11 000 yrs of environmental change in the northwest passage a multiproxy core record from central parry channel canadian high arctic article i nfo piston core 97022 004pc 74 48 0 n 97 05 9 w 267 m water depth represents a rare paleoenvironmental archive from the understudied west central canadian arctic archipelago lithological biogeochemical and microfossil dinoflagellate cysts non pollen palynomorphs benthic and planktonic foraminifera character istics in combination with a chronostratigraphy based on seventeen radiocarbon dates show seven promi nent paleoenvironmental episodes since the end of the last regional glaciation the basal diamict zone i records decoupling of previously grounded glacial ice followed by ice proximal conditions zone iia commencing at 10 8 cal ka bp age depth model extrapolation after an interval of pervasive sea ice zone iib ice distal conditions are established zone iic although sparse microfossils are present in glaciomarine sediments zone ii noticeable biological activity with heightened abundances and diversities across all groups begins in the postglacial zone iii 10 3 10 0 cal ka bp when planktonic foraminifera neogloboquadrina pachyderma appear as planktonics are excluded from the study area today due to shal low inter channel sills this likely signals the inflow of relatively warm and saline atlantic derived arctic intermediate water below 250 m presumably facilitated by glacio isostatically enhanced deglacial water depths the subsequent zone iv 10 0 7 0 cal ka bp characterized by heightened biological productivity in both plankton and benthos and reduced seasonal sea ice cover may correspond to a previously proposed holocene thermal maximum this apparent amelioration ends by the mid holocene zone v 7 0 5 7 cal ka bp when arctic intermediate water is excluded from the study area and water depths approach modern values high arctic conditions with seasonal sea ice cover a circulation dominated by arctic ocean surface water and microfossil assemblages similar to modern are found from 5 7 cal ka bp onwards zones vi vii as only minor environmental fluctuations are apparent during the late holocene shorter term climatic episodes e g little ice age are not recognized in this record

estimating sea ice area flux across the canadian arctic archipelago using enhanced amsr e 1 enhanced resolution advanced microwave scanning radiometer amsr e imagery is used to estimate daily sea ice area fluxes between the canadian arctic archipelago and the arctic ocean and baffin bay for the period september 2002 to june 2007 over the period amundsen gulf and m clure strait exported 54 103 km2 of sea ice area or roughly 77 km3 of sea ice volume each year into the arctic ocean export import into the arctic ocean through the queen elizabeth islands is small and uncertain since no estimates for july and august could be made due to atmospheric attenuation of the microwave signal lancaster sound exported 68 103 km2 of sea ice area or roughly 102 km3 of ice volume into baffin bay this produced a net loss of sea ice area of about 122 103 km2 or roughly 174 km3 a 1 which is presumed to be generated from within the archipelago itself mainly through the stationary and transient polynyas and leads that form each winter daily ice area fluxes for amundsen gulf ag and lancaster sound ls were as high as 2500 km2 d 1 and were event driven depending on synoptic scale atmospheric circulation and the mobility of the sea ice mean sea level pressure difference across each gate is moderately correlated with daily sea ice area fluxes despite the fact that free ice drift conditions are not always met in the region cross gradient and daily sea ice area flux for lancaster sound show a large number of counter gradient ice flux occurrences suggesting that local mesoscale winds nongeostrophic and perhaps ocean currents play a role in transporting sea ice through this gate monthly ice fluxes for the ag and ms gate were positively correlated with the ao index indicating that a strong beaufort sea high pressure and gyre correspond to more export into the beaufort sea monthly fluxes for the ls gate were positively correlated with the nao index indicating that strong southerly atmospheric circulation over baffin bay increases ice export into baffin bay from lancaster sound

upwelling in the alaskan beaufort sea atmospheric forcing and local versus non local response abstract the spin up and relaxation of an autumn upwelling event on the beaufort slope is investigated using a combination of oceanic and atmospheric data and numerical models the event occurred in november 2002 and was driven by an aleutian low storm the wind field was strongly influenced by the pack ice distribution resulting in enhanced winds over the open water of the chukchi sea flow distortion due to the brooks mountain range was also evident mooring observations east of barrow canyon show that the beaufort shelfbreak jet reversed to the west under strong easterly winds followed by upwelling of atlantic water onto the shelf after the winds subsided a deep eastward jet of atlantic water developed centered at 250 m depth an idealized numerical model reproduces these results and suggests that the oceanic response to the local winds is modulated by a propagating signal from the western edge of the storm the disparity in wave speeds between the sea surface height signal traveling at the fast barotropic shelf wave speed versus the interior density signal traveling at the slow baroclinic wave speed leads to the deep eastward jet the broad scale response to the storm over the chukchi sea is investigated using a regional numerical model the strong gradient in windspeed at the ice edge results in convergence of the offshore ekman transport leading to the establishment of an anti cyclonic gyre in the northern chukchi sea accordingly the chukchi shelfbreak jet accelerates to the east into the wind during the storm and no upwelling occurs west of barrow canyon hence the storm response is fundamentally different on the beaufort slope upwelling versus the chukchi slope no upwelling the regional numerical model results are supported by additional mooring data in the chukchi sea

holocene paleoceanography of the northwest passage canadian arctic archipelago abstract a series of cores box and piston were collected at 2 key locations in lancaster sound cores 2004 804 009 bc and pc and barrow strait cores 2005 804 004 bc and pc in the canadian arctic archipelago to document the evolution of sea surface conditions in the main axis of the northwest passage during the holocene time period reconstruction of sea surface parameters summer temperature and salinity duration of sea ice cover were estimated based on transfer functions using dinoflagellate cyst assemblages as proxy indicators the chronology of these cores is based on calibrated ams 14c dates 210pb analyses and correlations between paleomagnetic secular variations of the geomagnetic field and a predicted spherical harmonic model of the geomagnetic field cals7 k 2 our age models for both cores indicate that 009 pc spans the last 11 100 cal bp while 004 pc encompasses the last 10 800 cal bp calculated sedimentation rates are in the range of 43 140 cm kyr for core 009 pc and 15 118 cm kyr for core 004 pc allowing for a millennial time scale resolution in each core our results indicate relatively harsh conditions in lancaster sound between 10 800 and 9000 cal bp summer temperatures 2 c cooler than at present which we associate with the presence of active ice streams in northernmost baffin bay and a weak west greenland current this is followed by a warming trend up to 3 c higher than present that took place between 8500 and 5500 cal bp which we associate with the holocene thermal maximum and to a large scale atmospheric pattern such as the arctic oscillation operating at the millennial time scale this is concomitant with an increase in the relative abundance of phototrophic dinoflagellate cyst taxa a gradual cooling of sea surface temperature and increased sea ice follow this from 5500 cal bp until the modern period in barrow strait harsh sea surface conditions prevailed from 11 100 to 5500 cal bp with summer temperatures as low as 4 c cooler than at present the warming trend occurred later in this region between 5500 and 1000 cal bp after which a gradual cooling is observed until the modern period the apparent shift or opposite warming trends between lancaster sound and barrow strait after 5500 cal bp could be the result of a change in atmospheric circulation patterns related to a possible shift in the ao mode from ao to ao comparison of ice core 18o record from devon island ice cap and the reconstructed sea surface temperature from core 009 pc suggests a strong atmospheric oceanic coupling throughout the holocene in this area

outside influences on the water column of cumberland sound baffin island cumberland sound host to a commercially viable fish population in the deepest depths is a large embayment on the southeast coast of baffin island that opens to davis strait conductivity temperature and depth profiles were collected during three summer field seasons 2011 2013 and two moorings were deployed during 2011 2012 within the sound salinity increases with increasing depth while water temperature cools reaching a minimum of 1 49 c at roughly 100 m below 100 m the water becomes both warmer and saltier temperature salinity curves for each year followed a similar pattern but the entire water column in cumberland sound cooled from 2011 to 2012 and then warmed through the summer of 2013 even though the sound s maximum depth is over a kilometer deeper than its sill water in the entire sound is well oxygenated a comparison of water masses within the sound and in davis strait shows that above the sill the sound is flooded with cold baffin island current water following an intermittent geostrophic flow pattern entering the sound along the north coast and leaving along the south below the sill replenishment is infrequent and includes water from both the baffin island current and the west greenland current deep water replenishment occurred more frequently on spring tides especially in the fall of 2011 although the sound s circulation is controlled by outside currents internal water modifying processes occur such as estuarine flow and wind driven mixing

neodymium isotopes in seawater from the barents sea and fram strait arctic atlantic gateways abstract the neodymium concentration c nd and isotopic composition e nd in seawater have been determined in the water column at five sites in the barents sea fram strait area where most of the water exchange between the arctic ocean and the north atlantic takes place in the main arctic ocean inflow branch across the barents sea the concentration and isotopic composition c nd 15 5 pmol kg and e nd 10 8 are similar to those reported for the northeastern nordic seas which is consistent with this region being a source area for the arctic inflow due to the addition of nd from svalbard shelf sediments the c nd in the surface waters above 150 m in the fram strait inflow branch is higher by a factor of 2 and the e nd is shifted to lower values 11 8 in the stratified nansen basin where cold low salinity water overlies warmer atlantic water the c nd and e nd do not vary with the vertical temperature salinity structure but are essentially constant and similar to those of the atlantic inflow throughout the entire water column down to 3700 m depth which indicates that the nd is to a large extent of atlantic origin compared to the atlantic inflow water the nd in the major arctic ocean outflow the fram strait show higher c nd in the surface waters above 150 m and a higher e nd 9 8 throughout the entire water column down to 1300 m depth sources for the more radiogenic nd isotopic composition in deep water of the fram strait outflow most likely involve boundary exchange with sediments on the shelf and slope as the water passes along the canadian archipelago river water is a possible source in the surface water but it also seems likely that pacific water nd modified by interactions on the shelf is an important component in the fram strait surface outflow changes in the relative proportions of inflow of river water and flow of pacific water through the arctic ocean could thus influence the isotopic composition of nd in the north atlantic

influence of inheritance and pedogenesis on heavy metal distribution in soils of sicily italy abstract the recognition of the potential health hazards associated with heavy metals has focused attention on the levels and behaviours of these elements both in natural and contaminated environments various soil types developed from different parent materials in sicily italy have been analysed in order to compare heavy metal distribution under different geopedological conditions total metal concentrations metal partitioning and distribution profiles are discussed in relation to the inheritance factor and pedogenic processes parent material composition largely influences the contents of heavy metals in most of the analysed soils mainly differentiating pedons for their metal concentration on the basis of sedimentary and volcanic parent materials however an exception is represented by the carbonate free alfisols and mollisols which are markedly enriched in heavy metals with respect to the underlying limestones and calcarenites on the basis of chemical and mineralogical results supported by data from sequential extraction sep heavy metal enrichment in these soils is associated with the formation of common to abundant fe mn oxides and clay accumulation for mollisols there is evidence for a major role of organic matter in heavy metal retention in surface horizons in the other pedons pedogenic processes appear to mainly influence the redistribution of heavy metals throughout the soil horizons rather than affecting the total content argillopedoturbation seems to be responsible for a uniform distribution of heavy metals in vertisol profiles on marly clays accumulation of heavy metals in the topsoil of inceptisols on clays with gypsum and entisols on gypsarenites and diatomites is caused partially by adsorption on organic matter and mainly by dissolution of primary gypsum and opal a a pedogenic influence is less evident in young andisols whose heavy metal composition greatly reflects that of hawaiitic pyroclastic deposits interbedded within the profiles however a certain redistribution of cu accumulated as metal organic matter complexes is evidenced in the surface horizon by sep

causes and consequences of arctic freshwater routing into the nordic seas during late marine isotope stage 5 sediment core ps1904 reveals continuous records of planktic and benthic foraminiferal stable isotopes 18o 13c from the north eastern greenland continental margin the data show good comparability with other records from the nordic seas allowing the stratigraphic range of ps1904 to be dated to marine isotope stage mis 6 focusing on mis 5 reveals light 18o values during mis 5a compared to the last interglacial peak mis 5e which indicates that surface and bottom water layers were strongly affected by freshwater during the former event we present two possible scenarios explaining the origin and routing of the freshwater i drainage of a eurasian proglacial lake coupled with the collapse of the kara sea ice sheet at the mis 5b a boundary and ii destabilization and melting of the nearby greenland ice sheet although both scenarios could have acted simultaneously sediment records from the eurasian sector of the arctic ocean hint at the proglacial lake system in north western siberia as the largest freshwater source regardless of the actual source the freshwater lowered the surface ocean salinity causing water column stratification and sea ice expansion increased sea ice abundance led to a higher albedo and probably contributed to the cooling and global ice sheet growth that occurred subsequently during mis 4

the background concentrations of 13 soil trace elements and their relationships to parent materials and vegetation in xizang tibet china abstract the background concentrations of 13 soil trace elements copper cu lead pb zinc zn cadmium cd nickel ni chromium cr mercury hg arsenic as selenium se cobalt co vanadium v manganese mn and fluorine f from approximately 205 pedons in tibet china are reported here for the first time the 13 trace element concentrations follow an approximately log normal distribution while the mean concentrations of hg and se are lower and as is higher than the average concentration for all of china concentrations of the other trace elements are similar to the national average trace element concentrations are related to vegetation and human activity also played a notable role on the contents of trace elements in tibet the parent material relationship for all 13 soil trace element concentrations follows the pattern shale sandstone igneous rock limestone alluvial sediment glacial deposits lake sediments while for vegetation and human activity the concentration pattern is farmland shrub forests meadow prairie marsh and others the soil trace element concentrations on the tibetan plateau are related primarily to the parent material but were also affected by vegetation and human activity

volume and freshwater transport of the labrador current in flemish pass a current meter array of 3 months duration from the newfoundland shelf edge to the 400 m isobath gives a mean southward transport of the labrador current of 3 7 sv with a freshwater component of 0 1 sv over a 2 month period the volume and the freshwater flow increased by 3 and 0 09 sv respectively mean currents exceeded the variable components by a factor of 3 this estimate of the total transport of the labrador current is low because the flow extends eastward of the array beyond the 400 m isobath to at least 1000 m the total volume transport of the labrador current through flemish pass is estimated roughly to range between 6 3 and 9 8 sv if archived current meter data are incorporated with the observations from this array the mean freshwater transport is estimated to be 0 13 0 03 sv

flow of winter transformed pacific water into the western arctic abstract the dynamics of the flow of dense water through barrow canyon is investigated using data from a hydrographic survey in summer 2002 the focus is on the winter transformed bering water the highest volumetric mode of winter water in the chukchi sea which drains northward through the canyon in spring and summer the transport of this water mass during the time of the survey was 0 2 0 3 sv as the layer flowed from the head of the canyon to the mouth it sank decelerated and stretched strong cyclonic relative vorticity was generated on the seaward side of the jet which compensated for the stretching this adjustment was incomplete however in that it did not extend across the entire current possibly because of internal mixing due to shear instabilities the resulting vorticity structure of the flow at the canyon mouth was conducive for baroclinic instability and eddy formation multiple eddies of winter transformed bering water were observed along the chukchi beaufort shelfbreak those to the west of barrow canyon were in the process of being spawned by the eastward flowing shelfbreak current emanating from herald canyon while the single eddy observed to the east originated from the barrow canyon outflow it is argued that such an eddy formation is a major source of the ubiquitous cold core anti cyclones observed historically throughout the canada basin implications for the ventilation of the upper halocline of the western arctic are discussed

nares strait hydrography and salinity field from a 3 year moored array 1 nares strait to the west of greenland facilitates the exchange of heat and freshwater between the arctic and atlantic oceans this study focuses on salinity temperature and density measurements from nares strait from a mooring array deployed from 2003 to 2006 innovative moorings requiring novel analysis methods measured seawater properties near 80 5 n at spacing sufficient to resolve the internal rossby deformation radius the 3 year mean geostrophic velocity has a surface intensified southward flow of 0 20 m s 1 against the western side of the strait and a secondary core flowing southward at 0 14 m s 1 in the middle of the strait data show warm salty water on the greenland side and cold fresher water on the ellesmere island side especially in the top layers there was a clear difference in hydrographic structure between times when sea ice was drifting and when it was land fast ice was drifting in late summer fall and early winter with a strong surface intensified geostrophic flow in the middle of the strait ice was land fast in late winter spring and early summer when there was a subsurface core of strong geostrophic flow adjacent to the western side of the strait salinity variations of about 2 psu in time and space reflect a variable freshwater outflow from the arctic ocean one particularly strong pulse occurred at the end of july 2005 for several days steeply sloping isohalines indicated strong geostrophic flow down the middle of the strait coinciding with an amplified ice export from the arctic due to strong southward winds

the pedo geochemistry of vertisols under tropical savanna climate abstract fourteen representative thai vertisols on lowland and upland areas under a tropical savanna climate were investigated to ascertain parent material and pedogenic influences on their geochemistry physico chemical mineralogical and geochemical properties were determined for 98 soil samples multivariate analysis was used to interpret the dataset and identify affinity groups of samples and properties silicon al fe and ca are the major constituents of the soils mean concentrations of elements are mostly within the range for worldwide normal soils the variations in concentration of elements between soils reflect differences in the abundance of the major mineral constituents beidellite calcite iron oxides and quartz factor analysis of geochemical data showed that most elements do not cluster into discrete affinity groups the composition of soils is mostly quite uniform throughout the profiles with no evidence for depositional layers beidellite is the dominant clay mineral and acts as a reservoir of many major and trace elements in these soils the accumulation of pedogenic calcium carbonate and fe mn nodules in distinct horizons has resulted in systematic variations in composition within and between soil profiles for those elements that are associated with these neoformed materials e g fe mn co v th ba and ge

air sea co2 fluxes and the continental shelf pump of carbon in the chukchi sea adjacent to the arctic ocean the chukchi sea a shallow sea ice covered coastal sea adjacent to the arctic ocean exhibits an intense bloom of phytoplankton each year due to the exposure of nutrient laden surface waters during the brief summertime retreat and melting of sea ice the impact of phytoplankton production and other factors on the seasonal dynamics of carbon and air sea co2 fluxes were investigated during two survey cruises 5 may 15 june 2002 and 17 july 26 august 2002 as part of the western arctic shelf basins interactions sbi project in springtime most of the chukchi sea was sea ice covered 95 and remnant winter water was present across the shelf surface layer seawater partial pressure of co2 pco2 ranged from 200 320 atm indicative of undersaturation with respect to atmospheric pco2 although sea ice cover kept rates of air to sea co2 flux generally low 80 air to sea co2 fluxes remained generally low 2 mmoles co2 m 2 d 1 seasonal i e may to september and annual net air to sea co2 fluxes from the chukchi sea shelf were estimated at 27 7 tg c yr 1 and 38 7 tg c yr 1 respectively the chukchi sea represents the largest oceanic co2 sink in the marginal coastal seas adjacent to the arctic ocean an active continental shelf pump of carbon driven by the northward transport of nutrient rich water of pacific ocean origin high rates of primary and net community production during the sea ice free period and lateral export of organic carbon maintains the chukchi sea shelf and slope as a perennial ocean co2 sink

on the origin of the chemical properties of the arctic ocean halocline profiles of chemical constituents in seawater above the alpha ridge in the central arctic ocean obtained during the canadian expedition to study the alpha ridge cesar support a model in which the halocline is maintained by dense saline water produced on the continental shelves within the arctic ocean by the formation of sea ice it is argued that nutrient regeneration on the continental shelves largely accounts for the nutrient maximum that has been observed in the upper halocline over a wide region of the arctic ocean and that while the bering sea and north altantic can be recognized as origins of halocline water water masses from these regions undergo sufficient changes in their chemical properties within the arctic ocean significant that they no longer retain their identity in the halocline

long term variability of arctic ocean waters evidence from a reanalysis of the ewg data set 1 we have examined interannual to decadal variability of water properties in the arctic ocean using an enhanced version of the 1948 1993 data released earlier under the gore chernomyrdin environmental bilateral agreement that earlier data set utilized gridded fields with decadal time resolution whereas we have developed a data set with annual resolution we find that beginning about 1976 most of the upper arctic ocean became significantly saltier possibly related to thinning of the arctic ice cover there are also indications that a more local upper ocean salinity increase in the eurasian basin about 1989 may not have originated on the shelf as had been suggested earlier in addition to the now well established warming of the atlantic layer during the early 1990s there was a similar cyclonically propagating warm event during the 1950s more remarkable however was a pervasive atlantic layer warming throughout most of the arctic ocean from 1964 1969 possibly related to reduced vertical heat loss associated with increased upper ocean stratification a cold period prevailed during most of the 1970s and 1980s with several very cold events appearing to originate near the kara and laptev shelves finally we find that the silicate maximum in the central arctic ocean halocline eroded abruptly in the mid 1980s demonstrating that the redistribution of pacific waters and the warming of the atlantic layer reported from other observations during the 1990s were distinct events separated in time by perhaps 5 years we have made the entire data set publicly available

physical and geochemical properties across the atlantic pacific water mass front in the southern canadian basin temperature salinity nutrients oxygen and halocarbon data collected in the arctic ocean reveal a frontal structure previously unrecognized in the hydrography of the canadian basin samples were collected on a 1300 km section extending from the beaufort sea in the canada basin to the east siberian sea in the makarov basin these data collected in 1993 aboard the ccgs henry larsen reveal a lateral boundary between water masses of atlantic and pacific origin the term water mass assembly is introduced to describe the basic arrangement or vertical stacking of water masses found in the arctic ocean recognizing that water mass components within each assembly may differ from basin to basin using historical data two primary water mass assemblies are defined each consisting of three layers an upper layer an atlantic layer and a deep layer these two assemblies are marked by important differences one assembly here defined as the western arctic wa assembly is characterized by an upper layer of relatively fresh high nutrient water of pacific origin below this by an atlantic layer with a core temperature generally below 0 5 c and finally by a deep layer of higher salinities and colder temperatures about 0 5 c than found in the overlying atlantic layer the second assembly here defined as eastern arctic ea assembly is characterized by the absence of pacific water in the upper layer below this by an atlantic layer core as warm as 2 to 3 c and by a colder about 0 9 c deep layer because the presence or absence of pacific origin water is a key characteristic distinguishing the two assemblies we will refer to the water mass boundary between the two assemblies as the atlantic pacific front earlier research indicated that water masses in the arctic ocean were separated by a front above the lomonosov ridge into the canadian and eurasian basins although all larsen 93 stations from the canada basin a1 d1 display classic wa assembly characteristics the makarov basin station e1 shows ea assembly characteristics in the upper and atlantic layers and a wa assembly deep layer this suggests a relocation in the position of the atlantic pacific boundary away from the lomonosov ridge further larsen 93 data show the transition region between the atlantic and deep layers is fresher in the makarov basin than corresponding water in either the canada or eurasian basins implying a source of cold low salinity water perhaps from the laptev and east siberian shelves the front separating these two assemblies lies above the mendeleyev ridge and is marked by large lateral gradients in all measured properties in particular the penetration of anthropogenic halocarbons is 2 to 3 times deeper in the makarov basin than in the canada basin implying enhanced rates of ventilation this suggests that direct exchange between the canadian and eurasian basins has occurred recently near the perimeter and that physical and chemical properties including contaminants may have been transported by boundary currents more quickly from one basin to the other

sea ice variations in the central canadian arctic archipelago during the holocene abstract a sea ice record for barrow strait in the canadian arctic archipelago caa is presented for the interval 10 0 0 4 cal kyr bp this holocene record is based primarily on the occurrence of a sea ice biomarker chemical ip25 isolated from a marine sediment core obtained from barrow strait in 2005 a core chronology is based on 14c ams dating of mollusc shells obtained from ten horizons within the core the primary ip25 data are compared with complementary proxy data obtained from analysis of other organic biomarkers stable isotope composition of bulk organic matter benthic foraminifera particle size distributions and ratios of inorganic elements the combined proxy data show that the palaeo sea ice record can be grouped according to four intervals and these can be contextualised further with respect to the holocene thermal maximum htm spring sea ice occurrence was lowest during the early mid holocene 10 0 6 0 cal kyr bp and this was followed by a second phase 6 0 4 0 cal kyr bp where spring sea ice occurrence showed a small increase between 4 0 and 3 0 cal kyr bp spring sea ice occurrence increased abruptly to above the median and we associate this interval with the termination of the htm elevated spring sea ice occurrences continued from 3 0 to 0 4 cal kyr bp although they were more variable on shorter timescales within this fourth interval we also provide evidence for slightly lower and subsequently higher spring sea ice occurrence during the mediaeval warm period and the little ice age respectively comparisons are made between our proxy data with those obtained from other palaeo climate and sea ice studies for the caa

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

the arctic circumpolar boundary current we present high resolution simulations and observational data as evidence of a fast current flowing along the shelf break of the siberian and alaskan shelves in the arctic ocean thus far the arctic circumpolar boundary current acbc has been seen as comprising two branches the fram strait and barents sea branches fsb and bsb respectively here we describe a new third branch the arctic shelf break branch asbb we show that the forcing mechanism for the asbb is a combination of buoyancy loss and non local wind creating high pressure upstream in the barents sea the potential vorticity influx through the st anna trough dictates the cyclonic direction of flow of the asbb which is the most energetic large scale circulation structure in the arctic ocean it plays a substantial role in transporting arctic halocline waters and exhibits a robust seasonal cycle with a summer minimum and winter maximum the simulations show the continuity of the fsb all the way around the arctic shelves and the uninterrupted asbb between the st anna trough and the western fram strait the bsb flows continuously along the siberian shelf as far as the chukchi plateau where it partly diverges from the continental slope into the ocean interior the alaskan shelf break current asc is the analog of the asbb in the canadian arctic the asc is forced by the local winds and high upstream pressure in bering strait caused by the drop in sea surface height between the pacific and arctic oceans

tracing pacific water in the north atlantic ocean 1 in the arctic ocean pacific source water can be distinguished from atlantic source water by nitrate phosphate concentration relationships with pacific water having higher phosphate concentrations relative to those of nitrate furthermore pacific water originally from the inflow through bering strait is clearly recognizable in the outflows of low salinity waters from the arctic ocean to the northern north atlantic ocean through the canadian arctic archipelago and through fram strait in the canadian arctic archipelago we observe that almost all of the waters flowing through lancaster and jones sounds most of the water in the top 100 m in smith sound containing the flow through nares strait and possibly all waters in hudson bay contain no water of atlantic origin significant amounts of pacific water are also observed along the western coast of baffin bay along the coast of labrador and above the 200 m isobath of the grand banks there is a clear signal of pacific water flowing south through fram strait and along the east coast of greenland extending at least as far south as denmark strait pacific water signature can be seen near the east coast of greenland at 66 n but not in data at 60 n temporal variability in the concentrations of pacific water has been observed at several locations where multiple year observations are available

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

the profile of the rare earth elements in the canada basin arctic ocean we analyzed the dissolved rare earth element ree content of three water column profiles two shelf sites and one deep basin site in the canada basin in order to better constrain the behavior of rees in the arctic ocean dissolved concentrations of the rees in the surface are 1 3 to 1 9 times higher than deep water 500 m concentrations which are constant with depth la 19 23 pm nd 14 17 pm yb 4 0 4 3 pm the dominant source of rees to the surface waters of the canada basin is most likely pacific water flowing through the bering strait and chukchi sea and or the mackenzie river dissolved rees in the intermediate and deep waters are constant and appear to behave conservatively allowing us to investigate this aspect of ree behavior in the oceans calculated deep ocean residence times of the rees in the canada basin range from 450 700 years and match the age of these waters we postulate that these values are likely applicable to global deep ocean reservoirs and that observed deviations from this conservative value can help to constrain non conservative processes acting on the rees this article is protected by copyright all rights reserved

the thermohaline circulation of the arctic ocean and the greenland sea the thermohaline circulation of the arctic ocean and the greenland sea is conditioned by the harsh high latitude climate and by bathymetry warm atlantic water loses its heat and also becomes less saline by added river run off in the arctic ocean this leads to rapid cooling of the surface water and to ice formation brine released by freezing increases the density of the surface layer but the ice cover also insulates the ocean and reduces heat loss this limits density increase and in the central arctic ocean a low salinity surface layer and a permanent ice cover are maintained only over the shallow shelves where the entire water column is cooled to freezing can dense water form and accumulate to eventually sink down the continental slope into the deep ocean the part of the atlantic water which enters the arctic ocean is thus separated into a low density surface layer and a denser deep circulation these two loops exit through fram strait the waters are partly rehomogenized in the greenland sea the main current is confined to the greenland continental slope but polar surface water and ice are injected into the central gyre and create a low density lid allowing for ice formation in winter this leads to a density increase sufficient to trigger convection upwelling and subsequent ice melt the convection maintains the weak stratification of the gyre and also reinforces the deep circulation loop as the transformed waters return to the north atlantic the low salinity upper water of the east greenland current enters the labrador sea and influences the formation of labrador sea deep water the dense loop passes through denmark strait and the faroe shetland channel and sinks to contribute to the north atlantic deep water changes in the forcing conditions might alter the relative strength of the two loops this could affect the oceanic thermohaline circulation on a global scale

renewal and circulation of intermediate waters in the canadian basin observed on the scicex 96 cruise during the summer of 1996 the nuclear submarine uss pogy occupied a line of stations extending through the middle of the canadian basin between about 88 n 44 w lomonosov ridge and about 78 n 144 w center of the canada basin ctd niskin bottle casts extending to 1600 m were carried out at eight stations providing the first high quality temperature salinity cfc tritium and 3he data obtained from this region although xctd data had previously been collected in this region these data along with data from stations at the basin boundary to the south and west reveal the presence of well ventilated intermediate water beneath the halocline in the center of the canada basin indicating renewal times of the order of 1 2 decades the least ventilated intermediate water was observed at the northern end of the canada basin along the southern flank of the alpha ridge intermediate water is derived from the atlantic ocean and enters the arctic ocean through fram strait and the barents sea it flows around the arctic basins in boundary currents and splits in the eastern amundsen basin with one branch crossing the lomonosov ridge and flowing along the east siberian continental slope and the other flowing along the eurasian flank of the lomonosov ridge from the 1996 scientific ice expedition scicex 96 observations we conclude that the branch that flows along the east siberian continental slope transports this water to the chukchi rise where it apparently enters the central canada basin with some flow continuing along the boundary to the southern canada basin the fram strait branch water mixes extensively with waters from the canadian basin during its transit along the east siberian continental slope being diluted by a factor of about 5 by the time it reaches the central canada basin the barents sea branch water does not undergo such extensive mixing and is diluted by a factor of only about 2 when it reaches the central canada basin

a role for north pacific salinity in stabilizing north atlantic climate 1 a simple ocean atmosphere feedback may reduce the amplitude of climate variability in around the north atlantic during interglacial compared to glacial states when climate is warm in the north atlantic region the intertropical convergence zone has a relatively northward position and moisture is exported from the tropical atlantic to the tropical pacific at the same time the east asian summer monsoon is strong which helps maintain a positive balance of precipitation over evaporation in the subpolar north pacific this is thought to account for lower salinity in the north pacific relative to the north atlantic which in turn drives northward flow through the bering strait to the northern north atlantic freshening in the north atlantic by water of pacific origin suppresses the meridional overturning circulation and reduces the heat flux the opposite situation exists during cold climate thus the combination of atmospheric vapor transport and flow through bering strait tends to cool the north atlantic region when warm and warm the region when cool

distribution of dissolved organic matter in the eastern bering sea chukchi sea barrow canyon and beaufort sea 1 the distribution of dissolved organic carbon doc in the western arctic ocean is greatly influenced by conservative riverine doc flux into the northern bering sea bering strait and beaufort sea as indicated by an inverse correlation with salinity based on the relations between doc salinity and seawater temperature several water masses could be identified these included riverine water ice melt water surface mixed water cold and saline shelf water and atlantic ocean water high concentrations of chlorophyll a and doc were found in some parcels of dense shelf water in barrow canyon in addition labile doc compounds such as polyunsaturated fatty acids pufa were found in the dense shelf water suggesting the dense shelf water contains a product marine organic matter of the biological co2 pump

circulation on the north central chukchi sea shelf abstract mooring and shipboard data collected between 1992 and 1995 delineate the circulation over the north central chukchi shelf previous studies indicated that pacific waters crossed the chukchi shelf through herald valley in the west and barrow canyon in the east we find a third branch through the central channel onto the outer shelf the central channel transport varies seasonally in phase with bering strait transport and is 0 2 sv on average although some of this might include water entrained from the outflow through herald valley a portion of the central channel outflow moves eastward and converges with the alaskan coastal current at the head of barrow canyon the remainder appears to continue northeastward over the central outer shelf toward the shelfbreak joined by outflow from herald valley the mean flow opposes the prevailing winds and is primarily forced by the sea level slope between the pacific and arctic oceans current variations are mainly wind forced but baroclinic forcing associated with upstream dense water formation in coastal polynyas might occasionally be important winter water mass modification depends crucially on the fall and winter winds which control seasonal ice development an extensive fall ice cover delays cooling limits new ice formation and results in little salinization in such years bering shelf waters cross the chukchi shelf with little modification in contrast extensive open water in fall leads to early and rapid cooling and if accompanied by vigorous ice production within coastal polynyas results in the production of high salinity 33 shelf waters such interannual variability likely affects slope processes and the transport of pacific waters into the arctic ocean interior

boundary undercurrent and water mass changes in the lincoln sea oceanographic measurements taken between 1989 and 1994 in the lincoln sea describe the currents and water mass structure along the continental slope of the arctic basin between the canadian and eurasian basins the measurements included periodic conductivity and temperature versus depth ctd profiles from ice camps ctd cross sections normal to the slope and year round current measurements analysis of this data describes the hydrographic structure of the waters over the continental slope and identifies some significant interannual variations an undercurrent confined to the continental slope with a width of about 50 km and speeds of 5 9 cm s 1 is shown in geostrophic current cross sections the presence of this easterly flow at depth is confirmed by current meter measurements and its existence has also been observed in the beaufort sea and the barents sea aagaard 1989 the waters within this undercurrent exhibit temperature salinity ts characteristics similar to canadian basin waters suggesting a boundary current system which is continuous along the continental slope north of alaska and canada significant interannual variations in temperature and salinity profiles may be related to variations in the large scale circulation of the arctic examination of the upper pycnocline waters over the slope between 1991 and 1994 indicated a relative temperature maximum overlying a minimum ts characteristics similar to waters attributed to bering sea origin found in the canadian basin these characteristics were not seen however during 1989 and 1990 suggesting a recent increase in the transport of surface waters from the canadian basin into the eurasian basin

holocene sea ice history and climate variability along the main axis of the northwest passage canadian arctic 1 palynological geochemical and physical records were used to document holocene paleoceanographic changes in marine sediment core from dease strait in the western part of the main axis of the northwest passage core 2005 804 006 pc latitude 68 59 552 n longitude 106 34 413 w quantitative estimates of past sea surface conditions were inferred from the modern analog technique applied to dinoflagellate cyst assemblages the chronology of core 2005 804 006 pc is based on a combined use of the paleomagnetic secular variation records and the cals7k 2 time varying spherical harmonic model of the geomagnetic field the age depth model indicates that the core spans the last 7700 cal years b p with a sedimentation rate of 61 cm ka 1 the reconstructed sea surface parameters were compared with those from barrow strait and lancaster sound cores 2005 804 004 pc and 2004 804 009 pc respectively which allowed us to draw a millennial scale holocene sea ice history along the main axis of the northwest passage manwp overall our data are in good agreement with previous studies based on bowhead whale remains however dinoflagellate sea surface based reconstructions suggest several new features the presence of dinoflagellate cysts in the three cores for most of the holocene indicates that the manwp was partially ice free over the last 10 000 years this suggests that the recent warming observed in the manwp could be part of the natural climate variability at the millennial time scale whereas anthropogenic forcing could have accelerated the warming over the past decades we associate holocene climate variability in the manwp with a large scale atmospheric pattern such as the arctic oscillation which may have operated since the early holocene in addition to a large scale pattern more local conditions such as coastal current tidal effects or ice cap proximity may have played a role on the regional sea ice cover these findings highlight the need to further develop regional investigations in the arctic to provide realistic boundary conditions for climatic simulations

pacific freshwater river water and sea ice meltwater across arctic ocean basins results from the 2005 beringia expedition 1 pacific water sea ice meltwater and river water are the primary sources of freshwater in the arctic ocean we have determined their relative fractions on a transect across the arctic ocean section 2005 expedition onboard ib oden which took place from 21 august to 23 september 2005 the transect began north of alaska continued through the central canada basin to the alpha ridge and into the makarov basin and ended in amundsen basin pacific freshwater and river water were the major sources of freshwater throughout the central canada basin and into makarov basin with river water fractions sometimes considerably higher than pacific water in the top 50 m pacific freshwater extended to depths of about 200 m pacific water found over the alpha ridge and in the amundsen basin is suggested to have been transported there in the transpolar drift the inventories of pacific freshwater and river water were roughly constant along the section through most of the canada and makarov basins river water fractions were greater than those of pacific freshwater in the amundsen basin sea ice meltwater fractions were negative reflecting net ice formation or near zero throughout most of the section a comparison of freshwater inventories with those at stations occupied during expeditions in 1991 1994 and 1996 indicated an increase in river water inventories in the makarov and amundsen basins on the eurasian side of the arctic ocean

calcium carbonate saturation states in the waters of the canadian arctic archipelago and the labrador sea 1 ocean acidification is predicted to occur first in polar oceans we investigated the saturation state of waters with respect to calcite cal and aragonite arg in six sections along an arctic outflow pathway through the canadian arctic archipelago caa and into the northwestern atlantic using dissolved inorganic carbon and total alkalinity measurements from 2003 to 2005 the study area a key region connecting the arctic and the north atlantic includes smith sound barrow strait baffin bay davis strait hudson strait and the labrador sea the average arg in the arctic outflow was 1 18 0 17 in barrow strait and 1 31 0 14 in smith sound with areas where arg 1 the arctic outflow through the caa has a high content of pacific waters which have a low saturation state these waters can be traced along the western baffin bay to davis strait south of davis strait this outflow is modified by mixing with slope and offshore waters of atlantic origin and with the outflow from hudson strait despite the mixing low saturation state water can still be identified on the southern labrador shelf the aragonite saturation horizon is found at 150 m in barrow strait at 200 m in baffin bay davis strait and hudson strait and at 2300 m in the labrador sea this study provides baseline data of the saturation states for the waters of the caa and the northwest atlantic it also illustrates the downstream evolution of low saturation state arctic outflow in the northwest atlantic

distribution of atlantic and pacific waters in the upper arctic ocean implications for circulation the atlantic and pacific oceans provide source waters for the arctic ocean that can be distinguished by their differing nitrate and phosphate concentration relationships using these relationships we estimate the amount of atlantic and pacific waters in the surface layer top 30 m of the arctic ocean atlantic source water is dominant in most of the eurasian basin and is present in significant amounts in the makarov basin north of the east siberian sea pacific source water is dominant in most of the canadian basin and is present in significant amounts in the amundsen basin north of greenland we deduce circulation patterns from the distributions of atlantic and pacific source waters in the surface layer of the arctic ocean and conclude that the flow within the surface layer differs from ice drift along the north american and european boundaries of the polar basin

freshwater composition of the waters off southeast greenland and their link to the arctic ocean 1 the freshwater composition of waters on the southeast greenland shelf and slope are described using a set of high resolution transects occupied in summer 2004 which included hydrographic velocity nutrient and chemical tracer measurements the nutrient and tracer data are used to quantify the fractions of pacific water sea ice melt and meteoric water present in the upper layers of the east greenland current egc and east greenland coastal current egcc the egc egcc system dominates the circulation of this region and strongly influences the observed distribution of the three freshwater types sea ice melt and meteoric water fractions are surface intensified reflecting their sources and generally increase southward from denmark strait to cape farewell as well as shoreward significant fractions of pacific water are found in the subsurface layers of the egcc supporting the idea that this inner shelf branch is directly linked to the egc and thus to the arctic ocean a set of historical sections is examined to investigate the variability of pacific water content in the egc and egcc from 1984 to 2004 in the vicinity of denmark strait the fraction of pacific water increased substantially in the late 1990s and subsequently declined to low levels in 2002 and 2004 mirroring the reduction in pacific water content reported previously at fram strait this variability is found to correlate significantly with the arctic oscillation index lagged by 9 years suggesting that the arctic ocean circulation patterns bring varying amounts of pacific water to the north atlantic via the egc egcc

coupled nitrification denitrification in sediment of the eastern bering sea shelf leads to 15n enrichment of fixed n in shelf waters 1 we studied the nitrogen biogeochemistry of the ice covered eastern bering sea shelf using the isotope ratios 15n 14n and 18o 16o of no3 and other n species the 15n 14n of late winter no3 on the shelf decreases inshore and is inversely correlated with bottom water nh4 consistent with an input of low 15n 14n no3 from partial nitrification of nh4 remineralized from the sediments an inshore 15n 14n increase in total dissolved n tdn suggests that 1 the sediment derived nh4 is elevated in 15n due to the same partial nitrification that yields the low 15n 14n no3 and 2 15n deplete no3 from partial nitrification within the sediments is denitrified to n2 the proportion of newly nitrified no3 on the shelf evidenced by an inshore decrease in no3 18o 16o is correlated with the n deficit further implicating nitrification coupled to denitrification however a simple n isotope budget indicates a comparable rate of denitrification supported by diffusion of no3 into the sediments the isotopic impact of benthic n loss is further demonstrated by a correlation between the 15n 14n of shelf surface sediment and the n deficit of the overlying water column both of which increase inshore and northward as well as by arctic no3 isotope data indicating that the fixed n transported through bering strait has a 15n 14n higher than is found in the open bering sea the significant net isotope effect of benthic n loss on the bering shelf 6 8 is at odds with previous assumptions regarding the global ocean s n isotope budget

methane and nitrous oxide distributions across the north american arctic ocean during summer 2015 we collected arctic ocean water column samples for methane ch4 and nitrous oxide n2o analysis on three separate cruises in the summer and fall of 2015 covering a 10 000 km transect from the bering sea to baffin bay this provided a three dimensional view of ch4 and n2o distributions across contrasting hydrographic environments from the oligotrophic waters of the deep canada basin and baffin bay to the productive shelves of the bering and chukchi seas percent saturation relative to atmospheric equilibrium ranged from 30 800 for ch4 and 75 145 for n2o with the highest concentrations of both gases occurring in the northern chukchi sea nitrogen cycling in the shelf sediments of the bering and chukchi seas likely constituted the major source of n2o to the water column and the resulting high n2o concentrations were transported across the arctic ocean in eastward flowing water masses methane concentrations were more spatially heterogeneous reflecting a variety of localized inputs including likely sources from sedimentary methanogenesis and sea ice processes unlike n2o ch4 was rapidly consumed through microbial oxidation in the water column as shown by the 13c enrichment of ch4 with decreasing concentrations for both ch4 and n2o sea air fluxes were close to neutral indicating that our sampling region was neither a major source nor sink of these gases our results provide insight into the factors controlling the distribution of ch4 and n2o in the north american arctic ocean and an important baseline data set against which future changes can be assessed

the role of sea ice and other fresh water in the arctic circulation salinity stratification is critical to the vertical circulation of the high latitude ocean we here examine the control of the vertical circulation in the northern seas and the potential for altering it by considering the budgets and storage of fresh water in the arctic ocean and in the convective regions to the south we find that the present day greenland and iceland seas and probably also the labrador sea are rather delicately poised with respect to their ability to sustain convection small variations in the fresh water supplied to the convective gyres from the arctic ocean via the east greenland current can alter or stop the convection in what may be a modern analog to the halocline catastrophes proposed for the distant past the north atlantic salinity anomaly of the 1960s and 1970s is a recent example it must have had its origin in an increased fresh water discharge from the arctic ocean similarly the freshening and cooling of the deep north atlantic in recent years is a likely manifestation of the increased transfer of fresh water from the arctic ocean into the convective gyres finally we note that because of the temperature dependence of compressibility a slight salinity stratification in the convective gyres is required to efficiently ventilate the deep ocean

retreat of the cold halocline layer in the arctic ocean we present a comparison of arctic ocean hydrographic data sets from the 1990s with a focus on changes in the upper few hundred meters of the eurasian basin the most recent observations discussed here were collected during the spring 1995 scientific ice expedition scicex 95 the second in a series of scientific cruises to the arctic ocean aboard u s navy nuclear submarines although the 1990s have seen an abundance of synoptic cruises to the arctic this was the only one to take place in winter spring conditions other data considered here were collected during the first scicex cruise in summer 1993 scicex 93 and during an icebreaker cruise to the eurasian basin in summer 1991 oden 91 a new russian american winter climatology is also used as a reference these comparisons reveal that the eurasian basin cold halocline layer has retreated during the 1990s to cover significantly less area than in previous years specifically we find a retreat from the amundsen basin back into the makarov basin the latter is the only region with a true cold halocline layer during scicex 95 changes are also seen in other halocline types and in the atlantic water layer heat content and depth since the cold halocline layer insulates the surface layer and thus the overlying sea ice from the heat contained in the atlantic water layer this should have profound effects on the surface energy and mass balance of sea ice in this region using a simple mixing model we calculate maximum ice ocean heat fluxes of 1 3 w m 2 in the eurasian basin where during scicex 95 the surface layer lay in direct contact with the underlying atlantic water layer the overall cause of water mass changes in the 1990s might have been a shift in the atmospheric wind forcing and resulting sea ice motion during the late 1980s which we speculate influenced the location where fresh shelf waters flow into the deeper basins of the arctic ocean finally we discuss two different mechanisms that have been proposed for cold halocline water formation and we propose a compromise that best fits these data

waters of the makarov and canada basins abstract hydrographic measurements from the 1994 arctic ocean section show how the makarov and canada basins of the arctic ocean are related and demonstrate their oceanographic connections to the eurasian basin the inflow into the makarov basin consists largely of well ventilated water within a broad band of densities from a boundary flow over the siberian end of the lomonosov ridge the boundary flow contains a significant component of dense shelf water likely originating in the barents kara and laptev seas earlier ice camp data show that the canada basin is relatively more isolated from this ventilation source in the canada basin shelf sources influenced by bering sea water appear to add cold waters with high silicate concentrations to the halocline and deeper in 1994 the halocline silicate maximum over the central makarov basin was absent evidence of the recent displacement of the upper s 33 1 halocline water from the chukchi east siberian sea region by water from the eurasian basin much of the makarov basin water in and below the halocline is in fact from the eurasian basin with admixture of waters from the canada basin suggested by their higher silicate concentrations mid depth eddies may transport anomalous properties into the central arctic and create property gradients or fronts in mid depth and deep waters the complex topography of the mendeleyev ridge chukchi plateau region also may assist spreading of water from the boundary into the interior atlantic layer characteristics in 1994 differed from previous general depictions in particular the core temperatures at the chukchi mendeleyev boundary were at least 0 2 c warmer on average than indicated in earlier work the recent warming at intermediate depth has resulted from inflow of atlantic waters that have been cooled relatively little during their transit of the norwegian sea

effect of geo pedological conditions on the distribution and chemical speciation of selected trace elements in forest soils of western alborz iran abstract geologic and pedologic controls have an important influence on the abundance distribution and behavior of elements in natural soil environments in order to assess the role of these factors on distribution and chemical speciation of selected trace elements in soil soils on six parent materials including phyllite tonalite peridotite dolerite shale and limestone were sampled in western alborz in iran soil genesis and development of representative residual pedons were studied for each parent material and the total content of si al fe ca mg co cr cu mn ni pb v and zn were compared enrichment depletion patterns of trace elements were assessed using ti as the reference element and lowest horizon as the reference layer a modified bcr european community bureau of reference sequential extraction procedure was used to fractionate the elements into four operationally defined species the total contents of co cr ni and v are highest in soils derived from peridotite 53 984 285 and 204 mg kg 1 respectively and dolerite 39 1023 176 and 185 mg kg 1 respectively lead and zn contents are highest in soils derived from shale 27 and 106 mg kg 1 respectively which is probably due to the high sorption capacity of clay different elements exhibited very different enrichment depletion patterns in a given pedon moreover depth distribution patterns differed also for a given element among soils with different parent material and even showed considerable variation among soils with similar lithology lead zn cu and mn have been generally enriched in most pedons except in some acidic and strongly leached soils whereas co cr fe ni and v have been leached especially from dystrudepts and eutrudepts the latter elements however showed enrichment trend in hapludalfs and argiudolls parallel to the development of illuvial b horizons iron cr cu ni v and zn are present primarily in the residual fraction independent of soil and parent material type whereas mn pb and co were mainly present in the non residual fractions of most pedons trace element concentrations in the soils of the study area are related primarily to the parent material type while pedogenic processes appear to have played a minor role

oceanographic regime shift during 1997 in disko bay western greenland data from a long time series of temperature salinity and nutrient measurements in disko bay west greenland reveal a marked change in the water characteristics during recent years seasonal dynamics in the upper 150 m of the water column were highly affected by the seasonality in meteorological conditions while the deeper water strata were more stable and were primarily influenced by large scale circulation patterns there was a marked increase in the average water temperatures at 200 m depth in spring 1997 with the long term average increasing from 1 30 c to 2 25 c weekly data from 1996 to 1997 show that the sudden change in bottom water occurred in april 1997 due to the inflow of a larger proportion of north atlantic water which propagated north along the coast before entering the bay further support for this inflow was found when tracing the relative proportion of atlantic water in the bay using inorganic nutrients these changes in the oceanography of the bay will not only lead to further glacial retreat but will also affect the local marine ecosystem by changing the relative dominance of major copepod species that overwinter in bottom waters of the bay

wind driven transport pathways for eurasian arctic river discharge distributions of temperature salinity and barium in near surface waters depth 50 m of the laptev sea and adjacent areas of the arctic ocean are presented for the summers of 1993 1995 and 1996 the tracer data indicate that while fluvial discharge was largely confined to the shelf region of the laptev sea in the summer of 1993 surface waters containing a significant fluvial component extended beyond the shelf break and over the slope and basin areas north of the laptev sea in the summers of 1995 and 1996 these distributions of fluvial discharge are consistent with local winds and suggest two principal pathways by which river waters can enter the central arctic basins from the laptev sea when southerly to southeasterly wind conditions prevail river waters are transported northward beyond the shelf break and over the slope and adjacent basin areas these waters can then enter the interior arctic ocean via upper layer flow in the vicinity of the lomonosov ridge under other wind conditions river waters are steered primarily along the inner laptev shelf and into the east siberian sea as part of the predominantly eastward coastal current system these waters then appear to cross the shelf and enter the interior arctic ocean via upper layer flow aligned roughly along the mendeleyev ridge the extent to which either pathway is favored in a given year is largely determined by local wind patterns during the summer months when fluvial discharge is greatest and shelf waters are at the lowest salinity of their annual cycle

pathways of pacific water across the chukchi sea a numerical model study 1 pathways of pacific water flowing from the north pacific ocean through bering strait and across the chukchi sea are investigated using a two dimensional barotropic model in the no wind case the flow is driven only by a prescribed steady northward flow of 0 8 sv through bering strait the resulting steady state circulation consists of a broad northeasterly flow basically following the topography with a few areas of intensified currents about half of the inflow travels northwest through hope valley while the other half turns somewhat toward the northeast along the alaskan coast the flow through hope valley is intensified as it passes through herald canyon but much of this flow escapes the canyon to move eastward joining the flow in the broad valley between herald and hanna shoals another area of slightly intensified currents there is a confluence of nearly all of the flow along the alaskan coast west of pt barrow to create a very strong and narrow coastal jet that follows the shelf topography eastward onto the beaufort shelf thus in this no wind case nearly all of the pacific water entering the chukchi sea eventually ends up flowing eastward along the narrow beaufort shelf with no discernable flow across the shelf edge toward the interior canada basin travel times for water parcels to move from bering strait to pt barrow vary tremendously according to the path taken e g less than 6 months along the alaskan coast but about 30 months along the westernmost path through herald canyon this flow field is relatively insensitive to idealized wind forcing when the winds are from the south west or north in which cases the shelf transports tend to be intensified however strong northeasterly to easterly winds are able to completely reverse the flows along the beaufort shelf and the alaskan coast and force most of the throughflow in a more northerly direction across the chukchi sea shelf edge potentially supplying the surface waters of the interior canada basin with pacific water the entire shelf circulation reacts promptly to changing wind conditions with a response time of 2 3 days the intense coastal jet between icy cape and pt barrow implies that dense water formed here from winter coastal polynyas may be quickly swept away along the coast in contrast there is a relatively quiet nearshore region to the west between cape lisburne and icy cape where dense water may accumulate much longer and continue to become denser before it is carried across the shelf

two configurations of the western arctic shelfbreak current in summer abstractdata from a closely spaced array of moorings situated across the beaufort sea shelfbreak at 152 w are used to study the western arctic shelfbreak current with emphasis on its configuration during the summer season two dynamically distinct states of the current are revealed in the absence of wind with each lasting approximately one month the first is a surface intensified shelfbreak jet transporting warm and buoyant alaskan coastal water in late summer this is the eastward continuation of the alaskan coastal current it is both baroclinically and barotropically unstable and hence capable of forming the surface intensified warm core eddies observed in the southern beaufort sea the second configuration present during early summer is a bottom intensified shelfbreak current advecting weakly stratified chukchi summer water it is baroclinically unstable and likely forms the middepth warm core eddies present in the interior basin the mesoscale instabilities extract energy from the mean flow such

long term coordinated changes in the convective activity of the north atlantic the north atlantic is a peculiarly convective ocean the convective renewal of intermediate and deep waters in the labrador sea and greenland iceland sea both contribute significantly to the production and export of north atlantic deep water thus helping to drive the global thermohaline circulation while the formation and spreading of 18 degree water at shallow to intermediate depths off the us eastern seaboard is a major element in the circulation and hydrographic character of the west atlantic for as long as time series of adequate precision have been available to us it has been apparent that the intensity of convection at each of these sites and the hydrographic character of their products have been subject to major interannual change as shown by aagaard 1968 clarke et al 1990 and meincke et al 1992 for the greenland sea in the ows bravo record from the labrador sea eg lazier 1980 et seq and at the panulirus hydrostation s site in the northern sargasso off bermuda eg jenkins 1982 talley and raymer 1982 this paper reviews the recent history of these changes showing that the major convective centres of the greenland and labrador seas are currently at opposite convective extrema in our postwar record with vertical exchange at the former site limited to 1000 m or so but with labrador sea convection reaching deeper than previously observed to over 2300 m as a result greenland sea deep water has become progressively warmer and more saline since the early 70 s due to increased horizontal exchange with the arctic ocean through fram strait while the labrador sea water has become progressively colder and fresher over the same period through increased vertical exchange most recently convection has become deep enough there to reach into the more saline nadw which underlies it so that cooler but now saltier and denser lsw has resulted

processes of multibathyal aragonite undersaturation in the arctic ocean during three years of study 2010 2012 the western arctic ocean was found to have unique aragonite saturation profiles with up to three distinct aragonite undersaturation zones this complexity is produced as inflow of atlantic and pacific derived water masses mix with arctic derived waters which are further modified by physiochemical and biological processes the shallowest aragonite undersaturation zone from the surface to 30 m depth is characterized by relatively low alkalinity and other dissolved ions besides local influence of biological processes on aragonite undersaturation of shallow coastal waters the nature of this zone is consistent with dilution by sea ice melt and invasion of anthropogenic co2 from the atmosphere a second undersaturated zone at 90 220 m depth salinity 31 8 35 4 occurs within the arctic halocline and is characterized by elevated pco2 and nutrients the nature of this horizon is consistent with remineralization of organic matter on shallow continental shelves bordering the canada basin and the input of the nutrients and co2 entrained by currents from the pacific inlet finally the deepest aragonite undersaturation zone is at greater than 2000 m depth and is controlled by similar processes as deep aragonite saturation horizons in the atlantic and pacific oceans the comparatively shallow depth of this deepest aragonite saturation horizon in the arctic is maintained by relatively low temperatures and stable chemical composition understanding the mechanisms controlling the distribution of these aragonite undersaturation zones and the timescales over which they operate will be crucial to refine predictive models this article is protected by copyright all rights reserved

a 600 ka arctic sea ice record from mendeleev ridge based on ostracodes arctic paleoceanography and sea ice history were reconstructed from epipelagic and benthic ostracodes from a sediment core hly0503 06jpc 800 m water depth located on the mendeleev ridge western arctic ocean the calcareous microfaunal record ostracodes and foraminifers covers several glacial interglacial cycles back to estimated marine isotope stage 13 mis 13 500 ka with an average sedimentation rate of 0 5 cm ka for most of the stratigraphy mis 5 13 results based on ostracode assemblages and an unusual planktic foraminiferal assemblage in mis 11 dominated by a temperate water species turborotalita egelida show that extreme interglacial warmth high surface ocean productivity and possibly open ocean convection characterized mis 11 and mis 13 400 and 500 ka respectively a major shift in western arctic ocean environments toward perennial sea ice occurred after mis 11 based on the distribution of an ice dwelling ostracode acetabulastoma arcticum spectral analyses of the ostracode assemblages indicate sea ice and mid depth ocean circulation in western arctic ocean varied primarily at precessional 22 ka and obliquity 40 ka frequencies

shelfbreak current over the canadian beaufort sea continental slope wind driven events in january 2005 the shelfbreak current over the beaufort sea continental slope is known to be one of the most energetic features of the beaufort sea hydrography in january 2005 three oceanographic moorings deployed over the canadian eastern beaufort sea continental slope simultaneously recorded two consecutive shelfbreak current events with along slope eastward bottom intensified flow up to 120 cm s 1 both events were generated by the local wind forcing associated with two pacific born cyclones passing north of the beaufort sea continental slope toward the canadian archipelago over the mooring array the associated westerly wind exceeded 15 m s 1 these two cyclones generated storm surges along the beaufort sea coast with sea surface height ssh rising up to 1 4 m following the two westerly wind maxima we suggest that the westerly along slope wind generated a surface ekman onshore transport the associated ssh increase over the shelf produced a cross slope pressure gradient that drove an along slope eastward geostrophic current in the same direction as the wind this wind driven barotropic flow was superimposed on the background baroclinic bottom intensified shelfbreak current that consequently amplified summer fall satellite altimetry data for 1992 2013 show that the ssh gradient in the southeastern beaufort sea is enhanced over the upper continental slope in response to frequent storm surge events because the local wind forcing and or sea ice drift could not explain the reduction of sea ice concentration over the beaufort sea continental slope in january 2005 we speculate that wind driven sea level fluctuations may impact the sea ice cover in winter

the terrane concept and its manifestation by deep reflection studies in the variscides summary the terrane concept is understood as an important extension of plate tectonics and is based on the recognition of allochthonous mobile geological units the concept is successfully applied to the variscides with their wide range of collisional belts it is mainly supported by the dense deep seismic network of dekorp which reveals certain reflectivity patterns and succeeds in mapping old and new deep fault zones between the terranes variscan terranes are rooted in the ductile lower crust and seem to consist of continental crust only partly exclusively of rigid upper crust oceanic terranes on the other hand are always rooted in the asthenosphere the development of continental terranes and their boundaries depends strongly on their thermal and rheological history in the case of post orogenic collapse with heating and extension of the lower crust seismic lamellae develop and often truncate former thrust faults