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

• Main Authors: Sinnl, Giulia, Adolphi, Florian, Christl, Marcus, Welten, Kees C., Woodruff, Thomas, Caffee, Marc, Svensson, Anders, Muscheler, Raimund, Rasmussen, Sune Olander
• Format: Text
• Language: English
• Published: 2022
• Subjects: Antarctic; Greenland; Hulu; Antarc*; Antarctica; Greenland ice core; ice core; North Atlantic
• Online Access: https://doi.org/10.5194/cp-2022-62; https://cp.copernicus.org/preprints/cp-2022-62/

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 10 Be 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 10 Be datasets, supported by lower-resolution radionuclide data from Greenland and 14 C in the Hulu Cave speleothem, representing a good synchronization candidate at around 22 ka b2k. By matching the respective 10 Be 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 ...