the role of the barents sea in the arctic climate system present global warming is amplified in the arctic and accompanied by unprecedented sea ice decline located along the main pathway of atlantic water entering the arctic the barents sea is the site of coupled feedback processes that are important for creating variability in the entire arctic air ice ocean system as warm atlantic water flows through the barents sea it loses heat to the arctic atmosphere warm periods like today are associated with high northward heat transport reduced arctic sea ice cover and high surface air temperatures the cooling of the atlantic inflow creates dense water sinking to great depths in the arctic basins and 60 of the arctic ocean carbon uptake is removed from the carbon saturated surface this way recently anomalously large ocean heat transport has reduced sea ice formation in the barents sea during winter the missing barents sea winter ice makes up a large part of observed winter arctic sea ice loss and in 2050 the barents sea is projected to be largely ice free throughout the year with 4 c summer warming in the formerly ice covered areas the heating of the barents atmosphere plays an important role both in arctic amplification and the arctic heat budget the heating also perturbs the large scale circulation through expansion of the siberian high northward with a possible link to recent continental wintertime cooling large air ice ocean variability is evident in proxy records of past climate conditions suggesting that the barents sea has had an important role in northern hemisphere climate for at least the last 2500 years

impact of eastern arctic shelf waters on the nansen basin intermediate layers the eurasian shelves supply water to the nansen basin intermediate layers in two ways as buoyancy driven plumes of dense winter water and as permanent inflow of the barents sea branch of atlantic water while the plumes are local and seasonal phenomena the barents sea flow is part of the large scale circulation both interact with atlantic water which enters the arctic ocean through fram strait and moves as a subsurface boundary current eastward along the continental slope during the polarstern cruise ark ix 4 in summer 1993 the fram strait branch was observed as a narrow core within tens of kilometers of the barents sea shelf edge here several patches of cold low salinity water spread across the slope down to about 500 m depth their origin is assumed to be the northern barents sea they mix with the warm saline fram strait branch water fsbw so that the core properties of the latter become modified downstream in the eastern nansen basin the fram strait branch is displaced toward the inner basin by inflow of the barents sea branch of atlantic water bsbw this inflow appears as a broad 200 km wedge extending from 200 to 1300 m depth bsbw is colder and less saline than water of the fram strait branch and it is less dense and less stratified than the ambient water both branches appear to undergo vigorous mixing while spreading eastward so that any eastward continuation of the boundary flow transports about 50 bsbw and 50 fsbw above 600 m and about 80 bsbw and 20 fsbw below that level toward the canadian basin according to available observations the barents and kara seas are the only source areas for shelf waters ventilating the nansen basin below the halocline and these waters constitute a freshwater input rather than a salt input winter shelf water from the laptev sea cannot contribute to layers deeper than the upper halocline

topographic control of thermohaline frontal structure in the barents sea polar front on the south flank of spitsbergen bank a combination of observations and process oriented numerical modeling is used to investigate the thermohaline structure of the barents sea polar front on the south flank of spitsbergen bank the polar front is the boundary between warm saline north atlantic water and cool fresh arctic water located over the outer edge of the bank observations from the barents sea polar front experiment in august 1992 show that north atlantic water was present in waters of 250 m or deeper with little vertical structure beneath the upper 50 m of the water column the mean velocity field over the south flank of the bank shows a westward flow of roughly 0 1 m s 1 in the north atlantic water and weak mean velocities over the outer edge of the bank a primitive equation model is used with idealized bathymetry to show that the inflow of north atlantic water into the barents sea via the bear island trough bifurcates at the sill between nordkapp bank and sentral bank at the eastern edge of the bear island trough one branch of the north atlantic water recirculates westward out of the barents sea and back into the norwegian sea the flow of north atlantic water is barotropic and linear following the bathymetry the recirculating branch is sheared off at the sill such that the core of recirculating flow is concentrated between the isobath coincident with the sill depth 260 m and the center of the trough 500 m both the cross bank structure of the model thermohaline fields as well as the along bank velocity are very similar to the observations at a depth of 80 m thus the frontal structure is controlled by the interaction of the barotropic inflow with the sill at the eastern edge of the bear island trough and is not controlled by processes occurring over the bank

climate and oceanographic variability in the sw barents sea during the holocene the holocene section of the marine sediment core psh 5159n located in the sw barents sea has been studied at high resolution with a multiproxy approach a well stratified water column occurred at the site 11 9 8 ka bp the stratification was probably a result of a winter sea ice cover and or fresh warm surface waters during summer stratification and resultant reduction in air sea interaction allowed for warmer bottom water temperatures the general situation 11 9 8 ka bp could have been associated with an anomalous high pressure system over the nordic seas and the arctic ocean during the 11 10 5 ka bp interval the polar front was located close to the barents sea margin the polar front moved towards the site from 10 5 ka bp and from 9 8 to 7 5 ka bp it was probably located close to the site at 7 5 ka bp the polar front retreated eastwards as the present day oceanographic pattern established the mid holocene was in general characterized by rather stable conditions in contrast highly variable cond

first results from a pre operational system for automatic detection and recognition of seismic signals associated with avalanches a system for automatic reliable semi instantaneous estimation of avalanche activity is presented in an attempt to check deterministic models and improve the surveillance of risk zones the principle is the seismic detection of avalanches two experimental sites equipped with standard seismological equipment are described avalanche seismic signals are recorded as well as many extraneous signals of natural or human origin after several years of a posteriori identification of the signals we are now able to set up criteria for the automatic recognition of non avalanche signals we have therefore developed an automatic analysis decision system to discriminate betweenn avalanche signals and others this system worked satisfactorily in pre operational conditions during the winter of 1995 96 the results are presented and compared with other data related to avalanche activity although there is still room for improvement our system seems to be able to estimate avalanche activity better than human visual observations

wind driven atlantic water flow as a direct mode for reduced barents sea ice cover abstractvariability in the barents sea ice cover on interannual and longer time scales has previously been shown to be governed by oceanic heat transport based on analysis of observations and results from an ocean circulation model during an event of reduced sea ice cover in the northeastern barents sea in winter 1993 it is shown that the ocean also plays a direct role within seasons positive wind stress curl and associated ekman divergence causes a coherent increase in the atlantic water transport along the negative thermal gradient through the barents sea the immediate response connected to the associated local winds in the northeastern barents sea is a decrease in the sea ice cover due to advection despite a subsequent anomalous ocean to air heat loss on the order of 100 w m 2 due to the open water the increase in the ocean heat content caused by the circulation anomaly reduced refreezing on a time scale of order one month furthermore it is found that coherent ocean heat transport anomalies occ

water mass transformation in the barents sea inferred from radiogenic neodymium isotopes rare earth elements and stable oxygen isotopes abstract nearly half the inflow of warm and saline atlantic water aw to the arctic ocean is substantially cooled and freshened in the barents sea which is therefore considered a key region for water mass transformation in the arctic mediterranean am numerous studies have focused on this transformation and the increasing influence of aw on arctic climate and biodiversity yet geochemical investigations of these processes have been scarce using the first comprehensive data set of the distributions of dissolved radiogenic neodymium nd isotopes expressed as nd rare earth elements ree and stable oxygen isotope 18o compositions from this region we are able to constrain the transport and transformation of aw in the barents sea and to investigate which processes change the chemical composition of the water masses beyond what is expected from circulation and mixing inflowing aw and norwegian coastal water ncw both exhibit distinctly unradiogenic nd signatures of 12 4 and 14 5 respectively whereas cold and dense polar water pw has considerably more radiogenic nd signatures reaching up to 8 1 locally formed barents sea atlantic water bsaw and barents sea arctic atlantic water bsaaw are encountered in the northeastern barents sea and have intermediate nd values resulting from admixture of pw containing small amounts of riverine freshwater from the ob this article is part of a special issue entitled cycles of trace elements and isotopes in the ocean geotraces and beyond edited by tim m conway tristan horner yves plancherel and aridane g gonzalez

interaction of ocean temperature advection surface heat fluxes and sea ice in the marginal ice zone during the north atlantic oscillation in the 1990s a modeling study 1 a moderately fine resolution 0 4 40 vertical levels global coupled ice ocean model was configured and run for 24 years 1979 2002 forced with high frequency national center for environmental prediction national center for atmospheric research ncep ncar atmospheric fluxes the model consists of the los alamos national laboratory parallel ocean program pop and sea ice model cice the fidelity of the simulated mean climatological state and variability of key variables such as ice concentration total ice area ice thickness and drift were compared to observational data sets from satellite and ice drift buoy measurements basin scale changes in the lower atmosphere surface ocean sea ice in the simulated arctic and nordic seas before and after the north atlantic oscillation nao phase switch in 1995 were examined using winter composite analyses over the period 1990 1999 ice cover changes between the two nao phases were consistent with observations in that reduced concentrations were found in the nordic and barents seas and increased values occurred in the labrador sea next we regionally evaluated the relative importance of winter anomalies of upper ocean mixed layer net heat fluxes and of ocean temperature advection on marginal ice zone variability in the irminger greenland and barents seas for this ten year period we found that the net heat flux winter anomaly was at least four times more important than the winter anomaly of ocean temperature advection in the greenland and barents seas while it was twice as important in the irminger sea the ekman ocean temperature advection component generally dominated the geostrophic component in all three regions

sm nd isotopic and geochemical study of the archean tonalite amphibolite association from the eastern indian craton we report the results of a sm nd isotopic major element and rare earth element ree study of the older metamorphic group omg tonalite amphibolite association of the eastern indian craton the older metamorphic tonalite gneisses omtg have been previously dated to be 3 8 ga using sm nd isotope systematies and 3 2 3 4 ga by rb sr and pb pb dating the results of this study indicate that the protoliths of the omg amphibolites are 3 3 ga isochron age 3 30 0 06 ga nd 0 9 0 7 and therefore the omtg which intrude into the associated amphibolites cannot be any older than 3 3 ga the amphibolites display light ree enrichment ce yb n 2 2 6 7 la 30 100 x chondrite and nearly flat heavy ree patterns tb lu n 1 2 1 9 the basaltic parents of the amphibolites were probably generated by the partial melting of a spinel lherzolite mantle strong linear relationships between the amphibolites and tonalites in 147sm 144nd 143nd 144nd space isochron age 3 29 0 04 ga nd 0 8 0 8 imply that they are genetically related the tonalites display fractionated ree patterns la 100 300 x chondrite with moderate heavy ree depletions tb lu n 1 9 3 4 the isotopic major element and ree data are consistent with the derivation of the omtg from partial melting of omg amphibolites or equivalent rocks at amphibolegarnet stabilization depths an initial nd t value of 0 9 0 7 for the amphibolites indicates the presence of a slightly depleted mantle source at 3 3 ga with 147sm 144nd between 0 20 and 0 22 it is suggested that the growth of continental crust in the eastern indian craton occurred in response to magmatic underplating in a plume setting

seasonal variability of atlantic water on the continental slope of the laptev sea during 2002 2004 abstract 2002 04 observations carried out on the laptev sea continental slope as part of the nansen and amundsen basins observational system nabos project are used to study variations of the intermediate 150 800 m atlantic water aw layer of the arctic ocean at the mooring site aw exhibits seasonal changes with higher lower temperature and salinity in winter summer this variability is attributed to the shift of the aw core toward the slope in winter and away from the slope in summer seasonal variation of wind is among the possible factors governing seasonal changes of the aw layer

time slice reconstructions of ocean circulation changes on the continental shelf in the nordic and barents seas during the last 16 000 cal yr b p abstract ocean circulation changes along the continental shelf of the nordic and barents seas have been investigated in order to reconstruct regional changes in the inflow of atlantic water aw through the last 16 000 calibrated cal years yr b p we have selected five time slices representing the late glacial 16 000 15 000 cal yr b p the bolling allerod warm interstadials 14 500 13 500 cal yr b p the younger dryas cold stadial 12 500 11 500 cal yr b p the early holocene 9500 7500 cal yr b p and the late holocene 4000 2000 cal yr b p twelve previously published records of the distribution of benthic foraminifera faunas and ice rafted debris have been compiled the earliest sign of atlantic water inflow was recorded at the northern iceland shelf at 16 000 15 000 cal yr b p the inflow of warm aw to the nordic seas shelf has been persistent since but with variable strength and geographic pattern an apparent zonal seesaw pattern in the strength of the norwegian atlantic current nwac and the irminger current ic during the late glacial bolling allerod and younger dryas periods was found during the holocene no zonal differences in the inflows of nwac and ic were found a strong meridional gradient with warmer conditions at lower latitudes and relatively cold conditions at high northern latitudes existed

arctic ocean circulation processes and water masses a description of observations and ideas with focus on the period prior to the international polar year 2007 2009 abstract the evolving knowledge of the arctic ocean its hydrography and its water masses and their transformations and circulation is reviewed starting with the observations made on fram 1893 1896 and extending to the international polar year ipy 2007 2009 the expeditions and observations after fram to the mid 20th century as well as the more extensive and systematic studies of water masses and circulation made from ice stations and airborne expeditions from the late 1940s to the late 1970s are briefly described the early concepts of the connections and exchanges between the arctic ocean and the world ocean are also discussed in the 1980s scientific icebreakers were beginning to enter the inner parts of the arctic ocean and large international programmes were launched culminating in the ipy the changes in the arctic ocean first noted in the atlantic layer in 1990 and shortly after in the upper layers are described the exchanges between the arctic ocean and the surrounding seas through the four main openings fram strait barents sea bering strait and the canadian arctic archipelago as well the volume and freshwater balances of the arctic ocean are examined

an equivalent barotropic mode in the fine resolution antarctic model abstract both the 6 year time mean flow and the eddy kinetic energy in the fine resolution antarctic model are found to be approximately self similar in the vertical with the velocity showing a rapid decay with depth a simple argument is given as to why this would be expected to occur in this and other numerical models and an analysis is given as to the degree of steering of the mean flow by topography

observations and modeling of dense water cascading from the northwestern laptev sea shelf 1 we examine dense water cascading from the northwestern laptev sea shelf in the arctic ocean this region is believed to be a potential site of dense water formation through ice freezing and brine ejection climate data indicate the presence of saltier denser water on the shelf all year round tongues of dense water spreading from the shelf to the continental slope and reaching a depth of 300 400 m are reported in some historical hydrographic surveys in this study we recreate dense water cascading from the laptev sea shelf by filling a gap between two sequential hydrographic surveys with numerical model output from october 1984 to april 1985 ice formation over the shelf provided salt input almost 5 times greater than the amount that was accumulated in the shelf waters this excessive salt was transported off the shelf mainly by baroclinic eddies and also by mean outflow through the bottom boundary layer shelf origin dense water would have reached at least 1000 m depth but strong stratification prevented it from penetrating deeper than 400 m downslope contribution of mean downslope flow to heat and salt exchange between shelf and slope is on the average 4 times smaller than that caused by eddy fluxes hence although the volume transport associated with cascading is relatively small 0 02 sv heat and salt fluxes are large enough to provide cooling and freshening of atlantic water which propagates along the siberian continental slope

207pb 206pb zircon ages and the evolution of the singhbhum craton eastern india an ion microprobe study1this paper is dedicated to prof a k saha one of the senior co authors who passed away after submission of the paper 1 abstract we used an ion microprobe to measure 207 pb 206 pb ages of single zircons from four key lithologies from the singhbhum craton of eastern india detrital zircons from the oldest recognized sedimentary sequence of the craton the older metamorphic group yielded 3 5 3 6 ga ages indicating that crustal formation had already been initiated by 3 6 ga in this region this data also established an older limit of 3 5 ga for the age of sediment deposition the first appearance of extensive continental crust in the singhbhum region marked by the emplacement of the older metamorphic tonalite gneisses is dated at 3 44 ga our data from both of these units reveal that a 3 2 ga event induced overgrowths within each of these pre existing zircon populations we determine an age of 3328 7 ma for the singhbhum granite phase ii the most widespread of this granite s three phases the emplacement of the two phases of the mayurbhanj granite marking the youngest major episode of acid plutonism in this craton took place in rapid succession at 3 1 ga marking the broad scale stabilization of this terrain

sm nd evidence for 3 3 ga old rocks in rajasthan northwestern india abstract tonalitic to granodioritic gneisses from the basement gneiss of the aravalli region northwestern india define a sm nd isochron corresponding to an age of 3 31 0 07 ga and an initial nd isotopic ratio that is close to chondritic lenticular bodies of mafic amphibolites within the gneisses however define an isochron corresponding to a younger age of 2 83 0 05 ga and small positive initial nd this age is similar to that reported for a large intrusive granite the untala granite in this area and combined with field evidence suggests that mafic volcanism may have been associated with formation of the granite a highly hree enriched garnet separate from one of the tonalitic gneisses defines a two point garnet wholerock isochron age of 2 45 0 02 ga which also is similar to the age of a known thermal event in the region intrusion of the berach and bundelkhand granites at approximately 2 5 ga these results document in broad outline archean crustal formation events in the northwestern segment of the indian subcontinent and demonstrate the need for more detailed studies of the complex terranes mapped by heron 1953 as a single unit the banded gneiss complex

sedimentation pattern and tectonic evolution of the proterozoic singhbhum basin in the eastern indian shield abstract the proterozoic singhbhum basin psb located on the flank of an archaean platform ca 3400 ma is a distinct lithotectonic unit of the singhbhum crustal province of the eastern indian shield the present contribution traces the evolution of this basin filled by volcanics dominated submarine supracrustals and sedimentary formations the proterozoic singhbhum basin has been identified to be a marginal basin evolved in a back arc setting an axial volcanic belt manifesting mor like basaltic eruptions divided the basin into two domains with parallel but distinct sedimentation patterns an asymmetry in sedimentation pattern and source polarity are documented in litho as semblages and ree distribution patterns of cover rocks in the basinal domain flanking the southern platform prevailing tectonics strongly controlled the mechanism of sedimentation which coupled with the volcanic history of the basin indicates its riftogenic character progressive lithospheric stretching successively produced picritic volcanics and mor type basalts along the axial zone of the basin being related to a stretching factor of 2 continental margin rifting ultimately resulted in an oceanic transition as supported also by available geophysical data the evolution of the proterozoic singhbhum basin in its broad perspective was controlled by subduction related processes

monitoring of snow avalanches using a seismic array location speed estimation and relationships to meteorological variables 1 monitoring snow avalanches is necessary in order to better understand their triggering mechanisms and ultimately improve forecast performance seismic monitoring has been developed by several groups over the last 20 years and holds great potential to detect locate and characterize snow avalanches during the 2009 2010 winter a seismic antenna was installed in the french alps close to the village of saint christophe en oisans 1700 m above sea level the array of seven sensors operated during 50 days in october and november 2009 under snow free conditions and during 40 days in january and february 2010 in presence of snow it recorded different types of seismic events including snow avalanches rockfalls shots and regional and local microearthquakes eighty avalanche signals were visually identified using a beam forming method we were able to locate snow avalanches on slopes of various orientations in a radius of about 3 km and track their propagation the location technique allowed for the estimation of avalanches front speed which ranged between 12 and 32 m s 1 the method can also distinguish dry and wet snow avalanches durations of avalanches can be as long as 380 s because of the length of the slopes in the area seismic monitoring provides a catalog of avalanches with precise times which can be used to analyze the impact of meteorological forcings on the avalanche triggering snowfall is found to be the dominant forcing of avalanche activity during this period as revealed by the strongest correlation for the period of study our results suggest that the impact of precipitation on the snowpack instability lasts for about 6 days

the 2 7 2 0 ga volcano sedimentary record of africa india and australia evidence for global and local changes in sea level and continental freeboard abstract the 2 7 2 0 ga volcano sedimentary records of the african indian and australian cratons indicate two broadly defined periods of extensive drowning of the emergent continental areas concomitant with lowered freeboard carbonate banded iron formation bif platforms characterised the first such event at ca 2 6 2 4 ga africa and australia to 2 7 ga india these earlier globally enhanced sea levels are ascribed to increased mid ocean ridge activity possibly related to breakup of a postulated late archaean southern supercontinent alternatively a transition from global scale catastrophic mantle overturn events to the onset of plate tectonics may have occurred in the late archaean nelson 1998 earth planet sci lett 158 109 119 both explanations of increased mid ocean ridge activity are compatible with significant early to middle archaean crustal growth armstrong 1981 phil trans r soc london a 301 443 472 with the emergent high freeboard cratons being subjected to aggressive weathering and erosion enhanced continental crustal growth near the archaean proterozoic boundary mclennan and taylor 1982 j geol 90 347 361 related to the development of significant island arc complexes would have resulted in common lowered freeboard enhanced sea level conditions at the passive margins of the southern cratons the diachronous nature of these earlier transgressions in the various cratons may reflect the effect of local tectonic movements and or the thermal state of the cratons from ca 2 4 2 2 ga cratons that make up the present day continents of india africa and australia had relatively high continental freeboard and lowered sea levels glacigenic deposits are preserved on the kaapvaal africa singhbhum india and pilbara australia cratons the second broadly defined drowning event at ca 2 15 ga was probably due to post glacial climatic amelioration freeboard was reduced by the combination of eustatic rise and the reestablishment of aggressive weathering as warmer palaeoclimates returned in india carbonates were more prominent than the siliciclastic sediments including prominent black shales seen in africa and australia

modeling dynamics and thermodynamics of icebergs in the barents sea from 1987 to 2005 1 a modeling study of iceberg drift characteristics in the barents and kara seas for the period 1987 2005 is presented maps of iceberg density and potential locations subject to grounding complement sparse existing oceanographic and aerial field survey campaigns the model suggests preferential pathways from the most important calving sources icebergs originating from franz josef land have the largest spread over the domain simulations confirm the previously observed seasonal cycle of the southernmost extent of the icebergs strong interannual variability of the iceberg extent with a weak decreasing trend occurs similar to the observed sea ice extent analysis of the atmospheric forcing reveals that years with anomalous northerly winds enhance the southward iceberg extension northerly winds also have a positive delayed impact on the iceberg extent they limit the inflow of atlantic water into the barents sea and therefore its heat content the following year increasing the mean age of icebergs and thus their potential extension finally the model is able to reproduce the observed extreme iceberg extension southeast of the barents sea in may 2003

quantifying the influence of atlantic heat on barents sea ice variability and retreat abstractthe recent arctic winter sea ice retreat is most pronounced in the barents sea using available observations of the atlantic inflow to the barents sea and results from a regional ice ocean model the authors assess and quantify the role of inflowing heat anomalies on sea ice variability the interannual variability and longer term decrease in sea ice area reflect the variability of the atlantic inflow both in observations and model simulations during the last decade 1998 2008 the reduction in annual july june sea ice area was 218 103 km2 or close to 50 this reduction has occurred concurrent with an increase in observed atlantic heat transport due to both strengthening and warming of the inflow modeled interannual variations in sea ice area between 1948 and 2007 are associated with anomalous heat transport r 0 63 with a 70 103 km2 decrease per 10 tw input of heat based on the simulated ocean heat budget it is found that the heat transport into the western barents sea sets the bou

interconnectivity between volume transports through arctic straits arctic heat and freshwater budgets are highly sensitive to volume transports through the arctic subarctic straits here we study the interconnectivity of volume transports through arctic straits in three models two coupled global climate models one with a third degree horizontal ocean resolution higem1 1 and one with a twelfth degree horizontal ocean resolution hadgem3 and one ocean only model with an idealized polar basin tenth degree horizontal resolution the two global climate models indicate that there is a strong anti correlation between the bering strait throughflow and the transport through the nordic seas a second strong anti correlation between the transport through the canadian artic archipelago caa and the nordic seas transport and a third strong anti correlation is found between the fram strait and the barents sea throughflows we find that part of the strait correlations is due to the strait transports being coincidentally driven by large scale atmospheric forcing patterns however there is also a role for fast wave adjustments of some straits flows to perturbations in other straits since atmospheric forcing of individual strait flows alone cannot lead to near mass balance fortuitously every year idealized experiments with an ocean model nemo3 6 that investigate such causal strait relations suggest that perturbations in the bering strait are compensated preferentially in the fram strait due to the narrowness of the western arctic shelf and the deeper depth of the fram strait

impact of north atlantic current changes on the nordic seas and the arctic ocean 1 the impact of north atlantic current nac volume heat and salt transport variability onto the nordic seas and the arctic ocean is investigated using numerical hindcast and sensitivity experiments the ocean sea ice model reproduces observed propagation pathways and speeds of sst anomalies signals reaching the entrance to the nordic seas between iceland and scotland originate partly in the lower latitude north atlantic response experiments with different prescribed conditions at 50 n show that changes in the barotropic flow across 50 n have no impact on the seas north of the greenland scotland ridge because of the strong deformation of the f h field a temperature anomaly inserted in the upper 500 m at 50 n on the other hand has a widespread effect on the temperature distribution and the circulation in the high latitude north atlantic nac induced variability in the nordic seas and locally induced variability have similar magnitude the local atmospheric influence and the complexity of north atlantic nordic seas advection pathways make it unlikely that detection of signal propagation in the nac could lead to a prediction of oceanic conditions in the nordic seas and the arctic ocean with several years lead time

observed atlantification of the barents sea causes the polar front to limit the expansion of winter sea ice abstractbarents sea water bsw is formed from atlantic water that is cooled through atmospheric heat loss and freshened through seasonal sea ice melt in the eastern barents sea the bsw and fresh

the canada basin 1989 1995 upstream events and far field effects of the barents sea 1 the effects of upstream events on southern canada basin waters were examined using physical and geochemical data collected at one location between 1989 and 1995 these events included atlantic layer warming relocation of the atlantic pacific water mass boundary and increased ventilation of boundary current waters early signals of change in the canada basin first appeared in 1993 along the continental margin and by 1995 were evident in the basin interior and farther downstream differences in physical and geochemical properties nutrients oxygen 129i and cfcs were observed between 150 and 1600 m of the water column by 1995 the boundary between pacific and atlantic origin water was shallower and atlantic origin water occupied more of the canada basin water column atlantic origin lower halocline water was colder and more ventilated fram strait branch water was colder fresher and more ventilated and barents sea branch water was warmer fresher more ventilated and occupied a larger volume of the water column than in previous years water mass analysis showed that the composition of atlantic origin water in the canada basin in 1995 included 20 more water from the barents sea two related events upstream appear to be the source of this change an atmospheric regime shift in 1989 that increased cyclonic circulation a transition unprecedented within the latter half of the 20th century in magnitude geographic reach and apparent oceanographic impacts and a large volume of dense water flowed from the barents sea to the arctic ocean between 1988 and 1989 these two phenomena illustrate the close relationship between atmospheric and oceanic events whose combined influence was evident 6 years later and 5100 km downstream in the canada basin at depths 1000 m

dynamically recrystallised quartz c axis fabrics in greenschist facies quartzites singhbhum shear zone and its footwall eastern india influence of high fluid activity abstract oriented specimens of quartz tectonites from the singhbhum shear zone ssz an important tectonic element in the precambrian eastern indian shield and its footwall have been analysed for c axis fabrics of dynamically recrystallised quartz grains in individual specimens the fabric pattern is either an asymmetric type i cross girdle or an asymmetric kinked single girdle irrespective of whether the fabric is from the ssz or its footwall the asymmetry of the fabric confirms a southward thrust movement of the northern block on a northerly dipping shear zone the measured fabrics are characterised by a concentration near the y axis of the finite strain ellipsoid with an equally or subordinately developed concentration near the z axis although some earlier works suggest the y concentration of the quartz c axis fabric as due to the influence of higher temperature obtained in amphibolite facies the occurrence of a similar concentration in the quartz c axis fabric from quartz tectonites of the ssz and its footwall interpreted to have formed under greenschist facies condition is explained by formation of the fabric under high fluid activity during deformation

precambrian continental crust of india and its evolution the indian precambrian continental crust exhibits a variety of geological features fashioned at different times by different geotectonic processes the bulk of this crust was formed prior to 2600 m y ago and remobilized at least twice between 2600 2000 m y ago early proterozoic mobile belt epmb and 2000 1500 m y ago middle proterozoic mobile belt mpmb three early precambrian nucleii karnataka kn jeypore bastar jbn and singhbhum sn appear to have survived in the craton and are characterized by low grade supracrustals and tonalitic trondhjemite gneisses formed 3800 2600 m y ago the epmb event involved sedimentation amphibolite granulite facies metamorphism and co 2 k metasomatism and produced amphibolite facies rocks and k granites in the north and charnockite and other granulite facies rocks in the south gold sporadically distributed in the supracrustal rocks of the craton was remobilized during the epmb event k granites form a garland around the central dharwar craton sugg

seismic and acoustic signatures of surficial mass movements at volcanoes abstract surficial mass movements such as debris avalanches rock falls lahars pyroclastic flows and outburst floods are a dominant hazard at many volcanoes worldwide understanding these processes cataloging their spatio temporal occurrence and detecting tracking and characterizing these events would advance the science of volcano monitoring and help mitigate hazards seismic and acoustic methods show promise for achieving these objectives many surficial mass movements generate observable seismic and acoustic signals and many volcanoes are already monitored significant progress has been made toward understanding modeling and extracting quantitative information from seismic and infrasonic signals generated by surficial mass movements however much work remains in this paper we review the state of the art of the topic covering a range of scales and event types from individual rock falls to sector collapses we consider a full variety of volcanic settings from submarine to subaerial shield volcano to stratovolcano finally we discuss future directions toward operational seismo acoustic monitoring of surficial mass movements at volcanoes

advection in polar and sub polar environments impacts on high latitude marine ecosystems we compare and contrast the ecological impacts of atmospheric and oceanic circulation patterns on polar and sub polar marine ecosystems circulation patterns differ strikingly between the north and south meridional circulation in the north provides connections between the sub arctic and arctic despite the presence of encircling continental landmasses whereas annular circulation patterns in the south tend to isolate antarctic surface waters from those in the north these differences influence fundamental aspects of the polar ecosystems from the amount thickness and duration of sea ice to the types of organisms and the ecology of zooplankton fish seabirds and marine mammals meridional flows in both the north pacific and the north atlantic oceans transport heat nutrients and plankton northward into the chukchi sea the barents sea and the seas off the west coast of greenland in the north atlantic the advected heat warms the waters of the southern barents sea and with advected nutrients and plankton supports immense biomasses of fish seabirds and marine mammals on the pacific side of the arctic cold waters flowing northward across the northern bering and chukchi seas during winter and spring limit the ability of boreal fish species to take advantage of high seasonal production there southward flow of cold arctic waters into sub arctic regions of the north atlantic occurs mainly through fram strait with less through the barents sea and the canadian archipelago in the pacific the transport of arctic waters and plankton southward through bering strait is minimal in the southern ocean the antarctic circumpolar current and its associated fronts are barriers to the southward dispersal of plankton and pelagic fishes from sub antarctic waters with the consequent evolution of antarctic zooplankton and fish species largely occurring in isolation from those to the north the antarctic circumpolar current also disperses biota throughout the southern ocean and as a result the biota tends to be similar within a given broad latitudinal band south of the southern boundary of the acc there is a large scale divergence that brings nutrient rich water to the surface this divergence along with more localized upwelling regions and deep vertical convection in winter generates elevated nutrient levels throughout the antarctic at the end of austral winter however such elevated nutrient levels do not support elevated phytoplankton productivity through the entire southern ocean as iron concentrations are rapidly removed to limiting levels by spring blooms in deep waters however coastal regions with the upward mixing of iron maintain greatly enhanced rates of production especially in coastal polynyas in these coastal areas elevated primary production supports large biomasses of zooplankton fish seabirds and mammals as climate warming affects these advective processes and their heat content there will likely be major changes in the distribution and abundance of polar biota in particular the biota dependent on sea ice

precambrian continental freeboard and geological evolution a time perspective abstract continental crustal growth rates crustal volumes thicknesses and continental freeboard are considered to be intimately related however none are easy to quantify least of all in the precambrian additionally crustal volumes thicknesses and isostasy are related to changing mantle heat and the concomitant variation in thickness of ocean crust another set of variables would be the interaction of plate tectonics and the onset of plate tectonics a contentious issue in itself and mantle plumes superplumes further complication is provided by the ranges of freeboard elevations and eustatic sea level changes overlapping in scale and sharing common genetic causes the constant freeboard model suggests that the net results of the interaction of this complex set of variables has been that continental elevation relative to sea level has remained essentially similar on a global average basis over much of geological time assuming an essentially constant ocean volume since c 3 8 ga application of this model to the precambrian geological record suggests that sigmoidal crustal growth rate models are probably the most reliable a conundrum of the constant freeboard model would be that freeboard would tend to become lowered towards mean sea level for any specific craton over time this freeboard equilibrium would be interrupted for a particular craton by active geodynamic processes resulting from the interplay of plate tectonics and mantle thermal instabilities in this paper we test the validity of this thesis of alternating approximate freeboard equilibrium and active geodynamics by examining the volcano sedimentary record of a number of cratons kaapvaal singhbhum and pilbara for the singhbhum craton and bearing in mind its poor chronological data base freeboard equilibrium appears to have prevailed until c 2 1 ga but for kaapvaal and pilbara until c 1 8 ga the geodynamic processes largely outweighed the tendency towards equilibrium except for c 200 my from c 2 6 to 2 4 ga when global sea level appears to have remained high and transgression was the norm we thus tentatively add the plate tectonic cycle and mantle thermal processes to the already complex association of concepts controlling continental freeboard over time

water mass distribution and polar front structure in the western barents sea the water mass distribution in the western barents sea the thermohaline structure of the western barents sea polar front and the local formation of a dense water mass are described on the basis of an analysis of historical hydrographic data this study concentrated on the frontal region between bjornoya and hopen island where arctic water is found on the spitsbergen bank and atlantic water in the bear island trough and hopen trench the distributions of atlantic and arctic waters in relation to topography were consistent with the hypothesis that the location of the polar front is fixed at about the 250 m isobath by the barotropic circulation of atlantic water within the bear island trough and hopen trench in winter vertical gradients of temperature and salinity were weak throughout the frontal region consistent with a barotropic topographically controlled front in summer vertical gradients remained weak below 100 m depth but increased in the upper layer as a result of the presence of fresh warm surface water produced by melting ice the topographic control of thermohaline properties at the surface was disrupted by the meltwater pool and the meltwater contributed to water mass modification in the frontal region the following seasonal cycle of water mass formation was hypothesized summer heating melts the sea ice on the spitsbergen bank and produces the surface meltwater pool this meltwater not only increases vertical thermohaline gradients on the bank but also crosses the front and freshens the surface layer throughout the western barents sea subsequent winter cooling which creates ice over the bank also forms dense water in the bear island trough and hopen trench by convective mixing of atlantic water and the overlying meltwater

paleoceanographic development in the sw barents sea during the late weichselian early holocene transition abstract the late weichselian early holocene variability of the north atlantic current has been studied with focus on the zonal component of this meridional transport during the transition from glacial to interglacial conditions the investigated sediment core is from 409 m water depth in the sw barents sea eight accelerator mass spectrometry ams 14c dates show that the core covers the last 20 000 cal yr b p with a centennial scale resolution during late weichselian early holocene planktic foraminiferal assemblages were analyzed using the 100 m size fraction and foraminiferal planktic and benthic 13c and 18o isotopes were measured furthermore a range of physical and chemical analyses has been carried out on the bulk sediment samples four time periods have been identified which represent the varying oceanographic conditions in ingoydjupet a glacial trough located off the north coast of norway in the sw barents sea 1 the late glacial before ca 15 000 cal yr b p influenced by the nearby ice sheets with high amounts of sea ice or iceberg transported detritus 2 the late oldest dryas stadial and the bolling allerod interstadial ca 15 000 12 700 cal yr b p with cold surface water conditions influenced by the collapse of the nearby ice sheets high amounts of sea ice or iceberg transported detritus and melt water and weak subsurface inflow of atlantic water 3 the younger dryas cold stadial 12 700 11 650 cal yr b p with low primary productivity and extensive sea ice cover and 4 the preboreal and early holocene 11 650 6800 cal yr b p cal yr b p with strong influx of atlantic water into the area near absence of ice rafted debris and generally ameliorated conditions in both surface and bottom water masses as seen from a high flux of foraminifera and increased marine primary production

recirculation of atlantic water in the western barents sea 1 in this article the atlantic inflow with the north cape current to the barents sea and potential recirculation of this water in the bear island trough is investigated this is resolved by combining continuous current meter and repeated hydrographic section data in the barents sea opening the estimated annual mean net fluxes when excluding the contribution from the norwegian coastal current are 1 1 sv and 39 tw estimated relative to a reference temperature of 0 c the estimated heat flux associated with the outflow in the bear island trough is relatively large 12 tw long term current meter records do not show a close relationship between variations in the inflow and the outflow one year low pass filtered variations in temperature and salinity of the outflowing waters in the bear island trough are positively correlated with variations of the inflowing atlantic water with a lag of about seven months on the basis of a simple mixing model the outflow water consists of about 80 atlantic water that is additionally cooled by 2 0 2 5 c by heat loss to the atmosphere by considering the relative weak mean currents in this region it can be inferred that the fraction of the atlantic water that recirculates follows a relatively short pathway in the bear island trough before returning to the norwegian sea

arctic warming evolution and spreading of the 1990s warm event in the nordic seas and the arctic ocean 1 observations in the arctic ocean revealed changes in oceanic temperature salinity and ice cover of the 1990s as compared with earlier data with a numerical model we favorably reproduce the development and subsequent propagation of temperature anomalies in water of atlantic origin in the 1980s and 1990s these propagated into the arctic ocean via the barents sea and the fram strait two warm anomalies entered the arctic ocean through these passages while the first smaller anomaly only warmed up the western eurasian basin the second large anomaly spread far into the eastern eurasian basin and across the lomonossov ridge into the western arctic basins intensified boundary currents during the high nao state in the first half of the 1990s significantly influenced the amplitude and speed of propagation of the temperature anomalies inside the arctic ocean in contrast to the notion of a continuous warming process during the 1990s our model results suggest the warming of the atlantic layer in the arctic ocean occurred in the form of events the event with the largest anomalous heat input during the modeled period entered the arctic between 1989 and 1994 it is possible to trace back the additional heat input into the arctic to an increased volume inflow via the faroer scotland passage and reduced heat loss to the atmosphere in the early 1990s after a weaker warm inflow in the second half of the 1990s the most recent observations and the model results point to a recurring warm anomaly in the inflow from 1999 onward

skillful prediction of barents sea ice cover a main concern of present climate change is the arctic sea ice cover in wintertime its observed variability is largely carried by the barents sea here we propose and evaluate a simple quantitative and prognostic framework based on first principles and rooted in observations to predict the annual mean barents sea ice cover which variance is carried by the winter ice 96 by using observed ocean heat transport and sea ice area the proposed framework appears skillful and explains 50 of the observed sea ice variance up to 2 years in advance the qualitative prediction of increase versus decrease in ice cover is correct 88 of the time model imperfections can largely be diagnosed from simultaneous meridional winds the framework and skill are supported by a 60 year simulation from a regional ice ocean model we particularly predict that the winter sea ice cover for 2016 will be slightly less than 2015

a review of hadean to neoarchean crust generation in the singhbhum craton india and possible connection with pilbara craton australia the geochronological perspective abstract the precambrian singhbhum craton sc of the eastern india holds a prolonged record of sporadic crust generation and evolution starting from as ancient as the hadean till late archean like every craton episodic nature of crust generation in the sc has been indicated by several workers based on numerous stratigraphic and geochronological evidence long before however it is only in the past decade that a growing zircon u pb hf database has resolved its evolution in detail such as the timing of juvenile crust versus reworking events integration of over a thousand geochronological data n 1558 from hadean 4 ga till the end of archean 2 5 ga exhibits multiple prominent crustal growth peaks during c 3320 ma 3300 ma and 2780 ma combined with moderate peaks at c 3460 ma 3380 ma and 2820 ma integral crust modelling of hf isotopezircon indicates major juvenile crust addition during the periods c 3760 3640 ma 3620 3440 ma while prominent age frequency peak at c 2780 ma defined by u thbaddeyelite ages of regional mafic ultramafic dyke swarm provides a direct proxy of large scale juvenile crust generation the interplay between the growth of new crust and reworking of older crust combined with multiphase deformation and metamorphic events till the end of archean constructed the critical juxtaposition of diverse crustal components of this important craton constraining crust generation and deformation events from an updated geochronological database of this craton reveal remarkable similarity in crustal growth pattern with the archean pilbara craton australia moreover paleomagnetic studies of the neoarchean mafic dyke swarms of both the cratons indicate similar paleo positions therefore compiled field geochronological paleomagnetic parameters invoke the possibility that the archean singhbhum and pilbara cratons might have been connected and shared similar crustal history at least till the neoarchean era

arctic warming through the fram strait oceanic heat transport from 3 years of measurements we present estimates of volume and heat transport through fram strait for the period 1997 to 2000 from data of moored instruments full depth volume transports at 78 55 n were in the order of 10 sv both northwards and southwards with an annual mean net transport between 2 and 4 sv to the south the temperature of the northward flow of atlantic water had a strong seasonality with a minimum in winter nevertheless the northward heat transport was highest in winter caused by the winter maximum of northward volume transport during the three years of observation the heat transport in the west spitsbergen current increased from 28 to 46 tw as a result of both increased speed and temperature in contrast to the west spitsbergen current the volume and heat transport of east greenland current remained fairly constant an integration over a subsection of the east greenland current showed similar values of volume transport to that obtained by measurements in the 1980s foldvik et al 1988 the southward heat transport through modified atlantic water weakened slightly between 1997 and 1999 despite increased temperatures

insights into rock ice avalanche dynamics by combined analysis of seismic recordings and a numerical avalanche model 1 rock ice avalanches larger than 1 106 m3 are high magnitude low frequency events that may occur in all ice covered high mountain areas around the world and can cause extensive damage if they reach populated regions the temporal and spatial evolution of the seismic signature from two events was analyzed and recordings at selected stations were compared to numerical model results of avalanche propagation the first event is a rock ice avalanche from iliamna volcano in alaska which serves as a natural laboratory with simple geometric conditions the second one originated on aoraki mt cook new zealand southern alps and is characterized by a much more complex topography a dynamic numerical model was used to calculate total avalanche momentum total kinetic energy and total frictional work rate among other parameters these three parameters correlate with characteristics of the seismic signature such as duration and signal envelopes while other parameters such as flow depths flow path and deposition geometry are well in agreement with observations the total frictional work rate shows the best correlation with the absolute seismic amplitude suggesting that it may be used as an independent model evaluation criterion and in certain cases as model calibration parameter the good fit is likely because the total frictional work rate represents the avalanche s energy loss rate part of which is captured by the seismometer deviations between corresponding calculated and measured parameters result from site and path effects which affect the recorded seismic signal or indicate deficiencies of the numerical model the seismic recordings contain additional information about when an avalanche reaches changes in topography along the runout path and enable more accurate velocity calculations the new concept of direct comparison of seismic and avalanche modeling data helps to constrain the numerical model input parameters and to improve the understanding of rock ice avalanche dynamics

an observational estimate of volume and freshwater flux leaving the arctic ocean through nares strait abstract the arctic ocean is an important link in the global hydrological cycle storing freshwater and releasing it to the north atlantic ocean in a variable fashion as pack ice and freshened seawater an unknown fraction of this return flow passes through nares strait between northern canada and greenland surveys of ocean current and salinity in nares strait were completed in the summer of 2003 high resolution data acquired by ship based acoustic doppler current profiler and via hydrographic casts revealed subtidal volume and freshwater fluxes of 0 8 0 3 sv and 25 12 msv sv 103 msv 106 m3 s 1 respectively the observations resolved the dominant spatial scale of variability the internal rossby radius of deformation ld 9 km and revealed a complex yet coherent along channel flow with a rossby number of about 0 13 close to geostrophic balance approximately one third of the total volume flux was associated with across channel slope of the sea surface and two thirds 68 with across cha

velocity field of the western entrance to the barents sea 1 by the use of 4 year long records from moored current meters between 71 30 n and 73 30 n of the western entrance to the barents sea the velocity field of the atlantic inflow is examined the mean velocity field shows the atlantic inflow as a wide core that occupies most of this section but the general picture is a velocity field that is dominated by large and frequent fluctuations the key parameter that to a large degree determines the spatial distribution of the velocity field is sea level changes within the section that are induced by the local wind field the main process is the ekman transport through its ability to accumulate water thereby creating strong gradients of barotropic pressure and associated currents southwesterly winds along the norwegian coast and southeasterly winds farther north will in general create wide inflows while northerly winds will result in wide outflows these flow regimes may be persistent for up to 2 3 weeks and are related to the relative strength and lateral extension of the icelandic low and the arctic high although the alignment of the local isobars must be considered in order to be able to describe the details of the flow

changes in ocean temperature in the barents sea in the twenty first century abstractpossible modifications to ocean temperature in the barents sea induced by climate change are explored the simulations were performed with a coupled ice ocean model ciom driven by the surface fields from the canadian regional climate model crcm simulations ciom can capture the observed water volume inflow through the barents sea opening the ciom simulation and observations suggest an increase in the atlantic water volume inflow and heat transport into the barents sea in recent decades resulting from enhanced storm activity while seasonal variations of sea ice and sea surface temperature in ciom simulations are comparable with observations ciom results underestimate the sea surface temperature but overestimate ice cover in the barents sea consistent with an underestimated heat transport through the barents sea opening under the sres a1b scenario the loss of sea ice significantly increases the surface solar radiation and the ocean surface heat loss through turbulent heat fluxes and longwa

seasonal modification of the arctic ocean intermediate water layer off the eastern laptev sea continental shelf break up to 75 of the total variance our data suggest that the entire aw layer down to at least 840 m is affected by seasonal cycling although the strength of the seasonal signal in temperature and salinity reduces from 260 m 0 25c and 0 025 psu to 840 m 0 05c and 0 005 psu the seasonal velocity signal is substantially weaker strongly masked by high frequency variability and lags the thermohaline cycle by 45 75 days we hypothesize that our mooring record shows a time history of the along margin propagation of the aw seasonal signal carried downstream by the aw boundary current our analysis suggests that the seasonal signal in the fram strait branch of aw fsbw at 260 m is predominantly translated from fram strait while the seasonality in the barents sea branch of aw bsbw domain at 840 m is attributed instead to the seasonal signal input from the barents sea however the characteristic signature of the bsbw seasonal dynamics observed through the entire aw layer leads us to speculate that bsbw also plays a role in seasonally modifying the properties of the fsbw

geochemical and petrological evidence for subduction accretion processes in the archean eastern indian craton the composition of sandstones often provides key evidence about the tectonic weathering and transport processes operating on the surface at the time of deposition petrologic and geochemical analyses of little metamorphosed middle late archean sandstones from the eastern indian craton show that the sedimentary rocks were derived from dominantly 3 3 ga old amphibolites of the older metamorphic group omg and tonalites of the older metamorphic tonalite gneisses omtg the two oldest lithologic units of this craton chondrite normalized rare earth element ree patterns of the sandstones show a light ree enriched signature with la sm n varying from 5 2 to 6 7 with no eu anomaly while the heavy rees display flat patterns with gd lu n values of 0 9 1 6 primitive mantle normalized incompatible and compatible trace element plots of these sandstones demonstrate an overall similarity with global proterozoic archean sandstones including strong nb ta negative anomalies in an fsm nd vs ond 0 diagram the sandstones plot precisely between the regional amphibolites and tonalites we infer from the ree abundances and the fsm nd vs ond 0 plot that the sandstones represent a bimodal mechanical mixture of omg and omtg the low ce pb ratios of these rocks of 1 4 indicate a variably pb enriched archean crust and that the ce pb ratio acquired the continental crustal signature distinctly different from those of the bulk silicate earth and mantle values at least as early as mid archean strong nb ta depletion relative to the primitive mantle suggests the sandstones were derived from subduction related magmatic arc sources this latter suggestion is strongly supported by the low nb ta and high zr sm ratios of these sandstones identical to archean tonalite trondhjemites that require based on recent trace element partitioning results their protoliths to have formed by subduction melting of lowmagnesium amphibolites or metamorphosed hydrous basalts 1 2 the average nd model ages of the sandstones are greater than the sm nd crystallization ages of the omg and omtg at v3 3 ga the geochemical data presented here can be collectively interpreted to suggest the presence of subduction accretion processes operational in the midarchean eastern indian craton because the omg and omtg the source rocks of the sandstones formed in a subduction related arc setting the basement rocks upon which this arc was constructed must have been older this observation and the depleted mantle nd model ages tdm of the sandstones ranging from 3 6 to 4 0 ga strongly indicate the presence of continental crust in this eastern indian craton older than 3 3 ga and possibly as old as

width of the north cape current and location of the polar front in the western barents sea 1 earlier results have shown that stronger southwesterly winds give higher temperatures stronger velocities and higher transports in the north cape current ncac in the western barents sea this investigation shows that the wind field causing the stronger southwesterlies also causes a wider ncac i e the ncac becomes warmer and wider at the same time in warm periods the ncac seems to be a two core current system while it has only one wider core in cold periods the reason for the fluctuations in the width of the ncac is a non uniform wind field across the current the varying width of the ncac affects the location of the polar front south of bear island the location of this front is not as stationary as earlier believed and in warm periods with strong wind the front is located further upslope than in cold periods

investigation of the summer kara sea circulation employing a variational data assimilation technique 1 the summer circulations and hydrographic fields of the kara sea are reconstructed for mean positive and negative arctic oscillation regimes employing a variational data assimilation technique which provides the best fit of reconstructed fields to climatological data and satisfies dynamical and kinematic constraints of a quasi stationary primitive equation ocean circulation model the reconstructed circulations agree well with the measurements and are characterized by inflow of 0 63 0 8 0 51 sv through kara gate and 1 18 1 1 1 12 sv between novaya zemlya and franz josef land for mean climatologic conditions positive and negative ao indexes respectively the major regions of water outflow for these regimes are the st anna trough 1 17 1 21 1 34 sv and vilkitsky shokalsky straits 0 52 0 7 0 51 sv the optimized velocity pattern for the mean climatological summer reveals a strong anticyclonic circulation in the central part of the kara sea region of fresh water inflow rofi zone and is confirmed by adcp surveys and laboratory modeling this circulation is well pronounced for both high and low ao phases but in the positive ao phase it is shifted approximately 200 km west relatively to its climatological center during the negative ao phase the rofi locaion is close to its climatological position the results of the variational data assimilation approach were compared with the simulated data from the hamburg shelf ocean model hamsom and naval postgraduate school 18 km resolution nps 18 model to validate these models

2 8 ga old anorogenic granite acid volcanics association from western margin of the singhbhum orissa craton eastern india abstract the tamperkola granite acid volcanics association occurring at the western margin of the archaean singhbhum orissa iron ore craton soc eastern india is intrusive into the darjing group which represents a sequence of mobile belt metasediments in this part of the soc the darjing group rests unconformably on the bonai granite 3 2 ga old absence of any deformational imprints of the country rock metasediments on the tamperkola granite acid volcanics together with its undeformed and unmetamorphosed nature its alkali feldspar dominant mineralogy and its high sio 2 and na 2 o k 2 o and low mgo and cao contents suggest that this granite acid volcanics association is anorogenic in nature two representative samples one each from the granite and the acid volcanics have been dated by in situ 207 pb 206 pb zircon dating method using a small ion microprobe minimum age of crystallisation of the acid volcanics is found to be 2 8 ga strong peak in the 207 pb 206 pb frequency diagram and equality of the observed and expected errors in radiogenic 207 pb 206 pb ratios suggest that this age probably represents the true age of formation of the volcanics the age data place the deposition and metamorphism of the mobile belt metasediments of the darjing group in between 3 2 and 2 8 ga occurrence of 2 9 2 8 ga old small granitoid plutons alkali feldspar granite to syenogranite in composition is also known from the southern margin of the soc therefore it appears that around 2 9 2 8 ga small alkali granite bodies formed at the marginal part of this cratonic block after its stabilisation at 3 1 ga

seismic characterisation of lahars at volcan de colima mexico volcan de colima is one of the most active volcanoes in mexico not only for its eruptive history but also for its annual occurrence of lahars this makes the volcano a natural laboratory for monitoring and studying lahar processes since 2011 monitoring instruments have been deployed along the highly active montegrande ravine with at least three lahar events per year here we report the datasets of three events collected during the 2012 and 2013 seasons then interpret the acquired data an event classification scheme based on lahar magnitude duration and seismic characteristics is presented to distinguish single pulse events spes from multi pulse events mpe spes lasted approximately 60 min had average velocities of 2 m s and mean peak discharges of 24 m3 s mpes endured for more than 3 h reached mean velocities of 4 5 m s and peak discharges of 60 m3 s for block rich surges the seismic signal analysis also allowed us to discriminate physical flow fluctuations within single lahars i e between the arrival of block rich fronts and subsequent variations in flow discharge the exponential regression analysis showed a best fit with correlation coefficients around 0 92 and exponential coefficients of 0 01 s for the block rich fronts with seismic amplitudes increasing from 4 8 10 4 to 2 3 10 3 m s and frequency ranges from 10 to 20 hz the variations in flow discharge were distinguished by lower amplitudes of 5 7 10 4 m s than those of the block rich fronts and with frequency ranges of 10 40 hz the results presented in this paper demonstrate that the seismic data of events allowed us to describe and discriminate among different flow types these records are thus a useful investigation tool for lahar events that have a seismic record but are not observed directly we propose that a seismic early warning system can be developed to help civil protection authorities in designing risk mitigation strategies

the archaean nucleus of singhbhum the present state of knowledge abstract the supracrustal rocks of the older metamorphic group omg consisting of metasediments and ortho amphibolite constitute the oldest unit in the archaean nucleus of singhbhum however there are indications that still older 3 4 3 8 ga crust of both sialic and mafic composition existed in this region the omg ortho amphibolites were formed by partial melting of mantle with near chondritic composition ca 3 3 ga ago probably as a result of plume activity shortly afterwards partial melting of the underplated mafic material produced a tonalitic melt older metamorphic tonalitic gneiss omtg which intruded the omg supracrustals and the entire suite was deformed and metamorphosed to upper amphibolite facies subsequent to this melting of the omg ortho amphibolites and the lower crustal material of probable andesitic composition produced melts varying in composition from tonalite to granite and these intruded in different phases to produce plutons of singhbhum granite bonai granite and kaptipada granite which together form volumetrically the major part of the archaean nucleus the older omg and omtg occur as enclaves within these younger granitoids the time difference between the emplacements of the omtg and the early phases of younger granitic intrusion was of the order of 100 200 ma thus serial additions of juvenile material led to the formation of a stable microcontinent by 3 2 ga thermally triggered stretching in this microcontinent produced basins peripheral to the present day singhbhum granite pluton and in these basins the younger supracrustal rocks of the iron ore group iog consisting of bif associated argillaceous and subordinate arenaceous rocks and mafic lavas were laid down there is inadequate field or geochronological evidence to resolve the issue of whether the different iron ore basins were coeval or not meagre geochronological data suggest that some of the bifs are older than ca 3 1 ga post iog activity is confined to the intrusion of mafic dyke swarms and formation of intracratonic basins the ages of both being uncertain

atmospheric influence on arctic marginal ice zone position and width in the atlantic sector february april 1979 2010 arctic marginal ice zone miz widths in the atlantic sector were measured during the months of maximum sea ice extent february april for years 1979 2010 using a novel method based on objective curves through idealized sea ice concentration fields that satisfied laplace s equation over the record the labrador sea miz mizl had an average width of 122 km and narrowed by 28 while moving 254 km poleward the greenland sea miz mizg had an average width of 98 km and narrowed by 43 while moving 158 km west toward the greenland coast and the barents sea miz mizb had an average width of 136 km and moved 259 km east toward the eurasian coast without a trend in width trends in miz position and width were consistent with a warming arctic and decreasing sea ice concentrations over the record beyond the trends nao like atmospheric patterns influenced interannual variability in miz position and width mizl widened and moved southeast under anomalously strong northerly flow conducive to advection of sea ice into the labrador sea mizg widened and moved northeast under anomalously weak northerly flow conducive to diminishing the westward component of sea ice drift and mizb widened and moved poleward at the expense of pack ice under anomalously strong southwesterly flow conducive to enhancing oceanic heat flux into the barents sea in addition meridional flow anomalies associated with the nao per se moved mizb east and west by modulating sea ice concentration over the barents sea

age of the baula pge mineralization orissa india and its implications concerning the singhbhum archaean nucleus abstract two types of platinum group element pge mineralization are identified in the mafic facies of the baula complex intruding the gabbro anorthosite unit of the singhbhum archaean nucleus the first pt dominated is magmatic the pgm are included in the magmatic silicates of a gabbro norite intrusion the bangur gabbro cutting the complex s ultramafic facies and are found preferentially where the gabbro incorporates clasts of dunite and chromitite near the gabbro ultramafics contact the second pd dominated is hydrothermal the pgm are associated with hydrous silicates located in the gabbro matrix of a magmatic breccia in which the blocks are from the baula ultramafic facies the originating fluids for the second type of mineralization were exsolved from the magma and concentrated pge and volatile elements we see no evidence of remobilization or external fluid contamination a structural study has demonstrated that a the breccia was provoked by the intrusion of the upper part of the bangur gabbro and b the breccia matrix corresponds to the bangur gabbro consequently both types of pge mineralization are associated with the same magmatic event a zircon age of 3122 5 ma has been obtained for the main bangur gabbro intrusion and similar ages 3123 7 and 3119 6 ma have been obtained on the pge mineralized gabbro matrix of the breccia this supports the hypothesis of a genetic link between the bangur gabbro with its pt dominated pge and the breccia with its pd dominated pge giving a mean weighted age of 3121 3 ma for the mineralization sm nd data on eight gabbro samples of the baula complex yielded a similar age of 3205 280 ma the dating of these events places them close to the broad scale stabilization of the singhbhum archaean nucleus estimated at 3 1 ga and defines one of the oldest pge mineralizing events ever recorded the bangur gabbro shows many affinities with the gabbro anorthosite unit of the singhbhum archaean nucleus in terms of age of emplacement and isotopic composition it may be therefore that the bangur gabbro actually forms part of the gabbro anorthosite unit and that a fundamental control of its two types of pge mineralization is the presence of ultramafic clasts

atlantic water circulation over the mendeleev ridge and chukchi borderland from thermohaline intrusions and water mass properties 1 hydrographic and tracer data from 2002 illustrate atlantic water pathways and variability in the mendeleev ridge and chukchi borderland cblmr region of the arctic ocean thermohaline double diffusive intrusions zigzags dominate both the fram strait fsbw and barents sea branch waters bsbw in the region we show that details of the zigzags temperature salinity structure partially describe the water masses forming the intrusions furthermore as confirmed by chemical tracers the zigzags peaks contain the least altered water allowing assessment of the temporal history of the atlantic waters whilst the fsbw shows the 1990s warming and then a slight cooling the bsbw has continuously cooled and freshened over a similar time period the newest boundary current waters are found west of the mendeleev ridge in 2002 additionally we show the zigzag structures can fingerprint various water masses including the boundary current using this tracer data and the advection of the 1990s warming we conclude the strongly topographically steered boundary current order 50 km wide and found between the 1500 m and 2500 m isobaths crosses the mendeleev ridge north of 80 n loops south around the chukchi abyssal plain and north around the chukchi rise with the 1990s warming having reached the northern but not the southern northwind ridge by 2002 pacific waters influence the atlantic layers near the shelf and over the chukchi rise the northwind abyssal plain is comparatively stagnant being ventilated only slowly from the north there is no evidence of significant boundary current flow through the chukchi gap

absolute flow field estimation for the nordic seas from combined gravimetric altimetric and in situ data 1 in the nordic seas we combine a computation of absolute surface current flow derived from geodetic data with in situ historical hydrographic data to estimate the absolute volume heat and salt transports as a function of depth our mean dynamic topography mdt is calculated from marine airborne and satellite gravimetry combined with satellite altimetry using a new algorithm called the iterative combination method icm residual noise in the gravimetric geoid is the limit on mdt resolution and is suppressed using a gaussian filter with a width at half peak amplitude of 59 km detailed and coherent flow paths for surface geostrophic currents are clearly identified icm mdt was used as fixed boundary condition to transform historical hydrography into absolute estimates of volume heat and salt transport replacing the assumption of an isobaric surface at a predetermined depth for the inflow of atlantic water potential temperature 6 c through the faroe shetland channel into the nordic seas we obtain time averaged fluxes between 1993 and 1996 of 3 5 sv volume 121 tw heat and 124 106 kg s 1 salt very close to reported observations from acoustic doppler current profiler moorings and conductivity temperature depth data for the svinoy section we obtain a northward transport of atlantic water s 35 0 t 5 0 c of 3 9 sv in the eastern branch of the norwegian atlantic current comparable with reported measurements of 4 2 sv similarly good agreement is found for the hornbanki and iceland faroe ridge sections and for monitoring atlantic water outflow across the barents sea opening to the arctic shelf

the structural and geochemical evolution of the singhbhum granite batholithic complex india abstract the singhbhum granite batholithic complex of eastern india is composed mainly of a the older metamorphic group tonalite trondhjemite gneiss omtg 3800 ma old whch intruded synkinematically into the enveloping older metamorphic group omg 3800 ma old and b the singhbhum granite sbg consisting of three distinct but closely related phases of at least twelve separate magmatic units of granodiorite granite 2950 ma old and a number of patches of granitised omg orthoamphibolites geochemical studies including ree and lil elements suggest that a the omg orthoamphibolites were derived either by re melting of a k poor basalt lkt or of mantle peridotite with high concentration of lil elements b the omg tonalite was derived by partial melting of amphibolite and c the singhbhum granite magmas appear to have formed in two distinct modes i partial melting of amphibolite for the magmas of phases i and ii and ii partial melting of a siliceous garnet bearing granulite for magmas of the phase iii units

petrochemistry of the lavas from proterozoic dalma volcanic belt singhbhum eastern india the dalma volcanic belt of the singhbhum precambrian terrain in eastern india is developed along the median zone of a linear basin flanked by archaean cratonic basement to the south the lavas in a low grade metamorphic environment preserve a strong compositional bimodality with highly magnesian picritic volcanics developed at the base and low k basalt flows above constituting the bulk of the lava pile the ultrabasic lavas have low concentrations of immobile incompatible elements ratios of which are probably controlled by the source character dalma mafic flows are closely comparable in geochemical character to modern day mid oceanic ridge basalts morb with a dominance of light ree depleted basalts and ferrobasalts however in terms of certain element ratios th ta deviation from morb characteristics toward island arc tholeiites is apparent in this respect the dalma basalts appear to have a modified morb composition and the closest chemical analogy may be basalts from back arc basins i e a supra subduction zone environment the bimodality of ultrabasic and mafic lavas is reminiscent of archaean komatiitic provinces the geochemical signature of the dalma lavas and the geological framework of the terrain strongly point to a marginal basin domain developed in this crustal segment during the proterozoic

spatio temporal patterns in lateglacial and holocene vegetation and climate of finnmark northernmost europe precisely dated records of palaeovegetation and reconstructed palaeoclimate are presented from three lakes in northernmost finnmark the lakes lie adjacent to the southern shore of the barents sea and are located along a west east transect the three records are used to reconstruct spatial patterns in regional vegetation and climatic history since 13 900 cal yr bp longer term shifts in treeline position and in the position of the pinus betula ecotone are recorded in addition especially during the regional holocene thermal maximum the latter exhibited strong periodic fluctuations the number and strength of these fluctuations that were recorded at each of the three sites differed systematically with fewer and weaker fluctuations seen at the easternmost site in particular the patterns revealed are used to test the hypothesis that variations in the strength of the north cape current have been of primary importance as the proximal driver of climatic variability in the region since deglaciation the results provide strong support for this hypothesis during the holocene the strong periodic fluctuations during the regional holocene thermal maximum in particular being consistent with the proposed mechanism during the lateglacial and earliest holocene the patterns are less clear but nonetheless also consistent with the proposed mechanism further work on precisely dated marine sediment cores will be necessary to understand the factors leading to the periodic and longer term variations in strength of the north cape current

seasonal sea ice cover during the warm pliocene evidence from the iceland sea odp site 907 abstract sea ice is a critical component in the arctic and global climate system yet little is known about its extent and variability during past warm intervals such as the pliocene 5 33 2 58 ma here we present the first multi proxy ip25 sterols alkenones palynology sea ice reconstructions for the late pliocene iceland sea odp site 907 our interpretation of a seasonal sea ice cover with occasional ice free intervals between 3 50 3 00 ma is supported by reconstructed alkenone based summer sea surface temperatures as evidenced from brassicasterol and dinosterol primary productivity was low between 3 50 and 3 00 ma and the site experienced generally oligotrophic conditions the east greenland current and east icelandic current may have transported sea ice into the iceland sea and or brought cooler and fresher waters favoring local sea ice formation between 3 00 and 2 40 ma the iceland sea is mainly sea ice free but seasonal sea ice occurred between 2 81 and 2 74 ma sea ice extending into the iceland sea at this time may have acted as a positive feedback for the build up of the greenland ice sheet gis which underwent a major expansion 2 75 ma thereafter most likely a stable sea ice edge developed close to greenland possibly changing together with the expansion and retreat of the gis and affecting the productivity in the iceland sea

an assessment of biomarker based multivariate classification methods versus the pip25 index for paleo arctic sea ice reconstruction abstract the development of various combinative methods for arctic sea ice reconstruction using the sympagic highly branched isoprenoid hbi ip25 in conjunction with pelagic biomarkers has often facilitated more detailed descriptions of sea ice conditions than using ip25 alone here we investigated the application of the phytoplankton ip25 index pip25 and a recently proposed classification tree ct model for describing temporal shifts in sea ice conditions to assess the consistency of both methods based on biomarker data from three downcore records from the barents sea spanning millennial timescales we showcase apparent and potential limitations in both approaches and provide recommendations for their identification or prevention both methods provided generally consistent outcomes and within the studied cores captured abrupt shifts in sea ice regimes such as those evident during the younger dryas as well as more gradual trends in sea ice conditions during the holocene the most significant discrepancies occurred during periods of highly unstable climate change such as those characteristic of the younger dryas holocene transition such intervals of increased discrepancy were identifiable by significant changes of hbi distributions and correlations to values not observed in proximal surface sediments we suggest that periods of highly fluctuating climate that are not represented in modern settings may hinder the performance and complementary application of pip25 and ct based methods and that data visualisation techniques should be employed to identify such occurrences in downcore records additionally due to the reliance of both methods on biomarker distributions we emphasise the importance of accurate and consistent biomarker quantification

forcing of oceanic heat anomalies by air sea interactions in the nordic seas area 1 hydrographic data and atmospheric reanalysis from 1982 to 2005 are used to show a strong link of the atlantic water temperature awt anomalies observed in the transition zone between the norwegian atlantic current and the west spitsbergen current in summer to the surface heat flux shf anomalies observed over the barents sea open water in the preceding late winter a mechanism proposed for this link is formation of ocean temperature anomalies in a deep mixed layer and their subsequent westward export by a branch of atlantic water recirculating in the western barents sea the shf anomalies over the barents sea are due to advection of temperature and humidity by anomalous winds across the arctic ice edge and do not strongly depend on the north atlantic oscillation nao correlations of up to about 0 9 between the awt anomalies and indices of atmospheric variability over the barents sea open prospects for seasonal awt predictability it is also shown that the wind forcing responsible for positive awt anomalies is involved in a cyclonic perturbation of the atmospheric circulation over the nordic seas this perturbation generates through influence on the sea ice distribution a lobe of shf anomalies in the marginal ice zone miz on the eastern barents sea and western greenland sea sides of the nordic seas which has the opposite sign to the open water lobe in contrast to the barents sea miz the diabatic heating of the atmosphere by upward shf anomalies in the greenland sea miz competes with cold advection

eastern indian 3800 million year old crust and early mantle differentiation samarium neodymium data for nine granitic and tonalite gneisses occurring as remnants within the singhbhum granite batholith in eastern india define an isochron of age 3775 89 x 10 6 years with an initial 143 nd 144 nd ratio of 0 50798 0 00007 this age contrasts with the rubidium strontium age of 3200 x 10 6 years for the same suite of rocks on the basis of the new samarium neodynium data field data and petrologic data a scheme of evolution is proposed for the archean crust in eastern india the isotopic data provide evidence that parts of the earth s mantle were already differentiated with respect to the chondritic samarium neodymium ratio 3800 x l0 6 years ago