Age and extent of the Barents and Kara ice sheets in Northern Russia

The youngest ice marginal zone between the White Sea and the Ural mountains is the W-E trending belt of moraines called the Varsh-Indiga-Markhida-Harbei-Halmer-Sopkay, here called the Markhida line. Glacial elements show that it was deposited by the Kara Ice Sheet, and in the west, by the Barents Ice Sheet. The Markhida moraine overlies Eemian marine sediments, and is therefore of Weichselian age. Distal to the moraine are Eemian marine sediments and three Palaeolithic sites with many C-14 dates in the range 16-37 ka not covered by till, proving that it represents the maximum ice sheet extension during the Weichselian. The Late Weichselian ice limit of M. G. Grosswald is about 400 km (near the Urals more than 700 km) too far south. Shorelines of ice dammed Lake Komi, probably dammed by the ice sheet ending at the Markhida line, predate 37 ka. We conclude that the Markhida line is of Middle/Early Weichselian age, implying that no ice sheet reached this part of Northern Russia during the Late Weichselian. This age is supported by a series of C-14 and OSL dates inside the Markhida line all of >45 ka. Two moraine loops protrude south of the Markhida line; the Laya-Adzva and Rogavaya moraines. These moraines are covered by Lake Komi sediments, and many C-14 dates on mammoth bones inside the moraines are 26-37 ka. The morphology indicates that the moraines are of Weichselian age, but a Saalian age cannot be excluded. No post-glacial emerged marine shorelines are found along the Barents Sea coast north of the Markhida line.     

Maximum extent of the Eurasian ice sheets in the Barents and Kara Sea region during the Weichselian

Based on field investigations in northern Russia and interpretation of offshore seismic data, we have made a preliminary reconstruction of the maximum ice-sheet extent in the Barents and Kara Sea region during the Early/Middle Weichselian and the Late Weichselian. Our investigations indicate that the Barents and Kara ice sheets attained their maximum Weichselian positions in northern Russia prior to 50 000 yr BP, whereas the northeastern flank of the Scandinavian Ice Sheet advanced to a maximum position shortly after 17 000 calendar years ago. During the Late Weichselian (25 000-10 000 yr BP), much of the Russian Arctic remained ice-free. According to our reconstruction, the extent of the ice sheets in the Barents and Kara Sea region during the Late Weichselian glacial maximum was less than half that of the maximum model which, up to now, has been widely used as a boundary condition for testing and refining General Circulation Models (GCMs). Preliminary numerical-modelling experiments predict Late Weichselian ice sheets which are larger than the ice extent implied for the Kara Sea region from dated geological evidence, suggesting very low precipitation.     

The last deglaciation of the Franz Victoria Trough, northern Barents Sea

A study of two piston cores and a 3.5 kHz seismic profile from the Franz Victoria Trough provides new stratigraphic, stable isotopic and foraminiferal AMS ¹⁴C data that help constrain the timing of ice-sheet retreat in the northern Barents Sea and the nature of the deglacial marine environment. Silty diamicton at the base of each core, interpreted as till or ice-marginal debris flow, suggests that the Barents ice sheet was grounded at the core sites (470 m water depth). Eight AMS ¹⁴C dates on sediment overlying the diamicton indicate that the ice sheet retreated from both core sites by 12.9 ka and that postglacial sedimentation began 10 ka ago. These dates, combined with a recently published ¹⁴C date from a nearby core, suggest that the Franz Victoria Trough may not have been deglaciated until c . 13 ka, 2000 years later than modeled ice-sheet reconstructions indicate. In the trough, oxygen isotopic ratios in planktonic foraminifera ^N. pachyderma (sinistral) were 0.5–0.750, lower during deglaciation than after, probably as a result of ice-sheet and/or iceberg melting. Foraminiferal assemblages suggest that Atlantic-derived intermediate water may have begun to penetrate the trough c . 13 ka ago.     

Dangerous ice phenomena on the lowland rivers of European Russia

The site amplification functions at 48 sites of NCR have been estimated in this study using the waveforms of locally recorded 23 earthquakes. Due to the absence of a suitable reference site in the region, the widely used horizontal-to-vertical spectral ratio (HVSR) technique has been used for this purpose. The maps showing the spatial distribution of predominant frequencies and the site amplifications at different frequencies corresponding to the natural frequencies of the different-storey buildings have been presented. The predominant frequencies in general are found to be in the range 2.5–7.5 Hz with an average of 4.4 Hz for the region having older alluvium sediments and in the range 1.1–6.4 Hz with an average of 3.3 Hz for the region with the younger alluvium deposits. The average value of the site amplifications for the frequency band 3.0–10.0 Hz is in the range 2.0–5.3 for the sites with significant soil cover, while the spectral amplification corresponding to the predominant frequency varies from 2.5 to 7.5 at most of the sites. The spectral amplification level lies in the range 2.0–3.0 for the sites with less or no sediment cover. The spectral amplification levels presented for the different-storey buildings may be used for the mitigation of seismic hazard in the region. The estimated site amplification functions may be used in the simulation of the site-specific strong ground motions and therefore useful for the evaluation of seismic hazard of a region.     

Dangerous ice phenomena on the lowland rivers of European Russia

In the Russian climate, the security of populations and economic security are often limited by dangerous ice phenomena. Not only ice-jam floods, but also some processes lead to the violation of operating conditions of various facilities (water intakes, roads, bridges) and damage hydraulic structures and shipping. Currently, rivers’ ice regime characteristics change under the influence of both natural (primarily climatic) and anthropogenic factors. Changes have been analyzed in detail on the basis of observations of 300 hydrological stations in the period from 1936 to 2013. Changes of ice phenomena hazards have been estimated. Hazard assessment of flooding caused by ice jams has been carried out for the Northern Dvina River reach from the Velikiy Ustyug City to Kotlas, the most problematic ice jam flooding area in European Russia. The modeling was performed on the basis of STREAM_2D software complex for current conditions and taking into account the possible construction of various protective structures. Methods for the prevention of negative impact of water at the site are examined.

     

Anomalous diurnal tides of the third degree in the Barents and Kara seas

Doklady Earth Sciences -     

Spring melt patterns in the Kara/Barents Sea: 1984

Ice-atmosphere interactions in the Seasonal Sea Ice Zone undergo rapid changes during the spring melt period with the transition from winter to summer conditions. The nature of these interactions is strongly dependent on the characteristics of the surface, which also experiences large changes during this same time period. This paper describes a methodology, based on Extended Principal Components Analysis, which is used to categorize the spatial and temporal patterns of surface change that occur in the Seasonal Sea Ice Zone during the spring/early summer. The methodology is demonstrated for the Kara/Barents Sea in spring 1984 using data from the Nimbus-7 Scanning Multichannel Microwave Radiometer. The analysis shows conditions in the Barents Sea to be largely controlled by ice advection, while the variance in the Kara Sea is dominated by surface melt.     

The last Scandinavian Ice Sheet in northwestern Russia: ice flow patterns and decay dynamics

Advance of the Late Weichselian (Valdaian) Scandinavian Ice Sheet (SIS) in northwestern Russia took place after a period of periglacial conditions. Till of the last SIS, Bobrovo till, overlies glacial deposits from the previous Barents and Kara Sea ice sheets and marine deposits of the Last Interglacial. The till is identified by its contents of Scandinavian erratics and it has directional properties of westerly provenance. Above the deglaciation sediments, and extra marginally, it is replaced by glaciofluvial and glaciolacustrine deposits. At its maximum extent, the last SIS was more restricted in Russia than previously outlined and the time of termination at 18-16 cal. kyr BP was almost 10 kyr delayed compared to the southwestern part of the ice sheet. We argue that the lithology of the ice sheets' substrate, and especially the location of former proglacial lake basins, influenced the dynamics of the ice sheet and guided the direction of flow. We advocate that, while reaching the maximum extent, lobe-shaped glaciers protruded eastward from SIS and moved along the path of water-filled lowland basins. Ice-sheet collapse and deglaciation in the region commenced when ice lobes were detached from the main ice sheet. During the Lateglacial warming, disintegration and melting took place in a 200-600 km wide zone along the northeastern rim of SIS associated with thick Quaternary accumulations. Deglaciation occurred through aerial downwasting within large fields of dead ice developed during successively detached ice lobes. Deglaciation led to the development of hummocky moraine landscapes with scattered periglacial and ice-dammed lakes, while a sub-arctic flora invaded the region.     

Palaeoceanographic changes in the northern Barents Sea during the last 16 000 years – new constraints on the last deglaciation of the Svalbard–Barents Sea Ice Sheet

The sediment core NP05‐71GC, retrieved from 360 m water depth south of Kvitøya, northwestern Barents Sea, was investigated for the distribution of benthic and planktic foraminifera, stable isotopes and sedimentological parameters to reconstruct palaeoceanographic changes and the growth and retreat of the Svalbard–Barents Sea Ice Sheet during the last ～16 000 years. The purpose is to gain better insight into the timing and variability of ocean circulation, climatic changes and ice‐sheet behaviour during the deglaciation and the Holocene. The results show that glaciomarine sedimentation commenced c. 16 000 a BP, indicating that the ice sheet had retreated from its maximum position at the shelf edge around Svalbard before that time. A strong subsurface influx of Atlantic‐derived bottom water occurred from 14 600 a BP during the Bølling and Allerød interstadials and lasted until the onset of the Younger Dryas cooling. In the Younger Dryas cold interval, the sea surface was covered by near‐permanent sea ice. The early Holocene, 11 700–11 000 a BP, was influenced by meltwater, followed by a strong inflow of highly saline and chilled Atlantic Water until c. 8600 a BP. From 8600 to 7600 a BP, faunal and isotopic evidence indicates cooling and a weaker flow of the Atlantic Water followed by a stronger influence of Atlantic Water until c. 6000 a BP. Thereafter, the environment generally deteriorated. Our results imply that (i) the deglaciation occurred earlier in this area than previously thought, and (ii) the Younger Dryas ice sheet was smaller than indicated by previous reconstructions.     

Distribution of clay minerals in surface sediments from the eastern Barents and south-western Kara seas

Surface samples from the eastern Barents and south-western Kara seas have been analysed for clay mineralogy. Transport paths, the role of regional sources and local bedrock outcrops and the influence of hydrodynamic and glacigenous processes for clay distribution on the shelves are discussed in relation to central Arctic Ocean deep sea and sea ice sediments. Franz Josef Land and Novaya Zemlya show significantly different clay mineral associations. Although smectite concentrations are fairly high, Franz Josef Land can be excluded as a source for central Arctic sea ice sediments, which are relatively rich in smectite. In the Kara Sea, smectite concentrations in coastal sediments surpass even the Franz Josef Land concentrations. The large cyclonic gyre in the eastern Barents Sea between Novaya Zemlya and Franz Josef Land, which serves as a mixing zone between Arctic and North Atlantic water, is apparently reflected within the smectite distribution pattern. With the exception of Franz Josef Land, the area of investigation is typically low in kaolinite. In particular, coastal areas and areas north of Novaya Zemlya, influenced by the inflow of Arctic waters, show the lowest kaolinite concentrations. A high kaolinite occurrence within the Nansen Basin is most probably related to Franz Josef Land and emphasizes the importance of long-range downslope transport of sediments across the continental slope. The surface water circulation pattern in close interaction with local outcrops onshore Novaya Zemlya and locally restricted occurrences within the eastern Barents Sea significantly alter the illite dispersal pattern. Illite concentrations are lowest around Franz Josef Land. Chlorite is generally low in the area of investigation. Submarine outcrops and important chlorite occurrences onshore Novaya Zemlya bias its distribution pattern.     

The Barents Sea Ice Sheet — A model of its growth and decay during the last ice maximum

On the basis of geomorphological and sedimentological data, we believe that the entire Barents Sea was covered by grounded ice during the last glacial maximum. ¹⁴C dates on shells embedded in tills suggest marine conditions in the Barents Sea as late as 22 ka BP; and models of the deglaciation history based on uplift data from the northern Norwegian coast suggest that significant parts of the Barents Sea Ice Sheet calved off as early as 15 ka BP. The growth of the ice sheet is related to glacioeustatic fall and the exposure of shallow banks in the central Barents Sea, where ice caps may develop and expand to finally coalesce with the expanding ice masses from Svalbard and Fennoscandia.The outlined model for growth and decay of the Barents Sea Ice Sheet suggests a system which developed and existed under periods of maximum climatic deterioration, and where its growth and decay were strongly related to the fall and rise of sea level.     

Modeling of pleistocene European ice sheets: Some experiments with simple mass-balance parameterizations

A vertically integrated ice-flow model suitable for use in climate studies is formulated. Large continental ice sheets may be characterized by two fundamental quantities: the height-to-width ratio, and the steepness of the edge. So it is natural to develop a model containing two parameters that can be chosen to give the right values of those characteristic quantities. The result is a model that is close to M. A. W. Mahaffy's (Journal of Geophysical Research, 81, 1059–1066 (1976)). The model is used to study glaciation in Europe. Dropping the level of zero mass balance creates small stable ice caps in the Alps and the Scandinavian mountains. If the drop exceeds 600 m (with respect to present-day conditions), the feedback between ice-sheet height and mass balance becomes dominating and the Fennoscandian Ice Sheet keeps growing. It does not reach an equilibrium state within 60,000 yr. An experiment simulating rapid onset of a glacial cycle shows that the growth of ice volume in Europe is smaller than that in northern America (J. T. Andrews and M. A. W. Mahaffy, Quaternary Research, 6, 167–183 (1976)). After 10,000 yr, the volume of the Fennoscandian Ice Sheet (2 × 10¹⁵ m³) is about half the volume of the Laurentide Ice Sheet. This leaves the “observed” sea-level lowering in the period 125,000–115,000 yr B.P. (estimates center around 50 m) unexplained.     

Extent of the last ice sheet in northern Scotland tested with cosmogenic 10Be exposure ages

The extent of the last British–Irish Ice Sheet (BIIS) in northern Scotland is disputed. A restricted ice sheet model holds that at the global Last Glacial Maximum (LGM; ca. 23–19 ka) the BIIS terminated on land in northern Scotland, leaving Buchan, Caithness and the Orkney Islands ice‐free. An alternative model implies that these three areas were ice‐covered at the LGM, with the BIIS extending offshore onto the adjacent shelves. We test the two models using cosmogenic ¹⁰Be surface exposure dating of erratic boulders and glacially eroded bedrock from the three areas. Our results indicate that the last BIIS covered all of northern Scotland during the LGM, but that widespread deglaciation of Caithness and Orkney occurred prior to rapid warming at ca. 14.5 ka. Copyright © 2008 John Wiley & Sons, Ltd.     

Freshwater and Atlantic water inflows to the deep northern Barents and Kara seas since ca 13 C ka: : foraminifera and stable isotopes

Foraminiferal stable isotopes and assemblages from Franz Victoria and St. Anna troughs provide a valuable record of freshwater and Atlantic Water flows to the northern Barents and Kara seas from deglaciation to present. The δ¹⁸O and δ¹³C of planktonic Neogloboquadrina pachyderma (s) and benthic Elphidium excavatum were up to 1.4‰ lower than present at ca 13, 11.5, and 10 ¹⁴C ka (global sea-level corrected), mostly reflecting substantial freshwater inputs coincident with glacial–marine sediment deposition. Cassidulina teretis exceeded 40% of benthic foraminifera ca 13 and 10 ¹⁴C ka, indicating subsurface penetrations of Atlantic Water. The transition to postglacial marine conditions is marked by a 1‰ rise in foraminiferal δ¹⁸O and a sharp fall in % C. teretis soon after 10 ¹⁴C ka. These changes imply reduced inputs of freshwater and Atlantic Water. Subsequent isotopic and foraminiferal assemblage variations reflect changing Atlantic Water conditions “upstream” in the Nordic Seas and shifts between the warm Fram Strait and cold Barents Sea branches of Atlantic Water. We hypothesize that glacial-isostatically induced deepening by up to 150 m influenced Atlantic Water inflows to the northern Barents Sea during deglaciation and the Holocene. Thus, effects of isostatic recovery have to be factored into paleoceanographic reconstructions.     

Correlation and interpretation of paleosols and loess across European Russia and Asia over the last interglacial-glacial cycle

Loess-paleosol sequences of the last interglacial-glacial cycle are correlated from European Russia to central Siberia and the Chinese Loess Plateau. During cold periods represented by marine oxygen isotope stages (OIS) 2 and 4, loess deposition dominated in the Russian Plain and the Loess Plateau. In central Siberia, loess deposition took place also, but five to seven thin, weakly developed paleosols are identified in both stages. OIS 3, in the Chinese Loess Plateau near Yangchang, consists of a loess bed that is flanked by two weakly developed paleosols. At Kurtak, Siberia, OIS 3 is represented by two distinct, stacked paleosols with no loess bed separating the paleosols. In the Russian Plain, OIS 3 consists of a single, possibly welded paleosol, representing upper and lower stage-3 climates. Brunisols and Chernozems dominate the profiles in China and Siberia, whereas Regosols, Luvisols, and Chernozems are evident in the northern and southern Russian Plain, respectively. OIS 5 is represented in China and the Russian Plain by pedo complexes in a series of welded soils, whereas in contrast, the Kurtak site consists of six paleosols with interbedded loess. The paleosols consist largely of Brunisols and Chernozems. Although the three areas examined have different climates, geographical settings, and loess source areas, they all had similar climate changes during the last interglacial-glacial cycle.     

Continental ice sheets and the planetary radiation budget

The interaction between continential ice sheets and the planetary radiation budget is potentially important in climate-sensitivity studies. A simple ice-sheet model incorporated in an energybalance climate model provides a tool for studying this interaction in a quantitative way. Experiments in which the ice-sheet model is coupled step by step to the climate model show that ice sheets hardly affect the zonal mean radiation balance because the albedo feedback due to sea ice and snow cover is dominating. The model requires a 5% drop in the solar constant to create ice sheets of ice-age size.If the feedback between surface elevation and ice-mass balance is included (in a very crude way), the ice-sheet size (L, measured southward from 70°N) becomes much more sensitive to in insolation. For a range of normalized solar constants, roughly from 0.98 to 1.02, two stable solutions exist: L 0 and L 2000 km. This result demonstrates that the response of ice sheets to insolation variations is far from linear. It also stresses the need for explicit modeling of the ice-mass balance of ice sheets, particularly its dependence on surface elevation.     

Age-specific net migration patterns in the municipal formations of Russia

This paper analyses the spatial patterns of internal migration in Russia using data on net migration gain/loss in 2200 municipal formations (MFs) in Russia for the 2012–2013 period. These MFs are grouped into age categories that correspond with different life-course stages. We define 16 classes of MFs with similar migration balance patterns for multiple age groups and characterize the most typical classes. The results of our analysis show that age-specific migration patterns are determined by the spatial characteristics of MFs—in particular, a municipality’s localization in the centreperiphery system and the advantages of the geographic location (e.g., resort area, natural resources). We find that a city’s population size and administrative status are also important migration factors. In addition, we reveal differences in inter-regional and intra-regional migration and define their structural characteristics. An analysis of age-specific net migration contributes to our understanding of internal migration factors and allows us to assess the impact of migration on a municipality’s age structure. In large cities and regional centres, migration results in younger populations, while in peripheral areas, it speeds up population ageing. In most of the MFs that we analysed, the migration of youth and adults ‘moves’ in opposite directions. This factor accelerates the impact of migration on the population age structure in areas of destination and origin and significantly influences a municipality’s current and prospective demographic parameters as well as the population’s patterns of settlement and spatial concentration or de-concentration both nationally and regionally.