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Interplanetary shock-associated aurora
Get PDFInterplanetary shocks or solar wind pressure pulses have prompted impacts on Earth’s magnetospheric and ionospheric environment, especially in causing dynamic changes to the bright aurora in the polar ionosphere. The auroral phenomenon associated with shock impingements, referred to as shock aurora, exhibits distinct signatures differing from other geophysical features on the dayside polar ionosphere. Shock aurora provides a direct manifestation of the solar wind–magnetosphere–ionosphere interaction. Imagers onboard satellites can obtain the associated large-scale auroral characteristics during shock impingement on the magnetopause. Therefore, auroral data from satellites are very useful for surveying the comprehensive features of shock aurora and their general evolution. Nonetheless, the ground-based high temporal-spatial resolution all-sky imagers installed at scientific stations play an essential role in revealing medium- and small-scale characteristics of shock aurora. Here, we focus on shock aurora imaging signatures measured by imagers onboard satellites and ground-based all-sky imagers
Investigation of PMSE echoes characteristics using the discontinuous EISCAT UHF observation and its relation with space environment
Get PDFThe observations of Polar Mesosphere Summer Echoes (PMSE) were carried out using the sporadic data of EISCAT UHF radar during the summer season from 2004 to 2015. There were 25 h of PMSE echoes with EISCAT UHF radar. PMSE echoes were mostly observed only during the early morning and fore-noon time. Moreover, the PMSE echoes are positively correlated with Lyman α radiation, but the correlation is non-significant. The occurrence of PMSE echoes in the early morning and fore-noon time and there positive correlation with Lyman α radiation suggests that solar radiations might be one important factor for PMSE echoes in this study. Very weak positive, but statistically non-significant correlation is found between PMSE occurrence rate and the local geomagnetic K-indices. It is found that there is a matching between the variation in the occurrence rate of PMSE and noctilucent clouds (NLC) up to some extent and they are positively correlated. This positive correlation might support the earlier proposed idea about the role of ice particle size in producing PMSE echoes at higher frequencies
Late Maastrichtian Paleocene chronostratigraphy from Seymour Island, James Ross Basin, Antarctic Peninsula: Eustatic controls on sedimentation
Get PDFThe Paleocene (66–56 Ma) was a critical time interval for understanding the geological history in high palaeolatitudes after the end of Cretaceous event (recovery from mass extinction, palaeoclimate, global sea level changes, among others). The sedimentary succession from Seymour Island (Antarctic Peninsula) provides key reference material from this important phase of the early Cenozoic. A detailed age model is proposed for the López de Bertodano Formation (LBF), Sobral Formation (SF) and Cross Valley–Wiman Formation (CVWF) based on a new magnetostratigraphic section which integrates previous dinoflagellate cyst biostratigraphy, Iridium anomaly (K-Pg boundary), U-Pb zircon dating (airfall tuff) and strontium isotope values from macrofossils. The new composite magnetostratigraphic section, which includes the Cretaceous–Paleogene boundary, has been correlated to the GPTS from C29r up to C24r. The top of the LBF is confirmed as latest Maastrichtian to earliest Danian (~65.4 Ma) in age. The overlying SF is mostly Danian in age (~65.2– ~63 Ma) and CVWF is Selandian–Thatenian (~61.3–56.9 Ma). LBF, SF and CVWF are unconformity-bounded units (alloformations) that record the geological evolution of the James Ross Basin during a period of relative decreasing tectonism but coeval with volcanic activity. Unconformity based internal units have been recognized, dividing each formation into allomembers (LBF: Molluscan and Cenozoic; SF: A, B and C; CVWF: Díaz, Arañado, Bahía Pingüino). The new age model allows correlation of base-level changes with eustatic sea-level fluctuations. The bases of the SF and CVWF are correlated with the 65.3 and 61.5 Ma sea level lowstands
Very low biodiversity of top predators—seabirds and marine mammals—in the high Arctic Ocean
Get PDFDuring the ARK-XXIII/3 expedition of icebreaking RV Polarstern in the high Arctic Ocean (partim north of 73°N) from 25 August to 10 October 2008, 550 transect counts lasting 30 min were devoted to seabird and marine mammal counts from the bridge. In the whole area, the three most numerous species, kittiwake Rissa tridactyla, fulmar Fulmarus glacialis and Brünnich’s guillemot Uria lomvia represented 90% of the total of 12000 individuals registered, followed by ivory gull Pagophila eburnea, black guillemot Cepphus grylle and Ross’s gull Rodostethia rosea. Four geographical zones were recognized on the basis of number of species and density. Both were especially low in the deeper areas (mean depth of 3000 m), both ice-free and heavily ice-covered: 0.3 birds per 30 min count belonging to three and four species respectively. The most numerous species was kittiwake with 0.25 per count (50 individuals) in the ice-covered area. Pinniped numbers were very low as well, the most numerous of the four species tallied being 20 harp seals Phoca groenlandica and 10 ringed seal Pusa hispida. Seven polar bears Ursus maritimus were encountered. These observations were basically confirmed during 12 helicopter flights lasting one hour each with very low numbers: 50 kittiwakes and 13 harp seals, almost none in the ice-covered deep zone. A comparison between data obtained from ship and from helicopter seems however to reflect the importance of seabird followers including for long distances. The only cetaceans were two adult belugas Delphinapterus leucas tallied from helicopter
Methane increase over the Barents and Kara seas after the autumn pycnocline breakdown: satellite observations
Get PDFSeven operative thermal infrared (TIR) spectrometers launched at sun-synchronous polar orbits supply huge amounts of information about Arctic methane (CH4) year-round, day and night. TIR data are unique for estimating CH4 emissions from a warming Arctic, both terrestrial and marine. This report is based on publicly available CH4 concentrations retrieved by NOAA and NASA from spectra of TIR radiation delivered by EU IASI and US AIRS sounders. Data were filtered for high thermal contrast in the troposphere. Validation versus aircraft measurements at three US continental sites reveal a reduced, but still significant sensitivity to CH4 anomalies in the troposphere below 4 km of altitude. The focus area is the Barents and Kara seas (BKS). BKS is impacted with warm Atlantic water and mostly free of sea ice. It is a shelf area with vast deposits of oil and natural gas (~90% CH4), as well as methane hydrates and submarine permafrost. Although in summer AIRS and IASI observe no significant difference in CH4 between BKS and N. Atlantic, a strong, monthly positive CH4 spatial anomaly of up to 30 ppb occurs during late autumn–winter. One of explanations of this increase is a fall/winter pycnocline breakdown after a period of blocked mixing caused by a stable density seawater stratification in summer: enhanced mixing lets CH4 to reach the sea surface and atmosphere
Terahertz atmospheric windows for high angular resolution terahertz astronomy from Dome A
Get PDFAtmospheric transmission from Dome A, Antarctica, presents new possibilities in the field of terahertz astronomy, where space telescopes have been the only observational tools until now. Using atmospheric transmission measurements from Dome A with a Fourier transform spectrometer, transmission spectra and long-term stabilities have been analyzed at 1.461 THz, 3.393 THz, 5.786 THz and 7.1 THz, which show that important atmospheric windows for terahertz astronomy open for a reasonable length of time in the winter season. With large aperture terahertz telescopes and interferometers at Dome A, high angular resolution terahertz observations are foreseen of atomic fine-structure lines from ionized gas and a water ice feature from protoplanetary disks
Interaction of diabatic processes, large-scale eddies and the mean atmospheric circulation over the Atlantic, Arctic and Eurasia
Get PDFIn the last decade, the atmospheric part of the climate system experienced a shift from pronounced zonal to stronger meridional flow configurations and regionally diverse changes and trends. The climate system shows complex interactions and nonlinear behavior, manifested in global warming, rising ocean temperatures and the retreat of Arctic sea ice. Although atmospheric trends and changes are observed, underlying processes are not well understood. In this study we diagnose the interaction of large-scale atmospheric eddies and the mean flow with respect to diabatic heating and cooling processes that impact on the atmospheric advection of heat. For this purpose, the three-dimensional Eliassen-Palm flux theory is used in combination with an analysis of the thermodynamic equation, diabatic heating and cooling and heat advection. The most recent decades of observed winter climate are evaluated in terms of climatology and trends over the Atlantic, Arctic and Eurasia. The change of the atmospheric circulation and related processes differ between early and late winter. In early winter, the interaction of macro-turbulent eddies with the mean flow is inhibited at the Atlantic jet stream entrance region and atmospheric heat is meridionally advected into the Arctic, both related to strong high pressure anomalies. In late winter, these anomalies are inverted and a negative phase of the Arctic Oscillation with a more wavy mean flow and a tendency towards stronger meridionalization is observed
Effects of vegetation on the structure and diversity of soil bacterial communities in the Arctic tundra
Get PDFThe relatively simple vegetation of the Arctic tundra provides an ideal site in which to study the relationships between plants, bacterial communities and soil chemistry. Here, results of 16S rRNA gene sequencing of secondary Arctic brown soils collected from underneath colonies of Dryasoctopetala, Luzulaconfusa and Bistortavivipara in the Arctic tundra near Ny-Ålesund, Svalbard, Norway, reveal significant differences in bacterial communities related to soil environmental properties. Redundancy analysis shows that all measured geochemical factors were significant in structuring microbiomes, with strong correlations related to soil pH and organic matter contents. Vegetation is likely to affect the physical and chemical properties of the soil, which in turn affects the bacterial community and composition of the soil
The Sámi Arctic Strategy
Get PDFThe Saami Council has worked on Arctic issues since its early days. Seeing an increased national and international focus on the Arctic, the Saami Council has identified a need for an Arctic strategy to guide its work in this important area. This Arctic strategy aims to establish the Saami Council as an active partner for the civil Sámi society, governments, NGOs, IGOs, and others that, through international cooperation, will build a strong and sustainable Sápmi in the Arctic
Constraints on early Paleozoic magmatic processes and tectonic setting of Inexpressible Island, Northern Victoria Land, Antarctica
Get PDFDuring the Cambrian and Ordovician, widespread magmatic activity occurred in the Ross Orogen of central Antarctica, forming the Granite Harbor Intrusives and Terra Nova Intrusive Complex. In the Terra Nova Intrusive Complex, the latest magmatic activity comprised the emplacement of the Abbott Unit (508 Ma) and the Vegetation Unit (~475 Ma), which were formed in different tectonic settings. Owing to their similar lithological features, the tectonic transformation that occurred between the formation of these two units has not been well studied. Through a detailed geological field investigation and geochemical and geochronological analyses, four types of magmatic rock—basalt, syenite, mafic veins, and granite veins—were identified on Inexpressible Island, Northern Victoria Land. Our SHRIMP (Sensitive High Resolution Ion Micro Probe) zircon U–Pb ages of the basalt and the granite veins are 504.7 ± 3.1 and 495.5 ± 4.9 Ma, respectively. Major- and trace-element data indicate a continental-margin island-arc setting for the formation of these two rock types. The zircon U–Pb ages of the syenite and the monzodiorite veins are 485.8 ± 5.7 and 478.5 ± 4.0 Ma, respectively. Major- and trace-element compositions suggest a collisional setting for the former and an intracontinental extensional setting for the latter. These results elucidate the evolution from subduction to collision and intracontinental extension in Northern Victoria Land during the 20 Ma spanning the late Cambrian–Early Ordovician and improve our understanding of the tectonics and evolution of the Ross Orogen in the Transantarctic Mountains