Distribution of Chemical Constituents in Superimposed Ice from Austre Brøggerbreen, Spitsbergen

10 m and 2.3 m ice cores were obtained on Austre Brøggerbreen, Spitsbergen in Svalbard (78°53 ' N, 11°56 ' E, 450 m a.s.l.) in September 1994 and in March 1995, respectively. Stratigraphy, bulk density, pH, electrical conductivity, and major ions were obtained from the core samples.
The chemical effect of meltwater percolation through snow/ice is examined. Good correlation between Cl⁻ and Na⁺ was obtained. The ratio of Cl⁻ to Na⁺ was 1.14 which was nearly the same value as in bulk sea water. However, the variation of Cl⁻/Na⁺ shows that higher ratio occured in the bubble-free ice. Furthermore the Cl⁻ ions remain in higher concentration than SO ₄ ²⁻ or Na⁺ ions.     

Factors affecting the seed-setting success of Dryas octopetala in front of Brøggerbreen (Brøgger Glacier) in the high Arctic, Ny-Ålesund, Svalbard

To determine the factors restricting plant reproduction in front of a glacier, the gender expression and seed production of Dryas octopetala L. (Rosaceae) were observed, as well as the grazing pattern of reindeer on flowers, near Brøggerbreen (Brøgger Glacier), which is near Ny-Ålesund (78° 55'N, 11° 56'E), Svalbard. Three hundred shoots with flowers and flower buds were randomly tagged in early July 1996. Between then and the end of flowering in late July, 100 (33%) flowers and buds were grazed by reindeer. Out of the surviving flowers, 145 (76%) shoots had hermaphrodite flowers, while 45 (24%) shoots had male flowers without a developed gynocium. Male flowers, which appeared later than hermaphrodite flowers in the population, were significantly smaller than hermaphrodite flowers in dry weight. In the hermaphrodite flowers, moreover, smaller flowers showed lower dry-weight allocation to the gynoecium as compared to larger flowers. During the observation, hermaphrodite flowers did not produce any developed seeds under a natural condition (0% seed-set). Cross-pollinated flowers showed 8% seed-set. On the other hand, flowers which were artificially warmed in small greenhouses during the flowering period showed 60% seed-set, regardless of cross-pollination or autodeposition of pollen from anthers to stigma (self-pollination). Thus, it was found that grazing, gender variation in relation to the length of the growing season and the flower size, and - in the floweriing period - low temperature rather than pollinator limitation strongly affected the seed production of D. octopetala in the population studied.     

Origin of well-rounded gravels in glacial deposits from Brøggerhalvøya, northwest Spitsbergen: potential problems caused by sediment reworking in the glacial environment

Well-rounded gravels are described from moraine-mound complexes, diamicton forefields and modern englacial thrusts at the margins of four glaciers on the northern side of Brøggerhalvøya, northwest Spitsbergen. Their shape charcteristics are compared with modern and fossil glacigenic, modern beach and Early Weichselian beach gravels from this peninsula. The best discriminators of the well-rounded gravels have been found to be the percentage-frequency roundness histograms, the roundness mid-point and roundness range diagrams and the sphericity-roundness plots. It is concluded that the gravels have been derived by englacial thrusting from Early Weichselian or last interglacial beaches in the inner parts of the fjord and in the low level cirques when sea level reached at least 50m a.s.l. and deposited the beach gravels. The discrimination between gravel in basal diamictons, proglacial outwash and modern beaches is difficult as the reworking has resulted in little particle shape change. The potential major problem caused by reworking in the glacial environment is emphasised. especially when clast shape comparisons from modern environments to older sediments are used.     

Reconstruction of the mean specific mass balance of Vatnajökull (Iceland) with a Seasonal Sensitivity Characteristic

We present a Seasonal Sensitivity Characteristic (SSC) of Vatnajökull (Iceland), which consists of the sensitivity of the mean specific mass balance to monthly perturbations in temperature and precipitation. The climate in Iceland is predominantly maritime (high precipitation) although often the polar air mass influences the area. This results in temperature sensitivities that are high in summer and nearly zero during the winter months. In contrast, precipitation sensitivities are high in winter and low in summer. We use the SSC of Vatnajökull as a reduced mass balance model, with which we reconstruct the mass balance of Vatnajökull since 1825. The reduced model shows that changes in temperature and precipitation like the ones observed both have a significant impact upon the mass balance. The reconstructed mass balance records for two Icelandic glaciers correlate very well with mass balance records that are extracted from length records with a linear inverse model. This places confidence in both the reduced (forward) mass balance model and in the inverse model, although the forward method produces larger mass balance variations than the inverse method. For the south of Vatnajökull we find that after 1900, the length record is well explained by temperature variations alone, while another Icelandic glacier (Sólheimajökull) was also influenced by precipitation variations.     

The restructuring of London's labour force: migration and shifting opportunities, 1971–91

Summary The links between migration in and out of London and intergenerational social mobility are explored. Opportunities to enter high-grade jobs are greater in London, but so is the competition. The selectivity of migration explains the high social mobility associated with both in- and out-migration; those who stay in London are much less mobile, be they male or female. Black migrants to London do not share the fast escalator with white migrants, and London stayers come disproportionately from ethnic minority backgrounds. Socially mobile Londoners of both sexes leave far faster than the non-mobile, but women are less often 'creamed off'. Women with high-level jobs rarely leave; when they stay, they are less likely to leave the labour force. The selectivity of both types of migration concentrates 'under-achievement' on London stayers; racial discrimination may contribute to this outcome.     

Mass balance and changes of surface slope, crevasse and flow pattern of Erikbreen, northern Spitsbergen: an application of a geographical information system (GIS)

The polythcrmal valley glacier Erikbreen (79°40'N 12°30'E), northern Spitsbergen, was investigated in 1970 and 1990 using digital photogrammetry and digital elevation model (DEM) techniques. The bottom topography was derived from radio-echo soundings. Based on the DEM, mass balance and changes of surface slope, crevasse and flow pattern were evaluated, and internal ice deformation velocities were calculated. Calculations of the total mass balance show that Erikbreen has not been in equilibrium for the last 20 years. The average surface lowering was 0.38 m/a and the volume had decreased by 5% to 6% from 1970 to 1990 or on the average by 3.5 × 10⁻¹ water. The glacier surface subsided over the whole glacier area except in minor areas with northfacing slopes in the accumulation area. The surface slope and the crevasse pattern, however, did not change significantly during the 20-year-period, except in areas below 100 ma.s.l.     

Mass balance and area changes of four High Arctic plateau ice caps, 1959–2002

Abstract Small, stagnating ice caps at high latitudes are particularly sensitive to climatic fluctuations, especially with regard to changes in ablation season temperature. We conducted mass balance measurements and GPS area surveys on four small High Arctic plateau ice caps from 1999–2002. We compared these measurements with topographic maps and aerial photography from 1959, and with previously published data. Net mass balance (b_n) of Murray Ice Cap was ?0.49 (1999), ?0.29 (2000), ?0.47 (2001), and ?0.29 (2002), all in meters of water equivalent (m w.eq.). The mass balance of nearby Simmons Ice Cap was also negative in 2000 (b_n=?0.40 m w.eq.) and in 2001 (b_n=?0.52 m w.eq.). All four ice caps experienced substantial marginal recession and area reductions of between 30 and 47% since 1959. Overall, these icecaps lost considerable mass since at least 1959, except for a period between the mid‐1960s and mid‐1970s characterized regionally by reduced summer melt, positive mass balance, and ice cap advance. The regional equilibrium line altitude (ELA) is located, on average, above the summits of the ice caps, indicating that they are remnants of past climatic conditions and out of equilibrium with present climate. The ice caps reached a Holocene maximum and were several times larger during the Little Ice Age (LIA) and their current recession reflects an adjustment to post‐LIA climatic conditions. At current downwasting rates the ice masses on the Hazen Plateau will completely disappear by, or soon after, the mid‐21st century.     

The transport and mass balance of fallout radionuclides in Blelham Tarn, Cumbria (UK)

Although lake sediment archives are widely used for reconstructing historical records of atmospherically delivered pollutants, the quantitative relationship between fallout levels and their record in the sediments is complex and not well known. The original input signal from the atmosphere can be significantly distorted by mediating transport processes in the catchment, through the water column and within the sediments themselves. Since these processes also affect the fallout radionuclide ²¹⁰Pb commonly used to date sediments, a better understanding of their impact is also important to improving the accuracy and reliability of sediment dating. Blelham Tarn has been the subject of a number of palaeolimnological investigations using radiometric dating techniques since the early 1970s. More recently it was the site of a major study carried out within the EU Transuranics project concerning the long-term fate of fallout radionuclides in catchment/lake systems. This paper reviews the radiometric data from this study and uses the results to determine mass balances for fallout ²¹⁰Pb, ¹³⁷Cs and ^239+240Pu in Blelham Tarn, and their spatial distribution over the bed of the lake. Atmospheric fluxes were determined by measuring concentrations in rainwater and cumulative inventories in soil cores from non-eroding sites. Sediment records in a grid of 16 cores were used to determine the spatial distribution over the bed of the lake, and net inputs from the catchment. Mass balance calculations indicate that c. 47% of ²¹⁰Pb in the sediments derives from erosive inputs from the catchment. For ^239+240Pu the figure rises to 61%. Reduced amounts of ¹³⁷Cs in the sediments are attributed to greater losses of this radionuclide from the water column via the outflow due to its greater solubility. Inputs of radionuclides from the catchment are concentrated near one of the major input streams. Away from this part of the lake the sediment record is dominated by direct atmospheric fallout, though the detailed pattern is influenced by sediment focussing. A one parameter catchment/lake transport model is developed that incorporates the assumption that transport rates will decline with time as fallout on the catchment diffuses into the soil and becomes less available for removal. Values of the transport parameter were calculated for ²¹⁰Pb and ^239+240Pu and found to be comparable. The results suggest that it will take c. 11000 years to remove 50% of ^239+240Pu from the catchment to the lake.     

Study of annual mass balance(2011–2013) of Rikha Samba Glacier,Hidden Valley,Mustang, Nepal

Although Himalayan glaciers are of particular interest in terms of future water supplies, regional climate changes, and sea-level rises, little is known about them due to lack of reliable and consistent data. There is a need for monitoring these glaciers to bridge this knowledge gap and to provide field measurements necessary to calibrate and validate the results from different remote sensing operations. Therefore, glaciological observations have been carried out by the Cryosphere Monitoring Project(CMP) since September 2011 on Rikha Samba Glacier in Hidden valley, Mustang district in western Nepal in order to study its annual mass balance. This paper presents the first results of that study. There are 10 glaciers in Hidden Valley, named G1, G2, G3, up to G10. Of these, G5 is the Rikha Samba Glacier, which has the largest area(5.37 km2) in this valley and the highest and lowest altitudes(6,476 and 5,392 m a.s.l., respectively). The glacier mass balance discussed in this paper was calculated using the glaciological method and the equilibrium line altitude(ELA). The glacier showed a negative annual point mass balance along the longitudinal profile of its lower part from September 10, 2011 to October 3, 2012. Stake measurements from October 4, 2012 to September 30, 2013 indicated a negative areal average of annual mass balance-0.088±0.019 m w.e. for the whole glacier. Based on these observations, the ELA of the Rikha Samba Glacier is estimated at 5,800 m a.s.l. in 2013. This negative balance may be due to rising air temperatures in the region, which have been incrementally rising since 1980 accompanied by little or no significant increase in precipitation in that period. The negative mass balance confirms the general shrinking trend of the glacier.     

The failure mechanism of a Late Glacial Sturzstrom in the Subalpine Molasse (Leckner Valley, Vorarlberg, Austria)

A number of prehistoric landslides and rock avalanches occurred in the folded and faulted section of the Molasse Zone in Vorarlberg, Austria. Some developed into a Sturzstrom, defined as a ‘rapidly moving fluidised mass movement of large volumes of rock, derived from the disintegration of a falling rock mass, that spread under the influence of gravity’. Their impact on the landscape usually is related to obstruction of rivers and valleys.In this paper, we analyse the geomorphology and the failure mechanism of a relative small ‘Sturzstrom’. The failure mechanism can be described as a ‘buckling failure’. The morphological situation indicates that failure took place after local deglaciation by the end of the Upper Würm. The period of failure coincides with glacial and ice-marginal remnants, which developed between 15.000 and 14.600 BP. The lithological sequence and rock structure, as well as the impact of the processes related to the former glacial environment, were major causal conditions. The rock sequence consists of conglomerates, sandstone layers, and marls. Next to glacial scouring, which increased the inclination of the valley slopes, the effect of late-glacial unloading and postglacial processes, such as weathering and fluvial erosion, subsequently weakened the mass rock fabric until failure occurred.Discontinuity orientation measurements, geostructural and geomechanical conditions, and the former hydrological and geomorphological conditions support bucklings failure. In fact, three-hinge buckling may have occurred. The frontal section of the Sturzstrom consists mainly of large conglomerate blocks, averaging 1.5 m³ in volume, although megablocks, reaching of up to 4000 m³, are present as well. The volume of the entire Sturzstrom equals approximately 10×10⁷ m³. Present activity is only restricted to minor rock falls derived from the conglomerates and mudflows originating from the marl layers.     

Mapping the phases of Glacial Lake Algonquin in the upper Great Lakes region,Canada and USA,using a geostatistical isostatic rebound model

This study reviews Glacial Lake Algonquin, examines the Main and two “Upper Group” phases in northern Michigan and nearby Ontario, reports their spatial extents, and reassesses the lake history in light of isostatic rebound. Our paper presents the most accurate and detailed maps of Glacial Lake Algonquin in this region that have yet been published. Fieldwork was conducted at 243 ancient shoreline sites, which yielded position data that support geostatistical models that represent differentially upwarped water planes. Model parameters that describe water plane tilt are reported for the Main, Ardtrea and Upper Orillia phases. Geostatistical water plane models were used to adjust a digital contemporary elevation model, thereby creating a digital proglacial elevation model for each phase. Maps of these phases and the data that support them suggest (1) proto-Cockburn Island, Ontario existed as an islet in the lake that was deglaciated before the outlet at North Bay, Ontario was opened, (2) the Main and Ardtrea phases of the lake extended into the northern Lake Michigan basin, and (3) the Main and Ardtrea water planes intersect at places near Little Traverse Bay (by Lake Michigan) and Thunder Bay (by Lake Huron). Mapped isobases generally conform to those published in other works and suggest the regional pattern of isostatic adjustment has not changed substantially during the last 13,000 years.     

Sedimentological and Geomorphological Impacts of The Jökulhlaup (Glacial Outburst Flood) In January 2002 At Kverkfjöll, Northern Iceland

Jökulhlaups (glacial outburst floods) are common hazards in many glaciated environments. However, research on the controls on the sedimentological and geomorphological impact of jökulhlaups is rare. Developing a more comprehensive understanding of flood impacts may be useful for hazard identification, prediction and mitigation. This study determines the controls on the sedimentological and geomorphological impact of a jökulhlaup in January 2002 at Kverkfjöll, northern Iceland. This jökulhlaup, caused by geothermal activity, reached a peak discharge of 490 m³s^?1 as recorded at a permanent gauging station 40 km downstream from the glacier snout. However, reconstructed peak discharges in the proximal part of the jökulhlaup channel near the glacier snout indicate a peak discharge of 2590 m³s^?1. The jökulhlaup hydrograph was characterized by a rapid rising stage and a more gradual falling stage. As a result, sedimentary and geomorphological impacts included poorly sorted, structureless, matrix‐supported deposits; massive sand units; clast‐supported units; ice‐proximal cobbles, rip‐up clasts and kettle‐holes; and steep‐sided kettle‐holes. These features are proposed to be characteristic of rapid rising stage deposition. Additionally, large‐scale gravel bars and bedload sheets prograded and migrated during the rapid rising stage. The development of these bedforms was facilitated by high bedload transport rates, due to high discharge acceleration rates during the rapid rising stage. During the more prolonged falling stage, there was sufficient time for sediment incision and erosion to occur, exhuming cobbles, ice blocks and rip‐up clasts, and creating well‐defined terrace surfaces. This study provides a clearer understanding of hydrological and sedimentological processes and mechanisms operating during jökulhlaups, and helps to identify flood hazards more accurately, which is fundamental for hazard management and minimizing risk.     

Meteorological Observations in 1999 at the Arctic Station,Qeqertarsuaq (Godhavn), Central West Greenland/Evidence of a warmer climate around AD 600, Mittivakkat Glacier,South East Greenland

In october 1990 an automatic weather station was established at the Arctic Station (65° 15', 53°31'W), Qeqertarsuaq (Godhavn), Central West Greenland. The Station register parameters each 20 minutes, and the paramters have been described in an earlier paper in this journal by Nielsen et al.(1995). The present paper summarizes meteorological parameters during 1999.

During a field campaign in 1999, woody remains from Salix glauca were found on a nunatak, 515 m. a.s.l. on the Mittivakkat Glacier, South East Greenland. Radio carbon dating determined the age of a wood sample to AD 640. Together with analyses of macroscopic botanical remains and insect rests in peaty material found nearby, these results indicate, that a warmer climate prevailed near the glacier around AD 600. These findings are in accordance with temperature records based on studies of ice cores from the Greenland Ice sheet.     

Source parameters of large historical (1918–1962) earthquakes, South Island, New Zealand

We present the results of body waveform modelling studies for 17 earthquakes of M _w ≥5.7 occurring in the South Island, New Zealand region between 1918 and 1962, including the 1929 M _s = 7.8 Buller earthquake, the largest earthquake to have occurred in the South Island this century. These studies confirm the concept of slip partitioning in the northern South Island between strike-slip faulting in southwestern Marlborough and reverse and strike-slip faulting in the Buller region, but indicate that the zone of reverse faulting is quite localized. In the central South Island, all historical earthquakes appear to be associated with strike-slip faulting, although recent (post-1991) reverse faulting events suggest that slip partitioning also occurs within this region. The difference between historical and recent seismicity in the central South Island may also reflect stress readjustment occurring in response to the 1717 ad rupture along the Alpine fault. Within the Fiordland region (southwestern South Island) none of the historical earthquakes appears to have occurred along the Australian/Pacific plate interface, but rather they are associated with complex deformation of the subducting plate as well as with deformation of the upper (Pacific) plate. Two earthquakes in the Puysegur Bank region south of the South Island suggest that strike-slip deformation east of the Puysegur Trench is playing a major role in the tectonics of the region.