Atle Nesje | University of Bergen (original) (raw)

Papers by Atle Nesje

Quaternary Science …, Jan 1, 2005

Lake sediment cores and cosmogenic exposure (CE) dates constrain the pattern of deglaciation and ... more Lake sediment cores and cosmogenic exposure (CE) dates constrain the pattern of deglaciation and evolution of climate across Baffin Island since the last glacial maximum (LGM). CE dating of erratics demonstrates that the northeastern coastal lowlands became ice-free ca.14ka as the Laurentide Ice Sheet (LIS) receded from its LGM margin on the continental shelf. Coastal lakes in southeastern Baffin Island

Norsk Geologisk Tidsskrift, 1992

ABSTRACT

Norsk Geogr Tidsskr Nor J Geo, 1994

ABSTRACT The total late Cenozoic erosion and denudation in the Sognefjord drainage basin, western... more ABSTRACT The total late Cenozoic erosion and denudation in the Sognefjord drainage basin, western Norway, has been calculated to about 5400 km3 by subtracting the present topography from a reconstructed preglacial (paléic) surface. This volume corresponds to a mean erosion and denudation of 440 m in the Sognefjord drainage basin. The total volume of subaerial denudation and fluvial activity amounts to about 400 km3. The remaining volume of about 5000 km3 yields a mean glacial erosion of about 400 m in the Sognefjord drainage basin. Assuming glacial erosion in a period of 1 million years during the past 2.57 million years, the average rate of glacial erosion in the Sognefjord drainage basin was about 40cm 1000 yr-1 (0.4mm yr-1).

Egs Agu Eug Joint Assembly, Apr 1, 2003

High resolution records of mean annual and summer temperatures over the past 2 millennia have bee... more High resolution records of mean annual and summer temperatures over the past 2 millennia have been developed for the Nordic Seas and adjacent land areas with decadal resolution. A new high quality age model for these records has been developed using a novel tree-ring correlation. The data show a very strong land-ocean coherence. Correlation to instrumental time series is also strong. A remarkable correspondance with proxy records of the nortward extent of the ITZC is apparent in the data, based on correlations to a rainfall/runoff proxy from Cariaco Basin off Venezuela. Further comparisons with long time series of North Atlantic indices based on instrumental data and proxy records are underway and will be reported. The strong tropical linkage is also noticeable in the instrumental time series, indicating possible tropical influence on decadal to century climate changes in the high latitude North Atlantic.

A global overview of glacier advances and retreats (grouped by regions and by millennia) for the ... more A global overview of glacier advances and retreats (grouped by regions and by millennia) for the Holocene is compiled from previous studies. The reconstructions of glacier fluctuations are based on 1) mapping and dating moraines defined by 14 C, TCN, OSL, lichenometry and tree rings (discontinuous records/time series), and 2) sediments from proglacial lakes and speleothems (continuous records/ time series). Using 189 continuous and discontinuous time series, the long-term trends and centennial fluctuations of glaciers were compared to trends in the recession of Northern and mountain tree lines, and with orbital, solar and volcanic studies to examine the likely forcing factors that drove the changes recorded. A general trend of increasing glacier size from the earlyemid Holocene, to the late

Norsk Geologisk Tiddsskrift

Norsk Geologisk Tidsskrift

ABSTRACT

Norsk Geologisk Tiddsskrift

Quaternary Science Reviews

Norsk Geologisk Tidsskrift

The two largest climate coolings following the end of the last glaciation are the Younger Dryas a... more The two largest climate coolings following the end of the last glaciation are the Younger Dryas and the 8.2 ka events. Evidence for these cold excursions is widespread around the North Atlantic and in more distant regions. Both events are well expressed in Greenland ice cores; glacier readvances occurred across much of NW Europe during the Younger Dryas and cold surface waters returned to the North Atlantic, with depressed summer temperatures in eastern North America. The 8.2 ka event has a similar pattern, but the magnitude is substantially lower, with a much shorter duration. However, surprisingly little evidence has been presented for either event from the North Atlantic Arctic. Recently acquired lake sediment records from the Eastern Canadian Arctic contain evidence for both excursions. The 8.2 ka event is recorded at two sites as a significant glacier readvance of cirque and outlet glaciers of local ice caps at 8.2±0.1 ka. In some non-glacially-dominated lakes, a reduction in primary productivity is apparent at the same time. These records suggest colder summers without a dramatic reduction in precipitation, producing positive mass balances and glacier readvances. For most local glaciers, this was the last significant readvance before they receded behind their Little Ice Age margins. Only a few lakes contain records that extend through the Younger Dryas chron. The best-dated lake record, Donard Lake, extends back to 15 ka. Lacustrine sedimentation is currently dominated by a meltwater from an outlet glacier that terminates a few hundred meters from the lake. The glacier has been within the drainage basin of the lake for the past 5.5 ka, although the contribution of glacial sediment has been larger since about 2.5 ka. Prior to 5.5 ka, there is no evidence of a glacier in the catchment of Donard Lake, suggesting that throughout the entire Neoglacial period, the local glacier has been more advanced than at any time since 15 ka. During the Younger Dryas chron, lacustrine primary productivity was greatly reduced, whether measured as the flux of organic carbon to the lake floor or as the percentage of organic matter in lake sediment. We interpret this change to reflect a substantial reduction in summer temperatures for more than 1 ka. However, this temperature drop was not accompanied by a significant glacier readvance, suggesting precipitation must have been very low. This differs from the 8.2 ka event when precipitation must have remained relatively high. These records indicate that in the Eastern Canadian Arctic, summers during the Younger Dryas were much colder than present, but precipitation was dramatically lower too, so glaciers did not advance, whereas during the briefer, and less severe summer cooling associated with the 8.2 ka event, precipitation was not dramatically reduced and glaciers readvanced.

Whereas a number of records from the marine realm have demonstrated Holocene changes regarded to ... more Whereas a number of records from the marine realm have demonstrated Holocene changes regarded to be related to overturning circulation in the North Atlantic region, independent information of atmospherical variability from the terrestrial realm have proven more elusive to capture in palaeo-records. This is a major concern, as several studies have suggested that atmospherical forcing may be an important factor

Norsk Geologisk Tidsskrift

Two terrestrial sections have been studied in order to reconstruct the Holocene glacial and collu... more Two terrestrial sections have been studied in order to reconstruct the Holocene glacial and colluvial history in Leirungsdalen, eastern Jotunheimen. The interpretation of individual sedimentary units is based on the grain-size distribution and compared with modern analogue samples collected in the respective streams and at sites close to the present glaciers. Stages of enhanced debris flow or glacial activity are recognized as sand and silt layers, respectively, while periods of low colluvial and glacial activity in the catchment are characterised by continuous peat accumulation. Age/depth curves based on radiocarbon dates from the Svarthammarbu and Steinflybekken sections indicate debris flow activity > 7500, 7300-6800,6600-5500, 5800, 5700, 5300-4900,4700, 4500,4300, 2300, 2100-1500, 1300, 700-600 and 500-400 cal. yr BP. The first Holocene glacial signal is detected ca. 5300 cal. yr BP. The frequency of glacial events seems to have increased during the Late Holocene, especially...

Multi-proxy paleoclimatic time series have been developed from IMAGES Sites and adjacent suppleme... more Multi-proxy paleoclimatic time series have been developed from IMAGES Sites and adjacent supplementary cores in the Eastern Norwegian Sea. The records cover the last 2000 years at decadal resolution, allowing for a detailed reconstruction of the surface hydrography of the main path of the northern limb of the north Atlantic circulation cell. Centennial to millennial scale events are recorded, such as the "Medieval Warm Phase" (MWP) and the "Little Ice Age" (LIA), which constitute the main long term century scale features. Superimposed on these are multidecadal variability of somewhat less amplitude. There is a close correspondance with continental records reflecting summer temperaure and winter precipitation in western Scandinavia over this period.SST changes are found to be in the range of 1-2 degrees. Significant land-sea correlation is observed. A cold phase in the early 20th Century, a series of cold phases in the LIA and two warm phases in the MWP are observ...

Quaternary Science …, Jan 1, 2005

Norsk Geologisk Tidsskrift, 1992

ABSTRACT

Norsk Geogr Tidsskr Nor J Geo, 1994

Egs Agu Eug Joint Assembly, Apr 1, 2003

Norsk Geologisk Tiddsskrift

Norsk Geologisk Tidsskrift

ABSTRACT

Norsk Geologisk Tiddsskrift

Quaternary Science Reviews

Norsk Geologisk Tidsskrift

Gård og utmark i Gudbrandsdalen - Arkeologiske undersøkelser i Fron 2011-2012, 2016

The archaeological investigations in the mid part of Gudbrandsdalen in 2011 and 2012 revealed a n... more The archaeological investigations in the mid part of Gudbrandsdalen in 2011 and 2012 revealed a number of flood/avalanche horizons, of which «Forrskredet» (ca 350–200 BC), «Gammelofsen» (ca 50–1 BC), and «Merovingertidsofsen» (ca AD 600–800) were recognised as the major events at the investigated sites. Local topography and weather conditions (such as extreme weather events) and more long-term climatic trends were most likely the triggering factors for these events. During the time interval for Forrskredet, glaciers in Jotunheimen were in an advanced position, winter precipitation in mountains in western Norway (Jostedalsbreen) was relatively high, and summer temperatures in Scandinavia, as reconstructed from tree rings, were relatively high. Gammelofsen occurred during a period with relatively small glaciers in Jotunheimen as winter precipitation was increasing in western Norway and summer temperatures were rising in Scandinavia. During Merovingertidsofsen, glaciers in Jotunheimen were in an advanced position, winter precipitation was rapidly increasing in western Norway, and summer temperatures were relatively low in Scandinavia. The prehistoric flood and avalanche events in Gudbrandsdalen, such as the subsequent historic flood events, in particular «Storofsen» (1789) and «Storflaumen» (1860), certainly had a severe impact on settlement and farming.

by Ingar Mørkestøl Gundersen, Jan Henning Larsen, Ole Christian Lønaas, Atle Nesje, Rebecca J S Cannell, Kristin Eriksen, Lise Loktu, Tina Villumsen, Arne Jouttijärvi, Annine Moltsen, and Richard Macphail

E6-prosjektet Gudbrandsdalen er det mest omfattende utgravningsprosjektet som er gjennomført i Op... more E6-prosjektet Gudbrandsdalen er det mest omfattende utgravningsprosjektet som er gjennomført i Oppland noensinne, og har sin bakgrunn i etableringen av ny E6 gjennom dalføret. I 2011 og 2012 gjennomførte Kulturhistorisk museum utgravninger på 64 steder i kommunene Sør-Fron, Nord-Fron og Sel, og utgravningene avdekket blant annet en frem til da ukjent flom-, bosetnings-og jordbrukshistorikk. Omfattende undersøkelser ble også gjort i utmarka, der et stort antall kull-og fangstgroper ble gravd ut. Det samlede vitenska-pelige materialet fra prosjektet har endret forståelsen av Gudbrandsdalens arkeologi og gitt ny kunnskap om hvordan samfunnet i dalføret utviklet seg i jernalderen og middelalderen. Denne boken presenterer de viktigste faglige resultatene, setter resultatene inn i en større kulturhistorisk sammenheng og gjør rede for kunnskapsstatusen på viktige fagområder innenfor Gudbrandsdalens arkeologi.

The melting of perennial ice patches globally is uncovering a fragile record of alpine activity, ... more The melting of perennial ice patches globally is uncovering a fragile record of alpine activity, especially hunting and the use of mountain passes. When rescued by systematic fieldwork (glacial archaeology), this evidence opens an unprecedented window on the chronology of high-elevation activity. Recent research in Jotunheimen and surrounding mountain areas of Norway has recovered over 2000 finds—many associated with reindeer hunting (e.g. arrows). We report the radiocarbon dates of 153 objects and use a kernel density estimation (KDE) method to determine the distribution of dated events from ca 4000 BCE to the present. Interpreted in light of shifting environmental, preservation and socioeconomic factors, these new data show counterintuitive trends in the intensity of reindeer hunting and other high-elevation activity. Cold temperatures may sometimes have kept humans from Norway's highest elevations, as expected based on accessibility, exposure and reindeer distributions. In times of increasing demand for mountain resources, however, activity probably continued in the face of adverse or variable climatic conditions. The use of KDE modelling makes it possible to observe this patterning without the spurious effects of noise introduced by the discrete nature of the finds and
the radiocarbon calibration process.