Connecting the Greenland ice-core and U∕Th timescales via cosmogenic radionuclides: testing the synchroneity of Dansgaard–Oeschger events

Abstract

Abstract. During the last glacial period Northern Hemisphere climate was characterized by extreme and abrupt climate changes, so-called Dansgaard–Oeschger (DO) events. Most clearly observed as temperature changes in Greenland ice-core records, their climatic imprint was geographically widespread. However, the temporal relation between DO events in Greenland and other regions is uncertain due to the chronological uncertainties of each archive, limiting our ability to test hypotheses of synchronous change. In contrast, the assumption of direct synchrony of climate changes forms the basis of many timescales. Here, we use cosmogenic radionuclides (10Be, 36Cl, 14C) to link Greenland ice-core records to U∕Th-dated speleothems, quantify offsets between the two timescales, and improve their absolute dating back to 45 000 years ago. This approach allows us to test the assumption that DO events occurred synchronously between Greenland ice-core and tropical speleothem records with unprecedented precision. We find that the onset of DO events occurs within synchronization uncertainties in all investigated records. Importantly, we demonstrate that local discrepancies remain in the temporal development of rapid climate change for specific events and speleothems. These may either be related to the location of proxy records relative to the shifting atmospheric fronts or to underestimated U∕Th dating uncertainties. Our study thus highlights the potential for misleading interpretations of the Earth system when applying the common practice of climate wiggle matching.

An ~130 kyr Record of Surface Water Temperature and δ18O From the Northern Bay of Bengal: Investigating the Linkage Between Heinrich Events and Weak Monsoon Intervals in Asia

“…In contrast, the reduction in monsoon intensity during Heinrich events H3 and H10 was most probably rather weak as reflected by relatively small positive peaks in the δ 18 O sw‐ivc record (Figure ). The synchroneity between WMIs and Heinrich events throughout the last glacial period has previously been observed in several other paleomonsoon records (e.g., Cheng et al, ; Colin et al, ; Deplazes et al, ; Kathayat et al, ; Mingram et al, ; Mohtadi et al, ; Stager et al, ; Wang et al, ) and recently been proven by connecting Greenland ice core and Asian speleothem chronologies via cosmogenic radionuclides (Adolphi et al, ). However, although WMIs can therefore be considered as the regional Asian response to cold spells in the North Atlantic realm, the teleconnective mechanism that links the two regions is still debated.…”

Robust Characteristics of the Laschamp and Mono Lake Geomagnetic Excursions: Results From Global Field Models

“…As two lows are also seen in GGF100k and directly in a number of RPI records ( Figure S7) the younger low is real and not due to modeling edge-effects near the end of our time interval. Note also that two production rate maxima are found in cosmogenic isotope records at about these times (e.g., Wagner et al, 2000;Adolphi et al, 2018), also indicating two intervals of globally low magnetic field intensity. We find transitional VGPs and P i ≥0.5 in only a few regions and not globally during these two times (see sections 4.5, 4.6), which we propose to be two separate excursions with nonglobal directional surface signatures.…”

Decadal-scale progression of the onset of Dansgaard–Oeschger warming events

“…During the glacial conditions, the westerly jet was located further south than today, leading to more frequent or even permanent conditions for dust emission (Chiang et al, 2015;Nagashima et al, 2011). As lowlatitude proxy records indicate northward movements of the ITCZ during the DO events (Wang et al, 2004;Deplazes et al, 2013;Wang et al, 2008;Yancheva et al, 2007), synchronous within approximately 180 years (Adolphi et al, 2018), we hypothesize that the accompanying change in atmospheric circulation causes a reduction of the dust deflation during interstadials. Because the reduction in mineral dust aerosol concentrations in the ice core occurs before the reduction in sea-salt aerosol, the data imply that this change in atmospheric circulation happens before the reduction in the sea-ice cover in the North Atlantic.…”

“…In the lower latitudes, speleothem and sediment records from both South America (Wang et al, 2004;Deplazes et al, 2013) and eastern Asia (Wang et al, 2008) indicate a northward displacement of the Intertropical Convergence Zone (ITCZ) at the time of DO warming (Cheng et al, 2012) resulting in rapid changes in tropical hydroclimate and methane emissions from the tropical wetlands (Baumgartner et al, 2014). A recent synchronization of cosmogenic radionuclide records from ice cores and low-latitude speleothems back to 45 kyr ago shows that atmospheric circulation changes in the tropics occurred synchronously with the Greenland warming within the cross-dating uncertainties of around 180 years (Adolphi et al, 2018). The atmospheric circulation changes associated with the Asian monsoon systems documented in the Asian speleothems also reduced the mobilization and export of mineral dust aerosol from the central Asian deserts during the warm stadial periods as documented by downstream sediment records (Porter and Zhisheng, 1995;Jacobel et al, 2017).…”