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Imhof P.,University of Bern | Nesje A.,University of Bergen | Nesje A.,University Bjerknes Center | Nussbaumer S.U.,University of Bern | Nussbaumer S.U.,University of Zurich
Holocene | Year: 2012

Glacier length, though an indirect and delayed signal of climate conditions, can be used to determine the relationship between climate and glacier response. This study discusses glacier length change of eight outlet glaciers of Jostedalsbreen and Folgefonna (southern Norway), from the 'Little Ice Age' (LIA) until the present. A climate index was calculated from meteorological data from Bergen to determine the specific frontal time lags of the individual glaciers. Short and steep outlet glaciers, such as Briksdalsbreen, react rapidly to changes in climatic conditions, whereas long and gently descending glaciers, such as Nigardsbreen, need longer time to adjust to changes in temperature and/or precipitation. The time lag of Briksdalsbreen was about twice as long during the LIA as today. The correlations between North Atlantic Oscillation (NAO) and climate conditions and glacier fluctuations in Norway and the European western Alps were analysed. As the influence of the NAO on glacier fluctuations is most pronounced during winter, only the winter NAO index was considered. Fluctuations of maritime Norwegian glaciers are highly correlated with the NAO, whereas variations of more continental glaciers in the European western Alps are only partly influenced by the NAO and tend to be anti-correlated. However, the (anti-)correlation with the NAO is not constant during the record, and significantly weaker or even inversed during some periods. A comparison of the LIA glacier fluctuations in southern Norway and the European western Alps suggests that the asynchronous LIA maxima in the two regions may partly be attributed to multidecadal trends in the NAO. © SAGE Publications 2011.

Cunningham L.K.,University of St. Andrews | Austin W.E.,University of St. Andrews | Knudsen K.L.,University of Aarhus | Eiriksson J.,University of Iceland | And 18 more authors.
Holocene | Year: 2013

We undertake the first comprehensive effort to integrate North Atlantic marine climate records for the last millennium, highlighting some key components common within this system at a range of temporal and spatial scales. In such an approach, careful consideration needs to be given to the complexities inherent to the marine system. Composites therefore need to be hydrographically constrained and sensitive to both surface water mass variability and three-dimensional ocean dynamics. This study focuses on the northeast (NE) North Atlantic Ocean, particularly sites influenced by the North Atlantic Current. A composite plus regression approach is used to create an inter-regional NE North Atlantic reconstruction of sea surface temperature (SST) for the last 1000 years. We highlight the loss of spatial information associated with large-scale composite reconstructions of the marine environment. Regional reconstructions of SSTs off the Norwegian and Icelandic margins are presented, along with a larger-scale reconstruction spanning the NE North Atlantic. The latter indicates that the 'Medieval Climate Anomaly' warming was most pronounced before ad 1200, with a long-term cooling trend apparent after ad 1250. This trend persisted until the early 20th century, while in recent decades temperatures have been similar to those inferred for the 'Medieval Climate Anomaly'. The reconstructions are consistent with other independent records of sea-surface and surface air temperatures from the region, indicating that they are adequately capturing the climate dynamics of the last millennium. Consequently, this method could potentially be used to develop large-scale reconstructions of SSTs for other hydrographically constrained regions. © The Author(s) 2013.

Nesje A.,University of Bergen | Nesje A.,University Bjerknes Center | Matthews J.A.,University of Swansea
Holocene | Year: 2012

In the ad 1990s maritime glaciers in Scandinavia started to advance as a response to positive net mass balance in the preceding years, invoking annual advance rates in the order of ~50-60 m and a total frontal advance of 285 m (at Briksdalsbreen) in less than a decade. Records from six south Norwegian glaciers with continuous, annual front measurements are used to evaluate the magnitude, duration, climatic causes, and frontal time lags involved in this mass balance perturbation and the following frontal response of glaciers in southern Norway. A climate index based on meteorological data from Bergen unequivocally demonstrates that the main cause for the large glacier advances in Scandinavia in the 1990s was high winter precipitation linked to positive NAO index in the winters of 1988/1989, 1989/1990, 1992/1993, 1994/1995, 1997/1998, and 1999/2000. Less positive (or negative) glacier mass balance years were 1990/1991, 1993/1994, 1995/1997, and 1998/1999. Between 1996/1997 and 2009, Briksdalsbreen retreated 486 m (maximum annual retreat of 145 m in 2005/2006). The main cause of the significant glacier retreat in the early twenty-first century was a combined effect of reduced winter precipitation and higher summer temperatures. The glacier advance and following retreat phase back to the pre-advance position was completed in ~20 years, and is here termed the Briksdalsbre Event. This event has relevance for the identification and interpretation of decadal to centennial Holocene glacial events recorded in lacustrine and terrestrial sequences. © SAGE Publications 2011.

Nesje A.,University of Bergen | Nesje A.,University Bjerknes Center | Pilo L.H.,Oppland fylkeskommune | Finstad E.,Oppland fylkeskommune | And 8 more authors.
Holocene | Year: 2012

The main aim of this study is to describe consequences of climate change in the mountain region of southern Norway with respect to recently exposed finds of archaeological remains associated with reindeer hunting and trapping at and around ice patches in central southern Norway. In the early years of the twenty-first century, warm summers caused negative glacier mass balance and significant glacier retreat and melting of ice patches in central southern Norway. As a result, prehistoric remains lost and/or left by past reindeer hunters appeared at ice patches in mountain areas of southern Norway. In the warm summer and autumn of 2006 the number of artefact recoveries at ice patches increased significantly because of melting of snow and ice patches and more than 100 objects were recovered in the Oppland county alone. In 2009, detailed multidisciplinary investigations were carried out at the Juvfonne ice patch in Jotunheimen at an elevation of c. 1850 metres. A well-preserved Iron Age hunting station was discovered and in total c. 600 artefacts have been documented at the Juvfonne site alone. Most of the objects were recovered and brought to the Museum of Cultural History at the University of Oslo for conservation, exhibition and storing. Thirteen so called 'scaring sticks' recovered from the recently exposed foreland of Juvfonne were radiocarbon dated, yielding ages that group in two separate time intervals, ad 246-534 and ad 804-898 (±1 sigma). By putting the temporal distribution of the radiocarbon-dated artefacts into the context of late-Holocene glacier-size variations in the Jotunheimen and Jostedalsbreen regions, we conclude that the most extensive reindeer hunting and trapping associated with snow/ice patches was related to periods with prevailing warm summers when the reindeer herds gathered on high-altitude, contracted glaciers and ice patches to avoid insect plagues. The 'freshness' of the fragile organic finds strongly indicates that at least some of the artefacts were rapidly covered by snow and ice and that they may have been more-or-less continuously covered by snow and ice since they were first buried. © The Author(s) 2011.

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