Solar and climate signals revealed by seasonal ¹⁰Be data from the NEEM ice core project for the neutron monitor period

Summary, in English

¹⁰Be in ice cores has been instrumental for reconstructing past changes in solar activity prior to direct observations. For a robust use of these records, it is pivotal to understand the ¹⁰Be transport and deposition. However, there are only few high-resolution seasonal ¹⁰Be data longer than one full solar cycle (11 years) that could enable a quantification of the influences of atmospheric circulation and deposition processes on the ¹⁰Be signal in ice. Here we present a seasonally resolved ¹⁰Be data set covering the neutron monitor period (1951–2002) from a firn core connected to the NEEM (North Greenland Eemian Ice Drilling) project. The results suggest that both summer and winter ¹⁰Be reflect the production signal induced by solar modulation of galactic cosmic rays. However, superimposed on this solar signal we find additional meteorologically driven influences on ¹⁰Be transport and deposition. We found that the tropopause pressure over 30°N represents an important factor influencing NEEM ¹⁰Be concentrations on seasonal and annual scales. ¹⁰Be deposited in summer also correlates significantly with the tropopause pressure over Greenland suggesting a direct contribution of stratospheric intrusions during summer to the ¹⁰Be deposition in Greenland. To correct for these transport/deposition influences, we apply a first-order correction to the ¹⁰Be data using a multi-linear regression model. The “climate-corrected” ¹⁰Be data shows a comparable skill for reconstructing production rate changes as the ¹⁰Be composite record from five different ice cores in Greenland. The results suggest that the correction approach can be a complementary method to the stacking to better isolate the production rate signal from the ¹⁰Be data when only limited data are available.

• Author: Minjie Zheng; Florian Adolphi; Jesper Sjolte; Ala Aldahan; Göran Possnert; Mousong Wu; Peng Chen; Raimund Muscheler
• Department/s: Quaternary Sciences; MERGE: ModElling the Regional and Global Earth system
• Publishing year: 2020
• Language: English
• Publication/Series: Earth and Planetary Science Letters
• Volume: 541
• Links: http://dx.doi.org/10.1016/j.epsl.2020.116273
• Document type: Journal article
• Publisher: Elsevier
• Topic: Climate Research; Geosciences, Multidisciplinary
• Keywords: climate and solar signal; cosmogenic radionuclides; NEEM firn core; seasonally resolved Be
• Status: Published
• Project: Disentangling climate influence and production rate on 10Be deposition in the polar region over the last 150 yrs; Disentangling production and climate signals from high-resolution Beryllium records: implications for solar and geomagnetic reconstructions
• ISBN/ISSN/Other: ISSN: 0012-821X