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

Abstract

Abstract. During the last glacial period, proxy records throughout the Northern Hemisphere document a succession of rapid millennial-scale warming events, called Dansgaard–Oeschger (DO) events. A range of different mechanisms has been proposed that can produce similar warming in model experiments; however, the progression and ultimate trigger of the events are still unknown. Because of their fast nature, the progression is challenging to reconstruct from paleoclimate data due to the limited temporal resolution achievable in many archives and cross-dating uncertainties between records. Here, we use new high-resolution multi-proxy records of sea-salt (derived from sea spray and sea ice over the North Atlantic) and terrestrial (derived from the central Asian deserts) aerosol concentrations over the period 10–60 ka from the North Greenland Ice Core Project (NGRIP) and North Greenland Eemian Ice Drilling (NEEM) ice cores in conjunction with local precipitation and temperature proxies from the NGRIP ice core to investigate the progression of environmental changes at the onset of the warming events at annual to multi-annual resolution. Our results show on average a small lead of the changes in both local precipitation and terrestrial dust aerosol concentrations over the change in sea-salt aerosol concentrations and local temperature of approximately one decade. This suggests that, connected to the reinvigoration of the Atlantic meridional overturning circulation and the warming in the North Atlantic, both synoptic and hemispheric atmospheric circulation changes at the onset of the DO warming, affecting both the moisture transport to Greenland and the Asian monsoon systems. Taken at face value, this suggests that a collapse of the sea-ice cover may not have been the initial trigger for the DO warming.

NALPS19: sub-orbital-scale climate variability recorded in northern Alpine speleothems during the last glacial period

“…The exception to this is during the interval of 100 to 115 ka, where transitions in the AICC2012 chronology occurred up to 3000 years later than in NALPS19. In such instances, the transitions in the revised AICC2012 chronology of Extier et al (2018) are in agreement with NALPS19 on centennial scales, supporting the hypothesis that AICC2012 appears to be considerably too young between 100 and 115 ka. Using a ramp-fitting function to objectively identify the onset and the end of abrupt transitions, we show that δ 18 O shifts took place on multi-decadal to multi-centennial timescales in the North Atlantic-sourced regions (northern Alps and Greenland) as well as the Asian monsoon.…”

“…(f) 2σ range of U-Th ages used to produce (e) are colour-coded the same as (e). (g) NGRIP records on the GICC05 modelext chronology (Svensson et al, 2008;Wolff et al, 2010), AICC2012 chronology (Veres et al, 2013), and AICC2012 revised according to Extier et al (2018). To see this graph split into 20 000-year slices and with the INTIMATE event stratigraphy scheme (Rasmussen et al, 2014), see Fig.…”

“…Comparison of NGRIP and NALPS19 shows that the broad-scale pattern of shifts in δ 18 O was remarkably similar during this period, including down to centennial-scale events. Differences do, however, arise when considering the timing and duration of events, which we investigate further by applying the ramp-fitting function of Erhardt et al (2019). The ramp-fitting function is similar to the one used by Mudelsee (2000), but instead uses probabilistic inference to define a transition via a linear ramp between two constant levels.…”

N<sub>2</sub>O changes from the Last Glacial Maximum to the preindustrial – Part 1: Quantitative reconstruction of terrestrial and marine emissions using N<sub>2</sub>O stable isotopes in ice cores

“…This is very likely also the reason why the duration of the terrestrial emission increase in the ice core based reconstruction (grey line in Fig. 5) has a similar timescale, while the rapid warming in Greenland and the North Atlantic occurred only in a few decades (Erhardt et al, 2019;Steffensen et al, 2008).…”

“…4). Reconstructions from the high-accumulation Law Dome drill site offer the best connection with the current atmospheric measurements (Etheridge et al, 1988;Francey et al, 1999). The Law Dome ice core record covers the time interval from 2 ka BP to 1979 CE and air samples obtained from the firn column and the Cape Grim air archive cover 1942 CE to 2004CE (MacFarling Meure et al, 2006 (Fig.…”