Decadal fingerprints of freshwater discharge around Greenland in a multi-model ensemble   总被引：2，自引：2，他引：0  

Didier Swingedouw  Christian B. Rodehacke  Erik Behrens  Matthew Menary  Steffen M. Olsen  Yongqi Gao  Uwe Mikolajewicz  Juliette Mignot  Arne Biastoch 《Climate Dynamics》2013,41(3-4):695-720

The recent increase in the rate of the Greenland ice sheet melting has raised with urgency the question of the impact of such a melting on the climate. As former model projections, based on a coarse representation of the melting, show very different sensitivity to this melting, it seems necessary to consider a multi-model ensemble to tackle this question. Here we use five coupled climate models and one ocean-only model to evaluate the impact of 0.1 Sv (1 Sv = 10⁶ m³/s) of freshwater equally distributed around the coast of Greenland during the historical era 1965–2004. The ocean-only model helps to discriminate between oceanic and coupled responses. In this idealized framework, we find similar fingerprints in the fourth decade of hosing among the models, with a general weakening of the Atlantic Meridional Overturning Circulation (AMOC). Initially, the additional freshwater spreads along the main currents of the subpolar gyre. Part of the anomaly crosses the Atlantic eastward and enters into the Canary Current constituting a freshwater leakage tapping the subpolar gyre system. As a consequence, we show that the AMOC weakening is smaller if the leakage is larger. We argue that the magnitude of the freshwater leakage is related to the asymmetry between the subpolar-subtropical gyres in the control simulations, which may ultimately be a primary cause for the diversity of AMOC responses to the hosing in the multi-model ensemble. Another important fingerprint concerns a warming in the Nordic Seas in response to the re-emergence of Atlantic subsurface waters capped by the freshwater in the subpolar gyre. This subsurface heat anomaly reaches the Arctic where it emerges and induces a positive upper ocean salinity anomaly by introducing more Atlantic waters. We found similar climatic impacts in all the coupled ocean–atmosphere models with an atmospheric cooling of the North Atlantic except in the region around the Nordic Seas and a slight warming south of the equator in the Atlantic. This meridional gradient of temperature is associated with a southward shift of the tropical rains. The free surface models also show similar sea-level fingerprints notably with a comma-shape of high sea-level rise following the Canary Current.  相似文献   

Competitive firms in thin regions in Norway: The importance of workplace learning     

Bjørn-Tore Flåten  Arne Isaksen  James Karlsen 《Norsk geografisk tidsskrift. Norwegian journal of geography》2015,69(2):102-111

The article departs from empirical studies of two competitive firms in an organisationally thin region in Norway. The main question in the article is how these firms have achieved global competitiveness. The article focuses its inquiry on how the firms organise their innovation activity, giving special attention to the firms' organisational learning and absorptive capacity. It is found that find that workplace learning enables the firms to utilise knowledge in uncommon ways. The learning rests on specific organisational traits in the firms, such as broad participation, long-term on-the-job training, the use of practice-based knowledge in innovation projects, and links to national and global knowledge sources. The characteristics of thin regions indicate that these traits make up a generally applicable strategy in such regions.  相似文献   

Consistent joint elastic‐electrical differential effective‐medium modelling of compacting reservoir sandstones     

Erling Hugo Jensen  Leiv‐J. Gelius  Tor Arne Johansen  Zhong Wang 《Geophysical Prospecting》2013,61(4):788-802

  相似文献   

Simulations of a Line W-based observing system for the Atlantic meridional overturning circulation     

Matthias Fischer  Arne Biastoch  Erik Behrens  Johanna Baehr 《Ocean Dynamics》2013,63(8):865-880

In a series of observing system simulations, we test whether the Atlantic meridional overturning circulation (AMOC) can be observed based on the existing Line W deep western boundary array. We simulate a Line W array, which is extended to the surface and to the east to cover the basin to the Bermuda Rise. In the analyzed ocean circulation model ORCA025, such an extended Line W array captures the main characteristics of the western boundary current. Potential trans-basin observing systems for the AMOC are tested by combining the extended Line W array with a mid-ocean transport estimate obtained from thermal wind “measurements” and Ekman transport to the total AMOC (similarly to Hirschi et al., Geophys Res Lett 30(7):1413, 2003). First, we close Line W zonally supplementing the western boundary array with several “moorings” in the basin (Line W-32°N). Second, we supplement the western boundary array with a combination of observations at Bermuda and the eastern part of the RAPID array at 26°N (Line W-B-RAPID). Both, a small number of density profiles across the basin and also only sampling the eastern and western boundary, capture the variability of the AMOC at Line W-32°N and Line W-B-RAPID. In the analyzed model, the AMOC variability at both Line W-32°N and Line W-B-RAPID is dominated by the western boundary current variability. Away from the western boundary, the mid-ocean transport (east of Bermuda) shows no significant relation between the two Line W-based sections and 26°N. Hence, a Line W-based AMOC estimate could yield an estimate of the meridional transport that is independent of the 26°N RAPID estimate. The model-based observing system simulations presented here provide support for the use of Line W as a cornerstone for a trans-basin AMOC observing system.  相似文献   

The genesis of Pb‐Zn sulphide occurrences in the Lower Devonian Buchan Group,Victoria     

D. C. Arne  P. W. Cromie  J. A. Webb  J. R. Richards 《Australian Journal of Earth Sciences》2013,60(2):75-90

Six minor sulphide occurrences hosted by the Lower Devonian Buchan Group have been investigated. Sulphide minerals and associated phases are hosted by both dolostone and limestone lithologies along stylolitized bedding planes, cross‐cutting fractures, low angle minor faults and in cavities. Mineralization was closely associated with minor structures of inferred Tabberabberan age (Middle Devonian), which it appears to have post‐dated, but was largely strata‐bound in nature. The mineralogy of the occurrences is simple and characterized by the following generalized paragenesis which reflects the increasing oxidation state and pH of the mineralizing fluids: pyrite (pseudomorphous after marcasite)‐galena ± sphalerite ± pyrite‐dolomite ± barite‐calcite ± fluorite ± dolomite.

The sulphur isotope composition of sulphide minerals varies from ‐32.1 to +4.1‰, with iron and base metal sulphide minerals forming two distinct populations around ‐25‰ and 0‰, respectively. A single barite sample gives a sulphur isotope composition of +22.4‰, which is similar to that estimated for Early Devonian seawater. Fluid inclusions in fluorite and calcite homogenize at temperatures in the range 160 to 212° C and have average salinities of approximately 10 wt% NaCI eq. Sphalerite contains up to 1.81 wt% iron which correlates with colour, and up to 1.43 wt% cadmium. The Pb isotopic pattern of galena suggests a source region with U/Pb(= μ) lower than the crustal average, and a high Th/U.

A genetic hypothesis is proposed which involves the circulation of saline fluids through the Snowy River Volcanics, which directly underlie the Buchan Group, during or at some time after the Tabberabberan Orogeny. Although the Buchan occurrences show features characteristic of both Mississippi Valley‐type and stratiform ore deposits, they are most directly comparable to the epigenetic zones of Irish carbonate‐hosted base‐metal deposits. However, Pb‐Zn sulphide mineralization at Buchan appears to have been associated with minor compressional structures, suggesting that a simple correlation with the Irish deposits is not directly applicable.  相似文献   

Airborne Gravimetry Survey for the Marine Area of the United Arab Emirates     

Rene Forsbergbi  Arne Vestergaard Olesen  Adel Alshamsi  Arne Gidskehaug  Sahrum Ses  Majid Kadir 《Marine Geodesy》2013,36(3):221-232

The Military Survey Department (MSD) of the United Arab Emirates (UAE) undertook an airborne gravity survey project for the marine area of the country in 2009, especially to strengthen the marine and coastal geoid in the near-shore regions. For the airborne gravity survey, 5 km spacing coast-parallel flight lines were planned and surveyed. These lines were supplemented by cross-lines in order to assess the quality of the airborne gravity surveys. The flight lines were extended 10 km, spacing lines further offshore. A Beech King Air 350 aircraft was used for the surveys, collecting data at a typical flight speed of 170 knots and a typical flight elevation of 900–1500 m, depending on weather conditions and topography. Gravity was measured with a ZLS-modified LaCoste and Romberg gravimeter (S-99), augmented with a Honeywell strap-down inertial navigation system unit. The estimated accuracy for the airborne gravity data is better than 2.0 mGal r.m.s., as judged from the airborne track crossovers. The new airborne gravimetry data changed the UAE coastal geoid by up to 30 cm in some regions, highlighting the importance of airborne gravity coastal surveys.  相似文献   

Modeling the role of rainfall patterns in seasonal malaria transmission     

Arne Bomblies 《Climatic change》2012,112(3-4):673-685

Seasonal total precipitation is well known to affect malaria transmission because Anopheles mosquitoes depend on standing water for breeding habitat. However, the within-season temporal pattern of the rainfall influences persistence of standing water and thus rainfall patterns can also affect mosquito population dynamics in water-limited environments. Here, using a numerical simulation, I show that intraseasonal rainfall pattern accounts for 39% of the variance in simulated mosquito abundance in a Niger Sahel village where malaria is endemic but highly seasonal. I apply a field validated coupled hydrology and entomology model. Using synthetic rainfall time series generated using a stationary first-order Markov Chain model, I hold all variables except hourly rainfall constant, thus isolating the contribution of rainfall pattern to variance in mosquito abundance. I further show the utility of hydrology modeling using topography to assess precipitation effects by analyzing collected water. Time-integrated surface area of pools explains 70% of the variance in simulated mosquito abundance from a mechanistic model, and time-integrated surface area of pools persisting longer than 7?days explains 82% of the variance. Correlations using the hydrology model output explain more variance in mosquito abundance than the 60% from rainfall totals. I extend this analysis to investigate the impacts of this effect on malaria vector mosquito populations under climate shift scenarios, holding all climate variables except precipitation constant. In these scenarios, rainfall mean and variance change with climatic change, and the modeling approach evaluates the impact of non-stationarity in rainfall and the associated rainfall patterns on expected mosquito activity.  相似文献   

Determining return water levels at ungauged coastal sites: a case study for northern Germany   总被引：1，自引：0，他引：1  

Arne Arns  Thomas Wahl  Ivan D. Haigh  Jürgen Jensen 《Ocean Dynamics》2015,65(4):539-554

  相似文献   

The Origin of the Proterozoic Bidjovagge Gold-Copper Deposit, Finnmark, Northern Norway, as Deduced from Rare Earth Element and Nd Isotopic Evidences on Calcites     

Feng–Jun NIE  Arne BJ&#;RLYKKE  Kjell S. NILSEN 《Resource Geology》1999,49(1):13-25

Abstract: The Bidjovagge gold-copper deposit, northern Norway occurs in the lower Proterozoic Kautokeino greenstone belt, and consists of ten ore bodies in albite felsite, graphite schist and meta-diabase sills, along with a series of syenodiorite dykes. Calcite is one of the most important gangue minerals occurring within the ore veins. The early primary calcite samples from A, C and D ore bodies (copper–rich) show almost flat chondrite-normalised REE curves, and slightly positive Eu anomalies. A Sm-Nd isotope age of 1858 ± 72 Ma (2ρ) has been given based on fifteen primary calcite samples. The Sm-Nd age of calcite is in well agreement with previously published U-Pb davidite age of 1885 ±18 Ma (2ρ) and Sm-Nd davidite age of 1886 ± 88 Ma (2ρ). All these isotopic age data indicate that the gold-copper mineralisation may occur during or slightly after the peak of the Svecokarelian orogeny. Two late primary calcite samples from C and D ore bodies have flat chondrite-normalised LREE curves, positive HREE curves, and negative Eu anomalies. In contrast, most of the early primary calcite samples from B ore body (gold–rich) show an overall negative chondrite-normalised REE slope and negative Eu anomalies. Sm-Nd data on seven primary calcite samples from the B ore body are relatively scattered, and gave an isochrone age of 1809 ± 150 Ma (2ρ), identical to the age of the calcite samples from A, C and D ore bodies. Two late primary calcite samples from the B ore body have almost flat chondrite-normalised REE slope and negative Eu anomalies. REE patterns and eNd (T) values of calcites suggest that the ore fluids for the calcites from the A, C and D ore bodies derived their metals from mafic igneous rocks (diabase sills). For the secondary calcites from the C ore body, their relative high initial Nd (T) values at 1858 Ma imply that much more radiogenic Nd-component were incorporated during calcite crystallisation when another ore fluid emplaced. Combined Nd isotope data and REE geochemical features suggest that the isotopically more evolved source such as albite felsite and syn-genetic high level syenodiorite dykes were probably metal source for these calcites in the B ore body. Three samples of secondary calcite from the B ore body, which obviously deviated from 1809 Ma isochron are easily explained as products of post-ore hydrothermal events.  相似文献   

The point of no return and pectoral angle of Japanese anchovy(Engraulis japonicus) larvae during growth and starvation     

WAN Ruijing  LI Xiansen  ZHUANG Zhimeng  JOHANNESSEN Arne 《海洋学报(英文版)》2007,26(5):144-152

At a temperature of 23.0~24.8℃,the mixed feeding of Japanese anchovy larvae was initiated 24 h before the yolk-sac was exhausted.The point of no return(PNR) was reached on the 6th day after hatching.On the 4th day after hatching,the pectoral angle appeared in both fed and unfed anchovy larvae although it was more evident and sharper in the starved and the PNR stage larvae than in the fed ones.According to observations of larvae collected in the sea,the pectoral angles were evident not only in the larvae of 3.62~7.44 mm in standard length,but also in the larvae of 2.70 mm in standard length with remnants of yolk.The pectoral angles became diffuse when the larvae reached 7.84 mm and vanished at 9.86 mm.The pectoral angle cannot be used as a criterion to distinguish healthy from starving larvae.  相似文献