Holocene mean July temperature and winter precipitation in western Norvay inferred from palynological and glaciological lake-sediment proxies

Abstract

Reconstructions of mean July temperature (T_jul) and winter precipitation (P_w) for the last 11/500 years on the Folgefonna peninsula are presented. T_jul was reconstructed using pollen-climate transfer functions and P_w was reconstructed based on the exponential relationship between mean solid winter precipitation and ablation-season temperature at the equilibrium-line altitude (ELA) with a reconstructed former ELA, using T_jul as the proxy for ablation-season temperature. The reconstructions from the Folgefonna peninsula suggest that the early Holocene was relatively cool and dry until c. 8000 cal. yr BP, followed by a warm and humid mid-Holocene until c. 4000 cal. yr BP with inferred T_jul above 12°C and P_w reaching as high as 225% of the present day. Subsequent to c. 4000 cal. yr BP a reduction is seen in both inferred T_jul and P_w with large fluctuations during the last 500 years. In addition, new calculations of P_w from two glaciers (Hardangerjøkulen and Jostedalsbreen) in southern Norway are presented. The results show that P_w varied in phase at all glaciers, probably as a response to the same climate forcing factor. During the early Holocene a major shift is suggested between winds from the west and the east.