CO2 absorption into NaOH solution. The results have now been thoroughly reviewed, revised where necessary, and extended through to 2014. In addition, we use a series of new measurements on archived “NaOH” samples, archived whole air flask samples and tree rings to span gaps in the main record and to re-measure key periods, thereby producing a record with lower variability and higher precision. We use new modeling tools to examine the causes of the temporal variability in the Wellington 14CO2 record.