forty years of ttg research abstract ttgs tonalite trondhjemite granodiorite are one of the archetypical lithologies of archaean cratons since their original description in the 1970s they have been the subject of many studies and discussions relating to archaean geology in this paper we review the ideas concepts and arguments brought forward in these 40 years and try to address some open questions both old and new the late 1960s and the 1970s mark the appearance of grey gneisses ttg in the scientific literature during this period most work was focused on the identification and description of this suite and the recognition that it is a typical archaean lithology ttgs were already recognised as generated by melting of mafic rocks this was corroborated during the next decade when detailed geochemical ttg studies allowed us to constrain their petrogenesis melting of garnet bearing metamafic rocks and to conclude that they must have been generated by archaean geodynamic processes distinct from their modern counterparts however the geodynamic debate raged for the following 30 years as many distinct tectonic scenarios can be imagined all resulting in the melting of mafic rocks in the garnet stability field the 1990s were dominated by experimental petrology work a wealth of independent studies demonstrated that melting of amphibolites as well as of mafic eclogites can give rise to ttg liquids whether amphibolitic or eclogitic conditions are more likely is still an ongoing debate from 1990s onwards one of the key questions became the comparison with modern adakites as originally defined these arc lavas are reasonably close equivalents to archaean ttgs pending issues largely revolve around definitions as the name ttg has now been applied to most archaean plutonic rocks whether sodic or potassic irrespective of their hree contents this leads to a large range of petrogenetic and tectonic scenarios a fair number of which may well have operated concurrently but are applicable only to some of the rocks lumped together in the ever broadening ttg bin

a general rule for synoptic eddy feedback onto low frequency flow in this study scale interaction between synoptic eddies and low frequency flow is investigated it is demonstrated here that there is a general rule the left hand rule that describes synoptic eddy feedback onto low frequency flow the rule is that low frequency anomalies systematically stir and deform the transient eddies in such a way that the irrotational eddy vorticity fluxes are directed preferentially about 90 toward the left hand side of the low frequency flow thus this eddy feedback plays a positive role in maintaining and prolonging low frequency flow under the stormy atmosphere similarly we show that the irrotational eddy temperature and moisture fluxes are also directed preferentially about 90 toward the left hand side of the low frequency flow in the northern hemisphere the eddy temperature fluxes and their vertical structure play a positive role in reinforcing the low frequency flow in the low levels the moisture fluxes play a role in enhancing low frequency flow by providing eddy induced moisture convergence and divergence

impact of the german harz mountain weichselian ice shield and valley glacier development onto palaeolithic and megafauna disappearances abstract three pleistocene stages are recorded by 3d google earth geomorphology cave sediments river terraces megafauna archaeological sites of the harz mountain range and its forelands of northern germany central europe peak 1141 a s l late pleistocene glaciation stages are modeled preliminary in valley elevations between 407 and 760 a s l starting all southeast below the brocken ice field above 750 a s l the 14 11 km long oder and bode valley glaciers left typical moraines kames or dead ice depressions such as fluvial cave relic sediments the bode river glacier passed during the lgm the rubeland caves where it deposited reworked kames lateral moraines in the baumann s cave which floods mixed a neanderthal camp leopard lair and cave bear den area 60 km downstream fluvial to aeolian deposits were trapped in the gypsum karst doline westeregeln neanderthal camp hyena den late aurignacians replaced in the region neanderthals but a gap of late palaeolithic gravettian magdalenian 26 000 16 000 bp settlement and latest starting speleothem genesis around 24 260 568 bp correlate to the lgm when an arctic reindeer fauna with alpine elements ibex chamois accumulated in bone assemblages of a wolverine polar fox mustelid such as european eagle owl dens which allow landscape reconstructions

geomorphometry and landform mapping what is a landform abstract starting from a concept of the land surface its definition and subdivision from digital elevation models dems is considered high resolution dems from active remote sensing form a new basis for geomorphological work which is moving on from consideration of whether data are accurate enough to how the surface of interest can be defined from an overabundance of data discussion of the operational definition and delimitation of specific landforms of varying degrees of difficulty from craters to mountains is followed by the applicability of fuzzy boundaries scaling usually allometric is shown to be compatible with the scale specificity of many landforms this is exemplified by glacial cirques and drumlins classification of a whole land surface is more difficult than extraction of specific landforms from it well dissected fluvial landscapes pose great challenges for areal analyses these are tackled by the delimitation of homogeneous elementary forms and or land elements in which slope position is considered the boundaries are mainly breaks in gradient or aspect but may also be in some type of curvature breaks in altitude are rare elementary forms or land elements are grouped together into functional regions landforms such as hill sheds it may often be useful to recognise fuzziness of membership or core and periphery of a surface object plains and etched or scoured surfaces defy most of these approaches and general geomorphometry remains the most widely applicable technique it has been applied mainly within arbitrary areas and to some extent to drainage basins but more experimentation with mountain ranges and other landforms or landform regions is needed geomorphological mapping is becoming more specialised and its legends are being simplified its incorporation into geographical information systems gis has required greater precision with definitions and the separation of thematic layers so that it is converging with specific geomorphometry and becoming more flexible and more applicable with a broader range of visualisation techniques

interannual and decadal modulations recently observed in the pacific storm track activity and east asian winter monsoon abstract interannual variability of the north pacific storm track observed over 17 recent winters is documented the local storm track activity is measured by a meridional flux of sensible heat associated with the lower tropospheric subweekly fluctuations the interannual variability in the heat flux over the northwestern nw pacific is found to be strongest in midwinter the first empirical orthogonal function of the interannual variability in midwinter captures the decadal tendency toward the enhanced storm track activity in midwinter over the nw pacific in association with the decadal weakening of the east asian winter monsoon siberian high and the aleutian low that occurred in the late 1980s the most marked signature of this enhancement is that the midwinter minimum in the storm track activity which had been apparent in the early to mid 1980s almost disappeared afterward as opposed to linear theory of baroclinic instability the enhanced activity occurred despite the weakening of the pacific j

chronology of the late weichselian glaciation in the bohemian forest in central europe abstract a glacial chronology based on in situ produced 10 be surface exposure dating of moraines in the bohemian forest central europe was established eleven exposure ages obtained for moraine boulders in the prasilske lake and laka lake valleys czech republic were complemented by 10 be ages from kleiner arbersee germany recalculated according to recently calibrated production rates in the northern hemisphere the glacial phases in the bohemian forest occurred during the last glacial maximum around 24 1 2 5 23 6 2 4 21 8 2 0 and 19 5 2 1 ka following phases of local glaciation occurred during the northern hemisphere deglaciation period around 16 ka and 14 ka the last indicated phase may correlate with older dryas the glacial chronology of the bohemian forest is in agreement with local glaciation chronologies in the giant mts krkonose mts and the eastern alps

the role of synoptic waves in the formation and maintenance of the western hemisphere circulation pattern abstractprevious studies have demonstrated that the nao the leading mode of atmospheric low frequency variability over the north atlantic could be linked to northeast pacific climate variability via the downstream propagation of synoptic waves in those studies the nao and the northeast pacific climate variability are considered as two separate modes that explain the variance over the north atlantic sector and the east pacific north american sector respectively a newly identified low frequency atmospheric regime the western hemisphere wh circulation pattern provides a unique example of a mode of variability that accounts for variance over the whole north atlantic north american north pacific sector the role of synoptic waves in the formation and maintenance of the wh pattern is investigated using the ecmwf reanalysis datasets persistent wh events are characterized by the propagation of quasi stationary rossby waves across the north pacific north american north atlantic regions and by associated s

application of field geophysics in geomorphology advances and limitations exemplified by case studies abstract during the last decade the use of geophysical techniques has become popular in many geomorphological studies however the correct handling of geophysical instruments and the subsequent processing of the data they yield are difficult tasks furthermore the description and interpretation of geomorphological settings to which they apply can significantly influence the data gathering and subsequent modelling procedure e g achieving a maximum depth of 30 m requires a certain profile length and geophone spacing or a particular frequency of antenna for more than three decades geophysical techniques have been successfully applied for example in permafrost studies however in many cases complex or more heterogeneous subsurface structures could not be adequately interpreted due to limited computer facilities and time consuming calculations as a result of recent technical improvements geophysical techniques have been applied to a wider spectrum of geomorphological and geological settings this paper aims to present some examples of geomorphological studies that demonstrate the powerful integration of geophysical techniques and highlight some of the limitations of these techniques a focus has been given to the three most frequently used techniques in geomorphology to date namely ground penetrating radar seismic refraction and dc resistivity promising applications are reported for a broad range of landforms and environments such as talus slopes block fields landslides complex valley fill deposits karst and loess covered landforms a qualitative assessment highlights suitable landforms and environments the techniques can help to answer yet unsolved questions in geomorphological research regarding for example sediment thickness and internal structures however based on case studies it can be shown that the use of a single geophysical technique or a single interpretation tool is not recommended for many geomorphological surface and subsurface conditions as this may lead to significant errors in interpretation because of changing physical properties of the subsurface material e g sediment water content in many cases only a combination of two or sometimes even three geophysical methods gives sufficient insight to avoid serious misinterpretation a good practice guide has been framed that provides recommendations to enable the successful application of three important geophysical methods in geomorphology and to help users avoid making serious mistakes

generation of eoarchean continental crust from altered mafic rocks derived from a chondritic mantle the 3 72 ga aktash gneisses tarim craton nw china abstract our understanding of crust mantle evolution and geodynamics of the early earth has been hampered by the scarcity of hadean to eoarchean rocks and by the almost ubiquitous isotopic disturbance of the oldest rocks here we present in situ zircon u pb ages o oh and lu hf isotopes as well as whole rock sr nd hf pb isotopes for the recently identified eoarchean aktash gneisses in the tarim craton nw china the new age data confirm that the aktash gneisses were formed at least by 3 72 ga and were affected by two metamorphic events at 3 56 and 2 0 ga respectively whole rock isotopic data show that the sr nd hf pb isotopic systematics have all been variously disturbed by 2 0 ga regional granulite facies metamorphism resulting in decoupling of nd hf isotopic systematics that is in some samples similar to that observed in sw greenland the least disturbed sample 16alt67 however yielded chondritic to slightly sub chondritic whole rock end 0 3 and ehf 0 9 this is consistent with the in situ magmatic zircon ehf weighted mean 0 2 to 1 8 for most samples of the aktash gneisses suggesting a mafic source derived from chondritic mantle with a short crustal residence time our data thus provide no evidence for the presence of an eoarchean depleted mantle or a hadean enriched crust implying that early earth crust mantle differentiation was either limited or balanced by large scale crustal recycling in situ zircon o oh data show that metamorphism and later alteration tend to decrease the zircon 18 o of the aktash gneisses and the weighed mean 18 o of pristine magmatic zircons 6 2 6 3 from the least disturbed samples indicate that the mafic source was mildly altered at low temperature by the early hydrosphere facilitating partial melting and formation of some of the earliest preserved continental crust known on earth

the oldest zircons of africa their u pb hf o isotope and trace element systematics and implications for hadean to archean crust mantle evolution abstract more than 450 detrital zircon grains from two limpopo belt quartzite samples were investigated by a combination of scanning electron imaging u pb dating 18 o lu hf isotope and trace element analyses in order to get robust information about the early earth s crust mantle evolution the detrital zircon grains have crystallization ages between 3 95 ga and 3 18 ga show hf t between 1 to 15 1 unit and 18 o vsmow mostly between 5 5 and 8 1 0 2 pristine zircon domains reveal ti in zircon temperatures between 700 and 865 c and th u of 0 3 2 3 trace elements point to zircon formation in predominately granitoid rocks metamorphic zircon rims have ages 2 65 ga hf 2 65ga 15 18 o 7 0 8 1 and th u mostly hf t age array i which starts from a chondritic uniform reservoir chur at about 4 5 ga and requires 176 lu 177 hf 0 020 indicative for mafic crust most zircon grains however plot on or above an hf t age array ii which runs parallel to array i 176 lu 177 hf 0 021 and starts from chur at 4 01 ga oxygen isotope compositions of 18 o 5 5 indicate that the magmatic host rocks of the zircons have been formed either by melting of altered mafic crust which interacted with cold water prior to granitoid formation and or that ancient sedimentary and or magmatic rocks were involved in the melting process the new u pb hf 18 o datasets together with compiled data from worldwide sources indicate a significant gap of about 5 epsilon units between arrays i and ii furthermore they illustrate that many hadean zircon analyses plot well below array i and some above chur these findings support an interpretation that the hadean earth was covered by a long lived mafic protocrust perhaps forming a partially open stagnant lid this protocrust was affected by internal reworking but also injected and overlain by ultra mafic rocks derived from chondritic and highly depleted mantle sources at

early crustal evolution of the superior craton a u pb hf and o isotope study of zircon from the assean lake complex and a comparison to early crust in other cratons abstract we report u pb hf o isotopic measurements of zircon extracted from meta igneous rocks exposed in the assean lake crustal complex northwestern superior craton canada with crystallization ages of ca 3 22 ga zircon from the assean lake crustal complex are among the oldest reported in the superior craton the hf and o isotope compositions of zircon indicate that these meta igneous rocks derive from a mantle component with a relatively primitive hf isotope composition similar to chondrites that was uncontaminated by elevated 18o material ehf initial 0 and 18ovsmow 5 5 these features are shared by the large majority of the zircon extracted from the oldest meta igneous rocks exposed in archean terranes positive ehf deviations in archean zircons are typically observed in magmas that post date the oldest magmatic activity in a given terrain this temporal variability in magma source regions may reflect a sequence of events comprising i felsic magmatism derived from undepleted mantle components followed by ii re melting of the same mantle component producing the depleted hf signatures in zircon and then iii accretion of the proto craton and reworking of the whole system enabling stabilization

from valley to marginal glaciation in alpine type relief lateglacial glacier advances in the piec stawow polskich roztoka valley high tatra mountains poland abstract the piec stawow polskich roztoka valley in the high tatras western carpathians features typical alpine type relief with a deeply incised glacial trough and large compound trough head cirque the prominent hypsographic maximum in the valley 1680 2000 m along with a broad cirque bottom had provided a vast space for recording glacial and periglacial landforms specifically the most recent lateglacial advances the valley has been intensively studied before in the context of glacial chronology in this paper we re establish the post last glacial maximum lgm glacial chronology of the valley via detailed geomorphologic mapping equilibrium line altitude ela reconstruction and schmidt hammer sh dating along with a critical review of previously published cosmogenic exposure age data 36 cl and lacustrine sediment chronology our results indicate that the first four of the five distinguished lateglacial stages roztoka i iii pusta i occurred before the bolling allerod b a interstadial thus virtually the entire valley became deglaciated in course of the oldest dryas cold phase a distinct reorganization of deglacial patterns from valley type to marginal type occurred before b a warming when the ela increased above the valley hypsographic maximum concentrated at the cirque bottom elevation it shows that noticeable deglaciation step can be caused due to topographic reason with a minimal climate forcing this points also to an important role of glaciated valley hypsography in regulating the distribution of moraines which is rarely taken into account in paleoglaciological reconstructions we infer that glaciers vanished in the tatra mountains during the b a interstadial later a renewed advance during the younger dryas pusta ii formed a nearly continuous festoon shaped pattern of moraines and rock glaciers in close distance to cirque backwalls furthermore we discus some paleoenvironmental significance of the geomorphological record in the valley as well the applicability of sh dating in constructing glacial chronology

extreme δ18o signatures in zircon from the saglek block north atlantic craton document reworking of mature supracrustal rocks as early as 3 5 ga

on the interpretation of eddy fluxes during a blocking episode abstract using twice daily synoptic charts objectively analyzed at the national meteorological centre horizontal eddy fluxes of temperature and quasi geostrophic potential vorticity are computed for the month of july 1976 when a blocking anticyclone was centered over western europe the local time averaged eddy variance equations are used to provide a dynamical basis for interpreting the spatial pattern of eddy fluxes and their relation to mean gradients it is shown that a rotational non divergent flux can be identified the cross gradient component of which balances the mean flow advection of eddy variance the remaining flux is the dynamically significant one which helps maintain the block and can be understood in terms of a response to sources and sinks of eddy variance

origins of two types of archean potassic granite constrained by mg isotopes and statistical geochemistry implications for continental crustal evolution abstract the chemical composition of the upper continental crust ucc dramatically changed from predominantly sodic to more potassic during the late archean 3000 2500 ma although how this change occurred remains poorly constrained the origins of neoarchean potassic granites may provide clues for this crucial change as their formation dominated the compositional transition of the ucc in this study we conducted high precision mg isotopic analyses of neoarchean potassic granites 2558 2520 ma and tonalite trondhjemite granodiorites ttgs 2595 2574 ma from the north china craton and statistical geochemistry in k2o na2o ratios of global archean granitoids results show that these ttgs with k2o na2o ratios of 0 61 and 26mg values of 0 39 to 0 22 were generated from heterogeneous basaltic sources in contrast potassic granites yield two distinctive groups of 26mg values and can be subdivided into i and s types the i type granite has mantle like 26mg values of 0 28 to 0 22 and weak enrichment in k2o k2o na2o 1 0 1 5 and was likely derived by partial melting of igneous sources the s type is characterized by much higher 26mg values of 0 60 to 0 91 and strong k2o enrichment k2o na2o 1 57 23 26 with geochemical characteristics suggesting derivation by partial melting of sediments based on the geochemical characteristics of the s type potassic granites in this study we sort the s type granites out of 4066 archean felsic igneous rocks worldwide their temporal distribution suggests that s type potassic granites have appeared in the middle archean 3500 3000 ma and became widespread in the late archean 3000 2500 ma but were scarce in the early archean 4000 3500 ma the onset of s type granites indicates reworking of supracrustal rocks may have started since 3500 ma and widespread s type potassic granites during 3000 2500 ma play an important role for the high k2o na2o ratio of ucc at the end of archean a mass balance calculation shows that 25 88 wt i type 4 12 wt s type potassic granite and 70 wt ttgs could increase the k2o na2o ratio of the ucc to 0 83 which is the global average value for felsic rocks at the end archean to increase k2o na2o of the archean ucc contributions made by i and s type potassic granites could probably reach 3 2 respectively consequently the evolved crustal composition from predominantly sodic to potassic results from the synergy of re working of igneous unaltered and sedimentary weathered rocks by which the former contributed more quantitatively while the latter contributed more efficiently

weichselian late pleniglacial surface winds over northwest and central europe a model data comparison reconstructions of the weichselian late pleniglacial wind direction in northwest and central europe are reviewed and compared with palaeoclimate simulations performed with an atmospheric general circulation model these reconstructions are based on proxy data containing information on former wind directions such as relic dune forms sediments and wind polished rock surfaces the objective is to investigate whether 1 the proxy information is internally consistent and 2 in agreement with the model simulations we find a general consensus in the proxy based reconstructions indicating a dominant westerly to northwesterly wind in winter during the late pleniglacial the model results indicate over the study area an atmospheric circulation in winter that is dominated by southwesterly to west northwesterly winds which are stronger than the southwesterly winds in the present day climate the main driving factors behind the anomalous atmospheric circulation in the late pleniglacial are the laurentide ice sheet and a colder north atlantic ocean with a relatively extensive sea ice cover leading to an eastward relocation of the icelandic low and an enhanced pressure gradient over northwest europe the minor difference in late pleniglacial wind direction between the reconstructions and model can be explained by a combination of pricertainties in the proxy data and the relatively low spatial resolution of the applied climate model copyright 2006 john wiley sons ltd

late glacial sediments of the stara jimka paleolake and the first finding of laacher see tephra in the czech republic the late glacial sedimentary sequence of the stara jimka paleolake bohemian forest czech republic is characterized by the prevalence of detrital minerals with an elevated proportion of organic matter and abundant diatom valves in relatively warm periods the mineral debris originated mainly from local migmatites and mica schists or glacial and deluvial deposits derived from the same material low background contents of cao 0 20 wt and na2o 0 50 wt reflect chemical weathering correlation analysis of trace elements shows that the mineral debris concentrates rb cs ga cr zr hf light rare earth elements th u pb ba sr and weakly zn whereas mo co se as ni cu br and weakly au are allocated predominantly to sulphides and organic matter the sequence contains a continuous horizon with the laacher see tephra lst causing contrasting maxima of na ca cl and nb in bulk composition while the phonolitic tephra corresponds to the lower part of the middle lst unit it also contains phosphorus rich relicts of older sediments with small euhedral air transported volcanic crystals such sediments may have occurred in depressions at an older volcano prior to the major laacher see eruption 12 880 cal bp

oxygen isotope trajectories of crystallizing melts insights from modeling and the plutonic record elevated oxygen isotope values in igneous rocks are often used to fingerprint supracrustal alteration or assimilation of material that once resided near the surface of the earth the 18 o value of a melt however can also increase through closed system fractional crystallization in order to quantify the change in melt 18 o due to crystallization we develop a detailed closed system fractional crystallization mass balance model and apply it to six experimentally and naturally determined liquid lines of descent llds which cover nearly complete crystallization intervals melt fractions of 1 to 0 1 the studied llds vary from anhydrous tholeiitic basalts to hydrous high k and calc alkaline basalts and are characterized by distinct melt temperature sio 2 trajectories as well as crystallizing phase relationships our model results demonstrate that melt fraction temperature sio 2 relationships of crystallizing melts which are strongly a function of magmatic water content will control the specific 18 o path of a crystallizing melt hydrous melts typical of subduction zones undergo larger increases in 18 o during early stages of crystallization due to their lower magmatic temperatures greater initial increases in sio 2 content and high temperature stability of low 18 o phases such as oxides amphibole and anorthitic plagioclase versus albite conversely relatively dry tholeiitic melts only experience significant increases in 18 o at degrees of crystallization greater than 80 total calculated increases in melt 18 o of 1 0 to 1 5 can be attributed to crystallization from 50 to 70 wt sio 2 for modeled closed system crystallizing melt compositions as an example application we compare our closed system model results to oxygen isotope mineral data from two natural plutonic sequences a relatively dry tholeiitic sequence from the upper and upper main zones uumz of the bushveld complex south africa and a high k hydrous sequence from the arc related dariv igneous complex mongolia these two sequences were chosen as their major and trace element compositions appear to have been predominantly controlled by closed system fractional crystallization and their llds have been modeled in detail we calculated equilibrium melt 18 o values using the measured mineral 18 o values and calculated mineral melt fractionation factors increases of 2 3 and 1 1 5 in the equilibrium melts are observed for the dariv igneous complex and the uumz of the bushveld complex respectively closed system fractional crystallization model results reproduce the 1 increase observed in the equilibrium melt 18 o for the bushveld uumz whereas for the dariv igneous complex assimilation of high 18 o material is necessary to account for the increase in melt 18 o values assimilation of evolved supracrustal material is also confirmed with sr and nd isotope analyses of clinopyroxene from the sequence beginning with a range of mantle derived basalt 18 o values of 5 7 pristine mantle to 7 0 heavily subduction influenced mantle our model results demonstrated that high silica melts i e granites with 18 o of up to 8 5 can be produced through fractional crystallization alone lastly we model the zircon melt 18 o fractionations of different llds emphasizing their dependence on the specific sio 2 t relationships of a given crystallizing melt wet relatively cool granitic melts will have larger zircon melt fractionations potentially by 1 5 compared to hot dry granites therefore it is critical to constrain zircon melt fractionations specific to a system of interest when using zircon 18 o values to calculate melt 18 o

cirque overdeepening and their relationship to morphometry abstract shape and size characteristics of cirques and their changes and mutual relationships include not only spatial and descriptive aspects but also genetic attributes the goals of this article were to define an application of k curve sensu haynes 1968 that describes the extent of cirque overdeepening and to identify k curve equation input variables the k values depend on the profile location and hence a clear definition of the cirque profile position is necessary therefore ideal profiles were delineated through the steepest part of the cirque headwall k steepest k s or through a point on the cirque crest that had a maximal elevation k highest k h knowledge of the cirque headwall height allows for the mathematical theoretical calculation of cirque overdeepening i e the maximum depth of the cirque floor sedimentary filling of the cirque floor further the goal of this study was to analyse and compare cirque classification methods according to the extent of overdeepening and standard morphometric characteristics as a training data set 27 example cirques of the bohemian massif giant mts sumava mts and hrub jesenik mts and a total of 12 morphometric characteristics were used in the analyses cirques were classified into two groups using cluster analysis based on the extent of overdeepening k values k h and k s a mutual relationship between cluster analysis classifications and classifications based on morphometric characteristics l w h and 3d 2d was determined using general discriminant analysis the classification of cirques based on other characteristics corresponded closely in total 81 for the first group and the cross validation group with cirque classifications based on the degree of overdeepening k value

laser ablation split stream analysis of the sm nd and u pb isotope compositions of monazite titanite and apatite improvements potential reference materials and application to the archean saglek block gneisses abstract continued improvements in both icpms inductively coupled plasma mass spectrometry and laser ablation technologies are fueling advancements in accessory mineral investigations and their related isotope systems of interest and are now being applied to a wide range of geological applications in this contribution we present an updated methodology for laser ablation split stream lass analysis of the light rare earth element lree enriched minerals monazite titanite and apatite for simultaneous analysis of the u th pb age or trace element content and the sm nd isotope system the data were collected with the current generation of high sensitivity icpms and laser systems thermofinnigan neptuneplus mc icpms and element xr sf icpms coupled to a resolution 193 nm arf excimer laser system the increased sensitivity of these icpms instruments allows for improved spatial resolution and the ability to target minerals which previously contained insufficient concentrations of elements of interest e g sm nd in apatite making their analysis difficult if not impossible using less sensitive instruments furthermore the higher sensitivity allows less aggressive ablation parameters that facilitate thin section sampling and reduces inter element and isotopic fractionation to assess and improve the accuracy precision and efficiency of the technique three new potential lass reference materials rms are evaluated for dual u pb and sm nd analysis tory hill apatite tory hill titanite and steenskralkamp monazite the homogeneity of these materials was first assessed using reconnaissance laser ablation analyses with final characterization of u pb age and sm nd isotope composition using isotope dilution thermal ionization mass spectrometry id tims the precision and accuracy of the lass method is explored using secondary mineral reference materials of known age and sm nd isotope composition the utility of the technique is evaluated with a case study of monazite and apatite from the eoarchean uivak gneiss complex of labrador canada finally we suggest that there is a wide variety of geological applications for this methodology such as multi mineral detrital provenance crustal growth and petrogenic studies

structure and mechanisms of the southern hemisphere summertime subtropical anticyclones abstract the three dimensional structure and dynamics of the climatological mean summertime subtropical anticyclones in the southern hemisphere sh are investigated as in the northern hemisphere nh each of the surface subtropical anticyclones over the south pacific south atlantic and south indian oceans is accompanied by a meridional vorticity dipole aloft exhibiting barotropic and baroclinic structures in its poleward and equatorward portions respectively in a manner that is dynamically consistent with the observed midtropospheric subsidence their dynamics are also similar to their nh counterpart it is demonstrated through the numerical experiments presented here that each of the sh surface anticyclones observed over the relatively cool eastern oceans can be reproduced as a response to a local near surface cooling heating couplet the cooling is mainly due to radiative cooling associated with low level maritime clouds and the heating to the east is due to sensible heat flux over the dry hea

structure and dynamics of a wave train along the wintertime asian jet and its impact on east asian climate based on observational and reanalysis datasets this study investigates the structure and dynamics of a wave like atmospheric teleconnection pattern along the wintertime asian jet and its influence on east asian climate along the jet the leading empirical orthogonal function eof mode of monthly meridional winds at 250 hpa in winter december january and february is organized as a wave train with maximum anomalies at upper troposphere the wave train propagates northeastward from the north atlantic to europe turns southeastward to the middle east with amplifying amplitude propagates along the jet to south china and reaches japan which is partly induced by sea surface temperature sst anomalies in the equatorial eastern pacific and the north atlantic oscillation over the sector from europe to the middle east the anomalous vortices in the wave train tilt northwestward with height and tilt northeast southwest in horizontal at 250 hpa favoring for extracting available potential energy and kinetic energy from mean flows effectively in addition there exists a positive feedback between transient eddies and the wave train related anomalous circulation over the north atlantic and europe these processes help to maintain and amplify the wave train moreover the wave train can exert significant influences on the wintertime climate in east asia when it is in the phase with a cyclone anticyclone over south china japan rainfall tends to be above normal in south and east china and surface air temperature tends to be above normal around japan and the korea peninsula

relict rock glaciers and protalus lobes in the british isles implications for late pleistocene mountain geomorphology and palaeoclimate many relict rock glaciers and protalus lobes have been described in mountainous areas of the british isles this paper reviews their distribution chronology supposed origin and development and places the research within current investigations and knowledge rock glaciers and protalus lobes are located in a number of different topographic locations and settings they developed at the base of steep cliffs following the catastrophic failure of rock faces at the base of scree slopes following the gradual accumulation of rock debris and in association with glaciers protalus lobes probably developed in response to the permafrost creep of talus material while rock glaciers formed through the deformation and sliding of large bodies of buried ice rock glaciers probably developed or were last active during the younger dryas although the possibility exists that some of these landforms are dimlington stadial in age the development of protalus lobes during the younger dryas suggests that precipitation levels were low and permafrost was widespread during this time the lack of rock glaciers sensu stricto in the british isles compared with other mountain areas is believed to be a consequence of the rock type and relative scarcity of weathered debris for their formation rather than a lack of suitable sites or appropriate environmental conditions copyright 2007 john wiley sons ltd

the influence of aspect and altitude on the size shape and spatial distribution of glacial cirques in the high tatras slovakia poland the shape of glacial cirques is generally considered to result from the combined actions of climate topography and geology the goal of this article was to determine the dependence of cirque morphology on mesoclimatic conditions defined by altitude and aspect in the highest part of the carpathians the high tatras the morphology of each of 116 analyzed cirques was described using a set of 12 morphometric characteristics the relationships between the obtained data were evaluated using simple and multivariate statistical methods the results indicate that cirques in the high tatras are scale specific landforms with allometric development their occurrence increases with altitude but their size decreases the shape of the cirques is determined by altitude only to a small extent with the exception of an increase in the degree of incision with altitude the spatial distribution of cirques is negatively influenced by incoming solar radiation and positively influenced by moisture sources which came mainly from the nw to n during the cold phases of the pleistocene for this reason north facing cirques have proportionally stronger representation and are more incised with steep slopes thus cirques have proportionally stronger representation on the northern slopes and represent more developed glacial erosion landforms than those on the southern slopes although some relationships were detected between cirque morphology and mesoclimatic factors such as altitude and aspect a general discriminant analysis showed that these environmental factors did not explain variations in cirque morphology with sufficient cogency

northern hemisphere winter atmospheric transient eddy heat fluxes and the gulf stream and kuroshio oyashio extension variability abstractspatial and temporal covariability between the atmospheric transient eddy heat fluxes i e t and q in the northern hemisphere winter january march and the paths of the gulf stream gs kuroshio extension ke and oyashio extension oe are examined based on an atmospheric reanalyses and ocean observations for 1979 2009 for the climatological winter mean the northward heat fluxes by the synoptic 2 8 days transient eddies exhibit canonical storm tracks with their maxima collocated with the gs and ke oe the intraseasonal 8 days 3 months counterpart while having overall similar amplitude shows a spatial pattern with more localized maxima near the major orography and blocking regions lateral heat flux divergence by transient eddies as the sum of the two frequency bands exhibits very close coupling with the exact locations of the ocean fronts linear regression is used to examine the lead lag relationship between interannual changes in the northward heat fluxes by the transient

a model study of heat waves over north america meteorological aspects and projections for the twenty first century abstractthe characteristics of summertime heat waves in north america are examined using reanalysis data and simulations by two general circulation models with horizontal resolution of 50 and 200 km several key regions with spatially coherent and high amplitude fluctuations in daily surface air temperature are identified the typical synoptic features accompanying warm episodes in these regions are described the averaged intensity duration and frequency of occurrence of the heat waves in various key regions as simulated in the two models for twentieth century climate are in general agreement with the results based on reanalysis data the impact of climate change on the heat wave characteristics in various key regions is assessed by contrasting model runs based on a scenario for the twenty first century with those for the twentieth century both models indicate considerable increases in the duration and frequency of heat wave episodes and in number of heat wave days per year during the twenty firs

data reduction of laser ablation split stream lass analyses using newly developed features within iolite with applications to lu hf u pb in detrital zircon and sm nd u pb in igneous monazite

observed changes in baroclinic wave activity during the life cycles of low frequency circulation anomalies abstract anomalous baroclinic wave activity during the onset and decay of blocking patterns in the northern hemisphere winter is investigated based upon a 30 year record of 500 mb height and sea level pressure a slowly varying envelope function is defined at each gridpoint in order to represent the modulation of the amplitude of baroclinic wave activity by the low frequency circulation anomalies related to blocking the envelope function fields and the low frequency circulation fields are composited relative to the onset and decay times of four persistent dipole patterns in low frequency circulation anomalies located downstream of the climatological mean stormtracks one polarity of the anomaly patterns corresponds to dipole or modon like blocking patterns over the eastern oceans and the other to strong zonal flow patterns each of the eight composites is comprised of more than 50 persistent blocking or zonal flow episodes the most striking common feature observed during the onset of blocking over th

chronology of the last glacial cycle in the european alps chronological data for glacier advances in the european alps between the last interglacial eemian and the holocene are summarised 115 to 11 ka during this time glaciers were most extensive extending tens of kilometres out onto the forelands between 30 and 18 ka that is synchronous with the global ice volume maximum of marine isotope stage mis 2 evidence for ice expanding to just past the mountain front for an earlier major glacier advance comes from swiss sites where advances have been luminescence dated to mis 5d 100 ka and mis 4 70 ka up to now no such evidence has been found in the eastern alps by 18 ka more than 80 of the late wurmian ice volume had gone subsequently glaciers readvanced reaching into the upper reaches of the main valleys during the lateglacial gschnitz stadial which likely occurred around 17 ka with final moraine stabilisation no later than 15 4 ka the link of the egesen stadial with the younger dryas climate deterioration is supported by exposure ages from four sites as well as minimum limiting radiocarbon dates from bogs within former glacier tongue areas key questions on the spatial and temporal variability of ice extents throughout the last glacial cycle have yet to be answered copyright 2008 john wiley sons ltd

dynamical feedbacks and the persistence of the nao the persistence of the north atlantic oscillation nao is studied using observations of the threedimensional vorticity budget in the atlantic sector analysis of the relative vorticity tendency equation shows that convergence of eddy vorticity flux in the upper troposphere counteracts the effect of anomalous largescale divergence at the upper level at low levels the convergence associated with this large scale vertical circulation cell maintains the relative vorticity anomaly against frictional drag the eddy vorticity flux convergence thus acts to sustain the vorticity anomaly associated with the nao against drag and increases the persistence of the nao vorticity anomaly the adiabatic cooling associated with the rising motion in the vorticity maximum sustains the thermal structure of the nao anomaly enhancing the baroclinicity and thus eddy generation this constitutes a positive eddy feedback that helps maintain the nao the positive eddy feedback occurs only in the midlatitude region and is strongest during the negative phase of the nao when the atlantic jet is displaced toward the equator with a high pressure anomaly to the north and a low pressure anomaly to the south the stronger feedback demonstrated during the negative phase is consistent with the greater persistence observed for this phase of the nao the positive feedback appears to be associated with anomalous northward eddy propagation away from the jet

warm season subseasonal variability and climate extremes in the northern hemisphere the role of stationary rossby waves abstractthis study examines the nature of boreal summer subseasonal atmospheric variability based on the new nasa modern era retrospective analysis for research and applications merra for the period 1979 2010 an analysis of the june july and august subseasonal 250 hpa meridional wind anomalies shows distinct rossby wave like structures that appear to be guided by the mean jets on monthly subseasonal time scales the leading waves the first 10 rotated empirical orthogonal functions reofs of the 250 hpa wind explain about 50 of the northern hemisphere wind variability and account for more than 30 60 of the precipitation surface temperature variability over a number of regions of the northern middle and high latitudes including the u s northern great plains parts of canada europe and russia the first reof in particular consists of a rossby wave that extends across northern eurasia where it is a dominant contributor to monthly surface temperature and precipitation variability and

structure and dynamics of a springtime atmospheric wave train over the north atlantic and eurasia the leading pattern of boreal spring 250 hpa meridional wind anomalies over the north atlantic and mid high latitude eurasia displays an obvious wave train the present study documents the structure energy source relation to the north atlantic sea surface temperature sst and impacts on eurasian climate of this wave train during 1948 2018 this atmospheric wave train has a barotropic vertical structure with five major centers of action lying over subtropics and mid latitudes of the north atlantic northern europe central eurasia and east asia respectively this spring wave train can efficiently extract available potential energy from the basic mean flow the baroclinic energy conversion process and positive interaction between synoptic scale eddies and the mean flow both play important roles in generating and maintaining this wave train the north atlantic horseshoe like nah sst anomaly contributes to the persistence of the wave train via a positive air sea interaction specifically the nah sst anomaly induces a rossby wave type atmospheric response which in turn maintains the nah sst anomaly pattern via modulating surface heat fluxes this spring atmospheric wave train has significant impacts on eurasian surface air temperature sat and rainfall during the positive phase of the wave train pronounced sat warming appears over central eurasia and cooling occurs over west europe and eastern eurasia in addition above normal rainfall appears over most parts of europe and around the lake baikal accompanied by below normal rainfall to east of the caspian sea and over central asia

juvenile crust formation in the zimbabwe craton deduced from the o hf isotopic record of 3 8 3 1 ga detrital zircons hafnium and oxygen isotopic compositions measured in situ on u pb dated zircon from archaean sedimentary successions belonging to the 2 9 2 8 ga belingwean bulawayan groups and previously undated sebakwian group are used to characterize the crustal evolution of the zimbabwe craton prior to 3 0 ga microstructural and compositional criteria were used to minimize effects arising from pb loss due to metamorphic overprinting and interaction with low temperature fluids 207 pb 206 pb age spectra concordance 90 reveal prominent peaks at 3 8 3 6 3 5 and 3 35 ga corresponding to documented geological events both globally and within the zimbabwe craton zircon delta o 18 values from 4 to 10 point to both derivation from magmas in equilibrium with mantle oxygen and the incorporation of material that had previously interacted with water in near surface environments in epsilon hf time space 3 8 3 6 ga grains define an array consistent with reworking of a mafic reservoir 176 lu 177 hf similar to 0 015 that separated from chondritic mantle at similar to 3 9 ga crustal domains formed after 3 6 ga depict a more complex evolution involving contribution from chondritic mantle sources and to a lesser extent reworking of pre existing crust protracted remelting was not accompanied by significant mantle depletion prior to 3 35 ga this implies that early crust production in the zimbabwe craton did not cause complementary enriched and depleted reservoirs that were tapped by later magmas possibly because the volume of crust extracted and stabilised was too small to influence asthenospheric mantle isotopic evolution growth of continental crust through pulsed emplacement of juvenile chondritic mantle derived melts into and onto the existing cratonic nucleus however involved formation of complementary depleted subcontinental lithospheric mantle since the early archaean indicative of strongly coupled evolutionary histories of both reservoirs with limited evidence for recycling and lateral accretion of arc related crustal blocks until 3 35 ga c 2017 elsevier ltd all rights reserved

glaciation in the surroundings of prasilske lake bohemian forest czech republic abstract comprehensive geomorphological and sedimentological analyses confirmed three phases of wurm glaciation in the surroundings of prasilske lake and stara jimka in the bohemian forest sumava mountains glaciations were affected by a steep east facing slope by plateaus on the adjacent ridges and by local geological conditions a small valley glacier about 2 km long and 50 m thick occurred during the first phase in the second phase a glacier rock glacier developed probably based on remnants of the valley glacier during the last phase glacial activity was divided into stara jimka and the stepped cirque of prasilske lake a further shallow 3 m deep lake in stara jimka was dammed by slope movements after deglaciation 14 cal ka bp and survived until 4 cal ka bp the late pleistocene chronology of the bohemian forest seems to be related more closely to the alps than to northern europe in the mid mountains of central europe pleistocene glaciation decreases significantly eastward because of increasing continentality the presence of plateaus deflation areas around 1300 m altitude across the approach of westerly winds was important for the development of glaciers in the bohemian forest the termination of glaciation before the younger dryas is specific to the bohemian forest in comparison with the vosges and krkonose mountains

comparing geophysical methods for talus slope investigations in the turtmann valley swiss alps three geophysical methods ground penetrating radar 2d resistivity and seismic refraction were applied to two landform complexes in a high alpine valley in switzerland to investigate their internal structure results of the different methods were analysed separately before conclusions about sediment thickness and geomorphologic implications were drawn the results from the three methods were compared to focus on the quality of the methods and their field utility with respect to portability of equipment required man power and measurement time in this study ground penetrating radar and seismic refraction proved to be the most suitable with respect to the quality and resolution of the subsurface information and the level of field utility sediment thicknesses of 15 m on a rectilinear slope and more than 30 m on a talus cone have been measured a backweathering rate of approximately 700 mm ka 1 was established furthermore the radar delivered detailed internal sediment structure as well as interfaces between talus and rock glacier the combined geophysical investigation produced a detailed image of the subsurface composition of the two landform complexes that enhance the understanding of the paraglacial landform evolution in this hanging valley

model simulation and projection of european heat waves in present day and future climates abstractthe synoptic behavior of present day heat waves hw over europe is studied using the gfdl high resolution atmospheric model hiram with 50 km grid spacing three regions of enhanced and coherent temperature variability are identified over western russia eastern europe and western europe the simulated hw characteristics are compared with those derived from climate forecast system reanalysis products composite charts for outstanding hw episodes resemble well known recurrent circulation types the hw region is overlain by a prominent upper level anticyclone which blocks the passage of synoptic scale transients the altered eddy vorticity transports in turn reinforce the anticyclone the anticyclone is part of a planetary scale wave train the successive downstream development of this wave train is indicative of rossby wave dispersion additional runs of hiram are conducted for the time slices of 2026 35 and 2086 95 in the climate scenario corresponding to representative concentration pathway

seasonality and interannual variability of the westerly jet in the tibetan plateau region abstract in this study 40 yr ecmwf re analysis era 40 data are used for the description of the seasonal cycle and the interannual variability of the westerly jet in the tibetan plateau region to complement results based on the analysis of monthly mean horizontal wind speeds an occurrence based jet climatology is constructed by identifying the locations of the jet axes at 6 hourly intervals throughout 1958 2001 thus a dataset describing the highly transient and localized features of jet variability is obtained during winter and summer the westerly jet is located respectively to the south and north of the tibetan plateau during the spring and autumn seasons there are jet transitions from south to north and vice versa the median dates for these transitions are 28 april and 12 october the spring transition is associated with large interannual variations while the fall transition occurs more reliably within a 3 week period the strength of the jet exhibits a peculiar seasonal cycle during northw

time variation of 500 mb height fluctuations with long intermediate and short time scales as deduced from lag correlation statistics abstract the time variation of northern hemisphere wintertime 500 mb height fluctuations with short intermediate and long time scales is investigated using lag correlation patterns derived from time filtered data fluctuations with short 2 5 6 day periods time scales propagate eastward at a rate consistent with the notion of a steering level around 700 mb which supports an interpretation in terms of baroclinic waves the mobile teleconnection patterns associated with the intermediate 10 30 day periods time scales exhibit a pattern of time variation suggestive a rossby wave dispersion with a predominance of southward dispersion from middle latitudes into the tropics the geographically fixed teleconnection patterns characteristic of the longer time scales do not show a well defined pattern of time variation but their horizontal structure resembles that of the fastest growing normal mode associated with barotropic instability of the climatological mean wintertime flow

crustal thickening and clay controls on o isotope variation in global magmatism and siliciclastic sedimentary rocks new compilations of global o isotope data from zircon and siliciclastic sedimentary rocks highlight an increasing range in 18o values in both systems since the late archean this is consistent with an increased clay component in sedimentary rocks and subsequent incorporation into igneous rocks each of these factors can arguably be achieved by increased crustal thickening in the late archean resulting in greater burial and melting of supracrustal rocks and increased chemical weathering and recycling of upper crustal rocks despite the suggested change in tectonic regimes in the late archean stochastic modelling in this study demonstrates that 18o data do not provide evidence for a secular decrease in the proportion of mantle derived magmas in granitoid rocks instead best fit models indicate that juvenile input and reworking of supracrustal material vary with respect to the short term 100 200 myr tectonic cycles preserved in the continental crust hence major step changes in global tectonic regimes in the post hadean such as the initiation of subduction in the mid to late archean are not supported by global zircon o isotope datasets and instead minor progressive changes are indicated for earth s tectonic regimes

the response of the pacific storm track and atmospheric circulation to kuroshio extension variability an index of the kuroshio extension front strength is produced using a maximum covariance analysis between sea surface temperature sst and sea surface height ssh gradient observations and composites of the atmospheric state are presented during its positive and negative phases using reanalysis data 1992 2011 it is found that when the kuroshio extension is less more meandering with a stronger weaker sst front the atmospheric heat transport by transient eddies is increased in the western eastern pacific region consistent with an increase decrease in low level baroclinicity analysis of the eddy mean flow interaction shows that this zonal shift in heat transport forces anomalous barotropic flow in the eastern pacific where blocking frequency is strongly influenced the above relationships cannot be reconciled with the known response of the north pacific storm track to remote forcing from the tropical pacific nor can they be explained by the response of the ocean to atmospheric forcing via surface heat fluxes or winds rather the zonal shift in the storm track highlighted here and the associated changes in the large scale circulation are interpreted as a response to the interannual variability of the kuroshio extension front

transient eddy forcing of the time mean flow as identified by geopotential tendencies abstract the forcing of the time mean flow by transient eddies is examined within the framework of a quasi geostrophic equation relating the geopotential tendency to the convergence of transient eddy transports of heat and vorticity the forcing functions of this equation are computed using observed circulation statistics for the wintertime northern hemisphere and solutions are sought for the three dimensional structure of geopotential and temperature tendencies associated with eddies of different time scales in general the geopotential tendencies associated with vorticity fluxes are of the same sign within a given atmospheric column whereas the polarity of the geopotential tendencies associated with heat fluxes in the lower troposphere is opposite to that in the upper troposphere the geostrophic wind tendencies associated with synoptic scale eddies with periods between 2 5 and 6 days are strongest in the vicinity of the oceanic storm tracks the enhanced poleward heat transports by active disturbanc

more intense more frequent and longer lasting heat waves in the 21st century a global coupled climate model shows that there is a distinct geographic pattern to future changes in heat waves model results for areas of europe and north america associated with the severe heat waves in chicago in 1995 and paris in 2003 show that future heat waves in these areas will become more intense more frequent and longer lasting in the second half of the 21st century observations and the model show that present day heat waves over europe and north america coincide with a specific atmospheric circulation pattern that is intensified by ongoing increases in greenhouse gases indicating that it will produce more severe heat waves in those regions in the future

sulfur and oxygen isotope constraints on the sedimentary history of apparent conglomerates from the nuvvuagittuq greenstone belt nunavik quebec abstract mafic igneous rocks of the nuvvuagittuq greenstone belt ngb crystallized before 3 8 ga and possibly as early as 4 3 ga potentially making the belt the oldest known supracrustal sequence on earth however detrital zircons from a rare quartz biotite schist in the ngb yield significantly younger ages of 3 77 ga or less these appear to be inconsistent with the ages of the mafic igneous rocks as the quartz biotite schist has been interpreted as a metaconglomerate formed by the dismantling of preexisting lithologies in order to assess this genetic interpretation we performed a sulfur and oxygen isotope study of the quartz biotite schist sulfide grains found in quartz clasts and the matrix show significant mass independent fractionation of sulfur isotopes 0 2 33s 1 0 mean 33s 0 5 0 1 secondary sulfides from crosscutting veins do not show mass independent fractionation of sulfur isotopes 0 1 33s 0 3 mean 33s 0 1 0 1 oxygen isotope compositions of quartz from clasts matrix and a fine grained lens are highly enriched in 18o 16 9 18o 26 7 non zero 33s values indicate a surficial origin for sulfur probably the eoarchean atmosphere while high 18o values suggest a low temperature 65 18 c origin for the quartz likely as chemical precipitation of a chert precursor from si saturated seawater therefore the coupled s and o isotope measurements show that primary isotopic signatures characteristic of surficial environments survived the protracted metamorphic history of the ngb and suggest that the quartz biotite schist contains material that originated as chemical metasediments the near mono mineralic compositions of the clasts quartz and their shared 18o enrichment suggest that they had a common protolith which was deposited prior to the formation of the schist and subsequently reworked whether the quartz biotite schist represents a metaconglomerate or a structural melange it preserves remnants of some of the oldest chemical sediments on earth

sedimentological investigations in the forefield of an icelandic surge type glacier implications for the surge mechanism abstract a sedimentological study in the forefield of hagafellsjokull vestari iceland has been employed to distinguish between pervasive sediment deformation and sliding as mechanisms of basal motion in surge ice retreat following a surge in 1979 80 has exposed a two layered quasi continuous till cover and a suite of streamlined bedforms including flutes and drumlins an integrated approach using particle size data clast morphology scanning electron microscopy and micromorphology suggests that comminution processes were confined to the uppermost 16 25 cm of the till the lower till layer remained relatively undisturbed during the surge advance in both drumlinised and non drumlinised areas micromorphological evidence of a clay depositing ice sediment water layer suggests that decoupling was important during the surge phase we suggest that the till did not weaken sufficiently for pervasive deformation to occur at depth rather the surge mechanism at hagafellsjokull vestari is thought to involve the transition of the quiescent phase basal water system which consists of a few large subglacial conduits emerging at the ice margin to a distributed or linked cavity system

left hand rule for synoptic eddy feedback on low frequency flow 1 in this study scale interaction between synoptic eddies and low frequency flow is investigated the synoptic eddy feedback is a key process in sustaining the low frequency flow we show clear evidence using ncep reanalysis data that there is a general underlying rule the left hand rule governing the synoptic eddy feedback onto low frequency flow this rule states that eddy vorticity fluxes are directed preferentially about 90 degrees toward their left hand side so that they converge into cyclonic flow and diverge from anticyclonic flow therefore the eddy vorticity flux plays a positive role in reinforcing low frequency flow citation kug j s and f f jin 2009 left hand rule for synoptic eddy feedback on low frequency flow geophys res lett 36 l05709 doi 10 1029 2008gl036435

anatomy of great plains protracted heat waves especially the 1980 u s summer drought abstract the protracted heat wave and drought of the great plains during summer 1980 was a manifestation of an abnormal form of the general circulation an upper level continental high developed rapidly over the southern plains in late may and persisted with only small changes throughout the summer the associated subsidence dry soil lack of cloud and high insolation led to unrelenting heat descriptions of several interlocking features are given followed by an attempt to ascribe the development and maintenance of the drought producing cell to several physical factors strong low latitude westerlies expanded circumpolar vortex over the north pacific north america and north atlantic during spring 1980 led to latitudinally depressed storm tracks relative to normal combined with normal seasonal forcing this anomalous pattern was stable in spring but unstable in summer after the climatologically dependable northward march of the westerlies moreover normal spring to summer mid tropospheric height chang

late pleistocene glaciation of the kleiner arbersee area in the bavarian forest south germany abstract during pleistocene mountain glaciation of the bavarian forest south germany the wurmian kleiner arbersee glacier left behind glacial landforms and sediments which are described classified and interpreted using a combination of geomorphological sedimentological pedological surveying and absolute dating methods the latest kleiner arbersee glacier with a maximum length of 2600 m a minimum width of 800 m and a thickness of 115 m formed an elongated cirque four lateral moraines one divided end moraine one recessional moraine a proglacial lake and a basin in which lake kleiner arbersee was established after deglaciation beyond the glacial limit the landscape is denuded by periglacial slope deposits which are differentiated from the glacigenic sediments based upon clast fabrics clast shapes and sediment consolidation within the glacial limit sandy gravelly to silty gravelly tills are widely distributed whereas glaciolacustrine sediments are restricted to a small area north of the lake small variations in the sand and silt fraction of the tills are explained by melt out processes quartz mica and chlorite derived from gneiss bedrock are dominant in the clay mineral spectrum of tills but also gibbsite as a product of pre pleistocene weathering is present giving evidence of glacially entrained saprolites an irsl date of glaciolacustrine sediments 32 4 9 4 ka bp confirms the wurmian age for the glaciation and radiocarbon ages of the basal sediments 12 3 0 4 and 12 5 0 2 ka bp uncalibrated in the lake kleiner arbersee prove that the basin was ice free before the younger dryas

the shape propagation and mean flow interaction of large scale weather systems abstract for a zonal average operator the eliassen palm flux provides a diagnostic of both eddy behavior and the feedback of the eddies onto the mean flow this paper addresses the diagnosis problem for other averaging operators and in particular for time averaging which has proved in recent years such a powerful means of viewing the three dimensional tropospheric flow the horizontal velocity correlation tensor gives a measure of the characteristic horizontal eddy shape at a point it also implies the direction of the group velocity relative to the mean flow in cases where such a concept is valid however the major emphasis here is on the mean flow feedback of eddies in this respect the eddy vorticity flux is determined by derivatives of the components of the anisotropic part of the tensor making a reasonable approximation allows the eddy vorticity flux convergence to be written in terms of e v 2 u 2 u v a simple interpretation of the mean flow feedback of eddies is then possible a sligh

a comparison of the lichenometric and schmidt hammer dating techniques based on data from the proglacial areas of some icelandic glaciers abstract measurements of rhizocarpon section and schmidt hammer r values are reported from the proglacial geomorphic features on the forelands of the icelandic glaciers of kviarjokull holarjokull and heinabergsjokull oraefi and south vatnajokull sandfellsjokull and oldufellsjokull east m rdalsjokull and bruarjokull eyjabakkajokull and west snaefell north vatnajokull these data are used in reconstructions of patterns of glacier recession since the little ice age maximum and the geomorphic signals of climatic versus non climatic events are discussed age control was obtained from various dated substrates by utilizing historical accounts aerial photographs and grave stones three lichen growth rates are calculated a 0 51 mm a 1 corrected to 0 50 mm a 1 with a colonization lag time of

paleoclimatic implications based on equilibrium line altitude depressions of reconstructed younger dryas and holocene cirque glaciers in inner nordfjord western norway abstract relative to a present cirque glacier in innner nordfjord western norway equilibrium line altitude ela depressions for reconstructed cirque glaciers formed during the younger dryas 11 000 10 000 yr b p the erdalen event 9100 200 yr b p and the little ice age mid 18th century are calculated by the use of accumulation area ratio aar and compared to the corresponding values for plateau glaciers the temperature precipitation ela tp ela as reflected by plateau glaciers gives considerably larger ela depressions than use of the temperature precipitation wind ela tpw ela for cirque glaciers ela depressions during the younger dryas erdalen event and the little ice age thus strongly indicate that cirque glaciers are much more sensitive to changes in winter precipitation than plateau glaciers the difference in ela depressions of contemporaneous plateau and cirque glaciers during the younger dryas erdalen event and the little ice age suggests that winter precipitation was reduced to 59 7 71 6 and 88 7 compared to present values taken into account the reduced winter precipitation the corresponding mean ablation season temperature depressions were probably 4 3 0 3 3 0 0 2 0 3 and 1 4 0 3 0 2 c respectively

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 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 14 c 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 and 2 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

influence of the east asian winter monsoon on the storm track activity over the north pacific 1 we investigate the relationship between the east asian winter monsoon eawm and synoptic eddy activity over the north pacific ocean it is well known that the subtropical pacific jet becomes stronger during strong monsoon periods than during weak monsoons the storm track is generally expected to be active when the eawm is strong owing to the enhanced subtropical jet contrary to this expectation synoptic eddy activity is significantly reduced in strong eawm years and conversely significantly increased during weak years in addition we found that eawm induced lower level cooling brings about the reverse relationship a stronger jet but with weaker storm activities it is suggested that the local baroclinicity induced by the eawm modulates the variation of both the jet and north pacific storm track simultaneously in the interannual time scale because major lower level cooling is located in the western parts of both the subtropical jet and the storm track in longitudes and between the two central axes in latitudes it induces the opposite sign of anomalous local baroclinicity at the two active regions and causes this reverse relationship the wave seeding from east asia to the north pacific storm track is weakened owing to the anomalous lower level cooling in the northwestern pacific which also results in reduction of eddy generation and storm track activities

the largest prehistoric landslide in northwestern slovakia chronological constraints of the kykula long runout landslide and related dammed lakes abstract this study deals with the chronology of the largest long runout landslide in the northwesterrn part of the western flysch carpathians kysucke beskydy mts slovakia despite the impossibility of using direct radiocarbon dating method time constraints for the evolution of the landslide were determined on the basis of the dating of various sedimentological geomorphological elements situated on and adjacent to the landslide body the results show that the landslide evolved between 10 3 and 9 0 ka 14 c bp i e in the wider transitional phase between the late glacial lg and the holocene the main mass movement activity took place at the turn of the younger dryas preboreal chronozones whereas retrogressive activity continued up to the preboreal boreal transition radiocarbon dating together with pollen analysis and sedimentology of landslide dammed palaeolakes and colluvial peat bogs revealed almost continuous holocene palaeogeographical records between 10 3 and 3 3 ka 14 c bp periods of enhanced sediment supply to the reservoirs in 9 9 9 0 8 4 8 2 6 9 6 5 and 4 5 ka 14 c bp correlate well with palaeogeomorphic and palaeohydrological records from nearby polish carpathians the study confirms that the lg holocene transition represented a favourable period for the evolution of large landslides not only in glaciated high mountain areas but also in medium high mountains of central europe

reconstructing the transport history of glacigenic sediments a new approach based on the co variance of clast form indices abstract two indices are used to describe the aggregate shape and roundness characteristics of glacially transported clasts the c40 index the percentage of clasts with c a ratios 0 4 and the ra index the percentage of very angular and angular clasts in a sample analysis of the between and within sample co variance of these indices provides a powerful tool for discriminating actively and passively transported clasts in glacigenic deposits use of these indices is illustrated in an analysis of the form characteristics of clasts from lateral and frontal moraines at storbreen jotunheimen these fall between those of actively transported clasts in basal till low c40 and ra values and those of unmodified frost weathered clasts high c40 and ra values both indices decline down moraine within sample analyses of clast shape demonstrates that these aggregate clast form gradients reflect changes in the relative proportions of actively and passively transported debris on the moraines rather than progressive modification of actively transported clasts these analyses also indicate that actively transported clasts form the dominant component of the moraines particularly near the former glacier terminus further applications of the approach developed here are suggested

dependency of the north pacific winter storm tracks on the zonal distribution of mjo convection 1 we investigate the effects of the tropical madden julian oscillation mjo convection on the zonal location and intensity of storm activity during the boreal cool season nov 1 to feb 28 120 days over the pacific ocean as tropical convection shifts eastward from the eastern indian ocean to the western north pacific mjo induced local hadley circulation leads to an eastward displacement of extratropical rossby wave source rws consequently this influence leads to an eastward shift of the peak area of the storm track the storm track is strongest with the mjo convection over the eastern indian ocean phase 3 and it experiences the suppression when mjo convection is located over the maritime continents phase 4 and it increases again when the mjo propagates to the western pacific phase 5 after which it weakens again phase 6 the intensity of the storm track particularly over the western north pacific 120 e 180 is determined by the integrated effects of three factors the midlatitude convective forcing mcf the jet stream and rws these factors are associated with the locations of mjo convections it is estimated that mjo induced suppression accounts for only 2 5 of the total observed midwinter suppression mws however the pattern generated by the mjo is remarkably similar to the observed meridional displacement of north pacific storm track associated with sub seasonal variation we conclude that the spatial distribution of mjo affects the variation of the pacific storm track but is not a cause of the mws

elementary forms for land surface segmentation the theoretical basis of terrain analysis and geomorphological mapping abstract land surface morphology is fundamental to geomorphological mapping and many gis applications review and comparison of various approaches to segmentation of the land surface reveals common features and permits development of a broad theoretical basis for segmentation and for characterization of segments and their boundaries within the context of defining landform units that maximise internal homogeneity and external differences this paper introduces the concept of elementary forms segments units defined by constant values of fundamental morphometric properties and limited by discontinuities of the properties the basic system of form defining properties represents altitude and its derivatives constant values of which provide elementary forms with various types of homogeneity every geometric type of elementary form can be characterized by a defining function which is a specific case of the general polynomial fitted function various types of boundary discontinuity and their connections and transformations into other types of morphological unit boundaries are analysed the wealth of types of elementary forms and their boundaries is potentially unbounded and thus is sufficient to cover the real variety of landforms elementary forms in the basic set proposed here have clear potential for genetic and dynamic interpretation a brief worked example documents the possibility of analytical computation of various models of ideal elementary forms for particular segments of landform ideal elementary forms can be considered as attractors to which the affinity of surface segments can be measured by multivariate statistical methods the use of the concept of elementary forms in landscape segmentation is promising and it could be adapted for elementary segmentation of various other spatial fields

proterozoic onset of crustal reworking and collisional tectonics reappraisal of the zircon oxygen isotope record a global u pb and 18o zircon database shows temporal changes in the magmatic record related to changes in the degree of crustal reworking the 18o composition of bulk sediment remains relatively constant through geologic time with a mean value of 14 9 in contrast the 18o values in magmatic zircons vary from relatively low values averaging 6 in the archean to increasingly higher and scattered values defining a series of peaks and troughs in post archean data the degree of crustal reworking increases at times of supercontinent assembly therefore we attribute the pattern of post archean 18o values recorded by magmatic zircons to a significant increase in the incorporation of high 18o sediment in response to enhanced crustal thickening and reworking associated with the onset of collisional tectonics especially during formation of supercontinents

multi scale temporal spatial variability of the east asian summer monsoon frontal system observation versus its representation in the gfdl hiram this study examines the representation of the multi scale temporospatial variability of the east asian summer monsoon stationary front msf in the high resolution atmospheric model hiram of the national oceanic and atmospheric administration noaa geophysical fluid dynamics laboratory compared with the observed variability of the msf in the european center for medium range weather forecasts reanalysis interim era interim hiram reproduces reasonably well the seasonal mean precipitation pattern and the seasonal migration of msf however wet biases are found over the northern and eastern china and northern japan and dry biases extend from the southern china to the western north pacific these rainfall biases are directly tied to a northwestward bias in the model simulated seasonal mean location of msf and this location bias is most pronounced in the month of may in general the msf in hiram is more intense located more northwestward and more stationary with weaker interannual variations compared to the observed a pronounced positive bias in the ocean land sea level pressure contrast over east asia largely manifested as the westward expansion of the western north pacific subtropical high is hypothesized to be the main cause of the northwestward location bias of msf in hiram this bias in sea level pressure contrast likely results from the missing of realistic air sea interactions in the hiram simulations

sem analysis of quartz sand grain surface textures indicates alluvial colluvial origin of the quaternary glacial boulder clays at huangshan yellow mountain east central china abstract geomorphic features and pleistocene deposits on huangshan have been attributed to glaciation recent reassessment questions this interpretation as part of the reassessment quartz sand grains from deposits identified as glacial boulder clays till composed of boulders in a clay or silt matrix were analyzed by scanning electron microscope for evidence of their sedimentary history surface textures found on the boulder clay grains were compared with those on grains with known sedimentary histories including glacial grus colluvial and alluvial grains the analysis shows that the grains lack typical glacial textures the surface textures present indicate a complex history nonuniformly weathered grain surfaces point to chemical weathering of the source rock this is supported by the deep weathering of the nonquartz clasts in the sand sized fraction as well as in boulders at the outcrops the close correspondence in surface texture frequencies with those of the alluvial grains indicates an alluvial component to the grains history the similarity with the colluvial grains and the outcrops structures suggest an alluvial colluvial origin for the deposits the history indicated by the surface textures agrees with the recent reassessment of the geomorphic features and points to warm climatic conditions in east central china for at least part of the pleistocene