Satellite-based terrestrial production efficiency modeling     

Ian McCallum  Wolfgang Wagner  Christiane Schmullius  Anatoly Shvidenko  Michael Obersteiner  Steffen Fritz  Sten Nilsson 《Carbon balance and management》2009,4(1):8-14

Production efficiency models (PEMs) are based on the theory of light use efficiency (LUE) which states that a relatively constant relationship exists between photosynthetic carbon uptake and radiation receipt at the canopy level. Challenges remain however in the application of the PEM methodology to global net primary productivity (NPP) monitoring. The objectives of this review are as follows: 1) to describe the general functioning of six PEMs (CASA; GLO-PEM; TURC; C-Fix; MOD17; and BEAMS) identified in the literature; 2) to review each model to determine potential improvements to the general PEM methodology; 3) to review the related literature on satellite-based gross primary productivity (GPP) and NPP modeling for additional possibilities for improvement; and 4) based on this review, propose items for coordinated research.  相似文献   

Identification of sinkhole development mechanism based on a combined geophysical study in Nahal Hever South area (Dead Sea coast of Israel)   总被引：2，自引：0，他引：2  

Michael Ezersky  Anatoly Legchenko  Christian Camerlynck  Abdallah Al-Zoubi 《Environmental Geology》2009,58(5):1123-1141

Seismic refraction, magnetic resonance sounding (MRS), and the transient electromagnetic (TEM) method were applied to investigate the geological and hydrogeological conditions in the Nahal Hever South sinkhole development area at the Dead Sea (DS) coast of Israel. Microgravity and MRS results reliably reveal large karst cavity in the central part of investigated area. The map of the seismic velocity shows that sinkholes in Nahal Hever can be divided into two major groups: sinkholes close to the salt edge and sinkholes over compact salt formations between a few tens to a hundred meters from the major cavern. The present study shows that the formation of sinkholes of the first group is caused by soil collapsing into the cavern. In the area occupied by sinkholes of the second group, karst was not detected either by MRS or by seismic diffraction methods. TEM results reveal shallow clay layer saturated with DS brine underlain sinkholes of this group. It allows suggestion that the water drainage and intensive water circulation during rain events wash out fine rock particles from the unsaturated zone into the pre-existing cavern, initiating the formation of sinkholes of the second group. Karst development takes place at a very low bulk resistivity (<1 Ω m) of the DS aquifer, attesting to the fact that pores are filled with a highly saline solution. Refilling of the karstic cavities with collapsing and flushed soil slows down sinkhole development in the area. The sinkhole formation cycle at the site is estimated at 10 years. Sinkhole development throughout the studied area is triggered by a drop in the level of the DS, which reduces the head of the confined aquifer and the strength of the overlain sediments.

Abdallah Al-ZoubiEmail:

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An unusual anomaly of ice conditions in the eastern seas of the Russian Arctic and in the arctic basin in summer 2007     

Yu. A. Gorbunov  S. M. Losev  V. T. Sokolov 《Russian Meteorology and Hydrology》2010,35(8):545-553

It is demonstrated that during the whole annual cycle of ice cover evolution in 2006–2007 in the eastern seas of the Russian Arctic and in the Arctic basin, the factors whose effect led to the formation of an extremely large anomaly of ice conditions in summer 2007 were revealed. By the end of summer, the ice melted on the huge water area of 3500000 km². In September, the ice edge between the meridians of 150° E-170° W reached the parallel of 85° N. The estimates of the open water area being formed due to the ice melting and its drifting edge shift are given.  相似文献   

Evidence of multiple thermokarst lake generations from an 11 800‐year‐old permafrost core on the northern Seward Peninsula,Alaska          下载免费PDF全文

Josefine Lenz  Sebastian Wetterich  Benjamin M. Jones  Hanno Meyer  Anatoly Bobrov  Guido Grosse 《Boreas: An International Journal of Quaternary Research》2016,45(4):584-603

Permafrost degradation influences the morphology, biogeochemical cycling and hydrology of Arctic landscapes over a range of time scales. To reconstruct temporal patterns of early to late Holocene permafrost and thermokarst dynamics, site‐specific palaeo‐records are needed. Here we present a multi‐proxy study of a 350‐cm‐long permafrost core from a drained lake basin on the northern Seward Peninsula, Alaska, revealing Lateglacial to Holocene thermokarst lake dynamics in a central location of Beringia. Use of radiocarbon dating, micropalaeontology (ostracods and testaceans), sedimentology (grain‐size analyses, magnetic susceptibility, tephra analyses), geochemistry (total nitrogen and carbon, total organic carbon, δ¹³C_org) and stable water isotopes (δ¹⁸O, δD, d excess) of ground ice allowed the reconstruction of several distinct thermokarst lake phases. These include a pre‐lacustrine environment at the base of the core characterized by the Devil Mountain Maar tephra (22 800±280 cal. a BP, Unit A), which has vertically subsided in places due to subsequent development of a deep thermokarst lake that initiated around 11 800 cal. a BP (Unit B). At about 9000 cal. a BP this lake transitioned from a stable depositional environment to a very dynamic lake system (Unit C) characterized by fluctuating lake levels, potentially intermediate wetland development, and expansion and erosion of shore deposits. Complete drainage of this lake occurred at 1060 cal. a BP, including post‐drainage sediment freezing from the top down to 154 cm and gradual accumulation of terrestrial peat (Unit D), as well as uniform upward talik refreezing. This core‐based reconstruction of multiple thermokarst lake generations since 11 800 cal. a BP improves our understanding of the temporal scales of thermokarst lake development from initiation to drainage, demonstrates complex landscape evolution in the ice‐rich permafrost regions of Central Beringia during the Lateglacial and Holocene, and enhances our understanding of biogeochemical cycles in thermokarst‐affected regions of the Arctic.  相似文献   

Dolomite-calcite textures in early carbonatites of the Kovdor ore deposit,Kola peninsula,Russia: their genesis and application for calcite-dolomite geothermometry     

Anatoly Zaitsev  Ludmila Polezhaeva 《Contributions to Mineralogy and Petrology》1994,115(3):339-344

In early calcite carbonatites of the Kovdor ore deposit four morphological types of dolomite are represented. In the first type, dolomite microcrystals occur as lamellae enclosed by optically continuous calcite. In the second, dolomite microcrystals occur as segmented rods, plates and xenomorphic grains, enclosed by optically discontinuous calcite, and in the third, dolomite is represented by grains of various morphologies, situated along calcite grain boundaries. The fourth type of dolomite occurs as a fine-grained aggregate, which develops along grain boundaries and cleavage cracks of calcite. From microscopic, scanning electron microscope and microprobe studies of these different types of dolomite microcrystals, as well as the calcite associated with them, it can be concluded that the first type of dolomite was exsolved from magnesian calcite during cooling. The second, and the third types of dolomite microcrystals were formed by recrystallization. The fourth type of dolomite was formed by metasomatic dolomitization. As the result of these two processes-recrystallization and metasomatic dolomitization-early dolomite microcrystals seldom occur. The composition of the early-formed primary magnesian calcite yielded temperatures of exsolution of dolomite from magnesian calcite between 665 and 700°C.  相似文献   

The usage of MTVZA-GYa satellite microwave radiometer observations in the data assimilation system of the Hydrometcenter of Russia     

D. R. Gayfulin  M. D. Tsyrulnikov  A. B. Uspensky  E. K. Kramchaninova  S. A. Uspensky  P. I. Svirenko  M. E. Gorbunov 《Russian Meteorology and Hydrology》2017,42(9):564-573

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Alpine-type tectonics in the Paleoproterozoic Lapland-Kola Orogen     

S. V. Mudruk  V. V. Balagansky  I. A. Gorbunov  A. B. Raevsky 《Geotectonics》2013,47(4):251-265

The Kola region in the northeastern Baltic Shield is characterized by diverse Paleoproterozoic collision processes. The Keivy Terrane is one of the major tectonic units in the northeastern foreland of the Paleoproterozoic Lapland-Kola Collisional Orogen, which markedly differs in a number of parameters from other tectonic units of the Kola region. The study of the Keivy Terrane allowed us to unravel one more basic difference: the large Paleoproterozoic sheath synform of the Serpovidny (Crescentic) Range localized in this terrane. Its core is occupied by volcanic and sedimentary rocks, which correlate with the fill of the Imandra-Varzuga Rift; the limbs are composed of metamorphosed mature sedimentary rocks known as Keivy paraschists of Neoarchean or Paleoproterozoic age. The lower limb of the Serpovidny Synform is strongly squeezed, whereas the upper limb consists of almost undeformed rocks. The deformed rocks underwent ductile flow under conditions of simple or general shear. In the degree of its asymmetry and main parameters, the Serpovidny Synform is similar to the plunging and recumbent anticlines in the Helvetic nappes of the Alps. It is concluded that the Paleoproterozoic core of the Serpovidny Sheath Synform, or plunging anticline, is a fragment of the almost completely eroded deep Serpovidny Nappe of the Helvetic type. During the collision related to the Lapland-Kola Orogeny (1.9–2.0 Ga), this nappe was pushed out northward from the Paleoproterozoic Imandra-Varzuga Rift, which is situated 50 km south of the Serpovidny structure, and thrust over the Keivy paraschists. The latter, together with underlying the Lebyazhka Gneiss, were folded in the process of thrusting and were involved in the structure of the Serpovidny Synform. The Keivy paraschists make up a para-autochthon or a separate nappe of the Pennine type. The Archean Lebyazhka metafelsic volcanics underlie the Keivy paraschists and overlie granitoids of the Archean basement that remained undeformed during thrusting. Most likely, they also belong to the para-autochthon; however, it cannot be ruled out that, like the Keivy paraschists, they occur as a Pennine-type nappe. The large sheath folds known in the Paleoproterozoic and Phanerozoic orogens are genetically related to deep-seated nappes or channel-flow tectonics. Paleoproterozoic and Phanerozoic orogens are similar in this respect.  相似文献   

Methane fluxes and gas hydrates as well as seismic activity in the Okhotsk Sea     

Anatoly Obzhirov 《东北亚地学研究》2006,9(2):161-163

The research works of methane concentration in water column of the Okhotsk Sea from 1984 to 2005 were reviewed.And some regularities of methane distribution in water column in the North-East Sakhalin slope of the Okhotsk Sea were concluded.  相似文献   

El'gygytgyn impact crater,Russia: Structure,tectonics, and morphology     

Eugene P. Gurov  Christian Koeberl  Anatoly Yamnichenko 《Meteoritics & planetary science》2007,42(3):307-319

Abstract— The 3.6 Myr old El'gygytgyn impact crater is located in central Chukotka, northeastern Russia. The crater is a well‐preserved impact structure with an inner basin about 15 km in diameter, surrounded by an uplifted rim about 18 km in diameter. The flat floor of the crater is in part occupied by Lake El'gygytgyn, 12 km in diameter, and surrounding terraces. The average profile of the rim is asymmetric, with a steep inner wall and a gentle outer flank. The rim height is about 180 m above the lake level and 140 m above the surrounding area. An outer ring feature, on average 14 m high, occurs at about 1.75 crater radii from the center of the structure. El'gygytgyn crater is surrounded by a complex network of faults. The density of the faults decreases from the bottom of the rim to the rim crest and outside the crater to a distance of about 2.7 crater radii. Lake El'gygytgyn is surrounded by a number of lacustrine terraces. Only minor remnants are preserved of the highest terraces, 80 and 60 m above the present‐day lake level. The widest of the terraces is 40 m above the current lake level and surrounds the lake on the west and northwest sides. The only outlet of the lake is the Enmivaam River, which cuts through the crater rim in the southeast. In terms of structure, El'gygytgyn is well preserved and displays some interesting, but not well understood, features (e.g., an outer ring), similar to those observed at a few other impact structures.  相似文献   

Discs and haloes in pre-main-sequence stars     

Dejan Vinkovi&#;  &#;eljko Ivezi&#;  Anatoly S. Miroshnichenko  Moshe Elitzur 《Monthly notices of the Royal Astronomical Society》2003,346(4):1151-1161

We study the infrared (IR) emission from flared discs with and without additional optically thin haloes. Flux calculations of a flared disc in vacuum can be considered a special case of the more general family of models in which the disc is imbedded in an optically thin halo. In the absence of such a halo, flux measurements can never rule out its existence because the disc flaring surface defines a mathematically equivalent halo that produces the exact same flux at all IR wavelengths. When a flared disc with height H at its outer radius R is imbedded in a halo whose optical depth at visual wavelengths is  τ_halo  , the system IR flux is dominated by the halo whenever  τ_halo > (1/4) H / R   . Even when its optical depth is much smaller, the halo can still have a significant effect on the disc temperature profile. Imaging is the only way to rule out the existence of a potential halo, and we identify a decisive test that extracts a signature unique to flared discs from imaging observations.  相似文献