Disko Bugt Research Articles

The Stone Age of Qeqertarsuup Tunua (Disko Bugt). A regional analysis of the Saqqaq and Dorset cultures of Central West Greenland

The present text is a revised version of the Ph.D. thesis ‘Tent Rings and Stone Tools’ defended by the author on March 11th 2005 at the University of Copenhagen. Saqqaq and Dorset sites excavated by the author in the southern part of Qeqertarsuup Tunua (Disko Bugt) form the empirical basis for a comparison of Saqqaq and Dorset settlement in the area. Earlier reconstructions of the cultural history were based mainly on observations of stratified middens. In contrast to this, the present work focuses on the ‘horizontal dimension’ within the archaeological record. As a consequence, settlement patterns, dwelling types and the spatial organisation of dwellings are the principal objectives. Saqqaq and Dorset settlement patterns are broadly similar and it is concluded that there is little evidence to suggest any major difference in economy or adaptation between the two periods. Both Saqqaq and Dorset settlement patterns are characterised by a number of large settlements located strategically near the most productive biotopes. Minor settlements, most often occupied during the warm season, are found within the catchment area, indicating annual recurring dispersal of the population during the warmer months. Only Sydostbugten, in Southeastern Qeqertarsuup Tunua, appears to exhibit significant differences between Saqqaq and Dorset settlement patterns. Large Dorset settlements have not been found in Sydostbugten and it is suggested that this area, probably due to climatic oscillations, was less attractive for settlement during the Dorset period than it was in the Saqqaq. Consequently, the Dorset people seem only to have utilised Sydostbugten for specialised seasonal camps. Saqqaq and Dorset accommodation comprises distinct summer and winter dwellings. During both periods, the summer dwellings are characterised by what are believed to be single family tents. These occur in two principal varieties: Tent rings, with a central hearth, and mid-passage tent rings, where the interior is divided in two by parallel lines of stones. This difference in architecture is suggested to result from variation in the social composition of the inhabitants. Winter dwellings of both the Saqqaq and Dorset cultures are characterised by more solidly built structures. In the Saqqaq culture there are ‘platform dwellings’ and mid-passage structures filled with fire-cracked rocks. During the Dorset, the winter dwellings are characterised by ‘double-platform dwellings’, in which a central floor area divides the interior into two platforms that are often paved. The presence of more than one hearth or lamp stand, as well as ‘mirrored’ distributions of the most frequent tool categories to the left and right of the central floor area, is interpreted as a result of these dwellings being occupied by two families. Chapter 7 focuses on Saqqaq raw material distribution from killiaq sources in the vicinity of Qaarsut and Angissat. The raw material distribution from these two sources is characterised as a regional and local system. The procurement and subsequent distribution of raw materials from Angissat in Southern Qeqertarsuup Tunua appears thus to have been imbedded in the local resource exploitation. Much of the raw material extraction appears to have been carried out by hunting parties visiting the outcrop during summer hunting trips. In contrast to this, Qaarsut at Nuussuaq shows evidence of a more comprehensive production of preforms, which were distributed through-out Western Greenland. Economically as well as socially, there appear to be numerous similarities between the Saqqaq and Dorset cultures. However, when evaluating the radiocarbon dates, there appears to be discontinuity between the two periods as is also suggested by earlier excavations of stratified deposits. In Sisimiut District, to the south of Qeqertarsuup Tunua, the latest Saqqaq dates overlap with the oldest Dorset dates. Theoretically, there could be continuity between the two periods outside Qeqertarsuup Tunua, however the archaeological evidence for such a development has yet to be found. When the cultural history of Qeqertarsuup Tunua is compared with that of Peary Land, the dwelling types and chronological units appear very similar. In the case of Dorset and Independence II, the similarities also extend to include the lithic inventory. As a consequence it is difficult to maintain a division between Dorset in Western and Southern Greenland and Independence II in the High Arctic.

Using a Paired Chironomid δ18O and Aquatic Leaf Wax δ2H Approach to Reconstruct Seasonality on Western Greenland During the Holocene

AbstractThe Arctic hydrological cycle is predicted to intensify as the Arctic warms, due to increased poleward moisture transport during summer and increased evaporation from seas once ice‐covered during winter. Records of past Arctic precipitation seasonality are important because they provide a context for these ongoing changes. In some Arctic lakes, stable isotopes of oxygen and hydrogen (δ18O and δ2H, respectively) vary seasonally, due to seasonal changes in precipitation δ18O and δ2H. We reconstruct precipitation seasonality from Lake N3, a well‐dated lake sediment archive in Disko Bugt, western Greenland, by generating Holocene records of two proxies that are produced at different times of the year, and therefore record different lake water seasonal isotopic compositions. Aquatic plants synthesize waxes throughout the summer, and their δ2H reflects winter‐biased precipitation δ2H at Lake N3, whereas chironomids synthesize their head capsules between late summer and winter, and their δ18O reflects summer‐biased precipitation δ18O at Lake N3. During the middle Holocene at Lake N3, aquatic plant leaf wax was strongly 2H‐depleted, while chironomid chitin was 18O‐enriched. We guide interpretations of these records using sensitivity tests of a lake water and energy balance model, where we change precipitation amount and isotope seasonality inputs. The sensitivity tests suggest that the contrasting trends between proxies were likely caused by an increase in precipitation amount during all seasons and an increase in precipitation isotope seasonality, in addition to proxy‐specific mechanisms, highlighting the importance of understanding lake‐ and proxy‐specific systematics when interpreting records from sediment archives.

The oldest part of the Rae craton identified in western Greenland

New U-Pb zircon data from a range of Archean rocks from the Paleoproterozoic Rinkian Belt in the North-West and central West Greenland provide new constraints on the crystallisation and formation of the Archean basement to this Paleoproterozoic orogen. The results show that the protoliths of the oldest orthogneisses were emplaced in the central part of the Rinkian Belt at c. 3150–3100 Ma. This was followed in the southern part of the belt by the crystallisation of igneous rocks at c. 3000–2900 Ma, including rhyolites that are well preserved. This event is not recorded in the northern part of the belt and may represent southward growth away from a cratonic core at this time. The orthogneisses across the entire belt were subsequently affected by a metamorphic event at c. 2730–2660 Ma, which included intrusions of granites and northward cratonic growth. A few samples also yield evidence of a younger Paleoproterozoic overprint associated with the formation of the 1.90–1.80 Ga Rinkian Belt. The Archean basement rocks of the Rinkian Belt have previously been correlated with similar rocks exposed in northeast Canada and, consequently, they have been referred to as the Greenland part of the Rae craton. The new data support this correlation in general but reveal that Greenland contains the oldest rocks of the Rae craton discovered so far. The new data also show that the Rinkian Belt has a significantly different Archean history than the basement underlying the Nagssugtoqidian orogen to the south. This supports former models that envision two separate Archean cratons colliding during the Paleoproterozoic and that a suture of this age is situated in the central Disko Bugt area.

Distribution of dinocyst assemblages in surface sediment samples from the West Greenland margin

Abstract Palynological analyses of 60 surface sediment samples from West Greenland margin revealed high concentrations of dinoflagellate cysts (dinocysts), particularly in the Disko Bugt area, where they reach >104 cysts g−1. Dinocyst assemblages are characterized by a relatively high species diversity and are dominated by Operculodinium centrocarpum, cysts of Pentapharsodinium dalei, Islandinium minutum, Islandinium? cezare, and Brigantedinium spp. On a regional scale, the overall assemblages show statistical relationships with sea-ice cover duration, primary productivity, salinity and summer-fall temperature. The cysts of Pentapharsodinium dalei, Operculodinium centrocarpum, and Spiniferites elongatus appear linked to high productivity and to characterize the late summer-fall bloom. Although Islandinium minutum and Islandinium? cezare are generally associated with a seasonally sea-ice covered environment, there is no linear relationship between their relative abundance and sea-ice concentration or duration on a regional scale, along the West Greenland margin. The abundance of these taxa primarily reflects cold and low-salinity water in the study area. Radionuclide measurements (210Pb and 137Cs) allow the distinction between two categories of samples, the “modern” ones likely encompassing the interval younger than 1950 CE, and the others that may be considered “sub-modern”. Statistical analyses indicate that dinocyst assemblages belonging to “modern” and “sub-modern” categories are not significantly different. Hence, the dinocyst assemblages of surface sediment samples, both “modern” and “sub-modern”, represent fluxes homogenized over a relatively long time interval, which illustrates a spatial distribution corresponding to the main gradient in oceanographic conditions. Consequently, dinocyst assemblages in surface sediments can be assumed to represent the average “modern” conditions with a sufficiently high degree of confidence for their use in environmental studies and paleoclimate reconstructions.

European trading, whaling and climate history of West Greenland documented by historical records, drones and marine sediments

The European trading and whaling activities of the 17th– 19th centuries provide records of climate and sea- ice conditions off West Greenland in the form of ships’ logs and other official documents in many archives around Europe. These documents, combined with evidence from marine sediments, help describe climate changes in general, and seaice volume changes in particular, in connection with human activity in the region. The Greenland National Museum & Archives in Nuuk (NKA) hosts a unique collection of original documents presenting detailed insight into weather and ice conditions as well as the daily life of the colonial centres and outposts recorded by the documents of the Danish administration. These documents also reveal many aspects of the interaction between the Inuit and Europeans from 1779 onwards. Information retrieved from the archives in Nuuk has been combined with results from palaeo-environmental investigations of marine sediment cores to unravel climate variability and changes in sea ice. This information has been supplemented with data from an extensive field programme using drones to document onshore remains from the whaling period in the Disko Bugt region (Fig. 1).

A 2000-year record of ocean influence on Jakobshavn Isbræ calving activity, based on marine sediment cores

The Greenland Ice Sheet has experienced significant mass loss in recent years. A substantial component of this is attributable to the retreat of marine-terminating outlet glaciers, which lose mass through increases in calving, submarine melting and terrestrial meltwater discharge. In terms of iceberg production, Jakobshavn Isbræ is the largest marine-terminating glacier in Greenland, yet relatively little is known about its history before the first glacier margin observations in 1851. Two marine sediment cores obtained 15 and 19 km northwest from the mouth of Jakobshavn Isfjord were analysed to reconstruct the past behaviour of Jakobshavn Isbræ and to investigate the response of the glacier system to ocean forcing. These records provide long-term (~2000) context for assessing the significance of the rapid changes in glacier stability over the last century. The X-ray imagery and high-resolution grain size analysis from both cores reveal distinct multi-centennial-scale changes in the flux of iceberg-rafted debris (IRD) from Jakobshavn Isbræ. Foraminiferal analysis shows that variability in the relatively warm West Greenland Current (WGC) may have been an important driver of calving activity at Jakobshavn Isbræ. We find that iceberg rafting and WGC inflow were relatively high from onset of the record, at 60 BC, until AD 1100. Subsequently, the inflow of the WGC into Disko Bugt decreased. This was accompanied by a dramatic reduction in IRD from AD 1500 to 1850, which is attributed to the establishment of a floating ice tongue. We also show that ocean warming in the 20th century is part of a longer-term warming trend in the WGC which started at around AD 1700. Finally, these new records underline the complexity of glaciomarine sediments; IRD variability was driven by the inflow of the WGC but was also modulated by a complex interplay of air temperature, sea-ice coverage and ice margin proximity.

New insights into sea ice changes over the past 2.2 kyr in Disko Bugt, West Greenland

Past sea ice conditions and open water phytoplankton production were reconstructed from a sediment core taken in Disko Bugt, West Greenland, using the sea ice biomarker IP25 and other specific phytoplankton biomarker (i.e., brassicasterol, dinosterol, HBI III) records. Our biomarker record indicates that Disko Bugt experienced a gradual expansion of seasonal sea ice during the last 2.2 kyr. Maximum sea ice extent was reached during the Little Ice Age around 0.2 kyr BP. Superimposed on this longer term trend, we find short-term oscillations in open water primary production and terrigenous input, which may be related to the Atlantic Multidecadal Oscillation and solar activity changes as potential climatic trigger mechanisms. A direct sample-to-sample multiproxy comparison of our new biomarker record with microfossil (i.e., benthic foraminifera, dinocysts, and diatoms) and other geochemical records (i.e., alkenone biomarkers) indicates that different proxies are influenced by the complex environmental system with pronounced seasonal changes and strong oceanographic gradients, e.g., freshwater inflow from the Greenland Ice Sheet. Differences in sea ice reconstructions may indicate that the IP25 record reflects only the relatively short sea ice season (spring), whereas other microfossil reconstructions may reflect a longer (spring–autumn) interval.

Late Holocene Sea Surface Instabilities in the Disko Bugt Area, West Greenland, in Phase With δ18O Oscillations at Camp Century

AbstractPalynological analyses of sediment core MSM343310 from Disko Bugt (68°38′861°N, 53°49′493°W) document decadal‐ to centennial‐scale variability of sea surface conditions during the last ~3,600 years. Dinocyst fluxes (>104 cysts/cm2 yr−1) indicate a very high productivity. Dinocyst assemblages dominated by Islandinium minutum, Brigantedinium spp., Islandinium? cezare, and the cyst of Pentapharsodinium dalei suggest low surface salinity and marked shifts in summer sea surface temperature. The application of the modern analog technique to dinocyst assemblages, using an updated reference data set with new sites from the West Greenland margin, led to reconstruct decadal‐centennial‐scale variations in sea surface salinity and temperature, in phase with the δ18O variations in the Camp Century ice core. At ~1.5 ka BP, the seasonal sea ice cover records an important regime change, from winter‐only sea ice to more unstable conditions marked by successive cooling pulses with sea ice cover of up to 8 months/yr. The data suggest a close relationship between hydrographic conditions and regional climate over Greenland. Our record shows variations with a mean 200 years periodicity until ~2 ka BP, which supports the hypothesis of climate variations driven by solar variability. After 1.5 ka BP, our data show a variability characterized by a 60–70 year periodicity, which suggests linkages with the Atlantic Multidecadal Oscillation and southwestward migration of the atmospheric polar front. The most recent part of the record, from ~1900 CE to 2007 CE, is characterized by assemblages reflecting warmer surface conditions and reduced sea ice cover.

Earliest Holocene deglaciation of the central Uummannaq Fjord system, West Greenland

Uummannaq Fjord, West Greenland, held the Uummannaq Ice Stream system that drained an estimated ~6% of the Greenland Ice Sheet (GrIS) during the Last Glacial Maximum. Published ages for the final deglaciation in Uummannaq Fjord vary from as early as c. 9.8 ka to as late as c. 5.3 ka. Assessing this variability requires additional chronological controls to improve the deglaciation history of central West Greenland. Here, we combine 14C dating of lake sediment cores with cosmogenic 10Be exposure dating at sites adjacent to the present GrIS margin in the central‐inland sector of the Uummannaq Fjord system. We find that ice retreated to or within the present GrIS margin at 10.8±0.2 ka (n = 6). Although this ‘final deglaciation’ to or within the present GrIS margin across the Uummannaq Fjord system varies from c. 10.8 to 5.3 ka, all chronologies indicate collapse from the continental shelf to the inner fjords at c. 11.0 ka, which occurred at a net retreat rate of 300–1100 m a−1. The Uummannaq Fjord system deglaciated c. 1000 years earlier than the major fjord system to the south, Disko Bugt. However, similarly rapid retreat rates of the two palaeo‐ice stream systems suggest that their collapse may have been aided by high calving rates. The asynchronous deglaciation of the GrIS throughout the Uummannaq Fjord system probably relates to the influence of varying fjord geometry on marine glacier behaviour.

Summer Sea-Surface Temperatures and Climatic Events in Vaigat Strait, West Greenland, during the Last 5000 Years

We present a new reconstruction of summer sea-surface temperature (SST) variations over the past 5000 years based on a diatom record from gravity core DA06-139G, from Vaigat Strait in Disko Bugt, West Greenland. Summer SST varied from 1.4 to 5 °C, and the record exhibits an overall decreasing temperature trend. Relatively high summer SST occurred prior to 3000 cal. a BP, representing the end of the Holocene Thermal Maximum. After the beginning of the “Neoglaciation” at approximately 3000 cal. a BP, Vaigat Strait experienced several hydrographical changes that were closely related to the general climatic and oceanographic evolution of the North Atlantic region. Distinct increases in summer SST in Vaigat Strait occurred from 2000 to 1600 cal. a BP and from 1200 to 630 cal. a BP, and are consistent with the “Roman Warm Period” and the “Mediaeval Warm Period” in the North Atlantic region. The summer SST decreased significantly during 1500~1200 cal. a BP and 630~50 cal. a BP, corresponding, respectively, to the Northeast Atlantic cooling episodes known as the “European Dark Ages” and “Little Ice Age”. Spectral and cross-correlation analyses indicate that centennial-scale oscillations in summer SST are superimposed on the long-term trend. The dominant periodicities are centered at 529, 410, and 191 years, which are close to the ubiquitous 512 and 206-year 14C cycle, suggesting that solar forcing may play an important role in summer SST variability in Disko Bugt.

Local glaciation in West Greenland linked to North Atlantic Ocean circulation during the Holocene

Abstract Recent observations indicate that ice-ocean interaction drives much of the recent increase in mass loss from the Greenland Ice Sheet; however, the role of ocean forcing in driving past glacier change is poorly understood. To extend the observational record and our understanding of the ocean-cryosphere link, we used a multi-proxy approach that combines new data from proglacial lake sediments, 14C-dated in situ moss that recently emerged from beneath cold-based ice caps, and 10Be ages to reconstruct centennial-scale records of mountain glacier activity for the past ∼10 k.y. in West Greenland. Proglacial lake sediment records and 14C dating of moss indicate the onset of Neoglaciation in West Greenland at ca. 5 ka with substantial snowline lowering and glacier expansion at ca. 3.7 ka followed by additional ice expansion phases at ca. 2.9, ca. 1.7, and ca. 1.4 ka and during the Little Ice Age. We find that widespread glacier growth at ca. 3.7 ka in West Greenland coincides with marked cooling and reduced strength of the West Greenland Current in Disko Bugt. The transition to cooler ocean conditions at ca. 3.7 ka identified in Disko Bugt is registered by marine proxy data farther afield in East Greenland and on the northwestern Icelandic shelf, implying large-scale paleoceanographic changes across the North Atlantic during this interval. The similarity between glacier change on West Greenland and multiple marine and terrestrial records across the North Atlantic suggests that glaciers are strongly influenced by changes in ocean circulation and consequently implies that the ocean-cryosphere teleconnection is a persistent feature of the Arctic system.

Surface and sub-surface multi-proxy reconstruction of middle to late Holocene palaeoceanographic changes in Disko Bugt, West Greenland

We present new surface water proxy records of meltwater production (alkenone derived), relative sea surface temperature (diatom, alkenones) and sea ice (diatoms) changes from the Disko Bugt area off central West Greenland. We combine these new surface water reconstructions with published proxy records (benthic foraminifera - bottom water proxy; dinocyst assemblages – surface water proxy), along with atmospheric temperature from Greenland ice core and Greenland lake records. This multi-proxy approach allows us to reconstruct centennial scale middle to late Holocene palaeoenvironmental evolution of Disko Bugt and the Western Greenland coastal region with more detail than previously available.Combining surface and bottom water proxies identifies the coupling between ocean circulation (West Greenland Current conditions), the atmosphere and the Greenland Ice Sheet. Centennial to millennial scale changes in the wider North Atlantic region were accompanied by variations in the West Greenland Current (WGC). During periods of relatively warm WGC, increased surface air temperature over western Greenland led to ice sheet retreat and significant meltwater flux. In contrast, during periods of cold WGC, atmospheric cooling resulted in glacier advances.We also identify potential linkages between the palaeoceanography of the Disko Bugt region and key changes in the history of human occupation. Cooler oceanographic conditions at 3.5 ka BP support the view that the Saqqaq culture left Disko Bugt due to deteriorating climatic conditions. The cause of the disappearance of the Dorset culture is unclear, but the new data presented here indicate that it may be linked to a significant increase in meltwater flux, which caused cold and unstable coastal conditions at ca. 2 ka BP. The subsequent settlement of the Norse occurred at the same time as climatic amelioration during the Medieval Climate Anomaly and their disappearance may be related to harsher conditions at the beginning of the Little Ice Age.

Sedimentary evidence for a mid-Holocene iceberg-generated tsunami in a coastal lake, west Greenland

We report sedimentological evidence for a tsunami from a coastal lake at Innaarsuit, Disko Bugt (west Greenland), which was most likely generated by a rolling iceberg. The tsunami invaded the lake c. 6000 years ago, during a period of time when relative sea level (RSL) was falling quickly because of isostatic rebound. We use the background rate of RSL fall, together with an age model for the sediment sequence, to infer a minimum wave run-up during the event of c. 3.3 m. The stratigraphic signature of the event bears similarities to that described from studies of the early-Holocene Storegga slide tsunami in Norwegian coastal basins. Conditions conducive to iceberg tsunami include a supply of icebergs, deep water close to the shore, a depositional setting protected from storms or landslide tsunami, and a coastal configuration that has the potential to amplify the height of tsunami waves as water depths shallow and the waves approach and impact the coast. Future warming of polar regions will lead to increased calving and iceberg production, at a time when human use of polar coasts will also grow. We predict, therefore, that iceberg-generated tsunami will become a growing hazard in polar coastal waters, especially in areas adjacent to large, fast-flowing, marine-terminating ice streams that are close to human populations or infrastructure.

The influence of ice marginal setting on early Holocene retreat rates in central West Greenland

Ice sheet reconstructions from diverse ice margin settings, spanning multiple millennia, are needed to assess the reaction of the Greenland Ice Sheet (GrIS) to millennial-scale climatic forcing and to place historical records in a longer-term context. Here we present 18 new cosmogenic 10 Be exposure ages and five new radiocarbon ages that constrain the early Holocene retreat of the GrIS in the Disko Bugt region in both a marine and a land-based setting. Results indicate similar rates of early Holocene retreat of � 40-50m a � 1 from transects in Torsukattak fjord (marine setting) and the Naternaq area (land-based setting). We compile seven previously published chronologies of deglaciation from West Greenland, which yield early Holocene retreat rates ranging from 10 to 65m a � 1 , similar to those determined for our two study areas. This work demonstrates that when averaged on millennial timescales, retreat rates were remarkably similar along the western GrIS margin. Furthermore, the retreat rates calculated here demonstrate that terrestrial sectors of ice sheets can retreat at net rates comparable to their marine counterparts. Copyright # 2015 John Wiley & Sons, Ltd.

Fluid flow and methane occurrences in the Disko Bugt area offshore West Greenland: indications for gas hydrates?

The present study is the first to directly address the issue of gas hydrates offshore West Greenland, where numerous occurrences of shallow hydrocarbons have been documented in the vicinity of Disko Bugt (Bay). Furthermore, decomposing gas hydrate has been implied to explain seabed features in this climate-sensitive area. The study is based on archive data and new (2011, 2012) shallow seismic and sediment core data. Archive seismic records crossing an elongated depression (20×35 km large, 575 m deep) on the inner shelf west of Disko Bugt (Bay) show a bottom simulating reflector (BSR) within faulted Mesozoic strata, consistent with the occurrence of gas hydrates. Moreover, the more recently acquired shallow seismic data reveal gas/fluid-related features in the overlying sediments, and geochemical data point to methane migration from a deeper-lying petroleum system. By contrast, hydrocarbon signatures within faulted Mesozoic strata below the strait known as the Vaigat can be inferred on archive seismics, but no BSR was visible. New seismic data provide evidence of various gas/fluid-releasing features in the overlying sediments. Flares were detected by the echo-sounder in July 2012, and cores contained ikaite and showed gas-releasing cracks and bubbles, all pointing to ongoing methane seepage in the strait. Observed seabed mounds also sustain gas seepages. For areas where crystalline bedrock is covered only by Pleistocene–Holocene deposits, methane was found only in the Egedesminde Dyb (Trough). There was a strong increase in methane concentration with depth, but no free gas. This is likely due to the formation of gas hydrate and the limited thickness of the sediment infill. Seabed depressions off Ilulissat Isfjord (Icefjord) previously inferred to express ongoing gas release from decomposing gas hydrate show no evidence of gas seepage, and are more likely a result of neo-tectonism.

Unstable ice stream in Greenland during the Younger Dryas cold event

Past, present, and future ice sheet stability is closely linked to the dynamic behavior of major draining ice streams and surrounding ice shelves. While short observational records document the recent variability and acceleration of ice streams, the long-term dynamics of ice streams remain poorly documented. Here, we date the Pjetursson’s Moraine on Disko Island, Greenland, to 12.2 ± 0.6 ka and demonstrate that the Jakobshavn Isbrae (JI) ice stream collapsed during the middle of the Younger Dryas (YD) cold interval. We suggest that this collapse was due to the incursion of warm subsurface water under the ice shelf fronting the JI ice stream, as well as increased surface-air temperature and sea-surface temperature seasonality starting at the beginning of the YD cold interval. The triggered acceleration of the land-based JI and the delivery of icebergs into Disko Bugt potentially contributed to Heinrich Event 0 at the end of the YD. The collapse of the JI ice stream 12.2 ± 0.6 ka ago demonstrates that calving marine-based ice margins can respond rapidly to environmental changes. It provides a new benchmark for marine-terminating ice stream models.

Paleoceanographic changes in the Disko Bugt area, West Greenland, during the Holocene

Micropaleontological analyses of a sediment core raised in Disko Bugt (West of Greenland) were undertaken in order to document paleoceanographical changes in the eastern Baffin Bay during the Holocene. The modern analogue technique (MAT) applied to dinocyst assemblages provided information on paleo-sea-surface conditions, whereas isotopic analyses of benthic foraminifers aimed at documenting the ‘deep’ water mass occupying the site. During the earlier interval recorded (~10 to ~7.3 cal. kyr BP), important discharge of ice and meltwater from the Greenland Ice Sheet (GIS) margin, notably through the Jakobshavn Isbrae, resulted in harsh conditions with a dense sea-ice cover and low temperatures, productivity, and foraminiferal abundances. Postglacial conditions settled at ~7.3 cal. kyr BP, with a sharp rise in dinocyst abundance and species diversity, which led to reconstruct increase in summer temperatures. We link this transition to the advection of West Greenland Current waters in the upper part of the water column after the reduction of meltwater inputs from GIS. Optimal temperature conditions reaching up to >10°C were finally achieved in surface waters at ~6 cal. kyr BP. Slight cooling pulses were then recorded at ~4.2–4 and ~1.5–1 cal. kyr BP, and the final optimum recorded in surface temperature from ~1 to 0.8 cal. kyr BP is associated with the ‘Medieval Warm Period’. Throughout the postglacial interval, the data suggest an opposition between sea-surface temperatures and salinity, with warmer intervals being characterized by lower salinity waters, probably as a result of the higher freshwater discharge along the ice margin and notably the Jakobshavn Isbrae.

Impact of Medieval Fjord Hydrography and Climate on the Western and Eastern Settlements in Norse Greenland

Abstract A comparison of the Medieval fjord hydrography and climate regime of the main Norse settlements in Greenland demonstrates important differences in the timing of sea-ice expansion and storminess when comparing the Western and Eastern Settlement regions. The Western Settlement, as well as the northern hunting grounds around Disko Bugt, had already experienced major climate deterioration in the first decades after AD 1200. This regime shift in West Greenland included an expansion of fjord and sea ice (“West Ice”) in coastal waters as well as a drastic atmospheric cooling and an increase in storminess, mainly in the summer season. In contrast, environmental conditions in the Eastern Settlement deteriorated notably later, i.e., around AD 1400. At that time, ice conditions became much more severe, whereas the previously prevailing strong wind activity decreased, which was coeval with a general decrease in aeolian activity in West Greenland, eastern Canada, and NW Iceland. Summer blockage of the fjord e...

A diatom-based sea-ice reconstruction for the Vaigat Strait (Disko Bugt, West Greenland) over the last 5000 yr

A diatom-based sea-ice concentration (SIC) transfer function was developed by using 72 surface samples from west of Greenland and around Iceland, and validated against associated modern SIC. Canonical correspondence analysis on surface sediment diatoms and monthly average of SIC indicated that April SIC is the most important environmental factor controlling the distribution of diatoms in the area, justifying the development of a diatom-based SIC transfer function. The agreement between reconstructed SIC based on diatoms from West Greenland and the satellite and modelled sea-ice data during the last ~75yr suggests that the diatom-based SIC reconstruction is reliable for studying the palaeoceanography off West Greenland.Relatively warm conditions with a strong influence of the Irminger Current (IC) were indicated for the early part of the record (~5000–3860cal. yr BP), corresponding in time to the latest part of the Holocene Thermal Maximum. Between 3860 and 1510cal. yr BP, April SIC oscillated around the mean value (55%) and during the time interval 1510–1120cal. yr BP and after 650cal. yr BP was above the mean, indicating more extensive sea-ice cover in Disko Bugt.Agreement between reconstructed April SIC and changes in the diatom species suggests that the sea-ice condition in Disko Bugt was strongly influenced by variations in the relative strength of two components of the West Greenland Current, i.e. the cold East Greenland Current and the relatively warm IC. Further analysis of the reconstructed SIC record suggests that solar radiation may be an important forcing mechanism behind the historic sea-ice changes.

Alfred de Quervain's Swiss Greenland expeditions, 1909 and 1912

ABSTRACTIn 1909, with two companions Swiss meteorologist Alfred de Quervain travelled to the Uummannaq area of west Greenland, to the same area investigated by Erich von Drygalski in 1892–1893. A major objective was to investigate the changes in the nearby outlet glaciers since Drygalski's visit. Man-hauling sledges, de Quervain and his companions also made a sortie into the interior of the ice cap, penetrating to a distance of about 100 km and to a height of about 1700 m. Having thus whetted his appetite, in1912 de Qervain mounted a further expedition aimed at making a crossing of the ice cap, only the second after that of Fridtjof Nansen in 1888, and along a trajectory significantly further north. De Quervain hoped to determine the shape and height of the ice cap along this trajectory. With three companions and using dog-sledges de Quervain set off from the Disko Bugt area of west Greenland and crossed the ice cap to the area of Ammassalik (now Tasiilaq) on the east coast. In 31 days on the ice the party travelled some 640 km, reaching a maximum altitude of 2510 m. A comprehensive range of scientific observations was effected en route. A support party of three men remained at the western edge of the ice cap for the summer to conduct meteorological and glaciological studies. Thereafter two of this group spent the winter of 1912–1913 at the Danish Arctic Station at Godhavn as guests of Morten Porsild to conduct aerological studies using pilot balloons and, to a lesser degree, captive balloons. All quotations in this paper are translated from the German by the author. This article is the first English-language account of de Quervain's expeditions.