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| Titel |
10Be and 210Pb in Antarctic air and firn: A tool for examining the air-firn transfer of sub-micron aerosol |
| VerfasserIn |
Christoph Elsässer, Dietmar Wagenbach, Hans Oerter, Anna Wegner, Anton Wallner, Susanne Preunkert, Margareta Hansson |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250056621
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| Zusammenfassung |
| 10Be and 210Pb are mainly produced in the atmosphere by cosmic ray interactions and the
decay of terrigenous 222Rn, respectively. Being immediately attached to the sub-micron
particles they tag the atmospheric cycle of this aerosol body. Moreover, since their sources are
relatively well known and expected to show marginal temporal changes in case
of 210Pb or less than 30% over a solar cycle in case of 10Be they constitute an
ideal tool for studying the air-firn transfer of the sub-micron aerosol over polar ice
sheets.
We discuss in this context our firn data of these radioisotopes obtained during several
Antarctic traverses and from various ice cores extending from sea level up to 3600m a.s.l. on
the central plateau. This spatial distribution is supplemented by our long term atmospheric
records of these radionuclides observed at the coastal Neumayer Station and by shorter ones
from two inland sites.
While at single sites the relative temporal variability of yearly mean radionuclide levels in
firn do not exceed 30%, approximately, we observed systematic, spatial concentration
changes by up to a factor of six going from coastal to inland sites. These trends mainly reflect
the strong contrast in the glacio-meteorological settings within the covered area (as mainly
concerning the scavenging efficiency and particularly the net snow accumulation rate). Even a
steady distinct 10Be increase of a factor two is seen over some 100km in the rather
homogenous upstream area of the East Antarctic EDML drilling site at Kohnen Station (
2890m a.s.l.) suggesting a rather high sensitivity of the air-firn transfer on the accumulation
rate in central Antarctica.
We found a uniform, linear relationship between the site specific mean firn concentration
and the inverse accumulation rate which surprisingly holds for the entire Antarctic
domain studied. This would imply a uniform atmospheric concentration within the
Antarctic boundary layer which was indeed fairly corroborated by our atmospheric
observations. On the other hand, long term atmospheric monitoring suggests a notable
influence of the surface inversion strength on the seasonal, near surface atmospheric
levels; an effect which should be more pronounced at inland locations. Using a crude
air-firn transfer parameterization of 10Be and 210Pb (i.e. conservative, sub-micron
particles) we may infer from our spatial trends among others: a typical dry deposition
velocity of 0.12cm/s and dry deposition to total deposition fractions increasing from
60% at coastal to 90% at inland sites. These results will be discussed in terms of
implications for the interpretation of glacio-chemical records from deep Antarctic ice
cores. |
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