T1-P28 Observations of atmospheric radionuclide cycles The

Observations of atmospheric radionuclide cycles: The benefit for global Observations
off atmospheric
ph i radionuclide
y l The
gl b l
Ob
ti
t
di
lid cycles:
Th benefit
b
fit for
f global
st dies
paleoclimate studies
paleoclimate studies Christoph Elsässer (1),
Christoph Elsässer (1), Dietmar Wagenbach (1), Rebecca Bremen (1), Ingeborg Levin (1), Rolf Weller (2), Clemens Schlosser (3)
(1) Dietmar Wagenbach (1),
(1) Rebecca Bremen (1),
(1) Ingeborg Levin (1),
(1) Rolf Weller (2),
(2) Clemens Schlosser (3) and Matthias Auer (4)
and Matthias Auer (4)
(1) Institut für Umweltphysik, University of Heidelberg, Germany ([email protected] heidelberg.de), (2) Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany, (3) Bundesamt für Strahlenschutz, Freiburg, Germany, (1) Institut für Umweltphysik, University of Heidelberg, Germany ([email protected]‐heidelberg.de), (2) Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany, (3) (4) CTBTO P
(4) CTBTO Preparatory Commission, Vienna International Center, Vienna, Austria t
C
i i
Vi
I t
ti
l C t Vi
A ti
210Pb
The IUP Heidelberg
Th
H id lb g q
quasi‐continuously
i
ti
ly measures
and
d
since
i
27
years at Neumayer Station in coastal Antarctica (see Elsässer et al.
al (2011)).
(2011))
Photo: O. Eisen IUP/AWI
Why measure
14C
10
1.4
Be
12
1.2
1.0
0.6
24
2.4
2.2
20
2.0
210
Be/ Pb
18
1.8
10
7
B / Be
Be/
B
1.6
14
1.4
7
7
08
0.8
Be / B
B
Be ato
om
m ra
atio
1.6
1.4
12
1.2
10
1.0
08
0.8
0.6
10
Pb
b [a
activvityy ra
atio
o]
210
0
Be /
B
200
175
5
150
125
100
75
Be
B
Be
rellative un
nits
Be
rellative un
nits
relatiive un
nits
7
1.2
J F M A MJ J A S O N D J F M A M
1984
1988
1992
0.5
1996
2000
2004
2008
Fig. 3: Records of 7Be and 10Be in boundary
Fig
layer air at Neumayer station compared to
neutron monitor count rate reflecting the
production
d ti signal
i l (solar
( l cycle).
l )
Fig. 4: Mean sesonal cycles of 7Be, 210Pb
and
d 10Be
B att Neumayer
N
and
d their
th i respective
ti
ratios (for details see Elsässer et al.
al (2011)).
(2011))
J F M A M J J A S O N D J F M A M
Last Glacial Maximum
Fig. 1: Simulated atmospheric Δ14C modified after Köhler
Fig
et al.l [[2006].
[2006]]
-44
low
18
δ O
-42
42
GISP ice core
-40
temperature
p
&
accumulation
-34
34
SSeparating the production signal from p ti g th p d ti
ig l f
climate
climate modulations
li t modulations
d l ti
-32
10Be
-38
38
-36
high
25000
20000 15000
age [BP]
10000
5000
0
data from Finkel and Nishiizumi, 1997; Grootes et al., 1993
Fig.
Fi
g 2:
2 10Be
B concentration
t ti in
i the
th GISP ice
i core contrasted
t t d to
t
the respective δ18O record which basically indicates variations
in temperature and associated accumulation rate changes.
is sensitive to aerosol transport and deposition. Fig. 2
clearly
l ly illustrates
ill
the
h climate
li
modulation
d l i off a 10Be
B ice
i core
signal The challenge to disentagle the production signal
signal.
from climate modulations is not sufficiently solved,
solved yet.
yet
Understanding 10Be transport and deposition processes
i indispensable
is
i di p
bl for
f its
i application
ppli i as a p
paleo
l p
proxy!
y!
(1) Bartol Research Institute, 2010. http://neutronm.bartol.udel.edu/~pyle/bri_table.html
(2)
( ) BMU, 2011. Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit, d
f
l
h
d
k
h h
U
lt di kti ität d St hl b l t
J h b i ht 2001 2008
Umweltradioaktivität und Strahlenbelastung: Jahresberichte 2001‐2008.
(3) El ä
(3) Elsässer, C. et al. , 2011. Continuous 25‐years aerosol records at coastal Antarctica: Part C
l 2011 C i
25
l
d
lA
i P
2 V i bilit f th
2. Variability of the radionuclides 7Be, 10Be and 210Pb.
di
lid 7B 10B
d 210Pb Tellus 63B (in press).
T ll 63B (i
)
(4) Fi k l d Ni hii
(4) Finkel and Nishiizumi, 1997. Beryllium 10 concentrations in the Greenland Ice Sheet i 1997 B lli
10
t ti
i th G
l d I Sh t
Project 2 ice core from 3 40 ka Journ Geophys Res 102(C12)
Project 2 ice core from 3‐40 ka. Journ. Geophys. Res., 102(C12).
(5) Grootes et al., 1993. Comparison of oxygen isotope records from the GISP2 and GRIP
Greenland ice cores. Nature, 366, 552‐554. l d
(6)
Köhl
t l 2006 A
d l b di t
t ti
fl
f
h
i th
b
(6) Köhler et al. 2006. A model‐based interpretation of low‐frequency changes in the carbon cycle during the last 120000 years and ist implications for the reconstruction of l d i
h l 120000
d i i li i
f h
i
f
14
atmospheric Δ
t
h i Δ C . Geochem. Geophys. Geosyst., 7(11).
C G h
G
h G
t 7(11)
Neutron monitors of the Bartol Research Institute are supported by NSF grant ATM‐
N t
it
f th B t l R
h I tit t
t d b NSF
t ATM
0527878
0527878.
-4
4
1.6
model result (2001
(2001-2008)
2008)
1.4
PTB
((2))
22Na/
Fig. 5:
Fi
5
N /7Be
B
measured at PTB
Braunschweig (BMU,
2011)) and
d Vienna
Vi
(IUP
Heidelberg)
compared
to
preliminary
p
li i y model
d l
results
results.
(2001 2008)
(2001-2008)
1.2
1.0
08
0.8
06
0.6
7
20
IUP Heidelberg (2009/2010)
Na / Be
N
e [10 acctivvity
y ra
atio
o]
Holocene
30
A
Al pin
nee iccee cco
orree ffrro
om
m Mo
Montee R
Ro
osa rreegio
on
n
40
Radionuclide ratios are ideal tools to study transport
processes Primarily,
processes.
Primarily ratios of radionuclides which originate
from the same production process reduce meteorological
noise.
i In
I this
thi cases, transport
t
t processes such
h as Stratosphere‐
St t h
Troposphere Exchange may be sensitively quantified.
Troposphere‐Exchange
quantified Here,
Here
measurements of 22Na (cosmogenic; radioact. lifetime: 3.8
yyears)) might
ight substitute
b tit t expensive
p i 10Be
B measurements.
t
1.8
04
0.4
22
What may be learned from What
may be learned from
radionuclide
radionuclide ratios?
d
l d ratios??
50
[pe
er mill]
10
3
Be [10
B
0 at//g]
60
References:
References
10
1.0
• Stratosphere
Stratosphere‐Troposphere‐Exchange
Troposphere Exchange (STE) causes a remarkable seasonal cycle.
cycle Hence,
Hence the yearly average snow concentration of
10Be is sensitive to the seasonality of accumulation rate.
rate
• The production signal is clearly seen in air measurements but embedded in considerable meteorological noise.
7Be
• Differences
Diff
b t
between
B and
d 10Be
B callll for
f 10Be
B measurements
t on a global
l b l scale
l for
f validation
lid ti and
d use off global
l b l circulation
i l ti models.
d l
Be ice concentration
GISP ice core
30000
1.5
16
1.6
fails on the millennial
10
35000
Neumayer Station (Antarctica)
Major findings concerning 10Be
70
40000
1.6
1
6
1.4
1.2
10
1.0
08
0.8
0.6
Pb
IIndeed,
d d, 14C‐
C and
d 10Be‐based
B b d reconstructions
i
off p
past cosmogenic
g i
production rates agree fairly well on the centennial timescale (not
shown) – but they systematically deviate on the millennial timescale.
timescale
This
h mismatch
h is p
pointed
d out by
by Köhler
hl et al.l ((2006)) who
h simulated
l d
atmospheric 14C based on production rates obtained from 10Be (see
Fig 1) Even though Köhler et al.
Fig.1).
al (2006) applied a carbon‐cycle model
accounting for glacial
glacial‐interglacial
interglacial changes, they could not reproduce
th atmospheric
the
t
h i 14C variations.
i ti
10
0.8
7
210
7
and
(1)
10
10
D we understand
Do
Do we understand the d
d the
h Be ice core signal sufficiently well?
B ice
Be
i core signal
ig l sufficiently
ffi i ly well?
ll?
10Be
and
10Be?
neutron count rate
Although
Alth
h 10Be
B and
d the
th short
h t lived
li d 7Be
B underly
d l almost
l
t identical
id ti l production
d ti
processes their atmospheric behavior differs due to their different radioactive
processes,
lifetimes (10Be: 2x106 years; 7Be: 77days).
Cosmogenic radionuclides in climate archives basically allow
reconstructing past production rates and related solar and
geomagnetic
ti activity.
ti it However,
H
one has
h to
t understand
d t d the
th
climate driven hand‐over
climate‐driven
hand over of the atmospheric production
signal into the particular archives, modified by the
respective
p ti
ggeochemical
h i l cycles.
y l
Si
Since
th
these
cycles
y l
are
completely different for 10Be and 14C,
C an approach
combining timeseries of both radionuclides seems
promising.
p
ii g
Consistency of
timescale
7Be
0.9
02
0.2
00
0.0
O N
D J
F
M A
M J
J
A
S
IImproving our understanding of the past with measurements Improving
p i g our understanding
d t di g off the
th p
pastt with
ith measurements
t
of present‐day
of present
present day cosmogenic radionuclides day cosmogenic radionuclides
Atmospheric monitoring as well as modelling attempts help to study the sensitivtiy of ice core 10Be to climate modulations (i.e.
changes
h g in
i transport
t
p t and
d deposition).
d p iti ) However,
H
models
d l have
h
t be
to
b tied
ti d to
t measurements.
t Yet,
Y t there
th
are only
ly a few
f measurements
t off
10Be deposition and air‐concentration
air concentration available which are mainly restricted to polar areas.
areas A global aerosol sampling network might
help to answer the following questions with respect to the global 10Be cycle:
Is there a latitudinal dependence of atmospheric Is
there a latitudinal dependence of atmospheric 10Be concentration and of the Be concentration and of the 10Be/7Be ratio on the global scale?
Be ratio on the global scale?
What
is the shape of the expected seasonal cycle of atmospheric 10Be
(or 22Na)
in mid‐latitudes
or tropics?
What is the shape of the expected seasonal cycle of atmospheric Be (or Na) in mid
latitudes or tropics?
h
h gl b l d
b
f 10Be deposition?
d p
?
What is the global distribution of 10
7Be,
B 10Be
B
1.0
0
Be, B
B
Be co
onccentra
ation [normalizzed
d]
The IUP Heidelberg time series
1.1
7
Radionuclides in climate archives: R
Radionuclides
di
lid in
i climate
li
archives:
hi
A tool for reconstructing
A tool for reconstructing the past
re onstr tin the past
neu
n utro
on co
ount ra
ate
e [norm
ma
alize
ed]]
The benefit from atmospheric monitoring: Findings from The
h b
benefit
fi ffrom atmospheric
ph i monitoring:
i i g Findings
i di g from
f
N
Neumayer
Neumayer Station (Antarctica)
y Station
St ti (Antarctica)
(A
( t ti )