Solar and climate influences on ice core 10Be records from Antarctica and Greenland during the neutron monitor era

Abstract

Cosmogenic 10Be in polar ice cores is a primary proxy for past solar activity. However, interpretation of the 10Be record is hindered by limited understanding of the physical processes governing its atmospheric transport and deposition to the ice sheets. This issue is addressed by evaluating two accurately dated, annually resolved ice core 10Be records against modern solar activity observations and instrumental and reanalysis climate data. The cores are sampled from the DSS site on Law Dome, East Antarctica (spanning 1936–2009) and the Das2 site, southeast Greenland (1936–2002), permitting inter-hemispheric comparisons. Concentrations at both DSS and Das2 are significantly correlated to the 11-yr solar cycle modulation of cosmic ray intensity, rxy=0.54 with 95% CI [0.31; 0.70], and rxy=0.45 with 95% CI [0.22; 0.62], respectively. For both sites, if fluxes are used instead of concentrations then correlations with solar activity decrease. The strength and spectral coherence of the solar activity signal in 10Be is enhanced when ice core records are combined from both Antarctica and Greenland. The amplitudes of the 11-yr solar cycles in the 10Be data appear inconsistent with the view that the ice sheets receive only 10Be produced at polar latitudes. Significant climate signals detected in the 10Be series include the zonal wave three pattern of atmospheric circulation at DSS, rxy=−0.36 with 95% CI [−0.57; −0.10], and the North Atlantic Oscillation at Das2, rxy=−0.42 with 95% CI [−0.64; −0.15]. The sensitivity of 10Be concentrations to modes of atmospheric circulation advises caution in the use of 10Be records from single sites in solar forcing reconstructions.