 |
| Titel |
Records of Northern Hemisphere atmospheric carbon monoxide and hydrogen back to about 1960 AD from Greenland firn air |
| VerfasserIn |
V. V. Petrenko, P. Novelli, D. M. Etheridge, I. Levin, Z. Wang, T. Blunier, P. Lang, L. P. Steele, F. Vogel, J. Chappellaz |
| Konferenz |
EGU General Assembly 2009
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250024825
|
|
|
|
|
|
| Zusammenfassung |
| Carbon monoxide (CO) plays a key role in global atmospheric chemistry by being the main
sink of atmospheric hydroxyl radicals (OH). The relatively short CO atmospheric lifetime
(about 2 months) together with larger emissions in the Northern Hemisphere (NH) currently
result in a large interhemispheric [CO] gradient (1). Reliable records of past [CO] from both
hemispheres are therefore essential for understanding past changes in atmospheric [OH] as
well as changes in biomass burning. Earlier attempts at reconstruction of NH [CO] suffered
from apparent in-situ CO production in ice and firn (2, 3). We present a record of
high-latitude NH [CO] to about 1960 AD, from measurements by four different laboratories
of firn air collected at the NEEM ice core site in Greenland. Procedural blanks indicate no
detectable [CO] contamination from sampling. The smooth, gradual changes in the [CO]
profile with depth in the firn, as well as excellent agreement with a firn air record from
another cold Greenland site (NGRIP) are consistent with the NEEM firn CO record being
unaltered. Our results suggest that high-latitude NH mean annual [CO] increased
from about 1960 to the 1980s, with measured peak values of 155 – 160 ppb. Firn
air data from sites in Antarctica show Southern Hemisphere [CO] also increasing
during this time period. Our results further suggest that high-latitude NH mean
annual [CO] gradually declined after the 1980s, which is consistent with early direct
atmospheric measurements. [CO] in the oldest samples is 135 – 140 ppb. In addition, we
present the NEEM firn record of molecular hydrogen (H2), from measurements by
three laboratories. The main features of the [H2] record closely parallel the [CO]
record, with results suggesting an increase in [H2] from about 1960 to the 1980s,
followed by a gradual decline. This is again consistent with early direct atmospheric
measurements. The similarity in the main features of [CO] and [H2] records is expected
because of broadly similar sources for the two gases, and is once again consistent
with the NEEM firn [CO] record being unaltered. Dates given are preliminary and
approximate only. Modeling is currently in progress to use the NEEM firn [CO]
and [H2] records to constrain the high-latitude NH atmospheric history for these
gases.
References: 1. P. C. Novelli, K. A. Masarie, P. M. Lang, J. Geophys.Res. 103, 19015
(1998). 2. I. D. Clark et al., J. Geophys. Res. 112, D01301 (2007). 3. D. Haan, D. Raynaud,
Tellus 50B, 253 (1998). |
|
|
|
|
|
|