volcaniclastic rocks and volcaniclastic facies in the middle precambrian aphebian belcher group northwest territories canada the middle precambrian flaherty formation consists of a thick sequence of volcanic rocks of both effusive and explosive origin derived from a source area west of the belcher islands the effusive

late quaternary paleoceanographic changes in the southwestern okhotsk sea evidence from geochemical radiolarian and diatom records abstract high resolution analyses of geochemical parameters biogenic opal calcium carbonate organic carbon and nitrogen and microfossil assemblages diatoms and radiolarians on core md01 2412 clarified detailed paleoceanographic changes such as sea ice cover and biological production in the southwestern okhotsk sea during the last 115 kyr an age model of core md01 2412 was established based on 18o stratigraphy accelerator mass spectrometer ams 14c and tephrochronology sea ice history reconstructed by siliceous microplankton records indicated that the present sea ice condition was formed during the last 8 kyr only during marine isotope stage mis 2 was the duration of sea ice cover in this region much longer than that of today 4 5 months a year two diatom species thalassionema nitzschioides and fragilariopsis doliolus revealed that the soya warm current water swcw flowed into the okhotsk sea near the site of core md01 2412 during the last 12 14 kyr and during mis 5a and was associated with sea level rise biological productivity rapidly increased during mis 1 associated with sea ice retreat two major increases of organic carbon oc contents wt and corg n ratios were observed and the timings of these events were 15 8 16 7 ka event 1 and 13 1 13 6 ka event 2 corresponding to these events the abundance of cycladophora davisiana an intermediate water dwelling radiolarian species increased this high c davisiana abundance can be correlated to the input of terrestrial organic matter from the submerged shelf to the intermediate water apart from the radiolarians the production of diatoms in the surface waters was suppressed by the development of well stratified surface water along with sea ice melting during the early holocene diatom production increased gradually during the last 10 kyr with enhanced vertical mixing

sea surface temperature and salinity changes near the soya strait during the last 19 ka past sea surface temperature sst and salinity sss changes in the northeastern east sea japan sea since 19 cal ka bp have been reconstructed by using an alkenone unsaturation index and the oxygen isotope ratio of planktonic foraminifera neogloboquadrina pachyderma s in core mr0604 pc03b coretop alkenone temperature and calcification temperature correspond to the temperature of seawater in summer and spring at the depth of 10 30 m respectively based on the records from this core and previous studies spatio temporal changes in alkenone temperature of the east sea japan sea have been reconstructed to investigate changes of surface circulations and the subpolar front spf position during the transitional period from the glacial to the holocene the sst was lower about 2 3 c than that of today and the sss dramatically increased at that time in the entire east sea japan sea but it was still lower than that of today however the northern sss was higher than that of the southern part the source of the cold and saline seawater could have been the oyashio current oy inflow from the north not the tsushima warm current twc inflow from the south probably sea level rose rapidly at that time there might be no strong development of the spf during the transitional period due to the restricted inflow of the twc during the early holocene the sst and sss of the east sea japan sea increased compared to the transitional period due to increased seawater exchange through straits the spf was tilted orienting from southwest to northeast because the inflow of the twc was not fully developed due to lower sea level subsequently the surface condition of the east sea japan sea was similar to that of today at 6 cal ka bp the forerunner of soya warm water fsww that flowed out through the soya strait in early spring did not affect the formation of the okhotsk sea intermediate water and the north pacific intermediate water during the glacial and interglacial periods

formation of 26 8 26 9 σθ water in the kuril basin of the sea of okhotsk as a possible origin of north pacific intermediate water by using all japanese hydrographic data obtained south of 55 n in latitude in the sea of okhotsk we compile a data set for this study our investigations with these data show that a large quantity of relatively cold fresh oxygen rich homogeneous intermediate water with a density range of 26 8 to 26 9 exists in the kuril basin we name this intermediate water the kuril basin intermediate water kbiw results of isosteric analyses show that a possible origin of kbiw is located in a region off the hokkaido coast in the southwestern sea of okhotsk we suggest that kbiw is produced by the isopycnal mixing of relatively dense soya warm water which appears only in early spring with the colder fresher water which originates from the northwestern okhotsk finally we demonstrate that kbiw may be a source water of the north pacific intermediate water npiw because it has the same density range and water properties

gravity anomalies and deep structure of eastern hudson bay abstract the cape smith and belcher foldbelts of lower proterozoic aphebian rocks form parts of the proposed circum superior suture which separates the superior and churchill structural provinces of the canadian shield recent marine gravity surveys in eastern hudson bay 1976 1979 show that the distinctive linear gravity pattern of paired positive and negative anomalies along the cape smith foldbelt of northern ungava extends southwards into hudson bay to the belcher islands interpretation of five gravity profiles across the cape smith and belcher foldbelts suggests that the churchill crust is thicker and denser than the superior the boundary between the two contrasting crustal blocks is interpreted as a collisional suture the rocks of the foldbelts which are progressively more volcanic northwards are the source of a residual positive anomaly associated with the cape smith foldbelt and a series of discontinuous positive residual anomalies in the bay to the north the thicknesses of the foldbelt rocks are estimated to be between 4 and 9 km with a local maximum of 13 km in the northernmost profile to the south in the belcher islands where geological estimates of formation thickness and measured rock densities provide more constraints on the interpretation of the residual anomalies the foldbelt rocks are generally 6 7 km thick with a local maximum thickness of about 9 km one possible interpretation of paleomagnetic results for belcher islands rocks in terms of a two plate model lends support to the collision hypothesis

proterozoic continental volcanism in the belcher islands implications for the evolution of the circum ungava fold belt the belcher islands of eastern hudson bay expose a continuous sequence of early proterozoic volcanics and continental and shallow marine sedimentary rocks the volcanic rocks comprise two sequences of continental basalts the older eskimo formation and the younger flaherty formation the flows of both formations are composed of tholeiitic basalts mgo 9 wt which in each formation are divided into two groups based on the concentrations of high field strength elements both groups of eskimo flows have fractionated rare earth element ree patterns with negative nb anomalies relative to eskimo flows the flaherty flows have flatter ree profiles and higher nb contents the chemical variations observed in the eskimo flows are consistent with an assimilation fractional crystallization process involving a lower continental crust contaminant the major and most trace element trends of the flaherty flows are attributed to gabbroic crystal fractionation of two parental liquids which are interpreted to

freshening and dense shelf water reduction in the okhotsk sea linked with sea ice decline abstract a recently constructed hydrographic dataset from the okhotsk sea reveals a prominent freshening to depths of 500 m during the past four decades with the maximum in the northwestern part of the sea averaged over the sea this freshening corresponds to an input of 0 55 m of freshwater this leads to a decrease in density of the intermediate water and deepening of the isopycnals with the maximum deepening at 26 8 of 60 m averaged over the sea the intermediate water is significantly warmed along the pathway of dense shelf water dsw a simple box model shows that dsw production has decreased by 30 during the past four decades we propose that the freshening and dsw reduction are caused by the weakening of salt freshwater redistribution through sea ice decline as well as by the increase of excess precipitation over evaporation since the overturning in the north pacific originates from the okhotsk sea through the dsw these changes possibly weaken the shallow overturning of the north pacific

tides in the sea of okhotsk eight major tidal constituents in the sea of okhotsk have been investigated using a numerical solution of tidal equations on a 59 space grid the tides are dominated by the diurnal constituents diurnal tidal currents are enhanced in shelikhov bay and penzhinskaya guba at kashevarov bank in proximity to the kuril islands and at a few smaller locations the major energy sink for diurnal tides over 60 of the total energy is shelikhov bay and penzhinskaya guba the major portion of semidiurnal tide energy is dissipated in the northwestern region of the sea of okhotsk and in shelikhov bay and penzhinskaya guba nonlinear interactions of diurnal currents are investigated through k1 and o1 constituent behavior over kashevarov bank these interactions generate residual circulation of the order of 10 cm s 21 major oscillations at semidiurnal and fortnightly periods 13 66 days and higher harmonics of basic tidal periods the m2 tidal current caused by the nonlinear interaction of the diurnal constituents over kashevarov bank constitutes approximately a half of the total m2 tide current there the fortnightly current through nonlinear interactions also influences basic diurnal tidal currents by inducing fortnightly variations in the amplitude of these currents

freshwater impacts recorded in tetraunsaturated alkenones and alkenone sea surface temperatures from the okhotsk sea across millennial scale cycles 1 we present records of phytoplankton produced alkenones down a long piston core which reveal changes of sea surface temperature sst and sea surface salinity sss in the southwestern okhotsk sea over the past 120 ka between 20 and 60 ka b p alkenone derived temperatures typically increased by 6 c 8 c from periods corresponding within a few hundred years to stadials to those corresponding to interstadials recorded in greenland ice cores the abundance of c37 4 alkenone relative to total c37 alkenones percent c37 4 a possible proxy for salinity indicated that during most low sss was associated with high sst the warm freshwater events might be related to 1 a decline in the supply of saline water entering the okhotsk sea through the soya strait 2 strengthening of the freshwater supply from the amur river and precipitation over the okhotsk sea associated mainly with increased asian summer monsoon activity and 3 the effect of melting sea ice these findings increase our understanding of the close linkage between high and low latitudes in relation to climate change and the synchronicity of climate changes within a few centuries between the pacific and the atlantic sides of the northern hemisphere

assessment of the effects of tidal mixing in the kuril straits on the formation of the north pacific intermediate water abstract to assess accurately the effect of tidal mixing in the kuril straits on the formation of the north pacific intermediate water npiw the spatial distribution of diapycnal diffusivity recently obtained by the present authors is incorporated into an eddy permitting ogcm it is shown that the npiw is successfully reproduced although the diapycnal diffusivity averaged over the entire kuril straits is an order of magnitude less than has previously been assumed as a tuning parameter to reproduce the npiw in low resolution ogcms this strongly suggests that the effect of tidal mixing in the kuril straits on the formation of the npiw is relatively minor and that the physical processes omitted by the low resolution ogcms such as isopycnal mixing along the kuroshio extension region are much more important this suggestion gives warning of the danger that some misleading conclusions might be derived from ogcms that employ diapycnal diffusivity just as a tuning parameter to reproduce the observed features

spatial and temporal variability of surface mass balance near talos dome east antarctica 1 predictions concerning antarctica s contribution to sea level change have been hampered by poor knowledge of surface mass balance snow accumulation is the most direct climate indicator and has important implications for paleoclimatic reconstruction from ice cores snow accumulation measurements stake core snow radar taken along a 500 km transect crossing talos dome east antarctica have been used to assess accumulation signals and the representativeness of ice core records stake readings show that accumulation hiatuses can occur at sites with accumulation rates below 120 kg m 2 yr 1 differences between cores and stakes can lead to statistical misidentification of annual layers determined from seasonal signals at sites with accumulation rates below 200 kg m 2 yr 1 because of nondetection of higher and lower values achieving 10 accuracy in the reconstruction of snow accumulation from single cores requires high accumulation 750 kg m 2 yr 1 low accumulation sites are representative if cumulative rates computed over several years are used to reach the 750 kg m 2 yr 1 threshold temporal variability of accumulation over the last two centuries shows no significant increase in accumulation wind driven processes are a fundamental component of surface mass balance spatial variations in accumulation are well correlated with surface slope changes along the wind direction and may exceed 200 kg m 2 yr 1 within 1 km wind driven sublimation rates are less than 50 kg m 2 yr 1 in plateau areas and up to 260 kg m 2 yr 1 in slope areas and account for 20 75 of precipitation whereas depositional features are negligible in surface mass balance

satellite observations of the ice cover of the kuril basin region of the okhotsk sea and its relation to the regional oceanography for the period 1978 1982 this paper examines the nature of the sea ice which forms over the kuril basin of the okhotsk sea and describes the impact of this ice on the regional oceanography the paper compares the oceanographic behavior during the heavy ice season associated with the cold 1979 winter with the behavior during the lighter ice years of 1980 and 1982 examination of the oceanography in the okhotsk and the adjacent pacific shows that the early summer water column structure depends on the heat loss from the okhotsk during the preceding ice season the total amount of okhotsk ice formation and specifically the amount of ice formation in the kuril basin following the 1979 ice season the upper 200 300 m of the kuril basin waters were cooler less saline and richer in oxygen than for the other years this modification appears to be a process local to the kuril basin driven by eddy induced mixing local cooling and ice melting in the depths 300 1200 m the water modification is caused by the advection of water from the northern okhotsk for 1979 this deeper water is also less saline colder and richer in oxygen than for the lighter ice years the water modified in the okhotsk enters the adjacent north pacific through the bussol strait where for 1979 the adjacent waters are also cooler less saline and richer in oxygen down to a depth of 1000 m than for the lighter ice years

changes in detrital input ventilation and productivity in the central okhotsk sea during the marine isotope stage 5e penultimate interglacial period abstract by presenting benthic foraminifera isotope profiles and bulk geochemical composition of core sediments we offer a mutiproxy reconstruction of the central okhotsk sea oceanography between 130 to and 115 kyr related to the marine isotopic stage 5e mis 5e sediments from the site mr0604 pc7a have been compared with paleo sea surface temperatures and other records this multiparameter approach allowed to recognize three periods for mis 5e evolution characterized by variations in marine productivity and bottom oxygenation these variations have been ultimately associated with the production of okhotsk sea intermediate water and the presence or absence of nutrient contribution from the pacific deep water into central okhotsk sea aeolian input reconstructed by th sc ratio indicates higher values during the mis 6 and mis 5d compared with the mis 5e eu values indicate an input of detrital material from kurile islands and east kamchatka during the late mis 5e absent during the early mis 5e and glacial periods

the production of ice and dense shelf water in the okhotsk sea polynyas this paper examines the ice and dense water production in the okhotsk sea coastal polynyas for the 1990 1995 winters the dominant polynyas occur on the northwest and northern shelves and in shelikhov bay we use an algorithm developed for the special sensor microwave imager ssm i to derive for each polynya the area and composition of thin ice and open water and a heat flux algorithm to derive the ice and brine production historic oceanographic observations show that the northwest shelf is the only north pacific region where the 26 8 potential density surface outcrops to the surface and is also that part of the okhotsk shelf where the densest water is observed to occur in support of these observations we find that the northwest shelf polynya is the dominant ice and brine producer contributing on average about 55 of the total production shelikhov bay is the second largest producer with about 25 of the total this region has been previously neglected by both oceanographic and remote sensing studies using a combination of two dense water production models we find that the 6 year average dense water production lies between 0 2 0 4 sv the ice and brine production for the dominant northwest shelf vary interannually by a factor of 3 while the production from all the northern polynyas varies by factor of 2 the source of the variability for the northwest shelf comes from the fact that the southwest to northeast trend of the coastline and the mean winter geostrophic wind velocities are roughly parallel which means that small variations in the wind direction yield large changes in the ice production

early partitioning of quebec microcontinent formation in the paleoproterozoic the distribution of allochthonous versus parautochthonous carbonate platforms combined with the timing of initial continental rift magmatism versus the timing of subsequent rifting of the continental margin provides tectonostratigraphic evidence for the formation and isolation of the oldest documented microcontinent perhaps as a consequence of the impingement of a mantle plume onto a cratonic margin during the paleoproterozoic initial rifting of the archean nucleus of north america in eastern canada is constrained to have been diachronous between 2 17 and 2 03 ga renewed rifting of a segment of the continental margin 292 to 120 m y later was accompanied by the emplacement of ultramafic layered sills the accumulation of komatiitic and alkalic basalts the deposition of banded iron formations and the isolation of a microcontinent and its 1 93 ga continental shelf succession subsequently accreted to the telescoped continental margin during collisional orogenesis

dense water production on the northern okhotsk shelves comparison of ship based spring summer observations for 1996 and 1997 with satellite observations for the northern okhotsk sea polynyas five russian ctd surveys taken during 1995 to 1997 are used to examine the evolution of the polynya dense water the surveys show that consistent with other investigations the largest potential densities are 26 99 and the densest water occurs in sakhalin and shelikhov bays the surveys also suggest that the shelikhov water drains directly into the deep okhotsk while on the northern shelves gravity currents transport the dense water west to sakhalin bay for comparison determination of the polynya sizes and ice production from satellite passive microwave and meteorological observations shows that polynyas occur on the northwest shelf nws between ayan and okhotsk city on the northern shelf between okhotsk city and magadan and in shelikhov bay in contrast the observations show that sakhalin bay is a region of land fast ice with no polynyas so that the dense water observed here cannot form locally for all polynyas the satellite observations show that the nws contributes 60 to 70 of the total ice production and due to the warmer 1997 air temperatures the 1996 production is about 1 5 times the 1997 value an estimate of the ice production from the surveys shows a similar regional distribution and enhancement of the 1996 production with the satellite and ship estimates in agreement within their error bars finally analysis of the dense water outflow shows that the upper okhotsk sea mode water has a renewal time of about 4 years the lower part about 14 years

woce section p1w in the sea of okhotsk 1 oceanographic data description we describe the results of a world ocean circulation experiment woce survey line p1w from the open pacific ocean through the bussol strait and across the sea of okhotsk observations are presented of distributions of temperature and salinity dissolved oxygen and nutrients and some derived quantities discussion centers on the distribution of the sea of okhotsk component of the north pacific intermediate water mass and its properties the sea of okhotsk has been suggested as the only location where deep convection may occur within the north pacific or its marginal seas our analysis suggests that the surface 26 85 has recently been ventilated and arguments might be made to suggest that ventilation has occurred to 27 05 this is discussed here but detailed evidence is covered in a companion paper analyzing cfc observations the okhotsk component of the north pacific intermediate water extends to substantially greater depths and densities and so some other process is needed to create the denser water mass

snow accumulation rates in northern victoria land antarctica by firn core analysis a multiparametric chemical isotopic and physical study on three shallow firn cores sampled in northernvictoria land was carried out to obtain glaciological information and climatic data in this antarctic region sampling areas were accurately prospected to identify sites located at different altitudes and distances from the sea where the snow accumulation was not influenced by katabatic wind redistribution or summer melting stratigraphic isotopic 18 o and chemical h 2 o 2 msa and nssso 4 2 profiles were mutually examined for dating purposes and to determine the mean snow accumulation rates at three different stations annual accumulation rates of 85 420 kg m 2 a 1 were determined in the period 1971 92 an inverse pattern between accumulation rate and altitude was shown by the progression of the mean annual rates of 160 203 and 260 kg m 2 a 1 respectively in the highest medium and lowest stations the mean accumulation value of all northern victoria land data available 170 kg m 2 a 1 represents a decrease of up to 35 with respect to the estimated value most widely used until now our accumulation value is very close to that required for a zero net surface mass balance according to ice discharge a linear relationship with a gradient of 0 81 c has been found between mean 18 o values and mean annual surface temperature for different ice cores drilled in northern victoria land

woce line p1w in the sea of okhotsk 2 cfcs and the formation rate of intermediate water from august 30 to september 21 1993 temperature salinity nutrient and cfc data were collected along a section starting in the pacific ocean near bussol strait in the kuril islands crossing the basin and shelf region of the sea of okhotsk and ending near the coastal town of okhotsk at the northwest corner of the sea of okhotsk world ocean circulation experiment woce line p1w water on the continental shelf had potential density as great as 27 0 with high cfc concentrations and low temperature and salinity the sea of okhotsk intermediate water soiw ranging from 26 8 to 27 4 had uniform water properties along isopycnal surfaces that were distinctly different from either the north pacific intermediate water npiw or the shelf water found at the same density since the soiw was colder and fresher than the npiw we postulate that soiw is formed by sinking plumes and diapycnal mixing shelf derived water sdw as dense as 27 0 is formed on the shelf during the winter by cooling and brine rejection during ice formation prevailing winds move the sdw off the shelf where it sinks to an equilibrium depth and subsequently mixes isopycnally with north pacific water npw flowing into the sea of okhotsk through the kuril islands the observations on the shelf suggest that sdw directly modifies soiw to 27 0 using potential temperature salinity s and cfc data we calibrated a simple box model to determine the input of sdw into the soiw model results required a minimum of 0 9 sv 1 sv 10 6 m 3 s 1 of sdw in the formation of soiw and produced a minimum export of 2 7 sv of soiw from the sea of okhotsk our minimum calculated export of soiw into the north pacific ocean makes the sea of okhotsk a significant source of the salinity minimum present in the npiw below 27 2 the box model failed because the cfc concentrations of the sdw were too high this suggests that sdw directly ventilates the soiw to a maximum of 27 2 the unique properties of the soiw below 27 2 must be the result of diapycnal mixing in the sea of okhotsk and isopycnal mixing with inflowing npw

observations of ice ocean eddy streets in the sea of okhotsk off the hokkaido coast using radar images abstract this study examines the features of fairly regular ocean wave motion in which some eddy streets or backward breaking waves are successfully visualized using sea ice floes as a tracer these examinations are made using the time sequence of radar imagery data collected during the past 20 years 1969 88 the correspondence of the radar images with the actual pattern is partially confirmed through aircraft observations the ice ocean eddy street or backward breaking wave pattern runs parallel to the coastline at a distance of about 20 km from the hokkaido coast the eddy street also corresponds to a boundary between the soya warm current and colder less saline offshore water the wave motion is characterized by wavelengths of 40 55 km phase velocities of 14 20 km day 1 and periods of 2 3 3 5 days the regular ice ocean wave motion pattern was observed when pack ice had a small ice concentration composed of uniform sized ice floes and weak winds the sea ice floes serve as a highly effective flow i

mantle plumes and flood basalt stratigraphy in the parana south america geochemical studies of the parana continental flood basalts in brazil have led to the recognition of distinct magma types which have been used to infer the internal stratigraphy of the lava pile the overstepping of stratigraphic units toward the north and a similar compositional change in sills within the underlying parana basin sedimentary rocks imply that the site of magnatism migrated 750 km toward the north during this volcanic event this has important implications for recent plume related models that have argued whether fithospheric rifting must accompany the presence of a mantle plume in order to generate continental flood basalt magmatism it is difficult to ascribe the magnitude and direction of the shift in the locus of the parana magmatism to movement of the brazilian lithosphere relative to the underlying tristan mantle plume instead it is suggested that the observed lava distribution and internal structure of the parana etendeka flood basalt province were imposed by the intracacies of the rifting process during the initial opening of the south atlantic ocean

adcp referenced kuroshio and oyashio water transports for north pacific intermediate water formation abstract the adcp referenced geostrophic circulation of the oyashio and kuroshio waters in the density range 26 6 27 2 in the kuroshio oyashio interfrontal zone is examined by synoptic observations with a ctd and shipboard adcp in may 1992 and may 1994 in order to investigate the absolute transports of the source waters for north pacific intermediate water npiw formation the kuroshio and oyashio components are calculated by the adcp referenced transport combined with the mixing ratio assuming isopycnal mixing between pure kuroshio and oyashio waters as a result the kuroshio transport involved in the npiw formation is estimated to be 7 8 sv sv 106 m3 s 1 which is the net component along the kuroshio extension ke from the separation point near the cape nojima to the east side of the first crest of the ke the oyashio transport is estimated to be 5 6 sv which consists of coastal 1 2 sv and offshore 3 4 sv separated by warm core rings and which subsequently merges with the ke at the east side

distribution and characteristics of mesoscale cyclones in the antarctic ross sea eastward to the weddell sea abstract the mesoscale cyclone activity observed in the portion of antarctica that faces the south pacific ocean and weddell sea area is summarized from a study of 1991 in general area normalized results reveal much greater mesoscale cyclonic activity over the ross sea ross ice shelf and southern marie byrd land than on both sides of the antarctic peninsula more than 50 of the observed mesoscale vortices are of the comma cloud type the average diameter of mesoscale vortices is approximately 200 km near terra nova bay 270 km near byrd glacier and 280 km near siple coast near the antarctic peninsula the average diameter is about 370 km over the bellingshausen sea and 380 km on the weddell sea side the largest percentage of deep vortices occurs over the bellingshausen sea sector 38 of all cases where convective instability frequently occurs over the ross sea ross ice shelf and weddell sea sectors the majority of the mesoscale vortices are low cloud features that probably do not exceed the 700

transport and modification processes of dense shelf water revealed by long term moorings off sakhalin in the sea of okhotsk 1 the region off the east coast of sakhalin is thought of as an important pathway of dense shelf water dsw from its production region in the northwestern okhotsk sea to the southern okhotsk sea from july 1998 to june 2000 the first long term mooring experiment was carried out in this region to observe the southward flowing east sakhalin current esc and dsw moored and associated hydrographic data show considerable modification of cold dense water via mixing with warm offshore water in the slope region off northern sakhalin significant onshore eddy heat flux was observed at the northernmost mooring 54 9 n which suggests the occurrence of baroclinic instability the eddy heat flux was not significant farther south at moorings along 53 n cold anticyclonic eddies were identified that were consistent with isolated eddies seen in the hydrographic data the three years of hydrographic data also showed large differences in extent and properties of dsw furthermore the mooring data show that seasonal variability of dsw was quite different in the two years the average dsw transport for 26 7 evaluated using the moored data at 53 n for 1 year 1998 1999 was 0 21 sv 106 m3 s 1 this value is at the lower end of the previous indirect estimates along with the dsw modification this transport estimate indicates that dsw was not only carried southward by the esc but was spread offshore by eddies off northern sakhalin

distribution and formation of okhotsk sea intermediate water an analysis of isopycnal climatological data 1 in order to clarify the distribution and formation of okhotsk sea intermediate water osiw an isopycnal climatological data set based on all of the available historical observations is developed and examined the isopycnal maps clearly show that there are two direct ventilation sources for osiw dense shelf water dsw with cold and fresh properties influenced by sea ice formation in the northwest shelf region and forerunner of soya warm current water fscw which has warm and saline properties originating in the japan sea the cold and fresh water extends southward from the northwest shelf to the shelf slope off sakhalin island it suggests that dsw is transported southward by the east sakhalin current the dsw enters the kuril basin and mixes with fscw and western subarctic water wsaw originating from the north pacific to form osiw the annual mean production rate of dsw estimated from the total volume of dsw over the shelf in spring and summer is 0 67 sv 1 sv 106 m3 s the annual mean volume transport of fscw is estimated to be 0 08 sv on the basis of its cross section area and the current speed assumption of isopycnal mixing yields a mixing ratio of 1 1 0 1 among dsw wsaw and fscw to form osiw we estimate the annual production rate of osiw to be 1 4 sv the corresponding osiw s renewal time is 7 years continued assumption of isopycnal mixing yields a mixing ratio of 0 6 0 4 between wsaw and osiw to form oyashio intermediate water oyiw

paleomagnetism and u pb geochronology of diabase dyke swarms of minto block superior province quebec canada in the first collaborative study of paleomagnetism and precise u pb geochronology in the minto block of the superior province mafic dyke swarms with three widely divergent paleomagnetic signatures and isotopic ages have been identified the 2505 2 ma ptarmigan dykes trend north to northeast and have a virtual geomagnetic pole at 42 s 220 e similar to that of 2473 2446 ma matachewan dykes of the southern superior province the ca 2230 ma maguire dykes trend west to northwest and yield a paleopole at 9 s 267 e similar to those for 2216 8 4 ma senneterre dykes and 2217 2210 ma nipissing sills of the southern superior and southern provinces respectively the 2209 1 ma klotz dykes trend west northwest but do not carry a consistent magnetization direction finally 1998 2 ma minto dykes of west northwest to northwest trend identical in age to the 1998 ma 2 ma purtuniq ophiolite of the cape smith belt have a paleopole at 38 n 174 e the similarity of paleopoles for the ca 2 23 2 21 ga maguire

chlorofluorocarbons in the sea of okhotsk ventilation of the intermediate water 1 ventilation of the intermediate layer in the sea of okhotsk is studied with regard to the ventilation of north pacific intermediate water npiw measurements of chlorofluorocarbons cfcs from 1998 to 2000 reveal that the okhotsk intermediate water is ventilated in two ways the first consists of dense water formation in the polynyas that form on the northern shelves during winter measurements show that on the northwestern shelf because of atmospheric cooling and brine rejection the cold water that forms is dense enough to enter the intermediate layer the cfc concentration in this dense shelf water dsw is high and almost saturated with respect to atmospheric cfcs indicating that the dsw experiences active air water gas exchange during its formation away from the shelves the cfc distribution shows that the dsw directly ventilates the upper level of the okhotsk sea intermediate water osiw the second ventilation process is driven by the strong tidal mixing around the bussol strait the observed distribution of cfcs at the 27 4 level suggest that diapycnal mixing around the strait transports cfcs from the surface to this deeper layer ventilating the osiw combination of both processes means that the osiw is more ventilated than pacific water at the same density levels

decreased surface salinity in the sea of okhotsk during the last glacial period estimated from alkenones 1 studies of sediment cores from the sea of okhotsk which is characterized by seasonal sea ice have shown a large variability of sea ice indicators during the glacial interglacial cycles in this study we apply the relative abundance of the c37 4 alkenone to total c37 alkenones c37 4 as a molecular indicator of salinity and water masses to further investigate surface oceanographic condition in the sea of okhotsk in the glacial period we found a large fluctuation of c37 4 4 35 with higher values 20 35 during the last glacial period and lower values 8 during warm periods suggesting a decreased surface salinity in the glacial period the variation of c37 4 was found to be consistent with the ice rafted debris ird in the sediment core correlation coefficient r2 between c37 4 and ird 0 72 this suggests that the duration of seasonal sea ice was longer in the glacial period than today the lowered surface salinity in the glacial might also have been seriously affected by the close off of the shallow soya strait which currently transports massive volumes of saline water from the sea of japan to the sea of okhotsk

paleomagnetism and u pb geochronology of the 2 17 ga biscotasing dyke swarm ontario canada evidence for vertical axis crustal rotation across the kapuskasing zone u pb dates on baddeleyite yield ages of 2167 8 2 2 and 2171 6 1 2 ma on two northeast trending dykes west of the kapuskasing zone in ontario canada these ages identify the dykes as belonging to the biscotasing dyke swarm east of the kapuskasing zone which was previously dated at 2166 7 1 4 ma by u pb on baddeleyite and zircon the new dates show that the biscotasing swarm was emplaced over an area of at least 300 000 km2 much larger than hitherto suspected and in a geologically short period of time of about 5 million years a comparison of paleomagnetic data from biscotasing and 2 45 ga matachewan dykes on either side of the kapuskasing zone suggests that the western half of the superior province has rotated about 10 20 counterclockwise relative to the eastern half across the kapuskasing zone this movement may have been accompanied by rifting farther north which ultimately led to the paleoproterozoic embayment underlying hudson bay that gives the superior province its characteristic butter

the climatology of the north atlantic abstract data from approximately 144 000 hydrographic stations in the north atlantic have been retrieved from the national oceanic data centre and analysed to produce maps of mean pressure temperature salinity and oxygen on selected potential density surfaces for the domain bounded by 0 85 w and 0 65 n the data span the period from 1904 to 1990 with the majority of the data from the last four decades the data set for this region is 60 larger than that used in the production of levitus climatological world atlas this increase in stations coupled with smoothing scales specific to the north atlantic rather than the global ocean considerably improves the resolution of the basin s features the mean property fields and their associated standard deviations are resolved on a one degree grid with little smoothing contrasting with the levitus atlas where properties although presented on a one degree grid have been smoothed on the order of 1000km another important feature of this database is the process by which irregularly spaced data are averaged onto a regular grid in a significant departure from the levitus analysis which averaged on depth surfaces these data were averaged on potential density surfaces thus eliminating an artificial mixing of water mass properties the database is used to describe the baroclinicity of well known features such as the gulf stream the north atlantic current and the deep western boundary current and to elucidate the recirculations associated with these currents it additionally resolves several new features in the intermediate and deep north atlantic these features include the signature of a large scale deep recirculation that extends southwestward from the eastward extension of the north atlantic current to the separation point of the gulf stream near cape hatteras this recirculation which spans approximately 2000m of the water column encompasses more local recirculations and potentially mixes subpolar and subtropical waters furthermore in the upper thermocline this database reveals a coherent azores current that stretches from the gulf stream system south of the tail of the grand banks to madeira this flow is marked by divergences to the south and convergences from the north such that its downstream transport is not much changed

geochemistry of mafic magmas from the ungava orogen quebec canada and implications for mantle reservoir compositions at 2 0 ga the ungava orogen of northern quebec is one of the best preserved proterozoic mobile belts of the world recording 200 ma of plate divergence and convergence voluminous magmatism associated with rifting of the superior province basement 2 04 ga resulted in the development of a volcanic rift margin sequence and an ocean basin four distinct mafic magma suites were erupted 1 continental basalts eskimo formation western and central povungnituk group with moderate to high zr nb and negative nb anomalies which have interacted with the continental crust nd 2 0 ga from 7 4 2 mafic lavas from the flaherty formation eastern povungnituk group and some watts group lavas associated with passive margin rifting having slightly enriched isotopic signatures nd 2 0 ga 2 7 to 4 4 compared to the contemporaneous depleted mantle high nb y n and low zr nb ratios 4 4 and 8 9 respectively 3 a highly alkaline oib like suite nd 2 0 ga 2 3 to 3 2 nb y n 12 within the povungnituk group composed of nephelinites basanites and phonolites and 4 depleted mg rich basalts and komatiitic basalts nd 2 0 ga 4 5 to 5 5 with trace element characteristics of n morb but with higher fe and lower al than primitive morb chukotat group ottawa islands and some watts group samples the ocean basin into which these lavas were erupted was subsequently destroyed during subduction between 1 90 and 1 83 ga resulting in the development a magmatic arc narsajuaq terrane and parent group the ungava magmas provide a unique window into the mantle at 2 0 ga the chemical and isotopic similarity of these proterozoic magmas to modern day magmas provides strong evidence that the interplay between depleted mantle oib mantle and sub continental mantle during the proterozoic was comparable to that of the modern earth

relationships between crustal contamination and crystallisation in continental flood basalt magmas with special reference to the deccan traps of the western ghats india the upper part of the deccan traps sequence bushe to mahabaleshwar formations shows a statistically significant tendency for the most mafic lavas to be the most contaminated by crustal materials this is the reverse of the relationship shown by suites evolving by contamination accompanied by fractional crystallisation afc the observed correlations e g between mg number and sr isotope initial ratios are partly an accidental consequence of the fact that the most mafic lavas are more abundant in the lower part of the sequence while contaminant availability declines in the upper part it is probable however that the correlations are augmented by increased contamination of hotter magma batches during ascent through dykes a process during which fractional crystallisation is suppressed by magmatic turbulence the absence of afc relationships suggests that most of the contamination took place during the ascent stage rather than in a magma chamber other continental flood basalt provinces such as the parana and etendeka do show afc relationships and it is speculated that this may be a result of magma chamber contamination coupled with flow rates which prevent contamination during ascent

age of the richmond gulf group and implications for rifting in the trans hudson orogen canada abstract the aphebian richmond gulf group of the east coast of hudson bay is a fluvial sandstone sequence containing basalt flows it was shed eastward from a rifting related thermal dome situated in the present central part of hudson bay sandstone from the base of the group contains a uraniferous diagenetic apatite cement u pb and pb pb isochron analysis from this material show the age of the apatite haematite cement to be 2025 25 ma old these data provide an older age bracket for the deposition of the richmond gulf nastapoka and belcher groups they also date the formation of the richmond gulf graben an aulacogen related to the initial rifting of the trans hudson orogen

a numerical study of barotropic instability associated with the soya warm current in the sea of okhotsk abstract numerical model experiments have been carried out in an attempt to elucidate the generation mechanism of the eddy or wave street in the soya warm current we use a barotropic model incorporating bottom topography under realistic conditions the model produces waves whose properties are within range of the observed ones the generation mechanism of the waves proposed in this experiment is as follows when the current is driven by the mean water level difference between the japan sea and the sea of okhotsk the flow separates from the cape in the soya strait in the region of the flow separation strong positive vorticity is produced by the frictional torques occurring as the water flows through the strait and by vortex stretching as the water is pushed out to deeper depths this strong vorticity or horizontal shear induces barotropic instability in which the waves are generated in brief the system of the soya warm current accompanied by an eddy street is interpreted as a good geophysical ex

structure and seasonal variability of the east sakhalin current abstract in order to clarify the structure and seasonal variability of the flow field near the western boundary of the sea of okhotsk long term mooring measurements were carried out from 1998 to 2000 in this region in most of the mooring period a persistent southward flow the east sakhalin current was observed which extends from the surface to a depth around 1000 m the speed of this southward flow clearly changed seasonally the peak monthly mean speed along 53 n at a depth of 200 m attained a maximum of 37 9 cm s 1 in january and a minimum of 10 8 cm s 1 in july three different cores of intense flow were identified in the southward flow the first core was centered over the continental slope and had rather large vertical extent reaching the bottom on the slope the second core was trapped over the shelf near the surface and was observed from october to november this core was associated with less saline surface water affected by the amur river discharge the third core was intensified toward

snow precipitation at four ice core sites in east antarctica provenance seasonality and blocking factors snow precipitation is the primary mass input to the antarctic ice sheet and is one of the most direct climatic indicators with important implications for paleo climatic reconstruction from ice cores provenance of precipitation and the dynamic conditions that force these precipitation events at four deep ice core sites dome c law dome talos dome and taylor dome in east ant arctica were analysed with air mass back trajectories cal culated using the lagrangian model and the mean composite data for precipitation geopotential height and wind speed field data from the european centre for med ium range weather forecast from 1980 to 2001 on an annual basis back trajectories showed that the atlantic indian and ross pacific oceans were the main provenances of precipitation in wilkes land 80 and victoria land 40 respectively whereas the greatest influence of the ice sheet was on the interior near the vostok site 80 and in the southwest ross sea 50 an effect that decreased towards the coast and along the antarctic slope victoria land received snowfall atypically with respect to other antarctica areas in terms of pathway eastern instead of western seasonality summer instead of winter and velocity old air age geopotential height patterns at 500 hpa at low 10 days and high 2 6 days frequen cies during snowfall cycles at two core sites showed large positive anomalies at low frequencies developing in the tasman sea eastern indian ocean at higher latitudes 60 70s than normal this could be considered part of an atmospheric blocking event with transient eddies acting to decelerate westerlies in a split region area and accelerate the flow on the flanks of the low frequency positive anomalies

satellite passive microwave studies of the sea of okhotsk ice cover and its relation to oceanic processes 1978 1982 this paper describes the use of the nimbus 7 scanning multichannel microwave radiometer smmr satellite data to study the ice cover in the sea of okhotsk during the four winters of 1978 1982 the ice concentration estimates obtained from smmr are used to study two different polynyas one over the kashevarova bank and the other over the northwest continental shelf for the kashevarova polynya this study shows that the polynya which may be related to the upwelling observed in historic summer cruises occurs directly over the bank for the continental shelf which because of strong offshore winds and cold temperatures is a region of high ice production the polynya areas are combined with heat flux estimates from weather station data to yield the production rates of ice salt and dense shelf water as a previous study by kitani 1973 shows the mixing of this dense shelf water with pacific water yields a water mass unique to the okhotsk which is the layer of cold low salinity intermediate water between depths of 150 and 800 m from our calculations we estimate that the dense shelf water is produced at an annual rate of about 0 5 sv and that the intermediate water is produced at a rate of 1 2 sv which yields a renewal time for this layer of 10 40 years

okhotsk sea intermediate water formation deduced from oxygen isotope systematics to clarify the mechanisms of the okhotsk sea intermediate water formation water samples collected in the okhotsk sea and neighboring western north pacific were analyzed for 18o as well as salinity and other routinely measured components the 18o salinity relation in the okhotsk sea was markedly different from that in the western subarctic pacific feeding the okhotsk sea the intermediate water of the okhotsk sea was less saline than that of the western subarctic water at the same density but was more saline at the same 18o value especially in the density range 26 5 27 0 this could be due to mixing of dense shelf water formed during sea ice formation with neighboring water the amount of fresh water removed by the sea ice formation was estimated from the salinity anomaly of the okhotsk sea intermediate water the calculated amounts of fresh water removed from the okhotsk sea intermediate water corresponded to the amount of sea ice formed for 0 6 3 8 years in the okhotsk sea this suggests that the residence time of the okhotsk sea intermediate water is a few years

the origin of the north pacific intermediate water possible source regions of the north pacific intermediate water npiw were investigated with synoptic conductivity temperature depth surveys in the okhotsk sea kuril basin a pycnostad referred to as the okhotsk sea mode water osmw was found in the density range of 26 6 27 the pycnostad is not seen in the western subarctic gyre wsag thus it is an indicative water peculiar to the okhotsk sea the maximum thickness is at 26 7 26 9 centered at 26 8 which coincides with the npiw density range in the north pacific subtropical gyre in the oyashio area east of the southern kuril islands and hokkaido waters that have intermediate temperature salinity and potential vorticity between the osmw and the wsag water were distributed suggesting a following transport route of the npiw source water the thick thus low q q is potential vorticity and low salinity water mass outflowing from the okhotsk sea mixes with the relatively warm saline and high q wsag water to form the oyashio water a coastal part of the oyashio water flows southwestward along the east coast of the southern kuril islands and hokkaido retaining the pycnostad q minimum a large part of the low q oyashio water flows further southward and merges with the kuroshio extension and then flows eastward forming new npiw in this process a salinity minimum develops and the q minimum disappears because of the mixing with a saline kuroshio water old npiw without a pycnostad in the npiw density range these results suggest that the origin of npiw is the water mass in the okhotsk sea osmw and the density of the water mass primarily determines the npiw density centered at around 26 8

effects of along shore wind on dsw formation beneath coastal polynyas application to the sea of okhotsk 1 it is known that salinity anomaly under a polynya reaches and remains an equilibrium value s after termination of its initial increase associated with brine rejection at the surface in this paper we investigate effect of along shore downwelling favorable wind on the equilibrium salinity anomaly by idealized numerical calculations and scale based estimates numerical calculations showed that high saline water beneath polynya is advected downstream by wind driven circulations over the shelf besides baroclinically developed eddies which consequently induces a decrease in s beneath polynya the downwelling favorable wind generates an offshore overturning flow through lower layers referred to as ekman compensation flow ecf which causes a great offshore salinity flux as well as an along shore current we also constructed an equation for estimation of s from the viewpoint of salinity budget over the polynya region in which lateral salinity fluxes caused by ecf along shore wind driven current and baroclinic eddies are scaled the solution s was also verified by a series of numerical calculations furthermore we investigated the effects of along shore wind on dense water generation beneath the okhotsk coastal polynyas we conducted simplified numerical experiments assuming the okhotsk situation in which fs and offshore width b of polynya are predicted by a thermodynamic polynya model with ecmwf meteorological variables the simulated salinity shows a good agreement with the direct measurements the theoretical estimates for s was also applied to two okhotsk polynyas northwestern polynya nwp and northern polynya np in conclusion we found that the along shore wind causes greater salinity decrease in np than in nwp whose variations substantially depend on the aleutian low activity

episodic ages of greenstones a key to mantle dynamics two greenstone age minima at 2 5 2 2 ga and 1 65 1 35 ga may correlate with ages of supercontinents when a greater proportion of greenstones were recycled into the mantle by subduction from the age distributions of greenstones and juvenile continental crust earth history can be divided into three stages i 2 8 ga when greenstones and microcontinents formed and collided continuously although probably not forming a supercontinent until about 3 ga ii 2 8 1 3 ga where a clear episodisity is apparent in greenstone eruption and collision ages and where two greenstone age minima coincide in age with supercontinents and iii 1 3 ga when greenstones and continents appear to have formed and collided continuously perhaps in response to significant overlap in the times of dispersal and assembly of supercontinents greenstone age peaks 2 7 1 9 and 1 3 ga may reflect catastrophic overturn of the mantle initiated by episodes of sinking of cold lithospheric slabs through the 660 km discontinuity to the d layer initiating an episode of major mantle plume activity continuous production and preservation of greenstones in the last 1 3 gy is consistent with seismic tomography data which suggest a steady sinking of slabs into the lower mantle

near surface circulation and tidal currents of the okhotsk sea observed with satellite tracked drifters 1 near surface circulation of the okhotsk sea was observed with argos drifters from august 1999 to february 2000 the drifters clearly revealed the existence of the southward boundary current the east sakhalin current off the east sakhalin this current is strongly controlled by bottom topography and confined to the region shallower than 1000 m the volume transport of this current is estimated to be in the range of 4 9 sv 1 sv 106m3 s 1 with the increase from summer to winter the current appears to consist of two cores one exists near the coast 50 150 m depths with typical speeds of 0 3 0 4 m s 1 and the other exists over the shelf slope 300 900 m depths with typical speeds of 0 2 0 3 m s 1 a part of this southward current continues as far as the southern tip of sakhalin island while another part turns to the east around terpeniya bay 48 n flowing eastward as far as bussol strait most of the drifters that survived in the okhotsk sea went out to the pacific through bussol strait by less than a half year suggesting that bussol strait is the main pathway for the surface water to flow out from the okhotsk sea mesoscale anticyclonic eddies with diameters of 100 200 km are dominant in the kuril basin diurnal shelf waves were identified over the shelf in the northern part of the east sakhalin shelf large amplification of diurnal tidal currents order of 1 0 m s 1 was observed over kashevarov bank along with the residual anticyclonic circulation both diurnal and semidiurnal tidal currents were found to be enhanced in and around bussol strait

upb geochronology of the western cape smith belt canada new insights on the age of initial rifting and arc magmatism abstract the cape smith belt of northern quebec is the foreland to hinterland transition of the ungava orogen a component of the paleoproterozoic trans hudson orogen of north america u pb ages for rift and volcanic arc related units from the cape smith belt are presented and used to evaluate models of its tectonic evolution a gabbroic sill intrusive into the rift related sediments near the base of the povungnituk group is 2038 2 4 ma old indicating that rifting of the superior province was initiated prior to that time 80 m y earlier than previously reported a granodiorite intrusive into the volcanic rocks of the povungnituk group is dated at 1991 2 ma indicating that magmatism associated with the rifting event was active at that time 30 m y earlier than formerly thought the age of parent group arc related magmatism ranges from 1874 3 4 ma the age of a diorite intrusion to 1860 2 ma the age of another diorite intrusion and of a rhyolite a granodiorite intrusive in the parent group yields an age of 1845 6 ma magmatism of the parent group is thought to be related to northward dipping subduction of the superior province margin below the watts group a gabbroic intrusion in the 2000 ma old watts group is dated at 1858 2 ma these ages are consistent with a tectonic model in which the rocks of the cape smith belt formed in a single continental rift to oceanic progression followed by subduction which led to an arc continent collision a comparison of u pb ages for similar events in different sectors of the trans hudson orogen in canada reveals that early events are diachronous and range from 2169 ma to 2038 ma the main collisional events are coeval in the ungava and new quebec orogens and in some of the western sectors at 1830 1860 ma younger ages of 1800 1820 ma are obtained for the late collisional stages throughout the trans hudson orogen

paleomagnetism u pb geochronology and geochemistry of lac esprit and other dyke swarms james bay area quebec and implications for paleoproterozoic deformation of the superior province an extensive set of north to northwest trending diabase dykes termed the lac esprit swarm is identified in the superior province east of james bay based on geological mapping and a distinctive paleomagnetic pole 61 7 n 169 1 e dm 7 7 dp 5 5 the lac esprit swarm yields a u pb baddeleyite age of 2069 1 ma similar to that of the 2076 5 4 ma fort frances swarm of the western superior province their paleomagnetic declinations differ by 23 12 after correction to a common reference locality the difference is likely due mainly to counterclockwise rotation about a vertical axis of the fort frances area relative to the lac esprit area differential rotation of 10 20 has been proposed more locally across the kapuskasing structural zone separating the eastern and western superior province in earlier paleomagnetic studies of ca 2450 ma matachewan and 2170 ma biscotasing dyke swarms thus relative rotation may have involved the entire eastern and western superior province perhaps in response

characteristics of the ross ice shelf air stream as depicted in antarctic mesoscale prediction system simulations 1 streamlines of the mean annual near surface winds over the antarctic continent suggest a confluent channeling of the drainage flows off the ice sheets and onto the ross ice shelf a persistent cyclonic circulation to the north of the ice shelf supports a large scale pressure field that reinforces the continental drainage flows owing to these two processes an enhanced low level airflow is present along the southern and western sections of the ross ice shelf the resulting air stream known as the ross ice shelf air stream ras is one of the persistent and prominent low level wind features seen in the antarctic real time mesoscale simulations of the antarctic atmosphere and high southern latitudes using a modified version of the pennsylvania state university national center for atmospheric research mesoscale modeling system have been ongoing since the 1999 2000 austral field season model results from the 1 year period november 2001 to october 2002 have been analyzed to investigate the mean structure and modulation of the ross ice shelf air stream analyses of model results show the low level air stream over the western ross ice shelf has a wind speed maxima that is linked to the steep topography to the west individual cases of strong wind events appear to contain a significant barrier wind component that arises from cold air damming against the transantarctic mountains cyclones that frequently form in the ross sea are shown to establish conditions that promote barrier wind dynamics and thus significantly modulate the intensity of the ras

seasonality of airmass pathways to coastal antarctica ramifications for interpreting high resolution ice core records abstractunderstanding airmass pathways is critical for ice core interpretation and the ability to determine the broadscale characteristics and seasonality of synoptic scale flow using paleoclimate records offers great potential to improve the understanding of past atmospheric circulation the dominant airmass pathways to a coastal antarctic ice core site at the whitehall glacier in the ross sea are modeled using snowfall and high resolution stable isotope data between 1979 and 2006 combined with back trajectories produced from both ncep ncar and ecmwf interim re analysis era interim data back trajectories generated from both datasets produce comparable results they show that high snowfall is associated with cyclonic airflow in the ross sea with a strong meridional component along the western ross sea coast over a 28 yr time frame trajectories also reveal a clear distinction between flow paths associated with above and below average annual temperatures high and low d in the ice core record in

enriched mantle components in proterozoic continental flood basalts of the cape smith foldbelt northern quebec magmatism associated with ca 2 04 ga rifting of the superior province resulted in the formation of a succession of tholeiitic and alkaline basalts as well as minor rhyolites collectively known as the povungnituk group cape smith foldbelt the tholeiites are not typical continental flood basalts cfb as they lack significant negative nb and ta anomalies indicating that crustal contamination has not played a major role in their evolution although crystal fractionation along a gabbroic cotectic can account for much of the compositional variation in the povungnituk basalts it cannot explain the range of observed traceelement ratios which is similar to that from tholeiitic to highly alkaline lavas observed in modern ocean island basalt suites variations of la sm and nb zr indicates the presence of a highly enriched component and that mixing between this enriched component and a non enriched end member can account for the range of trace element ratios in the povungnituk lavas although the most enriched tholeiites are spatially associated with an alkaline volcanic center enriched tholeiites are widely interspersed in the povungnituk group and are also found in other parts of the eastern trans hudson orogen the paleoproterozoic mantle source appears to have contained a dispersed but variable enriched component that was responsible for the variation of degree of enrichment of the povungnituk tholeiitic basalts d 2003 elsevier b v all rights reserved

synoptic controls on precipitation pathways and snow delivery to high accumulation ice core sites in the ross sea region antarctica 1 dominant storm tracks to two ice core sites on the western margin of the ross sea antarctica skinner saddle sks and evans piedmont glacier are investigated to establish key synoptic controls on snow accumulation this is critical in terms of understanding the seasonality source regions and transport pathways of precipitation delivered to these sites in situ snow depth and meteorological observations are used to identify major accumulation events in 2007 2008 which differ considerably between sites in terms of their magnitude and seasonal distribution while snowfall at evans piedmont glacier occurs almost exclusively during summer and spring skinner saddle receives precipitation year round with a lull during the months of april and may cluster analysis of daily back trajectories reveals that the highest accumulation days at both sites result from fast moving air masses associated with synoptic scale low pressure systems there is evidence that short duration pulses of snowfall at sks also originate from mesocyclone development over the ross ice shelf and local moisture sources changes in the frequency and seasonal distribution of these mechanisms of precipitation delivery will have a marked impact on annual accumulation over time and will therefore need careful consideration during the interpretation of stable isotope and geochemical records from these ice cores

a comprehensive mass flux scheme for cumulus parameterization in large scale models abstract observational studies indicate that a mass flux approach may provide a realistic framework for cumulus parameterization in large scale models but this approach through the introduction of a spectral cloud ensemble leads normally to rather complex schemes in this paper the question is addressed whether much simpler schemes can already provide realistic values of the thermal forcing by convection under various synoptic conditions this is done through verifying such a scheme first on data from field experiments for periods of tropical penetrative convection gate marshall islands tradewind cumuli atex bomex and extratropical organized convection sesame 79 and then in a nwp model the scheme considers a population of clouds where the cloud ensemble is described by a one dimensional bulk model as earlier applied by yanai et al in a diagnostic study of tropical convection cumulus scale downdrafts are included various types of convection are represented i e penetrative convection in c

a comprehensive habit diagram for atmospheric ice crystals confirmation from the laboratory airs ii and other field studies abstract recent laboratory experiments and in situ observations have produced results in broad agreement with respect to ice crystal habits in the atmosphere these studies reveal that the ice crystal habit at 20 c is platelike extending to 40 c and not columnar as indicated in many habit diagrams found in atmospheric science journals and texts these diagrams were typically derived decades ago from laboratory studies some with inherent habit bias or from combinations of laboratory and in situ observations at the ground observations that often did not account for habit modification by precipitation from overlying clouds of varying temperatures habit predictions from these diagrams often disagreed with in situ observations at temperatures below 20 c more recent laboratory and in situ studies have achieved a consensus on atmospheric ice crystal habits that differs from the traditional habit diagrams these newer results can now be combined to give a comprehensive description of ice crystal habits

distributions of dissolved organic carbon and nitrogen in the western okhotsk sea and their effluxes to the north pacific abstract the okhotsk sea is considered the only ventilation source area for north pacific intermediate water npiw which is widely distributed in the low and middle latitudes of the north pacific previous studies have confirmed high levels of dissolved organic carbon doc in npiw yet the amounts and the processes driving doc export from the okhotsk sea are poorly understood in this study concentrations of doc and dissolved organic nitrogen don were measured in the western okhotsk sea during the summer of 2006 and additional doc measurements were made during the late spring of 2010 results indicate that doc transport to the intermediate waters 26 7 27 0 occurs through two processes the first process involves the spread of water discharged from the continental shelf dense shelf water which contributes to a doc and turbidity maxima in the 250 300 m layer of okhotsk sea mode water osmw located off the eastern sakhalin coast the second process involves diapycnal mixing in the kuril basin and the bussol strait where doc is transported to a depth greater than 800 m the ratio of doc don in osmw was significantly higher in the kuril basin and bussol strait than off of the sakhalin coast which suggests that the transport of terrigenous organic matter from the bottom occurs in the former regions doc and don efflux from the okhotsk sea to the intermediate layer in the north pacific water 26 7 27 0 were estimated to be 68 72 tg c yr 1 and 5 4 tg n yr 1 respectively for which the doc transported by diapycnal mixing accounts for 37 we conclude that diapycnal mixing in the kuril basin and bussol strait regions could play a significant role in regulating the quality and quantity of doc exported to the intermediate water in the north pacific

age and tectonic implications of paleoproterozoic mafic dyke swarms for the origin of 2 2 ga enriched lithosphere beneath the ungava peninsula canada abstract mafic dyke swarms represent short lived magmatic events that carry important temporal and chemical constraints for the evolution of the lithospheric mantle five baddeleyite u pb isotopic analyses of paleoproterozoic mafic dyke swarms intruding the ungava peninsula yielded ages of 2508 6 2220 1 2212 3 2199 5 and 2149 3 ma these ages fall within the 2 5 2 0 ga period previously defined by five other swarms which together comprise a magmatic record of more than 500 ma the similar age composition and surface area of two 2 51 ga swarms along with the lack of coeval supracrustal rocks suggest they correspond to failed rifts an important magmatic hiatus of 280 ma follows but ends with the intrusion of numerous dykes between 2 23 and 2 20 ga in the thinnest lithosphere of the northern ungava peninsula these dykes exhibit chemical signatures that vary from enriched older 2229 2212 ma dykes nd t 4 to relatively depleted 2209 2199 ma voluminous younger dykes nd t 1 4 la yb ca 2 21 2 20 ga later dykes emplaced ca 2 17 ga within a rejuvenated paleoproterozoic lithosphere also have depleted chemical compositions and map the extent of rifting coeval with the emplacement of early basalts in the labrador trough dykes emplaced in the 2 15 2 00 ga period further to the south are proximal to coeval continental basalts with which they share enriched isotopic compositions nd t 1 5 to 7 and a positive correlation between la yb and zr nb la yb 4 10 zr nb 7 20 that suggest assimilation of an archean crustal component a progressive decrease in the nd t values of these magmas with decreasing age further implies increasing contamination until the archean lithosphere failed ca 2 0 ga and permitted the eruption of isotopically depleted basalts the ca 2 2 ga depleted northern dykes and the 2 1 1 9 ga povungnituk basalts of the cape smith foldbelt share a negative correlation between zr nb and la yb that is expected for the incorporation of an enriched lithospheric component this component is represented by the alkaline rocks comprised in the circum ungava supracrustal belts carbonatites lamprophyric lavas alkaline basalts and by the lac aigneau lamprophyric dykes 1941 3 ma intruding the ungava peninsula these alkaline magmas collectively have 2 2 2 1 ga depleted mantle nd model ages t dm similar to a 2 15 ga sm nd isochron defined by the basaltic rocks of the supracrustal belts although these nd t dm ages and isochron are 100 300 ma older than magmatic ages they are identical with the ca 2 2 ga mafic dykes of the ungava peninsula this time correlation along with the similar chemical signature of the northern dykes and younger povungnituk basalts suggest that the composition of younger lavas and alkaline magmas was influenced by an enriched component associated with the pervasive metasomatism of the lithosphere coeval with the emplacement of the many ca 2 2 ga dykes