Lateglacial Shifts in Seasonality Reconcile Conflicting North Atlantic Temperature Signals

Abstract

The Younger Dryas (YD: 12.9-11.7 ka) is a canonical example of abrupt climate change and has evolved in interpretation from a cold snap of possibly global extent to a primarily Northern Hemisphere event centered on the North Atlantic and linked to meltwater-forced disturbance of Atlantic meridional overturning circulation (AMOC) (Broecker et al., 2010;McManus et al., 2004). Northern Hemisphere palaeoclimate data confirm the YD was accompanied by atmospheric circulation shifts (Mayewski et al., 1994), permafrost expansion (Isarin, 1997), and disruption of the Asian monsoon (Cheng et al., 2020;Liu et al., 2008), while ice cores document the rapidity of these shifts (<10 years; Alley, 2000;Steffensen et al., 2008). Nonetheless, a satisfactory trigger for the YD is elusive, partly because our understanding of the event's manifestation continues to evolve (Cheng et al., 2020). For instance, emerging data suggest an out-of-phase relationship between glacier records and traditional interpretations of Lateglacial climate proxies in Europe and the circum North Atlantic (Foreman et al., 2022;Wittmeier et al., 2020). Noting the apparent disparity between the 16°C cooling inferred from Greenland δ 18 O and the muted advances of local glaciers, Denton et al. (2005) hypothesized that YD cooling was greater in winter than summer, reflecting the impact of expanded winter sea ice on ocean-atmosphere heat transfer. Recent glacial studies have explored this model further, suggesting that North Atlantic YD summers did not cool or may even have been anomalously warm (

Hydroclimate intensification aided Early Holocene Arctic glacier survival

“…From a paleoclimate perspective, the presented evidence for land vegetation (terrestrial plant fossils) and high productivity (LOI) helps explain why thermophilous species were already present at the onset of the Holocene in nearby Ringhorndalen 70 . Beyond our study area, the above (growing season) data complement a growing body of evidence that suggests that the Younger Dryas stadial was characterized by mild summers and severe winters 71,72 , rather than year-round cooling.…”