Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
doi:10.5194/acp-2016-1110
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
20 Dec 2016
Review status
This discussion paper is under review for the journal Atmospheric Chemistry and Physics (ACP).
Sixty years of radiocarbon dioxide measurements at Wellington, New Zealand 1954–2014
Jocelyn C. Turnbull1,2, Sara E. Mikaloff Fletcher3, India Ansell1, Gordon Brailsford3, Rowena Moss3, Margaret Norris1, and Kay Steinkamp3 1GNS Science, Rafter Radiocarbon Laboratory, Lower Hutt, New Zealand
2CIRES, University of Colorado at Boulder, Boulder, Colorado, USA
3NIWA, Wellington, New Zealand
Abstract. We present 60 years of Δ14CO2 measurements from Wellington, New Zealand (41° S, 175° E). The record has been extended and fully revised. New measurements have been used to evaluate the existing record and to replace original measurements where warranted. This is the earliest atmospheric Δ14CO2 record and records the rise of the 14C "bomb spike", the subsequent decline in Δ14CO2 as bomb 14C moved throughout the carbon cycle and increasing fossil fuel CO2 emissions further decreased atmospheric Δ14CO2. The initially large seasonal cycle in the 1960s reduces in amplitude and eventually reverses in phase, resulting in a small seasonal cycle of about 2 ‰ in the 2000s. The seasonal cycle at Wellington is dominated by the seasonality of cross-tropopause transport, and differs slightly from that at Cape Grim, Australia, which is influenced by anthropogenic sources in winter. Δ14CO2 at Cape Grim and Wellington show very similar trends, with significant differences only during periods of known measurement uncertainty. In contrast, Northern Hemisphere clean air sites show a higher and earlier bomb 14C peak, consistent with a 1.4-year interhemispheric exchange time. From the 1970s until the early 2000s, the Northern and Southern Hemisphere Δ14CO2 were quite similar, apparently due to the balance of 14C-free fossil fuel CO2 emissions in the north and 14C-depleted ocean upwelling in the south. The Southern Hemisphere sites show a consistent and marked elevation above the Northern Hemisphere sites since the early 2000s, which is most likely due to reduced upwelling of 14C-depleted and carbon-rich deep waters in the Southern Ocean. This developing Δ14CO2 interhemispheric gradient is consistent with recent studies that indicate a reinvigorated Southern Ocean carbon sink since the mid-2000s, and suggests that upwelling of deep waters plays an important role in this change.

Citation: Turnbull, J. C., Mikaloff Fletcher, S. E., Ansell, I., Brailsford, G., Moss, R., Norris, M., and Steinkamp, K.: Sixty years of radiocarbon dioxide measurements at Wellington, New Zealand 1954–2014, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1110, in review, 2016.
Jocelyn C. Turnbull et al.
Jocelyn C. Turnbull et al.
Jocelyn C. Turnbull et al.

Viewed

Total article views: 241 (including HTML, PDF, and XML)

HTML PDF XML Total Supplement BibTeX EndNote
176 31 34 241 5 16 32

Views and downloads (calculated since 20 Dec 2016)

Cumulative views and downloads (calculated since 20 Dec 2016)

Viewed (geographical distribution)

Total article views: 241 (including HTML, PDF, and XML)

Thereof 239 with geography defined and 2 with unknown origin.

Country # Views %
  • 1

Saved

Discussed

Latest update: 28 May 2017
Publications Copernicus
Download
Short summary
We present a 60 year record of radiocarbon in carbon dioxide (14CO2) from Wellington New Zealand. It records the atmospheric 14C "bomb spike" and decline as bomb 14C moved through the carbon cycle and fossil fuel emissions increased. The bomb peak is lower and 1.4 years later than in the Northern Hemisphere. Since the early 2000s Wellington 14CO2 is elevated above the Northern Hemisphere implying a reinvigorated Southern Ocean carbon sink in which deep water upwelling plays an important role.
We present a 60 year record of radiocarbon in carbon dioxide (14CO2) from Wellington New...
Share