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Surface exposure–age dating was applied to rock surfaces associated with ice‐marginal moraines at elevations of ~1520–1780 m a.s.l. on the slopes of Galdhøpiggen and Glittertinden, the two highest mountains in Scandinavia located in the Jotunheimen mountains of central southern Norway. This is important for understanding the pattern and timing of wastage of the Scandinavian Ice Sheet at the Younger Dryas–Holocene transition. Cosmogenic exposure dating (here 10Be dating) of boulders from the moraine ridges yielded overall mean ages (corrected for glacio‐isostatic uplift, surface erosion and snow shielding) of ~11.6 ka from Galdhøpiggen and ~11.2 ka from Glittertinden. Similar 10Be ages were also obtained from additionally collected proximal and distal erratic boulders and bedrock samples. These enabled age calibration of Schmidt‐hammer R‐values and independent Schmidt‐hammer exposure‐age dating (SHD) of the moraine ridges, which yielded comparable mean SHD ages of ~10.8 and ~10.6 ka from the Galdhøpiggen and Glittertinden sites, respectively. Taking account of the age resolution and other limitations of both dating techniques, the results suggest that the two sets of moraines have approximately the same age but that neither technique can distinguish unambiguously between moraine formation in the late Younger Dryas or Early Holocene. Together with features of moraine‐ridge morphology and estimates of equilibrium‐line altitude depression of ~360–575 m (corrected for land uplift), the results imply moraine formation during short‐lived re‐advances of active glaciers, at least the lower reaches of which were warm‐based. It is concluded that the local glaciers remained active and advanced during deglaciation either very late in the Younger Dryas or very early in the Holocene, possibly in response to the Preboreal Oscillation at ~11.4 ka. The study supports the concept of a thin Younger Dryas ice sheet and places time constraints on the timing of final deglaciation in southern Norway. [ABSTRACT FROM AUTHOR]

Continuous glacier margin and equilibrium‐line altitude fluctuations of a former glacier on central Andøya, northern Norway, are reconstructed during the Lateglacial based on moraines and AMS 14C‐dated sediments from the distal glacier‐fed lake Ner‐Finnkongdalsvatnet. The results indicate that a valley glacier occupied the entire valley during the Last Glacial Maximum (before 21 970±620 cal. a BP). The glacier remained large throughout the early Lateglacial until a significant glacier retreat took place about 14 300±330 cal. a BP. Major advances occurred during the Older Dryas (OD) and during the Younger Dryas (YD), while minor advances are suggested to have taken place during the Intra Allerød Cold Period and the Late Allerød Cooling. Additionally, three smaller glacier retreats/re‐advances within the YD are suggested to have taken place, the latter being the largest. The glacier re‐formations/advances during the Lateglacial are consistent with increases in temperature, and they are thus suggested to be the result of increased winter precipitation. Comparing the results with relevant glacier and sea‐surface temperature records, a south–north migration of storm tracks may have occurred between 12 100–11 810±220 cal. a BP. The high temporal resolution of local glacier activity in Finnkongdalen improves our understanding of the climate forcing of the regional glacier fluctuations of the northwestern sector of the Scandinavian Ice Sheet during the Skarpnes‐ (OD) and Tromsø‐Lyngen (YD) re‐advances. [ABSTRACT FROM AUTHOR]

Understanding past responses of ice sheets to climate change provides an important long‐term context for observations of present day, and projected future, ice‐sheet change. In this work, we reconstruct the deglaciation of the marine‐terminating western margin of the Scandinavian Ice Sheet in the outer Hardangerfjorden area of southwestern Norway, following the Last Glacial Maximum (LGM) until the start of the Holocene. We base our interpretations on a combination of geomorphological mapping using high‐resolution (LiDAR) terrain models, 68 new cosmogenic nuclide 10Be exposure ages and radiocarbon‐dated lake sediment cores, supported by the stratigraphic position of the 12.1 ka Vedde Ash. We show that even the highest mountain summits in the area (~1200–1400 m a.s.l.) were ice‐covered during the LGM, thus settling debates concerning the Scandinavian Ice Sheet thickness in this region. These summits emerged as nunataqs through the ice sheet about 22–18 ka, potentially owing to upstream ice thinning caused by the break‐up and retreat of the Norwegian Channel Ice Stream. Following the break‐up of the Norwegian Channel Ice Stream, the ice margin seemingly stabilized at the outermost coast for 3500–5500 years before the mouth of Hardangerfjorden became ice free at c. 14.5 ka. Subsequently, during the Bølling and Allerød periods, the ice sheet retreated rapidly into the inner parts of Hardangerfjorden before a major ice sheet re‐advance during the Younger Dryas. We identify and reconstruct a sizeable, independent ice cap on the Ulvanosa mountain massif during the Younger Dryas (YD), a massif that earlier was mapped as covered by the Scandinavian Ice Sheet during the YD. We also document ice‐free areas that are more extensive than previously thought between Hardangerfjorden and Matersfjorden during the YD. [ABSTRACT FROM AUTHOR]

Developing a long‐term understanding of the cryosphere is important in the study of past climatic change. Here we used a nested approach combining diverse instrumental (monthly meteorological data from four weather stations, as well as gridded data) and proxy data (based on blue intensity measurements from local tree ring records) to create a reconstruction of past summer temperature for the central Jotunheimen area in southern Norway. This record was then used to reconstruct annual glacier mass balance from 1962, the start of the yearly measurements, back to 1722, immediately prior to the regional Little Ice Age maximum. Our reconstruction of the 'average' Jotunheimen cumulative glacier mass balance is based on three representative glaciers (Storbreen, Hellstugubreen and Gråsubreen) that were synthesized into one composite record which we term 'Gjennomsnittsbreen' ('mean glacier' in Norwegian) to filter out localized controls on the behaviour of individual glaciers. While not ignoring the role of precipitation on glacier mass balance, our reconstruction demonstrates that glaciers in this region exhibit a strong summer temperature control and appear to have been declining more or less continuously since the mid‐18th century. However, it also shows that this long‐term trend of overall retreat in Jotunheimen is punctuated by relatively short‐lived periods of neutral or occasionally positive glacier mass balance, signifying periods of stillstand or small‐scale glacier advance. These periods or 'events' in our reconstruction were compared with an independent record of 12 moraine‐building events developed using lichenometry. A minimum of 10 of the moraine‐building events identifiable in our reconstruction were also identifiable in the lichenometric data which affords confidence in the performance of our interrogative model. A critical implication of this successful glacier mass balance reconstruction based on just summer temperature is that for Jotunheimen – in contrast to Norwegian maritime glaciers further to the west – there is no need (as was proposed in some previous studies) to invoke large, prolonged increases in winter snowfall to explain glacier advances, not even for events such as the Little Ice Age. [ABSTRACT FROM AUTHOR]