DOI: 10.25921/24bm-6987
title: NOAA/WDS Paleoclimatology - Cosmogenic Radionuclides Atmospheric Transport Model Output

description: All existing 10Be records from Greenland and Antarctica show increasing concentrations during the Maunder Minimum period (MM), 1645-1715, when solar activity was very low and the climate was colder (little ice age). In detail, however, the 10Be records deviate from each other. We investigate to what extent climatic changes influence the 10Be measured in ice by modeling this period using theECHAM5-HAM general circulation model. Production calculations show that during the MM the mean global 10Beproduction was higher by 32% than at present due to lower solar activity. Our modeling shows that the zonally averaged modeled 10Be deposition flux deviates by only ~8% from the average increase of 32%, indicating that climatic effects are much smaller than the production change. Due to increased stratospheric production, the 10Be content in the downward fluxes is larger during MM, leading to larger 10Be deposition fluxes in the subtropics, where stratosphere-troposphere exchange(STE) is strongest. In polar regions the effect is small. In Greenland the deposition change depends on latitude and altitude. In Antarctica the change is larger in the east than in the west. We use the 10Be/7Be ratio to study changes in STE. We find larger change between 20N-40N during spring, pointing to a stronger STE in the Northern Hemisphere during MM. In the Southern Hemisphere the change is small. These findings indicate that climate changes do influence the 10Be deposition fluxes, but not enough to significantly disturb the production signal. Climate-induced changes remain small, especially in polar regions.
description: Model results for the atmospheric transport of cosmogenic radionuclides 
Be-10, Be-7, Cl-36 performed using the ECHAM5-HAM general circulation 
model, developed at the Max-Planck-Institute for Meteorology 
(http://www.mpimet.mpg.de/). Please refer to Heikkilä, U., J. Beer, and J. Feichter. 2008. Modeling cosmogenic radionuclides 10Be and 7Be during the Maunder Minimum using the ECHAM5-HAM General Circulation Model. Atmospheric Chemistry and Physics, 8, 2797-2809. doi:10.5194/acp-8-2797-2008, for a detailed description of the data.


Data from the following experiments is available: 

1) The simulated bomb test peak of Chlorine-36 during the years 
   1952-1972. See  Heikkilä, U., Beer, J., Feichter, J., Alfimov, V., Synal, H.-A., Schotterer, U., Eichler, A., Schwikowski, M., and Thompson, L.: 36Cl bomb peak: comparison of modeled and measured data, Atmos. Chem. Phys., 9, 4145-4156, doi:10.5194/acp-9-4145-2009, 2009.

Available files: 
cl36_air_conc_1952-1972_monthly.nc 
- monthly mean Cl-36 atmospheric concentrations (atoms/kg) 
  at 39 model levels up to 0.01 hPa (ca. 80 km). 
  (Note: large file, 329MB) 
  (Note: data for March 1959 are not present in this file) 


cl36_flux_1952-1972_monthly.nc 
cl36_flux_1952-1972_annual.nc 
- monthly and annual mean Cl-36 atmospheric deposition fluxes (atoms/m2/s). 


2) Simulated atmospheric deposition fluxes of Beryllium-10, Beryllium-7 
   and Lead-210 for two different periods: 1986-1990 (present day conditions) 
   and 1705-1709 (Maunder Minimum of the Little Ice Age). 
   See Heikkilä et al. 2008. More information on the simulation of Lead-210 
   can be found in Heikkilä, Ulla. Modeling of the atmospheric transport of the cosmogenic radionuclides ¹⁰Be and ⁷Be using the ECHAM5-HAM general circulation model. ETH (2007), http://e-collection.library.ethz.ch/view/eth:30179. 

Available files: 
be10_be7_pb210_flux_1986-1990_monthly.nc 
be10_be7_pb210_flux_1986-1990_annual.nc 
be10_be7_pb210_flux_1705-1709_monthly.nc 
be10_be7_pb210_flux_1705-1709_annual.nc 
 
- monthly and annual mean atmospheric deposition fluxes (atoms/m2/s) 
  of Be-10, Be-7 and Pb-210 and the total precipitation rate (mm/day). 

3) Simulated atmospheric deposition fluxes of Beryllium-10 
   and Beryllium-7 for the period of 1998-2003. (Heikkilä, U., J. Beer, and J. Feichter. 2008. Modeling cosmogenic radionuclides 10Be and 7Be during the Maunder Minimum using the ECHAM5-HAM General Circulation Model. Atmospheric Chemistry and Physics, 8, 2797-2809. doi:10.5194/acp-8-2797-2008). 

Available files: 
be10_be7_flux_1998-2003_monthly.nc 
be10_be7_flux_1998-2003_annual.nc 

- monthly and annual mean atmospheric deposition fluxes (atoms/m2/s) 
  of Be-10 and Be-7 and the total precipitation rate (mm/day). 


Model output is in netCDF format (http://www.unidata.ucar.edu/software/netcdf/)