sea ice motion in response to geostrophic winds it is an old rule of thumb that sea ice moves with a speed of about 2 of the surface wind and about 45 to the right of the wind a similar relationship between the ice velocity and the geostrophic wind is examined here it is found that only about half of the long term several month average ice motion is directly related to the geostrophic wind the other half being due to the mean ocean circulation on shorter time scales and in all seasons more than 70 of the variance of the ice velocity in the central arctic ocean is explained by the geostrophic wind within about 400 km of the coasts the geostrophic wind is less successful in explaining the ice motion the spatial variations in ice velocity are also partly explained by the geostrophic wind about half of the variance in the large scale ice vorticity and shear are accounted for on the other hand none of the large scale ice divergence can be explained by the wind the long term average ocean current is estimated by subtracting the share of the ice motion caused by the wind from the total ice motion

flow variability at the continental shelf break of the mackenzie shelf in the beaufort sea observations from four yearlong current meter deployments made in 1987 1988 near the shelf break in the canadian beaufort sea are analyzed by statistical and spectral methods to characterize the structure and variability vertical and horizontal of the velocity field and to compare measurements obtained during summer ice free and winter ice covered conditions three main frequency bands are defined low frequencies 0 01 0 07 cpd intermediate or synoptic scale frequencies 0 07 0 7 cpd and high frequencies 0 7 cpd including tides and inertial currents within this division about 65 of the kinetic energy is in the low frequency band 15 in the intermediate band and 20 is in the high frequency band the latter is dominated by tidal motions low frequency variability is well correlated both vertically and horizontally along the shelf for separation distances exceeding 200 km variability in this band appears to be related to wind forcing and topographic wave propagation over large horizontal scales low frequency variability is highest during october and november in association with the occurrence of intense autumn storms and lowest during periods of ice cover due to wind shielding and increased frictional damping by ice cover intermediate scale motions have significant correlation in the vertical but poor correlation in the horizontal motions in this frequency band appear to be associated with mesoscale eddies advected by the mean flow there is also evidence of local generation of intermediate frequency current fluctuations by storms in late autumn and again an apparent damping during winter periods of ice cover finally high frequency motions show significant peaks in diurnal and semidiurnal tidal bands which are well correlated horizontally and vertically however other high frequency motions in this band show no significant correlation in either the vertical or horizontal direction there is no clear evidence in the current meter records of coupling between high frequency motions and direct atmospheric forcing

circulation mixing and production of antarctic bottom water abstract the antarctic source of bottom water to the abyssal layer of the world ocean is examined as well as its large scale flow pattern and ultimate entrainment rate into the deep water above we make use of the available high quality station data in the southern ocean to construct bottom maps of neutral density and mean property maps including chlorofluorocarbon cfc for the abyssal layer underneath a selected neutral density surface the maximum density at the sill depth of drake passage is used to distinguish between the voluminous deep water mass that is a continuous component of the antarctic circumpolar current from the relatively denser bottom water originated along the antarctic continental margins based on water density antarctic bottom water aabw is defined here generically to include all volumes of non circumpolar water of antarctic origin over the shelf regime multiple localized sources of specific aabw types contribute to the abyssal layer of the adjacent antarctic basins characteristics of these dense bottom waters reflect closely those observed on the parent shelf water mass spreading paths of newly formed deep and bottom waters over the slope regime and their subsequent oceanic circulation patterns are analyzed on the basis of global property maps for the aabw layer interior mixing and interbasin exchanges of aabw are deduced from mean characteristic curves following the southern streamline of the antarctic circumpolar current outflow and mixing of aabw from the weddell sea to the argentine basin is depicted using density and cfc distributions of two zonal hydrographic lines recirculation and mixing of deep and bottom waters within the weddell gyre are also detailed using a meridional section along the greenwich meridian the strength of all localized sources of aabw combined is estimated by two independent approaches an estimate of the total production rate of aabw is calculated based on the oceanic cfc budget for the aabw layer offshore of the 2500 m isobath the sum of all downslope inputs of well ventilated bottom water types underneath the top isopycnal must account for the measured cfc content in the bottom layer the resulting total aabw production rate is about 8 sv which is a conservative figure that neglects the loss of cfc bearing waters across the top isopycnal in recent years whereas about 9 5 sv is calculated assuming a well mixed bottom layer making use of their transient nature cfc distributions at the top of the aabw layer indicate that more direct and rapid entrainment of cfc rich bottom waters below occurs over localized areas with relatively strong upwelling rates and enhanced vertical mixing a second more ad hoc but independent oceanic mass budget of the bottom layer is also constructed a typical basin wide rate of deep upwelling of 3 10 7 m s 1 requires 10 sv 1 sv 106 m3 s 1 of newly formed aabw to sink down the slope around antarctica we have also formulated a spatial distribution of deep upwelling on the isopycnal at the top of the aabw it is expressed as a combination of wind topographic and turbulent components which in turn are functions of the isopycnal depth bottom depth and bottom layer thickness this non uniform upwelling field yields about 12 sv of aabw exported across the top isopycnal fortuitously the overall average of upward speed at the top isopycnal 3 7 10 7 m s 1 compares well with previous estimates of deep upwelling in the northern basins a series of likely sites for strong vertical entrainment of aabw are clearly identified in the modeled distribution of deep upwelling consonant with the observed cfc distributions on the top isopycnal altogether regions with relatively high upwelling rates 5 10 7 m s 1 occupy only a quarter of the total areal extent of the top isopycnal but they account for as much as 45 of the total vertical transport

comparison of near surface mean and eddy flows from two numerical models of the south atlantic ocean the near surface mean and eddy flows simulated by two eddy permitting models of the south atlantic s coordinate primitive equation model spem and ocean parallel opa model are compared these models are intrinsically different by virtue of their vertical discretizations versus geopotential coordinates respectively so that their solutions differ essentially through the representation of current topography interactions the path of the agulhas current the generation process the characteristics and the subsequent trajectory of the agulhas rings are differently affected by topography in the two models along the american western boundary spem traps a larger part of the antarctic circumpolar current acc around the falkland plateau and consequently produces a stronger malvinas current which overshoots far to the north inshore of a rather realistic brazil current and confluence regime in contrast opa allows a large part of the acc to flow across the scotia sea produces a weaker malvinas current traps the brazil and malvinas currents along the american coast and tends to distort the complex dynamics of the confluence region and the zapiola anticyclone some of these differences can be attributed to the particularities of each vertical coordinate system and to the representation of topographic slopes staircases in opa and facettes in spem more generally the topographic constraint trapping of boundary currents and interaction of mean and eddy flows with bathymetry is stronger in spem than in opa the topographic smoothing usually performed in sigma coordinate models removes mesoscale topographic roughness and reduces topographic slopes this treatment is probably responsible for several of the differences observed in the numerical solutions

surface airflow around windless bight ross island antarctica ross island antarctica is located along the transantarctic mountains and is subjected to a strong southerly mountain parallel wind regime despite this windless bight on the island s southern coast is a region of anomalous calm the atmospheric boundary layer dynamics that gives rise to this phenomenon is analysed both theoretically and observationally it is the strong static stability of the boundary layer air encountering the high steep topography of ross island that causes a stagnation zone resulting in the calm conditions of windless bight direct and proxy observations of boundary layer winds provide a detailed description of airflow around the island the anomalous with respect to the synoptic pressure field but persistent north easterly winds at scott base are due to the deflection of highly stable low level air around hut point peninsula by contrast the less frequent strong southerly winds which override the peninsula are associated with the influx of warm maritime air from cyclonic systems to the east it is inferred that flow of air around the terrain of ross island gives rise to locally strong winds these are responsible for the ice breakout and polynya occurrences in mcmurdo sound the surface airflow past ross island can be modelled by a two dimensional steady frictionless irrotational incompressible flow past an obstacle with a shape based on an island height contour the flow is assumed to separate from the eastern and western sides of the island and form a wake downstream a solution for this flow is presented based on potential theory for streaming motion past an obstacle the streamline and isobar patterns clearly depict the stagnation region in windless bight for approaching winds of 20 ms 1 the local pressure field is perturbed by several millibars

determining the strength of the deep western boundary current using the chlorofluoromethane ratio abstract the dilution of a passive tracer during deep water formation and the subsequent advection mixing in a deep boundary current is modeled with application to chlorofluoromethanes cfms in the north atlantic two different types of boundary currents are considered a uniform flow and a simple shear flow in each case the core of the flow mixes with surrounding water which continually accumulates cfms in an extreme case the coupled systems predicts that the cfm ratio in the current is unaltered from the ratio of its source water save for a time lag more realistic cases however suggests that the ratio is not a conserved quantity but is substantially altered in both the overflow basin and boundary current matching the model results to cfm data collected near the grand banks gives a predicted average core speed of 5 10 cm s 1 for the deep western boundary current and provides a constraint on the transport and diffusivity of the flow as well

identification of surface wind patterns over the ross ice shelf antarctica using self organizing maps abstractthe interaction of synoptic and mesoscale circulations with the steep topography surrounding the ross ice shelf antarctica greatly influences the wind patterns in the region of the ross ice shelf the topography provides forcing for features such as katabatic winds barrier winds and barrier wind corner jets the combination of topographic forcing and synoptic and mesoscale forcing from cyclones that traverse the ross ice shelf sector create a region of strong but varying winds this paper identifies the dominant surface wind patterns over the ross ice shelf using output from the weather research and forecasting model run within the antarctic mesoscale prediction system and the method of self organizing maps som the dataset has 15 km grid spacing and is the first study to identify the dominant surface wind patterns using data at this resolution the analysis shows that the ross ice shelf airstream a dominant stream of air flowing northward from the interior of the continent over the western

a case study of a ross ice shelf airstream event a new perspective abstract a case study illustrating cloud processes and other features associated with the ross ice shelf airstream ras in antarctica is presented the ras is a semipermanent low level wind regime primarily over the western ross ice shelf linked to the midlatitude circulation and formed from terrain induced and large scale forcing effects an integrated approach utilizes moderate resolution imaging spectroradiometer modis satellite imagery automatic weather station aws data and antarctic mesoscale prediction system amps forecast output to study the synoptic scale and mesoscale phenomena involved in cloud formation over the ross ice shelf during a ras event a synoptic scale cyclone offshore of marie byrd land draws moisture across west antarctica to the southern base of the ross ice shelf vertical lifting associated with flow around the queen maud mountains leads to cloud formation that extends across the ross ice shelf to the north the low level cloud has a warm signature in thermal infrare

modeling winds and open water buoy drift along the eastern beaufort sea coast including the effects of the brooks range the united states coast guard deployed a cluster of satellite transmitting surface drifting buoys in the beaufort sea north of prudhoe bay alaska on august 17 1983 the surface currents in this coastal area are predominantly wind driven an unusual stand of westerly winds led to eastward drift with the surviving buoys moving into mackenzie bay canada by mid september the buoy motion suggested that they were driven by the geostrophic wind modified by the orographic umbrella of the brooks range this mesoscale effect can create changes in wind direction and regions of super and subgeostrophic speeds it influenced an arcuate zone at least 50 km seaward of the coast from camden bay alaska to mackenzie bay a simple model was developed to predict the wind modifications and resultant wind driven buoy drift the model s initial wind velocity input is a calculated geostrophic wind derived from triangular shaped mesoscale atmospheric pressure network data these networks were chosen because their boundaries alternately contained the trajectories of the eastward moving buoys the model then used this network velocity to generate an orographically modified wind field at buoy locations in offshore areas north of the brooks range the actual buoy drift during the open water season covered approximately 650 km in 60 days with the final model predicted buoy drift position in error by less than 50 km the brooks range influence did not appear to affect the october buoy drift which was north of richards island canada above 70 n and east of 135 n

anthropogenic co2 estimates in the southern ocean storage partitioning in the different water masses the research leading to these results was supported through eu fp7 project carbochange changes in carbon uptake and emissions by oceans in a changing climate which received funding form the european commission s seventh framework under grant agreement no 264879 and by the spanish ministry of sciences and innovation and was co founded by the fondo europeo de desarrollo regional 2007 2012 feder through the catarina project ctm2010 17141 mar

abyssal water carbon 14 distribution and the age of the world oceans the carbon 14 distribution in the abyssal waters of the world oceans indicates replacement times for pacific indian and atlantic ocean deep waters more than 1500 meters deep of approximately 510 250 and 275 years respectively the deep waters of the entire world ocean are replaced on average every 500 years

on the total input of antarctic waters to the deep ocean a preliminary estimate from chlorofluorocarbon measurements 1 deep ocean inventories of dissolved chlorofluorocarbon 11 cfc 11 along representative sections off antarctica provide the first estimate of the overall strength of all dense water sources in the southern ocean their formation rates are reported for three density layers that span the main water masses involved in the lower limb of the thermohaline circulation thc the bottom layer is supplied via sinking of antarctic bottom water aabw produced at a few continental shelves the middle layer receives the offshore injection of ventilated modified circumpolar deep water mcdw produced along much of the lengthy antarctic slope front the top layer is ventilated by northward export of antarctic surface water into the upper circumpolar deep water of the antarctic circumpolar current average southern ocean inputs to the upper two layers of the deep ocean for the 1970 1990 period are derived on the basis of the cfc 11 distributions along meridional sections the mean cfc 11 saturations of all water mass ingredients and the inferred mixing leading to production of dense source waters about 5 4 1 7 sv 1 sv 10 6 m 3 s 1 of near freezing shelf water ventilate the bottom layer and 4 7 1 7 sv and 3 6 1 3 sv of cold antarctic surface water ventilate the middle and top layers therefore the total contribution of ventilated southern ocean waters to the lower limb of the global thc is about 14 sv this is close to the about 17 sv estimated for north atlantic near surface sources from cfc 11 inventories their entrainment of 7 4 2 4 sv of cfc poor subsurface lower circumpolar deep water during the formation and sinking of aabw and mcdw raises the total southern ocean input to the deep ocean to about 21 sv

numerical simulation of northern hemisphere sea ice variability 1951 1980 the dynamic thermodynamic sea ice model of hibler 1979 is used to simulate northern hemisphere sea ice growth drift and decay over a 30 year period 1951 1980 the model is run with a daily time step and is forced by interannually varying fields of geostrophic wind and temperature derived thermodynamic fluxes the results include documentation of the sensitivities to the source of the thermodynamic forcing data and to the number of thickness levels in the thermodynamic formulation the fields of ice velocity and thickness show strong seasonal as well as interannual variability the pacific gyre is found to be well developed in spring and autumn but less so in winter and summer the mean drift pattern results in thicknesses of 4 5 m offshore of northern canada and greenland while winter thicknesses of 2 m are typical of the alaskan and eurasian coastal waters annual net growth ranges from 0 1 to 0 6 m over much of the arctic basin and baffin bay to over 1 0 m in the eastern bering sea annual net melt of 0 5 1 5 m occurs in the western bering sea and the north atlantic marginal ice zone no significant temporal trends are detectable in the total mass of simulated ice the simulated interannual fluctuations in 20 longitudinal sectors correlate at 0 4 0 9 with corresponding observed fluctuations during 1961 1976 the correlations are smaller when dynamics are omitted from the model the simulated velocities show no bias but considerable scatter relative to the drift of the arctic buoys in 1979 and 1980 an analysis of the regional mass budgets shows that the normal seasonal cycle is controlled primarily by the thermodynamic processes but that the thickness anomalies in much of the arctic are attributable primarily to dynamic processes during winter spring and autumn thermodynamic processes contribute more strongly to summer anomalies and to anomalies near the ice edge the tendency for ice anomalies to be advected by the pattern of mean drift is apparent in multiseason lag correlations involving subregions of the arctic basin and the peripheral seas the simulated outflows of ice mass through the fram and bering straits vary by factors of 2 3 in successive years the simulated outflow in the fram strait is 20 30 smaller when ocean currents are omitted from the model

initial model results for arctic mixed layer circulation under a refreezing lead at the temperatures in the arctic ocean mixed layer during lead induced surface water cooling convection is primarily salinity controlled owing to continuous brine expulsion from newly forming ice a nonlinear time dependent convective model has been developed that simulates existing field data obtained on the circulation characteristics under and near a refreezing lead the model uses typical arctic ocean ambient conditions as initial input and allows for imposition of varying geostrophic currents the zero geostrophic current free convective case model output for typical lead surface salt input resulted in maximum horizontal current velocities of 0 05 m s 1 eddy viscosities on the order of 0 01 m2 s 1 average salt fluxes beneath the lead of 3 3 10 5 kg m 2 s 1 and a subsequent increase in the depth of the mixed layer the circulation cells are symmetric with respect to the lead axis imposition of a cross lead constant geostrophic current shows a resultant circulation cell asymmetry associated with increased salt advection in a forced convective regime

are diamond bearing cretaceous kimberlites related to low angle subduction beneath western north america abstract diamond bearing cretaceous kimberlites of western north america were emplaced 1000 1500 km inboard of the farallon plate subduction margin and overlap with the development of the western interior seaway shut down of the sierra nevada arc and the laramide orogeny these events are consistent with a decrease in subduction angle along much of the margin which placed the subducted farallon plate in close proximity to the continental interior at the time of kimberlite magmatism our numerical models demonstrate that low angle subduction can result from high plate convergence velocities and enhanced westward motion of north america further rapid subduction allows hydrous minerals to remain stable within the cool interior of the subducting plate to more than 1200 km from the trench destabilization of these minerals provides a fluid source that can infiltrate the overlying material potentially triggering partial melting and kimberlite lamproite magmatism

ice drift and regional meteorology in the southern bering sea results from mizex west in february 1983 a multifaceted study of the air ice ocean interaction was made in the southern bering sea the study mizex west addressed a broad spectrum of physical problems related to the bering sea marginal ice zone miz as a part of that study an array of eight argos tracked floes on a scale of 50 km provided information on the mesoscale behavior of the ice pack wind and current measuring platforms on two of the floes gave detailed information on the forces on individual floes which were compared with the larger scale motions under relatively steady northeast winds and with weak or negligible regional currents the floes accelerated considerably as they crossed the miz the array showed little distortion even though it skirted around st matthew island and changed trajectory direction by over 90 during the 12 day study period similarly individual floes remained within 20 of their original orientation although their angular motions were erratic and often rapid a baroclinicly forced acceleration of the wind over the miz contributed to floe acceleration the relative currents at 2 and 6 m under the ice were highly variable and random in time although well correlated in depth one of the floes was much smoother than the other and higher winds and currents were noted at the smoother floe the motion of the floes reflect strong coupling to the currents at tidal and lower frequencies and low frequency greater than 6 hours response to the wind both floes drifted to the right of the mean wind by approximately 30 at about 4 of the wind speed at 3 m and relative wind and current directions were within 20 of being colinear traits that are consistent with free drift hypothesis using quadratic drag representations for wind and current stress the near colinearity allowed calculation of the ratio of the air ice to ice water drag coefficients ca cw relative to measurement heights of 3 m and 2 m for the rough floe this ratio changed in mean from 0 06 to 0 2 in its movement to the miz for the smooth floe the variation in the ratio was less from 0 14 to 0 2 however for the rough flow the angle between wind and current was generally less than 180 and for the smooth flow it was greater it is possible that another type of drag related to the bow effect of the floe pushing through the water can account for this observation finally the motion of the ice floes and ice edge are compared by examination of satellite photos two regions of the ice pack one thick with rafting and rubble one thin and broken showed a ratio of edge velocity to floe velocity of 0 64 and 0 43 respectively thinner ice overtakes the edge and melts more rapidly than the thicker ice a simple thermodynamic model explains this observation

chlorofluoromethanes in the northeast pacific ocean measured vertical distributions and application as transient tracers of upper ocean mixing the vertical distributions of the man made chlorofluoromethanes ccl3f f 11 and ccl2f2 f 12 have been measured at two locations in the eastern north pacific ocean to depths greater than 500 m at both sites 46 n 125 w off the washington oregon coast and 50 n 140 w in the gulf of alaska the halomethane concentrations were found to fall off exponentially with increasing depth below the mixed layer for f 11 at 50 n the surface concentration 3 2 10 12 mol l was found to be in saturation equilibrium with the measured atmospheric concentration 190 pptv the measured chlorofluoromethane profiles have been interpreted in terms of a one dimensional model for the vertical diffusion advection of an exponentially driven conservative tracer into a bottomless ocean in the appropriate limit of transient steady state the projected profiles are simple exponentials described by an advective diffusive scale depth h which is a function of the vertical eddy diffusivity kz the upwelling velocity w and the characteristic time for the exponential growth of the tracer concentration at the boundary at the two ocean locations studied the freon thermocline depth scales were in the range h 120 140 m with f 12 generally 10 20 deeper than f 11 at 50 n the f 11 and f 12 vertical profiles gave consistent values of vertical diffusivity kz 1 2 1 3 cm2 s 1 and upwelling velocity w 12 14 m yr 1 the model also allows a simple scaling from one exponentially driven transient tracer freon to another fossil fuel co2 leading to a predicted mean depth of penetration of fossil fuel co2 of approximately 300 m in the eastern north pacific

scale analysis of marine winds in straits and along mountainous coasts abstract the complicated wind regimes in straits which develop in response to different large scale pressure fields are investigated by scale analysis of the equations of motion adjustment of the mass and motion fields in straits o los km in width is governed by four nondimensional numbers separate along and cross strait rossby numbers a strait drag coefficient and a stratification parameter which relates the internal rossby radius of deformation to the width of the strait the wind field is in approximate geostrophic balance with an imposed cross channel pressure gradient an along channel pressure gradient is primarily balanced by ageostrophic acceleration of the wind field down the axis of the strait the gap wind vertical motion and the accompanying horizontal divergence in the near surface wind field can be large even for moderately stable stratification as a consequence there may be particularly abrupt transitions of the surface wind field at the exits of straits where there is a rapid c

case study of a barrier wind corner jet off the coast of the prince olav mountains antarctica abstractthe ross ice shelf airstream ras is a barrier parallel flow along the base of the transantarctic mountains previous research has hypothesized that a combination of katabatic flow barrier winds and mesoscale and synoptic scale cyclones drive the ras within the ras an area of maximum wind speed is located to the northwest of the protruding prince olav mountains in this region the sabrina automatic weather station aws observed a september 2009 high wind event with wind speeds in excess of 20 m s 1 for nearly 35 h the following case study uses in situ aws observations and output from the antarctic mesoscale prediction system to demonstrate that the strong wind speeds during this event were caused by a combination of various forcing mechanisms including katabatic winds barrier winds a surface mesocyclone over the ross ice shelf an upper level ridge over the southern tip of the ross ice shelf and topographic influences from the prince olav mountains these forcing mechanisms induced a b

the role of fluorine and oxygen fugacity in the genesis of the ultrapotassic rocks the effects of h2o co2 ch4 and hf on partial melting of a model phlogopite harzburgite mantle are considered with regard to the production of ultrapotassic magmas fluorine has a polymerising effect in h2o poor conditions but in the presence of abundant h2o where hf rather than f is dominant the overall effect is depolymerisation methane also dissolves by forming oh groups and so has a depolymerising effect group i ultrapotassic rocks lamproites probably originate from primary magmas with sio2 contents ranging from around 40 wt to at least 52 wt this range can be explained by differing depths of origin from a similar source with a similar reduced h2o ch4 hf volatile mixture the formation of silica rich initial melts from a model phlogopite harzburgite is assisted by the presence of ch4 and hf dissociation of less than 0 1 wt h2o driven by h2 loss is sufficient to cause oxidation during emplacement to observed oxidation states silica poor ultrapotassic rocks could be produced at higher pressures in a reduced environment or in an oxidised environment with high co2 co2 h2o ratios

a high pressure experimental study on a magnesian rich leucite lamproite from the west kimberley area australia petrogenetic implications liquidus and subliquidus phase relations of a leucite lamproite wolgidite from the west kimberley area australia have been studied experimentally under the volatile conditions of 3 22 wt h2o x co 2 0 11 and 13 0 wt h2o x co 2 0 03 between 10 to 40 kbar under these conditions liquids are vapour undersaturated in experiments with 13 0 wt h2o olivine is the liquidus phase up to 24 kbar and orthopyroxene above 24 kbar phlogopite and rutile occur close to the liquidus above 16 kbar crystallization temperatures of clinopyroxenes are 50 120 c below the liquidus

mineralogy of the tk1 and tk4 kimberlites in the timmasamudram cluster wajrakarur kimberlite field india implications for lamproite magmatism in a field of kimberlites and ultramafic lamprophyres abstract a mineralogical study of the hypabyssal facies late cretaceous macrocrystic pulse of tk1 intrusion and the mesoproterozoic aphanitic pulse of tk4 intrusion in the wajrakarur kimberlite field of southern india shows that the rocks contain macrocrysts of forsteritic olivine phenocrysts and microphenocrysts of al na poor diopside and phlogopite set in a groundmass mainly of al na poor diopside and phlogopite other groundmass minerals are spinel perovskite and fluorapatite in tk1 and spinel titanite chlorite calcite and gittinsite in tk4 k richterite and perovskite occur only as inclusions in phlogopite and titanite respectively in tk4 late stage deuteric phases include pyrite and barite in tk1 and strontianite chalcopyrite galena and pentlandite in tk4 diopside microphenocrysts in tk4 exhibit oscillatory zoning with characteristics of diffusion controlled magmatic growth tk1 spinels show magmatic trend 2 that evolves from magnesiochromite and culminates in titaniferous magnetite whereas tk4 spinels are less evolved with magnesiochromite composition only tk1 phlogopites show a simple compositional trend that is typical of lamproite micas while four distinct growth zones are observed in tk4 phlogopites with the following compositional characteristics zone i high cr 2 o 3 and tio 2 and low bao zone ii low cr 2 o 3 zone iii low tio 2 and high bao zone iv low bao forsterite contents and trace element concentrations reveal two xenocrystic core populations and one magmatic rim population for tk1 olivines mineralogically both tk1 and tk4 are classified as diopside phlogopite lamproites rather than archetypal kimberlites the two lamproites are considered to have formed from the same parent magma but crystallised under distinct oxygen fugacity conditions with elevated content of fe 3 in phlogopite spinel and perovskite tk1 appears to have crystallised in a relatively high oxygen fugacity environment multiple growth generations of phlogopite spinel and fluorapatite in tk4 indicate a complex evolutionary history of the magma close spatial and temporal associations of mesoproterozoic kimberlites and lamproites in southern india can possibly be explained by a unifying model which accounts for the generation of diverse magmas from a range of geochemical resevoirs in a continental rift setting

mineralogy and petrology of cretaceous subsurface lamproite sills southeastern kansas usa cores and cuttings of lamproite sills and host sedimentary country rocks in southeastern kansas from up to 312 m depth were analyzed for major elements in whole rocks and minerals certain trace elements in whole rocks including the ree and sr isotopic composition of the whole rocks the lamproites are ultrapotassic k2ona2o 2 0 19 9 alkalic molecular k2ona2o al2o3 1 3 2 8 enriched in mantle incompatible elements light ree ba rb sr th hf ta and have nearly homogeneous initial sr isotopic compositions 0 707764 0 708114 these lamproites could have formed by variable degrees of partial melting of harzburgite country rock and cross cutting veins composed of phlogopite k ti richterite titanite diopside k ti silicates or k ba phosphate under high h2oco2 ratios and reducing conditions variability in melting of veins and wall rock and variable composition of the metasomatized veins could explain the significantly different composition of the kansas lamproites least squares fractionation models preclude the derivation of the kansas lamproites by fractional crystallization from magmas similar in composition to higher silica phlogopite sanidine lamproites some believe to be primary lamproite melts found elsewhere in all but one case least squares fractionation models also preclude the derivation of magmas similar in composition to any of the kansas lamproites from one another a magma similar in composition to the average composition of the higher sio2 ecco ranch lamproite 237 5 247 5 m depth could however have marginally crystallized about 12 richterite 12 sanidine 7 diopside and 6 phlogopite to produce the average composition of the guess lamproite 305 312 m depth lamproite from the ecco ranch core is internally fractionated in k2o al2o3 ba mgo fe2o3 co and cr most likely by crystal accumulation removal of ferromagnesian minerals and sanidine in contrast the guess core 305 312 m depth has little fractionation throughout most of the sill except in several narrow zones lamproite in the guess core has large enrichments in tio2 ba ree th ta and sc and depletions in mgo cr co and rb possibly concentrated in these narrow zones during the last dregs of crystallization of this magma the ecco ranch sill did not show any evidence of loss of volatiles or soluble elements into the country rock this contrasts to the previously studied shallow silver city lamproite which did apparently lose h2o rich fluid to the country rock perhaps a greater confining pressure and lesser amount of h2o rich fluid prevented it from escaping

the water masses along the western boundary of the south and equatorial atlantic a quasi meridional hydrographic section located offshore from south america from 50 s to 10 n and three shorter transverse lines to the continental slope are used for a descriptive study of the water masses along the western boundary of the south and equatorial atlantic at the upper and intermediate levels the tracer analysis provides geographical limits of the wind driven circulation regimes and a comparison of the tracer values at the continental slope and along the meridional section shows where the boundary currents originate at depths shallower than about 200 m the subdivision of the subtropical gyre into two cells separated by the subtropical countercurrent near 28 s that was pointed out in a previous study is corroborated south of this front a warm variety 18 c of subtropical mode water in the inner recirculation of the brazil current appears despite its limited extent as a southern counterpart of the north atlantic 18 c water at the deep levels the upper circumpolar water and upper north atlantic deep water enter the south atlantic in a significantly overlapping density range the ensuing lateral encounter of both water masses occurs at 26 s near the western boundary where most of the boundary flow of the latter water is stopped and deflected seaward by the base of the subtropical gyre other tracer anomalies signal significant eastward escapes of north atlantic deep water within two jets at about two degrees of latitude on either side of the equator in another narrow current at 10 s and at 34 s the latter latitude marks the confluence and eastward deflection of the opposite boundary currents of lower north atlantic deep water and lower circumpolar water near the bottom of the argentine basin the weddell sea deep water that flows westward north of the zapiola ridge is more recently ventilated than the water carried by the boundary current near the falkland escarpment while a part of it flows anticyclonically around the ridge another part turns equatorward and enhances the southern property signatures of the water farther north

southern ocean winter mixed layer austral winter 1986 observations from the polarstern along the greenwich meridian from the ice edge to the antarctic margin show the mixed layer beneath the winter sea ice cover to be significantly depressed in oxygen saturation incorporation of weddell deep water wdw into the winter mixed layer responsible for this undersaturation also introduces heat and salinity into the surface layer which strongly influences the mixed layer sea air exchanges and sea ice formation processes the total wdw transfer into the mixed layer averages 45 myr 1 implying a residence time for the surface water of 2 5 years the associated winter heat flux is 41 w m 2 which limits ice thickness to about 0 55 m agreeing quite well with observations the air temperatures during the cruise are just sufficient to remove the wdw heat input in the presence of observed ice thickness and concentration this suggests that the sea ice cover and wdw heat input into the mixed layer are in approximate balance by midwinter the annual heat flux from wdw to the surface layer and hence into the atmosphere is estimated as 16 w m 2 extrapolation of the greenwich meridian wdw entrainment value to the full circumpolar 60 70 s belt yields total up welling of 24 106 m3 s 1 similar extrapolation of the heat flux value gives a circumpolar total of 2 8 1014 w as a consequence of circulation topography interaction the maud rise water column stands out as an anomaly relative to the surrounding region with a significantly more saline and dense mixed layer below the mixed layer the water column over the crest of the rise is identical to that over the flanks if the latter water column is upwelled by 400 m this uplifting is believed to be a response of the upstream flow encountering the rise increased upstream flow would be expected to increase maud rise upwelling and the dependent salinity density of the mixed layer slight increases in the mixed layer density could trigger a convective mode and generation of a polynya it is hypothesized that spin up of the weddell gyre s barotropic circulation induced by an increase of the regional wind stress curl would enhance the probability of polynya development over maud rise

atmospheric boundary layer structure and drag coefficients over sea ice this paper estimates the air sea drag coefficient for first year ice from recent aircraft measurements and reconciles the range of observed drag coefficients 103cd 1 2 3 7 referenced to 10 m for all sea ice types based on ice roughness and seasonal meteorology for the purpose of sea ice modeling it is necessary to define an effective drag coefficient which relates regional stress to regional wind because sea ice is heterogeneous on scales less than 20 km regional stress is influenced by the distribution of surface roughness the buoyancy flux from quasi periodic leads and external atmospheric conditions principally the inversion height 103cd is 1 3 1 5 for smooth ice but is much greater for nonflat surfaces for wind speeds greater than 5 m s and air temperatures below freezing the effective 103cd is 2 5 3 0 for nearly continuous pack ice such as first year ice in seasonal ice zones and central arctic basin the range of values of 103cd is 3 0 3 7 for unstable boundary layers typical of off ice winds in the marginal ice zone miz or even greater if the ice has been broken by a recent storm cd values at the lower end of these ranges are associated with low inversion heights these coefficients are confirmed by 103cd of 2 9 2 5 and 3 1 for first year sea ice calculated from gust probe data collected by the noaa p 3 aircraft interior to the inner miz in the bering sea during the marginal ice zone experiment mizex west in february 1983 and 103cd of 2 6 for the arctic calculated from arctic ice dynamics joint experiment aidjex aircraft data for february 1976 the effective drag coefficient with the presence of even a small concentration of sea ice is greater than the oceanic value as shown by a 103cd of 2 2 calculated from noaa p 3 gust probe data over a 40 km track of 0 4 ice concentration in the outer miz of the greenland sea in june 1984 during mizex 84 the relation of surface wind and stress to the geostrophic wind for shallow inversion heights typical of high latitudes is reviewed with a turbulent closure atmospheric boundary layer model the winter arctic is typified by low inversions 100 m low geostrophic drag coefficients and large geostrophic surface wind turning angles with low functional dependence on surface roughness seasonal ice zones are typified by a more modest influence of the inversion on boundary layer characteristics

the stratification and water masses at drake passage the waters at drake passage are known to be separated horizontally into four distinct zones of relatively small geostrophic shear by three fronts in which the shear and eastward flow are large the two northern fronts subantarctic front and polar front that bound the polar frontal zone comprise most of the transport of the antarctic circumpolar current vertical sections of closely spaced 50 km oceanographic stations made across drake passage in the summers of 1975 and 1976 produced quality measurements of temperature salinity oxygen silicate nitrate and phosphate based on these data a traditional description of characteristic distributions is presented good sampling resolution in the vertical allows maxima in hydrostatic stability to be traced laterally approximately along isopycnals between individual stations eleven strata of maximum stability are identified most vertically separate distinct water masses the most pronounced stability stratum is associated with the seasonal pycnocline north of the polar front it separates the subantarctic surface waters from subantarctic mode water to the south of the polar front the seasonal pycnocline is found slightly above the temperature minimum characteristic of the antarctic surface waters in austral summer this stability stratum extends northward near the base of the subantarctic mode water another stability stratum extending across the entire passage forms the upper boundary for the circumpolar deep water south of the polar front this stratum is at the base of the antarctic surface water to the north it is the lower boundary of the antarctic intermediate water although subantarctic mode water and antarctic intermediate water are separated by a stability stratum north of the polar front there is no such separation between antarctic intermediate water and the temperature minimum of the antarctic surface water south of the front this suggests that subantarctic mode water and antarctic intermediate water are distinct and that the latter derives from the surface waters south of the polar front at greater depths a horizontally discontinuous stratum is found between the upper and lower circumpolar deep water two horizontally continuous stability strata are found near the base of the circumpolar deep water marking the transition to a high silicate variety of denser deep water from the southeast pacific basin the densest water mass found is weddell sea deep water which flows through a gap in the south scotia ridge and along the southern scotia sea to fill the trough in the southern drake passage it is overlain by a laterally continuous stratum of relative maximum stability

a chlorofluoromethane and hydrographic section across drake passage deep water ventilation and meridional property transport new hydrographic and nutrient data obtained on a section across drake passage f s meteor january 1990 world ocean circulation experiment hydrographic program section s1 are in close agreement with property sections reported previously the chlorofluoromethanes cfm 11 and cfm 12 were measured in drake passage for the first time cfm concentrations are found to decrease from the surface down into the upper circumpolar deep water for which they confirm water renewal from the south for the lower circumpolar deep water in which cfm concentrations were above detection limit only south of the polar front very little water renewal on the cfm time scale is implied nonvanishing cfm is again found in the weddell sea deep water and the southeast pacific deep water toward the bottom in the south but recent ventilation for the latter water mass is rejected cfm 11 and cfm 12 concentrations vary essentially in constant proportion down to very low concentrations questioning the possibility of using cfm ratios as age markers the observed ratios are shown to be a natural feature of the upwelling regime of the southern ocean property concentrations on isopycnal surfaces display large undulations reaching down into the upper circumpolar deep water their extrema due to varying contribution of young water of southern origin are situated at the boundaries of the current bands of the antarctic circumpolar current the feature is ascribed to property advection by rings and is taken to support previous claims that rings are an important transport mechanism across the antarctic circumpolar current and that they might assist in maintaining its fronts

diapycnal and isopycnal transports in the southern ocean estimated by a box inverse model quantitative descriptions of circumpolar deep water upwelling and evolution into a lighter mode and heavier bottom waters in the southern ocean are still not well constrained here data from two occupations of eight hydrographic sections are combined and used in a box inverse model to estimate isopycnal and diapycnal transportsinthesouthernocean amixedlayerboxallowsdiapycnaltransportsinthesurfacemixedlayertobe estimated separately current velocity at 1000 dbar was constrained by the mean velocity field estimated from subsurfacefloatdriftdata theestimatedisopycnaltransportsarelargelyconsistentwithpastestimatesandwith outputs of three ocean general circulation models the estimated subduction and upwelling at the base of the southernoceanmixedlayershowthatuppercircumpolardeepwaterupwells 16615and17621sv where 1sv 10 6 m 3 s 21 by different inversion methods and evolves into heavier lower circumpolar deep water 5 6 13 and 6 6 18sv and bottom water 86 9a nd 86 13sv or lighter mode and intermediate waters 96 18 and 13 6 24sv meridional transport in the surface mixed layer is due to northward ekman transport and mostly southward eddy transport in seasonal ice covered areas near antarctica a significant 14 6 14sv southward transport was found the southward eddy transport is largest north of the antarctic circumpolar currentanddecreasespolewardbecauseofthepolewarddecreaseintheeddydiffusivity theinteriordiapycnal transports which can be either upward gaining buoyancy or downward gaining density are comparable in magnitude to the horizontal diapycnal transports within the surface mixed layer

geochemistry and petrogenesis of lamproites late cretaceous age woodson county kansas u s a abstract lamproite sills and their associated sedimentary and contact metamorphic rocks from woodson county kansas have been analyzed for major elements selected trace elements and strontium isotopic composition these lamproites like lamproites elsewhere are alkalic molecular k 2 o na 2 o al 2 o 3 1 6 2 6 are ultrapotassic k 2 o na 2 o 9 6 150 are enriched in incompatible elements lree or light rare earth elements ba th hf ta sr rb and have moderate to high initial strontium isotopic compositions 0 7042 and 0 7102 the silica saturated magma olivine hypersthene normative of the silver city lamproite could have formed by about 2 percent melting of a phlogopite garnet lherzolite under high h 2 o co 2 ratios in which the iherzolite was enriched before melting in the incompatible elements by metasomatism the rose dome lamproite probably formed in a similar fashion although the extreme alteration due to addition of carbonate presumably from the underlying limestone makes its origin less certain significant fractional crystallization of phases that occur as phenocrysts diopside olivine k richterite and phlogopite in the silver city magma and that concentrate co cr and sc are precluded as the magma moved from the source toward the surface due to the high abundances of co cr and sc in the magma similar to that predicted by direct melting of the metasomatized iherzolite ba and to a lesser extent k and rb and have been transported from the intrusions at shallow depth into the surrounding contact metamorphic zone the silver city lamproite has vertical fractionation of some elements due either to volatile transport or to variations in the abundance of phenocrysts relative to groundmass most probably due to flow differentiation although multiple injection or fractional crystallization cannot be conclusively rejected