major pathways of atlantic water in the northern north atlantic and nordic seas toward arctic 1 the major pathways of near surface atlantic water in the northern north atlantic and nordic seas are identified as current speeds above 30 cm s using 1014 lagrangian drifters combined with previously published hydrography the inflow over the scotland greenland ridge and establishment of the two branch norwegian atlantic current nwac are described in light of the circulation in the northern north atlantic the western branch of the nwac appears as a jet in the polar front topographically guided from the iceland faroe front through the nordic seas toward fram strait the eastern branch starts as a shelf edge current above the irish scottish continental shelf and after passing through the faroe shetland channel it continues northward along the norwegian shelf edge toward the arctic with a branch bifurcating into the barents sea the nwac appears to maintain its two branch structure throughout the nordic seas with the atlantic water confined to a 200 600 km wide wedge

can the southern hemisphere annular mode affect china winter monsoon 1 many previous studies suggested that the anomalous northern hemisphere annular mode nam and associated low boundary forcing e g snow cover greatly influence the china winter monsoon cwm variability on interannual to inter decadal timescales in this article it is found that the southern hemisphere annular mode sam also well correlates with the two observed cwm major modes which has not been revealed before note that the two cwm major modes are obtained by performing empirical orthogonal function eof analysis on winter surface air temperature at 160 gauge stations across china for the 1951 2006 period they explain around 70 of the total cwm variances thefirsteofmodeexhibitsahomogeneousspatialpatternwiththecorrespondingprincipal component displaying a significant inter decadal variation which reflects the warming trend in china during the past 56 years the second eof mode shows a meridional seesaw patternandisbasicallyassociatedwithsignificantinterannualvariations bothoftheleading modes are intimately associated with the simultaneous sam like hemispheric circulation anomalies moreover thesam likeanomaliessignalprecursoryconditionsforthefirstcwm mode in boreal autumn the relevant physical mechanisms by which anomalous autumn sam may affect the cwm are investigated with ncar community atmospheric model version 3 cam3 when sam is in a strong phase during boreal autumn the circumantarctic upper level jet stream displaces poleward and the corresponding surface wind speeds reduce in the region between 45s and 30s inducing a hemispheric scale warm sea surface temperature sst belt beneath such an anomalously warm sst belt persists through boreal winter and weakens the hadley cell the weakened hadley cell in boreal wintercorrespondstoanomaloussoutherliesprevailinginthelowertroposphereoverchina which favor a weak cwm the intimate linkage between the autumn sam and cwm may be instrumental for understanding interactions between the northern and southern hemisphere and can provide a way to predict the cwm variations

the anatomy of the arctic frontal zone in the greenland sea from a series of two dimensional expendable bathythermograph xbt surveys conductivity temperature depth ctd sections surface drifters and acoustic doppler current profiler adcp observations the properties and structure of the arctic frontal zone in the greenland sea have been determined the arctic frontal zone appears to be a large scale climatic multifrontal frontal zone the structure of the frontal zone can be discerned from subsurface as well as from surface hydrographic parameters even in summer when a seasonal thermocline covers the subsurface hydrographie structure the arctic frontal zone consists of two semipermanent frontal interfaces with warm saline norwegian atlantic water to the east and arctic water from the greenland sea gyre to the west the two frontal interfaces are bounding a band of shallow cyclonic cold eddies and anticyclonic warm eddies with horizontal scales of the order of 40 50 km the typical diameter of the eddies can be scaled with the local internal rossby radius of deformation the eddy kinetic energy of the surface flow in the frontal zone is of the order of 60 to 85 cm2 s 2 the zonal density gradient in the arctic frontal zone maintains a mean northward geostrophic transport of 3 8 sv averaged over a number of cruises this transport is mainly connected with the frontal interface on the western side of the warm and saline norwegian atlantic water the estimated cross frontal eddy transports of heat and salt appear to be of considerable importance for the conditioning of the greenland sea gyre

global climatic anomalies associated with extremes in the southern oscillation abstract composite temperature and precipitation anomalies during various stages of an event in the southern oscillation so have been computed for several hundred stations across the globe large regions of coherent significant signals are shown to exist for both extremes of the so with warm event signals generally opposite to those during cold events in addition during the year preceding the development of an event in the so year 1 climatic anomalies tend to be opposite to those during the following year year 0 this confirms that the biennial tendency of the so over the pacific indian ocean sectors is also present in more remote regions with climatic signals related to the so many of the signals are consistent enough from event to event to be useful for extended range forecasting purposes

volume heat and freshwater divergences in the subpolar north atlantic suggest the nordic seas as key to the state of the meridional overturning circulation the meridional overturning circulation moc decreases rapidly in subpolar and nordic regions where the warm upper layer loses its buoyancy due to intense heat loss sinks and flows south the maj

mixing driven mean flows and submesoscale eddies over mid ocean ridge flanks and fracture zone canyons abstractto close the abyssal overturning circulation dense bottom water has to become lighter by mixing with lighter water above this diapycnal mixing is strongly enhanced over rough topography i

dominant interannual and decadal variability of winter surface air temperature over asia and the surrounding oceans to clarify the interannual variability of winter surface air temperature sat over asia and the surrounding oceans the authors applied principal component analysis to normalized monthly sats the first mode represents the asian north south dipole pattern with a node over the tibetan plateau this component has close relationships to the arctic oscillation and cold surge variability around southeast asia showing decadal oscillation with signal changes in 1988 and 1997 the second mode is the inner asian mode with a center to the north of the tibetan plateau this component connects to fluctuations of not only the western siberian high but also the icelandic low which is associated with the pattern of the polar vortex over eurasia a recent warming trend and possible relationship to solar activity are also shown the modes of asian sat variability associated with enso are extracted as the north south dipole mode over the tropical western pacific and japan the third mode and silk road mode the fourth mode the two independent modes appear to be caused by different sea surface temperature sst anomalies over the western pacific and indian ocean and their associated atmospheric rossby wave responses the atmospheric wave trains over both the north and south of the tibetan plateau in the third mode and the atmospheric wave train that propagates toward the silk road via greenland in the fourth mode

asymmetric responses of tropical precipitation during enso abstract in response to the zonally symmetric el nino southern oscillation forcing hemispherically asymmetric tropical precipitation anomalies associated with the hadley circulation are found in boreal spring after an el nino peak phase positive tropical precipitation anomalies occur in the southern hemisphere while negative precipitation anomalies are found in the northern hemisphere this zonal asymmetry is more apparent in the el nino decaying phase than in the el nino growing phase the maximum amplitude of this zonal asymmetry lags one season behind the maximum sst anomalies over the tropical eastern pacific this lagged response of the asymmetry is mainly because of the tropical precipitation outside the tropical eastern pacific which is associated with the sst and tropospheric temperature anomalies outside the tropical eastern pacific a combination of the effect associated with the anomalous gross moist stability and the effect of the horizontal moist static energy mse transport is responsi

the reconstructed indonesian warm pool sea surface temperatures from tree rings and corals linkages to asian monsoon drought and el nino southern oscillation 1 the west pacific warm pool is the heat engine for the globe s climate system its vast moisture and heat exchange profoundly impact conditions in the tropics and higher latitudes here september november sea surface temperature sst variability is reconstructed for the warm pool region 15 degrees s 5 degrees n 110 160 degrees e surrounding indonesia using annually resolved teak ring width and coral delta o 18 records the reconstruction dates from a d 1782 1992 and accounts for 52 of the sst variance over the most replicated period significant correlations are found with el nino southern oscillation enso and monsoon indices at interannual to decadal frequency bands negative reconstructed sst anomalies coincide with major volcanic eruptions while other noteworthy extremes are at times synchronous with indian and indonesian monsoon drought particularly during major warm enso episodes while the reconstruction adds to the sparse network of proxy reconstructions available for the tropical indo pacific additional proxies are needed to clarify how warm pool dynamics have interacted with global climate in past centuries to millennia

the habberley formation youngest tremadoc in the welsh borderlands the habberley formation overlies the shineton shale formation in the shelve inlier shropshire and includes the youngest tremadoc strata known from the welsh basin it probably represents deposition during the interval cut out by the sub arenig unconformity in north wales and removed by the sub caradoc unconformity in the wrekin district there is no angular unconformity between tremadoc and arenig in the shelve inlier the habberley formation is likely to correlate in part with the hunnebergian stage of scandinavia it was deposited probably in a largely stagnant basin and records a shallowing upwards sequence prior to the arenig transgression of the stiperstones quartzite a sparse trilobite fauna proves the presence of the angelina sedg vickii biozone and a succeeding interval is characterized by asaphellus cf graffi the trilobites are briefly described they include the first undistorted material of angelina sedgwvickii the brachiopod lingulella bella walcott hitherto known only from eastern newfoundland is described by a w a rushton

north atlantic nordic seas exchanges abstract the northeastern part of the north atlantic is unique in the sense that it is much warmer in the surface than other ocean areas at similar latitudes the main reason for this is the large northward transport of heat that extends to high latitudes and crosses the greenland scotland ridge to enter the nordic seas and the arctic there the warm atlantic water is converted to colder water masses that return southwards over the ridge partly as surface outflows and partly as overflows through the deep passages across the ridge in this paper the state of knowledge on the exchanges especially across the eastern part of the greenland scotland ridge is reviewed based on results from the ices nansen north atlantic norwegian sea exchanges project from the nordic woce project and from other sources the accumulated evidence allows us to describe the exchanges in fair detail the origins of the waters the patterns of their flow towards and over the ridge and their ultimate fate there is also increasing information on temporal variations of the exchanges although dynamical changes are still not well understood quantitative estimates for the volume transport of most of the overflow branches seem reasonably well established and transport measurements of the atlantic inflows to the nordic seas are approaching acceptable levels of confidence which allows preliminary budgets to be presented the deep overflows are driven by pressure gradients set up by the formation of deep and intermediate water the dominance of deep overflows over surface outflows in the water budget argues that this thermohaline forcing also dominates over direct wind stress and estuarine forcing in driving the atlantic water inflow across the greenland scotland ridge while wind stress seems to influence the characteristics and distribution of the atlantic water north of the ridge

on the relationship between western maritime continent monsoon rainfall and enso during northern winter abstract several studies have reported that indonesian rainfall is poorly correlated with el nino southern oscillation enso events during the northern winter wet monsoon season this work studies the relationship between the nino 3 5 s 5 n 150 90 w sea surface temperature sst and the maritime continent monsoon rainfall during 1979 2002 the study indicates that the correlations are mostly negative except in the vicinity of sumatra and malay peninsula smp including the western sections of java and borneo where the correlations range from zero to weakly positive the monsoon rainfall during enso events is influenced by a pair of anomalous walker cells and a low level closed circulation centered near the philippines east of smp the rainfall is negatively correlated with nino 3 sst the anomalous low level wind over the indian ocean west of smp causes rainfall to also be correlated negatively with nino 3 sst but rainfall over smp is sheltered from this effect because of the high mountains along

observed sources and variability of nordic seas overflow the overflows from the nordic seas maintain the deep branch of the north atlantic circulation that is an important part of the global climate system an analysis of observed ocean temperatures and salinities between 1950 and 2005 shows that the atlantic water circulating in the nordic seas is the main source for change in the overflow waters

pathways of inflow and dispersion of warm waters in the nordic seas 1 in this study we use 22 acoustically tracked rafos floats to examine the routes and spreading of warm north atlantic waters entering the norwegian sea between iceland and the faroes the majority of floats crossed the iceland faroe ridge at the eastern end where it is deepest they joined the iceland faroe front but rather than continue north with the outer branch of the norwegian atlantic current into the nordic seas most of them jumped over to the inner branch which continues the inflow through the faroe shetland channel northeast over the voring plateau toward the lofoten basin indeed 17 floats whether deployed near iceland or the faroes did so only 2 floats continued north along the outer branch despite the small numbers these results highlight 1 the strong influence of topography on flow patterns 2 the strong crossover of iceland faroes waters to the inner branch and 3 the rapid and structured spreading into the nordic seas

a new early ordovician didymograptid and its bearing on the correlation of the skiddaw group of england with the toyen shale of scandinavia didymograptus s l rigoletto sp nov is a distinctive species in the balticus group of didymograptids occurring in the toyen shale lower ordovician in three localities in sweden it has a short range near the top of the range of tetragraptus phyllograptoides and it occurs at about the same level at localities in the oslo region norway at most of these localities it occurs within the range of tetragraptus of the approximatus group its presence in the skiddaw group of the english lake district indicates the occurrence there of the basal arenig sensu lato equivalent to the t phyllograptoides biozone of scandinavia and the t approximatus biozone lancefieldian 3 of the australasian succession

on the role of eddies and surface forcing in the heat transport and overturning circulation in marginal seas the factors that determine the heat transport and overturning circulation in marginal seas subject to wind forcing and heat loss to the atmosphere are explored using a combination of a high resolution ocean circulation model and a simple conceptual model the study is motivated by the exchange between the subpolar north atlantic ocean and the nordic seas a region that is of central importance to the oceanic thermohaline circulation it is shown that mesoscale eddies formed in the marginal sea play a major role in determining the mean meridional heat transport and meridional overturning circulation across the sill the balance between theoceaniceddyheatfluxandatmosphericcooling ascharacterizedbyanondimensionalnumber isshownto be the primary factor in determining the properties of the exchange results from a series of eddy resolving primitive equation model calculations for the meridional heat transport overturning circulation density of convective waters and density of exported waters compare well with predictions from the conceptual model over a wide range of parameter space scaling and model results indicate that wind effects are small and the mean exchange is primarily buoyancy forced these results imply that one must accurately resolve or parameterize eddy fluxes in order to properly represent the mean exchange between the north atlantic and the nordic seas and thus between the nordic seas and the atmosphere in climate models

pathways and water mass transformation along and across the mohn knipovich ridge in the nordic seas atlantic water takes various pathways through the nordic seas and its transformation to denser waters forms a crucial connection to the lower limb of the atlantic meridional overturning circulation circulation maps often schematize two distinct pathways of atlantic water one following the norwegian atlantic slope current along the continental slope of norway and one following the norwegian atlantic front current along the mohn and knipovich ridges in this paper the connectivity between the northward flow along these ridges is investigated analyzing trajectories of surface drifters and argo floats we find that only 8 of the floats that travel near the mid ocean ridges take the frontal pathway to the north indeed by tracing numerical particles in a realistic numerical simulation part of the water mass traveling along the mohn ridge follows the 2 500 m isobath eastward and joins the slope current instead of flowing north along the knipovich ridge furthermore north of 74 n frequent exchange between the slope current and the front current is observed therefore the slope current and front current are less isolated than often schematized additionally the observational data set reveals substantial cross ridge exchange 31 of the floats that travel within 60 km from the mid ocean ridges cross it results from numerical simulations indicate that the cross ridge exchange leads to cooling and freshening of the atlantic water along the front deployments of floats near the mid ocean ridges are needed to investigate the pathway of atlantic water and its exchange across the ridge in more detail

correlation between the onset of the east asian subtropical summer monsoon and the eastward propagation of the madden julian oscillation abstractusing the daily outgoing longwave radiation olr the pentad climate prediction center merged analysis of precipitation cmap and the 6 h climate forecast system reanalysis cfsr dataset from 1979 to 2010 a composite analysis along with space time wave filtering is performed to examine the linkage between the madden julian oscillation mjo and the onset of the east asian subtropical summer monsoon eassm over 20 30 n 110 120 e the onset of the eassm is shown to be best characterized by the reversal of the mean meridional wind shear related to the rapid reestablishment of the south asian high sah over the southern indochinese peninsula in the upper troposphere the mean date of easmm onset is near the end of april which is about a month earlier than the typical onset of the east asian summer monsoon further analysis indicates that the onset of the eassm and the reestablishment of sah are often associated with the arrival of the wet phase of the tropical mjo over the central and eas

a revision of ordovician series and stages from the historical type area this paper is a revision of the standard chronostratigraphy of the ordovician of the historical type area in england and wales the revision is a response to the need for more precise definitions of series and stages especially for practical international correlation in some cases this has entailed moving horizons for series bases away from those in the classical sections the scheme will be used as the standard for a forthcoming revision of the correlation chart of the british ordovician system the ordovician is divided into five series tremadoc arenig llanvirn caradoc and ashgill the llanvirn is extended to include part of the classical llandeilo series which is included within it as a stage where stage subdivisions of standard series have not yet been defined as in the tremadoc they are proposed in this paper however bancroft s fine stadial divisions of the caradoc which have been criticized for their brevity and local utility are combined into four new stages which will have wider application the former caradoc subdivisions are retained as substages for the purposes of regional correlation

the contrasting dynamics of the buoyancy forced lofoten and greenland basins abstractthe nordic seas are commonly described as a single basin to investigate their dynamics and sensitivity to environmental changes when using a theoretical framework here we introduce a conc

dynamical influence of the tibetan plateau on the winter monsoon over southeastern asia 1 previous studies have shown 1 that the tibetan plateau produces a significant fraction of the two components of the equatorial mountain torque emt in winter 2 that these torques are in part related to the east asian cold surges and 3 that the cold surges affect the convection over the maritime continent we show here that these relations are strong enough for the convection over the equatorial south china sea to be associated with significant signals on the two components of the emt that can precede by a few days and more the convection these signals are associated to surface pressure and temperature patterns that are strongly reminiscent of the east asian cold surges our results therefore show that the tibetan plateau couple dynamically the midlatitudes and the tropical region and that the vectors of this dynamical coupling are the cold surges this coupling also influences the convection over the northern bay of bengal mainland southeast asia and indonesia

synoptic disturbances over the equatorial south china sea and western maritime continent during boreal winter abstract during boreal winter the maritime continent is a region of deep cumulus convection and heavy precipitation systems that play a major role in several global and regional scale processes over the western part of this region the synoptic scale borneo vortex the northeast cold surge and the intraseasonal madden julian oscillation mjo contribute to the variability in deep convection this work studies the impact on deep convection due to interactions among these three different motion systems furthermore the role of the unique topography of the region is examined with respect to the variability in the synoptic scale cold surge and borneo vortex on the synoptic scale the interaction of northeast winds with local topography and the dynamic response to the change in latitude contribute to the turning of the winds and localized patterns of deep convection in days without a borneo vortex deep convection tends to be suppressed over the south china sea and borneo and enhanced downstream over th

charles lapworth and the biostratigraphic paradigm lapworth s paper on the moffat series 1878 provided a model for deciphering the interminable greywackes of the southern uplands and one which lasted for a century the same paper established graptolites in a dominant position in lower palaeozoic biostratigraphy the changes in the biostratigraphic paradigm are discussed with reference to lapworth s contribution issues implicit in his 1878 paper are still contentious graptolites have exemplified the conflict that can arise between the use of fossils as stratigraphic ciphers on the one hand or as complex organisms to be interpreted biologically on the other they have been subjected to the vicissitudes of stratigraphic fashion it is shown that lapworth s biostratigraphy has been enduring in contrast to his structural or palaeogeographic interpretations however the subsequent separation of litho and chrono from biostratigraphy while conceptually necessary has encouraged an idealistic pursuit of the perfect stratigraphic section for the purpose of defining stratigraphic boundaries this has not always been constructive not least because such boundaries often coincide with events which militate against the preservation of ideal sections but lapworth s close integration of biostratigraphic range with observations on lithology barren beds and fossil preservation may have a new lease of life in the context of event stratigraphy

in pursuit of anomalies analyzing the poleward transport of atlantic water with surface drifters we examine the trajectories of 168 drifters as a proxy for atlantic water flowing through the nordic seas the drifters were released at or passed through the svinoy section off the west coast of norway for comparison we generate a set of synthetic trajectories using a stochastic model with a range of diffusivities with the both sets we determine the transit times of both drifters and particles from svinoy to arctic gateways the barents sea and spitsbergen the mean arrival times to these locations are roughly 200 and 500 days respectively this implies ample time for cooling of the surface waters which increases densities and permits subduction before reaching the arctic however a range of transit times is seen some parcels reach fram strait in only 4 months while others are still in the southern nordic seas after 2 years the results do not support the idea that temperature or salinity anomalies can exist as coherent packets the drifters passing svinoy when treated as a group quickly spread over large distances mixing with water in the norwegian and lofoten basins thus an anomaly entering the nordic seas would quickly be obliterated however the velocity of the clusters center of mass is consistent with anomaly propagation speeds inferred previously from hydrographic measurements suggesting the observed variability is advective in nature

evolution of enso related rainfall anomalies in southeast asia region and its relationship with atmosphere ocean variations in indo pacific sector the southeast asia rainfall sear anomalies depend strongly on phases of el nino la nina using an extended empirical orthogonal function eeof analysis it is shown that the dominant eeof mode of sear anomalies evolves northeastward throughout a period from the summer when el nino develops to spring the following year when the event weakens this evolution is consistent with northeastward migration of the enso related anomalous out going radiation field during boreal summer winter the strong enso related anomaly tends to reside in regions south north of the equator the evolution of dominant mode of sear anomalies is in tandem with the evolution of enso related sea surface temperature sst anomalies the strengthening and weakening of boomerang shaped sst in western pacific the changing sign of anomalous sst in java sea and the warming in indian ocean and south china sea are all part of enso related changes and all are linked to sear anomaly the anomalous low level circulation associated with enso related sear anomaly indicates the strengthening and weakening of two off equatorial anticyclones one over the southern indian ocean and the other over the western north pacific together with patterns of el nino minus la nina composites of various fields it is proposed that the northeastward evolution of sear anomaly is basically part of the large scale eastward evolution of enso related signal in the indo pacific sector the atmosphere ocean interaction plays an important role in this evolution

near surface circulation of the nordic seas as measured by lagrangian drifters in the period june 1991 to august 1993 107 argos tracked drifters drogued to 15 m depth were released in the nordic seas or greenland iceland and norwegian seas the drifter movements revealed the strong and spatially confined current systems along the surface salinity fronts of the iceland faroe frontal zone and of the norwegian coast and along the continental margins and their extensions to the barents sea and spitsbergen the norwegian atlantic current is composed of three distinct streams two continental margin and one coastal branches which join into one single swift mean current west of the lofoten and vesteralen islands where the strongest measured currents are in excess of 110 cm s 1 in addition to the general cyclonic gyre circulation in the nordic seas the drifters indicate smaller cyclonic circulation patterns in all the major subbasins i e the iceland plateau the norwegian the lofoten and the greenland basins no surface signature of the east icelandic current is disclosed by the drifters interpolated and low pass filtered position data were used to construct maps of 15 m depth ensemble mean velocity velocity variability and residence time vigorous eddy fields are dominant in the strong currents and in the lofoten basin eulerian correlations indicate that they tend to propagate to the west in contrast the iceland plateau appears quiescent both in the mean and eddy velocities single particle diffusivities are computed and are found to be in the range 1 7 107 cm2 s 1 the corresponding lagrangian timescale and space scale are 1 3 days and 10 40 km respectively these lagrangian drifter measurements compose the first basin scale accurate near surface velocity data set of the nordic seas

topographic influence on baroclinic instability and the mesoscale eddy field in the northern north atlantic ocean and the nordic seas abstracta weak planetary vorticity gradient and weak density stratification in the northern north atlantic and nordic seas lead to time mean currents that are strongly guided by bottom topography

the stratigraphy correlation provenance and palaeogeography of the skiddaw group ordovician in the english lake district a new lithostratigraphy is presented for the skiddaw group lower ordovician of the english lake district two stratigraphical belts are described five formations are defined in the northern fells belt ranging in age from tremadoc to early llanvirn they are all mudstone or sandstone dominated of turbidite origin in ascending order they are named the bitter beck watch hill hope beck loweswater and kirk stile formations two formations are defined in the central fells belt ranging in age from late arenig to llanvirn these are the buttermere formation a major olistostrome deposit overlain by the tarn moor formation consisting of turbidite mudstones with volcaniclastic turbidite sandstone beds a revised graptolite and new acritarch biostratigraphy for the skiddaw group is presented with eight graptolite biozones and thirteen acritarch assemblages and sub assemblages the provenance of the group is assessed from detailed petrographical and geochemical work this suggests derivation in the early ordovician largely from an old inactive continental arc terrane lying to the south east with the appearance of juvenile volcanic material in the llanvirn comparisons and correlations of the skiddaw group are made with the isle of man and eastern ireland

a sea change in our view of overturning in the subpolar north atlantic to provide an observational basis for the intergovernmental panel on climate change projections of a slowing atlantic meridional overturning circulation moc in the 21st century the overturning in the subpolar north atlantic program osnap observing system was launched in the summer of 2014 the first 21 month record reveals a highly variable overturning circulation responsible for the majority of the heat and freshwater transport across the osnap line in a departure from the prevailing view that changes in deep water formation in the labrador sea dominate moc variability these results suggest that the conversion of warm salty shallow atlantic waters into colder fresher deep waters that move southward in the irminger and iceland basins is largely responsible for overturning and its variability in the subpolar basin

a simple kinematic mechanism for mixing fluid parcels across a meandering jet abstract recent observations of fluid parcel pathways in the gulf stream using isopycnal rafos floats revealed a striking pattern of cross stream and vertical motion associated with meanders bower and rossby 1989 in an attempt to explain the observed pattern a two dimensional kinematic model of a meandering jet has been developed which enables examination of the relationship between streamfunction patterns and fluid parcel trajectories the streamfunction fields are displayed in a reference frame moving with the wave pattern so motions of fluid parcels relative to the jet can be seen more easily the results suggest that the observed pattern of cross stream motion results primarily from the downstream phase propagation of meanders the model successfully reproduces several of the most distinctive features of the float observations 1 entrainment of fluid into the gulf stream occurs at the leading edges of meander extrema while detrainment takes place at the trailing edges 2 exchange between the gu

another look at interannual to interdecadal variations of the east asian winter monsoon the northern and southern temperature modes abstract this study investigates the causes of interannual to interdecadal variability of the east asian ea 0 60 n 100 140 e winter monsoon eawm over the past 50 yr 1957 2006 the winter mean surface air temperature variations are dominated by two distinct principal modes that together account for 74 of the total temperature variance the two modes have notably different circulation structures and sources of variability the northern mode characterized by a westward shift of the ea major trough and enhanced surface pressure over central siberia represents a cold winter in the northern ea resulting from cold air intrusion from central siberia the southern mode on the other hand features a deepening ea trough and increased surface pressure over mongolia representing a cold winter south of 40 n resulting from cold air intrusion from western mongolia the cold northern mode is preceded by excessive autumn snow covers over southern siberia mongolia whereas the cold southern mode is preceded b

why rainfall response to el nino over maritime continent is weaker and non uniform in boreal winter than in boreal summer why rainfall response to el nino is uniform and stronger over the maritime continent mc during el nino developing summer and fall but is weaker and non uniform during el nino mature winter is investigated through the diagnosis of anomalous large scale circulation patterns and a local moisture budget analysis it is found that when anomalous walker cells across the equatorial pacific and indian ocean are strengthened toward el nino mature winter a low level ascending motion anomaly starts to develop over western mc in northern fall due to topographic lifting near sumatra and anomalous wind convergence near west kalimantan easterly anomalies as a part of an anomalous anticyclone in south china sea scs that is developed during el nino and a part of the south easterly from java sea associated with anomalous walker circulation bump into the mountain ridge of sumatra and induce ascending motion anomalies near sumatra meanwhile the anomalous north easterly in the southern flank of the anomalous anticyclone over scs and south easterly over java sea converge into west kalimantan leading to ascending motion there the anomalous ascending motion tend to advect mean moisture upward to moisten lower troposphere in situ this low level moistening eventually sets up a convectively unstable stratification and induces a positive precipitation anomaly in the western mc how the mechanism discussed here is relevant to previous hypotheses and how processes during el nino might differ during la nina are discussed

the holocene environmental changes in southern indonesia reconstructed from highland caldera lake sediment in bali island diatom pollen geomagnetic and geochemical analyses were carried out on a 3 6 m long sediment core taken from lake buyan a highland caldera lake in central bali island to reconstruct the holocene climate changes in equatorial southern indonesia the core represents 8 thousand years sedimentation of organic diatomaceous lake mud constant inclusion of benthic diatom fossils as main components indicated that suspension and inflow of littoral materials were the main sedimentary process the core contained laminated sediments in two distinct intervals at 6 5 5 0 and 3 6 3 1 cal ky bp and multi proxy records showed generally drier climate in these sections especially at 3 6 3 1 cal ky bp lake bottom waters were more reducing condition in these laminated periods probably due to increased lake productivity by prolonged dry season and wind mixing laminae structures were made up of a layer composed of benthic diatoms and amorphous organic materials and a layer made by only planktonic diatom fossils each of which may represent rainy and dry period deposits although southern indonesia shows clear australian monsoon rainfall seasonality at present counting of layer numbers showed interannual cycles of laminae formation prolonged dry seasons could obscured the rainfall seasonality in these periods but precise depositional patterns were elusive unlaminated sections showed homogeneous sediment mixture of benthic planktonic diatoms and more volume of terrigenous materials indicating wetter climate and seasonality similar to the present time this was supported by the higher share of marsh environment pollens reflecting more stable lake level trends the dry climate from 6 5 cal ky bp was in line with the general perception of stronger enso dynamics from the mid holocene due to weaker than before boreal summer insolation but the sporadic appearances of dry periods imply the influence of regional climate forcings such as temporal migrations of inter tropical convergence zone itcz it was however possible that temporal shifts of large climate mode occurred in equatorial pacific and indian oceans wettest climate was inferred from 3 1 cal ky bp to the present and this might reflect increased importance of austral hemisphere atmospheric convection and subsequent southerly position of itcz in austral summer time

the greenland sea tracer experiment 1996 2002 horizontal mixing and transport of greenland sea intermediate water in summer 1996 a tracer release experiment using sulphur hexafluoride sf6 was launched in the intermediate depth waters of the central greenland sea gs to study the mixing and ventilation processes in the region and its role in the northern limb of the atlantic overturning circulation here we describe the hydrographic context of the experiment the methods adopted and the results from the monitoring of the horizontal tracer spread for the 1996 2002 period documented by 10 shipboard surveys the tracer marked greenland sea arctic intermediate water gsaiw this was redistributed in the gyre by variable winter convection penetrating only to mid depths reaching at most 1800 m depth during the strongest event observed in 2002 for the first 18 months the tracer remained mainly in the greenland sea vigorous horizontal mixing within the greenland sea gyre and a tight circulation of the gyre interacting slowly with the other basins under strong topographic influences were identified we use the tracer distributions to derive the horizontal shear at the scale of the greenland sea gyre and rates of horizontal mixing at 10 and 300 km scales mixing rates at small scale are high several times those observed at comparable depths at lower latitudes horizontal stirring at the sub gyre scale is mediated by numerous and vigorous eddies evidence obtained during the tracer release suggests that these play an important role in mixing water masses to form the intermediate waters of the central greenland sea by year two the tracer had entered the surrounding current systems at intermediate depths and small concentrations were in proximity to the overflows into the north atlantic after 3 years the tracer had spread over the nordic seas basins finally by year six an intensive large survey provided an overall synoptic documentation of the spreading of the tagged gsaiw in the nordic seas a circulation scheme of the tagged water originating from the centre of the gs is deduced from the horizontal spread of the tracer we present this circulation and evaluate the transport budgets of the tracer between the gs and the surroundings basins the overall residence time for the tagged gsaiw in the greenland sea was about 2 5 years we infer an export of intermediate water of gsaiw from the gs of 1 to 1 85 sv 1 sv 106 m3 s 1 for the period from september 1998 to june 2002 based on the evolution of the amount of tracer leaving the gs gyre there is strong exchange between the greenland sea and arctic ocean via fram strait but the contribution of the greenland sea to the denmark strait and iceland scotland overflows is modest probably not exceeding 6 during the period under study

puzzling over the dynamics of the lofoten basin a sub arctic hot spot of ocean variability 1 a sub arctic hot spot of intense synoptic scale variability is observed in the lofoten basin lb of the norwegian sea using ers 1 2 and envisat satellite altimetry measurements we discover a cyclonic propagation of the synoptic scale sea surface height anomalies around the center of the lb surface drifter trajectories do not reveal an associated coherent near surface cyclonic flow suggesting that the propagating signals have a wavelike nature we identify a dipole and a quadrupole wave modes rotating around the center of the lb obtain analytic dispersion relations for these modes and demonstrate that the observed propagation is a manifestation of topographic rossby waves most of the observed waves have a wavelength of about 500 km and phase speeds ranging from 2 to 10 km day we show that these waves are largely responsible for the localization and amplification of sea surface height variability in the center of the lb

cooperative effects of tropical pacific and atlantic sst forcing in southern china winter precipitation variability this study investigates the variability of winter precipitation over southern china sc and the impacts of sea surface temperature sst forcing in the tropical pacific and atlantic oceans the sc winter precipitation displays two major spatial modes a same sign mode with the maximum center located in southeastern china and a north south dipole mode with opposite variations between the lower reach of the yangtze river and the southeastern coast of china both modes are associated with the variation of the western north pacific wnp anticyclone the same sign mode is associated with canonical el nino through the pacific east asian teleconnection in the lower troposphere the north south dipole mode is subject to the impact of the western pacific warm pool associated with the central pacific el nino and equatorial atlantic forcing the influence of equatorial atlantic warming is through an upper tropospheric zonal wave pattern from the tropical atlantic to the mid latitudes of east asia both the tropical pacific and atlantic oceanic forcing induce a north south dipole pattern of winter precipitation anomalies over sc by affecting the northward extension of the wnp anticyclone moreover the observed statistical relationship between the dipole mode and the equatorial atlantic sst anomalies is present in hindcasts forecasts of the ncep climate forecast system version 2 cfsv2 confirming a potential source of the predictability of the north south dipole like variation of the winter precipitation in sc

interdecadal changes in the major modes of asian australian monsoon variability strengthening relationship with enso since the late 1970s abstract the present paper develops an integral view of the year to year variability across the entire asian australian monsoon a am system which covers one third of the global tropics between 40 and 160 e using season reliant empirical orthogonal function s eof analysis the authors identified two major modes of variability for the period 1956 2004 the first exhibits a prominent biennial tendency and concurs with the turnabout of el nino southern oscillation enso providing a new perspective of the seasonally evolving spatiotemporal structure for tropospheric biennial oscillation the second mode leads enso by one year the remote el nino forcing the monsoon warm pool ocean interaction and the influence of the annual cycle are three fundamental factors for understanding the behavior of the first mode the monsoon ocean interaction is characterized by a positive feedback between the off equatorial convectively coupled rossby waves and the underlying sea surface temperature sst dipole anoma

new cnes cls09 global mean dynamic topography computed from the combination of grace data altimetry and in situ measurements 1 an accurate knowledge of the ocean mean dynamic topography mdt is mandatory for the optimal use of altimetric data including their assimilation into operational ocean forecasting systems a new global 1 4 resolution mdt was computed for the 1993 1999 time period with improved data and methodology compared to the previous rio05 mdt field first a large scale mdt is obtained from the cls01 altimetric mean sea surface and a recent geoid model computed from 4 5 years of grace gravity recovery and climate experiment data altimetric sea level anomalies and in situ measurements are then combined to compute synthetic estimates of the mdt and the corresponding mean currents while the rio05 mdt was based on 10 years of in situ dynamic heights and drifting buoy velocities the new field benefits from an enlarged data set of in situ measurements ranging from 1993 to 2008 and includes all hydrological profiles from the argo array moreover the processing of the in situ data has been updated a new ekman model was developed to extract the geostrophic velocity component from the drifting buoy measurements the handling of hydrologic measurements has also been revisited compared to the previous rio05 solution the new global mdt resolves much stronger gradients in western boundary currents with mean velocities being doubled in some places moreover in comparison to several other recent mdt estimates we find that the new cnes cls09 mdt is in better agreement with independent in situ observations

baroclinic instability and the mesoscale eddy field around the lofoten basin the vigorous mesoscale eddy field around the lofoten basin west of northern norway is thought to be related to eddy shedding from the norwegian atlantic current flowing along the norwegian coast here we study baroclinic instability in the current with a particular focus on the influence of topography the flow over the steepest part of the continental slope is found to be the most unstable the growth characteristics cannot be understood from eady theory alone but require the consideration of interior potential vorticity gradients a study of the fully developed macroturbulent field shows that eddy kinetic energy is advected away from the generation regions and that nonlinear effects likely draw the eddy statistics away from the linear growth regime

vertical structure and seasonal variability of the inflow to the lofoten basin inferred from high resolution lagrangian simulations the lofoten basin in the eastern nordic seas plays a central role in modifying the warm atlantic water inflow toward the arctic ocean here the atlantic water experiences increased residence times

combined effect of el nino southern oscillation and pacific decadal oscillation on the east asian winter monsoon using long term observational data and numerical model experiments the combined effect of the el nino southern oscillation enso and pacific decadal oscillation pdo on the variability of the east asian winter monsoon is examined in the observations it is found that when the enso and pdo are in phase combinations i e el nino positive pdo phase and la nina negative pdo phase a negative relationship between enso and east asian winter monsoon is significantly intensified in other words when el nino la nina occurs with positive negative pdo phase anomalous warm cold temperatures are dominant over the east asian winter continent on the other hand there are no significant temperature anomalies when the enso and pdo are out of phase combinations i e el nino negative pdo phase and la nina positive pdo phase further analyses indicate that the anticyclone over the western north pacific including the east asian marginal seas plays an essential role in modulating the intensity of the east asian winter monsoon under the changes of enso pdo phase relationship long lasting high pressure and warm sea surface temperature anomalies during the late fall winter and following spring over the western north pacific which appear as the el nino occurs with positive pdo phase can lead to a weakened east asian winter monsoon by transporting warm and wet conditions into the east asian continent through the southerly wind anomalies along the western flank of the anomalous high pressure and vice versa as the la nina occurs with negative pdo phase in contrast the anomalous high pressure over the western north pacific does not show a prominent change under the out of phase combinations of enso and pdo numerical model experiments confirm the observational results accompanying dominant warm temperature anomalies over east asia via strong anticyclonic circulation anomalies near the philippine sea as the el nino occurs with positive pdo phase whereas such warming is weakened as the el nino occurs with negative pdo phase this result supports the argument that the changes in the east asian winter monsoon intensity with enso are largely affected by the strength of the anticyclone over the western north pacific which significantly changes according to the enso pdo phase relationship

graptolites in british stratigraphy 697 taxa of planktonic graptolites are recorded and their stratigraphical ranges are given through 60 biozones and subzones in the ordovician and silurian strata of england wales and scotland in the first such stratigraphical compilation for great britain since the synthesis of elles wood 1901 1918