Morten Rasch

Present-Day Climate at Zackenberg

Publisher Summary This chapter outlines the most prominent parameters of climate at Zackenberg and focuses on the short-term spatiotemporal variations of these parameters within the valley Zackenbergdalen and along the east coast of Greenland. The individual climatological parameters demonstrate large spatiotemporal variations. The greatest variations occur in winter when the differentiated influence of the solar energy is low or equal to zero, but this is connected to the fact that in the cold winter period, the cyclonic activity is more intensive and frequent than in the warmer summer period. In addition, the temperature contrast between the arctic air and the advected air from the mid-latitudes is highest during this period. In turn, the effect of the underlying surface is not large because snow and sea ice cover almost the entire arctic area. In the warm summer period, the solar radiation is the most important climatological element, and it causes the greatest heterogeneity of the meteorological elements in all spatial scales: micro-, macro-, and topo-climatic. The albedo of the underlying surface that is significantly differentiated increases the influence of solar radiation in the radiation balance. However, because of the attenuated influence of the atmospheric and oceanic circulations and the large areas of the Arctic Ocean and adjacent seas not covered by sea ice, the climatic spatiotemporal differences are lesser in summer than in winter.

Glacimarine sedimentation in Kangerdluk (Disko Fjord), West Greenland, in response to a surging glacier

Abstract Beginning in 1995, a large outlet glacier of the Sermersauq Ice Cap on Disko Island surged 10.5 km downvalley to within 10 km of the head of the fjord, Kuannersuit Sulluat, reaching its maximum extent in summer 1999 before beginning to retreat. Sediment discharge to the fjord increased from 13×10 3 t day −1 in 1997 to 38×10 3 t day −1 in 1999. CTD results, sediment traps and cores from the 2000 melt season document the impact of the surge on the glacimarine environment of the fjord. Within 4 km of the inflow sedimentation rates increased by 30 times over those before the surge, reaching an estimated maximum value of 29 cm a −1 (up to 4.2 mm day −1 between 24 July and 9 September 2000). Fine-grained deposits from suspension in the water column displayed diurnal laminations in response to the interaction of tidal cycles with the sediment plume; these are not found in the sediments deposited before surging. Thin beds of sandy turbidites from turbidity currents originating from slope failures on the delta front occurred at about 20 day intervals during the melt season. Each of these effects was limited to within several kilometres of the point of inflow, but provide a unique signal significantly different from those generated by normal hydroclimatically induced events.

New observations on the relative sea level and deglacial history of Greenland from Innaarsuit, Disko Bugt

Relative sea level (RSL) data derived from isolation basins at Innaarsuit, a site on the south shores of the large marine embayment of Disko Bugt, West Greenland, record rapid RSL fall from the marine limit (ca. 108 m) at 10,300–9900 cal yr B.P. to reach the present sea level at 3500 cal yr B.P. Since 2000 cal yr B.P., RSL rose ca. 3 m to the present. When compared with data from elsewhere in Disko Bugt, our results suggest that the embayment was deglaciated later and more quickly than previously thought, at or slightly before 10,300 cal yr B.P. The northern part of Disko Bugt experienced less rebound (ca. 10 m at 6000 cal yr B.P.) compared with areas to the south. Submergence during the late Holocene supports a model of crustal down-warping as a result of renewed ice-sheet growth during the neoglacial. There is little evidence for west to east differences in crustal rebound across the southern shores of Disko Bugt.

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.

Contrasting glacimarine sedimentary environments of two arctic fiords on Disko, West Greenland

Abstract Two fiords, Kangerluk and Akulliit, on the island of Disko, central West Greenland have very different sedimentary regimes caused by differences in the characteristics of their drainage basins and in the exposure of their waters to the open sea of Baffin Bay. Their insular location also results in much lower input of water and sediment than in nearby fiords on the mainland of Greenland that are affected by glaciers from the Greenland Ice Cap. Akulliit has a small drainage basin and low input of water and sediment; it is directly exposed to the higher energy wave environment of Baffin Bay. As a consequence, the mean thickness of Holocene glacimarine sediment assessed in acoustic records is less than 6 m in the inner and middle reaches of the fiord (mean Holocene accumulation, 0.4 mm/a) and about 11 m (1 mm/a) near the mouth. Dated core sediment indicates that rates are less than 0.5 mm/a in the outer fiord in the last 2 ka. The larger, more glacier-covered drainage basin of Kangerluk contributes much larger loads of sediment to a fiord environment protected from the open sea. As a result, Holocene glacimarine sediment is more than 80 m thick in the inner fiord (mean Holocene accumulation up to 5 mm/a), decreasing to 10–40 m (about 1 mm/a) in the middle reaches. Accumulation rates in Kangerluk are within the range of arctic fiords, including those of Baffin Island, but those in Akulliit are near the lower limit. The decrease in thickness distally in Kangerluk is typical of arctic fiords, but the opposite trend in Akulliit is probably due to erosion and re-distribution of sediment in the higher energy environment there.

The Study Area at Zackenberg

Publisher Summary The Zackenberg Research Station is situated in central Northeast Greenland and is open during June–August. The climate is high arctic, and the study area is mountainous with deep valleys and fjords. The study area for the terrestrial monitoring and research within the framework of Zackenberg Ecological Research Operations (ZERO) comprises the drainage basin of the river Zackenbergelven. Zackenbergdalen was selected as the main study area because of its great diversity in physical landscape features, plant communities, and other biota. Almost all of Greenlands high-arctic landforms and biodiversity are represented in the valley, including moraines, scree slopes, rock glaciers, gently sloping rock faces, river beds, alluvial fans, a raised delta, beach terraces, permanent and perennial snow beds and glaciers, several types of ponds and lakes, fens, heath and barren lands, together with most known species of plants and animals. Research, monitoring, and logistics at Zackenberg are coordinated by the research program ZERO. Research and monitoring within the Zackenberg research area are managed to secure appropriate coordination among individual research projects and between research and monitoring.

Geomorphology and Sedimentary Record of Three Cuspate Forelands as Indicators of Late Holocene Relative Sea-level Changes, Disko, West Greenland.

Abstract Geografisk Tidsskrift, Danish Journal of Geography 97: 33–46, 1997. The coastal geomorphology of three cuspate forelands at Saqqarliit Ilorliit, western Disko, West Greenland is described, sediment core data from salt marshes and lagoons are presented, an emergence curve is constructed, and data are discussed in relation to late Holocene relative sea-level (RSL) changes. On western Disko, falling RSL in early-middle Holocene was followed by rising RSL in late Holocene. Emergence continued until c. 2.5 ka BP. The coastal geomorphology at Saqqarliit Ilorliit suggest transgression early in the interval 2.5—1.0 ka BP and between 0.7 ka BP and the present. The first transgression resulted in formation of an intertidal platform and coastal cliffs. Washover ridges and lagoons developed during the transgression after 0.7 ka BP. Based on the core data it is suggested that the transgression after 0.7 ka BP might have consisted of three transgression phases separated by periods with stable or slightly regre...

Zackenberg in a circumpolar context

Throughout the Northern Hemisphere, changes in local and regional climate conditions are coupled to the recurring and persistent large-scale patterns of pressure and circulation anomalies spanning vast geographical areas, the so-called teleconnection patterns. Indeed, the atmospheric fluctuations described by the North Atlantic Oscillation (NAO) are closely associated with the last four decades of inter-annual variability in local snow and ice conditions observed in the Arctic. Since the NAO has also been connected with changes in the global climate, the behaviour of species, communities and other ecosystem elements at Zackenberg in relation to the NAO enables us to view these in circumpolar and global contexts. Large-scale systems like the NAO constitute the link between the global change and local climate variability to which ecosystem components respond. Here, we place selected ecosystem elements from the monitoring programme Zackenberg Basic presented in previous chapters in a circumpolar context related to NAO-mediated climatic changes. We begin by linking the local variability in winter weather conditions at Zackenberg to fluctuations in the NAO. We then proceed by linking the observed intra- and inter-annual behaviour of selected ecosystem elements to changes in the NAO. The functional ecosystem characteristics in focus are landscape gas exchange dynamics phenological patterns at different trophic levels, consumer-resource dynamics and community stability. The influence of the NAO is presented and discussed in a broader perspective based on information obtained from other arctic localities. The relation between the NAO and the Zackenberg winter weather, is nonlinear, reflecting differential effects of the NAO as the index moves between high and low phases. The inverse hyperbolic relationship found between the NAO and the amount of winter snow was also evident as non-linear response in organisms and systems to inter-annual changes in the NAO. Responses investigated included growth and reproduction in plants and animals, population dynamics and synchrony, inter-trophic interactions and community stability together with system feedback dynamics. (Less)

A Compilation of Radiocarbon Dates from Disko Bugt, Central West Greenland/Meteorological Observations in 1996 at the Arctic Station, Qeqertarsuaq (Godhavn), Central West Greenland/A Discussion on Pingos in Mellemfjord, Disko, Central West Greenland/Open System Pingos in Mellemfjord, Disko, Central West Greenland: A Reply to Gurney and Worsley

188 new and previously published radiocarbon dates on Holocene material from Disko Bugt, central West Greenland, are presented together with relevant informations (laboratory number, place name, dated material, geografic coordinates, altitude and δ13C-value) about the dates. In October 1990 an automatic weather station was established at the Arctic station (65 °15′N,53 °31′W), Qeqertarsuaq (Godhavn), Central West Greenland. The Station register parameters each 20 min., and the parameters have been described in an earlier paper in this journal by Nielsen et al. (1995). The present paper summarises main points of the climate during 1996. Open system, or more correctly, hydraulic pingos, are genetically poorly understood. A continuing problem concerns their need for a perennial groundwater supply (intra- or sub-permafrost). This has to be maintained despite the existence of continuous permafrost in many areas where they are located. Recent work on Disko Island has suggested a new type of hydraulic pingo deve...

Holocene Relative Sea-Level Changes Indicated by Morphostratigraphic Sequences; Sinigfik, Disko Island, West Greenland.

Morten Rasch & Niels Nielsen: Holocene Relative Sea-level Changes Indicated by Morphostratigraphic Sequences; Sinigfik, Disko Island, West Greenland. Geografisk Tidsskrift, Danish Journal of Geography 94:xx–xx, Copenhagen, Dec. 1994. A morphostratigraphic method is introduced in a study of Holocene relative sea-level changes at Sinigfik on the south coast of Disko Island, West Greenland. The method allows detection of relative sea-level rise interrupting the general Holocene emergence. It is concluded that the Holocene relative sea-level history at Sinigfik was one of steady emergence prior to c. 3 ka B P. A complex morphostratigraphic sequence near the present coastline might result from two emergence/submergence events within the last millenium. The geomorphology of the present coastline indicates extensive coastal recession, probably resulting from a relative sea- level rise at present.