13 Sep 2022
13 Sep 2022
Status: this preprint is currently under review for the journal CP.

Synchronizing ice-core and U/Th time scales in the Last Glacial Maximum using Hulu Cave 14C and new 10Be measurements from Greenland and Antarctica

Giulia Sinnl1, Florian Adolphi3, Marcus Christl6, Kees C. Welten4, Thomas Woodruff5, Marc Caffee5, Anders Svensson1, Raimund Muscheler2, and Sune Olander Rasmussen1 Giulia Sinnl et al.
  • 1Physics of Ice, Climate, and Earth, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
  • 2Quaternary Sciences, Department of Geology, Lund University, Lund, Sweden
  • 3Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
  • 4Space Sciences Laboratory, University of California, Berkeley, California, USA
  • 5Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana, USA
  • 6Laboratory of Ion Beam Physics, ETH Zurich, Zurich, Switzerland

Abstract. Between 15 and 27 ka b2k (thousands of years before 2000 CE) during the last glacial, Greenland experienced a prolonged cold stadial phase, interrupted by two short-lived warm interstadials. Greenland ice-core calcium data show two periods, preceding the interstadials, of anomalously high atmospheric dust loading, the origin of which is not well understood. At approximately the same time as the Greenland dust peaks, the Chinese Hulu Cave speleothems exhibit a climatic signal suggested to be a response to Heinrich Event 2, a period of enhanced ice-rafted debris deposition in the North Atlantic. In the climatic signal of Antarctic ice cores, moreover, a relative warming occurs between 23 and 24.5 ka b2k that is generally interpreted as a counterpart to a cool climate phase in the Northern Hemisphere. Proposed centennial-scale offsets between the polar ice-core time scales and the speleothem time scale hamper the precise reconstruction of the global sequence of these climatic events. Here, we examine two new 10Be datasets from Greenland (NorthGRIP) and Antarctic (WDC) ice cores to test the agreement between different time scales, by taking advantage of the globally synchronous cosmogenic radionuclide production rates.

Evidence of an event similar to the Maunder Solar Minimum is found in the new 10Be datasets, supported by lower-resolution radionuclide data from Greenland and 14C in the Hulu Cave speleothem, representing a good synchronization candidate at around 22 ka b2k. By matching the respective 10Be data, we determine the offset between the Greenland ice-core time scale, GICC05, and the WDC Antarctic time scale, WD2014, to be 125±40 years. Furthermore, via radionuclide wiggle-matching, we determine the offset between the Hulu speleothem and ice core timescales to be 375 years for GICC05 (75–625 years at 68 % confidence), and 225 years for WD2014 (-25–425 years at 68 % confidence). The rather wide uncertainties are intrinsic to the wiggle-matching algorithm and the limitations set by data resolution. The undercounting of annual layers in GICC05 inferred from the offset is hypothesized to have been caused by a combination of underdetected annual layers, especially during periods with low winter precipitation, and misinterpreted unusual patterns in the annual signal, during the extremely cold period often referred to as Heinrich Stadial 1.

Giulia Sinnl et al.

Status: open (until 08 Nov 2022)

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Giulia Sinnl et al.

Giulia Sinnl et al.


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Short summary
The record of past climate is preserved by several archives from different regions, such as ice cores from Greenland or Antarctica, or speleothems from caves such as the Hulu Cave in China. In this study, these archives are aligned by taking advantage of the globally synchronous production of cosmogenic radionuclides. This produces a new perspective on the global climate in the period between 20 and 25 thousand years ago.