Dead-Ice Under Different Climate Conditions: Processes, Landforms, Sediments and Melt Rates in Iceland and Svalbard

Modern dead-ice environments in the glacier forefields of Brúarjökull, Iceland and Holmströmbreen, Svalbard were investigated with focus on landform and sediment genesis, as well as quantification of melting. Field monitoring and studies of multi-temporal aerial photographs, satellite imagery, and Digital Elevation Models (DEMs) provided data for the melting quantification. Sedimentological and geomorphological data were achieved through field investigations and image analyses. Different measures for dead-ice melting (backwasting, downwasting, ice-walled lake area, glacier retreat and thinning) are assessed in relation to local air temperature data going back to the beginning of the instrumental period. A geomorphological map in scale 1:16 000 of the forefield of the surge-type glacier Brúarjökull was produced through digital aerial photograph interpretation and high-resolution DEM analyses. The map was used for the interpretation of landforms and sediments, and provided an overview of the surging glacier landsystem at Brúarjökull. A conceptual model for the formation of transitional-state ice-cored landforms ? ice-cored drumlins ? was also constructed, based on the research in the Brúarjökull forefield. After a complete melting, the model proposes that such drumlins will disintegrate into patches of hummocky dead-ice moraine. Three years of fieldwork combined with analyses of multi-temporal DEMs and aerial photographs revealed that multiple generations of ice-cored moraines are currently exposed to melting at Brúarjökull. Quantifying the melting progression suggests that in the current climate, a complete de-icing of ice-cored landforms is not likely to occur. Some dead-ice bodies are recycled into new ice-cored landforms, because the total melt-out time exceeds the duration of the quiescent period in the surge cycles. Long-term surface lowering due to dead-ice melting takes place with a rate of c. 0.10-0.18 m/yr. At the stagnant snout of Holmströmbreen, an extensive dead-ice area with ice-cored moraines, eskers and kames has developed since the Little Ice Age glacial maximum. Backwasting of ice-cored slopes and mass-movement processes continuously expose new dead-ice and prevents the build-up of an insulating debris-cover. Currently dead-ice melting progresses with a long-term surface lowering rate of c. 0.9 m/yr. The most prominent impact of dead-ice melting is the development of an extensive ice-walled, moraine-dammed lake receiving sediment from the adjacent slopes. Based on a literature review and the results presented here, dead-ice melting in different climatic settings is discussed, with focus on melt rates and sediment-landform genesis. Because identical processes operate with similar rates in different climates, dead-ice deposits provide little information on the climate at the time of deposition. The glaciodynamic significance of dead-ice deposits is that of stagnation of debris-covered glaciers

Production and preservation of the smallest drumlins

Few very small drumlins are typically mapped in previously glaciated landscapes, which might be an important signature of subglacial processes or an observational artefact. 143 newly emergent drumlins, recently sculpted by the Mulajokull glacier, have been mapped using high resolution LiDAR and aerial photographs in addition to field surveying. In this paper, these are used as evidence that few small drumlins (e.g. height H ≲ 4 m, width W ≲ 40 m, length L ≲ 100 m) are produced; at least, few survive to pass outside the ice margin in this actively forming drumlin field. Specifically, the lack of a multitude of small features seen in other landforms (e.g. volcanoes) is argued not to be due to i) Digital Elevation Model (DEM) resolution or quality, ii) mapper ability in complex (i.e. anthropogenically cluttered or vegetated) landscapes, or iii) post-glacial degradation at this site. So, whilst detection ability must still be at least acknowledged in drumlin mapping, and ideally corrected for in quantitative analyses, this observation can now be firmly taken as a constraint upon drumlin formation models (i.e. statistical, conceptual, or numerical ice flow). Our preferred explanation for the scarcity of small drumlins, at least at sites similar to Mulajokull (i.e. ice lobes with near-margin drumlin genesis), is that they form stochastically during multiple surge cycles, evolving from wide and gentle pre-existing undulations by increasing rapidly in amplitude before significant streamlining occurs

Digital elevation model and orthophotographs of Greenland based on aerial photographs from 1978–1987

Digital Elevation Models (DEMs) play a prominent role in glaciological studies for the mass balance of glaciers and ice sheets. By providing a time snapshot of glacier geometry, DEMs are crucial for most glacier evolution modelling studies, but are also important for cryospheric modelling in general. We present a historical medium-resolution DEM and orthophotographs that consistently cover the entire surroundings and margins of the Greenland Ice Sheet 1978–1987. About 3,500 aerial photographs of Greenland are combined with field surveyed geodetic ground control to produce a 25 m gridded DEM and a 2 m black-and-white digital orthophotograph. Supporting data consist of a reliability mask and a photo footprint coverage with recording dates. Through one internal and two external validation tests, this DEM shows an accuracy better than 10 m horizontally and 6 m vertically while the precision is better than 4 m. This dataset proved successful for topographical mapping and geodetic mass balance. Other uses include control and calibration of remotely sensed data such as imagery or InSAR velocity maps

A Driftwood-Based Record of Arctic Sea Ice During the Last 500 Years From Northern Svalbard Reveals Sea Ice Dynamics in the Arctic Ocean and Arctic Peripheral Seas

We present a 500-year history of naturally felled driftwood incursion to northern Svalbard, directly reflecting regional sea ice conditions and Arctic Ocean circulation. Provenance and age determinations by dendrochronology and wood anatomy provide insights into Arctic Ocean currents and climatic conditions at a fine spatial resolution, as crossdating with reference chronologies from the circum-Arctic boreal forests enables determination of the watershed the driftwood originated from. Sample crossdating may result in a wide range of matches across the pan-boreal region, which may be biased toward regions covered by the reference chronologies. Our study considers alternate approaches to selecting probable origin sites, by weighting scores via reference chronology span and visualizing results through spatiotemporal density plots, as opposed to more basic ranking systems. As our samples come from naturally felled trees (not logged or both), the relative proportions of different provenances are used to infer past ocean current dominance. Our record indicates centennial-to decadal-scale shifts in source regions for driftwood incursion to Svalbard, aligning with Late Holocene high variability and high frequency shifts in the Transpolar Drift and Beaufort Gyre strengths and associated fluctuating climate conditions. Driftwood occurrence and provenance also track the northward ice formation shift in peripheral Arctic seas in the past century. A distinct decrease in driftwood incursion during the last 30 years matches the observed decline in pan-Arctic sea ice extent in recent decades. Our new approach successfully employs driftwood as a proxy for Arctic Ocean surface circulation and sea ice dynamics

Geomorphology and surficial geology of the Femmilsjøen area, northern Spitsbergen

Climate change is amplified in the Arctic, and establishing baseline data for its current character is important. Here we present a map of the geomorphology of the Femmilsjøen area, Spitsbergen, northern Svalbard. The regional physiography is characterised by a low-relief, high elevation mountain plateau, its high-relief steep slopes, and low-relief coastal lowlands. The results indicate that glaciers were most likely warm-based and erosive in the low terrain, whereas there are signatures of colder, less erosive ice on the plateaus during the Late Weichselian. Our study highlights the ongoing glacial and periglacial morphological processes in an area of hard and weathering-resistant bedrock, situated in northern Svalbard

Holocene glacial history of Svalbard: Status, perspectives and challenges

© 2020 The Author(s) We synthesize the current understanding of glacier activity on Svalbard from the end of the Late Pleistocene (12,000 yrs. before present) to the end of the Little Ice Age (c. 1920 AD). Our glacier history is derived from the SVALHOLA database, the first compilation of Holocene geochronology for Svalbard and the surrounding waters, including over 1,800 radiocarbon, terrestrial cosmogenic nuclide and optically stimulated luminescence ages. Data have been categorized by geological setting, uniformly (re-)calibrated, quality assessed and ultimately used to constrain glacier fluctuations (deglaciation, ice free conditions, glacier re-advances and ice marginal positions). We advance existing knowledge by mapping the extent and distribution of ice-cover during the Holocene glacial maximum and the glacial minimum, as well as present retreat rates (and percentages) within Early Holocene fjord-systems. Throughout the Holocene, Svalbard glaciers have responded to a varying combination of climatic, environmental and dynamic driving factors which influence both the extent and behavior of ice margins. We discuss the complexities of glacier systems and their dynamics in response to changes in climate. This review provides a holistic state of the art of Holocene glaciers on Svalbard, suitable for orienting future works which address gaps in our current knowledge

Identificação, dinâmica da produção e potencial de uso do feromônio de agregação de Pseudopiazurus obesus (Boheman, 1838) (Coleoptera : Curculionidae)

Orientador : Paulo H.G. ZarbinDissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências Biológicas, Programa de Pós-Graduação em Ciências Biológicas (Entomologia). Defesa: Curitiba, 2005Inclui bibliografiaÁrea de concentraçao: EntomologiaResumo: A pesquisa objetivou identificar, determinar a dinâmica da produção e avaliar o potencial de uso do feromônio de agregação de Pseudopiazurus obesus (Boheman, 1838), (Coleoptera: Curculionidae), visando à possibilidade do uso desta alternativa no monitoramento e controle desta praga. O estudo consistiu em três fases, sendo a primeira envolvendo a criação dos insetos; a segunda a obtenção dos voláteis dos insetos e avaliação destes no comportamento dos co-específicos e a terceira abrangendo isolamento, identificação e avaliação da atividade biológica do feromônio sintético em laboratório. Ações complementares de pesquisa ainda foram desenvolvidas como a determinação da dinâmica da produção do feromônio e avaliação da captura dos espécimes em armadilhas a campo. Os principais resultados foram: machos e fêmeas são mais atraídos para voláteis de insetos machos adicionado a partes da planta hospedeira (caule fresco do mamoeiro), sugerindo ação sinergística e potencializando a atratividade de co-específicos; a liberação do feromônio inicia a partir do 18o DAE (dias após a emergência) e ocorre durante a escotofase, sendo observado o pico de produção 4 - 6 h após o seu início; machos virgens e acasalados são semelhantes quanto à produção de feromônio e esta é dependente da planta hospedeira; a duração da produção ocorre até aos 105 DAE; o feromônio é do tipo agregação; grandisal, grandisol e papaianol (composto majoritário, intermediário e minoritário, respectivamente), constituem as substâncias feromonais da espécie; as misturas ternárias e grandisal mostraram ser biologicamente ativos na atratividade de co-específicos; armadilhas colocadas a 1,50 m de altura capturaram mais espécimes em condições de campo.Abstract: The aim of this study was to isolate and identify the aggregation pheromone the papaya weevil, Pseudopiazurus obesus (Boheman, 1838), (Coleoptera: Curculionidae), in order to develop new monitoring and control methods against this pest. The study is based in three stages. The first stage was the rearing of papaya weevil; in the second stage, volatiles were obtained from males and females adults to be evaluated biological activity its in behavioral of the weevils; the third stage experiments were carried out isolation and identification of the aggregation pheromone and to evaluate the biological activity this compounds in behavioral of weevils. The main results was: male and female adults were attracted to volatiles obtained from male adults plus trunk pieces of the host plant. These results demonstrate that host plant volatiles, promote a sinergistic effect when added to male extracts; the male adults are the main responsible for the pheromone release, which starts from the 18th day after emerging; pheromone emission occurs at the scotophase, with a higher emission from 4h to 6h after the onset of the scotophase; there is no difference between pheromone emission from virgim or mated males, but there is difference among volatiles collected from males with or without food; pheromone release is affected by the food quality and decrease within time; occurring until the 105 day of life; three male-specific compounds: grandisal (main pheromone component), grandisol and papaianol are the pheromonals compounds; the ternary mixtures and grandisal show biological activity in both sexes of the papaya weevil; traps localized in 1,50 meter higher show best performance in the captures of weevils in field conditions

Glacial history of the Åsgardfonna Ice Cap, NE Spitsbergen, since the last glaciation

The response of glaciers and ice caps to past climate change provides important insight into how they will react to ongoing and future global warming. In Svalbard, the Holocene glacial history has been studied for many cirque and valley glaciers. However, little is known about how the larger ice caps in Svalbard responded to Late Glacial and Holocene climate changes. Here we use lake sediment cores and geophysical data from Femmilsjøen, one of Svalbard’s largest lakes, to reconstruct the glacial history of the Åsgardfonna Ice Cap since the last deglaciation. We find that Femmilsjøen potentially deglaciated prior to 16.1 ± 0.3 cal ka BP and became isolated from the marine environment between 11.7 ± 0.3 to 11.3 ± 0.2 cal ka BP. Glacial meltwater runoff was absent between 10.1 ± 0.4 and 3.2 ± 0.2 cal ka BP, indicating that Åsgardfonna was greatly reduced or disappeared in the Early and Middle Holocene. Deposition of glacial-meltwater sediments re-commenced in Femmilsjøen at c. 3.2 ± 0.2 cal ka BP, indicating glacier re-growth in the Femmilsjøen catchment and the onset of the Neoglacial. The glacier(s) in the Femmilsjøen catchment area reached sizes no smaller than their modern extents already at c. 2.1 ± 0.7 cal ka BP. Our results suggest that larger Svalbard ice caps such as Åsgardfonna are very sensitive to climate changes and probably melted completely during the Holocene Thermal Maximum. Such information can be used as important constraints in future ice-cap simulations

Postglacial relative sea level change and glacier activity in the early and late Holocene:Wahlenbergfjorden, Nordaustlandet, Svalbard

Publisher's version (útgefin grein).Sediment cores from Kløverbladvatna, a threshold lake in Wahlenbergfjorden, Nordaustlandet, Svalbard were used to reconstruct Holocene glacier fluctuations. Meltwater from Etonbreen spills over a threshold to the lake, only when the glacier is significantly larger than at present. Lithological logging, loss-on-ignition, ITRAX scanning and radiocarbon dating of the cores show that Kløverbladvatna became isolated from Wahlenbergfjorden c. 5.4 cal. kyr BP due to glacioisostatic rebound. During the Late Holocene, laminated clayey gyttja from lacustrine organic production and surface runoff from the catchment accumulated in the lake. The lacustrine sedimentary record suggests that meltwater only spilled over the threshold at the peak of the surge of Etonbreen in AD 1938. Hence, we suggest that this was the largest extent of Etonbreen in the (mid-late) Holocene. In Palanderbukta, a tributary fjord to Wahlenbergfjorden, raised beaches were surveyed and organic material collected to determine the age of the beaches and reconstruct postglacial relative sea level change. The age of the postglacial raised beaches ranges from 10.7 cal. kyr BP at 50 m a.s.l. to 3.13 cal. kyr BP at 2 m a.s.l. The reconstructed postglacial relative sea level curve adds valuable spatial and chronological data to the relative sea level record of Nordaustlandet.Sveinn Brynjólfsson and Sara Mollie Cohen are thanked for field assistance. Fieldwork and radiocarbon dates were funded by the Carlsberg Foundation (CF14-0756 to Schomacker) and Department of Arctic Geology, The University Centre in Svalbard (UNIS), respectively. Geospatial support was provided by the Polar Geospatial Center, and DEM(s) were created from DigitalGlobe, Inc., imagery and funded under National Science Foundation awards 1043681, 1559691, and 1542736. We thank Ole Bennike, Svend Funder, Antony Ruter, and Peter Ilsøe for macrofossil identification and lab assistance. The manuscript benefited from constructive review comments from Andy Emery. The publication charges for this article have been funded by a grant from the publication fund of UiT The Arctic University of Norway.Peer Reviewe

Dissolved Inorganic Geogenic Phosphorus Load to a Groundwater-Fed Lake: Implications of Terrestrial Phosphorus Cycling by Groundwater

The general perception has long been that lake eutrophication is driven by anthropogenic sources of phosphorus (P) and that P is immobile in the subsurface and in aquifers. Combined investigation of the current water and P budgets of a 70 ha lake (Nørresø, Fyn, Denmark) in a clayey till-dominated landscape and of the lake’s Holocene trophic history demonstrates a potential significance of geogenic (natural) groundwater-borne P. Nørresø receives water from nine streams, a groundwater-fed spring located on a small island, and precipitation. The lake loses water by evaporation and via a single outlet. Monthly measurements of stream, spring, and outlet discharge, and of tracers in the form of temperature, δ18O and δ2H of water, and water chemistry were conducted. The tracers indicated that the lake receives groundwater from an underlying regional confined glaciofluvial sand aquifer via the spring and one of the streams. In addition, the lake receives a direct groundwater input (estimated as the water balance residual) via the lake bed, as supported by the artesian conditions of underlying strata observed in piezometers installed along the lake shore and in wells tapping the regional confined aquifer. The groundwater in the regional confined aquifer was anoxic, ferrous, and contained 4–5 µmol/L dissolved inorganic orthophosphate (DIP). Altogether, the data indicated that groundwater contributes from 64% of the water-borne external DIP loading to the lake, and up to 90% if the DIP concentration of the spring, as representative for the average DIP of the regional confined aquifer, is assigned to the estimated groundwater input. In support, paleolimnological data retrieved from sediment cores indicated that Nørresø was never P-poor, even before the introduction of agriculture at 6000 years before present. Accordingly, groundwater-borne geogenic phosphorus can have an important influence on the trophic state of recipient surface water ecosystems, and groundwater-borne P can be a potentially important component of the terrestrial P cycle