Ob ti f t h i di lid l Th b fit f l b lObservations of atmospheric radionuclide cycles: The benefit for globalObservations of atmospheric radionuclide cycles: The benefit for globalObservations of atmospheric radionuclide cycles: The benefit for global p y gpaleoclimate st diespaleoclimate studiespaleoclimate studiespaleoclimate studies 

Christoph Elsässer (1) Dietmar Wagenbach (1) Rebecca Bremen (1) Ingeborg Levin (1) Rolf Weller (2) Clemens Schlosser (3) and Matthias Auer (4)Christoph Elsässer (1), Dietmar Wagenbach (1), Rebecca Bremen (1), Ingeborg Levin (1), Rolf Weller (2), Clemens Schlosser (3) and Matthias Auer (4)Christoph Elsässer (1), Dietmar Wagenbach (1), Rebecca Bremen (1), Ingeborg Levin (1), Rolf Weller (2), Clemens Schlosser (3) and Matthias Auer (4)(1) Institut für Umweltphysik, University of Heidelberg, Germany (christoph.elsaesser@iup.uni‐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 (christoph.elsaesser@iup.uni heidelberg.de), (2) Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany, (3)  Bundesamt für Strahlenschutz, Freiburg, Germany, (4) CTBTO P t C i i Vi I t ti l C t Vi A t i(4) CTBTO Preparatory Commission, Vienna International Center, Vienna, Austria 

h b fi f h i i i i di fThe benefit from atmospheric monitoring: Findings fromR di lid i li hi The benefit from atmospheric monitoring: Findings from Radionuclides in climate archives: p g gRadionuclides in climate archives: 

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processes their atmospheric behavior differs due to their different radioactive 1 0 tra

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ti ti it H h t d t d th lifetimes (10Be: 2x106 years; 7Be: 77days). onc

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Consistency of 10Be and 14C fails on the millennial J F M A M J J A S O N D J F M A MJ J J S O J

Consistency of 10Be and 14C fails on the millennialMajor findings concerning 10Betimescale Major findings concerning Betimescale• Stratosphere Troposphere Exchange (STE) causes a remarkable seasonal cycle Hence the yearly average snow concentration ofI d d 14C d 10B b d i f i • Stratosphere‐Troposphere‐Exchange (STE) causes a remarkable seasonal cycle. Hence, the yearly average snow concentration ofIndeed, 14C‐ and 10Be‐based reconstructions of past cosmogenic

10Be is sensitive to the seasonality of accumulation rate, p g

production rates agree fairly well on the centennial timescale (not Be is sensitive to the seasonality of accumulation rate.production rates agree fairly well on the centennial timescale (not• The production signal is clearly seen in air measurements but embedded in considerable meteorological noise.shown) – but they systematically deviate on the millennial timescale The production signal is clearly seen in air measurements but embedded in considerable meteorological noise.Diff b t 7B d 10B ll f 10B t l b l l f lid ti d f l b l i l ti d l

shown) but they systematically deviate on the millennial timescale.h h d b hl l ( ) h l d • Differences between 7Be and 10Be call for 10Be measurements on a global scale for validation and use of global circulation models.This mismatch is pointed out by Köhler et al. (2006) who simulatedp y ( )atmospheric 14C based on production rates obtained from 10Be (seeatmospheric 14C based on production rates obtained from 10Be (seeFig 1) Even though Köhler et al (2006) applied a carbon‐cycle model Fig.1). Even though Köhler et al. (2006) applied a carbon‐cycle model

accounting for glacial‐interglacial changes, they could not reproduce What may be learned from 1.8accounting for glacial interglacial changes, they could not reproduceth t h i 14C i ti What may be learned from IUP Heidelberg (2009/2010) the atmospheric 14C variations. What may be learned from  1.6 model result (2001-2008)

d l d ? Fi 5 22N /7Bmodel result (2001 2008)

PTB (2) (2001 2008)radionuclide ratios? Fig. 5: 22Na/7Be 1.4o]

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Fig 1: Simulated atmospheric Δ14C modified after Köhler Troposphere‐Exchange may be sensitively quantified. Here, p yresultsre

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Fig. 1: Simulated atmospheric Δ C modified after Köhlerl [2006] measurements of 22Na (cosmogenic; radioact. lifetime: 3.8 results.r-44low 0.2

et al. [2006]. measurements of Na (cosmogenic; radioact. lifetime: 3.8) i ht b tit t i 10B ta  δ18O

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high Improving our understanding of the past with measurements10Be is sensitive to aerosol transport and deposition. Fig. 2 Mo

-32high Improving our understanding of the past with measurements Be is sensitive to aerosol transport and deposition. Fig. 2

l l ill h li d l i f 10B i

M40000 35000 30000 25000 20000 15000 10000 5000 0 p g g pclearly illustrates the climate modulation of a 10Be ice core m

 40000 35000 30000 25000 20000 15000 10000 5000 0age [BP]

of present day cosmogenic radionuclidesy

signal The challenge to disentagle the production signal om

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of present‐day cosmogenic radionuclidessignal. The challenge to disentagle the production signal rodata from Finkel and Nishiizumi, 1997; Grootes et al., 1993 of present day cosmogenic radionuclides from climate modulations is not sufficiently solved yet fr

Fi 2 10B t ti i th GISP i t t d tfrom climate modulations is not sufficiently solved, yet.

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Fig. 2: 10Be concentration in the GISP ice core contrasted to Understanding 10Be transport and deposition processes Atmospheric monitoring as well as modelling attempts help to study the sensitivtiy of ice core 10Be to climate modulations (i.e.regthe respective δ18O record which basically indicates variations

Understanding Be transport and deposition processesi i di bl f i li i l !

Atmospheric monitoring as well as modelling attempts help to study the sensitivtiy of ice core Be to climate modulations (i.e.h i t t d d iti ) H d l h t b ti d t t Y t th l f t forthe respective δ18O record which basically indicates variations is indispensable for its application as a paleo proxy! changes in transport and deposition). However, models have to be tied to measurements. Yet, there are only a few measurements ofco

in temperature and associated accumulation rate changesp pp p p y g p p y

10Be deposition and air concentration available which are mainly restricted to polar areas A global aerosol sampling network mighte c

in temperature and associated accumulation rate changes. 10Be deposition and air‐concentration available which are mainly restricted to polar areas. A global aerosol sampling network mightce help to answer the following questions with respect to the global 10Be cycle:ic help to answer the following questions with respect to the global Be cycle:

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Is there a latitudinal dependence of atmospheric 10Be concentration and of the 10Be/7Be ratio on the global scale?ne Is there a latitudinal dependence of atmospheric 10Be concentration and of the 10Be/7Be ratio on the global scale?References

(1) Bartol Research Institute, 2010. http://neutronm.bartol.udel.edu/~pyle/bri_table.html( ) d f l h d k h h

in(5)  Grootes et al., 1993. Comparison of oxygen isotope records from the GISP2 and GRIPl d What is the shape of the expected seasonal cycle of atmospheric 10Be (or 22Na) in mid‐latitudes or tropics?References: (2) BMU, 2011. Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit, 

U lt di kti ität d St hl b l t J h b i ht 2001 2008

pGreenland ice cores. Nature, 366, 552‐554. (6) Köhl t l 2006 A d l b d i t t ti f l f h i th b What is the shape of the expected seasonal cycle of atmospheric  Be (or  Na) in mid latitudes or tropics?

h h l b l d b f 10 d ?Umweltradioaktivität und Strahlenbelastung: Jahresberichte 2001‐2008.

(3) El ä C l 2011 C i 25 l d l A i P Al(6)  Köhler et al. 2006. A model‐based interpretation of low‐frequency changes in the carbon  

l d i h l 120000 d i i li i f h i f What is the global distribution of 10Be deposition?(3)   Elsässer, C. et al. , 2011. Continuous 25‐years aerosol records at coastal Antarctica: Part 2 V i bilit f th di lid 7B 10B d 210Pb T ll 63B (i )

Acycle during the last 120000 years and ist implications for the reconstruction of t h i Δ14C G h G h G t 7(11)

g p2. Variability of the radionuclides 7Be, 10Be and 210Pb. Tellus 63B (in press).

(4) Fi k l d Ni hii i 1997 B lli 10 t ti i th G l d I Sh tatmospheric Δ14C . Geochem. Geophys. Geosyst., 7(11).

N t it f th B t l R h I tit t t d b NSF t ATM(4)   Finkel and Nishiizumi, 1997. Beryllium 10 concentrations in the Greenland Ice Sheet  Project 2 ice core from 3 40 ka Journ Geophys Res 102(C12)

Neutron monitors of the Bartol Research Institute are supported by NSF grant ATM‐0527878Project 2 ice core from 3‐40 ka. Journ. Geophys. Res., 102(C12). 0527878.