Study of the Solar Forcing over the Holocene from a new Dome C Ice Core

Solar forcing is one of the main natural climate forcings with greenhouse gas emissions, insolation or volcanic forcing. During the last millennium, solar minima often coincide with periods of enhanced volcanic forcing, making the attribution of climate variations to one or the other cause ambiguous (IPCC, 2013) ; this should not be the case for earlier millenia and it has to be tested on expanded records. In addition, the information collected on the variation of solar forcing in the past until today, can be used in climate models and allow to better constrain the part of the current climate change that is of natural origin and that of anthropogenic origin. There are various indicators of solar activity such as irradiance values measured by satellite for 30 years, sunspots observed on the Sun’s surface since the early 17th century but for longer timescales, only cosmogenic isotopes such as beryllium-10 (10Be) can provide information on past solar activity. The objective of this project is to propose a new reconstruction of solar activity during the Holocene, our current interglacial. This reconstruction will be based on a 10Be record at high resolution obtained from a new 350 m ice core drilled on the Concordia-Dome C site. In order to make a reference of this record, we will implement a multiproxy approach at a resolution rarely achieved in the past. Many data will be collected to characterize the evolution of the past atmospheric composition (carbon monoxide and methane), the variation of local temperature, humidity sources, volcanic forcing, biomass burning, the dust sources and the origin of air masses that reach Concordia-Dome C. Because of an accumulation of troubles with the two drillers used on the field, it was not possible to reach 350m but instead 215 m. A supplementary season in 2017/2018, will be necessary to reach the initial objective using the same drilling hole and the James Ross driller that is going to be repaired at the LGGE.