sediment distribution pattern of the south caspian sea possible hydroclimatic implications the south caspian subbasin extends from the foot of the alborz mountains to the deepest part of caspian sea the lithological background and tectonic setting of the study area primarily control the

reconstructions of deltaic environments from holocene palynological records in the volga delta northern caspian sea new palynological and ostracod data are presented from the holocene volga delta obtained from short cores and surface samples collected in the damchik region near astrakhan russian federation in the northern caspian sea four phases of delta deposition are recognized and constrained by accelerated mass spectrometry ams radiocarbon ages palynological records show that erosive channels dunes baer hills and inter dune lakes were present during the period 11 500 8900 cal bp at the time of the mangyshlak caspian lowstand the period 8900 3770 cal bp was characterized regionally by extensive steppe vegetation with forest present at times with warmer more humid climates and with halophytic and xerophytic vegetation present at times of drought the period 3770 2080 cal bp was a time of active delta deposition with forest or woodland close to the delta indicating relatively warm and humid climates and variable caspian sea levels from 2080 cal bp to the present day aquatic pollen is frequent in highstand intervals and herbaceous pollen and fungal hyphae frequent in lowstand intervals soils and incised valley sediments are associated with the regional derbent regression and may be time equivalent with the medieval warm period fungal spores are an indicator of erosional or aeolian processes whereas fungal hyphae are associated with soil formation freshwater algae ostracods and dinocysts indicate mainly freshwater conditions during the holocene with minor brackish influences dinocysts present include spiniferites cruciformis caspidinium rugosum impagidinium caspienense and pterocysta cruciformis the latter a new record for the caspian sea the holocene volga delta is a partial analogue for the much larger oil and gas bearing mio pliocene palaeo volga delta

the interpretation of secular caspian sea level records during the holocene abstract the caspian sea cs experienced significant changes during the holocene the standard deviation for caspian sea level csl variations over that interval is estimated as 1 4 m based on well established views they were climate induced variations there are no clear links with the calendar of climatic anomalies and climate models do not reproduce the changes therefore the question about the origin of secular csl fluctuations remains open based on general ideas about the laws of temporal dynamics relating to massive inertial objects the observed slow changes of the csl under the semi steady climate state of the holocene can be represented as resulting from the accumulation of small anomalies in the water regime as a kind of self developing system to test this hypothesis the model of the water balance of the cs was used time scale for the sea fluctuations was estimated as 20 years this model is interpreted as stochastic and from this perspective it is a langevin equation that incorporates the action of precipitation and evaporation as random white noise so that the whole can be thought of as an analogue of brownian motion under these conditions the cs is represented by a system undergoing random walk modeling results are interpreted from the probabilistic point of view although the model is deterministically based on the physical law of conservation of water mass the results showed that the csl fluctuations under steady state conditions are characterized by 1 1 m close to the empirical value super large anomalies in csl are not prohibited by the theory but their development requires a correspondingly long time however during long periods of time background conditions change and uniformity of the brownian process becomes disrupted the origin of large transgressive regressive stages can be different for example the low stand of the enotaevkian regression during the lgm was determined by a significant reduction in precipitation over the volga river catchment and by a corresponding reduction in the volume of river runoff hence based on modeling results the possibility of self development effects is not prohibited by the theory there need not be any cause for specific level changes or shifts merely the expected behavior of red noise processes

an investigation of local scale human landscape dynamics in the endorheic alluvial fan of the murghab river turkmenistan abstract endorheic or inland deltas commonly found across the deserts of central asia represent unique and dynamic ecotones that are still not fully understood these regions of environmental and landscape transition as well as social liminality straddle the line between fertile sustainable environments and less productive desertic regions less capable of sustaining significant human occupation because such boundary areas are dynamic and often unpredictable they are excellent case studies through which to study the complex processes that have characterized human environmental relationships throughout the late holocene this paper focuses on the local variability that characterizes these relationships in one such region the terminal fan of the murghab river in turkmenistan populated since at least the late 5th millennium bp and likely earlier the region has been variously described as an oasis environment in which desertic processes have been more or less stagnant throughout the late holocene or alternatively as a fertile continuously occupied and heavily cultivated alluvial fan in which desertification was a relatively late process intensifying only in the mid 4th millennium bp this paper presents geoarchaeological data from a series of test pits in the distal portion of the terminal fan to show that local scale analysis indicates a far more complex interpretation one shaped by the continuous and non uniform interaction of aeolian and alluvial depositional environments and one that bears substantially on human landscape dynamics in the region the late holocene development of the distal fan is examined using proxy data from granulometric analysis loss on ignition loi and geochemical analysis as well as a series of new osl dates that refines the depositional chronology of the region ultimately we show that landscape change throughout the holocene has been characterized by pronounced variability at the local level not fully described by regional scale approaches while differential aeolian encroachment non uniform alluvial processes and climatic conditions bear significantly on the initial conditions for human occupation human environmental processes are ultimately co evolutionary in nature

a record of late quaternary continental weathering in the sediment of the caspian sea evidence from u th sr isotopes trace element and palynological data abstract this study presents combined mineralogical chemical isotopic 87sr 86sr and u th disequilibria series and palynological analyses on bulk sediments and on distinct mineral phases carbonates and clays from a 10 m long core drilled in the southern caspian sea and containing a late pleistocene and early holocene record the data allowed identifying 1 the main variations in sedimentation 2 the processes causing these variations 3 the modification of erosion vs weathering and 4 the influence of climatic and or caspian sea level changes in the region since the late pleistocene the chemical and mineralogical results allowed the division of the sedimentary sequence into three main units and a transition zone the lower unit unit u1 primarily consists of silicate and carbonate rich detritus sedimentation characteristics including observation of detritus in secular equilibrium are relatively constant within this unit and reflect mechanical erosion in a cold climate unit u1 probably corresponds to a glacial period when the vegetation cover was sparse and wind and river transport of pollen were strong subsequently global increase in temperatures has greatly modified the sedimentation in the caspian sea south basin biogenic sedimentation is higher in units u2 and u3 and detrital inputs varied from unit u1 variations in detrital input are likely to be caused by decreasing aeolian contribution and by relative changes in river volumes and origins the study of the bulk sediments clays and carbonates reflects an increase in chemical weathering since about 10 14c ka bp ago base of unit u2 in line with an increase in the vegetation cover our results suggest an evolution of continental weathering conditions in the catchment area of the caspian sea from dominantly mechanical physical erosion during the cold period to a continuous increase in weathering since the lateglacial period as climate improved which illustrates the strong relation between climate vegetation cover and weathering processes this paper also highlights how the u th disequilibrium series proxy combined with other geochemical and palynological studies could be a useful tool to record and constrain the modification of weathering regime in response to climatic and environmental changes at regional scale

review of magnetic and electric field effects near active faults and volcanoes in the u s a abstract synchronized measurements of geomagnetic field have been recorded along 800 km of the san andreas fault and in the long valley caldera since 1974 and during eruptions on mount st helens since 1980 for shorter periods of time continuous measurements of geoelectric field measurements have been made on mount st helens and near the san andreas fault where moderate seismicity and fault slip frequently occurs significant tectonic and volcanic events for which nearby magnetic and electric field data have been obtained include 1 two moderate earthquakes m l 5 8 for which magnetometers were close enough to expect observable signals about three source lengths 2 one moderate earthquake m s 7 3 for which magnetometers were installed as massive fluid outflow occurred during the post seismic phase 3 numerous fault creep events and moderate seismicity 4 a major explosive volcanic eruption and numerous minor extrusive eruptions and 5 an episode of aseismic uplift for one of the two earthquakes with m l 5 8 seismomagnetic effects of 1 3 and 0 3 nt were observed for this event magnetometers were optimally located near the epicenter and the observations obtained are consistent with simple seismomagnetic models of the event similar models for the other event indicate that the expected seismomagnetic effects are below the signal resolution of the nearest magnetometer precursive tectonomagnetic effects were recorded on two independent instruments at distances of 30 and 50 km from a m l 5 2 earthquake longer term changes were recorded in one region in southern california where a moderate m l 5 9 earthquake has since occurred surface observations of fault creep events have no associated magnetic or electrical signature above the present measurement precision 0 25 nt and 0 01 respectively and are consistent with near surface fault failure models of these events longer term creep is sometimes associated with corresponding longer term magnetic field perturbations correlated changes in gravity magnetic field areal strain and uplift occurred during episodes of aseismic deformation in southern california primarily between 1979 and 1983 because the relationships between these parameters agrees with those calculated from simple deformation and tectonomagnetic models the preferred explanation appeals to short term strain episodes independently detected in each data set an unknown source of meteorologically generated noise in the strain gravity and uplift data and an unknown but correlated disturbance in the absolute magnetic data might also explain the data no clear observations of seismoelectric or tectonoelectric effects have yet been reported the eruption of mount st helens generated large oscillatory fields and 9 2 nt offset on the only surviving magnetometer a large scale traveling magnetic disturbance passed through the san andreas array from 1 to 2 h after the eruption subsequent extrusive eruptions generated small precursory magnetic changes in some cases these data are consistent with a simple volcanomagnetic model magneto gas dynamic effects and a blast excited traveling ionospheric disturbance traveling ionospheric disturbances tids also generated by earthquake related atmospheric pressure waves may explain many electromagnetic disturbances apparently associated with earthquakes local near fault magnetic field transients rarely exceed a few nt at periods of a few minutes and longer

the relationship between current and paleo groundwater base levels abstract base levels are basically divided into two categories oceanic and marine base levels and continental terminal endorheic ones the marine domain serves as the ultimate base level for both surface and groundwater drainage systems continental inland depressions very often serve as terminal endorheic base levels to both surface drainage and groundwater systems many of the current both marine and inland base levels served also in the past as paleo base levels fluctuations of base level elevations affect the adjoined groundwater system in several ways such as changes in groundwater levels location of divides depths of fresh saline water interfaces and the amount of flow to the base levels this paper provides examples from many different parts of the world that describe the relationship between current and paleo base levels the examples include marine base levels as well as inland endorheic ones both currently above and below sea level close to and distant from the sea

piezornagnetic field for parkfield fault model a theoretical piezomagnetic field is calculated as a function of time and ground position for an earthquake instability model applied to moderate m 6 earthquakes on the san andreas fault near parkfield california the instability model simulates fault slip and stress for all parts of a 32 year earthquake cycle including unstable mainshock slip mainshock slip occurs when a nearly locked patch of the fault becomes sufficiently loaded by surrounding aseismic slip that it reaches a condition of rapid failure the piezomagnetic field is calculated directly from fault slip using analytic solutions based on piezomagnetic nuclei that are analogous to strain nuclei during the interseismic interval increasing stress concentration on the locked patch is accompanied by a gradual evolution of the magnetic anomaly field leading to maximum cumulative changes of about 2 nt in the vicinity of the pending epicenter mainshock slip cancels about half of the interseismically accumulated changes and rapid post seismic relaxation cancels most of the rest at certain sites near the locked patch the rate of change of the field progressively increases during the interseismic interval while at others it progressively decreases this effect is most pronounced during the last 3 4 years before the mainshock and at suitably chosen pairs of sites results in reversal of the temporal trend of the differential field such reversals if separable from geomagnetic variation due to other sources would constitute precursory indicators of approaching failure

mollusc biodiversity in late holocene nearshore environments of the caspian sea a baseline for the current biodiversity crisis the caspian sea is an evolutionary island whose rich and endemic fauna have evolved in partial isolation over the past two million years baseline studies of pre 20th century communities are needed in order to assess the severity of the current caspian biodiversity crisis which mostly involves invasive species an inventory of late holocene shelly assemblages c 2000 2500 cal yr bp from outcrops in and around great turali lake dagestan russia shows a diverse nearshore community consisting of 24 endemic caspian species two invasive species and two caspian native species that lived in a shallow embayment with mesohaline salinities of circa 5 13 psu parts per thousands this pre crisis holocene caspian mollusc community serves as a baseline against which modern mollusc diversity measurements can be evaluated examination of faunas from similar environments living today and in the past illustrates the dramatic changes in nearshore communities during the 20th century our study identifies a habitat that may have served as a refuge but that is currently under threat from invasive species the severity of the caspian biodiversity crisis is comparable with other well known biodiversity crises in semi isolated ecosystems such as the cichlid fish communities of lake victoria africa

middle and late quaternary glacial lake outburst floods drainage diversions and reorganization of fluvial systems in northwestern eurasia abstract the middle and late pleistocene glaciations of northern eurasia had a great impact on the evolution of the modern drainage system this paper presents a review and synthesis on the palaeogeography of glacial lakes their drainage and impact on the re organization of the drainage systems during the last two glacial interglacial cycles we will focus on four regions 1 northern central europe and fennoscandia 2 the central part of the east european plain 3 the west siberian plain and 4 the aral caspian black sea area the main findings of the last decade s include the improved chronology of some major river system formation and of meltwater overflows across the continental drainage divides major drainage systems of the north central and west central part of the east european plain upper volga upper dnieper formed due to overspill of glacial lakes in late mis 6 with a partial re organization upper dnieper in mis 2 the aral caspian black sea cascade acted as a sink for glacial meltwater from the north the major meltwater yield to the aral and caspian seas occurred in mis 6 and late mis 5 in mis 2 the meltwater delivery via the volga valley into the caspian sea was low and therefore had only a minor influence on the sea level considerable meltwater discharge to the black sea through the dnieper river system occurred around the maximal stage of the mis 2 glaciation and ceased very quickly after the onset of deglaciation

seismomagnetic observation during the 8 july 1986 magnitude 5 9 north palm springs earthquake a differentially connected array of 24 proton magnetometers has operated along the san andreas fault since 1976 seismomagnetic offsets of 1 2 and 0 3 nanotesla were observed at epicentral distances of 3 and 9 kilometers respectively after the 8 july 1986 magnitude 5 9 north palm springs earthquake these seismomagnetic observation are the first obtained of this elusive but long anticipated effect the data are consistent with a seismomagnetic model of the earthquake for which right lateral rupture of 20 centimeters is assumed on a 16 kilometer segment of the banning fault between the depths of 3 and 10 kilometers in a region with average magnetization of 1 ampere per meter alternative explanations in terms of electrokinetic effects and earthquake generated electrostatic charge redistribution seem unlikely because the changes are permanent and complete within a 20 minute period

late pleistocene to holocene evolution of the emba delta kazakhstan and coastline of the north eastern caspian sea sediment ostracods pollen and dinoflagellate cyst records six cores each approximately 10 m long of late pleistocene to holocene age were studied from the emba delta region in the north eastern caspian sea radiocarbon dates provide ages within the range of 47 820 to 12 020 cal bp for the middle sections and for post 1950 close to surface the ages fall within marine isotope stage mis 3 mis 2 and mis 1 with mis 4 also inferred four lithological units are present each separated by an erosional contact unit 4 is equated with mis 4 and consists of over consolidated east west trending aeolian sands deposited during the late pleistocene atelian lowstand unit 3 is equated with mis 3 and is a low energy shallow open water or lagoonal deposit based on ostracod faunas pollen from mesophilic trees is common confirming warm climatic conditions floristic elements such as engelhardia and carya were shared with east asia frequent taxodiaceae pollen occurs derived from glyptostrobus pensilis a seasonal freshwater swamp tree now found naturally only in isolated relict stands in east asia this suggests that the north eastern caspian region was a refugium supporting glyptostrobus swamp vegetation during mis 3 there is no evidence to indicate that these are reworked occurrences unit 2 consists of early khvalynian transgressive barrier sands and unit 1 of shoreface sands and muds of holocene age the late khvalynian highstand and the last glacial maximum lgm record are eroded by the mangyshlak unconformity after ca 12 500 cal bp the holocene interval contains frequent foraminifera and dinoflagellate cysts dinocysts of restricted marine affinity e g lingulodinium machaerophorum the dinocysts pterocysta cruciformis and impagidinium inaequalis are found commonly in the caspian sea for the first time results are compared with palynological and ostracod assemblages in surface samples from the eastern caspian sea coastal region

intrusion of warm bering chukchi waters onto the shelf in the western beaufort sea 1 wind driven changes in the path of warm bering chukchi waters carried by the alaska coastal current acc through barrow canyon during late summer are described from high resolution hydrography acoustic doppler current profiler measured currents and satellite measured sea surface temperature imagery acquired from mid august to mid september 2005 2007 near barrow alaska numerical simulations are used to provide a multidecadal context for these observational data four generalized wind regimes and associated circulation states are identified when winds are from the east or east southeast the acc jet tends to be relatively strong and flows adjacent to the shelf break along the southern flank of barrow canyon these easterly winds drive inner shelf currents northwestward along the alaskan beaufort coast where they oppose significant eastward intrusions of warm water from barrow canyon onto the shelf because these easterly winds promote sea level set down over the beaufort shelf and upwelling along the beaufort slope the acc jet necessarily becomes weaker broader and displaced seaward from the beaufort shelf break upon exiting barrow canyon winds from the northeast promote separation of the acc from the southern flank of barrow canyon and establish an up canyon current along the southern flank that is fed in part by waters from the western beaufort shelf when winds are weak or from the southwest warm bering chukchi waters from barrow canyon intrude onto the western beaufort shelf

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

simulating long term caspian sea level changes the impact of holocene and future climate conditions to improve our understanding of the relationship between climate change and variations in caspian sea level csl we performed simulations of annual csl for the period 8 ka to 2100 ce using a coupled model setup representing climate hydrology and sea level we forced our climate model with long term changes in orbital parameters and atmospheric greenhouse gas concentrations using the ipcc a1b scenario for the 21st century our simulations produce an orbitally forced long term decline in csl of 5 m from 5 5 to 0 ka caused by a decrease in river runoff and over sea precipitation that is not fully compensated by a decrease in over sea evaporation superimposed on this long term downward csl trend we simulated centennial scale fluctuations of up to 4 m and decadal scale variations of up to 2 m caused by the internal variations of our modeled climate system amplified by the sensitivity of csl to small changes in river runoff and in the over sea p e budget the a1b anthropogenic emission scenario causes a 4 5 m fall in csl in the 21st century due to a pronounced increase in over sea evaporation that is stronger than the enhanced river discharge this decline in csl is of the same order of magnitude as the orbitally forced millennial scale downward csl trend simulated for the last 8000 years our results are generally consistent with csl estimates based on geological historical and measured data as well as with most other model studies 2007 elsevier b v all rights reserved

late little ice age palaeoenvironmental records from the anzali and amirkola lagoons south caspian sea vegetation and sea level changes abstract two internationally important ramsar lagoons on the south coast of the caspian sea cs have been studied by palynology on short sediment cores for palaeoenvironmental and palaeoclimatic investigations the sites lie within a small area of very high precipitation in a region that is otherwise dry vegetation surveys and geomorphological investigations have been used to provide a background to a multidisciplinary interpretation of the two sequences covering the last four centuries in the small lagoon of amirkola the dense alder forested wetland has been briefly disturbed by fire followed by the expansion of rice paddies from ad1720 to 1800 on the contrary the terrestrial vegetation reflecting the diversity of the hyrcanian vegetation around the lagoon of anzali remained fairly complacent over time the dinocyst and non pollen palynomorph assemblages revealing changes that have occurred in water salinity and water levels indicate a high stand during the late little ice age lia from ad

holocene oscillations of the caspian sea and forecasts based on palaeogeographical reconstructions abstract investigation of deltas and terraces adjacent to the caspian sea has indicated the pattern of holocene fluctuations in level since the initiation of the earliest holocene transgression the surface of the caspian sea has varied between 20 and 32 m below modern sea level six transgressive episodes are recognized in the holocene record separated by regressive episodes when the level fell below 28 m a s l the modal holocene level of the caspian sea is estimated at 28 2 m a s l beginning in 1929 water levels fell rapidly in the caspian sea reaching 29 m a s l the lowest value in 400 years in 1977 however the water level began to rise a trend which has continued to the present currently the caspian sea surface stands at approximately 27 m a s l throughout the past 2500 years the level has not exceeded 25 m a s l and it is not anticipated to exceed this value in the near future the fluctuations recorded since 1929 fall within the range of variations expected from natural environmental factors which have operated since the early holocene

landscape evolution and agro sylvo pastoral activities on the gorgan plain ne iran in the last 6000 years the gorgan plain ne iran is characterized by fertile soils formed on a loess plateau and is at present primarily exploited for intensive agriculture however the timing and intensity of the human impact on the landscape in the past are still unclear a sediment core taken from the centre of the eastern gorgan plain in the kongor lake covering the major part of the holocene from 6 1 to 0 8 ka all ages are calibrated before present has been studied for pollen non pollen palynomorphs botanical macroremains insects charcoal geochemistry biomarkers and magnetism in order to provide new insights into the evolution of the landscape and to estimate the intensity of human activities the data obtained suggest a dry period between 5 9 and 3 9 ka and an increase in regional humidity afterwards with a maximum between 2 7 and 0 7 ka during the period of the persian empires achaemenid through sasanian and the islamic era the eastern part of the gorgan plain was characterized by open steppe landscapes d

sea ice thickness in the coastal northeastern chukchi sea from moored ice profiling sonar time series ice draft data were obtained from moored ice profiling sonar ips in the coastal northeastern chukchi sea during 2009 10 time series data show seasonal growth of sea ice draft occasionally interrupted by coastal polynya the sea ice draft distribution indicates a slightly lower abundance of thick deformed ice compared with the eastern beaufort sea in january a rapid increase in the abundance of thick ice coincided with a period of minimal drift indicating compaction again the coast and dynamical thickening the overall mean draft and corresponding derived thickness are 1 27 and 1 38 m respectively the evolution of modal ice thickness observed can be explained mostly by thermodynamic growth the derived ice thicknesses are used to estimate heat losses based on era interim data heat losses from the raw 1 s ips data are 50 and 100 greater than those calculated using ips data averaged over spatial scales of 20 and 100 km respectively this finding demonstrates the importance of subgrid scale ice thickness distribution for heat loss calculation the heat loss estimate based on thin ice data derived from amsr e data corresponds well with that from the 1 s observed ice thickness data validating heat loss estimates from the amsr e thin ice thickness algorithm

river inflow and salinity changes in the caspian sea during the last 5500 years abstract pollen spores and dinoflagellate cysts have been analysed on three sediment cores 1 8 1 4 m long taken from the south and middle basins of the caspian sea a chronology available for one of the cores is based on calibrated radiocarbon dates ca 5 5 0 8 cal ka bp the pollen and spores assemblages indicate fluctuations between steppe and desert in addition there are some outstanding zones with a bias introduced by strong river inflow the dinocyst assemblages change between slightly brackish abundance of pyxidinopsis psilata and spiniferites cruciformis and more brackish dominance of impagidinium caspienense conditions during the second part of the holocene important flow modifications of the uzboy river and the volga river as well as salinity changes of the caspian sea causing sea level fluctuations have been reconstructed a major change is suggested at ca 4 cal ka bp with the end of a high level phase in the south basin amongst other hypotheses this could be caused by the end of a late and abundant flow of the uzboy river now defunct carrying to the caspian sea either meltwater from higher latitudes or water from the amu daria a similar later clear phase of water inflow has also been observed from 2 1 to 1 7 cal ka bp in the south basin and probably also in the north of the middle basin

numerical study of winter water formation in the chukchi sea roles and impacts of coastal polynyas winter water formation is examined in the chukchi sea for the winters of 1992 2006 using a primitive equation ocean model forced by ncep wind and surface salinity flux derived from ssm i thin ice thickness estimates the model is also forced by an external inflow of 0 8 sv through the bering strait the model successfully reproduces the oceanic circulation on the chukchi shelf thus providing numerous insights into behaviors of salt enriched water produced on the shelf the experiments show that under northeasterly winds northward throughflow across barrow canyon is reduced this results in salinity buildup under freezing conditions and ultimately in greater enhancement of salinity of the waters carried into the arctic basin the flow and salinity enhancement of the flow through herald canyon is less extreme but more steady than through barrow canyon together with moored salinity in the bering strait the model results estimate the actual salinity to be 32 9 0 8 psu and 32 7 0 3 psu respectively for waters moving through the barrow and herald canyons both estimates are less than 33 1 psu that is typically observed for the cold halostad layer in the canada basin suggesting the importance of diapycnal mixing with saltier atlantic origin water

circulation of the chukchi sea shelfbreak and slope from moored timeseries abstract data from a year long mooring array across the shelfbreak upper slope of the chukchi sea are used to describe and quantify the circulation and water masses of the region the timeseries revealed the year round existence of the eastward flowing shelfbreak jet and seaward of this the westward flowing chukchi slope current in the mean the slope current is estimated to transport 0 57 0 04 sv of pacific water while the bottom intensified shelfbreak jet transports 0 009 0 003 sv towards barrow canyon the slope current is surface intensified in summer and fall and in winter and spring it becomes middepth intensified moves shoreward and weakens two extreme states of the circulation were identified 1 an enhanced slope current and reversed westward flowing shelfbreak jet and 2 a strong eastward flowing shelfbreak jet and weak slope current the former state occurs when the wind stress curl on the chukchi shelf is positive and the latter state occurs when the curl is negative a simple theoretical model is used to determine the changes in sea surface height due to such wind stress curl forcing which is consistent with the observed changes in flow seaward of the shelf both in amplitude and phase via geostrophic set up shelfbreak upwelling occurred throughout the year but there was no correlation between the regional wind conditions and the upwelling furthermore there was no apparent relationship between upwelling and the extreme slope current shelfbreak jet events a comparison of water mass signals between the chukchi slope array and a mooring at the head of barrow canyon supports the notion that the slope current is fed by the outflow of pacific water from the canyon

dry late glacial and early holocene climate in arid central asia indicated by lithological and palynological evidence from bosten lake china abstract stratigraphical and chronological investigations of four sediment cores from bosten lake the largest inland freshwater lake in china provide a reliable regional environmental evolution record since the late glacial the stratigraphy of the four cores has been well correlated according to their lithology and chronology osl and 14c dates pollen and grain size data from bosten lake show evidence for a dry regional climate during late glacial and early holocene 16 8 cal ka bp indicated by a thick layer of aeolian sand deposit 100 cm although the climate became humid after 8 cal ka bp analysis of pollen assemblages pollen a c ratio and ephedra percentage also indicates that the climate was relatively dry in the bosten lake area between 8 and 6 cal ka bp while afterwards more humid conditions ca 6 1 5 cal ka bp are assumed comparison with other lake records from arid central asia influenced by the westerly winds generally supports the assumption of late glacial to early holocene dry climates in westerly dominated regions hence they contrast the holocene climate development in monsoon asia relatively wet conditions during the late holocene 6 1 5 cal ka bp might be induced by stronger westerly circulation

small scale stratigraphy in a large ramp delta recent and holocene sedimentation in the volga delta caspian sea the volga delta differs from all other major deltas in the world by its extremely gentle onshore and offshore gradient f5 cm km and by being affected by the rapid sea level changes of the caspian sea at rates up to a hundred times the global sealevel rise this paper reports 1 the morphological and facies development of part of the lower delta during the last full sealevel cycle between 1929 and 1995 as monitored using remote sensing and field mapping and 2 the holocene development of the delta from outcrop data and augered transects during a sea level fall of 3 m between 1929 and 1977 rapid progradation of levees composed of fine sand took place along over 800 distributary channels along the delta front smaller distributaries became filled with clay and organics during the 3 m sea level rise from 1977 to 1995 aggradation occurred leading to deposition of silt and clay on the levees and minor filling of the flood basins sedimentation rates as established with 137 cs dating are up to 2 5 cm year total thickness of holocene deposits in the lower delta plain is 4 10 m

sefidrud delta and quaternary evolution of the southern caspian lowland iran abstract the southern caspian sea lowland in iran forms a thick sedimentary prism produced by interactions of marine deltaic and fluvial processes during the late neogene and quaternary deltaic and fluvial deposits have been developed mainly by the sefidrud which is the largest river of the country its drainage area ca 61 600 km 2 includes nearly the entire alborz mountain range and forms deep valleys gorges and a large delta at the southern coast of the caspian sea the sefidrud delta is so large that it covers one third of the large guilan mazanderan plain both from an aerial and volumetric point of view consequently the drainage network of the sefidrud represents the quaternary evolution of northern iran and can be used to test the hypothesized evolution of the region the sefidrud delta has been investigated using many short and long cores satellite images and lithofacies maps and the results show that this delta complex 1680 km 3 consists of a covered lower part and exposed upper deltaic sequences the lower and upper parts of the complex were formed during the early pleistocene and late pleistocene respectively the upper exposed alluvial and deltaic sediments represent a total progradation of approximately 50 km forming three separate delta subsequences d1 3 of which the last one d3 is the modern sefidrud delta the modern delta is a wave dominated blanket like sediment cover ca 30 m thick and 1550 km 2 produced during the last three millennia it was formed by 30 km progradation of six juxtaposed lobes each lobe corresponds to a long term sea level fluctuation of the caspian sea the active lobe ca 50 km 2 has been forming since 1550 ad late pleistocene deltaic sequences d1 3 particularly the modern one d3 were produced by relatively fast deposition due to high volume sediment load of the sefidrud it is suggested that they were produced after the opening of the rudbar gorge by river capture that in turn six times enlarged the drainage area previous deltaic progradation and marine transgressions were relatively slow and the development of the whole lowland at the southern caspian sea lasted ca 1 1 2 ma bp

circulation and thermohaline variability of the hanna shoal region on the northeastern chukchi sea shelf we analyzed velocity and hydrographic data from 23 moorings in the northeast chukchi sea from 2011 to 2014 in most years the eastern side of hanna shoal was strongly stratified year round while weakly stratified regions prevailed on the shelf south and west of the shoal stratification differences cause differential vertical mixing rates which in conjunction with advection of different bottom water properties resulted in seasonally varying along isobath density gradients in agreement with numerical models we find that bottom waters flow anticyclonically around the shoal whereas most of the shelf responded barotropically to wind forcing there was a strong baroclinic component to the flow field northeast of hanna shoal resulting in no net vertically integrated transport on average in contrast there is a net eastward transport from west of the shoal which implies convergence north of the shoal convergence and along isobath density gradients may foster cross shelf exchange north of hanna shoal modal analyses indicate that the shelf south of the shoal and barrow canyon responded coherently to local and remote winds whereas the wind current response around hanna shoal was less coherent barotropic topographic waves of 3 day period were generated episodically northeast of the shoal and propagate clockwise around hanna shoal but are blocked from entering barrow canyon and are possibly scattered by the horizontally sheared flow and converging isobaths on the western side of the shoal analysis of water properties on the western side of hanna shoal suggests that these include contributions from the western and southern portions of the chukchi sea

solar forced 2600 bp and little ice age highstands of the caspian sea abstract the level of the caspian sea the largest inland sea in the world has fluctuated capriciously in history with amplitudes up to 3 m in the last century to 25 m in the last millennium and to over 150 m since the last glacial there is little consensus about the causes and forecasts are contradictory mainly due to a lack of solid data about past sea levels before 1837 ad when instrumental observation started we studied the holocene turali barrier complex along the western caspian shore in dagestan russia barrier dynamics during the last 3 m sea level cycle in the past century show that only lagoonal deposits overridden by highstand barriers are suitable for dating former highstands in the holocene barrier complex we selected the most suitable sites for dating using ground penetrating radar gpr profiles outcrops and gravel pits we obtained 14 accelerator mass spectrometry ams 14c data on in situ double valved molluscs from highstand lagoonal deposits the results suggest that the last major highstands occurred around 2600 bp and in the little ice age and coincide with global cooling events associated with minima in solar activity this suggests that millennial precipitation changes in the volga river drainage basin are also forced by solar activity

evidence for late holocene highstands in central guilan east mazanderan south caspian coast iran abstract the iranian caspian coast in the central guilan and east mazanderan were investigated using the analysis of samples retrieved from outcrops cores and through geophysical campaign the analysis of particle size organic matter calcium carbonate and fossil content as well as radiometric dating extends the caspian sea level records through the latest holocene ca 2500 years ground penetrating radar provides information about the internal stratigraphy of exposures along the central guilan coast lagoonal sediments that contained caspian mollusc shells have been dated at 2500 900 and 500 bp their dated horizons are located at altitudes of 22 24 and 25 m respectively which indicate higher sea levels during the late holocene the internal architecture and morphology of the coastal areas demonstrate spit lagoon development through littoral drift on the central guilan and east mazanderan coasts these structures also indicate lagoon formation due to rapid sea level rise a wide shallow lagoon in the central guilan sefidrud area was formed due to the last sea level rise 500 bp this lagoon then dried up as the result of falling sea level and infilled due to diversion of the sefidrud course these coastal developments show three highstands during the last 2500 years

a numerical model of earthquake induced piezomagnetic anomalies a numerical model for evaluating the order of magnitude of earthquake induced piezomagnetic anomalies is proposed the stress field associated with normal or reverse faulting with a 10 mpa mean stress drop is determined by mean of displacement discontinuity method the induced piezomagnetic tensor is then used to predict the associated magnetic field variations observed at ground surface the model shows that for earthquakes occurring in homogeneous magnetic masses with piezomagnetic properties of andesite rocks the associated anomalies are of the order of 0 2 nt for faults with a 5 km dip slip and 2 nt when the dip slip is 20 km long the variation of magnetic field for the case of a piezomagnetic dyke intruding a nonmagnetic body is found to be much greater for a 4 km thick dyke parallel to the fault and located 4 km from it the observed ground surface magnetic field variation is of the order of 10 nt these results outline that induced piezomagnetic effects strongly depend on the stress drop and stress distribution along and outside the fault the location of the earthquake source with respect to the piezomagnetic body and the piezomagnetic properties of the rock

development of the kura delta azerbaijan a record of holocene caspian sea level changes late holocene deposits of the kura delta indicate an alternating dominance of deltaic and shallow marine environments these major environment shifts are controlled by the high frequency sea level changes of the caspian sea the level of the caspian sea now at 27 m below global sea level gsl changes at rates of up to a hundred times as fast as global sea level allowing observation of sedimentary processes on a decadal scale that would take millennia in an oceanic environment the modern kura delta is a river dominated delta with some wave action along its north eastern flank and without tidal influence morphological and hydrological changes have been monitored for over 150 years continuing up to the present day using remote sensing imagery offshore sparker survey data onshore and offshore corings biostratigraphical analysis and radiometric dating enable a reconstruction of the holocene kura delta four phases of delta progradation alternating with erosional transgressive surfaces have been identified representing just as many cycles of sea level fall and rise the first cycle is represented by lowstand deposits truncated by a transgressive surface ts1 at ca 80 m below gsl ts1 is overlain by several metres of laminated clays and silts deposited during a late holocene forced regression h1 these deposits are truncated by the prominent reflector ts2 corresponding to the derbent lowstand around 1500 yr bp and subsequent transgression this transgressive surface is overlain by prograding shallowing upwards deposits h2 in turn truncated by a third transgressive surface ts3 correlated with a lowstand of ca 32 m below gsl the last phase h3 comprises an onshore progradational unit followed by an aggradational unit with an offshore veneer of clays and silts corresponding to the formation of the modern kura delta that started at the beginning of the 19th century

a full sea level cycle in 65 years barrier dynamics along caspian shores abstract the caspian sea being a closed basin shows much higher rates of sea level change up to 340 mm yr than the oceans it experienced a full sea level cycle with an amplitude of 3 m between 1929 and 1995 its coasts therefore present an attractive physical model to test predicted changes along oceanic coasts as a result of expected eustatic sea level rise and to validate sequence stratigraphical interpretations of ancient sediments along the wave dominated coasts with intermediate shore face slopes in dagestan low onshore bars were formed during the 1929 1977 sea level fall they represent minor short lived 1 2 years transgressive oscillations within the major regressional trend after the 1977 lowstand a prominent barrier lagoon system was formed which during the first phase of sea level rise 1977 1988 encroached landwards about 18 m each year by washover during storms continuous retreat between 1988 and 1995 however barrier size diminished lagoons widened and deepened apparently due to lack of coarse grained sediment supply discontinuous retreat the 1995 highstand prevented the barriers from being overstepped altogether sea level fall after 1995 again produced low bars without lagoons the caspian sea barrier coast demonstrates that for the formation of barrier lagoon complexes the combination of transgression and storms is essential barriers may show either continuous or discontinuous development at constant rate of sea level rise and constant offshore slope depending essentially on the availability of coarse grained sediments the rate of sea level rise as a factor in barrier behaviour cannot be viewed independently from barrier dimensions which in turn depend on wave base depth and maximum storm wave height relations between para sequence thickness and frequency and amplitude of sea level change in closed basins with an independent sea level regime may differ markedly from those in basins influenced by eustasy

late pleistocene and holocene sea level change and coastal paleoenvironment evolution along the iranian caspian shore the authors published by elsevier b v this is an open access article under the cc by nc nd license http creativecommons org licenses by nc nd 4 0

a wind driven hybrid latent and sensible heat coastal polynya off barrow alaska the nature of the barrow coastal polynya bcp which forms episodically off the alaska coast in winter is examined using mooring data atmospheric reanalysis data and satellite derived sea ice concentration and production data we focus on oceanographic conditions such as water mass distribution and ocean current structure beneath the bcp two moorings were deployed off barrow alaska in the northeastern chukchi sea from august 2009 to july 2010 for sea ice season from december to may a characteristic sequence of five events associated with the bcp has been identified 1 dominant northeasterly wind parallel to the barrow canyon with an offshore component off barrow 2 high sea ice production 3 upwelling of warm and saline atlantic water beneath the bcp 4 strong up canyon shear flow associated with displaced density surfaces due to the upwelling and 5 sudden suppression of ice growth a baroclinic current structure established after the upwelling caused enhanced vertical shear and corresponding vertical mixing the mixing event and open water formation occurred simultaneously once sea ice production had stopped thus mixing events accompanied by ocean heat flux from the upwelled warm water into the surface layer played an important role in formation maintenance of the open water area i e sensible heat polynya the transition from a latent to a sensible heat polynya is well reproduced by a high resolution pan arctic ice ocean model we propose that the bcp previously considered to be a latent heat polynya is a wind driven hybrid latent and sensible heat polynya with both features caused by the same northeasterly wind

modelling holocene stratigraphy and depocentre migration of the volga delta due to caspian sea level change the volga system is sensitive to allogenic control due to its low on and offshore gradient similar to 5 cm km in sequence stratigraphy little attention has been paid to the effects of sea level change in these ramp margin fluvio deltaic settings the high frequency sea level changes of the caspian basin have considerable amplitude up to 18 m over the holocene time span which is usually considered as the lower boundary of fifth order cycles a process response model aquatellus has been used to investigate fluvio deltaic response to sea level fluctuation calibration of the model with measured data over the last century comprising a full 3 m sea level cycle showed plausible progradation and sedimentation rates the numerical modelling showed that sea level changes forced the holocene volga delta to migrate similar to 200 km over the caspian plain leaving only thin laterally extensive deposits the frequent depocentre shifts add a whole new perspective to the ongoing discussion about the impact of sea level changes along the longitudinal profile the periods during which significant deposition occurred coincide with the times that migration distances were relatively low thicker progradational wedges have been deposited at these time intervals at similar to 9000 8000 similar to 7400 6700 similar to 5200 3700 and similar to 2400 900 years bp c 14 dated deposits in the lower delta plain area corroborate the model output remarkably this is both in highstand and lowstand conditions the low gradient makes wave effects insignificant and tides are nonexistent so that the fluvial deposits are hardly reworked and no shoreface facies or maximum flooding surface develop the volga delta response indicates that sequence stratigraphic concepts are not scale independent in low gradient settings and that short term high frequency sea level changes have a far reaching impact on the stratigraphy c 2002 elsevier science b v all rights reserved

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

vertical structure and temporal variability of currents over the chukchi sea continental slope abstract observations from a single mooring site on the northern chukchi sea continental slope near the 1000 m isobath are presented this site was occupied consecutively for three years spanning september 2014 august 2017 vertically the flow divides into three depth ranges the upper 200 m 200 850 m and near bottom flow in the upper 200 m the mean flow was northwestward and strongest in the summer months during winter months currents decreased in magnitude and in some years even reversed in direction satellite tracked drifter trajectories drogue depth 30 m show this along slope flow persists at least from 156 to 165 w with an average velocity of 17 cm s 1 this northwestward flowing current is the chukchi slope current from 250 m to 850 m the flow reversed this weak flow is the arctic wide cyclonic boundary current advecting atlantic water the mean flow at 900 m is weak and on an annual time scale not significantly different from 0 cm s 1 it consists of arctic deep water in the upper two layers currents vary on the scale of days to seasons with short term reversals common currents below 40 m were not significantly correlated with local winds nor wind stress curl we hypothesize that the northwestward flowing chukchi slope current is a consequence of dynamics associated with the beaufort gyre

nutrient supply and biological response to wind induced mixing inertial motion internal waves and currents in the northern chukchi sea a fixed point observation station was set up in the northern chukchi sea during autumn 2013 and for about 2 weeks conductivity temperature depth ctd water samplings 6 h and microstructure turbulence measurements 2 to 3 times a day were performed this enabled us to estimate vertical nutrient fluxes and the impact of different types of turbulent mixing on biological activity there have been no such fixed point observations in this region where incoming low salinity water from the pacific ocean river water and sea ice meltwater promote a strong pycnocline halocline that stabilizes the water column previous studies have suggested that because of the strong pycnocline wind induced ocean mixing could not change the stratification to impact biological activity however the present study indicates that a combined effect of an uplifted pycnocline accompanied by wind induced inertial motion and turbulent mixing caused by intense gale force winds 10 m s 1 did result in increases in upward nutrient fluxes primary productivity and phytoplankton biomass particularly large phytoplankton such as diatoms convective mixing associated with internal waves around the pycnocline also increased the upward nutrient fluxes and might have an impact on biological activity there for diatom production at the fixed point observation station it was essential that silicate was supplied from a subsurface silicate maximum a new feature that we identified during autumn in the northern chukchi sea water mass distributions obtained from wide area observations suggest that the subsurface silicate maximum water was possibly derived from the ventilated halocline in the canada basin

effects of variability of sea ice transport through the fram strait on the intensity of the atlantic deep circulation results from an ice ocean coupled model are used to investigate the impact of long term variability in sea ice transport at the fram strait on the intensity of the atlantic deep circulation an increase or decrease in sea ice transport through the fram strait leads to a stronger or weaker deep circulation in the atlantic change in the sea ice transport is accompanied by a salinity anomaly in the surface layer of the arctic ocean such an anomaly could inversely affect the atlantic circulation once it reaches deep water formation regions if the canadian archipelago is closed the anomaly is subsequently transported through the fram strait and counters the initial changes in the atlantic deep circulation on the other hand if the canadian archipelago is open some of the anomaly is transported to the canadian archipelago and the initial change in the atlantic deep circulation persists in the arctic ocean basin the time scale and path of the salinity anomalys propagation depends on the large scale flow at the surface of the arctic ocean our results suggest that the salinity anomaly transport and its propagation pathway out of the arctic ocean are important determinants of the role of sea ice transport variability through the fram strait in controlling the intensity of the atlantic deep circulation

winter water formation in coastal polynyas of the eastern chukchi shelf pacific and atlantic influences water properties and formation processes of alaskan coastal winter water acww over the eastern chukchi shelf along the alaska coast the so called barrow canyon pathway are examined using data from moorings atmospheric reanalysis satellite derived sea ice production sip and a numerical tracer experiment along this pathway pacific winter water pww can be modified to produce acww through sip accompanied by production of cold saline polynya water in the coastal polynyas upwelling of warm atlantic water aw and mixing processes on the shelf three different types of acww are formed i a mixture of aw and pww ii a mixture of aw and polynya water and iii hypersaline polynya water the northeasterly winds correlated with the north south atmospheric pressure gradient between beaufort high and aleutian low are common triggers of polynya sip episodes and aw upwelling in the barrow coastal polynya bcp due to the dual impact of northeasterly winds pww modification processes in the bcp are more complicated than what occurs elsewhere in the chukchi polynya the impact of aw upwelling on the acww formation is most prominent in the bcp usually centered along the coast all types of acww are thought to be basically transported westward or northwestward with the chukchi slope current and or beaufort gyre and finally contribute to maintenance of the lower halocline layer especially over the chukchi borderland northwind ridge and southern canada basin even in the pacific sector of the arctic ocean acww properties are strongly influenced by both atlantic origin and pacific origin waters

late cenozoic base level variations of the caspian sea a review of its history and proposed driving mechanisms abstract the caspian sea is characterized by significant variations in its base level during the late cenozoic and provides an important repository for long term records of both regional climate and tectonics due to its position within the interior of the eurasian continent and at the northern margin of the ongoing arabia eurasia collision zone the caspian also serves as an important moisture source for eastern eurasia including the northern tibetan plateau and thus the history of caspian base level variations represents an important and poorly understood constraint on paleoclimate reconstructions throughout eurasia prior work in the caspian region has largely focused on developing biostratigraphic age divisions and investigating the history of connection between the caspian black and mediterranean seas as well as the global ocean recent geochronologic work in the caspian and related basins has questioned previous correlations of hydrologic events in these different basins as a result prior estimates of the chronology and magnitude of caspian sea level variations may be incorrect here we synthesize previous work to develop a new caspian base level curve starting at the beginning of the meotian regional stage 7 ma we also present a new synthesis of potential driving mechanisms for the large variations in caspian base level and speculate on a possible cause for the enigmatic akchagyl transgression this synthesis highlights the dynamic range of caspian sea level which varied from 200 m above to in excess of 1000 m below its current level during the late cenozoic and provides a basis for future work investigating the tectonic and climatic drivers behind variations in caspian base level

the encoding of wind forcing into the pacific arctic pressure head chukchi sea ice retreat and late summer barrow canyon water masses abstract barrow canyon which incises the northeast corner of the chukchi sea shelf is a major conduit through which pacific origin waters carrying nutrients biota freshwater and heat enter the arctic ocean as such barrow canyon was adopted as a long term monitoring site for the distributed biological observatory dbo in 2010 however annual hydrographic surveys across barrow canyon conducted during late august 2005 2015 along a location near what is the barrow canyon dbo survey line and in support of other research programs extend and complement the dbo hydrographic record these complementary hydrographic surveys show that volumes of pacific origin and melt water masses in barrow canyon are significantly correlated with daily sea ice areas in the eastern chukchi sea for most of the may august ice retreat season year to year differences in the timing and pattern of sea ice retreat across the chukchi sea are also shown to be well correlated with changes in seasonally averaged regional winds particularly as defined by the strength and longitudinal location of the beaufort sea high pressure cell these interdependent wind ice retreat water mass relationships are largely predicated on wind stress curl driven changes to sea level in the east siberian sea northwestern chukchi sea statistically significant correlations among wind forced sea surface heights ice areas and water mass volumes suggest that during the ice retreat season the east siberian sea western chukchi sea region serves as the arctic terminus for the pacific arctic pressure head

the chukchi slope current abstract using a collection of 46 shipboard hydrographic velocity transects occupied across the shelfbreak and slope of the chukchi sea between 2002 and 2014 we have quantified the existence of a current transporting pacific origin water westward over the upper continental slope it has been named the chukchi slope current which is believed to emanate from barrow canyon the current is surface intensified order 50 km wide and advects both summer and winter waters it is not trapped to a particular isobath but instead is reminiscent of a free jet there is no significant variation in pacific water transport with distance from barrow canyon a potential vorticity analysis suggests that the flow is baroclinically unstable consistent with the notion that it meanders the current is present during all synoptic wind conditions but increases in strength from summer to fall presumably due to the seasonal enhancement of the easterly winds in the region its transport increased over the 12 year period of data coverage also likely in response to wind forcing in the mean the slope current transports 0 50 0 07 sv of pacific water this estimate allows us to construct a balanced mass budget of the chukchi shelf inflows and outflows our study also confirms the existence of an eastward flowing chukchi shelfbreak jet transporting 0 10 0 03 sv of pacific water towards barrow canyon

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

seasonal to mesoscale variability of water masses and atmospheric conditions in barrow canyon chukchi sea abstract twenty four repeat hydrographic transects occupied across barrow canyon from 2010 to 2013 are used to study the seasonal evolution of water masses in the canyon from july october as well as the occurrence of upwelling the mean sections revealed that the alaskan coastal water is mainly confined to the eastern flank of the canyon corresponding to a region of sloped isopycnals indicative of the surface intensified alaskan coastal current which advects the water the pacific origin winter water is found at depth banked against the western flank of the canyon its isopycnal structure is consistent with a bottom intensified flow of this dense water mass out of the canyon for the months that were sampled the alaskan coastal water is most prevalent in august and september while the coldest winter water is observed in the month of august it is argued that this newly ventilated winter water is delivered to the canyon via pathways on the central chukchi shelf as opposed to the coastal pathway roughly a third of the hydrographic sections were preceded by significant up canyon winds and hence were deemed to be under the influence of upwelling during these periods anomalously salty water is found throughout the eastern flank of the canyon and on occasion atlantic water fills the deepest part of the section using atmospheric reanalysis data it is shown that upwelling occurs when the beaufort high is strengthened and the aleutian low is deepened two modes of storm tracks were identified northward progressing storms mode 1 and eastward progressing storms mode 2 both of which can drive upwelling mode 1 is prevalent in july august while mode 2 is more common in september october these seasonal patterns appear to be dictated by regional variations in blocking highs

fluvial chronology in the east european plain over the last 20 ka and its palaeohydrological implications abstract a database containing 983 absolute ages of fluvial deposits was interpreted in palaeohydrological terms and 646 dates were found associated with 754 local palaeofluvial events geomorphic or sedimentological traces of changing fluvial activity combined probability density functions of high and low activity dates were used to detect time intervals of different palaeohydrological status after low fluvial activity during lgm two palaeohydrological epochs were designated extremely high activity in the end of mis 2 ca 18 11 7 ka before ce 2000 b2k and much lower activity in the holocene within the holocene two hierarchical levels of hydroclimatic variability were designated according to their duration and magnitude regional palaeohydrological phases centuries to few millennia and regional palaeofluvial episodes decades to few centuries tendency is rather clear of activity lowering in the first half and rise in the second half of the holocene extremes within the palaeohydrological phases were designated as 19 palaeofluvial episodes 7 high activity ha episodes 8 low activity stability la episodes and 4 contrast or complex ca episodes in most cases changes of fluvial activity were most likely induced by changing amounts of spring snowmelt runoff most distinct correlation of temperature and hydrological regimes was found in the late holocene high fluvial activity corresponded to cold climatic phases little ice age low activity to warm phases medieval climatic optimum current climate warming the suggested fluvial chronology was compared with independent hydroclimatic archives such as palaeosoils and lake levels correlation with soil formation alluviation epochs was found very close with some exceptions in the early holocene correspondence of fluvial activity to the caspian sea level changes is rather high in the second part of the holocene and is poor before 4 5 ka b2k which can be explained by insufficient data behind both types of reconstructions correlation of changes in fluvial activity within a west east transect over europe revealed relatively poor correlation in the early and mid holocene and much higher synchronism since 3 0 ka b2k which may indicate increasing role of westerlies in controlling european climates in the late holocene throughout the whole holocene changes of fluvial activity over eep were governed by natural climate forcing until the last few centuries when land use changes induced accelerated hillslope and gully erosion

surface current patterns in the northeastern chukchi sea and their response to wind forcing we measured northeastern chukchi sea surface currents using high frequency radar systems hfr during the ice free periods of august to october from 2010 2014 we analyzed these data along with regional winds using self organizing maps som to develop a set of surface current wind patterns temporal changes in the som patterns consist predominantly of two patterns comprising northeastward and southwestward surface currents a third pattern represents a transitional stage established during the onset of strong northeasterly winds these patterns are analogous to the first two eigenmodes of an empirical orthogonal function analysis of the hfr data the first principal component pc1 is significantly correlated 0 8 to that of the winds and is directly related to the time series of som derived patterns the sign of pc1 changes when the speed of local northeasterly winds exceeds 6 m s 1 at which point the northeastward surface currents reverse to the southwest this finding agrees with previous models and observations that suggest this wind threshold is needed to overcome the pressure gradient between the pacific and arctic oceans the transitional stage is characterized by alongshore currents bifurcating in the vicinity of icy cape and wind driven ekman currents north of 71 5 n its development is a manifestation of interactions amongst the poleward pressure gradient wind stress and geostrophic flow due to the coastal setdown

from the allerod to the mid holocene palynological evidence from the south basin of the caspian sea pollen and dinoflagellate cysts have been analysed in a core from the south basin of the caspian sea providing a picture of respectively past vegetation and water salinity for the late pleistocene to middle holocene a relatively sharp lithological change at 0 86 m depth reflects a shift from detrital silts to carbonates rich fine silts from this depth upwards a holocene chronology is built based on ten radiocarbon dates on ostracod shells and bulk carbonates from the vegetation point of view the late pleistocene deserts and steppes were partially replaced in the most sheltered areas by an open woodland with pinus juniperus hippophae elaeagnus and even alnus quercus pterocarya and fraxinus related to the allerod palynozone this was interrupted by the younger dryas palynozone when artemisia reaches a maximum in a first instance followed by a very dry phase with only a slight return of pinus and quercus and the rare presence of ulmus zelkova from 11 5 to 8 4 cal ka bp an open landscape dominated by shrubs such as ephedra and progressively increasing quercus appeared the final spread of diverse evergreen and deciduous trees is delayed and occurs after 8 4 cal ka bp it is suggested that this delay is caused by an arid climate in the early holocene linked to high insolation and perhaps to a lake effect the dinocyst assemblages fluctuate between slightly brackish pyxidinopsis psilata and spiniferites cruciformis 7 psu and lower and more brackish impagidinium caspienense w13 psu in the lateglacial khvalynian highstand the assemblages remained dominated by relative low salinity taxa a late and brief increase of salinity occurred prior to 11 2 cal ka bp associated with the mangyshlak lowstand it is suggested that it was caused by a brief drop in meltwater flow from both the north and the southeast uzboy and a likely evaporation increase this lowstand occurs quasi at the same time as the end of a longer lowstand in the black sea the freshest waters are then inferred as having occurred between 8 4 and 4 4 cal ka bp linked to a connection with the amu darya and the melting glaciers on the pamir mountains

lithofacies and ichnofacies distribution in offshore sediments of the langarud rudsar region of iran southern caspian sea innovative computerized co axial tomography cat scan methods have been applied to two short cores collected in the southern caspian sea offshore from the langarud rudsar region of iran to the east of the sefidrud delta magnetic susceptibility ms readings in association with other lithological criteria are used to correlate the cores and calibrate to real time the cores provide a sedimentary record from this largely unstudied region covering the last 200 years 1784 to 2008 ce three principal lithofacies types were recognized the more distal locality t2 3 water depth 117 m consists entirely of poorly fossiliferous silty muds whereas the more proximal locality t2 2 water depth 51 m contains beds with rich ostracod gastropod and bivalve assemblages peak ms readings occur between 1872 and 1918 ce and are linked to erosion of sediments deposited during the little ice age lia highstands of the caspian sea cat scan results reveal the presence of the non marine mermia ichnofacies type which is reported for the first time in the caspian sea horizontal burrows feeding structures by treptichnus ichnofauna coincide with periods of lia highstand in caspian sea level and suggest low energy conditions on the marine shelf vertical burrows feeding structures occur at times of relatively stable but variable caspian water levels interbedded dark coloured organic rich muds and lighter silt rich layers within the last 100 years show potential cyclicity which may be linked to climatic and or river discharge events

freshwater budget of the canada basin arctic ocean from salinity δ18o and nutrients 1 the contribution of freshwater components e g meteoric sea ice and pacific water in the canada basin is quantified using salinity 18o and nutrient data collected in 2003 and 2004 the penetration depth of sea ice meltwater is limited to the upper 30 m and brine rejected during sea ice formation is observed from 30 to 250 m depth the fraction of meteoric water is high in the upper 50 m and decreases with depth pacific water entering via bering strait is the main source of freshwater below 50 m depth bering strait throughflow which transports pacific water with salinity 32 5 together with meteoric water supplied upstream of the bering strait contributes up to 75 of freshwater input 3200 km3 a 1 to the canada basin the mean residence time of pacific water in the canada basin is estimated to be 11 years precipitation and river runoff from both north american and eurasian continents add 800 km3 a 1 and sea ice formation removes 900 km3 a 1 0 6 m a 1 of fresh water the export of ice and liquid fresh water from the canada basin contributes 40 of the freshwater flux from the arctic ocean to the north atlantic ocean

wintertime variability of the beaufort gyre in the arctic ocean derived from cryosat 2 siral observations we processed the sea surface height measured by the sar synthetic aperture radar interferometric radar altimeter siral on board cryosat 2 cs 2 and successfully estimated the monthly dynamic ocean topography dot of the arctic ocean the cs 2 monthly dot showed the interannual and monthly variability of the beaufort gyre bg during winter between 2010 2011 and 2014 2015 the northward flow at the western edge of the bg was primarily estimated over the chukchi borderland cbl however the bg extended across the cbl and the northward flow was estimated over the mendeleev ridge in the winter of 2012 2013 our analyses revealed a significantly variable bg in response to changes in the sea surface stress field our analysis indicated that 1 sea ice motion driven by wind fields acts as a driving force for the bg when sea ice motion was intensified during winter and 2 sea ice motion can also act as an inhibiting force for the bg when sea ice motion is weakened during winter in addition the relationship between the dot steric height and ocean bottom pressure implied that the dot during winter responded to varying wind stresses through baroclinic and barotropic adjustments according to a tracer experiment we inferred that in the winter of 2012 2013 the pacific origin water carried into the bg through the barrow canyon was transported to the northern shelf and shelf break of the chukchi sea rather than the cbl which is where the pacific origin water had been transported in the other years of the observation period

barrow canyon volume heat and freshwater fluxes revealed by long term mooring observations between 2000 and 2008 1 barrow canyon in the northeast chukchi sea is a major conduit for pacific water to enter the interior arctic basins assemblies of annual september 2000 to august 2008 temperature salinity and velocity data acquired from a mooring array in the mouth of barrow canyon and high resolution hydrographic and velocity transects along the mooring array in 2002 2010 and 2011 have enabled a direct computation of volume heat and freshwater fluxes annual mean volume transport through barrow canyon was 0 45 sv which consisted of 0 44 sv of pacific water and 0 01 sv of atlantic water annual mean pacific water transport through barrow canyon represents 55 of the long term mean pacific water inflow through the bering strait during summer more of the pacific inflow was advected to an eastern path as the alaskan coastal current that flows along the alaskan coast to barrow canyon the freshwater flux through barrow canyon was 904 km3 yr which is equivalent to 5 of the freshwater content of the canada basin the annual averaged heat flux displayed substantial interannual variability ranging from 0 93 to 3 02 tw which could melt 88 000 290 000 km2 of 1 m thick ice a relationship exists between the measured barrow canyon transport and local winds such that under southerly winds the northward flow of water through the canyon increases such wind conditions are induced by the weaker sea level pressure contrast between the arctic and north pacific caused by a decrease in the pressure over the arctic and an increase over the north pacific

piezomagnetic fields of screw dislocation fault models an analytical solution is obtained for the piezomagnetic field generated by a single screw dislocation and its image representing an infinitely long vertical fault with uniform strike slip that cuts the upper or lower portion of a half space the solution is readily extendable to other models of strike slip faults based on vertical arrays of screw dislocations for reasonable values of the relevant physical constants the field is predicted to be generally below current levels of detectability this result is a consequence of the symmetry of piezomagnetization around a screw dislocation which inhibits regions of intense piezomagnetism near the dislocation from contributing to the external field

wind driven modification of the alaskan coastal current 1 across shelf transects over the eastern flank of barrow canyon were obtained in august 2005 with an autonomous underwater vehicle auv here the shelf topography creates a choke point in which a substantial portion of pacific inflow from the bering strait is concentrated within 30 km of the coast providing an ideal setup for monitoring the flow with the auv four transects extending 10 km offshore of barrow alaska inshore of the 80 m isobath were used in conjunction with a process oriented numerical model to diagnose the wind driven modification of the alaskan coastal current poleward transports of 0 12 sv were consistent among all sections although the transport weighted temperature was about 1 c colder in the transect obtained during peak winds an idealized numerical model reproduces the observed hydrographic structure and across shelf circulation reasonably well in that 1 winds were not sufficient to reverse the poleward flow 2 upwelling was most pronounced in the nearshore and 3 the onshore return flow occurred throughout the interior as opposed to the bottom boundary layer the across shelf circulation provides a possible mechanism for a meltwater intrusion observed on the offshore side of the auv transect made during peak winds also of interest is that the observed anticyclonic shear was much stronger u y f than previously measured in the region

geomorphic response and 14c chronology of base level changes induced by late quaternary caspian sea mobility middle kura valley azerbaijan abstract recent geomorphological studies in azerbaijan reveal the importance of climato eustatic influences on landscape changes in the caspian sea basin during the last 40 ka radiocarbon dated fluvial landforms show that the paleohydrosystem of the middle kura valley and tributaries responded to regressive and transgressive phases of the caspian sea chrono sequences and landforms secured by 32 radiocarbon ages show strong correspondence between fluvial sediment accumulation and oscillations of base level in the caspian sea six phases of valley floor aggradation e g 27 000 13 000 11 000 3200 2900 2100 1600 1000 400 150 cal yr bp and seven phases of fluvial incision 37 000 37 000 27 000 13 000 11 000 3200 2900 2100 1600 1000 400 150 0 cal yr bp are recorded morphodynamics of the fluvial landscape show a strong correspondence with fluctuation in sea levels in the caspian sea the major upper pleistocene late glacial khvalynian c a 26 000 to 12 400 cal yr bp and various holocene transgressions as well as the mangyshlak c a 12 000 cal yr bp and derbent 6th 12th century ad regressions these data contribute to refining the caspian relative sea level curve for the last 30 ka using the chronology of changes in the aggradation or incision in the connected fluvial system

late pleistocene and holocene palaeoenvironments in and around the middle caspian basin as reconstructed from a deep sea core this article has been made available through open access by the brunel open access publishing fund

dinocyst records from deep cores reveal a reversed salinity gradient in the caspian sea at 8 5 4 0 cal ka bp abstract understanding the long term environmental forcings driving caspian sea cs water levels is of utmost importance not only owing to its large size or to the surrounding developing economies but also to improve global climate models and forecasts however late quaternary cs level changes and their amplitude are mostly documented from incomplete coastal sediment records because of the cs idiosyncrasies that behaves neither as a sea nor as a lake the methods used to reconstruct water levels in the global ocean or in freshwater lakes do not always apply here we propose a first step toward the use of dinoflagellate cysts records to reconstruct qualitative changes in water mass focusing on new and published deep water sedimentary sequences from the south and middle cs basins trends in water level changes are reconstructed on the relative proportions of dinocyst assemblages with different levels of brackishness a higher highstand than previously seen is reconstructed post mangyshlak lowstand a reverse water flow gradient from s to n not previously detected is identified at 8 5 8 to 4 cal ka bp a major turnover in dinocyst assemblage is found at 4 cal ka bp while the volga river is the main source of water nowadays we propose that the source of water to maintain the 8 5 8 to 4 cal ka bp highstand is the now disconnected drainage basin of the amu darya the cs was at that time most likely strongly influenced by low latitude climates with more precipitation over the karakum and perhaps even indirect monsoonal influence

circulation of summer pacific halocline water in the arctic ocean 1 we present an analysis of arctic ocean hydrographic and sea ice observations from the 1990s with a focus on the circulation of water that originates in the north pacific ocean previous studies have shown the presence of two varieties of relatively warm summer halocline water in the vicinity of the chukchi sea i e the relatively fresh alaskan coastal water acw and the relatively saltier summer bering sea water sbsw here we extend these studies by tracing the circulation of these waters downstream into the arctic ocean we find that acw is generally most evident in the southern beaufort gyre while sbsw is strongest in the northern portion of the beaufort gyre and along the transpolar drift stream we find that this separation is most extreme during the early mid 1990s when the arctic oscillation was at historically high index values this leads us to speculate that the outflow to the north atlantic ocean through the canadian archipelago and fram strait may be similarly separated as arctic oscillation index values fell during the later 1990s acw and sbsw began to overlap in their regions of influence these changes are evident in the area north of ellesmere island where the influence of sbsw is highly correlated with a 3 year lag with the arctic oscillation index we also note the presence of winter bering sea water wbsw which underlies the summer varieties all together this brings the number of distinct pacific water types in our arctic ocean inventory to three acw sbsw and wbsw

modern and holocene sublittoral ostracod assemblages crustacea from the caspian sea a unique brackish deep water environment abstract we present a reconnaissance study of sublittoral ostracods from a number of caspian sea core tops collected during a joint french russian scientific cruise in 1994 cores from between 13 and 875 m water depth the modern ostracods show little depth restriction and this reflects the hydrography of the caspian sea which maintains relatively constant conditions 5 c 13 salinity below 50 m throughout the year we also present the ostracod faunal record from a 10 m core of laminated sediments recovered from the central caspian basin at a water depth of 475 m which we believe shows repetitive quasi cyclic changes in bottom water conditions over approximately the last 14 15 000 years with a major change at about the late glacial to holocene transition the faunal record from this core illustrates the potential of these sediments for reconstructing environmental changes in the caspian region during the late quaternary to holocene the continuous occurrence of in situ benthic meiofauna throughout the core also indicates that the bottom water must have remained ventilated throughout this period although variability in the faunal assemblages may reflect long and short term changes in the strength of ventilation

current status and palaeostages of the caspian sea as a potential evaluation tool for climate model simulations decadal scale oscillations of the level of the caspian sea cs primarily stem from variations in runoff from the volga river therefore although the image of the cs within the climate models is very simplified changes in the level of the cs can be used to assess the ability of climate models to reproduce the water budget over the east european plain the proxy dataset comprises a number of detailed maps of the cs for the main regression stages and transgression stages during the last 30 ka together with information about sea level positions we compare observed or reconstructed cs level positions during the last millennium and modern periods with the cs level positions calculated based on simulations in experiments using the cmip5 pmip3 protocol the modelled data could be verified based on how well the models simulate a the observed decadal scale cs level dynamics during the twentieth century and b the derbentian regression transition to new caspian 5th phase highstand and slight lowering of the cs level at the end of the nineteenth century

rapid holocene sea level changes along the iranian caspian coast abstract the caspian sea is well known for its rapid sea level change during 1929 1995 a full sea level cycle was observed first the sea level dropped 3 m with a lowstand in 1977 followed by a 3 m rise to 1995 after which the sea level has been relatively stable these oscillations are a specific feature of the caspian sea and its sedimentary record the main purpose of this study is to reconstruct the sea level curve in the holocene by using sedimentological and biostratigraphic analysis and radiocarbon dating along the iranian part of the caspian shore remote sensing images and historical maps show that two lagoons totally emerged and the gorgan delta prograded rapidly at a rate of around 160 m y 1 until the 1975 lowstand gorgan bay was reduced in size considerably and the connection to the sea was blocked due to growth of a spit and change in base level when sea level started to rise again the coastal morphology rapidly changed and the gorgan delta retrograded at the rate of around 140 m y 1 these sedimentary dynamics can be recognized in the preserved deposits in addition to the recent dynamics core data from the southeastern lowlands show four earlier highstands using characteristic barrier lagoon deposits early holocene sea level rose until a highstand was reached of ca 34 m this phase was followed by fluvial deposition in the gorgan delta associated with a base level fall there is also an evidence of sea level rise between 5000 and 2300 bp at ca 27 7 m on top of these deposits there is evidence of a highstand between 2700 and 2300 bp at ca 23 5 m the fourth highstand from the core data is dated to the little ice age at ca 24 m data from these last two highstands correspond well with other observations from the caspian region

synoptic flow and density observations near an arctic shelf break analyses of data from three shipborne surveys describe the quasi synoptic density and velocity fields near barrow canyon alaska the canyon parallels the northwestern coast of alaska and contains three different water masses these are 1 warm and fresh alaskan coastal waters that originate from the bering strait 2 cold and moderately salty waters that originate from the chukchi shelf and 3 warm and salty waters that originate from the atlantic layer of the arctic ocean a halocline separates the chukchi shelf and atlantic layer waters the halocline slopes upward into the canyon where it is then twisted to slope across the wide canyon an intensification of the beaufort gyre near the shelf break just seaward of barrow canyon raises the halocline more than 100 m toward the surface locally upwelling favorable winds raise the arctic halocline which thus is ventilated within barrow canyon adjacent to the coast in the absence of winds the halocline slopes acrosscanyon in the thermal wind sense due to a northward flowing coastal current velocity measurements from a towed acoustic doppler current profiler reveal a northward flowing jet that transports about 0 3 sv sv 106 kg m23 of bering sea summer water into the arctic ocean at speeds that exceed 0 7 m s21 total northward transports through the canyon exceed 1 0 sv the warm waters of this coastal current supply more than 100 w m22 of heat to the atmosphere the jet separates both from the bottom and from the coast hence a laterally and vertically sheared jet forms which breaks into three branches at about 71 88n latitude

circulation dense water formation and outflow on the northeast chukchi shelf we investigated circulation and water mass modification processes in the chukchi sea using 1 temperature salinity and velocity data collected between september 1991 and september 1992 from moorings in bering strait and the northeast shelf and 2 meteorological data and ice concentrations derived from special sensor microwave imager ssm i imagery in october 1991 and from february to august 1992 the mean monthly circulation was steady and northward from november to january strong northeast winds diverted the low salinity bering inflow onto the western shelf and weakened and reversed flow over the northeast shelf the winds also opened extensive polynyas wherein cold hypersaline salinity 34 waters formed the fall winter circulation enhanced dense water formation by diverting low salinity waters away from and prolonging the residence time of water within the polynyas alongshore convergence of the coastal flow swept some of the cold hypersaline water offshore across isobaths but the coastal current carried most of it into the arctic ocean through barrow canyon the dense outflow mixed little during its descent through the upper canyon where bottom friction and rotation but not entrainment were important in the plume momentum balance if the outflow is not diluted by mixing in the lower canyon where theory suggests this will occur then the densest shelf waters can ventilate layers deeper than the halocline salt rejection estimates using ssm i data and surface heat budget calculations agree within a factor of 2 with independent estimates from the mooring hence remote sensing techniques can monitor winter salt rejection rates in the chukchi sea

development of spit lagoon complexes in response to little ice age rapid sea level changes in the central guilan coast south caspian sea iran the central guilan coast along the iranian caspian coastline is characterized by sandy beaches and the development of spit lagoon complexes which are prone to preserve past sea level fluctuations the morphology of three spit lagoon complexes along the central guilan coast was studied using ground penetrating radar gpr and sediment sequences to understand the effects of past sea level changes on spit lagoon development the results showed the prominent role of coastal setting in conditioning the development of spit lagoon formation in response to sea level change when the caspian sea experienced a highstand in the little ice age the coast of central guilan recorded fluctuations in sedimentation which are reflected for example by river avulsion and beach ridge formation depending on physical setting in the western half of the central guilan eastward longshore currents and strong wave action on a w e coastline coupled with sea level changes shaped the anzali spit lagoon complex while in the eastern part of the studied area river avulsion and changing the coastline orientation are responsible for development of the amirkola and kiashahr spit lagoon complexes under the same sea level fluctuations although sea level change has a major role in spit lagoon development an increase in the frequency of storms changes in sediment supply due to more precipitation and river avulsion are other players in spit lagoon development in the central guilan during the little ice age and more recent times

base level changes river avulsions and holocene human settlement dynamics in the caspian sea area middle kura valley south caucasus abstract geomorphological geochronological and geoarchaeological analysis focusing on six tributaries of the kura river provide valuable data concerning sedimentation rhythmicity and holocene human settlement distribution at a regional scale seven new radiocarbon dates from the upstream part of these hydrosystems complemented the existing radiocarbon dataset n 32 obtained downstream these data seem to indicate that upstream hydrosystems also reacted to marine regressions by powerful riverbed incisions and to transgression phases by thick valley infillings from at least as early as the upper pleistocene the retroactive morphogenic effects were also perceived in intra mountainous areas far from the caspian shoreline the land use patterns of the caucasian societies dwelling in the valley of the kura hydrosystem were affected by temporary river avulsions resulting in silty fans over the high terraces during the neolithic chalcolithic periods these river avulsions seem to be governed by local climate and base level changes linked to fluctuations of the caspian sea level over time this is spatially and diachronically evidenced in settlement distribution with almost exclusive localization on perched silty fans and river runoff from the key period of neolithic development in the region these new data must be considered in future geoarchaeological analyses concerning the caspian sea basin and will contribute to the enhancement of the relative caspian sea level curve for the past 40 ka

beaufort gyre freshwater reservoir state and variability from observations 1 we investigate basin scale mechanisms regulating anomalies in freshwater content fwc in the beaufort gyre bg of the arctic ocean using historical observations and data collected in 2003 2007 specifically the mean annual cycle and interannual and decadal fwc variability are explored the major cause of the large fwc in the bg is the process of ekman pumping ep due to the arctic high anticyclonic circulation centered in the bg the mean seasonal cycle of liquid fwc is a result of interplay between the mechanical ep and thermal ice transformations factors and has two peaks one peak occurs around june july when the sea ice thickness reaches its minimum maximum ice melt the second maximum is observed in november january when wind curl is strongest maximum ep and the salt input from the growing ice has not yet reached its maximum interannual changes in fwc during 2003 2007 are characterized by a strong positive trend in the region varying by location with a maximum of approximately 170 cm a 1 in the center of ep influenced region decadal fwc variability in the period 1950 2000 is dominated by a significant change in the 1990s forced by an atmospheric circulation regime change the center of maximum fwc shifted to the southeast and appeared to contract in area relative to the pre 1990s climatology in spite of the areal reduction the spatially integrated fwc increased by over 1000 km 3 relative to climatology

holocene vegetation history and sea level changes in the se corner of the caspian sea relevance to sw asia climate the palynological investigation of core tm 27 7 m long taken in a dried out lagoon reveals both holocene vegetation history in the north eastern foothills of the alborz mountains and past water level changes of the caspian sea cs the delay in woodland expansion at the beginning of the holocene which is typical of eastern turkey the iranian plateau and recorded in the cs south basin is only weakly felt as the region is close to glacial refugia of trees the succession of the main trees out of their refugia has been established as deciduous quercus carpinus betulus parrotia persica and fagus orientalis pterocarya fraxinifolia presenting therefore close affinities to south european interglacials of the early pleistocene this suggests a similarity in climate a pterocarya decline is observed after ad 495 the studied region is close to the easternmost tree distribution this could explain why it has been affected earlier than elsewhere in the northern alborz and the caucasus in addition human activities during the sasanian empire and the subsequent drying of the climate contributed to weakening the spread of this tree a maximal sea level occurs in the first part of the holocene from 10 6 to 7 2 cal ka it is suggested that the cs levels were significantly influenced by the monsoon precipitations over the western himalayas via the uzboy inflow this is followed by low levels from 7 2 to 3 5 cal ka with a minimum at 3 9 cal ka the neocaspian period should be considered a biozone rather than a chronozone as the environmental conditions reconstructed from dinocyst assemblages are different in shallow shelf waters and in the deep basins

circulation in the vicinity of mackenzie canyon from a year long mooring array abstract data from a five mooring array extending from the inner shelf to the continental slope in the vicinity of mackenzie canyon beaufort sea are analyzed to elucidate the components of the boundary current system and their variability the array part of the marine arctic ecosystem study mares was deployed from october 2016 to september 2017 four distinct currents were identified an eastward directed flow adjacent to the coast a westward flowing surface intensified current centered on the outer shelf a bottom intensified shelfbreak jet flowing to the east and a recirculation at the base of the continental slope within the canyon the shelf current transports 0 12 0 03 sv in the mean and is primarily wind driven the response is modulated by the presence of ice with little to no signal during periods of nearly immobile ice cover and maximum response when there is partial ice cover the shelfbreak jet transports 0 03 0 02 sv in the mean compared to 0 08 0 02 sv measured upstream in the alaskan beaufort sea over the same time period the loss of transport is consistent with a previous energetics analysis and the lack of pacific origin summer water downstream the recirculation in the canyon appears to be the result of local dynamics whereby a portion of the westward flowing southern limb of the beaufort gyre is diverted up the canyon across isobaths this interpretation is supported by the fact that the low frequency variability of the recirculation is correlated with the wind stress curl in the canada basin which drives the beaufort gyre