E-MORB glasses from the Gakkel Ridge (Arctic Ocean) at 87°N: evidence for the Earth's most northerly volcanic activity

During the ARCTIC '91 expedition aboard RV Polarstern (ARK VIII/3) to the Central Arctic Ocean, a box corer sample on the Gakkel Ridge at 87 degrees N and 60 degrees E yielded a layer of sand-sized, dark brown volcanic glass shards at the surface of the sediment core. These shards have been investigated by petrographic, mineralogical, geochemical and radiogenic isotope methods. The nearly vesicle-free and aphyric glass shards bear only minute microphenocrysts of magnesiochromite and olivine (Fo(88-89)). Most glasses are fresh, although some show signs of incipient low-temperature alteration. From their shapes and sizes, the glass shards most likely formed by spalling of glassy rinds of a nearby volcanic outcrop. Geochemically, the glasses are relatively unfractionated tholeiites with E-MORB trace element compositions. Thus, they are quite similar to the previously investigated ARK IV/3-11-370-5 basalts from 86 degrees N. The Nd and Sr isotopic ratios of PS 2167-2 glasses are significantly lower than for ARK IV/3-11-370-5 basalts and suggest an isotopically heterogeneous mantle source of Gakkel Ridge MORE between 86 degrees and 87 degrees N. The positive Delta-8/4 Pb value (similar to 16) and high Sr-87/Sr-86 ratio (0.70270), found for PS 2167-2 glasses are similar to that of ARK IV/3-11-370-5 basalts and show the influence of the DUPAL isotopic anomaly in the high Arctic mantle. These results argue against the presence of an 'anti-DUPAL anomaly' in the mantle below the North Pole region and simple models of whole-mantle convection

Grain Size seperation and sediment mixing in Artic Ocean sediments: evidence from the strontium isotope systematic

The (87)Rb/(86)Sr and (87)Sr/(86)Sr ratios of Laptev Sea sediments, of Arctic Ocean sediments and of suspended particulate matter (SPM) from Siberian rivers (Lena and Khatanga) form 'pseudo-isochrons' due to grain-size separation processes which are referred to as 'Lena Mixing Envelope' (LME) and as 'Flood Basalt Envelope' (FBE). At the land-ocean transition the reduction of the particle velocity causes a deposition of coarser grained material and the contact with saline water enhances a precipitation of finer-grained material. The coarse-grained material is enriched in Sr showing less radiogenic (87)Sr/(86)Sr ratios whereas fine grained material is depleted in Sr relative to Rb showing more radiogenic (87)Sr/(86)Sr ratios, The experimentally determined spread of the (87)Rb/(86)Sr and (87)Sr/(86)Sr ratios as a function of grain size in one sediment sample is on the same order as the natural spread of the (87)Sr/(86)Sr ratios observed in all samples from the Arctic Ocean. Chemical Index of Alteration (CIA) for the Lena river SPM tend to confirm previous observations that chemical alteration is negligible in the Arctic environment. Thus, these 'pseudo-isochrons' reflect an average age and the average isotope composition in the river drainage area. Calculated apparent ages from the FBE reflect the age of the Siberian flood basalt of about 220 Ma and the initial ratio of 0.707(1) reflects their mantle origin. The age calculated from the LME of about 125 Ma reflects accidentally the Jurassic and Cretaceous age of the sediments drained by the Lena river and the initial ratio of 0.714(1) reflects the crustal origin of their source rocks. Comparison of geographical locations reveals that all samples from the eastern Laptev Sea (east of 120 degrees E) fall along the LME whereas all samples from the western Laptev Sea (west of 120 degrees E) fall between LME and FBE. Mixing calculations based on (143)Nd/(144)Nd measurements, not influenced by grain size, show that about 75% of the western Laptev Sea sediments originate from the Lena drainage area whereas about 25% of the sediments are delivered from the Siberian flood basalt province. Sediments from the central Arctic Ocean are isotopically related to the Lena drainage area and the Siberian flood basalt province. However, sediments from the Arctic Ocean margins close to Novaya Semlya, Greenland, the Fram Strait and Svalbard originate from sources not yet identified. (C) 1999 Elsevier Science B.V. All rights reserved

Распределение взвешенных частиц в Баренцевом море в конце зимы 2019 г.

Arctic summer and winter sea-ice extent is continuously declining as a result of climate change, affecting the hydrography and biogeochemical cycles on the seasonally ice-free Eurasian Shelves. The prolongation of the open-water season causes higher sediment resuspension and coastal erosion due to larger wind fetch and wave heights. This impacts the optical properties of the water column and hence biological productivity in this region. During “Transarktika-2019” leg 1 in late winter 2019, a comprehensive dataset of filtered water samples and optical data was collected throughout the central and northern Barents Sea. Combining suspended particulate matter concentrations obtained from water samples and optical data revealed a pronounced bottom nepheloid layer on the Barents Sea shelf even under ice-covered conditions. Moreover, the data indicate that the Franz Viktoria Trough could be a major pathway for sediment transport into the Eurasian Basin. Therefore, to link changes in sediment distribution and its impact on the ecosystem under a warming climate, further studies of sediment dynamics are required, particularly during winter.Летняя и зимняя площадь ледяного покрова в Арктике постоянно сокращается в результате изменения климата, воздействуя на гидрофизические и биогеохимические циклы на сезонно-безледных шельфах Евразийского бассейна. Возрастание продолжительности периода открытой воды приводит к увеличению образования взвешенного осадка и береговой эрозии в связи с увеличением ветровой нагрузки и высоты волн. Это влияет на оптические свойства водной толщи и, следовательно, на биологическую продуктивность в этом регионе. Во время первого этапа экспедиции «Трансарктика-2019» в конце зимы 2019 г. в центральной и северной частях Баренцева моря был собран обширный объем данных взвешенных частиц из фильтрованной воды и оптических данных. Совместный анализ данных о концентрации взвешенного вещества, полученных из проб воды, и оптических данных показал наличие ярко выраженного донного нефелоидного слоя на шельфе Баренцева моря даже в условиях наличия ледяного покрова. Более того, полученные результаты свидетельствуют о том, что желоб Франц-Виктория может быть основным путем переноса осадочного материала в Евразийский бассейн. Поэтому для того, чтобы связать изменения в распределении осадочных отложений и их влияние на экосистему в условиях потепления климата, необходимы дальнейшие исследования динамики осадочных отложений, особенно в зимний период

Anomalous variations in the thermohaline structure of the Arctic Ocean (Aus dem Russ. übersetzt)

Introduction: In the last two decades, significant changes have occurred in the Arctic Ocean as well as in the entire Arctic region. The ice cover of Arctic seas, which was gradually (linearly) decreasing from the beginning of the 20th century to the end of it [1], began to shrink rapidly in the 1990s and in the 21st century [2]. Salinity variations in the upper layer changed sign in different regions [3]. The temperature of Atlantic waters in the Arctic basin started to increase. At the end of the 1990s, stabilization of Atlantic water transport to the Arctic Basin was observed [4], but starting from 2004, the temperature of Atlantic waters in the Eurasian sub-basin increased even more and reached values that had not been observed here previously [5]. In 2007, extreme summer processes in the Arctic that followed this increase and anomalous state of the ice cover and upper layer of the ocean that were formed by the beginning of autumn put forward a pressing problem to evaluate the variation in the thermohaline structure of the Arctic Ocean as a whole

Unravelling legacy: a triadic actor-network theory approach to understanding the outcomes of mega events

Mega events have recently attracted the attention of social scientists due to their important role for festival capitalism, urban regeneration and political propaganda. Their planning stage often produces elaborate strategies for maximising the benefits before, during and after the actual event, which has given rise to interdisciplinary studies of event legacy and leveraging. This paper aims to advance ongoing debates on the outcomes of sports mega events by bringing together the literatures on mega event legacy, leveraging and actor-network theory. Drawing on a case study on the usage of the Queen Elizabeth Olympic Park, the main legacy of the London 2012 Olympic Games, the paper develops a novel conceptual framework for researching the multi-scalar outcomes of mega events and locating respective studies within the resulting wider research agenda. The proposed concept extends Preuss’ (2007) legacy cube in two ways by visualising its five research dimensions in the legacy rings and using three rather than two sub-dimensions per ring, thereby replacing the restrictive dyads of dualistic thinking through more comprehensive but still manageable triads of triadic thought (Jöns, 2006)

Изменения термохалинных характеристик трансполярной системы Северного Ледовитого океана

Extensive archives of observations have been used to analyze changes of water salinity, temperature and thickness of the upper,Atlanticand bottom layers in the Eurasian and Amerasian basins of the Arctic Ocean (AO) in 1950–1993 and 2007–2013. Multivariate models revealed the mechanisms of the coherency of the layer properties. An opposition of variations of thicknesses of the Atlantic layer from one side and the upper and bottom layers from the other side was established; it was also shown that the increase of temperature of the Atlantic layer is followed by salinification of the upper layer with a 4 year lag. Strong correlation of temperature and salinity of the upper and Atlantic layers with climatic indexes (like the North Atlantic Oscillation index) suggests the connection between processes in theArcticand lower latitude regions. The role of external hydrometeorological forcings in climatic changes of the AO state was revealed. The statistical multivariable model is capable of describing large-scale components of the Transpolar system of the AO which is an important contribution for understanding of the Arctic climate system.Обширные архивы данных наблюдений использованы для анализа изменений солености, температуры и толщины верхнего, атлантического и донного слоев в 1950–1993, 2007–2013 гг. в Евразийском и Амеразийском суббассейнах Северного Ледовитого океана (СЛО). Мультирегрессионные модели выявили механизмы сопряженности характеристик слоев. Выявлена оппозиция вариации толщин атлантического слоя, с одной стороны, и верхнего и донного слоев, с другой, а также зависимость, в которой за повышением температуры атлантических вод следует увеличение солености поверхностного слоя с запаздыванием в 4 года. Высокая корреляция между температурой и соленостью верхнего и атлантического слоев СЛО с индексами климатической изменчивости (например, с индексом Североатлантического колебания) свидетельствует о связанности процессов в Арктике и низких широтах. Установлена роль внешних гидрометеорологических воздействий в климатических изменениях состояния СЛО. Полученная статистическая малопараметрическая модель описывает функционирование макромасштабных составляющих Трансполярной системы СЛО, что является важным вкладом в понимание арктической климатической системы

The Laptev Sea system since the last glacial

There is growing concern about the rapidity and extent of climate change in recent decades in the Arctic. The changes already evident in the Arctic, such as the cyclonic shift in the distribution of Atlantic and Pacific water masses, atmospheric pressure and winds, as well as the thinning and retreat of the sea ice, will be felt first and most dramatically around the circum-Arctic shelves, which comprise nearly 50% of the area of the Arctic Ocean. In this context, the Laptev Sea and its Siberian hinterland are of particular interest because of their distance both from the Atlantic and Pacific Oceans. River discharge into the Laptev Sea constitutes a key source for the Arctic freshwater input, and it generates a shallow brackish layer on top of the halocline. The shallow Laptev Sea shelf is a major area of sea-ice production that links the Siberian shelves of the Arctic Ocean with the Nordic seas. During the Last Glacial Maximum, most of these shelves were above sea level and developed thick permafrost sequences; today they are submarine, after having experienced the postglacial late Pleistocene and Holocene transgression. The history of the submarine permafrost and its modern state of decay are largely unknown