Portlandia-dominated Communities in the Arctic: Taxonomic Composition and Structure along the Geographical Gradient

Abstract. Ozone sounding databases for two stations, So-dankylä (67° N, 27° E) and Ny-Ålesund (79° N, 12° E) were used in order to investigate the generation of layering in the upper and middle troposphere of the Arctic. We concentrated on dry, ozone-rich and stable layers observed below the thermal tropopause under light wind conditions. This condition ensures that the observed layer is not a tropopause fold, a well-known phenomenon that develops within frontal zones near the jet stream. Selection criteria for ozone, humidity and stability anomalies of the tropopause fold detection algorithm were used here to pick out for detailed studies the most pronounced examples of laminae. For all these cases the meteorological situations were investigated in order to establish the origin of the observed layers. We found that layers could be classified into two groups. Laminae of the first group were observed equatorward of the jet stream and those of a second group were observed poleward of the jet. The meteorological situation for the first group resembles that for equatorward stratospheric streamer propagation. It was found that this group accounts for only a small fraction of the layers observed at Sodankylä and for none of those observed at Ny-Ålesund during the period investigated. A large case-to-case variability in the synoptic situation was observed for the second group of laminae, which were detected northward of the jet stream. Nevertheless, in about half of the cases, streamers of tropospheric air were found in the vicinity of the stations on the isentropic surfaces just above the detected stratospheric layers. Back trajectory analyses showed that these layers originated in the vicinity of the polar jet stream. We suppose that laminae-like structures in the troposphere were caused, in both groups, by equatorward (poleward) advection of the stratospheric (tropospheric) air, together with differential vertical shear. Forward-trajectory calculations suggest that, subsequently, a part of the stratospheric layers can mix irreversibly into the troposphere.Key words. Atmospheric composition and structure (pressure, density, and temperature; troposphere-composition and chemistry)

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Observation of an unusual mid-stratospheric aerosol layer in the Arctic: possible sources and implications for polar vortex dynamics

Annales Geophysicae ◽

10.5194/angeo-21-1057-2003 ◽

2003 ◽

Vol 21 (4) ◽

pp. 1057-1069 ◽

Cited By ~ 22

Author(s):

M. Gerding ◽

G. Baumgarten ◽

U. Blum ◽

J. P. Thayer ◽

K.-H. Fricke ◽

...

Keyword(s):

Middle Atmosphere ◽

Water Solution ◽

Polar Vortex ◽

Atmospheric Temperature ◽

Stratospheric Aerosol ◽

Atmospheric Composition ◽

The Arctic ◽

Aerosol Layer ◽

Particle Sedimentation ◽

Composition And Structure

Abstract. By the beginning of winter 2000/2001, a mysterious stratospheric aerosol layer had been detected by four different Arctic lidar stations. The aerosol layer was observed first on 16 November 2000, at an altitude of about 38 km near Søndre Strømfjord, Greenland (67° N, 51° W) and on 19 November 2000, near Andenes, Norway (69° N, 16° E). Subsequently, in early December 2000, the aerosol layer was observed near Kiruna, Sweden (68° N, 21° E) and Ny-Ålesund, Spitsbergen (79° N, 12° E). No mid-latitude lidar station observed the presence of aerosols in this altitude region. The layer persisted throughout the winter 2000/2001, at least up to 12 February 2001. In November 2000, the backscatter ratio at a wavelength of 532 nm was up to 1.1, with a FWHM of about 2.5 km. By early February 2001, the layer had sedimented from an altitude of 38 km to about 26 km. Measurements at several wavelengths by the ALOMAR and Koldewey lidars indicate the particle size was between 30 and 50 nm. Depolarisation measurements reveal that the particles in the layer are aspherical, hence solid. In the mid-stratosphere, the ambient atmospheric temperature was too high to support in situ formation or existence of cloud particles consisting of ice or an acid-water solution. Furthermore, in the year 2000 there was no volcanic eruption, which could have injected aerosols into the upper stratosphere. Therefore, other origins of the aerosol, such as meteoroid debris, condensed rocket fuel, or aerosols produced under the influence of charged solar particles, will be discussed in the paper. Trajectory calculations illustrate the path of the aerosol cloud within the polar vortex and are used to link the observations at the different lidar sites. From the descent rate of the layer and particle sedimentation rates, the mean down-ward motion of air within the polar vortex was estimated to be about 124 m/d between 35 and 30 km, with higher values at the edge of the vortex.Key words. Atmospheric composition and structure (aerosols and particles; middle atmosphere composition and chemistry) – meteorology and atmospheric dynamics (middle atmosphere dynamics)

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Cloud microphysical characteristics versus temperature for three Canadian field projects

Annales Geophysicae ◽

10.5194/angeo-20-1891-2002 ◽

2002 ◽

Vol 20 (11) ◽

pp. 1891-1898 ◽

Cited By ~ 9

Author(s):

I. Gultepe ◽

G. A. Isaac ◽

S. G. Cober

Keyword(s):

General Circulation ◽

Research Study ◽

Liquid Water Content ◽

Atmospheric Composition ◽

The Arctic ◽

Bay Of Fundy ◽

Arctic Clouds ◽

Composition And Structure ◽

In Situ Observations

Abstract. The purpose of this study is to better understand how cloud microphysical characteristics such as liquid water content (LWC) and droplet number concentration (Nd) change with temperature (T). The in situ observations were collected during three research projects including: the Radiation, Aerosol, and Cloud Experiment (RACE) which took place over the Bay of Fundy and Central Ontario during August 1995, the First International Regional Arctic Cloud Experiment (FIRE.ACE) which took place in the Arctic Ocean during April 1998, and the Alliance Icing Research Study (AIRS) which took place in the Ontario region during the winter of 1999–2000. The RACE, FIRE.ACE, and AIRS projects represent summer mid-latitude clouds, Arctic clouds, and mid-latitude winter clouds, respectively. A LWC threshold of 0.005 g m-3 was used for this study. Similar to other studies, LWC was observed to decrease with decreasing T. The LWC-T relationship was similar for all projects, although the range of T conditions for each project was substantially different, and the variability of LWC within each project was considerable. Nd also decreased with decreasing T, and a parameterization for Nd versus T is suggested that may be useful for modeling studies.Key words. Atmospheric composition and structure (cloud physics and chemistry) – Meteorology and atmospheric dynamics (climatology; general circulation)

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Relationship between marine epilithic diatoms and environmental variables in oligotrophic bay, NE Mediterranean

Mediterranean Marine Science ◽

10.12681/mms.14151 ◽

2018 ◽

pp. 223 ◽

Cited By ~ 2

Author(s):

DUBRAVKA HAFNER ◽

ANA CAR ◽

NENAD JASPRICA ◽

TATJANA KAPETANOVIĆ ◽

IRIS DUPČIĆ RADIĆ

Keyword(s):

Taxonomic Composition ◽

Diatom Community ◽

Silicate Concentration ◽

Factors Influencing ◽

Composition And Structure ◽

Infraspecific Taxa ◽

Monthly Distribution ◽

Ne Mediterranean ◽

The Difference ◽

Epilithic Diatom

The taxonomic composition and structure of a marine epilithic diatom community were sampled from the bottom of the two sites at monthly intervals from January to December 2011 in the small semi-enclosed oligotrophic Neum Bay in Bosnia and Herzegovina (Middle Adriatic). Altogether, 264 diatom taxa (species and infraspecific taxa) within 69 genera were identified. Among them, 149 and 203 taxa occurred in samples from the shallow (0.5 m depth) and deep (8 m depth) sites, respectively. The monthly distribution of most of the diatoms was irregular and high numbers of sporadic taxa were found. SIMPER analysis indicated that the difference between shallow and deep sites could be largely attributed to the frequently recorded diatom taxa and those with high percentage abundances. They were Halamphora coffeiformis, Caloneis excentrica, Cocconeis scutellum var. scutellum, Licmophora flabellata, Licmophora gracilis, Licmophora sp., Navicula abunda, Rhabdonema adriaticum, and Striatella unipunctata. Canonical Correspondence Analysis (CCA) showed that temperature, oxygen saturation (O2/O2′), silicate concentration (SiO4), and salinity were the most important factors influencing diatom community structure in the bay.

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STRUCTURE OF TRILOBITE COMMUNITIES ALONG A DELTA-MARINE GRADIENT (LOWER ORDOVICIAN; NORTHWESTERN ARGENTINA)

Palaios ◽

10.2110/palo.2020.013 ◽

2021 ◽

Vol 36 (2) ◽

pp. 39-52

Author(s):

FERNANDA SERRA ◽

DIEGO BALSEIRO ◽

ROMAIN VAUCHER ◽

BEATRIZ G. WAISFELD

Keyword(s):

Taxonomic Composition ◽

Ecological Niches ◽

Marine Environments ◽

Key Factors ◽

Physiological Conditions ◽

Marine Deposits ◽

Shelf Slope ◽

Composition And Structure ◽

Lower Ordovician ◽

Nested Structure

ABSTRACTThroughout their long history, trilobites occupied various ecological niches, colonizing a wide variety of marine environments. However, the paleoecology of this group is mostly based on shelf–slope environments and less is known about their distribution in marginal environments. To understand how trilobite communities respond to a deltaic influence, we studied changes in the taxonomic composition and structure of a diverse and well-known Lower Ordovician olenid-dominated fauna from the Argentine Cordillera Oriental along a delta–marine gradient. Cluster analysis revealed two distinct associations, and ordination analysis revealed a clear biotic gradient within each. The ecological structure and diversity trends of both associations follow a predictable response to a depth-related gradient. Impoverished communities with a highly nested structure characterize the lower offshore, whereas rich and even communities occur in the upper offshore. The trend towards higher diversity and greater taxonomic turnover in shallower environments corresponds to greater habitat heterogeneity. Towards the other extreme, only the ubiquitous genus Jujuyaspis was a successful colonizer in deltaic settings. This marked contrast with the more diverse and abundant assemblages of fully marine deposits indicates stressful physiological conditions in marginal-marine environments, where alternating and contrasting normal-marine to brackish-water conditions and high input of siliciclastic material were among the key factors controlling the distribution of these early trilobite communities.

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Diatomic flora of Lake Tikozero in the Holocene

Issues of modern algology (Вопросы современной альгологии) ◽

10.33624/2311-0147-2020-3(24)-24-31 ◽

2020 ◽

pp. 24-31

Author(s):

Anna L. Kosova ◽

Dmitrii B. Denisov

Keyword(s):

Preliminary Data ◽

Taxonomic Composition ◽

Eastern Coast ◽

Benthic Species ◽

Diatom Analysis ◽

Composition And Structure ◽

Murmansk Region ◽

Littoral Species ◽

Diatom Complexes ◽

Alkaline Waters

Preliminary data of micropaleontological (diatom) study of sediments of Lake Tikozero located on the eastern coast of Lake Yokostrovskaya Imandra (Murmansk region) are presented. Based on the results of diatom analysis, the taxonomic composition and structure of diatom complexes were studied, the stages of the development of the ecosystem of the lake were established. The studied lake was characterized by the dominance of benthic forms and fouling in the composition of paleosocial communities. Upward in the column of sediments, there is a change in indicator groups with respect to pH: the proportion of acidophils decreases from 62% to 18%, and the proportion of alkaliphiles increases from 5% to 40%. A change in the dominant diatom complex was revealed: the acidophilic benthic species Brachysira zellensis (Grunow) Round & D.G. Mann is replaced by the littoral species Staurosira construens Ehrenberg, which prefers slightly alkaline waters.

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Biostratigraphy of the upper jurassic of the Verkh-Tarskaya drilling area (South of Western Siberia in foraminifera)

Недропользование. Горное дело. Направления и технологии поиска, разведки и разработки месторождений полезных ископаемых. Экономика. Геоэкология: Материалы XVI международной конференции (20-24 апреля 2020, Новосибирск) ◽

10.18303/b978-5-4262-0102-6-2020-009 ◽

2020 ◽

Author(s):

Ekaterina V. Zaychikova ◽

Keyword(s):

Western Siberia ◽

Upper Jurassic ◽

Taxonomic Composition ◽

Composition And Structure

The study of the taxonomic composition of foraminifera in the wells of the Verkh-Tarskaya drilling area formed the basis of this study. This made it possible to clarify the content of the complexes and trace the zones and layers with foraminifera. The biostratigraphic characteristics of the middle oxfordian-lower volgian sediments are also presented in the work, and changes in the taxonomic composition and structure of foraminifera complexes from wells in the Verkh-Tarsky district.

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<i>Letter to the Editor:</i> A strange cloud in the Arctic summer stratosphere 1998 above Esrange (68°N), Sweden

Annales Geophysicae ◽

10.1007/s00585-000-0505-0 ◽

2000 ◽

Vol 18 (4) ◽

pp. 505-509 ◽

Cited By ~ 2

Author(s):

J. Siebert ◽

C. Timmis ◽

G. Vaughan ◽

K. H. Fricke

Keyword(s):

Potential Temperature ◽

Atmospheric Dynamics ◽

Atmospheric Composition ◽

The Arctic ◽

Back Trajectory ◽

Eastern Canada ◽

Composition And Structure ◽

Middle Atmospheric Dynamics ◽

Thin Cloud ◽

The University

Abstract. When the University of Bonn lidar on the Esrange (68°N, 21°E), Sweden, was switched on in the evening of July 18, 1998, a geometrically and optically thin cloud layer was present near 14 km altitude or 400 K potential temperature, where it persisted for two hours. The tropopause altitude was 4 km below the cloud altitude. The cloud particles depolarized the lidar returns, thus must they have been aspherical and hence solid. Atmospheric temperatures near 230 K were approximately 40 K too high to support ice particles at stratospheric water vapour pressures of a few ppmv. The isentropic back trajectory on 400 K showed the air parcels to have stayed clear of active major rocket launch sites. The air parcels at 400 K had traveled from the Aleutians across Canada and the Atlantic Ocean arriving above central Europe and then turned northward to pass over above the lidar station. Parcels at levels at ±25 K from 400 K had come from the pole and joined the 400 K trajectory path above eastern Canada. Apparently the cloud existed in a filament of air with an origin different from those filaments both above and below. Possibly the 400 K level air parcels had carried soot particles from forest wild fires in northern Canada or volcanic ash from the eruption of the Korovin Volcano in the Aleutian Islands.Key words: Atmospheric composition and structure (aerosols and particles; biosphere-atmosphere interactions) · Meteorology and atmospheric dynamics (middle atmospheric dynamics)

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Stratospheric background aerosol and polar cloud observations by laser backscattersonde within the framework of the European project "Stratospheric Regular Sounding"

Annales Geophysicae ◽

10.1007/s00585-999-1352-2 ◽

1999 ◽

Vol 17 (10) ◽

pp. 1352-1360 ◽

Cited By ~ 6

Author(s):

A. Adriani ◽

F. Cairo ◽

L. Pulvirenti ◽

F. Cardillo ◽

M. Viterbini ◽

...

Keyword(s):

Lower Stratosphere ◽

Middle Atmosphere ◽

Polar Vortex ◽

Atmospheric Composition ◽

The Arctic ◽

Tropical Regions ◽

Convective Systems ◽

Composition And Structure ◽

Different Seasons ◽

Stratospheric Clouds

Abstract. The Stratospheric Regular Sounding project was planned to measure regularly the vertical profiles of several tracers like ozone, water vapor, NOx, ClOx and BrOx radicals, aerosol, pressure and temperature, at three latitudes, to discriminate between the transport and photochemical terms which control their distribution. As part of this project, the "Istituto di Fisica dell'Atmosfera" launched nine laser backscattersondes (LABS) on board stratospheric balloons to make observations of background aerosol and PSCs. LABS was launched with an optical particle counter operated by the University of Wyoming. Observations have been performed in the arctic, mid-latitudes and tropical regions in different seasons. Polar stratospheric clouds have been observed in areas inside and outside the polar vortex edge. A background aerosol was observed both in mid-latitudes and in arctic regions with a backscattering ratio of 1.2 at 692 nm. Very stratified aerosol layers, possibly transported into the lower stratosphere by deep convective systems, have been observed in the lower stratosphere between 20 and 29 km in the tropics in the Southern Hemisphere. Key words. Atmospheric composition and structure (aerosols and particles; middle atmosphere – composition and chemistry; instruments and techniques)

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