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| Titel |
High resolution measurements of carbon monoxide along a late Holocene Greenland ice core: evidence for in situ production |
| VerfasserIn |
X. Faïn, J. Chappellaz, R. H. Rhodes, C. Stowasser, T. Blunier, J. R. McConnell, E. J. Brook, S. Preunkert, M. Legrand, T. Debois, D. Romanini |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 10, no. 3 ; Nr. 10, no. 3 (2014-05-22), S.987-1000 |
| Datensatznummer |
250116974
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| Publikation (Nr.) |
 copernicus.org/cp-10-987-2014.pdf |
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| Zusammenfassung |
| We present high-resolution measurements of carbon monoxide (CO)
concentrations from a shallow ice core of the North Greenland Eemian Ice
Drilling project (NEEM-2011-S1). An optical-feedback cavity-enhanced
absorption spectrometer (OF-CEAS) coupled to a continuous melter system
performed continuous, online analysis during a four-week measurement campaign.
This analytical setup generated stable measurements of CO concentrations
with an external precision of 7.8 ppbv (1σ), based on repeated
analyses of equivalent ice core sections. However, this first application of
this measurement technique suffered from a poorly constrained procedural
blank of 48 ± 25 ppbv and poor accuracy because an absolute
calibration was not possible. The NEEM-2011-S1 CO record spans 1800 yr and
the long-term trends within the most recent section of this record
(i.e., post 1700 AD) resemble the existing discrete CO measurements from the
Eurocore ice core. However, the CO concentration is highly variable (75–1327 ppbv
range) throughout the ice core with high frequency (annual scale), high
amplitude spikes characterizing the record. These CO signals are too abrupt
and rapid to reflect atmospheric variability and their prevalence largely
prevents interpretation of the record in terms of atmospheric CO variation.
The abrupt CO spikes are likely the result of in situ production occurring
within the ice itself, although the unlikely possibility of CO production
driven by non-photolytic, fast kinetic processes within the continuous
melter system cannot be excluded. We observe that 68% of the CO spikes
are observed in ice layers enriched with pyrogenic aerosols. Such aerosols,
originating from boreal biomass burning emissions, contain organic
compounds, which may be oxidized or photodissociated to produce CO within
the ice. However, the NEEM-2011-S1 record displays an increase of
~0.05 ppbv yr−1 in baseline CO level prior to 1700 AD (129 m
depth) and the concentration remains elevated, even for ice layers depleted
in dissolved organic carbon (DOC). Thus, the processes driving the likely
in situ production of CO within the NEEM ice may involve multiple, complex
chemical pathways not all related to past fire history and require further investigation. |
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