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A new approach to calculating Holocene winter precipitation by combining glacier equilibrium-line altitudes and pine-tree limits: a case stud from Hardangerjokulen, central southern NorwayDepartment of Geology, University of Bergen, Allégaten 41, N-5007 Bergen, Norway
Department of Geography, University of Bergen, Breiviken 2, N-5035 Bergen-Sandviken, Norway
At Hardangerjøkulen, central southern Norway, detailed knowledge of the number, age and magnitude of Holocene glacier fluctuations is used to reconstruct variations in equilibrium-line altitude (ELA) for the last 10 000 years. Present and past ELAs are based on an accumulation-area ratio (AAR) of 0.7 and are adjusted for land uplift. A synchronous relationship between advanced glacier positions and the highest pine-tree limits (Pinus sylvestris L.) is demonstrated for the early to mid-Holocene in southern Scandinavia, which indicates that warm summers were compensated for by high winter precipitation. Based on pine-tree limit fluctuations as a measure of mean ablation-season temperature, Holocene variations in winter precipitation at Hardangerjøkulen have been calculated by substitution in the close exponential relationship between mean ablation-season temperature and winter precipitation at the ELA of Norwegian glaciers. Setting the winter precipitation during the period AD 1961-1990 at 100%, mean values varied from about 65 to c. 175%. The wettest phase, at c. 8500-8300 cal. BP, experienced a mean summer temperature of c. 1.35°C warmer than at present, and may be regarded as a climatic analogue for the increase in precipitation which may accompany greenhouse warming of the atmosphere during the next century. These early-Holocene 'greenhouse centuries' ended abruptly within 30-50 years, and changed into a climatic regime dominated by dry winters and by summers only a little warmer than at present. The transition is synchronous with the most notable
Key Words: Glacier fluctuations • equilibrium-line altitude • ELA • pine-tree limits • tree-lines • summer temperature • winter precipitation • Holocene • Hardangerjøkulen • Norway • Scandinavia.
The Holocene, Vol. 6, No. 4,
381-398 (1996) This article has been cited by other articles:
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18O minimum recorded in Greenland ice cores at 8210 ± 30 years ago (before AD 1990), and is tentatively suggested as a Holocene analogue for the climatic instability (which may have been) recorded in the GRIP ice core during the last interglacial period (the Eemian). 
