Influence of temperature conditions in formation of end moraines in Fennoscandia and Svalbard

In the Finnmark region of northern Norway, end from Younger Drays and earlier periods appear as irregular mounds and ridges in a broad zone with a distinct distal margin. These moraines are similar in shape to end moraines formed in Svalbard today by melting of ice-cored moraines in front of subpolar glaciers under permafrost conditions. The end moraines in Finnmark were mkost likely formed in the same way in a permafrost climate during deglaciation. This might also be the case for moraines in the southernmost parts of Fennoscandia, in Denmark and southernmost Sweden. Cold-based ice during deglaciation in central parts of Fennoscandia is due to climatic conditions tens of thousands of years earlier. The period with climatic improvement after the Weicheselian maximum was too short to have any influence on the thermal conditions at the base of the ice-cap in the central areas.     

Budget calculations for polychlorinated biphenyls (PCBs) in the Northern Hemisphere ‐ a single‐box approach

Numerous studies show that the environmental concentrations of PCBs have been decreasing since the production and use of PCBs in most industrialised countries was banned in the 1970s. However, most of these studies have been conducted close to historical sources. The few studies conducted in remote locations detect no trend of decreasing concentrations over the past 20–30 years. These observations suggest that PCBs may be removed more slowly from the environment, when viewed from a global or hemispheric perspective. The present study estimates the mass fluxes of individual PCB congeners in the Northern Hemisphere in order to elucidate the most important removal processes and the rate of decrease one may expect with complete cessation of emissions. Atmospheric reaction lifetimes, open‐ocean settling fluxes and the pools and mobility of PCBs in the terrestrial environment are shown to be crucial parameters. However, the calculations identify important gaps of knowledge regarding predictions of environmental half‐lives of PCBs. The results suggest that highly chlorinated congeners such as PCB 153 and 180 may be persistent in the global environment with annual rates of decrease of less than 1%. The compiled environmental data also highlight large differences between the different PCB congeners. Although this paper is based on more than 800 PCB measurements it should be considered a starting point for further research aiming to quantify the global fate of toxic and persistent organic substances such as the PCBs.     

Climate variability and glacial processes in eastern Iceland during the past 700 years based on varved lake sediments

Striberger, J., Björck, S., Ingólfsson, Ó., Kjær, K. H., Snowball, I. & Uvo, C. B. 2010: Climate variability and glacial processes in eastern Iceland during the past 700 years based on varved lake sediments. Boreas, 10.1111/j.1502‐3885.2010.00153.x. ISSN 0300‐9483. Properties of varved sediments from Lake Lögurinn in eastern Iceland and their link to climate and glacial processes of Eyjabakkajökull, an outlet glacier of the Vatnajökull icecap, were examined. A varve chronology, which covers the period AD 1262–2005, was constructed from visual observations, high‐resolution images, X‐ray density and geochemical properties determined from X‐radiography and X‐ray fluorescence scanning. Independent dating provided by ¹³⁷Cs analysis and eight historical tephras verify the varve chronology. The thickness of dark‐coloured seasonal laminae, formed mainly of coarser suspended matter from the non‐glacial river Grímsá, is positively correlated (r=0.70) with winter precipitation, and our 743‐year‐long varve series indicates that precipitation was higher and more varied during the later part of the Little Ice Age. Light‐coloured laminae thickness, controlled mainly by the amount of finer suspended matter from the glacial river Jökulsáí Fljótsdal, increased significantly during the AD 1972 surge of Eyjabakkajökull. As a consequence of the surge, the ice‐dammed Lake Háöldulón formed and recurrently drained and delivered significant amounts of rock flour to Lake Lögurinn. Based on these observations, and the recurring cyclic pattern of periods of thicker light‐coloured laminae in the sediment record, we suggest that Eyjabakkajökull has surged repeatedly during the past 743 years, but with an increased frequency during the later part of the Little Ice Age.     

Configuration and timing of Ungava Bay ice streams, Labrador–Ungava, Canada

The prominent Ungava Bay landform swarm (UBLS), covering an area of ˜260000 km² south of Ungava Bay, Canada, is defined by drumlins, crag-and-tails, horned crag-and-tails and flutes indicating convergent ice flow towards Ungava Bay. The UBLS has been difficult to interpret in terms of ice-sheet configuration, dynamics and age. Aerial photograph and satellite image interpretations of the Labrador-Ungava region reveal a previously unrecognized level of complexity within the UBLS consisting of several well-defined segments, most interpreted as representing discrete stream-flow events. Each of the segments is characterized by one or more of the criteria (convergent flow patterns at their heads, attenuated till lineations and abrupt lateral margins) previously suggested as diagnostic for formation by fast-flowing ice (ice streams). The UBLS reflects the most direct and probably fastest contact (in terms of sediment transport) between the Laurentide Ice Sheet interior and the ocean. It is therefore a prime candidate for abrupt changes in glacial-age northwest Atlantic seafloor sedimentation.     

Thermal regime of a valley glacier, Erikbreen, northern Spitsbergen

The thermal regime of the valley glacier, Erikbreen, northern Spitsbergen (79°40'N, 12°30'E) was studied using radio-echo sounding and temperature measurements from eight boreholes ranging from 13.5 to 24 m. Radar images indicate a glacier with a two-layered thermal structure. A surface layer of cold ice, 20 to 60 m thick along the centre flow line, extends from an altitude above equilibrium line to the glacier front. This layer represents 20 to 35% of the glacier thickness, except at the floating front, where the cold layer is about 50%. The ice beneath the cold surface layer is interpreted to be temperate. Cold-based areas exist near the glacier margin and in some locations in the accumulation area; the ice is interpreted to be entirely temperate in central parts of the accumulation area at high altitude. Freezing of temperate ice at the base of the cold surface layer is probably the main mechanism of cold ice formation in the frontal parts of Erikbreen. Calculated heat fluxes based on the borehole measurements show that a steady state cold layer 25 to 30 m thick is likely, assuming a surface melting of 1.7 m/y and a maximum water content of 3%. In the frontal parts the calculated mean annual upward heat flux at 10 to 15 m depth is roughly 0.6 W/m².     

A diagnostic technique to differentiate between buried gleysolic and chernozemic B horizons

It is often difficult to establish in the field the origin of the B horizon of buried truncated palaeosols. However, infrared spectral configurations of electrodialyzed humic acids can be used as a diagnostic tool. Decreased absorption on passing from 2500 to 1800 cm^-1 indicates the presence of a chernozemic B horizon. The difference was explained on the basis of the conditions that existed at the time of the formation of these horizons. Burial did not change the structure of the humic substances responsible for the infrared spectral configurations.