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

Abstract

The history of Holocene glacier variations of Flatebreen, an independent glacier close to the SW part of the Jostedalsbreen ice cap, has been reconstructed from lacustrine sediments in the proglacial lake Jarbuvatnet. The sedimentary succession shows evidence of three maini episodes of Holocene glacier 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 continued up to the present. At 43 cm in the core, the medium silt content increases significantly, accompanied by a minor increase in the sand content. This textural change is interpreted as the first time that the tenninus of Flatebreen extended inlto an] upstream lake at 1083 m a.s.l. The age model suggests that this event took place around 800 cal. yr BP (-AD 1150), as a response to the initial ‘Little Ice Age’ glacier expansion after the ‘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 nomial in the Jostedalsbreen region are inferred for 9700-9400, 9200-8300, 8200-6500, 5700-5100, 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 periods of lower than normal winter precipitation correlate with periods of enhanced ice-rafting in the North Atlantic.