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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Discussion papers | Copyright
https://doi.org/10.5194/amt-2018-300
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 25 Oct 2018

Research article | 25 Oct 2018

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Measurement Techniques (AMT).

The Macquarie Island [LoFlo2G] high-precision continuous atmospheric carbon dioxide record

Ann R. Stavert1, Rachel M. Law1, Marcel van der Schoot1, Ray L. Langenfelds1, Darren A. Spencer1, Paul B. Krummel1, Scott D. Chambers2, Alistair G. Williams2, Sylvester Werczynski2, Roger J. Francey1, and Russell T. Howden1 Ann R. Stavert et al.
  • 1CSIRO Oceans and Atmosphere, Aspendale, Victoria, 3195, Australia
  • 2Australian Nuclear Science and Technology Organisation, Kirawee, New South Wales, 2232, Australia

Abstract. The Southern Ocean (south of 30°S) is a key global scale sink of carbon dioxide (CO2). However, the isolated and inhospitable nature of this environment has restricted the number of oceanic and atmospheric CO2 measurements in this region. This has limited the scientific community’s ability to investigate trends and seasonal variability of the sink. Compared to regions further north, the near-absence of terrestrial CO2 exchange and strong large-scale zonal mixing demands unusual inter-site measurement precision to help distinguish the presence of mid-to-high latitude ocean exchange from large CO2 fluxes transported southwards in the atmosphere. Here we describe a continuous, in-situ, ultra-high-precision, Southern Ocean region CO2 record, which ran at Macquarie Island (54°37’S, 158°52’E) from 2005–2016 using a LoFlo2 instrument, along with its calibration strategy, uncertainty analysis and baseline filtering procedures. Uncertainty estimates calculated for minute and hourly frequency data range from 0.01 to 0.05μmolmol−1 depending on averaging period and application. Higher precisions are applicable when comparing MQA LoFlo measurements to those of similar instruments on the same internal laboratory calibration scale and more uncertain values are applicable when comparing to other networks. Baseline selection is designed to remove measurements that are influenced by local, Macquarie Island, CO2 sources, with effective removal achieved using a within-minute CO2 standard deviation metric. Additionally, measurements that are influenced by CO2 fluxes from Australia or other southern hemisphere land masses are effectively removed using model-simulated radon concentration. A comparison with flask records of atmospheric CO2 at Macquarie Island highlights the limitation of the flask record (due to corrections for storage time and limited temporal coverage) when compared to the new high-precision, continuous record; the new record shows much less noisy seasonal variations than the flask record. As such this new record is ideal for improving our understanding of the spatial and temporal variability of the Southern Ocean CO2 flux particularly when combined with data from similar instruments at other Southern Hemispheric locations.

Ann R. Stavert et al.
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Ann R. Stavert et al.
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