A Walker switch mechanism driving millennial-scale climate variability

A key goal of paleoclimate science is to identify the source of millennial-scale climate fluctuations. Although long-term changes in the Earth’s position relative to the Sun are the driver of climate change on timescales of ≥ 19 thousand years (ka), it is still incompletely understood what causes rapid sub-orbital changes in climate that were common during glacial periods. Here, we provide a continuous, precisely dated speleothem record from southeastern Alaska that spans the last 13.5 ka. Despite its location in the high latitudes of the Northern Hemisphere, this record shows an equatorial Pacific climate pattern during the end of the last deglaciation and Holocene, and is at odds with North Atlantic climate patterns, calling into question the bipolar seesaw mechanism for the Pacific realm. Because of this, we propose a new mechanism to account for sub-orbitally forced climate changes. The mechanism, termed the Walker switch, is forced by insolation and results in rapid zonal sea-surface temperature changes in the equatorial Pacific. The climatic effects of the Walker switch are propagated across the globe, including the high northern latitudes.