The Onset and Rate of Holocene Neoglacial Cooling in the Arctic

The middle to late Holocene (8,200 years ago to present) in the Arctic is characterized by cooling temperatures and the regrowth and advance of glaciers. Whether this Neoglaciation was a threshold response to linear cooling, or was driven by a regional or Arctic-wide acceleration of cooling, is unknown. Here we examine the largest-yet-compiled multiproxy database of Arctic Holocene temperature change, along with model simulations, to investigate regional and Arctic-wide increases in cooling rate, the synchronicity of Neoglacial onset, and the observed and simulated rates of temperature change. We find little support for an Arctic-wide onset of Neoglacial cooling but do find intervals when regions experienced rapid increases in long-term cooling rate, both in the observations and in climate model simulations. In the model experiments, Neoglacial cooling is associated with indirectly forced millennial-scale variability in meridional heat transport superposed on the long-term decline of summer insolation.