Hanne H. Christiansen

Procedures used for luminescence dating of sediments

Abstract An account of the procedures for thermoluminescence (TL) and optically stimulated luminescence (OSL) dating of sediments used at the Nordic Laboratory for Luminescence Dating is given. The topics discussed include sampling, sample preparation, separation of quartz and feldspars using heavy liquids, dose rate estimation and methods for estimating the equivalent dose. Special attention is paid to the partial bleach TL technique of Mejdahl (1988), which appears to give reliable results for partially bleached sediments. Optically stimulated luminescence dating using stimulation by infra-red (IR) and green light has been taken up and especially added-dose methods using stimulation by IR or green light have been tried with some success. Some sources of error are discussed, including the adverse effect of shallow traps.

Permafrost and Periglacial Geomorphology at Zackenberg

Publisher Summary This chapter discusses the permafrost and periglacial geomorphology at Zackenberg. Permafrost is a climatically sensitive thermal state, the top of which is particularly vulnerable to climatic changes. Therefore, monitoring of the thermal state and geomorphological activity in the active layer and top permafrost is part of the GeoBasis monitoring program. All permafrost monitoring is carried out in the valley bottom, a short distance from the Zackenberg Research Station. This has enabled the collection of a unique summer-thaw-progression data set in two Circumpolar Active Layer Monitoring (CALM) network sites since 1996. Periglacial landforms exist in the Zackenberg landscape and include ice-wedges, sorted patterns, rock glaciers, active-layer detachment slides, soli-fluction lobes and sheets, nivation hollows and associated fans, and basins together with avalanche fans. Coastal landforms along Young Sund display changes in sea ice cover. The characteristics and activity of all these landforms are important parts of the GeoBasis program, providing improved knowledge about the development of modern high-arctic periglacial landscapes. An important periglacial condition that has been monitored with high frequency in the Zackenberg lowland is the seasonal thaw progression of the active layer at the ZEROCALM-1 and ZEROCALM-2 sites. Zackenberg as an important future Greenlandic permafrost observatory is discussed in the chapter.

Hydrochemical characteristics of bulk meltwater from an entire ablation season, Longyearbreen, Svalbard

The ionic and isotopic characteristics of bulk waters emanating from the cold-based Longyearbreen, central Svalbard, in 2004 are examined to determine lithological, hydrological and glaciological controls on water composition, solute provenance and chemical denudation. The geology consisted of reactive coal seams and associated sedimentary rocks. Acidity caused by microbial-mediated oxidation of sulfides and, to a lesser extent, nitrogen-bearing minerals was neutralized by congruent dissolution of dolomite and incongruent weathering of silicates in open-system subglacial drainage channels. The ablation season was divided into an early melt season, a peak-flow period and a late melt season. The runoff distribution during these periods was 1.7%, 89.7% and 8.6%, respectively, whereas the solute flux distribution was 1.9%, 82.1% and 16.0%, respectively. Comparisons between different annual solute flux estimation methods indicated that extrapolation of peak-flow period data significantly underestimated both the early- and late-melt-season solute fluxes. About 3.8% of the solutes derived from sea-salt spray, 0.7% from acid aerosol deposition and 95.5% from crustal/organic sources. The physical and chemical conditions resulted in diffusion of CO 2 rather than atmospheric drawdown. The cation-equivalent weathering rate and the crustal solute yield were 322 ΣmEq + m -2 a -1 and 22 tkm -2 a -1 , respectively, which are within the regional range of Svalbard. However, the chemical weathering intensity was as high as 940 ΣmEq + m -3 owing to the relatively low specific discharge of 0.34 ma -1 .

Internal Structure of Open System Pingos, Adventdalen, Svalbard: The Use of Resistivity Tomography to Assess Ground-Ice Conditions

The objectives of this project were to establish the geometry and internal structure of open system pingos in Adventdalen, Svalbard using electrical resistivity tomography. A clear distinction can be made between the electrical properties of the pingos investigated, depending upon whether they are located either above (Innerhytte pingo) or below (Hytte and Longyear pingos) the maximum Holocene marine limit. The resistivity profile at Innerhytte pingo was characterised by high values of resistivity (10,000–30,000Ωcm), indicating either ice-rich frozen bedrock or a lens of massive ground ice. The electrical resistivity of Hytte and Longyear pingos, both developed within fine-grained, saline marine clays, is exceptionally low (predominantly <2,000Ωm) for permanently frozen ground. This is inconsistent with the presence of a body of massive ground ice, and suggests that the internal structures of Longyear and Hytte pingos do not follow the classic model of a plano-convex pingo-core of massive injection ice. I...

Glacial History and Periglacial Landforms of the Zackenberg area, Northeast Greenland: Preliminary results

Christiansen, Hanne Hvidtfeldt & Ole Humlum: Glacial History and Periglacial Landforms of the Zackenberg area, Northeast Greenland: Preliminary results. Geografisk Tidsskrift 93:19–29. Copenhagen 1993. The geomorphology of the Zackenberg area has been investigated with the purpose of establishing a geomorphological map of a 260 km2 area around the planned research station. Production of a large digital three-dimensional elevation model, based on the use of a multi-model photogrammetric method, has been the basis for a GIS database and a topographical map (1:50,000) covering the investigation area. Both glacial and periglacial landforms have been mapped and a preliminary Late Weichselian glacial history of the Zackenberg area reconstructed. A monitoring of 11 selected test field sites representing climatically sensitive land elements has been established, enabling the registration of even minor short-term variations in the geomorphic processes.

Late Quaternary Environmental and Cultural Changes in the Wollaston Forland Region, Northeast Greenland

Publisher Summary This chapter reviews proxy data from a variety of natural archives sampled in the Wollaston Forland region, central Northeast Greenland. The data are used to describe long-term environmental and climatic changes, focusing on reconstructing the Holocene conditions, particularly in the Zackenberg area. The Wollaston Forland region is completely covered by the Greenland ice sheet several times during the quaternary. During the last glacial maximum (LGM), the margin of the inland ice might have extended to the shelf break off Northeast Greenland. Deglaciation of the Wollaston Forland commenced at the outer coast in the past 11,000–12,000 years, whereas the Zackenberg area was deglaciated somewhat later, in the past 10,000 years, and it took another 3,000–4,000 years before the inner fjords of the region were deglaciated. Isostatic rebound led to the rapid emergence in the early Holocene, but in the late Holocene, low-lying coastal areas were transgressed by the sea. The chapter discusses archaeological evidence for prehistoric occupation of the region.

The ''High Arctic Maritime Snow Climate'' in Central Svalbard

Abstract In this first systematic classification of the snowpack in central Svalbard a new additional snow climate is presented. Based on field observations in the 2007–2009 period, 109 snow pits were quantitatively analyzed in terms of temperature gradients, grain shapes, grain sizes, and hardness of every snow layer. Emphasis was given to the occurrence of depth hoar, ice layers, the most observed weak layer–bed surface interfaces. These parameters in combination with meteorological observations define the “High Arctic maritime snow climate” as having a very thin and cold snowpack, a basal layer of depth hoar with winds labs and ice layers on top. The snowpack lasts for 8–10 months of the year, at higher grounds for the whole year. Snow climate classifications are an important part of improving the local avalanche characterization. This is timely, especially for the area around Svalbards main settlement Longyearbyen, where avalanches represent a natural hazard. Also, climate models for the area predict changing meteorological conditions, especially more solid precipitation, thus a description of the snow climate as it is today is important. This “High Arctic maritime snow climate” characterization is based on the 16.8 km2 mountainous area around Longyearbyen at 78°N, and does not fit any other High Arctic location. Svalbard has in comparison to other High Arctic locations milder climate due to an overall meteorological maritime influence.

Ground penetrating radar investigations of open system pingos, Adventdalen, Svalbard

Ground penetrating radar (GPR) investigations conducted on two open system pingos, Innerhytte pingo and Riverbed pingo, in Adventdalen, Svalbard, are described. The surveys were undertaken at frequencies of 50 and 100 Mhz, and are used in an interpretation of the internal structure, origins and evolution of these landforms. Surface exposures suggest that both pingos are largely formed in weak Jurassic shales. Little evidence for the presence of large bodies of massive ice was found. Strong subsurface reflections within the core of both pingos are interpreted as representing either the presence of alternating shale and ice units, or variations in the chemistry, ice crystal properties or air content of pingo ice. Steeply dipping reflections are most pronounced on the flanks of the pingos and are orientated sub-parallel to the pingo surface. Variability in the depth of signal penetration is attributed to variability in subsurface properties, particularly ice content, and the attenuation of the signal by fine grained shales. The internal structure of Innerhytte pingo indicates that the point of sub-pingo groundwater injection has migrated southwards. Lack of evidence for ground ice beneath the north-eastern zone of this landform suggests that at least part of the landform is an erosional remnant of bedrock caused by fluvial incision of Janssonhaugen, with pingo development occurring only in the area proximal to the upper apex of the feature. Both Innerhytte and Riverbed are characterized by conspicuous surface icings, with groundwater flow to the surface in late winter, prior to initiation of active-layer thawing, suggesting derivation from a deep groundwater source.

The Circumpolar Active Layer Monitoring (CALM) Workshop and THE CALM II Program

Widespread and systematic changes in the thickness of the active layer (the seasonally thawed layer of ground above permafrost), if accompanied by penetration of thaw into the upper layers of ice-rich permafrost, could have profound effects on the flux of greenhouse gases, on human infrastructure in cold regions, and on landscape processes (Kane et al., 1991; Harris et al., 2001a; Nelson et al., 2001, 2002). It is therefore critical that observational and analytical procedures be conducted over extended periods to assess trends and detect cumulative changes in active-layer dynamics over long periods. Establishment of long-term time series of thaw measurements at fixed locations and across diverse landscapes and regions is required to identify scales of spatial variation, detect temporal trends, and validate models. The Circumpolar Active Layer Monitoring (CALM) network, established in the early 1990s through a collaborative arrangement with the International Tundra Experiment (ITEX), was designed to observe changes in the active layer over extended time periods using standard measurement protocols. At present, CALM is the only coordinated and standardized observation program designed to observe and detect decadal

Observations of Open System Pingos in a Marsh Environment, Mellemfjord, Disko, Central West Greenland

Danish Journal of Geography 95: 42–48, 1995. The purpose of this note is to draw attention to the special topographic setting of some pingos observed in Mellemfjord (Greenlandic: Akugdlit), Disko I...