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  • Articles  (137)
  • Geosciences  (137)
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  • Articles  (137)
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  • 1
    Electronic Resource
    Electronic Resource
    Synoptic variations in the chemical composition of atmospheric precipitation (1955)
    Springer
    Pure and applied geophysics 31 (1955), S. 127-128 
    Details
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Description / Table of Contents: Zusammenfassung Ein Studium der chemischen Zusammensetzung von Proben des monatlichen Niederschlages einer Anzahl von Beobachtungsstationen in Schweden deckt die Existenz von deutlichen Schwankungen im relativen Verhältnis von Chlor und Natrium auf, welche vom allgemeinen Charakter der vorherrschenden Zirkulation abhängen. In maritimen westlichen Strömungen nimmt das Gewichtsverhältnis von Chlor zu Natrium gegen Osten zu auf Werte, welche weit unterhalb des charakteristischen Betrages für Meerwasser liegen, ab. Im Niederschlag, welcher aus arktischen oder polar-kontinentalen Luftmassen stammt, fehlt die Chlor-Komponente beinahe vollständig. Der höchste Betrag von Chlor relativ zu Natrium wurde im Niederschlag aus warmen und den meisten Luftmassen, welche Schweden vom Süden und Südosten erreichen, gefunden. Deutliche Schwankungen wurden auch in den Jahresmitteln des Verhältnisses Chlor zu Natrium beobachtet, welche von der Vorherrschaft der maritimen oder kontinentalen Luftströmungen abhängen. Eine schematische Karte der «mittleren» Chlor-Konzentration im Europäischen Niederschlag, welche mit Hilfe von verschiedenen älteren Daten entworfen wurde, unterstützt die Resultate der Analyse der Monatswerte. Die Trennung der chemischen Komponenten, welche durch diese Untersuchung angedeutet wird, scheint von beträchtlichem Interesse für die Erdchemie zu sein, da auf diese Weise verschiedene maritime Salze in weit auseinander liegenden Teilen der Kontinente abgelagert würden. Die ausführliche Arbeit wird in der Zeitschrift «Tellus», VII (1955), 1 veröffentlicht werden.
    Notes: Summary A study of the chemical composition of monthly precipitation samples from a number of stations in Sweden brings out the existence of significant variations in the relative proportions of chlorides and sodium depending upon the general character of the prevailing circulation. In maritime westerly flows the weight ratio of chloride to sodium decreases eastward to values which lie far below that value characteristic of sea water. In precipitation falling from arctic or polar continental air masses the chloride component is almost completely absent. The highest amounts of chlorides relative to sodium are observed in precipitation from warm and most air masses reaching Sweden from the south or southeast. Significant variations are observed also in the yearly means of the chloride to sodium ratio depending upon the dominance of maritime or continental air currents. A sketch map of the «average» chloride concentration in European precipitation prepared from miscellaneous older data lends support to the results of the analysis of the monthly data. The separation of the chemical components indicated by this study would seem to be of considerable geochemical interest since it would permit different maritime salts to be deposited in widely separated parts of the continents. The full paper will be published in «Tellus», VII (1955), 1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01999595
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A new conservation-theorem of hydrodynamics (1949)
    Springer
    Pure and applied geophysics 14 (1949), S. 189-193 
    Details
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Description / Table of Contents: Zusammenfassung Der hier abgeleitete Erhaltungs-Satz sagt Folgendes aus: Wenn $$\vec v$$ die absolute Geschwindigkeit, $$\vec \xi = curl\vec v$$ den absoluten Wirbel, σ=σ(p) das spezifische Volumen einer barotropen Flüssigkeit und ΔW den Gradienten der Wirkungsfunktion bedeuten, so gilt: $$\frac{D}{{Dt}}\left\{ {\sigma {\text{ }}\vec \xi (\vec v - \nabla W)} \right\} = 0,$$ wobei $$\frac{D}{{Dt}}$$ die individuelle Zeitableitung der Hydrodynamik darstellt.
    Notes: Summary The conservation-theorem derived here can be expressed thus: Let $$\vec v$$ be the absolute velocity and $$\vec \xi = curl\vec v$$ the absolute vorticity, further σ=σ(p) the specific volume of a barotropic fluid and ΔW the gradient of the actionW (=Hamilton's principal-function), then $$\frac{D}{{Dt}}\left\{ {\sigma {\text{ }}\vec \xi (\vec v - \nabla W)} \right\} = 0,$$ where $$\frac{D}{{Dt}}$$ denotes differentiation following the motion of the fluid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01981973
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  • 3
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    On the long-term stability of the Lofoten Basin Eddy (2016)
    Wiley
    Details
    Publication Date: 2016-06-03
    Description: In recent years several studies have identified an area of intense anticyclonic activity about 500 km straight west of the Lofoten Islands at 70°N in the northern Norwegian Sea. Now recognized as the coherent Lofoten Basin Eddy (LBE), it is maintained by a supply of anticyclonic eddies that break away from the Norwegian Atlantic Current. Here we show from ship-based surveys of its velocity field that it is quite stable with a central core in solid body rotation ∼1000 m deep, ∼8 km radius and a relative vorticity close to its theoretical limit – f . The surveys also show the LBE typically has a 〉 60 km radius with maximum swirl velocities at 17-20 km radius. From the velocity field we estimate the dynamic height amplitude at the surface to be about ∼0.21 ± 0.03 dyn. m. Second, altimetry from the last 20 years shows the extremum in sea surface height relative to the surrounding waters to be about the same, 0.2 dyn. m. Third, a float trapped in the LBE for many months reveals a clear cyclonic wandering of the eddy over the deepest parts of the basin. Lastly, three hydrographic sections from the 1960s show the dynamic height signal to be virtually the same then as it is now. From these observations we conclude that the LBE is a permanent feature of the Nordic Seas and plays a central role in maintaining the pool of warm water in the western Lofoten Basin. This article is protected by copyright. All rights reserved.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    Directly measured currents and estimated transport pathways of Atlantic Water between 59.5°N and the Iceland–Faroes–Scotland Ridge (2015)
    Co-Action Publishing
    In: Tellus A
    Details
    Publication Date: 2015-11-25
    Description: Using vessel-mounted acoustic Doppler current profiler data from four different routes between Scotland, Iceland and Greenland, we map out the mean flow of water in the top 400 m of the northeastern North Atlantic. The poleward transport east of the Reykjanes Ridge (RR) decreases from ~8.5 to 10 Sv (1 Sverdrup=10 6 m 3 s −1 ) at 59.5°N to 61°N to 6 Sv crossing the Iceland–Faroes–Scotland Ridge. The two longest ~1200 km transport integrals have 1.4–0.94 Sv uncertainty, respectively. The overall decrease in transport can in large measure be accounted for by a ~1.5 Sv flow across the RR into the Irminger Sea north of 59.5°N and by a ~0.5 Sv overflow of dense water along the Iceland–Faroes Ridge. A remaining 0.5 Sv flux divergence is at the edge of detectability, but if real could be accounted for through wintertime convection to 〉400 m and densification of upper ocean water. The topography of the Iceland Basin and the banks west of Scotland play a fundamental role in controlling flow pathways towards and past Iceland, the Faroes and Scotland. Most water flows north unimpeded through the Iceland Basin, some in the centre of the basin along the Maury Channel, and some along Hatton Bank, turning east along the northern slopes of George Bligh Bank, Lousy Bank and Bill Bailey’s Bank, whereupon the flow splits with ~3 Sv turning northwest towards the Iceland–Faroes Ridge and the remainder continuing east towards and north of the Wyville-Thomson Ridge (WTR) to the Scotland slope thereby increasing the Slope Current transport from ~1.5 Sv south of the WTR to 3.5 Sv in the Faroes–Shetland Channel. Keywords: ADCP, current measurements, northeast Atlantic transport patterns, repeat sampling from vessels in regular traffic, Faroes–Shetland Channel, Iceland–Faroes Ridge (Published: 24 November 2015) Citation: Tellus A 2015, 67, 28067, http://dx.doi.org/10.3402/tellusa.v67.28067
    Print ISSN: 0280-6495
    Electronic ISSN: 1600-0870
    Topics: Geography , Geosciences , Physics
    Published by Co-Action Publishing on behalf of The International Meteorological Institute in Stockholm.
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  • 5
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    On the spatial structure and temporal variability of poleward transport between Scotland and Greenland (2014)
    Wiley
    Details
    Publication Date: 2014-01-17
    Description: The flow north of warm subtropical water though the northeastern Atlantic is known to have many pathways that vary over time. Here we use a combination of upper ocean current measurements between Greenland and Scotland near 60°N and satellite altimetry to examine the space-time variability of poleward transport. The high-resolution scans of currents in the top 400 m show that the Reykjanes Ridge serves as a very effective separator of flow towards the Nordic and Labrador Seas, respectively. Whereas the Labrador Sea branch exhibits two mean flows to the north on the western slope of the Reykjanes Ridge, the eastern branch flows north in roughly equal amounts over the deep Maury channel and east of Hatton Bank including the Slope Current. There is also a well-defined southward flow along the eastern slope of the Reykjanes Ridge. The satellite altimetric sea surface height (SSH) data show good overall agreement with geostrophically determined sea level difference from the repeat ADCP sections (1999-2002), but are unable to resolve the fine structure of the topographically defined mean circulation. The altimetric data show that variations in poleward flow west and east of the Reykjanes Ridge are strongly anticorrelated. They further reveal that the two eastern sub-branches also exhibit anticorrelated variability, but offset in time with respect to the Labrador Sea branch. Remarkably, all these variations cancel out for the entire Greenland-Scotland section leaving a gradual decrease in sea level difference of about 0.06 m over the 1993 to the end of 2010 observation period.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 6
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    A tale of two eddies: Diagnosing coherent eddies through acoustic remote sensing (2011)
    Wiley
    Details
    Publication Date: 2011-12-14
    Description: A 38 kHz vessel-mounted acoustic Doppler current profiler is used to explore in detail the dynamics of an anticyclonic and a cyclonic eddy during two transits of the cruise vessel Explorer of the Seas from the Caribbean to New Jersey in July 2007. The radial scale of the two eddies is similar, but whereas the cyclone is strongly surface intensified, the anticyclone has its maximum expression with near–solid body rotation between 200 and 800 m depth. The anticyclone has a minimum in relative vorticity very close to −f at 800 m depth and the cyclone has a maximum of about +1.6 f close to the surface where f is the local Coriolis parameter. By integrating the momentum equation the geopotential anomaly field and hence the potential energy of the eddies can be determined quite accurately, which means that the kinetic and potential energy of the eddies can be determined purely through acoustic remote sensing. Given a density profile just outside the eddy one can integrate the gradient wind equation to obtain an estimate of the density and hence potential vorticity fields through the two eddies. The acoustic backscatter patterns in the eddies are quite distinct from the surrounding waters. The backscatter intensity of the main scattering layer at ∼600 m depth decreases by ∼10 dB in the core of both eddies. In the cyclonic eddy three identifiable scattering layers in the main thermocline show a strong tendency for the scattering layer to track the shoaling density structure toward the center of the eddy.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
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    Direct velocity observations of volume flux between Iceland and the Shetland Islands (2014)
    Wiley
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    Publication Date: 2014-08-27
    Description: Atlantic Waters flowing northward into the Nordic Seas are important for their role as an early indicator of changes to deepwater formation. As such this requires a fundamental understanding of the pathways and volume fluxes through the primary passageways from the Atlantic into the Nordic Seas. A mean annual volume transport of 6.1±0.3 Sv was observed flowing in above the σ t =27.8 isopycnal (a proxy for the lower limit of Atlantic Water depth), through the Faroe Shetland Channel (FSC) and over the Iceland Faroes Ridge (IFR) from March 2008 through June 2012, using repeat velocity sections obtained from a vessel mounted Acoustic Doppler Current Profiler (ADCP). A new vessel route has expanded the spatial coverage of FSC observations and reveals a difference in average inflow transport, which most likely results from an interannual variation in the total transport through the FSC, which in turn is tied to a weakening of the southerly flow over the western slope of the channel. This interannual variability has increased the mean transport through the FSC from 0.9 Sv observed over the first two years of this program by Rossby and Flagg [2012] to a 4.5 year mean of 1.7±0.2 Sv, which emphasizes the importance of knowing the flow along the Faroese shelf. Interannual fluctuations in transport observed over the IFR are related to the width of the inflow over the Faroese half of the ridge.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
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    On the structure of the lofoten basin eddy (2013)
    Wiley
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    Publication Date: 2013-07-13
    Description: A small anticyclonic eddy of extraordinary intensity sits in the center of the Lofoten Basin near 69°40'N, 3°E. This paper gives a first detailed description of its kinematics and lowest order dynamic balances. Using a 75 kHz vessel-mounted acoustic Doppler current profiler, hydrography, and six RAFOS floats to probe the eddy, we document a solid body core with 7-8 km radius and relative vorticity very close to –f, where f is the local Coriolis parameter. Maximum orbital velocities close to 0.8 ms -1 were observed at 18 km radius. One float, trapped in the core of the eddy for 9 months, indicated undiminished strength throughout that period, possibly even intensifying in winter. Hydrography revealed adiabatic conditions from the bottom of a shallow seasonal thermocline to 1000 m depth in early July 2010. Thermal convection in winter maintains an already deep pycnostad, and may also play a key role in intensifying the eddy, quite possibly through penetrative convection that deepens and sharpens the underlying pycnocline. Heat lost to the atmosphere has to be replenished from warm anticyclonic eddies shed off the eastern branch of the Norwegian Atlantic Current, but the mechanism(s) by which it is added to the eddy remains to be studied. Examination of historical data sets suggests the eddy is a permanent feature of the Lofoten Basin. Two hydrocasts from the 1960s also show a similar adiabatic mixed layer albeit 1°C cooler than in 2010, perhaps reflecting the generally cold winter conditions that prevailed then.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 9
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    Direct measurement of volume flux in the Faroe-Shetland Channel and over the Iceland-Faroe Ridge (2012)
    Wiley
    Details
    Publication Date: 2012-04-04
    Description: Determining the exchange of water across the Iceland-Faroe-Scotland ridge is of fundamental interest because it measures the rate of transformation of North Atlantic water into dense water and thus the strength of the meridional overturning circulation (MOC). Here we study this exchange by monitoring all water flowing through the area east of Iceland to near the bottom or ∼600 m depth using a 75 kHz acoustic Doppler current profiler (ADCP) mounted on the high-seas ferry M/F Norröna. Starting in March 2008, currents have been measured in the Faroe-Shetland Channel (FSC) and along the Iceland-Faroe Ridge (IFR) on the ferry's weekly round-trips between Iceland and Denmark. The detided average transports (to the north) across the two sections are 4.1 ± 0.1 Sv (106 m2s−1) through the FSC and 4.4 ± 0.25 Sv across the IFR (this excludes ∼1.6 Sv circulating around the Faroes). The Norröna program is ongoing.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 10
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    On the long-term stability of Gulf Stream transport based on 20 years of direct measurements (2013)
    Wiley
    Details
    Publication Date: 2013-12-15
    Description: [1]  In contrast to recent claims of a Gulf Stream slow-down, two decades of directly measured velocity across the current show no evidence of a decrease. Using a well-constrained definition of Gulf Stream width, the linear least square fit yields a mean surface-layer transport of 1.35x10 5 m 2 s -1 with a 0.13% negative trend per year. Assuming geostrophy this corresponds to a mean cross-stream sea level difference of 1.17 m, with sea level decreasing 0.03 m over the 20-year period. This is not significant at the 95% confidence level, and it is a factor of 2-4 less than that alleged from accelerated sea-level rise along the U.S. coast north of Cape Hatteras. Part of the disparity can be traced to the spatial complexity of altimetric sea level trends over the same period.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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