A reconstruction of radiocarbon production and total solar irradiance from the Holocene &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C and CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; records: implications of data and model uncertainties

R Roth,F Joos

doi:10.5194/cp-9-1879-2013

Abstract

Abstract. Radiocarbon production, solar activity, total solar irradiance (TSI) and solar-induced climate change are reconstructed for the Holocene (10 to 0 kyr BP), and TSI is predicted for the next centuries. The IntCal09/SHCal04 radiocarbon and ice core CO2 records, reconstructions of the geomagnetic dipole, and instrumental data of solar activity are applied in the Bern3D-LPJ, a fully featured Earth system model of intermediate complexity including a 3-D dynamic ocean, ocean sediments, and a dynamic vegetation model, and in formulations linking radiocarbon production, the solar modulation potential, and TSI. Uncertainties are assessed using Monte Carlo simulations and bounding scenarios. Transient climate simulations span the past 21 thousand years, thereby considering the time lags and uncertainties associated with the last glacial termination. Our carbon-cycle-based modern estimate of radiocarbon production of 1.7 atoms cm−2 s−1 is lower than previously reported for the cosmogenic nuclide production model by Masarik and Beer (2009) and is more in-line with Kovaltsov et al. (2012). In contrast to earlier studies, periods of high solar activity were quite common not only in recent millennia, but throughout the Holocene. Notable deviations compared to earlier reconstructions are also found on decadal to centennial timescales. We show that earlier Holocene reconstructions, not accounting for the interhemispheric gradients in radiocarbon, are biased low. Solar activity is during 28% of the time higher than the modern average (650 MeV), but the absolute values remain weakly constrained due to uncertainties in the normalisation of the solar modulation to instrumental data. A recently published solar activity–TSI relationship yields small changes in Holocene TSI of the order of 1 W m−2 with a Maunder Minimum irradiance reduction of 0.85 ± 0.16 W m−2. Related solar-induced variations in global mean surface air temperature are simulated to be within 0.1 K. Autoregressive modelling suggests a declining trend of solar activity in the 21st century towards average Holocene conditions.

Highlights

Solid EarthSolar insolation is the driver of the climate system of the earth (e.g. Gray et al, 2010; Lockwood, 2012)
We combine our production record Q with estimates of virtual axis dipole moment (VADM) to compute the solar modulation potential with the help of the model output from Masarik and Beer (1999) which gives the slope in the Q − space for a given value of VADM
Converting the local interstellar spectrum (LIS) used for US11 to the one used by Castagnoli and Lal (1980) according to Herbst et al (2010) yields an average solar modulation potential of = 403 MeV during our calibration epoch 1937–1950 AD

Summary

Introduction

Solid EarthSolar insolation is the driver of the climate system of the earth (e.g. Gray et al, 2010; Lockwood, 2012). Solar insolation is the driver of the climate system of the earth Solar activity and TSI were reconstructed from the Holocene radiocarbon record. These reconstructions relied on box models of the ocean and land carbon cycle or on a 2-D representation of the ocean (Solanki et al, 2004; Marchal, 2005; Usoskin and Kromer, 2005; Vieira et al, 2011; Steinhilber et al, 2012). A quantification of how past changes in climate and the carbon cycle affect reconstructions of radiocarbon production and solar activity is yet missing. Aspects neglected in earlier studies include (i) changes in the climate– carbon-cycle system over the last glacial termination

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Conclusion