The lacustrine sedimentary sequence in Sygneskardvatnet, western Norway: a continuous, high-resolution record of the Jostedalsbreen ice cap during the Holocene

Abstract

Two lacustrine sediment cores from Sygneskardvatnet, Sunndalen, confirm that at least the northern part of the Jostedalsbreen ice cap melted away during the Atlantic Chronozone between 6475 and 5300 14 C yr BP (7340 and 6150 cal. BP), possibly interrupted for short intervals of glacier activity around 6000 and 5800 14 C yr BP (6900 and 6700 cal. BP). Prior to this, periods of glacier expansion culminated at ca. 8500, 8400, 8200, 7750, 7600, and 7400 cal. BP. The 8400/8200 cal. BP advances are correlated with the widespread `8200 event’ (“Finse event”) recorded in Greenland ice cores, lacustrine and proglacial sites, and marine sediments. During the early part of the Holocene, periods of glacier contraction culminated at ca. 8450, 8300, 7900, 7500, and 6250 cal. BP, of which the last represents climatic optimum conditions (lowest supply of minerogenic sediments and/or highest organic production). The sedimentary record also shows that the ice cap has existed continuously since 5300 14 C yr BP (6150 cal. BP). Neoglaciation involved three main phases (1: 6150–4500 cal. BP, 2: 4500–2700 cal. BP, 3: 2700 cal. BP to the present) and a series of low-amplitude glacier advances which occurred at 6000, 5800–5700, 5600, 5500, 5200, 5100, 4900, 4800, 4700–4550, 4450, 4300, 4200, 4150, 4050, 4000, 3900, 3800, 3550, 3300, 2550, 2450, 2350, 2250, 2150, 2000, 1800, 1700, 1600, 1400, 1300, 1150, 1050, and the 1000 cal. BP (including “the Little Ice Age”). Loss-on-ignition analyses indicate, however, that episodes of less glacier activity occurred during the mid- and late Holocene at around 5900-5800, 5550, 5450–5300, 5050, 4850, 4750, 4500, 4400, 4100, 3950, 3700, 3450, 3100, 2650, 2500, 2400, 2300, 2200, 1850, 1700, 1550, 1350, 1250, 1050–1000 cal. BP, and during the twentieth century. Altogether, the lacustrine record from Sygneskardvatnet indicates that the Holocene has been interrupted by 41 periods of increased glacier activity (mean return period of ca. 150 years) and by 36 events of glacier contraction (mean return period of 210 years). Spectral analysis of the LOI data show peaks at periods of about 50, 85, 110, 250–285, 500, and 2000 calendar years. The mean time resolution in core Sygneskardvatnet-2 is ca. 20 yr cm −1, while the mean sedimentation rate is 0.5 mm yr −1.