Solar influences on climate during the last and penultimate glacial

• Applicants: Professor Dr. Helge W. Arz; Dr. Markus Czymzik
• Subject Area: Palaeontology
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 429518574

The Sun is the main energy source of Earth’s climate system. Total solar irradiance varies by ~1 W m-2 throughout the 11-year solar ‘Schwabe’ cycle. Regardless of this small energetic change, numerous meteorological observations, paleoclimate reconstructions and climate model results point to substantial solar influences on climate, on time-scales from years to millennia, modified by a complex interplay of climate forcings and boundary conditions. Despite the diversity of information, a comprehensive understanding of Sun-climate linkages is still limited. Main cause is the nearly exclusive limitation of existing Sun-climate studies to the climatologically comparably stable Holocene.Cosmogenic radionuclides like 10Be and 14C are produced in Earth’s upper atmosphere by incident galactic cosmic rays. The production rate of these isotopes is, in turn, modified by varying solar and geomagnetic shielding of galactic cosmic rays. Therefore, deposited in natural environmental archives, 10Be and 14C provide proxy records of both solar variability and Earth’s magnetic field strength. During the recent decades cosmogenic radionuclide records were routinely measured from trees and ice cores. However, these archives do not carry a paleomagnetic signal, adding uncertainty to existing solar variability reconstructions. Moreover, well-dated 14C records from trees are limited to the last 14000 years and ice core 10Be time-series lose temporal resolution back in time due to lateral ice flow. Sediment records can provide independent records of both, 10Be production and geomagnetic field strength far into the past, without losing temporal resolution. Within this proposal, we aim at establishing novel proxy records of solar variability applying paired 10Be and paleointensity measurements from Black Sea sediments at 40-year resolution for parts of the last and penultimate glacial. We will provide the first 10Be records from marine sediments at a sufficient resolution for multi-decadal solar variability reconstruction. A multi-layer approach including (1) regression analysis with proxy records, (2) modelled 10Be from paleointensity data and (3) 9Be normalization, all from the same Black Sea sediment cores, as well as (4) multi-radionuclide record comparisons will allow us to distinguish solar from geomagnetic and environmental effects on 10Be deposition. Ultimate goal of the research is the investigation of solar influences on climate during full Last Glacial Maximum conditions (22-28 ka BP), a period of distinct Dansgaard-Oeschger variability (40-55 ka BP) and Termination II (128-134 ka BP), based on systematic comparisons of our novel solar variability records with paleoclimate time-series directly from Black Sea sediments and from around the globe. The work will improve our knowledge about spatial and temporal patterns of Sun-climate linkages and allow us to better anticipate Sun’s role within the anthropogenic 21st century climate change.

• DFG Programme: Research Grants