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. Plain Language Summary Arctic summer temperatures have decreased for the past 8,000 years, before rapidly warming over the past century. As temperatures cooled, glaciers that had melted began to regrow throughout the Arctic, a phenomenon and a time interval known as Neoglaciation. This study seeks to understand the nature of this cooling and whether or not this indicates a tipping point in the climate system. Specifically, we use a large database of records from ice cores, lakes, ocean sediment, and more paleoclimate archives to detect patterns of cooling. We investigate these patterns, and climate model simulations, to determine what parts of the Arctic experienced Neoglaciation at the same time, how rapidly it cooled, and what climate models indicate about the causes of cooling. We find that the Arctic did not cool simultaneously, but different regions cooled at different times and that the climate models perform well when simulating both the timing and amount of Arctic cooling. Key Points The onset of Neoglaciation is regional and driven by nonlinear increases in regional cooling Model simulations suggest that cooling onsets are linked to Atlantic Meridional Overturning Circulation Observed and simulated rates of late Holocene cooling in the Arctic are remarkably similar