The Macquarie Island (LoFlo2G) high-precision continuous atmospheric carbon dioxide record
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Published:2019-02-21
Issue:2
Volume:12
Page:1103-1121
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ISSN:1867-8548
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Container-title:Atmospheric Measurement Techniques
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language:en
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Short-container-title:Atmos. Meas. Tech.
Author:
Stavert Ann R., Law Rachel M.ORCID, van der Schoot Marcel, Langenfelds Ray L., Spencer Darren A., Krummel Paul B.ORCID, Chambers Scott D.ORCID, Williams Alistair G.ORCID, Werczynski Sylvester, Francey Roger J., Howden Russell T.
Abstract
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
midlatitude 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
to 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
0.05 µmol mol−1 depending on the averaging period and
application. Higher precisions are applicable when comparing Macquarie Island
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.
Publisher
Copernicus GmbH
Subject
Atmospheric Science
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