Holocene glacier fluctuations of Flatebreen and winter-precipitation changes in the Jostedalsbreen region, western Norway, based on glaciolacustrine sediment records

The history of Holocene glacier variations of Flatebreen, an independent gl acier close to the SW part of the Jostedalsbreen ice cap, has been reconstr ucted from lacustrine sediments in the proglacial lake Jarbuvatnet. The sed imentary succession shows evidence of three main episodes of Holocene glaci er expansion. The first is recorded in the basal part of the core up to 370 cm. According to the age/depth relationship in the sediment core (based on 12 AMS radiocarbon dates), this glacier expansion episode terminated about 10200 cal. yr BP. The second major glacier phase lasted from 8400 to 8100 cal. yr BP, while the third was initiated around 4000 cal, yr BP and has co ntinued up to the present. At 43 cm in the core, the medium silt content in creases significantly, accompanied by a minor increase in the sand content. This textural change is interpreted as the first time that the terminus of Flatebreen extended into an upstream lake at 1083 m a.s.l. The age model s uggests that this event took place around 800 cal. yr BP (similar to AD 115 0), as a response to the initial 'Little Ice Age' glacier expansion after t he 'Mediaeval Warm Period'. By using a Holocene-inferred summer-temperature curve from central southern Norway in the exponential relationship between annual winter precipitation (snow) and ablation-season temperature at the ELA, periods of higher winter precipitation than the 1961-90 normal in the Jostedalsbreen region are inferred for 9700-9400, 9200-8300, 8200-6500, 570 0-5100, 4700-4600, 4500-4300, 3800-3000, 2100-1800, 1600-1300 and 1200-1000 cal. yr BP, and from 900 cal, yr BP to the present. The intervening period s of lower than normal winter precipitation correlate with periods of enhan ced ice-rafting in the North Atlantic.