Migration dynamics of Pacific herring (Clupea pallasii) and response to spring environmental variability in the southeastern Bering Sea     

Naoki Tojo  Gordon H. Kruse  Fritz C. Funk 《Deep Sea Research Part II: Topical Studies in Oceanography》2007,54(23-26):2832

In the southeastern Bering Sea, Pacific herring (Clupea pallasii) migrate from the Pribilof Islands region where they overwinter, to the Alaska coast where they spawn in spring. The migration sustains a nearshore commercial fishery that targets roe-bearing females just prior to spawning. Herring also are taken as bycatch in groundfish trawl fisheries, where time and area closures in these fisheries are triggered by herring bycatch caps. Using herring bycatch data collected since the 1970s by National Marine Fisheries Service (NMFS) observers aboard groundfish fishing vessels, a retrospective analysis was conducted to describe the seasonal migration pattern of Pacific herring in the southeastern Bering Sea and to study its spatial and temporal variability. Observed changes in herring catch per unit of effort were compared with variability in climate and oceanographic conditions. The seasonal migration is complex, but annual shifts in migration routes and a possible northward shift of the overwintering grounds was identified. Pre-spawning herring aggregated in different areas depending on whether spawning occurred early or late in spring. The thermal structure of the ocean around the ice edge appears to influence herring migration timing and route as well as spawning date. Thus, on the basis of recent changes in sea-ice extent and duration, we suggest that the herring bycatch savings area that was developed from data collected in the 1980s should be revised to reflect prevailing conditions.  相似文献   

Ein erdmagnetisches Profil über die Daciabank im Atlantischen Ozean     

Fritz Errulat 《Ocean Dynamics》1948,1(1):30-32

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Synchronous climatic change inferred from diatom records in four western Montana lakes in the U.S. Rocky Mountains     

Brandi Bracht-Flyr  Sherilyn C. Fritz 《Quaternary Research》2012,77(3):456-467

Late-Holocene environmental and climatic conditions were reconstructed from diatom assemblages in sediment cores from four western Montana lakes: Crevice Lake, Foy Lake, Morrison Lake, and Reservoir Lake. The lakes show synchroneity in timing of shifts in diatom community structure, but the nature of these changes differs among the lakes. Two of the sites provide highly resolved records of hydrologic balance, while the other two stratigraphic sequences primarily record temperature impact on lake thermal structure. All four lakes show significant change in five discrete intervals: 2200–2100, 1700–1600, 1350–1200, 800–600, and 250 cal yr BP. The similarities in the timing of change suggest overlying regional climatic influences on lake dynamics. The 800–600 cal yr BP shift is evident in other paleorecords throughout the Great Plains and western US, associated with the transition from the Medieval Climate Anomaly to the Little Ice Age. Large-scale climatic mechanisms that influence these lake environments may result from atmospheric circulation patterns that are driven by interactions between Pacific and Atlantic sea-surface temperatures, which are then locally modified by topography.  相似文献   

Three generations of monazite in Austroalpine basement rocks to the south of the Tauern Window: evidence for Variscan, Permian and Eo-Alpine metamorphic events     

Erwin Krenn  Bernhard Schulz  Fritz Finger 《Swiss Journal of Geoscience》2012,105(3):343-360

Three monazite generations were observed in garnet-bearing micaschists from the Schobergruppe in the basement to the south of the Tauern Window, Eastern Alps. Low-Y monazite of Variscan age (321?±?14?Ma) and high-Y monazite of Permian age (261?±?18?Ma) are abundant in the mica-rich rock matrix and in the outer domains of large garnet crystals. Pre-Alpine monazite commonly occurs as polyphase grains with low-Y Variscan cores and high-Y Permian rims. Monazite of Eo-Alpine age (112?±?22?Ma) is rarer and was observed as small, partly Y-enriched grains (3?wt. %?Y₂O₃) in the rock matrix and within garnet. Based on monazite-xenotime thermometry, Y?+?HREE values in monazite indicate minimum crystallization conditions of 500?°C during the Variscan and 650?°C for the Permian and Alpine events, respectively. Garnet zoning and thermobarometric calculations with THERMOCALC 3.21 record an amphibolite facies, high-pressure stage of ~600?°C/13?C16?kbar, followed by a thermal maximum at 650?C700?°C and 6?C9?kbar. The Eo-Alpine age for these two events is supported by inclusions of Cretaceous monazite in the garnet domains used for thermobarometric constraints and through the high growth temperatures of Eo-Alpine monazite, which is consistent with that of the thermal maximum (~700?°C). The age and growth conditions of a few Mn-rich garnet cores, sporadically present within Eo-Alpine garnet, are unclear because inclusions of monazite, plagioclase and biotite necessary for thermobarometric- and age constraints are absent. However, based on monazite thermometry, Permian and Variscan metamorphic conditions were high enough for the growth of pre-Alpine garnet. The formation of Variscan garnet and its later resorption, plus Y-release, would also explain the high Y in Permian monazite, which cannot originate from preexisting Variscan monazite only. Monazite of Variscan, Permian and/or Eo-Alpine ages were also observed in other garnet-bearing micaschists from the Schobergruppe. This suggests that the basement of the Schobergruppe was overprinted by three discrete metamorphic events at conditions of at least lower amphibolite facies. While the Variscan event affected all parts of this basement, the younger events are more pronounced in its structurally lower units.  相似文献   

Geochemical tracing and hydrogeochemical modelling of water–rock interactions during salinization of alluvial groundwater (Upper Rhine Valley,France)     

Y. Lucas  A.D. Schmitt  F. Chabaux  A. Clément  B. Fritz  Ph. Elsass  S. Durand 《Applied Geochemistry》2010

In the southern Upper Rhine Valley, groundwater has undergone intensive saline pollution caused by the infiltration of mining brines, a consequence of potash extraction carried out during the 20th century. Major and trace elements along with Sr and U isotopic ratios show that groundwater geochemical characteristics along the saline plumes cannot reflect conservative mixing between saline waters resulting from the dissolution of waste heaps and one or more unpolluted end-members. The results imply the occurrence of interactions between host rocks and polluted waters, and they suggest that cationic exchange mechanisms are the primary controlling process. A coupled hydrogeochemical model has been developed with the numerical code KIRMAT, which demonstrates that cationic exchange between alkalis from polluted waters and alkaline-earth elements from montmorillonite present in the host rock of the aquifer is the primary process controlling the geochemical evolution of the groundwater. The model requires only a small amount of montmorillonite (between 0.75% and 2.25%), which is in agreement with the observed mineralogical composition of the aquifer. The model also proves that a small contribution of calcite precipitation/dissolution takes places whereas other secondary mineral precipitation or host rock mineral dissolution do not play a significant role in the geochemical signature of the studied groundwater samples. Application of the model demonstrates that it is necessary to consider the pollution history to explain the important Cl, Na and Ca concentration modifications in groundwater samples taken over 2 km downstream of waste heaps. Additionally, the model shows that the rapidity of the cationic exchange reactions insures a reversibility of the cation fixation on clays in the aquifer.  相似文献   

On the way to the exploitation of deep geothermal resources in naturally fractured environments     

Bertrand Fritz  André Gérard 《Comptes Rendus Geoscience》2010,342(7-8):493-501

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Jovian plasma sheet morphology: particle and field observations by the Galileo spacecraft     

L.S. Waldrop  T.A. Fritz  K. Khurana  A. Lagg 《Planetary and Space Science》2005,53(6):681-692

We present results from an investigation of the plasma sheet encounter signatures observed in the Jovian magnetosphere by the Energetic Particles Detector (EPD) and Magnetometer (MAG) onboard the Galileo spacecraft. Maxima in ion flux were used to identify over 500 spacecraft encounters with the plasma sheet between radial distances from Jupiter from 20 to 140R_J during the first 25 orbits (4 years of data). Typical signatures of plasma sheet encounters show a characteristic periodicity of either 5 or 10 hours that is attributed to an oscillation in the relative distance between the spacecraft and the plasma sheet that arises from the combination of planetary rotation and offset magnetic and rotational axes. However, the energetic particle and field data also display much variability, including instances of intense fluxes having little to no periodicity that persist for several Jovian rotation periods. Abrupt changes in the mean distance between the plasma sheet and the spacecraft are suggested to account for some of the transitions between typical flux periodicities associated with plasma sheet encounters. Additional changes in the plasma sheet thickness and/or amplitude of the plasma sheet displacement from the location of the spacecraft are required to explain the cases where the periodicity breaks down but fluxes remain high. These changes in plasma sheet characteristics do not display an obvious periodicity; however, the observations suggest that dawn/dusk asymmetries in both the structure of the plasma sheet and the frequency of anomalous plasma sheet encounters are present. Evidence of a thin, well-ordered plasma sheet is found out to 110R_J in the dawn and midnight local time sectors, while the dusk magnetosphere is characterized by a thicker, more disordered plasma sheet and has a potentially more pronounced response to an impulsive trigger. Temporal variations associated with changing solar wind conditions are suggested to account for the anomalous plasma sheet encounters there.  相似文献   

A regional-scale climate reconstruction of the last 4000 years from lakes in the Nebraska Sand Hills,USA     

J. Schmieder  S.C. Fritz  J.B. Swinehart  A.L.C. Shinneman  A.P. Wolfe  G. Miller  N. Daniels  K.C. Jacobs  E.C. Grimm 《Quaternary Science Reviews》2011,30(13-14):1797-1812

High-resolution paleohydrological reconstructions were carried out in five shallow lakes in the Nebraska Sand Hills across an east–west transect in order to 1) determine whether long-term droughts of the past 4000 years were spatially and temporally coherent across the region, 2) distinguish local variation in climate or hydrology from regional patterns of change, and 3) compare the paleolimnological results with the existing dune-inferred drought records. Diatom-inferred lake-level was reconstructed for all sites and compared with other regional records. Alterations between high and low lake-levels were frequent during the past 4000 years, which suggests that shifts between dry and wet periods were prevalent across the Sand Hills. Extended multi-decadal to centennial-scale droughts were more common prior to 2000 years BP, while the last two millennia were hydrologically more variable and climate conditions alternated on shorter timescales. Despite some discrepancies among the five records, the paleohydrological reconstructions refine the Holocene drought history of the Nebraska Sand Hills, particularly between ～2200 and 4000 cal a BP. Many of the observed drought events are contemporaneous with severe droughts documented at sites in the northern Great Plains and Rocky Mountains, lending support for the severity and regional significance of these events in western North America.  相似文献   

Zeitschriften- und Bücherschau     

Fritz Goebel  Wcks 《International Journal of Earth Sciences》1924,14(3):285-293

Ohne Zusammenfassung  相似文献   

The Evolutionary Status of Early-type Galaxies in Abell 2390     

A. Fritz  B.L. Ziegler  R.G. Bower  I. Smail  R.L. Davies 《Astrophysics and Space Science》2003,285(1):61-66

We explore the evolution of the early-type galaxy population in the rich cluster Abell 2390 at z=0.23. For this purpose, we have obtained spectroscopic data of 51 elliptical and lenticular galaxies with MOSCA at the 3.5 m telescope on Calar Alto Observatory. As our investigation spans both a broad range in luminosity (–22.3≤M_B≤–:19.3)and a wide field of view (10′×10′), the environmental dependence of different formation scenarios can be analysed in detail as a function of radius from the cluster center. In this paper, we present first results on the Faber-Jackson relation and, for a subsample of 14 galaxies with morphological and structural parameters from HST, we also investigate the evolution of the Kormendy relation and the Fundamental Plane. We find a mild luminosity evolution of the early-type galaxies in Abell 2390: our objects are on average brighter by m _B∼0.4 mag. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献