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3.2. ICE AND CLIMATE 111
3.2.4 Progress in developing novel tools for Antarctic ice core research
Dietmar Wagenbach (participating scientists: Rolf Weller (AWI) and Matthias Auer (VERA))
Abstract Progress achieved in automatic central Antarctica aerosol sampling and in the prospecting
of the 26 Al/ 10 Be dating tool are reported and assessed.
Figure 3.12: Seasonal cycle of total nitrate in central Antarctica obtained by automatic aerosol samplings
(left), overall changes of mean 26 Al/ 10 Be ratios seen in Antarctic (Neumayer), alpine (Sonnblick)
and upper troposphere aerosol as well as in Antarctic snow from Dome C (right).
Background See also Annual IUP Report 2005.
a) Automatic sampling: Interpretation of Antarctic
ice core records of aerosol species needs considering
year round atmospheric records, which
were not available however from inland positions.
Therefore IUP developed an autonomous aerosol
sampling device (ROBERTA) to be deployed year
round at the EPICA-DML drill site in the Atlantic
sector of east Antarctica.
b) 26 Al: Also the essentially unknown age and
stratigraphical feature of the basal core sections
challenge experimental dating tools to be deployed
here. In close collaboration with the University
of Vienna the dating deficit of very old ice
samples has been tackled therefore by exploring
the feasibility of the 26 Al/ 10 Be ratio (apparent
T 1/2 = 1.310 −6 a) as a radiometric chronometer.
Progress report
a) Deploying an improved sampler version, year
round, unattended running of the aerosol sampling
system at the EDML drill site could be successfully
maintained in 2005, indicating, that the
polar night energy problem became almost settled.
Evaluation of the first comprehensive observations
on the seasonal change of major ion
revealed, relative to coastal records: important
phase shifts of species with marine sources, but
a close agreement of nitrate cycles [Weller & Wagenbach,
submitted]. This surprising coherence
may need revisiting the open question of the major
Antarctic nitrate source.
b) In extending our former 26 Al/ 10 Be analyses
to Antarctic surface snow and high tropospheric
samples and in gaining first 53 Mn results from
Antarctic aerosol we got following evidences for
the 26 Al dating potential: (1) the overall (short
term) 26 Al / 10 Be variability in various recent
snow aerosol samples is less than 6 %. This figure
would translate into a dating uncertainty of
around 100 ky, indicating as well a negligible influence
of terrestical 26 Al. (2) interplanetary dust
(IPD) appears to contribute to the atmospheric
26 Al budget of Antarctica by some % only. This
results is, however, still to be confirmed by respective
firn analyses, needing to process some 100kg
of surface snow.
Future work
a) Adding results from ongoing 2006 samplings,
glacio-meteorological and snow pit data, the
source pattern and governing air/firn deposition
processes will be elucidated for the DML drill site
realm.
b) Backed up by surface snow 53 Mn first
26 Al/ 10 Be analyses are envisaged for the basal section
of Antarctic ice cores, perhaps including some
Ma old ground ice from the Dry Valleys.
Funding
a) AWI-Cooperation Contract
b) joint Austrian Research Fund (FWF) project
among VERA and IUP
Main publications a) [Weller & Wagenbach,
submitted], b) [Auer et al. , in pressb]