Atle Nesje

This study presents a cross-disciplinary revision of the Little Ice Age (LIA) advance of Nigardsbreen glacier, an outlet from Jostedalsbreen ice cap in western Norway. The associated glacier foreland is characterised by a well-preserved moraine series succeeding the 1748 CE LIA culmination, and a robust age control of individual moraines exists from abundant historical written and pictorial information as well as extensive lichenometric studies. The retreat dynamics of Nigardsbreen ever since the LIA maximum extent was attained is considered well-known. The timing of initiation of the LIA advance and dynamics of the glacier growth prior to reaching its maximum extent, however, is less understood as any moraines predating 1748 CE have been subsequently overridden. Potential archives available for exploring the glacier advance are therefore mostly confined to historical data such as for example, tax records, paintings, and church books, which has resulted in a present-day consensus of the LIA onset of Nigardsbreen c. 1710 CE. However, we show that a lack of adequate critical analysis on the accuracy of published historical data has allowed erroneous ages of glacier terminus positions to manifest in literature, resulting in for example, overestimated glacial advance rates. Here, we combine a novel data set of local tax load directly reflecting glacial impact on farming productivity with a cross-disciplinary assessment of published historical data, including rejection of several data points of former glacier extents. As a result, we present a revised glacier length curve for the LIA advance of Nigardsbreen towards its maximum extent.

This study presents the sedimentary succession of an outwash plain and an alluvial fan located along the valley Langedalen at the south‐eastern side of the Jostedalsbreen ice cap in inner Sogn, western Norway. A newly exposed ~2.8‐m‐high section along the southern riverbank of Langedøla river shows alternating layers of minerogenic sediments and peat layers with tree logs, identified as Salix sp. The section is situated in the distal part of an alluvial fan built out from the southern slope of Langedalen. Six AMS radiocarbon dates of tree fragments indicate that the accumulation of the fine‐grained sediments in the lower part of the section was initiated earlier than the basal radiocarbon date of 914–976 calibrated years CE (1 σ age range). These basal, fine‐grained sediments are interpreted as proglacial outwash deposited in a floodplain depression or abandoned river channel in a low‐energy glaciofluvial environment. Periods of low glacier cover, low river discharge or low‐water stands over the floodplain allowed peat formation and the growth of trees and shrubs in the valley. The radiocarbon dates further indicate relatively rapid sediment accretion (~2.7–3 cm a −1 ) between 190 and 125 cm below the sediment surface, equivalent to approximately 1220 to 1250 cal. a CE (1 σ age range). At ~60 cm depth below the surface, dated to approximately 1590 to 1620 cal. a CE (1 σ age range), a transition to more coarse‐grained, sandy and gravelly sediments indicates increased sediment supply and distal expansion of the alluvial fan. This occurred most likely as a consequence of increased sediment yield from expanding glaciers along the southern valley side of Langedalen as a response to the initial Little Ice Age glacier growth. Based on these results, the accretion and progradation of glacier‐fed alluvial fans mainly occur during periods of glacier advance rather than during glacier recession.