Central West Greenland Research Articles

Jakobshavn Glacier, west Greenland: 30 years of spaceborne observations

Early 1960's reconnaissance satellite images are compared to more recent image and map data in an interannual and seasonal study of West Central Greenland margin fluctuations. From 1962 to 1992, ice sheet margins to the north and south of Jakobshavn Glacier retreated despite a decline in average summer temperatures. The retreat may be reversing along the southern flank of the ice stream where regional mass balance estimates are positive. From 1950 to 1996, the terminus of Jakobshavn Glacier seasonally fluctuated ∼2.5 km around its annual mean position. The total calving flux during the summer is more than six times that during winter. We identified that summer melting and the break‐up of sea ice and icebergs in the fjord are important in controlling the rate of iceberg production. If correct, calving rates may be expected to increase should climate become warmer in the near future.

Diet of the ringed seal (<i>Phoca hispida</i>) in Greenland

Analysis of 454 stomachs of ringed seals (Phoca hispida) collected from the Inuit hunt in six municipalities in West Greenland and 30 alimentary tracts collected by scientists in East Greenland, showed seasonal and regional differences in the diet. In Northwest and East Greenland polar cod (Boreogadus saida) and Arctic cod (Arctogadus glacialis) were the most dominant prey items. In contrast, seals in central West Greenland mainly preyed upon amphipods (Parathemisto spp.), capelin (Mallotus villosus), redfish (Sebastes sp.) and squid (Gonatus sp.), while capelin was the most important prey item in Southwest Greenland. The material from Uummannaq demonstrates seasonal variations, as euphausiids were common in spring, and snailfish (Liparis spp.) dominated from October through January, where after snailfish disappeared with the formation of fast ice. No age related differences in the diet were found in stomach samples from Avanersuaq, but in Upemavik crustaceans were more abundant in stomach samples from younger immature seals. Greenland halibut (Reinhardtius hippoglossoides) was only present in samples from seals older than 4 years. In Upemavik Arctic cod was the dominant prey item for seals caught in May at the iceedge, whereas polar cod dominated the samples from seals caught in open water.

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

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.

Contrasting Pb isotopes of Archaean and Palaeoproterozoic sulphide mineralisation, Disko Bugt, central West Greenland

Sulphide separates from mineralisation in Archaean and Palaeoproterozoic host rocks of the Disko Bugt area, central West Greenland, have been analysed for trace elements and Pb isotopes. Isotopic compositions of lead from sulphide separates of Archaean supracrustal rocks show wide variations. Archaean semi-massive sulphides and sulphides separated from felsic metavolcanites yield an errorchron age of 2821 +77/−82, with a model μ1 value of 7.36; this is comparable to the estimated age of the supracrustal rocks. The two most prominent mineralised sites, the Andersen and Eqip prospects, have their own unique Pb isotope pattern; the Andersen prospect is considered to represent the result of an upper crust of Palaeoproterozoic process. The sulphide separates of Palaeoproterozoic epigenetic mineralisation hosted in shear and fault zones in the supracrustal rocks has a common origin, e.g. linked to a metamorphic peak and/or hydrothermal alteration. Gold-bearing samples indicate a local origin for associated sulphides; no regional processes seem to be involved in the formation of the gold occurrences.

Status of the harbour porpoise in Greenland

In Greenlandic waters the harbour porpoise (Phocoena phocoena) has been observed around the southern part of Greenland from Ammassalik on the east coast to Avanersuaq in northwest Greenland. The main distribution lies between Sisimiut and Paamiut in central west Greenland. Catch statistics from 1900 to 1993 indicate an annual average take of 668 harbour porpoises, ranging from 27 to 1531 animals. A decline in the reported catch has been recorded since 1980. Harbour porpoises are mainly caught between April and November, with a peak during June to October. Five fish species, crustaceans and squids have been found in stomach contents of harbour porpoises in Greenlandic waters. There are no indications that environmental issues such as organochlorines, heavy metals, oil or noise have constituted any threat to harbour porpoises in Greenland. No reports of ice entrapments of harbour porpoises have yet been made in Greenland, as is the case for white whales and narwhals on the west coast of Greenland. Disease patterns of harbour porpoise have not been studied in Greenland and incidents of mass mortality have never been recorded. Killer whales are sparse along the west Greenland coast and are not believed to constitute a threat to the harbour porpoise population. In Greenland no estimates on stock size are available, and a monitoring programme is needed if the impact of the catch is to be evaluated.

Routes and Travel Rates of Migrating Peregrine Falcons Falco peregrinus and Swainson's Hawks Buteo swainsoni in the Western Hemisphere

We describe and compare the migration routes, length of migration, and duration of migration of Peregrine Falcons Falco peregrinus tundrius and Swainson's Hawks Buteo swainsoni in the Western Hemisphere. We radio tracked migrants using the Argos satellite system. Our initial samples were 34 Swainson's Hawks from representative areas of their breeding range, and 61 Peregrine Falcons captured at nest sites across the North American boreal forest and low Arctic or on the migration routes along the mid-Atlantic and Gulf of Mexico coasts. The average distance of migration for Peregrines was 8,624 km southward, and 8,247 km northward. Peregrines travelled at an average rate of 172 km/d southward and 198 km/d going north. Peregrine Falcons used at least three broad, general routes south from the breeding areas, and individuals stopped migrating as far north as the U.S.A. mid-Atlantic coast and as far south as central Argentina. The radiomarked Peregrine Falcons used coastal routes, mid-continental routes, and water-crossing routes: the Davis Strait and Caribbean Sea. During northward migration, Peregrines migrating through at Padre Island, Texas diverged for destinations from central Alaska across the continent to central West Greenland. Swainson's Hawks migrated an average of about 13,504 km southward and 11,952 km northward, and travelled 188 km/d southward and 150 km/d northward. Swainson's Hawks converged in eastern Mexico on the Gulf of Mexico coast. Southward, these hawks followed a narrow, well-defined path through Central America, across the Andes Mountains in Columbia, and east of the Andes to central Argentina where they all spent the austral summer. Swainson's Hawks northward migration largely retraced their southward route.

Ancient Eskimo dwelling sites and Holocene relative sea-level changes in southern Disko Bugt, central West Greenland

A coordinated geological-archaeological investigation has been carried out in southern Disko Bugt with the primary purpose of elucidating Holocene relative sea-level (RSL) changes. Two RSL curves representing the Early-Middle Holocene emergence of respectively southeastern and southwestern Disko Bugt have been constructed. Elevations of paleo-Eskimo sites of different ages have been surveyed and supplemented with similar elevations compiled from the literature. Detailed investigations have been carried out at two partly submerged Dorset I sites. At both sites, the stratigraphy of the foreshore has been recorded in terrain profiles. It is concluded that the RSL history of southern Disko Bugt was one of steady emergence during Early-Middle Holocene followed by submergence in Late Holocene. The stratigraphy of the foreshore at the two Dorset I sites indicates that RSL has been at least 2-2.5 m below sea-level, and that the Transgression to present sea-level started after ca 1 ka B.P.

Breeding distribution and abundance of the great cormorant Phalacrocorax carbo carbo in Greenland

The Greenland population of the great cormorant Phalacrocorax carbo carbo numbers 2000–3000 pairs which breed in about 110 colonies distributed along a 1000 km long coastline in central and northern West Greenland. The number of colonies has increased and the breeding range has expanded in recent decades. These trends are believed to be related to a reduced hunting pressure. The number of nests per colony is smaller than in European colonies. The population is of particular conservation concern to Greenland because of its small size and presumed discrete status.

Studies of the lichen flora of coastal areas in Central West Greenland

Studies of the lichen flora of coastal areas in Central West Greenland

An ‘open system pingo’ near Kangerlussuaq (Søndre Strømfjord),West Greenland

Some of the most conspicuous structures generated in permafrost regions are pingos, conical hills containing an ice lens. Collapse structures of Pleistocene pingos are known from many sites in Europe (e.g. Washburn, 1973; Pissart, 1988), and active pingos have been described from the Antarctic, Siberia, Canada, Alaska, Spitzbergen and Greenland; in central West Greenland examples are found on Disko island and the Nuussuaq peninsula (Müller, 1959; Weidick, 1971, 1974; Scholz, 1984). No pingos have hitherto been reported from southern West Greenland, although the surficial geology of the region has been investigated in some detail (e.g. Weidick, 1968, 1974; Hansen, 1970; Hårløv et al., 1980; Scholz & Grottenthaler, 1988; Dijkmans & Törnqvist, 1991). This article describes a large and presumably active pingo discovered in August 1996 by the first author, east of the airport at Kangerlussuaq (Søndre Strømfjord) (Fig. 1).

A comparison of geoid undulations for west central Greenland

The accuracy of a new local gravity field model, GEOID94A, is examined at a site on the western Greenland ice sheet. The model, developed by the Danish National Survey and Cadastre, incorporates several new gravity data sets including an extensive amount of airborne gravity data. Model‐derived geoid undulations were compared to independently determined undulations found by differencing the elevations from Global Positioning System controlled airborne laser altimetry and optical leveling surveys. Differences between the two sets of undulations were less than +/−6 cm RMS. The comparison improved (+/−5 cm RMS) when GEOID94A undulations were adjusted by local gravity observations also acquired at the site. Our comparisons demonstrate that GEOID94A adequately models the long to intermediate wavelengths of the gravity field. We conclude that GEOID94A constitutes a reliable reference model for studies of Greenland's gravity field.

Ancient Eskimo dwelling sites and Holocene relative sea-level changes in southern Disko Bugt, central West Greenland

Ancient Eskimo dwelling sites and Holocene relative sea-level changes in southern Disko Bugt, central West Greenland

Breeding distribution and abundance of the great cormorant Phalacrocorax carbo carbo in Greenland

The Greenland population of the great cormorant Phalacrocorax carbo carbo numbers 2000–3000 pairs which breed in about 110 colonies distributed along a 1000 km long coastline in central and northern West Greenland. The number of colonies has increased and the breeding range has expanded in recent decades. These trends are believed to be related to a reduced hunting pressure. The number of nests per colony is smaller than in European colonies. The population is of particular conservation concern to Greenland because of its small size and presumed discrete status.

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 developing only in a “marsh environment”. It is argued that the marsh setting is not relevant to the formation of these features and that they are simply hydraulic pingos. A group of marsh initiated open system pingo remnants from the Iterdlagssûp kûgssua valley mouth, in Mellemfjord, Disko Island, Central West Greenland was described in Christiansen (1995). Gurney and Worsley (1997) state that the location of this group of pingo remnants in the Iterdlagssûp kûgssua valley mouth is of no relevance to their genesis, and that they presumably were the result of an assumed late Holocene sea level regression, causing permafrost to be established in the valley bottom. In this reply the arguments by Gurney and Worsley (1997) on the Iterdlagssûp kûgssua valley pingos are commented, and it is argued by way of sea level information, frost penetration and water supply that the special setting must indeed have caused pingo initiation and growth. Furthermore, the area has experienced a relative sea level rise during the late Holocene.

Pterygoneurum lamellatum, a Moss New to Greenland (Musci, Pottiaceae)

Pterygoneurum lamellatum (Lindb.) Jur. is reported new to the Greenland bryoflora based on two finds from west central Greenland. The specimens were found 350 km apart, both on frost boils of clay on raised marine sediments of Holocene age. These findings support the thesis that openland has existed in West Greenland during one or more glaciations. While preparing for the 1996 field season in Greenland we came across a specimen from the vicinity of Sendrestr0mfjord, central West Greenland initially named Stegonia latifolia Vent. Closer examination revealed this specimen to belong to Pterygoneurum lamellatum that had no previous record from Greenland. This specimen was collected in 1977 between the mountain Keglen and 7 km to the northwest, in the area located north of Sendrestr0mfjord Airport, at the Polar Circle, inland, and about 25 km from the Inland Ice Cap in an continental climatic regime. The specimen consists of a few plants with well developed sporophytes. The habitat is open clay on a frost boil located on raised marine sediments of Holocene age. On July 11, 1996, two of us found a second population, also consisting of few mature sporophytes and some sterile gametophytes. This population occurred 350 km to the north just outside the airport of Jakobshavn/Illulisat at 70014'N, 51001'W (Fig. 1). Geographically, Pterygoneurum lamellatum has its main distribution outside the Arctic, being a predominantly steppe and warm semi-desert species. Its discovery in the Nearctic is of fairly recent date. Steere (1959) reported this species from arctic Alaska, as P. arcticum Steere, which he subsequently synonymized with P. lamellatum (Steere 1976, 1978). Kuc (1973) reported three sites of P. lamellatum (also as P. arcticum) from the Queen Elisabeth Islands, and Brassard (1976) reported it from Alert, Ellesmere Island. Miller and Ireland (1978) reported Pterygoneurum ovatum (Hedw.) Dix. from Bathurst Island. Our plants from Greenland matches well with the description of P. arcticum given by Steere (1959), although we have not seen the type specimen. We have seen the specimen (FH) collected by Miller on Bathurst Island but we are hesitant to refer these plants to either P. lamellatum or P. ovatum due to variations in spore sizes. While spores of P. lamellatum vary between 14-22 ptm, and spores of P. ovatum are 20-27 ptm (Fig. 2), spores of the Bathurst Island plants fall within 20-31 Im. Actual varia ion in spore size range as shown by a large number of measurements may, however, be larger than wh n measurements are expressed as simple ranges. We feel certain about the taxonomic placement of our own two specimens from Greenland as P. lamellatum, but we find that a detailed taxonom-

High ammonium contents in the 3800 Ma Isua supracrustal rocks, central West Greenland

Ammonium contents of whole-rock and biotite samples from the metasedimentary sequence of the 3800 Ma Isua supracrustal belt, central Greenland, have been determined and compared with the ammonium contents of volcanic, sedimentary, metamorphic, and granitic rocks from the Late Archaean-Early Proterozoic. A sample of the Amitsoq gneiss has an NH 4 + content (whole-rock: 9 ppm, biotite: 29 ppm) that is similar to many younger igneous rocks. Ammonium contents of the supracrustal rocks vary with chemistry and mineralogy of the rock and most likely were inherited from the original sediments. A series of carbonate-bearing and basic plagioclase-bearing biotite-rich schists from sequence A have varying NH 4 + contents (whole-rock: 6–24 ppm) that increase with an increasing chemical /clastic component and decreasing volcanogenic component. Biotites in these rocks, together with biotites in mica schists of the same sequence, have high NH 4 + contents which vary over a small range of 54–95 ppm, suggesting that the NH 4 + in these rocks was contained mostly in authigenic clays of the original sediments. All these data imply that clay minerals were the major sink of NH 4 + or other nitrogen compounds on the Earth's surface at 3800 Ma. Two samples of graphite-bearing garnet-staurolite-mica schist from sequence B have remarkably high NH 4 + contents (whole-rock: 68 and 86 ppm, biotite: 234 and 253 ppm), which are as high as, or even higher than, those of common Late Archaean-Early Proterozoic argillites. It appears almost certain that the original, thick, clay-rich bottom sediments contained a large amount of NH 4 + or other nitrogen compounds. The most likely major source of nitrogen in these NH 4 +-enriched, graphite-bearing mica schists might be organic nitrogen.

Implications for Deglaciation Chronology from New AMS Age Determinations in Central West Greenland

New evidence has been obtained for the age of the Umı̂vı̂t/Keglen and Ørkendalen moraine systems close to the present ice sheet margin in central West Greenland. The Umı̂vı̂t/Keglen moraine system is dated at 7500 to 650014C yr B.P., which is older than the previously assumed date of 7300 to 600014C yr B.P. The Ørkendalen system is now dated at 6200 to 560014C yr B.P. against earlier estimates of 300 to 70014C yr B.P. The new age is based on AMS radiocarbon-dated organic material within depressions between morainic ridges belonging to the Ørkendalen system. A major implication of the new age is that ice margin positions prevailed for about 6000 years behind the present ice sheet margin. The retreat behind the present margin could be substantial, and in the light of deglaciation rates prior to the Ørkendalen phase, may be ca. 10's of kilometers rather than kilometers. Circumstantial evidence is found for the retreat of the ice sheet margin behind its present position during the Holocene climatic optimum. The results, placed into a time frame of deglaciation since the last glacial maximum, enable comparison with Greenland ice sheet models and ice core records.

Modelled ice-sheet margins of three Greenland ice-sheet models compared with a geological record from ice-marginal deposits in central West Greenland

Ice-sheet modelling is an essential tool for estimating the effect of climate change on the Greenland ice sheet. The large spatial and long-term temporal scales of the ice-sheet model limits the amount of data which can be used to test model results. The geological record is useful because it provides test material on the time-scales typical for the memory of ice sheets (millennia). This paper compares modelled ice-margin positions with a geological scenario of ice-margin positions since the Last Glacial Maximum to the present in West Greenland. Morphological evidence of ice-margin positions is provided by moraines. Moraine systems are dated by 14C-dated marine shells and terrestrial peat. Three Greenland ice-sheet models are compared. There are distinct differences in modelled ice-margin positions between the models and between model results and the geological record. Disagreement between models and the geological record in the near-coastal area is explained by the inadequate treatment of marginal processes in a tide-water environment. A smaller than present ice sheet around the warm period in the Holocene (Holocene climatic optimum) only occurs if such a period appears in the forcing (ice-core record) or used temporal resolution. Smoothing of the GRIP record with a 2000 year average eliminates the climatic signal related to the Holocene climatic optimum. This underlines the importance of short-term and medium-term variations (decades, centuries) in climatic variables in determining ice-margin positions in the past but also in the future.

Meteorological Observations in 1995 at the Arctic Station, Qeqertarsuaq (Godhavn), Central West Greenland/Concentrational Agriculture: Types, Functions, and Derivation/Den Danske Nationalkomité for Geografi

In October 1990 an automatic meteorological station was established at the Arctic Station (69°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 1995. Concentrational agriculture, defined as types of agriculture based on local concentration of plant nutrients, encompasses two main types: shifting cultivation and infield-outfield systems. They may ecologically be characterised by their mode of concentration: either by a vertical or a horisontal transfer (‘pumping’) of nutrients, respectively. The use of the general term ‘concentrational agriculture’ for the two forms is advocated by demonstrating that functional substitution of one by the other is possible, and by showing that the one type theoretically can be derived from the other. Historically, infield-outfield systems are supposed to be developed from some form of shifting cultivation. Kort beretning om virksomheden i 1995 Justering af medlemskredsen. I forbindelse med valg af repræsentanter fandt en justering af repræsentationsområder sled (Århus Universilet har ikke længere fagområdet ‘kulturgeografi’). Videnskabernes Selskab har i samme forbindelse bifaldet, at fire observatører, repræsenterende undervisningstrinene i geografi deltager i møderne.

Filling and plugging of a marine basin by volcanic rocks: the Tunoqqu Member of the Lower Tertiary Vaigat Formation on Nuussuaq, central West Greenland

The volcanic Tunoqqu Member formed at the end of the second of three volcanic cycles in the Paleocene Vaigat Formation. The Tunoqqu Member consists of brown aphyric and feldspar-phyric basalts and forms a marker horizon within the grey picritic rocks of the Vaigat Formation. Most of the basalts are siliceous and were produced by contamination with crustal rocks of magmas ranging in composition from picrite to evolved basalt. Some of the basalts were erupted from local volcanic centres of which four have been identified, whereas other basalts form more regional flows. The four identified eruption centres are located along fault lines and zones of uplift and subsidence, indicating tectonic control. Tectonic control is also inferred to be important in terminating the volcanic cycle and causing the development of high-level magma chambers where the magmas stagnated, fractionated, and became contaminated. The basalts of the Tunoqqu Member form subaerial lava flows in western Nuussuaq. Central Nuussuaq constituted a marine embayment in which the volcanics were deposited as eastward prograding foreset-bedded hyaloclastite breccia fans which indicate water depths of up to 160 m. Eastern Nuussuaq was a gneiss highland with a more than 700 m high NW-SE-elongated gneiss promontory stretching into the sea. During Tunoqqu Member time the volcanic rocks reached the gneiss promontory and blocked the outlet from the south to the sea in the north. This resulted in increased water levels in the enclosed embayment and transformation of the outlet into a torrential river. This river eroded the concomitantly forming Tunoqqu Member volcanics and the gneiss promontory and deposited the material in up to more than 250 m thick foreset-bedded boulder conglomerates in the sea where the north coast of Nuussuaq is now situated.