A large portion of the Greenland ice sheet that is today over 500 m thick did not exist during the Early to Mid Holocene.

Prudhoe Dome (PD), a 2500 km² section of northwestern Greenland’s ice sheet (GIS), is today 500 to 600 m thick (Walcott-George et al., 2026).

Approximately 6000-8000 years ago, or when atmospheric CO2 was alleged to be ~260 ppm, PD had deglaciated completely, exposing the soil to sunlight.

The primary mechanism for the PD deglaciation was the estimated 3-7°C warmer-than-present regional temperatures. This warming and the consequent ice cap minima was said to be  “Arctic-wide”.

Starting ~4000 years ago the GIS gradually began thickening until it recently reached its modern glaciated state, with glaciation peaking in the 1800s.

Image Source: Walcott-George et al., 2026