Latitude-dependent sensitivity of 10Be records to variations in geomagnetic field intensity

The atmospheric production rate of cosmogenic ¹⁰Be is inversely related to the geomagnetic field strength. This leads to variable deposition rates of ¹⁰Be in environmental archives, such as ice or sediment cores. ¹⁰Be records from these archives can, therefore, be used to reconstruct past intensities of the geomagnetic field. Recent ¹⁰Be production and atmospheric mixing models, however, suggest that the sensitivity of ¹⁰Be records to changes in the geomagnetic field intensity depends on the latitude. This impacts the use of single-site ¹⁰Be records for reconstructing global ¹⁰Be production rates and, therefore, geomagnetic field intensities.

Here, we quantitatively assess the latitudinal sensitivity of ¹⁰Be deposition to geomagnetic field changes. We present new authigenic ¹⁰Be/⁹Be data from a sediment core from the Bay of Bengal (IODP U1446) and compile additional ¹⁰Be data from ice and sediment cores. Our analysis focuses on ¹⁰Be deposition changes during the Laschamps geomagnetic field intensity minimum at different latitudes. We compare ¹⁰Be deposition changes with changes in modeled ¹⁰Be production from geomagnetic field reconstructions (LSMOD.2, GGFSS70, Black Sea, GLOPIS-75) and the GEOS-Chem atmospheric mixing model.

Our findings reveal that ¹⁰Be deposition changes are larger in the tropics (tropical enhancement) and diminish at higher latitudes (polar bias), indicating incomplete mixing of cosmogenic beryllium, consistent with atmospheric mixing models. This latitudinal sensitivity needs to be taken into account when reconstructing variations in global geomagnetic field intensity from ¹⁰Be.