10Be in the South Pole Ice Core - A Late Holocene Solar Variability Record

Abstract:

The production of 10Be in the atmosphere in the high latitudes is modulated by solar variability. Time-series records of 10Be from ice cores therefore provide important information on variations in solar activity through time, which is fundamental to understanding climate variability. However, deposition of 10Be to the ice surface is also influenced by variability in atmospheric circulation and deposition processes, and thus, many 10Be ice core records remain difficult to interpret.

South Pole is arguably the best available location for minimizing the influence of variable atmospheric circulation on 10Be deposition. The single existing 10Be record from South Pole covers the last millennium and ends in CE 1982.

We here present a new South Pole 10Be record from the late Holocene, together with examplary measurements from the last glacial period, complemented by climate modeling experiments of atmospheric ¹⁰Be production, transport and deposition physics. Our model simulations of both internannual variablity and glacial vs. interglacial ¹⁰Be production, transport and deposition indicate that 10Be in South Pole snow is robust even to significant climate changes, suggesting that the measured 10Be primarily reflect changes of solar activity over that period.

Our continuous one-meter resolution ¹⁰Be record from South Pole covers so far the last three millennia. The ¹⁰Be data from the last millennium agree well with the existing ¹⁰Be record by Raisbeck et al. (1990), and matches the historic sunspot records strikingly, providing a robust calibration between sunspot number and ¹⁰Be deposition.

Here, we present new data of ¹⁰Be deposition to South Pole and the implications for the underlying solar variability over prominent climate intervals refered to as ‘The Roman Warm Period’, the Dark Ages’, ‘the Medieval Warm Period’, ‘the Little Ice Age’ and the last 160 years.