Solar activity over nine millennia: A consistent multi-proxy reconstruction

Abstract

Aims. The solar activity in the past millennia can only be reconstructed from cosmogenic radionuclide proxy records in terrestrial archives. However, because of the diversity of the proxy archives, it is difficult to build a homogeneous reconstruction. All previous studies were based on individual, sometimes statistically averaged, proxy datasets. Here we aim to provide a new consistent multiproxy reconstruction of the solar activity over the last 9000 years, using all available long-span datasets of 10 Be and 14 C in terrestrial archives. Methods. A new method, based on a Bayesian approach, was applied for the first time to solar activity reconstruction. A Monte Carlo search (using the χ 2 statistic) for the most probable value of the modulation potential was performed to match data from different datasets for a given time. This provides a straightforward estimate of the related uncertainties. We used six 10 Be series of different lengths (from 500-10000 years) from Greenland and Antarctica, and the global 14 C production series. The 10 Be series were resampled to match wiggles related to the grand minima in the 14 C reference dataset. The stability of the long data series was tested.Results. The Greenland Ice-core Project (GRIP) and the Antarctic EDML (EPICA Dronning Maud Land) 10 Be series diverge from each other during the second half of the Holocene, while the 14 C series lies in between them. A likely reason for the discrepancy is the insufficiently precise beryllium transport and deposition model for Greenland, which leads to an undercorrection of the GRIP series for the geomagnetic shielding effect. A slow 6-7-millennia variability with lows at ca. 5500 BC and 1500 AD in the longterm evolution of solar activity is found. Two components of solar activity can be statistically distinguished: the main component, corresponding to the 'normal' moderate level, and a component corresponding to grand minima. A possible existence of a component representing grand maxima is indicated, but it cannot be separated from the main component in a statistically significant manner. Conclusions.A new consistent reconstruction of solar activity over the last nine millennia is presented with the most probable values of decadal sunspot numbers and their realistic uncertainties. Independent components of solar activity corresponding to the main moderate activity and the grand-minimum state are identified; they may be related to different operation modes of the dynamo.

Persistent Draining of the Stratospheric 10Be Reservoir After the Samalas Volcanic Eruption (1257 CE)

“…The cosmogenic nuclide of beryllium 10 ( 10 Be) measured in ice cores is an indirect proxy for past solar activity (e.g., Bard et al, 1997;Beer et al, 1990;Berggren et al, 2009;Cauquoin et al, 2014;Delaygue & Bard, 2011;Horiuchi et al, 2008;Raisbeck et al, 1990;Steinhilber et al, 2012;Wu et al, 2018) and for geomagnetic excursions or reversals (e.g., Beer et al, 1988;Finkel & Nishiizumi, 1997;Raisbeck et al, 2017Raisbeck et al, , 2006Yiou et al, 1997). In the atmosphere it is produced from spallation reactions on oxygen and nitrogen atoms induced by primary cosmic rays, whose flux is modulated by the magnetic fields of the Earth and the Sun.…”

The movements of Alpine glaciers throughout the last 10,000 years as sensitive proxies of temperature and climate changes

“…In general, it seems that some amplifying terrestrial effect are needed to explain the magnitude of the observed glacier movements. It has to be seen whether the recent detailed analysis of solar activity [50] will allow one to draw more definite conclusions about the influence of the sun on the glacier movement during the Holocene.…”

Is there evidence for a 4.2 ka BP event in the northern North Atlantic region?

“…Subsequently, Bond et al (2001) argued that these colder episodes were driven by changes in solar insolation (cf. Wanner and Bütikofer, 2008;Wanner et al, 2011), notwithstanding the fact that total solar irradiance did not vary by more than ±0.15% over this period (Vieira et al, 2011;Roth and Joos, 2013;Wu et al 2018). Other paleoceanographic studies have been unable to reproduce the record of ice-rafting reported in Bond et al, (1997) (e.g.…”