Persistent link between solar activity and Greenland climate during the Last Glacial Maximum

Abstract:

The role of solar activity changes in climate variations is a matter of continuous debate. Due to the relatively short period of direct observations sun-climate studies benefit from long-term proxy based evidence of past solar variability during different climate regimes. The most reliable recorders of past solar activity are cosmogenic radionuclides such as ¹⁰Be and ¹⁴C whose atmospheric production rates are modulated by the strength of the solar and geo- magnetic fields. Since paleo-archives of ¹⁰Be and ¹⁴C carry additional signals of climatic influences on their respective geochemical cycles a combined analysis of both radionuclides leads to improved solar activity reconstructions. However, reconstructions of past solar activity have so far been largely limited to the Holocene due to the lack of high resolution ¹⁰Be and ¹⁴C data further back in time. Here we present a solar activity reconstruction for the end of the last glacial based on high-resolution ¹⁰Be data from the GRIP ice core supported by ¹⁴C records from tree rings and speleothems, providing evidence for solar forcing of Greenland climate during the last glacial maximum (LGM). We find that centennial solar activity variations during the end of the last glacial have been comparable to the Holocene in both patterns and amplitudes. We see evidence for a persistent solar influence on North Atlantic atmospheric circulation during the LGM. Analysis of modern observations and high-top chemistry-climate model experiments suggests that this solar influence can be explained by favorable conditions for the occurrence of high pressure blocking situations south of Greenland during solar minima. This suggests that a similar solar forcing mechanism as today may have been active under a very different climatic setting.