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

growth and steady state stages of thermohaline intrusions in the arctic ocean thermohaline intrusions are a widespread feature of the arctic ocean pycnocline and may be important for the lateral transport of heat salt and other tracers in an attempt to understand the dynamics of the intrusions we present an analysis of hydrographic observations of a front north of svalbard following intrusions from profile to profile we find that they slope upward toward the cold fresh side of the front however their slope is less than that of the background isopycnals so that the intrusions slope between horizontal and isopycnal surfaces in the wedge of baroclinic instability our analysis proceeds in two stages first to determine what might have caused the initial growth of the intrusions we compare the observed intrusion properties with predictions of an instability theory the results suggest that the intrusions developed as a form of double diffusive interleaving with fluxes dominated by salt fingering and additional forcing by baroclinicity second to investigate the observed finite amplitude interleaving we apply a steady state model to the observations a key result is that diffusive convection not salt fingering must be the dominant form of double diffusion in order to reach steady state this fundamental change in dynamics is discussed in the context of adjustment from the growth stage to an eventual steady state

evidence for warming of atlantic water in the southern canadian basin of the arctic ocean results from the larsen 93 expedition potential temperature and salinity s data obtained along the perimeter of the southern canadian basin north of the east siberian sea in 1993 aboard the ccgs henry larsen show higher temperatures in waters of atlantic origin than in available climatological data for the canadian basin in particular a front is observed near the mendeleyev ridge which separates the cooler atlantic waters of the canada basin from the warmer atlantic waters observed in the makarov basin the front is further characterized by a change in the s slope of arctic thermocline water and by thermohaline intrusions and s reversals within the atlantic layer the idea that this warm variety of atlantic water has come recently from the eurasian basin is supported by its higher level of the tracer cfc 11

geochemical confirmation of the kula farallon slab window beneath the pacific northwest in eocene time plate tectonic models indicate subduction of the kula farallon spreading ridge and thus imply formation of the kula farallon slab window beneath western north america from late cretaceous to middle eocene time seafloor magnetic anomalies however pro vide few constraints on the configuration of the subducted ridge and the location of the slab window we use geochemical data from eocene igneous rocks to provide an estimate of the slab window s position at 50 ma contouring of the trace element ratios k 2o sio2 rb zr and ta ce for lavas of the eocene challis kamloops volcanic belt demonstrates a southward trend toward enriched geochemical character this trend is consistent with a pacific northwest position for the slab window this is supported by the presence of adak ites slab melts near the canada united states border and by ca 51 ma forearc intru sions and volcanic rocks on vancouver island that are regarded as products of ridge subduction a new reconstruction of the slab window s geometry over time indicates that its chemically defined position is kinematically viable

mixing in the west spitsbergen current abstract twenty eight profiles of temperature and salinity down to 1 km depth have been measured in the area north from the coast of svalbard to latitude 84 40 n between 0 and 32 e longitude they show atlantic waters of the west spitsbergen current entering the arctic ocean in a bifilimentary mode one filament following the coastline and the other 300 km farther north apparently following the continental shelf break the profiles show these filaments mixing into the ambient water in a series of intrusive layers which are remarkably uniform over distances of hundreds of kilometers a triple peak structure at the atlantic water maximum is the dominant oceanographic characteristic of the area with salt fingering occurring on the upper surface of the cold intrusions and indications of double diffusive exchanges through the lower surface a system or eddies or meanders is postulated as the mechanism for the production of multiple fronts allowing the intrusive layers to extend to distances much greater t

vertical mixing at intermediate depths in the arctic boundary current microstructure and hydrographic observations during september 2007 in the boundary current on the east siberian continental slope document upper ocean stratification and along stream water mass changes a thin warm surface layer overrides a shallow halocline characterized by a 40 m thick temperature minimum layer beginning at 30 m depth below the halocline well defined thermohaline diffusive staircases extended downwards to warm atlantic water intrusions found at 200 800 m depth observed turbulent eddy kinetic energy dissipations are extremely low epsilon 10 6 w m 3 such that double diffusive convection dominates the vertical mixing in the upper ocean the diffusive convection heat fluxes f dc h 1 w m 2 are an order of magnitude too small to account for the observed along stream cooling of the boundary current our results implicate circulation patterns and the influence of shelf waters in the evolution of the boundary current waters

new u pb and ar ar isotopic age constraints on the timing of eocene magmatism fort fraser and nechako river map areas central british columbia twenty three new precise eocene u pb and 40 ar 39 ar age determinations for calc alkaline volcanic rocks of the ootsa lake group and associated intrusive rocks widespread in the nechako plateau in central british columbia constrain the timing of the eocene magmatism to 53 2 47 6 ma with a local duration of as little as 2 3 million years the new dates show that magmatism in the study area is partly coeval with that responsible for the babine igneous suite newman volcanic suite 53 50 ma to the north and for the endako group 51 45 ma which overlies the ootsa lake group however locally the three magmatic suites are distinct in age and or the strata record a magmatic hiatus of as much as 7 5 million years the ages generally young from north to south 52 47 ma along the western portion of the study area the babine igneous suite newman volcanic suite represents the oldest member of this series however in the east the ootsa lake group volcanic rocks are generally older 53 51 ma the anomalously older ages may be related to the interaction of magmatism and formation of a nearby and coeval core complex which ongoing studies show was uplifted at about the same time during the eocene felsic plutonism associated with the ootsa lake group occurred between 50 5 and 47 3 ma these plutons were emplaced in an extensional setting along north northeast trending faults the new dates stratigraphic relationships and suggested correlations of eocene strata in the study area with that to the west and north require a revision of the stratigraphic nomenclature for the ootsa lake and endako groups 696

on the structure and dynamical features of intrusive layering in the eurasian basin in the arctic ocean 1 numerous conductivity temperature depth data obtained in the arctic basins are analyzed to describe structural features of intrusive layering special attention is paid to large intrusions vertical scale of 40 100 m observed in upper intermediate and deep layers depth ranges of 150 200 200 600 and 600 1000 m respectively the analysis of the intrusions is accompanied by descriptions of the frontal zones where the layering was observed based on observations detailed estimates of frontal zone parameters are presented vertical profiles of temperature and salinity are found to have a well defined sawtooth or cog shape displaying a sequence of relatively thick weak gradient layers where temperature and salinity are decreasing with depth interleaved with relatively thin high gradient sublayers where temperature and salinity are increasing with depth some hypotheses about causes responsible for cog structure existence are discussed intrusions with high amplitude anomalies in the vertical profiles of temperature and salinity are shown to be present at baroclinic fronts based on models of interleaving and data analysis the apparent vertical and lateral diffusivity in the frontal zones of the upper and deep ocean layers are estimated and the slope of unstable modes relative to the isopycnals is examined at the baroclinic front in the situation when both temperature and salinity are stably stratified

eocene melting of precambrian lithospheric mantle analcime bearing volcanic rocks from the challis kamloops belt of south central british columbia abstract potassic silica undersaturated mafic volcanic rocks form a minor portion of the predominantly calc alkaline eocene challis kamloops volcanic belt which extends from the northwestern united states into central british columbia canada their major occurrence is in the penticton group in south central british columbia where they reach a thickness of up to 500 m and form the northwestern edge of the montana alkaline province these analcime bearing rocks 53 52 ma old are typically rhomb porphyries of ternary feldspar an28ab52or20 additional phenocryst phases include clinopyroxene analcime phlogopite and rare olivine the rocks are characterized by high total alkalis particularly k2o 4 5 wt as well as by a distinct enrichment of large ion lithophile elements versus heavy rare earth elements and high field strength elements they have unusual isotopic compositions compared to most other rocks of the challis kamloops belt particularly high negative nd values and elevated but relatively uniform initial 87sr 86sr ratios 0 7065 the potassic silica undersaturated rocks overlie precambrian crust and lithosphere and were at least in part derived from ancient metasomatized subcontinental mantle lithosphere which was modified in a precambrian subduction setting the alkaline rocks of the challis kamloops belt are related to a slab window environment in particular they were formed above the southern edge of the kula plate adjacent to the kula farallon slab window whereas the montana alkaline province situated well to the southeast was formed directly above the kula farallon slab window upwelling of the hotter asthenospheric mantle may have been the thermal trigger necessary to induce melting of fertile and metasomatized lithospheric mantle

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

effect of baroclinicity on double diffusive interleaving although ocean fronts are often baroclinic existing models of double diffusive interleaving have ignored such baroclinic effects as velocity shear and horizontal density gradients to determine the importance of these effects the authors have formulated a linear instability analysis applicable to baroclinic fronts two limiting cases are considered one for fronts with strong vertical and or horizontal shear the other for fronts with weak shear in both limits double diffusive interleaving can be enhanced or suppressed by baroclinicity interleaving motion is enhanced if isopycnals rise toward the fresh side of the front conversely interleaving is suppressed if isopycnals slope downward across the front a significant result is that the salinity gradient along isopycnals is not a good indicator of interleaving strength as an example the model is applied to a mediterranean salt lens the effect of baroclinicity is significant the predicted growth rates are increased by 35 90 the large scale velocity and hydrographic fields indicate that meddy sharon lies somewhere between the high and low shear limits nevertheless the model predictions agree reasonably well with the observed interleaving characteristics

water masses and circulation in the eurasian basin results from the oden 91 expedition the oden 91 north pole expedition obtained oceanographic measurements on four sections in the nansen and amundsen basins of the eurasian basin and in the makarov basin of the canadian basin thereby proving the feasibility of carrying out a typical oceanographic program using an icebreaker in the arctic ocean the data show greater spatial variability in water structure and circulation than was apparent from previous data the results show that a clear front exists between the eurasian and canadian basins such that upper halocline water in the canadian basin is almost absent from the eurasian basin the lower halocline water produced in the barents kara sea region permeates much of the eurasian basin and flows along the continental slope into the canadian basin the deeper circulation is strongly influenced by topography three return flows of the atlantic layer are identified one over the nansen gakkel ridge one over the lomonosov ridge and a third flowing from the canadian basin the slight differences observed in salinity and temperature characteristics of the deeper waters of the nansen and amundsen basins do not lead to an obvious explanation of their origin or flow pattern

changes in temperature and tracer distributions within the arctic ocean results from the 1994 arctic ocean section abstract major changes in temperature and tracer properties within the arctic ocean are evident in a comparison of data obtained during the 1994 arctic ocean section to earlier measurements 1 anomalously warm and well ventilated waters are now found in the nansen amundsen and makarov basins with the largest temperature differences as much as 1 c in the core of the atlantic layer 200 400 m thus thermohaline transition appears to follow from two distinct mechanisms narrow order 100 km topographically steered cyclonic flows that rapidly carry new water around the perimeters of the basins and multiple intrusions 40 60 m thick which extend laterally into the basin interiors 2 altered nutrient distributions that within the halocline distinguish water masses of pacific and atlantic origins likewise point to a basin wide redistribution of properties 3 distributions of cfcs associated with inflows from adjacent shelf regions and from the atlantic demonstrate recent ventilation to depths exceeding 1800 m 4 concentrations of the pesticide hch in the surface and halocline layers are supersaturated with respect to present atmospheric concentrations and show that the ice capped arctic ocean is now a source to the global atmosphere of this contaminant 5 the radionuclide 129i is now widespread throughout the arctic ocean although the current level of 129i level poses no significant radiological threat its rapid arrival and wide distribution illustrate the speed and extent to which waterborne contaminants are dispersed within the arctic ocean on pathways along which other contaminants can travel from western european or russian sources

double diffusive interleaving part i linear stability analysis abstract quasi horizontal interleaving between water masses is frequently observed in the frontal regions between different water masses where there are significant compensating isopycnal gradients of temperature and salinity it is believed that these intrusions are driven by double diffusive convection which transports salt heat and density across sharp quasi horizontal interfaces i e across regions of large vertical property gradients stern and other investigators have parameterized the vertical flux of salt in these intrusions by an eddy diffusivity multiplied by the vertical gradient of salinity whereas laboratory experiments show that sharp interfaces tend to occur by double diffusive convection and that the vertical fluxes of properties depend on the property contrasts across the interfaces in this paper it is assumed that the vertical fluxes of double diffusive convection are proportional to the salinity contrast across the sharp interfaces that occur between the quasi horizontal intrusio

east west differences in water mass nutrient and chlorophyll a distributions in the sea ice reduction region of the western arctic ocean 1 the r v mirai conducted hydrographic surveys in the western arctic ocean during summer 2004 across a front between cold arctic water and warm water from the pacific ocean where sea ice cover has been largely reduced in recent summers the hydrographic data indicate a new type of vertical temperature minimum water west of the front along isohaline surfaces with approximate salinity s of 32 which is fresher than the typical temperature minimum s 33 caused by spreading of pacific winter water pww mainly to the east of the front both of the temperature minimum waters are characterized by low potential vorticity with near freezing temperature suggesting that they are formed by winter convection with sea ice formation a difference between the waters results from a large contribution of sea ice meltwater to the fresh temperature minimum frtmin water of s 32 the distributions of the sea ice meltwater contribution and nitrogen deficit suggest that summer shelf water largely influenced by the sea ice melt in the chukchi sea is modified by winter convection on its way to the chukchi abyssal plain to form the frtmin water this water supplies nutrients through the water distribution to the west of the front at depths shallower than the nutrient maximum layer caused by the pww spreading the shallower nutrient supply by the frtmin water combined with light penetration without sea ice cover could produce a prominent chlorophyll a maximum layer west of the front

eocene challis kamloops volcanism in central british columbia an example from the buck creek basin eocene volcanic rocks of the buck creek basin in central british columbia are part of the challis kamloops volcanic belt extending from the united states across british columbia to central yukon the volcanic rocks include two units the buck creek formation composed of high k calc alkaline rocks with predominant andesitic composition and the overlying swans lake unit made up of intraplate tholeiitic basalts whole rock 40ar 39ar data for both units show that they were emplaced at 50 ma they have similar mantle normalized trace element patterns characterized by a large ion lithophile element enrichment and nb ta depletion similar chondrite normalized rare earth element patterns with la yb n 4 14 and heavy rare earth element fractionation and overlapping epsilonnd values 2 4 3 1 and initial sr isotope ratios 0 704 these features suggest derivation of these two units from a similar mantle source probably garnet bearing subcontinental lithosphere the differences between tholeiitic and calc a

vertical heat transfer in the arctic ocean the role of double diffusive mixing 1 microstructure profiles collected in the central amundsen basin are analyzed in order to quantify the role of double diffusive mixing for vertical heat transfer from the atlantic layer in the profiles a persistent but laterally incoherent thermohaline staircase structure is identified in the 200 260 m depth range the staircase contains homogeneous layers with average height of 1 3 m and thin high gradient interfaces with average temperature and salinity jumps of about 0 065 c and 0 015 respectively when inferred from a commonly used diffusive convection parameterization the average vertical heat flux within the staircase is 0 6 w m 2 this is one order of magnitude larger than the molecular diffusion alone and of the same order as the overall heat loss from the atlantic layer in the deep basins of the arctic ocean the parameterization is evaluated using observed turbulent heat fluxes and is found to overestimate diffusive convective fluxes with up to an order of magnitude especially for weak thermal forcing small temperature jumps in staircase staircases coexist with thermohaline intrusions in the vertical temperature and salinity profiles lomonosov ridge is identified as a potential region for formation of intrusions it is found that salt fingering is the dominant process during intrusion growth whereas diffusive convection is the dominant process in maintaining the intrusions at steady state in the deep basins

hydrography of the west spitsbergen current svalbard branch autumn 2001 1 the atlantic inflow is the primary source of water and heat to the arctic ocean a large portion enters through fram strait where it splits into the yermak and svalbard branches in october to november 2001 the uscgc healy occupied five oceanographic transects across the svalbard branch west and north of spitsbergen temperature and salinity sections show the warm salty atlantic water cooling and freshening as it flows along the continental slope for 553 km the temperature in the upper 500 m of the water column decreased by 0 25 c 100 km implying a heat flux across the sea surface of up to 520 w m2 if one assumes a nominal current of speed of 0 1 m s a temperature salinity t s analysis shows that the shape of the t s curves can be explained in terms of the ratio of the atmospheric to ice melt heat flux the observations imply that ice melt accounts for progressively more surface cooling as the flow moves toward the arctic ocean an autonomous underwater vehicle completed a vertical section in the region of maximum water mass gradient and revealed layer interleaving in fine detail data from this cruise extend a long time series of atlantic layer source temperature beginning in 1910 saloranta and haugan 2001 the extended observations show that after the temperature of the atlantic layer inflow reached a peak in 1992 it cooled to a minimum in 1998 and rose again through 2001

can low magnitude earthquakes act as a triggering factor for landslide activity examples from the western carpathian mts poland abstract there are numerous examples of the impact of strong earthquakes on landslide activity there is however very little information about the ability of low magnitude earthquakes m

intrusive mixing in a mediterranean salt lens intrusion slopes and dynamical mechanisms abstract thermohaline intrusions found in meddy sharon were laterally coherent the slope of these intrusions across density surfaces was in opposite senses in the upper and lower part of the meddy consistent with i the mcintyre instability for prandtl number less than one in which case mass flux assumed equal in heat and salt diffusivity dominates over viscosity or ii double diffusive intrusions in which diffusive fluxes dominate in the upper diffusively unstable portion of the meddy and finger fluxes dominate in the lower fingering unstable part the magnitudes of the intrusion slopes are outside the range of angles for which the mcintyre mechanism can provide energy to the intrusive motions but within the range of angles for which double diffusive mixing can drive the intrusions thus the energy source for the intrusions is not the kinetic or potential energy of the geostrophic shear flow but is the potential energy associated with the lateral salinity and temperature gradients furthe

supercooling and energy exchange near the arctic ocean surface conductivity temperature and depth ctd measurements made north of svalbard centered around 83 n 10 e show regions in which the surface waters are supercooled to a depth of about 8 m at other locations warm atlantic waters advected into the area by the west spitzbergen current are melting the sea ice the resulting large horizontal salinity gradients cause intrusive layering with layers at depth sometimes being below their surface freezing point supercooling is explained in terms of the pressure dependence of freezing temperature and the existence of ice keels well below the surface it is noted that the potential heat sink for surface freezing provided by supercooling can be of the same order as that available from heat loss to the atmosphere at the same time an equivalent amount of ice is being melted off the keels thus constituting an ice pump

intrusions in double diffusively stable arctic waters evidence for differential mixing abstract intrusions like those observed in double diffusively stable regions of the arctic ocean can grow from uniform ambient temperature and salinity gradients if diapycnal mixing of these two components differs assuming this to be the driving mechanism the observed 40 60 m intrusion heights constrain the turbulent diffusivity for heat to be less than about 0 01 cm2 s 1 and the salt to heat turbulent diffusivity ratio to be greater than about 0 6 if the diffusivities are constant observations indicate that the intrusions slope across isopycnals in a sense that is consistent with such a scenario although the along intrusion density ratio is greater than that predicted by linear theory for the fastest growing intrusions numerical solutions for growing intrusions resemble observed temperature and salinity profiles

the diffusive regime of double diffusive convection the diffusive regime of double diffusive convection is discussed with a particular focus on unresolved issues that are holding up the development of large scale parameterizations some of these issues such as interfacial transports and layer interface interactions may be studied in isolation laboratory work should help with these however we must also face more difficult matters that relate to oceanic phenomena that are not represented easily in the laboratory these lie beneath some fundamental questions about how double diffusive structures are formed in the ocean and how they evolve in the competitive ocean environment

nonlinear equilibration of thermohaline intrusions abstract the nonlinear behavior of thermohaline intrusions on a wide front is investigated using a one dimensional numerical model the model is used to follow the evolution of a field of intrusions from infinitesimal amplitude to a large amplitude state characterized by inversions in temperature and salinity it is thus possible to extend the analytical studies of toole and georgi and others to large amplitude allowing for the effects of amplitude dependent diffusivities and for the appearance of stably stratified diffusively stratified and statically unstable regions in the water column as the intrusions grow the model runs are initialized with infinitesimal disturbances that grow exponentially in time until inversions in temperature and salinity occur after inversions appear the intrusions evolve toward an equilibrium state in which friction balances buoyancy forces for both finger and diffusive sense basic state stratifications these equilibrium states are characterized by statically unstabl

the eocene oligocene magmatic hiatus in the south central canadian cordillera a capture of the kula plate by the pacific plate the tertiary paleogene and neogene geological record in south central canadian cordillera is dominated by the 350 400 km wide lower eocene volcanic arc and the overlying miocene recent back arc lavas that are separated by a hiatus in magmatic activity between 48 and 24 ma in the black dome area 240 km north of vancouver the eocene volcanic rocks are mainly continental margin calc alkaline andesite and dacite resulting from the melting of a juvenile mafic source at the base of the crust in contrast the miocene volcanic rocks resemble continental flood basalts both eocene and miocene rocks from the black dome volcanic complex have high positive end values 7 2 to 7 4 and 6 4 to 7 6 respectively and low initial sr isotopic ratios 0 702 516 0 703 528 and 0 703 376 0 703 392 respectively comparable to modern oceanic basalts the onset of the hiatus in magmatism at 48 ma coincides with capture of the kula plate by the pacific plate resulting in a change in convergence direction with the

crustal recycling during subduction at the eocene cordilleran margin of north america a petrogenetic study from the southwestern yukon the early eocene 57 3 55 4 ma bennett lake and mount skukum volcanic complexes lie on the coast plutonic complex and intermontane belt boundary of the canadian cordillera at the british columbia yukon border some 200 km east of the current and eocene continental margin both complexes contain rock types from basaltic andesite to rhyolite in a series of lava and pyroclastic flows the location relative to the continental margin the rock types and the presence of an enhanced lile hfse large ion lithophile high field strength element signatures in all samples imply that contemporaneous subduction was the controlling factor in the formation of these complexes the majority of samples however return unusually low compatible element concentrations for given rock types we interpret this data to show that partial melting of the crust was the major source of erupted magmas one formation of andesites at mount skukum and one late dyke at bennett lake do show higher concentrations of compatible trace e

assessing the role of oceanic heat fluxes on ice ablation of the central chukchi sea shelf abstract we investigate the role of oceanic heat flux convergence in the summertime retreat of sea ice in the presence of a mean background flow prior studies indicated that eddies generated along the marginal ice zone front carry substantial quantities of heat laterally beneath the ice but the direct importance of these fluxes to the summertime retreat of sea ice was not well established we use the regional ocean model system roms with an idealized configuration of the chukchi sea shelf and without wind forcing to 1 determine the contributions to ice melt from the oceanic heat flux compared to that from the net atmospheric heat flux through the ice surface 2 evaluate the role of mesoscale fluctuations versus the mean background flow in providing this sub surface heat flux and 3 evaluate the role of the underlying bathymetry in modifying the subsurface heat flux to the ice analyses show that the three main water masses melt water bering sea water and winter water establish frontal systems the shelf water front and the ice edge melt water front that control baroclinic processes which in turn regulate the quantity of heat fluxed laterally and vertically to the ablating ice edge we identify and characterize distinct oceanic zones associated with these fronts the shelf water transition zone and the melt water transition zone that are delineated by flow dynamics and hydrographic structure the integrated heat flux along the modeled ice edge is significant lateral eddy transport of heat is as large as 2 tw of which 50 is fluxed upwards into the near surface melt water we introduce a parameterization for the vertical heat transport to the ice through the near surface meltwater lens that is a function of the along front current velocity and the cross front temperature gradient such a parameterization could improve coarse scale ocean and climate models that lack the resolution necessary for reproducing such small scale processes the results of this study may be informative to investigations of ice edge biological processes

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

oceanic thermohaline intrusions observations intrusions are commonly observed in the upper deep and coastal oceans and are closely linked to lateral fluxes of heat salt and momentum this is a review of observations of intrusions and the results of comparisons of properties such as scale slopes microstructure activity and fluxes with theoretical models a summary of estimates of lateral heat fluxes indicates a wide range of lateral diffusivities we conclude by noting that our present knowledge is insufficient to predict the structure length scales and lateral fluxes of thermohaline intrusions with confidence and list a number of unresolved questions suggestions are made for compilation of existing data into a database for exploratory analysis and testing of theoretical hypotheses an outline is given of a potential collaborative field experiment using ctd fluorescent dye and microstructure observations

eocene shoshonitic mafic dykes intruding the monashee complex british columbia a petrogenetic relationship with the kamloops group volcanic sequence the newly named three valley suite tvs kersantite lamprophyre to shoshonitic mafic dykes of the monashee complex are inferred to be hypabyssal feeder dykes to an alkaline to calc alkaline volcanic suite related to the kamloops group these dykes were emplaced in a subvertical north trending orientation coincident with inferred eocene crustal extension 50 0 ma based on the flat 40ar 39ar step heating plateau of contact metamorphic muscovite on the margin of a tvs dyke these weakly altered mafic dykes are fine grained with phenocrysts 0 5 2 0 mm of phlogopite augite amphibole and olivine pseudomorphed by clays rare labradorite and both primary and secondary carbonates set in a fine grained groundmass of similar mineralogy consistent with their classification as plagioclase bearing potassic diorite to kersantite lamprophyre the dykes are weakly silica undersaturated and alkalic 2 8 wt k2o 7 7 wt mgo with high large ion lithophile element contents 300 times primitive mantle and ele

eocene volcanism in the buck creek basin central british columbia canada transition from arc to extensional volcanism abstract the eocene buck creek volcanic complex central british columbia canada is a part of the challis kamloops volcanic province that extends from yukon across british columbia to the northern united states running approximately parallel to the margin of the north american continent the complex is associated with the formation of a fault bounded basin controlled by strike slip faults the volcanic rocks were emplaced during two short lived

frontal structures associated with coastal upwelling and ice edge subduction events in southern beaufort sea during the canadian arctic shelf exchange study the near surface temperature structure in the southeastern beaufort sea is shown to have been largely dependent on frontal dynamics in spring 2004 which may be typical for the region easterly wind events generated coastal upwelling along the cap bathurst peninsula a recurring event in that area further west a large mesoscale anticyclone simultaneously developed and subsequently controlled the sea surface circulation in the central amundsen gulf sharp temperature and density fronts were created at the surface at both eastern and western ends of the domain sampling north of cape bathurst and cape parry showed evidence of frontal intensification frontal features were detected near the 50 200 m isobaths at the mouth of the gulf where density compensated near surface intrusions driven by agesotrophic vertical circulation were identified these warm water tongues intruded into the outcropping isopycnal layers which dipped down between 5 and 25 m over the mackenzie shelf they then crossed the density surfaces with an inverse slope consistent with n f as predicted for quasi geostrophic flows the front event ended prior to the breakup of the landfast ice bridge in late june with sea surface temperature undergoing quick and widespread changes throughout the amundsen gulf