Reproductive behavioral interactions between wild and captively reared coho salmon (Oncorhynchus kisutch)     

Berejikian  B. A.; Tezak  E. P.; Schroder  S. L.; Knudsen  C. M.; Hard  J. J. 《ICES Journal of Marine Science》1997,54(6):1040-1050

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The DNSC08GRA global marine gravity field from double retracked satellite altimetry   总被引：15，自引：9，他引：6  

Ole Baltazar Andersen  Per Knudsen  Philippa A. M. Berry 《Journal of Geodesy》2010,84(3):191-199

Satellite radar altimetry has been monitoring the earth’s oceans from space for several decades. However, only the GEOSAT and ERS-1 geodetic mission data recorded more than a decade ago provide altimetry with adequate spatial coverage to derive a high-resolution marine gravity field. The original geodetic mission data suffer from degradation in quality and coverage close to the coast and in Polar Regions as well as the occasionally wrongly retracking of these, even in the open ocean. In order to improve the quality of these geodetic mission data and to derive a new improved global marine gravity field called DNSC08GRA, a new double retracking technique for analyzing the waveform data has been developed. Multiple retracking allows the system to retrack more data to increase the spatial coverage of the data. Subsequently, a second retracking run is used to enhance the SSH determination by using information from the first fitting to inform the second set of retrackers about smoothly varying sea state parameters. The development of the new global marine gravity field DNSC08GRA is described in this paper. Besides application of new retracking techniques the radar altimetry has been processed using EGM2008 as reference and augmented with ArcGP gravity data and laser altimetry from ICESat to close the Polar gap. DNSC08GRA is seen to perform significantly better than previous global marine gravity field like KMS02. The improvement in accuracy is better than 20% in general, but in coastal regions, the improvement is in many places of the order of 40–50% compared to older global marine gravity field KMS02.  相似文献   

An event stratigraphy for the Last Termination in the North Atlantic region based on the Greenland ice-core record: a proposal by the INTIMATE group     

Svante Bjrck  Michael J. C. Walker  Les C. Cwynar  Sigfus Johnsen  Karen-Luise Knudsen  J. John Lowe  Barbara Wohlfarth 《第四纪科学杂志》1998,13(4):283-292

It is suggested that the GRIP Greenland ice-core should constitute the stratotype for the Last Termination. Based on the oxygen isotope signal in that core, a new event stratigraphy spanning the time interval from ca. 22.0 to 11.5 k GRIP yr BP (ca. 19.0–10.0 k ¹⁴C yr BP) is proposed for the North Atlantic region. This covers the period from the Last Glacial Maximum, through Termination 1 of the deep-ocean record, to the Pleistocene–Holocene boundary, and encompasses the Last Glacial Late-glacial of the traditional northwest European stratigraphy. The isotopic record for this period is divided into two stadial episodes, Greenland Stadials 1 (GS-1) and 2 (GS-2), and two interstadial events, Greenland Interstadials 1 (GI-1) and2 (GI-2). In addition, GI-1 and GS-2 are further subdivided into shorter episodes. The event stratigraphy is equally applicable to ice-core, marine and terrestrial records and is considered to be a more appropriate classificatory scheme than the terrestrially based radiocarbon-dated chronostratigraphy that has been used hitherto. © 1998 John Wiley & Sons, Ltd.  相似文献   

A giant (5.3 × 10 m) middle Miocene (c. 15 Ma) sediment mound (M1) above the Siri Canyon, Norwegian–Danish Basin: Origin and significance     

Katrine Juul Andresen  Ole Rn Clausen  Mads Huuse 《Marine and Petroleum Geology》2009,26(8):1640-1655

A large-scale enigmatic mound structure (M1) has been discovered in middle Miocene strata of the Norwegian–Danish Basin, c. 10 km east and updip of the Central Graben. It is located about 1 km beneath the seabed and clearly resolved by a 3D seismic data set focused on the deeper, remobilised, sand-filled Siri Canyon. M1 comprises two culminations, up to 80 m high and up to 1400 m long, constituting a sediment volume of some 5.3 × 10⁷ m³. It is characterized by a hard reflection at the top, a soft reflection at the base, differential compaction relative to the surrounding sediments, and 10 ms TWT velocity pull up of underlying reflections, indicating a relatively fast mound fill, attributed to the presence of sand within the mound. Internal seismic reflections are arranged in an asymmetric concentric pattern, suggesting a progressive aggradation to the NW, downstream to a mid-Miocene contour current system. Numerous elongated pockmarks occur in the upper Miocene succession close to the mound and indicate that the study area was influenced by gas expulsion in the mid- and late Miocene.The reflection configuration, velocity, dimensions, regional setting, and isolated location can best be explained by interpreting the mound as a giant sand volcano extruded >1 km upward from the Siri Canyon during the middle Miocene (c. 15 Ma). The likely causes of this remarkable structure include gas charge and lateral pressure transfer from the Central Graben along the Siri Canyon reservoir. While this is the first such structure described from this part of the North Sea, similar-aged sand extrudites have recently been inferred from seismic observations in the North Viking Graben, thus suggesting that the mid-Miocene was a time of widespread and intense sediment remobilization and fluid expulsion in the North Sea.  相似文献   

Generalizing Poisson Regression: Including Apriori Information Using the Method of Offsets*     

Daniel C. Knudsen 《The Professional geographer》1992,44(2):202-208

In a recent note in The Professional Geographer, Lovett and Flowerdew (1989) introduce the analysis of count data using Poisson regression. Concern here rests with generalizing their discussion to show how a priori information may be included into models that incorporate dependent variables enumerated as counts. These models can be calibrated using the OFFSET command in GLIM. The paper concludes with a brief discussion of the applicability of the method of offsets to other problems in spatial analysis.  相似文献   

Collinear and cross-over adjustment of Geosat ERM and Seasat altimeter data in the Mediterranean Sea   总被引：1，自引：0，他引：1  

P. Knudsen  M. Brovelli 《Surveys in Geophysics》1993,14(4-5):449-459

The computation of mean sea surface heights from a set of collinear Geosat ERM altimeter data tracks was carried out in a collinear adjustment, where 1 cy/rev cosine and sine coefficients for each track are estimated, so the differences between the collinear tracks are minimized. Then bias/tilt cross-over adjustments of stacked Geosat and Seasat altimetry were carried out. The problems with the free surface in the cross-over adjusted altimetric surface were treated using the absolute sea surface heights relative to the geoid model OSU89B. In a combined adjustment of the two altimeter data sets using cross-over and height informations simultaneously a RMS of the cross-overs of 0.080 m and a RMS of the sea surface heights relative to OSU89B of 0.611 m were obtained.  相似文献   

Statistical EOF analysis of spatiotemporal glacier mass-balance variability: a case study of Mittivakkat Gletscher,SE Greenland     

Sebastian H. Mernild  Andrew P. Beckerman  Niels Tvis Knudsen  Bent Hasholt  Jacob C. Yde 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2018,118(1):1-16

An Empirical Orthogonal Function (EOF) variance analysis was performed to map in detail the spatiotemporal variability in individual stake mass-balances (ba) on Mittivakkat Gletscher (MG) – in a region where at present five out of ~20.000 glaciers have mass-balance observations. The EOF analysis suggested that observed ba was summarized by two modes: EOF1 and EOF2 represented 80% (significant) and 6% (insignificant) of the explained variance, respectively. EOF1 captured a decline in ba that was uniformly distributed in space at all stakes. The decline was correlated with albedo observations and air temperature observations from nearby stations. EOF2, however, described variations in ba that were heterogeneously distributed among stakes and associated with local slope and aspect. Low elevation stakes (~<400 m a.s.l.) showed relatively negative (out of phase) correlation and higher elevated stakes relatively positive (in phase) eigenvector correlation values with EOF2. Such relatively negative and positive eigenvector correlation values were present where the constituted of exposed glacier ice or snow cover, respectively. The results from this study show how EOF analyses can provide information on spatiotemporal patterns of glacier mass-balance. Understanding such detailed variabilities in mass-balance on a Greenlandic glacier is of interest because a fifth of the Arctic contribution from glaciers and ice caps to sea-level rise originates from Greenland.  相似文献   

Silica diagenesis in Cenozoic mudstones of the North Viking Graben: physical properties and basin modelling          下载免费PDF全文

Thilo Wrona  Christopher A.‐L. Jackson  Mads Huuse  Kevin G. Taylor 《Basin Research》2017,29(Z1):556-575

Silica diagenesis can significantly change physical properties of the host strata and release large volumes of water. Predicting these changes and their timing is essential to understanding compaction, fluid flow and rock deformation in sedimentary basins. In this paper, the influence of silica diagenesis (opal‐A/CT transformation) on physical properties is determined, the sediment volume affected by these changes is mapped, and a new technique to model silica diagenesis is introduced. A petrophysical analysis of 16 exploration wells shows that the opal‐A/CT transformation leads to a porosity reduction of c.20% (from 49 to 29%) in Cenozoic mudstones of the North Viking Graben. Using three‐dimensional seismic reflection data, it is shown that the c.50 m thick opal‐A/CT transformation zone covers an area of >1500 km², equating to a minimum volume of 75 km³. The spatial and temporal evolution of opal‐A/CT transformation is simulated using an innovative basin modelling approach, the results of which indicate that the transformation started around Middle‐to‐Late Eocene times and then migrated upwards until it gradually fossilised between the Miocene and present. These findings are important, as they help understanding how these sediments compact and when fluids are released by diagenesis.  相似文献   

Making a living in the cocoa frontier,Western Ghana: Diversifying incomes in a cocoa economy     

Michael Helt Knudsen 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(2):29-44

Geografisk Tidsskrift, Danish Journal of Geography 107(2):29–44, 2007

The literature on livelihoods in rural Africa has for the past decade documented and discussed the growing importance of non-farm income for rural livelihoods and often linked this to an increasing divorce of rural livelihoods from farming and land. This paper challenges the view that the increasing importance of income earned on non-farm activities is a direct expression of processes of deagrari-anisation. Drawing on empirical evidence from recent research in the Ghanaian cocoa frontier, the paper shows that a growing importance of income from non-farm activities is evident, but that incomefrom cocoa is still the determining factor for most households' income and thereby for the demand for non-farm goods and investment in the non-farm sector. By identifying two overall factors explaining the level of income diversification, the paper questions how generally applicable processes of deagrarianisation are in the Ghanaian case. Firstly, the actual crop cultivated and its price and marketing possibilities are of great importance for a farmer's choice to engage and stay in the agricultural sector or to diversify into non-farm activities. Secondly, different dynamics are evident between settlements dominated by either migrant or indigenous households, mainly due to unequal access to land. The paper argues that what on a general scale may look like processes of deagrarianisation during the last decade to a large extent can be explained by migrants without access to land who engage full-time in the nonfarm sector and by cocoa farmers diversifying their incomes, but not leaving a deteriorated agriculture.  相似文献   

Environmental reconstructions of Eemian Stage interglacial marine records in the Lower Vistula area,southern Baltic Sea     

Karen Luise Knudsen  Hui Jiang  Philip L. Gibbard  Peter Kristensen  Marit‐Solveig Seidenkrantz  Zofia Janczyk‐Kopikowa  Leszek Marks 《Boreas: An International Journal of Quaternary Research》2012,41(2):209-234

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