GLORIA

GEOMAR Library Ocean Research Information Access

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • AMS (American Meteorological Society)  (12)
  • Copernicus Publications (EGU)  (3)
  • Berlin, Heidelberg : Springer Berlin Heidelberg  (1)
  • 1
    Online Resource
    Online Resource
    An Approach to the Selberg Trace Formula via the Selberg Zeta-Function (1987)
    Berlin, Heidelberg : Springer Berlin Heidelberg
    Details Availability
    Keywords: Mathematics ; Number theory ; Number Theory ; Mathematics ; Selberg-Spurformel ; Selberg-Zetafunktion ; Selberg-Zetafunktion ; Selberg-Spurformel
    Description / Table of Contents: The Notes give a direct approach to the Selberg zeta-function for cofinite discrete subgroups of SL (2,#3) acting on the upper half-plane. The basic idea is to compute the trace of the iterated resolvent kernel of the hyperbolic Laplacian in order to arrive at the logarithmic derivative of the Selberg zeta-function. Previous knowledge of the Selberg trace formula is not assumed. The theory is developed for arbitrary real weights and for arbitrary multiplier systems permitting an approach to known results on classical automorphic forms without the Riemann-Roch theorem. The author's discussion of the Selberg trace formula stresses the analogy with the Riemann zeta-function. For example, the canonical factorization theorem involves an analogue of the Euler constant. Finally the general Selberg trace formula is deduced easily from the properties of the Selberg zeta-function: this is similar to the procedure in analytic number theory where the explicit formulae are deduced from the properties of the Riemann zeta-function. Apart from the basic spectral theory of the Laplacian for cofinite groups the book is self-contained and will be useful as a quick approach to the Selberg zeta-function and the Selberg trace formula
    Type of Medium: Online Resource
    Pages: Online-Ressource (IV, 188 p, online resource)
    ISBN: 9783540393313 , 9783540152088
    Series Statement: Lecture Notes in Mathematics 1253
    URL: https://doi.org/10.1007/BFb0077696
    URL: http://dx.doi.org/10.1007/BFb0077696
    URL: https://swbplus.bsz-bw.de/bsz01283212Xcov.jpg
    URL: https://zbmath.org/?q=an:0618.10029
    DOI: 10.1007/BFb0077696
    RVK:
    SI 850
    Language: English
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    GEOMAR CATALOGUE
    Link to Library Catalog
    get availability status
  • 2
    facet.materialart.
    Unknown
    Mean circulation and EKE distribution in the Labrador Sea Water level of the subpolar North Atlantic (2018)
    Copernicus Publications (EGU)
    In:  Ocean Science, 14 . pp. 1167-1183.
    Details
    Publication Date: 2021-03-19
    Description: A long-term mean flow field for the subpolar North Atlantic region with a horizontal resolution of approximately 25km is created by gridding Argo-derived velocity vectors using two different topography-following interpolation schemes. The 10-day float displacements in the typical drift depths of 1000 to 1500m represent the flow in the Labrador Sea Water density range. Both mapping algorithms separate the flow field into potential vorticity (PV) conserving, i.e., topography-following contribution and a deviating part, which we define as the eddy contribution. To verify the significance of the separation, we compare the mean flow and the eddy kinetic energy (EKE), derived from both mapping algorithms, with those obtained from multiyear mooring observations. The PV-conserving mean flow is characterized by stable boundary currents along all major topographic features including shelf breaks and basin-interior topographic ridges such as the Reykjanes Ridge or the Rockall Plateau. Mid-basin northward advection pathways from the northeastern Labrador Sea into the Irminger Sea and from the Mid-Atlantic Ridge region into the Iceland Basin are well-resolved. An eastward flow is present across the southern boundary of the subpolar gyre near 52°N, the latitude of the Charlie Gibbs Fracture Zone (CGFZ). The mid-depth EKE field resembles most of the satellite-derived surface EKE field. However, noticeable differences exist along the northward advection pathways in the Irminger Sea and the Iceland Basin, where the deep EKE exceeds the surface EKE field. Further, the ratio between mean flow and the square root of the EKE, the Peclet number, reveals distinct advection-dominated regions as well as basin-interior regimes in which mixing is prevailing.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.5194/os-14-1167-2018
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
    facet.materialart.
    Unknown
    Summer upwelling at the Boknis Eck time series station (1982 to 2012) - a combined glider and wind data analysis (2014)
    Copernicus Publications (EGU)
    In:  Biogeosciences (BG), 11 . pp. 3603-3617.
    Details
    Publication Date: 2019-05-23
    Description: Two consecutive summer upwelling events, each lasting for less than 24 h, were surveyed in high temporal and vertical resolution close to the Boknis Eck time-series station (BE) in the western Belt Sea (Baltic Sea) in summer 2010 with an autonomous glider. Driven only by moderate offshore winds both events resulted in more than 5 K cooling of surface waters, while only for the second event were significant irreversible changes in the vertical stratification observed. Generalizing the glider survey observations with hourly wind data from nearby meteorological stations, it is found that upwelling in the BE area occurs for wind directions between 190 to 260° and wind speed exceeding 4 m s−1. Based on these thresholds the wind-induced summer (June to September) upwelling conditions in the BE area for the period 1982 to 2012 are reconstructed. On average about 18 days of upwelling favourable wind conditions are found for the four summer months, with significant interannual variability ranging from 7.7 days (2006) to more than 28 days (1985). By aligning upwelling favourable wind conditions with the monthly BE surveys it is found that extreme anomalies in BE surveys follow extended periods of upwelling favourable winds.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.5194/bg-11-3603-2014
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
    facet.materialart.
    Unknown
    Surveying the upper Ocean with the Ocean Surveyor - a new Phased Array Doppler Current Profiler (2003)
    AMS (American Meteorological Society)
    In:  Journal of Atmospheric and Oceanic Technology, 20 (5). pp. 742-751.
    Details
    Publication Date: 2020-08-04
    Description: A new shipboard current profiler, a 75-kHz ocean surveyor, was operationally used during two research cruises in the tropical Atlantic and the subpolar North Atlantic, respectively. Here, a report is presented on the first experience with this instrument in two very different current regimes, in the Tropics with large vertical shears, and in the subpolar regime with mainly barotropic flow. The ocean surveyor continuously measured currents in the upper ocean from near the surface to about 500–700-m depth. The measurement range showed a dependence on the regional and temporal variations of scattering particles and on the intensity of swell and wind waves. Statistical comparisons are performed with on-station lowered acoustic Doppler current profiler (LADCP) profiles and underway measurements by classic shipboard acoustic Doppler current profiler (ADCP) measurements. Accuracy estimates for hourly averaged ocean surveyor currents result in errors of about 1 cm s–1 for on-station data and of 2–4 cm s–1 for underway measurements, depending on the regional abundance of scatterers and on the weather conditions encountered.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1175/1520-0426(2003)20〈742:STUOWT〉2.0.CO;2
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
    facet.materialart.
    Unknown
    Deep Velocity Profiling with Self-contained ADCPs (1993)
    AMS (American Meteorological Society)
    In:  Journal of Atmospheric and Oceanic Technology, 10 (5). pp. 764-773.
    Details
    Publication Date: 2020-08-04
    Description: Ocean deep velocity profiles were obtained by lowering a self-contained 153.6-kHz acoustic Doppler current profiler (ADCP) attached to a CTD-rosette sampler. The data were sampled during two Meteor cruises in the western tropical Atlantic. The ADCP depth was determined by integration of the vertical velocity measurements, and the maximum depth of the cast was in good agreement with the CTD depth. Vertical shears were calculated for individual ADCP velocity profiles of 140-300-m range to eliminate the unknown horizontal motion of the instrument package. Subsequent raw shear profiles were then averaged with respect to depth to obtain a mean shear profile and its statistics. Typically, the shear standard deviations were about 10(-3) s-1 when using up and down traces simultaneously. The shear profiles were then vertically integrated to get relative velocity profiles. Different methods were tested to transform the relative velocities into absolute velocity profiles, and the results were compared with Pegasus dropsonde measurements. The best results were obtained by integrating the raw velocities and relative velocities over the duration of the cast and correcting for the ship drift determined from the Global Positioning System. Below 1000-m depth a reduction of the measurement range was observed, which results either from a lack of scatterers or instrumental problems at higher pressures.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1175/1520-0426(1993)010〈0764:DVPWSC〉2.0.CO;2
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
    facet.materialart.
    Unknown
    Transports and pathways of the upperlayer circulation in the western tropical Atlantic (1998)
    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 28 (10). pp. 1904-1928.
    Details
    Publication Date: 2018-04-06
    Description: The mean warm water transfer toward the equator along the western boundary of the South Atlantic is investigated, based on a number of ship surveys carried out during 1990–96 with CTD water mass observations and current profiling by shipboard and lowered (with the CTD/rosette) acoustic Doppler current profiler and with Pegasus current profiler. The bulk of the northward warm water flow follows the coast in the North Brazil Undercurrent (NBUC) from latitudes south of 10°S, carrying 23 Sv (Sv ≡ 106 m3 s−1) above 1000 m. Out of this, 16 Sv are waters warmer than 7°C that form the source waters of the Florida Current. Zonal inflow from the east by the South Equatorial Current enters the western boundary system dominantly north of 5°S, adding transport northwest of Cape San Roque, and transforming the NBUC along its way toward the equator into a surface-intensified current, the North Brazil Current (NBC). From the combination of moored arrays and shipboard sections just north of the equator along 44°W, the mean NBC transport was determined at 35 Sv with a small seasonal cycle amplitude of only about 3 Sv. The reason for the much larger near-equatorial northward warm water boundary current than what would be required to carry the northward heat transport are recirculations by the zonal current system and the existence of the shallow South Atlantic tropical–subtropical cell (STC). The STC connects the subduction zones of the eastern subtropics of both hemispheres via equatorward boundary undercurrents with the Equatorial Undercurrent (EUC), and the return flow is through upwelling and poleward Ekman transport. The persistent existence of a set of eastward thermocline and intermediate countercurrents on both sides of the equator was confirmed that recurred throughout the observations and carry ventilated waters from the boundary regime into the tropical interior. A strong westward current underneath the EUC, the Equatorial Intermediate Current, returns low-oxygen water westward. Consistent evidence for the existence of a seasonal variation in the warm water flow south of the equator could not be established, whereas significant seasonal variability of the boundary regime occurs north of the equator: northwestward alongshore throughflow of about 10 Sv of waters with properties from the Southern Hemisphere was found along the Guiana boundary in boreal spring when the North Equatorial Countercurrent is absent or even flowing westward, whereas during June–January the upper NBC is known to connect with the eastward North Equatorial Countercurrent through a retroflection zone that seasonally migrates up and down the coast and spawns eddies. The equatorial zone thus acts as a buffer and transformation zone for cross-equatorial exchanges, but knowledge of the detailed pathways in the interior including the involved diapycnal exchanges is still a problem.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1175/1520-0485(1998)028〈1904:TAPOTU〉2.0.CO;2
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
    facet.materialart.
    Unknown
    Labrador Sea Water tracked by profiling floats - from the boundary current into the open North Atlantic (2002)
    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 32 . pp. 573-584.
    Details
    Publication Date: 2020-08-04
    Description: Fifteen profiling floats were injected into the deep boundary current off Labrador. They were ballasted to drift in the core depth of Labrador Sea Water (LSW) at 1500-m depth and were deployed in two groups during March and July/August 1997. Initially, for about three months, the floats were drifting within the boundary current, and the flow vectors were used to determine the mean horizontal structure of the Deep Labrador Current, which was found to be about 100 km wide with an average core speed of 18 cm s−1. North of Flemish Cap the boundary current encounters complicated topography around “Orphan Knoll,” and there the LSW outflow splits up into different routes. One obvious LSW path is eastward through the Charlie Gibbs Fracture Zone and another route is a narrow recirculation toward the central Labrador Sea. A surprising result was that none of the floats were able to follow the boundary current southward to the Grand Banks area and exit into the subtropics. Trajectories and temperature profiles of the eastward drifting floats indicate the importance of the North Atlantic Current for dispersing the floats, even at the level of LSW.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1175/1520-0485(2002)032〈0573:LSWTBP〉2.0.CO;2
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
    facet.materialart.
    Unknown
    Boundary circulation at the exit of the Labrador Sea (2004)
    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 34 . pp. 1548-1570.
    Details
    Publication Date: 2020-08-04
    Description: The deep circulation and related transports of the southern Labrador Sea are determined from direct current observations from ship surveys and a moored current-meter array. The measurements covered a time span from summer 1997 to 1999 and show a well-defined deep boundary current extending approximately out to the 3300-m depth contour and weak reverse currents farther offshore. The flow has a strong barotropic component, and significant baroclinic flow is only found in the shallow Labrador Current at the shelf break and associated with a deep core of Denmark Strait Overflow Water. The total deep-water transport below σΘ = 27.74 kg m−3 was 26 ± 5 Sv (Sv ≡ 106 m3 s−1) comprising Labrador Sea Water (LSW), Gibbs Fracture Zone Water (GFZW), and Denmark Strait Overflow Water (DSOW). Intraseasonal variability of the flow and transport was high, ranging from 15 to 35 Sv, and the annual means differed by 17%. A seasonal cycle is confined to the shallow Labrador Current; in its deeper part, where the mean flow is still strong, no obvious seasonality could be detected. The transport of the interior anticyclonic recirculation was estimated from lowered acoustic Doppler current profiler stations and geostrophy, yielding about 9 Sv. Thus, the net deep-water outflow from the Labrador Sea was about 17 Sv. The baroclinic transport of GFZW and DSOW referenced to the depth of the isopycnal σΘ = 27.80 kg m−3 is only about one-third of the total transport in these layers. Longer-term variations of the total transports are not represented well by the baroclinic contribution.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1175/1520-0485(2004)034〈1548:BCATEO〉2.0.CO;2
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
    facet.materialart.
    Unknown
    Circulation and deep water export at the western exit of the subpolar North Atlantic (2004)
    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 34 . pp. 817-843.
    Details
    Publication Date: 2020-08-04
    Description: The current system east of the Grand Banks was intensely observed by World Ocean Circulation Experiment (WOCE) array ACM-6 during 1993–95 with eight moorings, reaching about 500 km out from the shelf edge and covering the water column from about 400-m depth to the bottom. More recently, a reduced array by the Institut für Meerskunde (IfM) at Kiel, Germany, of four moorings was deployed during 1999–2001, focusing on the deep-water flow near the western continental slope. Both sets of moored time series, each about 22 months long, are combined here for a mean current boundary section, and both arrays are analyzed for the variability of currents and transports. A mean hydrographic section is derived from seven ship surveys and is used for geostrophic upper-layer extrapolation and isopycnal subdivision of the mean transports into deep-water classes. The offshore part of the combined section is dominated by the deep-reaching North Atlantic Current (NAC) with currents still at 10 cm s−1 near the bottom and a total northward transport of about 140 Sv (Sv ≡ 106 m3 s−1), with the details depending on the method of surface extrapolation used. The mean flow along the western boundary was southward with the section-mean North Atlantic Deep Water outflow determined to be 12 Sv below the σθ = 27.74 kg m−3 isopycnal. However, east of the deep western boundary current (DWBC), the deep NAC carries a transport of 51 Sv northward below σθ = 27.74 kg m−3, resulting in a large net northward flow in the western part of the basin. From watermass signatures it is concluded that the deep NAC is not a direct recirculation of DWBC water masses. Transport time series for the DWBC variability are derived for both arrays. The variance is concentrated in the period range from 2 weeks to 2 months, but there are also variations at interannual and longer periods, with much of the DWBC variability being related to fluctuations and meandering of the NAC. A significant annual cycle is not recognizable in the combined current and transport time series of both arrays. The moored array results are compared with other evidence on deep outflow and recirculation, including recent models of different types and complexity.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1175/1520-0485(2004)034〈0817:CADEAT〉2.0.CO;2
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
    facet.materialart.
    Unknown
    Dissolved organic matter at the fluvial–marine transition in the Laptev Sea using in situ data and ocean colour remote sensing (2019)
    Copernicus Publications (EGU)
    In:  Biogeosciences (BG), 16 (13). pp. 2693-2713.
    Details
    Publication Date: 2022-01-31
    Description: River water is the main source of dissolved organic carbon (DOC) in the Arctic Ocean. DOC plays an important role in the Arctic carbon cycle, and its export from land to sea is expected to increase as ongoing climate change accelerates permafrost thaw. However, transport pathways and transformation of DOC in the land-to-ocean transition are mostly unknown. We collected DOC and aCDOM(λ) samples from 11 expeditions to river, coastal and offshore waters and present a new DOC–aCDOM(λ) model for the fluvial–marine transition zone in the Laptev Sea. The aCDOM(λ) characteristics revealed that the dissolved organic matter (DOM) in samples of this dataset are primarily of terrigenous origin. Observed changes in aCDOM(443) and its spectral slopes indicate that DOM is modified by microbial and photo-degradation. Ocean colour remote sensing (OCRS) provides the absorption coefficient of coloured dissolved organic matter (aCDOM(λ)sat) at λ=440 or 443 nm, which can be used to estimate DOC concentration at high temporal and spatial resolution over large regions. We tested the statistical performance of five OCRS algorithms and evaluated the plausibility of the spatial distribution of derived aCDOM(λ)sat. The OLCI (Sentinel-3 Ocean and Land Colour Instrument) neural network swarm (ONNS) algorithm showed the best performance compared to in situ aCDOM(440) (r2=0.72). Additionally, we found ONNS-derived aCDOM(440), in contrast to other algorithms, to be partly independent of sediment concentration, making ONNS the most suitable aCDOM(λ)sat algorithm for the Laptev Sea region. The DOC–aCDOM(λ) model was applied to ONNS-derived aCDOM(440), and retrieved DOC concentration maps showed moderate agreement to in situ data (r2=0.53). The in situ and satellite-retrieved data were offset by up to several days, which may partly explain the weak correlation for this dynamic region. Satellite-derived surface water DOC concentration maps from Medium Resolution Imaging Spectrometer (MERIS) satellite data demonstrate rapid removal of DOC within short time periods in coastal waters of the Laptev Sea, which is likely caused by physical mixing and different types of degradation processes. Using samples from all occurring water types leads to a more robust DOC–aCDOM(λ) model for the retrievals of DOC in Arctic shelf and river waters.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.5194/bg-16-2693-2019
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...