Cold spells over Greenland during the mid-Pliocene Warm Period

The fate of the Greenland Ice Sheet (GIS) under global warming stress is still unascertained. From this viewpoint, GIS conditions during the mid-Pliocene Warm Period (mPWP; 3.264-3.025 Ma), an interval often referred to as a close analogue of a near-future warmer globe, deserve special attention. Neodymium (Nd) and lead (Pb) isotope signatures of marine sediment cored off the southern Greenland margin record intense glacial erosion pulses on southern Greenland Precambrian terranes during this interval, accompanied by a strong reduction of deep contour currents, and following a near obliquity cycle (~ 41 ka) pacing. Despite the high atmospheric CO2 concentration (~ 400 ppmV) of the mPWP, cold spells were thus strong enough to allow for active ice growth over Greenland. The mPWP interval was marked by a reduced amplitude in the axial tilt oscillation of the Earth, thus low overall summer insolation conditions at high latitudes, a feature not anticipated in the near future. Therefore, if offering analogies with the near future of the Earth's climate, the mPWP interval cannot be seen as a genuine analogue specifically for predicting the fate of the GIS.