on the intermediate water masses of the faroe bank channel overflow a review of available hydrographic data from the faroe bank channel indicates that north icelandic arctic intermediate water masses are present in the passage to a larger extent than was previously believed the presently compiled statistics including results on the seasonality are discussed in relation to previous investigations finally a high quality subset of the hydrographic data is used for an analysis of the alongchannel mixing of the intermediate water masses

oceanic influence on the baiu frontal zone in the east china sea a high resolution transect of atmospheric soundings across the kuroshio current in the east china sea was conducted onboard a ship in june 2012 with the objective of analyzing the influence of the complex sea surface temperature sst distribution on the baiu frontal zone bfz expendable bathythermograph castings and continuous surface meteorological observations were also examined two distinct mesoscale atmospheric fronts characterized by changes of wind direction in the lower troposphere and surface air temperature were found in the bfz one northern atmospheric front was observed around the sst front in relation to a warm water tongue extending from the kuroshio a high sst region around the northern atmospheric front enhances unstable near surface stratification and intensifies turbulent heat flux they help modify the marine atmospheric boundary layer in the bfz the other southern atmospheric front was at the southern end of the bfz intense evaporation over the kuroshio and moisture transport by southerly winds were important in forming the conditionally unstable air masses in the lower troposphere of the bfz

a riccati model for denmark strait overflow variability 1 a controlled volume box model of the western basins of the nordic seas for water denser than 1027 8 kg m 3 is constructed where accumulation in volume is driven by net imbalances between prescribed net inflow from the northern eastern and top boundaries qs and hydraulically limited outflow through the denmark strait the resulting riccati equation is solved analytically for filling and flushing experiments with constant qs and numerically for stochastic forcing qs t for small perturbations to qs with white noise spectrum the overflow response is red noise with a time scale between 5 and 15 years depending on the mean interface height and area for qs proportional to the nao index the overflow is positively correlated with the nao a 140 years integration reveals variations in the overflow between 2 5 sv in the 1970s and a maximum of 4 sv in the 1990s hydraulic transport calculations from hydrographic data north of iceland show good agreement with the model hindcast

analogue models of folds above a wrench fault abstract this paper describes the experimental deformation of models made with sheets of paraffin wax simulating a bedded cover resting on a basement wrench fault during the experiments en echelon folds appear in the cover as a result of early fault motion folds first appear at heterogeneities in the bedding and with axes at about 45 to the trace of the wrench fault further fault displacement causes a bulk rotation of fold axes towards parallelism with the basement wrench fault and a resulting curvature of fold axes at larger fault displacement folding affects an area which tends to quickly stabilize in width since folding weakens the sheared cover and subsequent deformation is concentrated in it axial surfaces of folds are initially upright then tend to become inclined with an external vergence forming a fan centered on the basement wrench fault deeper layer deformation close to the basement involves fold reorientations that are greater than in the upper layers therefore down a given vertical line there is no continuity between surface and deep structures the geometry and orientation of folds appearing at later stages of wrenching is controlled by the geometry and orientation of already extant folds

the impact of the wind stress curl in the north atlantic on the atlantic inflow to the norwegian sea toward the arctic 1 the norwegian atlantic current nwac through the norwegian sea serves as a conduit of warm and saline atlantic water from the north atlantic to the arctic ocean an important factor for climate and ecology in this study we concentrate on how the north atlantic wind stress curl nawsc affects interannual variability on the major branch of the nwac the norwegian atlantic slope current nwasc based on wind stress data from the ncep reanalysis and estimated volume transport of the nwasc from current records during 1995 2003 in the svinoy section 62 n our analysis shows that the volume transport in the nwasc exhibits a maximum correlation of 0 88 with the zonally integrated nawsc at 55 n 15 months earlier our findings reveal the nawsc to be a major forcing for interannual variability of the nwasc in the range of 3 0 to 5 3 sv sv 106 m3 s 1 the 15 month time lag appears to be in accordance with a forced baroclinic rossby wave in response to the local ekman pumping changing the baroclinicity and strength of the north atlantic current nac after being converted to a nearly barotropic shelf edge current along the irish scottish shelf through interaction with bottom topography it appears as a barotropic response downstream in the svinoy section this result suggests the possibility of predicting conditions influenced by the nwasc more than a year in advance using the nawsc as a proxy

climatological evolution of the okinawa baiu and differences in large scale features during may and june abstractthe okinawa baiu summer rainy season starts in early may and ends in late june preceding the baiu in mainland japan by approximately 1 month this study investigates the time evolution of the large scale circulation associated with the okinawa baiu using 10 yr 1997 2006 climatologies of precipitation and meteorological fields with particular focus on temperature advection at 500 hpa the onset of the okinawa baiu occurs in early may and is followed by an initial peak in precipitation during mid may the baiu rainband then moves southeastward leading to a short break in baiu precipitation during late may the rainband returns to okinawa in early june and a second peak in precipitation occurs during mid june the baiu rainband withdraws northward in late june the mid may precipitation peak is associated with warm advection at 500 hpa mainly due to the meridional temperature gradient and the prevailing southerly winds this warm advection coincides with upward motion near okinawa however t

centrifuged models of gulf of mexico profiles abstract physical models dynamically scaled in a centrifuge are used to explore the importance of slope progradation in driving internal salt structures much further horizontally than they rise large increments of ductile plastic overburden added at normal gravity values simulated primary clastic sedimentary progradation of a clastic slope over a layer of buoyant fluid simulating salt during load increments at a nominal 800 g in a centrifuge this ductile topographic slope spread over the ductile decollement except for down to basin growth faults all the structures considered to be distinctive in the northern gulf of mexico are simulated in the models that are scaled such that 1 mm and 60 s in the model correspond to 1 1 5 km and 2 6 ma in the prototype ratios of the rate of advance to the rate of rise of the shelf break compared with the rate of advance and increase in relief of salt structures control how much of the deep autochthonous salt is squeezed ahead of the advancing shelf and the paths this salt takes to shallow structural levels the few three dimensional diapiric stocks which developed from many two dimensional mullions in the models spread stock canopies which advanced huge distances before some became tongue canopies by climbing over clastic sediments already aggraded in front of them the models emphasize the significance of ductile spreading of the clastic sediments now being discerned by backstripping

monsoon convection in the himalayan region as seen by the trmm precipitation radar three dimensional structure of summer monsoon convection in the himalayan region and its overall variability are examined by analyzing data from the tropical rainfall measuring mission trmm precipitation radar over the june september seasons of 2002 and 2003 statistics are compiled for both convective and stratiform components of the observed radar echoes deep intense convective echoes 40 dbz echo reaching heights 10 km occur primarily just upstream south of and over the lower elevations of the himalayan barrier especially in the northwestern concave indentation of the barrier the deep intense convective echoes are vertically erect consistent with the relatively weak environmental shear they sometimes extend above 17 km indicating that exceptionally strong updraughts loft graupel to high altitudes occasionally scattered isolated deep intense convective echoes occur over the tibetan plateau wide intense convective echoes 40 dbz echo 1000 km2 in horizontal dimension also occur preferentially just upstream of and over the lower elevations of the himalayas most frequently in the northwestern indentation of the barrier the wide intense echoes have an additional tendency to occur along the central portion of the himalayas and they seldom if ever occur over the tibetan plateau the wide intense echoes exhibit three mesoscale structures amorphous areas lines parallel to the mountain barrier and arc shaped squall lines perpendicular to and propagating parallel to the steep himalayan barrier the latter are rare generally weaker than those seen in other parts of the world and occur when a midlevel jet is aligned with the himalayan escarpment deep and wide intense convective echoes over the northwestern subcontinent tend to occur where the low level moist layer of monsoon air from the arabian sea meets dry downslope flow in a manner reminiscent of severe convection leeward of the rocky mountains in the central usa as the low level layer of moist air from the sea moves over the hot arid northwestern subcontinent it is capped by an elevated layer of dry air advected off the afghan or tibetan plateau the capped low level monsoonal airflow accumulates instability via surface heating until this instability is released by orographically induced lifting immediately adjacent to or directly over the foothills of the himalayas broad 50 000 km2 in area stratiform echoes occur in the eastern and central portions of the himalayan region in connection with bay of bengal depressions their centroids are most frequent just upstream of the himalayas in the region of the concave indentation of the barrier at the eastern end of the range the steep topography apparently enhances the formation and longevity of the broad stratiform echoes monsoonal depressions provide a moist maritime environment for the convection evidently allowing mesoscale systems to develop larger stratiform echoes than in the western himalayan region copyright 2007 royal meteorological society

the deepening of the atlantic water in the lofoten basin of the norwegian sea demonstrated by using an active reduced gravity model 1 the norwegian atlantic current nwac as a poleward eastern boundary current is to be considered as the northern limb of the meridional overturning circulation in the north atlantic moc it transports warm and saline atlantic water aw northward toward the arctic ocean before cooling and mixing with cold and low saline water masses return it to the north atlantic to contribute in the moc in this study we focus on the aw in the lofoten basin lb of the norwegian sea ns where it occupies a wider and deeper domain than farther south and north it comprises the major heat reservoir in the ns with contact with the atmosphere and as such is an important area for cooling and buoyancy loss we show that the deepening of the aw is mainly caused by the reduced northward flow in the lb manifested in the deep counter current encountered by the polar frontal jet we demonstrate this effect by using an active reduced gravity model with a topographically steered deeper flow to achieve maintenance of volume transport the model shows that observed differences must be balanced by an oppositely directed deeper flow in the lb the ocean appears to achieve maintenance of volume transport of aw due to buoyancy loss and varying deeper currents by adjusting the vertical extension of aw resulting in a substantial deepening in the lb based on the good fit between the model and observations the suggested mechanism appears to be credible and feasible

the influence of sea surface temperature on surface wind in the eastern equatorial pacific weekly to monthly variability abstract temporal correlations between near equatorial surface wind and sea surface temperatures sst at 11 w in the eastern pacific ocean are investigated using data from an array of moored sensors between 5 n and 5 s the signature of tropical instability waves with periods of 20 30 days is apparent in time series of sst and both the meridional and zonal wind components results indicate the existence of a band of pronounced horizontal divergence in the surface wind field associated with the large meridional sst gradient equatorial front normally located just north of the equator perturbations of the equatorial front by the instability waves induce fluctuations in the overlying winds evidence of the air sea coupling is stronger in time series of the meridional gradients of wind and sst than between time series of the variables themselves the meridional differencing serves as a high pass filter in the space domain which removes planetary scale wind fluctuations that are unrelated to the local sst

atmospheric responses to kuroshio sst front in the east china sea under different prevailing winds in winter and spring abstractatmospheric responses to the kuroshio sst front in the east china sea under different prevailing winds are examined using high resolution observations and numerical modeling satellite data reveal a significant in phase relationship between sst and surface wind speed indicative of ocean to atmosphere influence the atmospheric response varies according to the relative surface wind direction with respect to the sst front orientation under the alongfront condition low high slp anomalies are found on the warmer colder flank of the front accompanied by surface wind convergence divergence enhanced precipitation and frequent cumulus convection appear over the warm kuroshio suggesting an atmospheric response extending into the free troposphere under the cross front condition when the air blows from cold to warm warm to cold sst divergence convergence is located directly over the sst front and its magnitude is proportional to the downwind sst gradient under such prevailing winds the

experiments on simultaneous faulting and folding above a basement wrench fault abstract wrench zones commonly show en echelon patterns of folds in the stratified cover above a basement fault examples are the darien basin in panama and the inglewood fault trend in california folds are often associated with synthetic and antithetic wrench faults but the time relationships between folds and faults may not be obvious we have done experiments where simultaneous faulting and folding occur above a basement fault four experiments were performed using a simple apparatus capable of imposing localised strike slip motions this apparatus consists of two plastic plates one can be moved laterally past the other by a piston thus modelling lateral motion on a single basement fault models were properly scaled to account for gravitational forces brittle behaviour of sandstone and ductile behaviour of clay or shales in the upper crust each model is a vertical succession of silicone layers and sand layers each layer is 2 mm thick except for the basal silicone layer which is 2 4 6 or 8 mm thick in experiments 1 2 3 or 4 respectively all models were deformed at the same slip rate on the basal fault 1 cm h 1 experiments 1 2 and 3 with 8 cm total horizontal sinistral offset were designed to investigate the influence of basal silicone layer thickness on the deformation of a multilayered model experiment 4 with 20 cm of total offset was designed to investigate the influence of an increasing left lateral offset on folding and faulting with a 2 mm thick basal silicone layer experiment 1 synthetic strike slip faults appeared en echelon above the basement fault no folds were visible at the surface of the experiment but the interfaces between sand and silicone layers showed millimetric folds en echelon above the basement fault with a 4 mm thick basal silicone layer experiment 2 en echelon synthetic strike slip faults and folds appeared above the basement fault faults and folds rotated progressively anticlockwise and synclines were activated as dextral antithetic shear zones with a 6 mm thick basal silicone layer experiment 3 synthetic faults and en echelon folds appeared as before but the fold amplitude was larger than in experiment 2 an increasing left lateral offset produced anticlockwise rotation of faults and folds as before and synclines were activated as dextral antithetic shear zones in experiment 4 after 16 cm of left lateral offset the anticlockwise rotation of the folds was such that antithetic dextral shear zones became almost parallel to the basement fault and were then reactivated as synthetic sinistral shear zones

transfer zones of deformation in thrust wedges an experimental study abstract although numerous transfer zones of deformation have been observed in thrust wedges their mechanisms and conditions of development are poorly understood in this paper three basic questions are addressed 1 1 what are the parameters controlling the genesis of transfer zones 2 2 what are the kinematics of thrust propagation during transfer zone development 3 3 which kinds of geological structure link the two compartments on either side of the transfer zone we attempted to solve these problems using a 3 d experimental approach sand models were used to simulate the foreland a rigid but mobile backstop was used to produced a thrust coulomb wedge which was studied during the various stages of its formation shortening led to the development of transfer zones in the wedge separating two domains of homogenous behaviour and connecting thrust planes in different domains the experimental results show that the development of transfer zones is controlled by mechanical and or geometrical parameters such as 1 1 variations in the sedimentary thickness in the foreland 2 2 the steepness of the backstop 3 3 domains with different basal friction in the foreland 4 4 kinked backstop geometry during deformation of the models two types of thrust sequence were identified alternative thrust propagations on both sides of the transfer zone and synchronous thrust propagations which are anastomosed within the transfer zone 3 d reconstructions revealed that the thrust deformations observed in the transfer zone are oblique ramps the frontal thrust bending of the barbados accretionary complex as well as the imbrication of thrust in the castellane arc and the oblique ramp in the zanskar range are discussed in relation to the mechanisms and structures revealed by the models the results of analogue modelling suggest that the development of transfer zones is directly linked to variations in the boundary conditions mechanical and or geometrical between two adjacent parts of a thrust wedge

deep atmospheric response to the north pacific oceanic subtropical front in spring abstract the north pacific subtropical front stf is a zone of high sea surface temperature sst gradients located around 25 n in the western basin and is most pronounced in spring the stf s atmospheric effects are investigated using satellite observations and an atmospheric reanalysis during april may along the stf surface wind stress curl turns weakly cyclonic in the general background of anticyclonic curls atmospheric column integrated water vapor displays a pronounced meridional maximum along this surface trough suggesting a deep vertical structure cyclonic wind curls occur intermittently at intervals of a few days along the stf in subsynoptic low pressure systems accompanying larger synoptic highs in the main storm track to the north in the subsynoptic surface lows convective rain takes place with deep upward motion moistening the entire troposphere the lows are enhanced by condensational heating leading to the formation of weak cyclonic wind curls the lows display vertical structure ch

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

satellite measurements reveal persistent small scale features in ocean winds four year averages of 25 kilometer resolution measurements of near surface wind speed and direction over the global ocean from the quikscat satellite radar scatterometer reveal the existence of surprisingly persistent small scale features in the dynamically and thermodynamically important curl and divergence of the wind stress air sea interaction over sea surface temperature fronts throughout the world ocean is evident in both the curl and divergence fields as are the influences of islands and coastal mountains ocean currents such as the gulf stream generate distinctive patterns in the curl field these previously unresolved features have important implications for oceanographic and air sea interaction research

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

midlatitude wind stress sea surface temperature coupling in the vicinity of oceanic fronts the influences of strong gradients in sea surface temperature on near surface cross front winds are explored in a series of idealized numerical modeling experiments the atmospheric model is the naval research laboratory coupled ocean atmosphere mesoscale prediction system coamps model which is fully coupled to the regional ocean modeling system roms ocean model a series of idealized two dimensional model calculations is carried out in which the wind blows from the warm to cold side or the cold to warm side of an initially prescribed ocean front the evolution of the near surface winds boundary layer and thermal structure is described and the balances in the momentum equation are diagnosed the changes in surface winds across the front are consistent with previous models and observations showing a strong positive correlation with the sea surface temperature and boundary layer thickness the coupling arises mainly as a result of changes in the flux richardson number across the front and the strength of the coupling coefficient grows quadratically with the strength of the cross front geostrophic wind the acceleration of the winds over warm water results primarily from the rapid change in turbulent mixing and the resulting unbalanced coriolis force in the vicinity of the front much of the loss gain of momentum perpendicular to the front in the upper and lower boundary layer results from acceleration deceleration of the flow parallel to the front via the coriolis term this mechanism is different from the previously suggested processes of downward mixing of momentum and adjustment to the horizontal pressure gradient and is active for flows off the equator with sufficiently strong winds although the main focus of this work is on the midlatitude strong wind regime calculations at low latitudes and with weak winds show that the pressure gradient and turbulent mixing terms dominate the cross front momentum budget consistent with previous work

some dynamical constraints on upstream pathways of the denmark strait overflow abstractthe east greenland current egc had long been considered the main pathway for the denmark strait overflow dso recent observations however indicate that the north icelandic jet nij which flows westward along the north coast of iceland is a major separate pathway for the dso in this study a two layer numerical model and complementary integral constraints are used to examine various pathways that lead to the dso and to explore plausible mechanisms for the nij s existence in these simulations a westward and nij like current emerges as a robust feature and a main pathway for the denmark strait overflow its existence can be explained through circulation integrals around advantageous contours one such constraint spells out the consequences of overflow water as a source of low potential vorticity a stronger constraint can be added when the outflow occurs through two outlets it takes the form of a circulation integral around the iceland faroe ridge in either case the direction of overall

ocean atmosphere covariability in the western arabian sea abstract the western arabian sea exhibits strong spatial variability in sea surface temperature sst during the southwest monsoon with changes in sst that can exceed 5 c over 200 km exploration of satellite based and in situ data shows a strong connection between mesoscale sst features and changes in the atmospheric boundary layer the fundamental relationship is that of weak strong wind velocities overlying cold warm sst features there are also coherent changes in other near surface meteorological parameters such as the air sea temperature difference and relative humidity indicating changes in the stability of the planetary boundary layer over the mesoscale sst features these relationships are similar to those recently reported over the equatorial pacific tropical instability wave region this observed covariability of atmospheric boundary layer structure and sst results in variations of the surface heat and moisture fluxes latent heat flux is modified by changes in relative humidity principa

the sensitivity of the greenland scotland ridge overflow to forcing changes processes that influence the volume and heat transport across the greenland scotland ridge system are investigated in a numerical model with horizontal resolution the focus is on the sensitivity of cross ridge transports and the reaction of the subpolar north atlantic ocean circulation to changes in wind stress and buoyancy forcing on seasonal to interannual timescales a general relation between changes in wind stress or cross ridge density contrasts and the overturning transport of greenland iceland norwegian seas source water is established from a series of idealized experiments the relation is used subsequently to interpret changes in an experiment over the years 1992 97 with realistic forcing on seasonal and interannual timescales there is a clear correlation between heat flux and wind stress curl variability the realistic model suggests a steady decrease in the strength of the cyclonic subpolar gyre of the north atlantic with a corresponding decrease in heat transport during the 1990s

active normal faulting and crustal extension a world wide review of fault plane solutions and focal depths for large normal faulting earthquakes on the continents shows that the overwhelming majority of such earthquakes nucleate in the depth range 6 15 km on faults dipping between 30 and 60 in the few cases where levelling or seismic data are good enough these normal faults are shown to be approximately planar from the surface to their nucleation depth at the base of the brittle crust there is evidence that in some cases as a result of the enormous transitory increase in strain rate during large earthquakes rupture continues into the normally ductile lower crust on surfaces with substantially gentler dips these low angle surfaces may be analogous to some of the detachments seen in metamorphic core complexes of the western usa but the nature of the motion on them depends on strain rate as well as on rheological contrasts between the detachments and the blocks on either side such contrasts however are unlikely to introduce substantial curvature to an originally planar shear zone if the observed spread in active normal fault dips is caused by rotation of the faults and the blocks they bound during extension then a maximum value of 1 7 can be accommodated by seismic activity on a single generation of normal faults with continued extension either a new generation of steeper faults cutting the rotated first faults is likely to form or the deformation will continue aseismically on faults dipping at less than 30 large earthquakes have not been observed to nucleate on very low angle 20 normal faults within the continental crust anywhere in the world such faults can of course move aseismically but are unlikely to do so on a large scale within the upper crust in areas where steep normal faults are seismically active thus extensional models that require concentrated simple shear on large sub horizontal faults within the brittle upper crust will also require a spatial separation between aseismic very low angle faulting and seismic highangle faulting since seismogenic high angle faults dominate the topography of extending regions upper crustal very low angle faulting if it occurs on a large scale presumably does so in areas that are relatively fiat

experiments on shortening of a 4 layer model of the continental lithosphere davy ph and cobbold p r 1991 experiments on shortening of a 4layer model of the continental lithosphere in p r cobbold editor experimental and numerical modelling of continental deformation tecronophysics 188 l 25 we present an experimental method for modelhng lithospheric deformation the method is based on a simplified profile of lithosphere rheology where only four layers are considered brittle crust ductile crust brittle mantle and ductile mantle the strengths of the four layers calculated from laboratory determined flow laws depend strongly on geothenns and slightly on strain rates and deformation regimes the rheological profiles of the lithosphere have been recreated in experimental models built with analog materials sand silicone putty and golden syrup which flow under their own weight during lithospheric shortening the style of deformation depends on the relative strengths of the four layers especially those in the mantle of special importance is the existence or non existence of a brittle mantle the initial stages of compression often produce flexures or buckles without local isostatic compensation buckling exerts a strong control on the localisation of thrust faults in later stages the thrusts tend to form at the inflexion points of buckles the style of crustal thickening depends on the relative thicknesses and resistances of the lithospheric layers in 2 layer lithospheric models without resistant mantle shortening was concentrated upon a small number of thrusts widely spaced in 3 layer models shortening was concentrated into a large number of reverse faults more closely spaced and more steeply dipping than before in clayer models a single thrust formed in the brittle mantle motion on this thrust dragged the crustal layers down forming an asymmetric crustal root with steep imbricate slices

analogue modelling of orthogonal and oblique rifting abstract the three dimensional progressive development of orthogonal and oblique rift systems has been simulated using scaled analogue sandbox models the orientation of the zone of rifting where angle between the rift axis and the extension direction was varied systematically from 90 orthogonal rifting to 75 60 and 45 oblique rifting completed models were impregnated and sectioned both vertically and horizontally orthogonal rift models are characterized by long straight rift border faults and intra rift faults perpendicular to the extension direction oblique rift models are characterized by shorter segmented rift border faults and intrarift faults in the oblique models the rift border faults formed en echelon arrays parallel to the inderlying zone of basement stretching whereas the intra rift faults formed at a high angle to the extension vector increased extension in the moderately oblique and oblique rift systems 60 and 45 caused the intra rift faults to rotate towards parallelism with the rift border faults no strike slip or oblique slip transfer faults were found in any experiments rift border faults and intra rift faults in the models are segmented along strike with relay ramp structures formed between overlapping fault tips along the strike of the rift variations in half graben polarities and offsets of depocentres are accomplished by accommodation zones formed by interlocking conjugate fault arrays the experimental fault patterns compare well with the fault architectures found in those modern or relatively young rift systems where well defined basement controlled strike slip or oblique slip transfer faults are absent an accommodation zone model consisting of interlocking conjugate extension faults is proposed for the along strike switching of half graben asymmetries and offsetting of depocentres in rift systems the fault geometries in the analogue models can be used as templates for recognition of fault styles in both orthogonal and in oblique rift environments

deep atmospheric response to the spring kuroshio over the east china sea abstractthe atmospheric response to the spring kuroshio front over the east china sea is investigated using a suite of high resolution satellite data and a regional atmospheric model the atmospheric response appears to extend beyond the marine atmospheric boundary layer with frequent occurrence of cumulus convection in spring quick scatterometer quikscat wind speed shows a clear effect of sea surface temperature sst with high low wind speed observed over the warm cold tongue this in phase relationship between sst and surface wind speed is indicative of sst influence on the atmosphere wind convergence is found on the warmer flank of the kuroshio front accompanied by a narrow rainband the analysis of satellite borne radar measurements indicates that deep convection appears over the kuroshio warm tongue in the spring season with enhanced convective precipitation frequent occurrence of cumulus convection and increased precipitation cloud tops in altitude these deep convective activities

structural controls on palaeozoic basin evolution and inversion in southwest wales the tectonic evolution of sw dyfed is presented in terms of a model of basin evolution and subsequent destruction by reactivation of the basin bounding faults in contractional mode movements along long lived palaeozoic extensional faults were reversed during variscan compression with the pre existing faults accommodating the contraction in addition to the development of a thin skinned thrust and fold system basin analysis of the pre variscan extensional system uses sedimentological and stratigraphical evidence to constrain the timing of movements of the basin bounding faults thus allowing division of the stratigraphy into depositional megasequences related to these extensional movements field examples on all scales illustrate active extension during the palaeozoic structural cross sections through sw dyfed demonstrate the interrelationship of the extensional and contractional deformations with palinspastic restorations of the cross sections illustrating the complexity of the pre variscan template

influence of kuroshio sst front in the east china sea on the climatological evolution of meiyu rainband the influence of kuroshio sea surface temperature sst front in the east china sea ecs on the temporal evolution of climatological meiyu rainband was investigated using a suite of high resolution satellite observations and a reanalysis dataset from 2000 to 2011 during the northward seasonal march of meiyu rainband from the warmer flank of the sst front to the colder flank the climatological rainband strength weakened substantially despite large scale environment became more conducive to intensify precipitation a sharp reduction in occurrence frequency of precipitation with relatively shallower depth and smaller intensity was responsible for the weakening of meiyu rainband during the northward migration of meiyu rainband individual precipitation events became deeper and more intensive and the contribution of convective precipitation to the rainband was enhanced associated with the seasonal northward extension of high convective instability region over the ecs the characteristics of meiyu rainband evolution were generally supported by cloud observations when meiyu rainband was located on the warmer flank of the sst front local enhanced mean surface wind convergence and variance of convergence at synoptic timescale by the warm sst of the kuroshio favored strong surface convergence that may trigger precipitation a detailed moisture budget analysis revealed that the major part of moisture for meiyu precipitation was supplied by low level wind convergence with much smaller contribution from moisture advection the variation of climatological precipitation associated with meiyu northward migration depended on sst modulation of both surface evaporation and low level moisture convergence over the ecs

mechanisms for the variability of dense water pathways in the nordic seas 1 interannual changes in simulated flow fields of the nordic seas are analyzed with respect to their dynamic causes and consequences regarding the flow of dense water from the nordic seas into the subpolar north atlantic across the greenland iceland scotland ridge the simple case of pure density driven outflow with closed northern boundaries shows that dense water mainly originates in the northern lofoten basin and flows southward in three branches namely along the norwegian continental slope along the mohn and jan mayen ridges and a weak current along the east greenland continental slope adding variable exchange through fram strait shows a strengthening of the most western branch and strong recirculations that may reverse the other two branches for this case we find in phase modulation of the denmark strait overflow dso by a changing fram strait supply and a faroe shetland transport that is in opposite phase the scaling of this relation provides a potential explanation of recently observed dso changes however details of the changes in the simulated pathways suggest in accord with the size of the prescribed varying fram strait supply basin wide wind stress curl and local convection which feeds water from different source regions into the outflow pathways as the primary cause for the upstream flow field reorganizations

how normal faulting and sedimentation interact to produce listric fault profiles and stratigraphic wedges abstract in a series of scale experiments we generated listric normal faults by extending models composed of colored sand layers deposited at regular time intervals throughout deformation during syntectonic sedimentation progressive bulk extension along a single set of faults caused domino type tilting of fault blocks underlying tilted faults propagated upwards with constant dips into newly sedimented layers hence fault profiles become progressively more listric tilting of the free surface resulted in asymmetrical depressions and in fan shaped deposits stepwise or continuous geometric models of domino tilting and synchronous sedimentation yield the same structural and stratigraphic features as observed in the sand models the continuous geometric model shows that a critical parameter governing fault curvature is the ratio r between rates of bulk strain and sedimentation both types of models reveal that synchronous sedimentation and bulk extension are capable by themselves of generating listric normal faults

modelling the geometry of coulomb thrust wedges internal geometry and detachment of coulomb thrust wedges is examined in a combined gravity and pressure force field under various boundary conditions and coulomb parameters frontally buttressed sand wedges accreted with narrow tapers above soles with negligible friction in these models serial imbricates stepped up in conjugate sets which operated synchronously or serially with increases in sole friction model coulomb wedges accreted in piggyback style with enhanced taper but narrower spacing of imbricates in this mode flat topped box fold anticlines nucleated at the frontal tip of a sole thrust prior to the fore limb failing as a ramp the initial ramp thrusts subsequently rotated and steepened to acquire concave upwards listric geometry when cohesion was a significant component of strength and the sand grains interlocked thoroughly ramp climb during piggyback thrusting occurred through the generation of a stack of backthrusts the taper of cohesionless sand wedges which lack any length scale was consistent with the critical cohesionless coulomb wedge taper in contrast the taper of experimental cohesive sand wedges which are scale dependent was consistent with the theoretical cohesive coulomb narrow taper only when the cohesive length scale was lr sr rar 10 6 this was constrained by comparing geometry of cohesive sand wedges shortened at different body force per unit mass

interannual changes in the overflow from the nordic seas into the atlantic ocean through denmark strait the global thermohaline circulation is an important part of earth s climate system cold dense water formed in the nordic seas enters the atlantic ocean as overflows across the sills of the greenland scotland ridge the denmark strait overflow dso is one of the main sources of north atlantic deep water until now the dso has been believed to be stable on interannual timescales here for the first time evidence is presented from a 4 year program of observations showing that overflow transports in 1999 2000 were approximately 30 higher than previous estimates later transports decreased remarkably during the observation period coincident with a temporary temperature increase of about 0 5 c

on the effective capacity of the dense water reservoir for the nordic seas overflow some effects of topography and wind stress abstractthe overflow of the dense water mass across the greenland scotland ridge gsr from the nordic seas drives the atlantic meridional overturning circulation amoc the nordic seas is a large basin with an enormous reservoir capacity the volume of the dense water above the gsr sill depth in the nordic seas according to previous estimates is sufficient to supply decades of overflow transport this large capacity buffers overflow s responses to atmospheric variations and prevents an abrupt shutdown of the amoc in this study the authors use a numerical and an analytical model to show that the effective reservoir capacity of the nordic seas is actually much smaller than what was estimated previously basin scale oceanic circulation is nearly geostrophic and its streamlines are basically the same as the isobaths the vast majority of the dense water is stored inside closed geostrophic contours in the deep basin and thus is not freely available to the overflow the positive wind stress curl in the no

air sea heat exchanges characteristic of a prominent midlatitude oceanic front in the south indian ocean as simulated in a high resolution coupled gcm abstract an integration of a high resolution coupled general circulation model whose ocean component is eddy permitting and thus able to reproduce a sharp gradient in sea surface temperature sst is analyzed to investigate air sea heat exchanges characteristic of the midlatitude oceanic frontal zone the focus of this paper is placed on a prominent sst front in the south indian ocean which is collocated with the core of the southern hemisphere storm track time mean distribution of sensible heat flux is characterized by a distinct cross frontal contrast it is upward and downward on the warmer and cooler flanks respectively of the sst front acting to maintain the sharp gradient of surface air temperature sat that is important for preconditioning the environment for the recurrent development of storms and thereby anchoring the storm track induced by cross frontal advection of cold warm air associated with migratory atmospheric disturbances the surface flux is highly variable with intermittent en

ocean frontal effects on the vertical development of clouds over the western north pacific in situ and satellite observations abstract a suite of shipboard and satellite observations are analyzed and synthesized to investigate the three dimensional structure of clouds and influences from sea surface temperature fronts over the western north pacific sharp transitions are observed across the kuroshio extension ke front in the marine atmospheric boundary layer mabl and its clouds the ocean s influence appears to extend beyond the mabl with higher cloud tops in altitude along the ke front than the surroundings in winter intense turbulent heat release from the ocean takes place on the southern flank of the ke front where the cloud top penetrates above the mabl and reaches the midtroposphere in this band of high cloud tops frequent lightning activity is observed the results of this study suggest a sea level pressure mechanism for which the temperature gradient in the mabl induces strong surface wind convergence on the southern flank of the ke front deepening the clouds there in early summer sea fog frequently occurs on

experimental models of hangingwall deformation in ramp flat listric extensional fault systems abstract the results of three experimental models of ramp flat extensional fault systems are presented the experiments were constructed from sand and mica layers to form an anisotropic sequence that would respond to the imposed deformation by both faulting and folding the geometry of the underlying detachment controls the deformation in the hangingwall sequence ramp flat detachment geometries produce an upper roll over with a crestal collapse graben system a ramp syncline and fold reverse fault zone and a lower roll over with a crestal collapse graben system short ramp geometries produce only minor perturbations in a larger roll over structure as extension progresses the crestal collapse systems migrate and superimpose earlier systems the models of ramp flat extensional structures produce templates for the interpretation of natural ramp flat listric fault systems

the influence of topography on the stability of the norwegian atlantic current off northern norway abstractthe steep continental slope off the lofoten vesteralen islands of northern norway appears to be the source of the most intense mesoscale eddy field in all of the nordic seas here we use li

on the deep water flow through the faroe bank channel a substantial part of the norwegian sea deep water outflow into the north atlantic takes place via the faroe bank channel the deepest passage through the greenland scotland ridge in order to estimate this flux of cold low saline bottom water a field survey comprising hydrographie observations as well as current measurements was carried out in the channel during may 1983 transport calculations were undertaken for a total of four sets of observations and yielded values ranging from 1 5 to 1 9 sverdrup the outflow is most likely subjected to hydraulic control and consequently a simple model has been formulated in order to determine the maximum discharge through a rotating channel of parabolic cross section this geometry is well adapted to the topography of the faroe bank channel and the theoretically predicted magnitude of the transport was found to be in good agreement with the observations

experiments on basin inversion above reactivated domino faults abstract results are presented from scaled sand box experiments which investigate the structural inversion of half graben basins generated by the contractional reactivation of extensional domino fault systems the overburden was deformed above a series of rigid basement fault blocks that were extended in a domino manner the models were constructed from either 1 sand with mica interlayers anisotropic behaviour 2 pure sand isotropic behaviour or 3 a sand clay mixture behaviour with increased competence during the extensional phase of deformation sand or alternating sand mica layers were deposited in teh half grabens associated with individual domino faults to simulate a syn extensional stratigraphic sequence together with a component of overall subsidence after termination of the extensional phase sand layers were added to represent a post rift passive subsidence stratigraphy subsequent contraction of the experimental configuration resulted in progressive reactivation of the domino fault system which was accompanied by back rotation of both the footwall and hanging wall in each of the individual fault blocks this produced null points along the profile section of the fault planes which separated net contraction above from net extension below continued shortening of the system led to further contraction being accommodated along footwall shortcut faults it is suggested that these shortcuts developed in response to 1 the accommodation of space problems generated by increased bed length in the graben acquired during extension and 2 by more efficient low angle fault trajectories in keeping with coulomb failure during horizontal to subhorizontal compression during inversion in the anisotropic model folding in the footwall partially suppressed the initiation of footwall shortcut faults footwall shortcut faulting did not occur in experiments where the dips of the original extensional faults were decreased before the inversion in all inversion experiments the contractional deformation associated with the shortening of the half graben was concentrated in the footwall to each domino basin bounding fault a control experiment in which an undeformed sand pack was deposited above an extended series of basement fault blocks revealed that the early extensional architecture formed in the other experiments had a profound influence on the resultant inversion geometries the results show clear similarities to interpreted examples of natural basin inversion structures associated with reactivated domino fault systems as well as to inferred strike slip induced flower structures

north atlantic arctic mediterranean exchanges in an ensemble hindcast experiment 1 an ensemble hindcast approach is designed to simulate north atlantic circulation changes during the period 1948 2005 using the max plank institute ocean model forced by atmospheric reanalysis data the experiment seeks to isolate oceanic changes related to the atmospheric forcing history by evaluating the role of initial conditions and masking internal model variability in the ensemble mean results characteristics of the complete north atlantic arctic mediterranean exchange system is described at key sections by time series of exchanges of volume ice heat and liquid freshwater volume transports are divided into water masses by properties and the constructed climatology of exchanges is shown to compare well with available observational estimates of individual branches in response to the atmospheric forcing history we find a modest but robust decline of the atlantic meridional overturning circulation of 0 4 sv decade in total 2 2 5 sv since 1948 in contrast overturning exchanges with the north atlantic and nordic seas and with the nordic seas and arctic ocean show no sign of cessation a marked increase in the freshwater storage of the nordic seas and in particular of the subpolar atlantic accompany the model decline in atlantic overturning the characteristics of the modeled freshening bears similarities with observed patterns of change since the 1950s but whereas the origin of observed freshening is uncertain freshening in the model predominantly results from dynamic changes linked to prominent changes in atmospheric circulation moreover documented increase in the drainage of major arctic rivers is found to have a negligible effect on the oceanic changes

sst induced surface wind variations over the brazil malvinas confluence satellite and in situ observations abstract the confluence of the brazil malvinas currents maintains strong sea surface temperature sst fronts in the midlatitude southwestern atlantic year round sst effects on near surface stability and surface wind variations are examined in this region using satellite and in situ datasets satellite observations show strong weak surface wind speeds over the warm brazil cold malvinas current a novel feature of this study is the construction of a high resolution surface meteorological dataset that is based on historical ship observations analysis of this new in situ dataset reveals an increased reduced sea air temperature difference over the brazil malvinas current indicating destabilization stabilization in the atmospheric boundary layer these results are consistent with the sst induced vertical mixing mechanism for wind adjustment the sst effect on the near surface atmosphere is observed both in the climatology and on interannual time scales in the brazil malvinas confluence along a zo

globally unified monsoon onset and retreat indexes abstract different criteria have been used in the past to define the monsoon onset and retreat over different monsoon regions and even over different parts of the same monsoon region here an objective criterion is proposed to define for the first time globally unified summer monsoon onset or retreat dates using a single meteorological variable i e the global daily 1 1 normalized precipitable water data with the threshold value being the golden ratio 0 618 results are found to be consistent with those determined using long term rainfall data over most monsoon regions the precipitable water data have also been used to refine the definition of monsoon regions on a grid cell by cell basis the objective definitions of these basic monsoon characteristics would provide one of the necessary foundations for global monsoon research they along with the onset retreat data over a 10 yr period 1988 97 would also facilitate the diagnostics and validation of global monsoon simulations

geology and geophysics of the rukwa rift east africa exploration in the rukwa rift using gravity and seismic reflection surveys fieldwork and drilling has defined the structure and stratigraphy of the basin in greater detail than any other part of the western rift the stratigraphy comprises precambrian basement karroo sandstones shales and coals upper miocene red beds and miocene recent lacustrine and fluvial sediments during miocene recent rifting the greatest sediment input apparently came from axial fluvial systems flowing from the northwest and southeast the southwestern area experienced alternating shallow lacustrine and fluviodeltaic conditions during the miocene recent cenozoic age rift structures have a dominant nw se and a subordinate n s trend the nw se trend tends to follow a precambrian basement and later karroo structural trend ne sw seismic lines indicate up to 10 km extension of the tertiary section in a direction oblique to the probable e w regional extension direction in the southeastern portion of the basin both karroo and tertiary quaternary sediments expand into the lupa fault zone reaching thicknesses of up to 3 and 7 km respectively tertiary quaternary sediment thicknesses decrease northwestward accompanied by a decrease in the amount of extension and a broadening of the basin as extension is transferred to the lake tanganyika rift

regional seasonal and diurnal variations of extreme convection in the south asian region abstract temporal and spatial variations of convection in south asia are analyzed using eight years of tropical rainfall measuring mission trmm precipitation radar pr data and ncep reanalysis fields to identify the most extreme convective features three types of radar echo structures are defined deep convective cores contiguous 3d convective echo 40 dbz extending 10 km in height represent the most vertically penetrative convection wide convective cores contiguous convective 40 dbz echo over a horizontal area 1000 km2 indicate wide regions of intense multicellular convection and broad stratiform regions stratiform echo contiguous over an area 50 000 km2 mark the mesoscale convective systems that have developed the most robust stratiform regions the preferred locations of deep convective cores change markedly from india s east coast in the premonsoon to the western himalayan foothills in the monsoon they form preferentially in the evening and over land as near surface moist flow is cap

sandbox model studies of inversion tectonics abstract scaled plane strain sandbox models have been used to simulate basement controlled structural inversion in a sedimentary overburden two basement configurations were tested in the first one reversal of movement along vertical and normal faults that controlled a graben relief induced only a partial recovery of displacement along the pre existing overburden faults the inversion produced new reverse faults in the footwall of the pre existing overburden faults the reactivated normal faults and the new reverse faults defined wedge shaped fault blocks at the edges of the inverted structure in the second configuration the relationship between inversion and tilted fault blocks was tested when a tilting basement block does not move parallel to its bounding fault a compression is induced in the overburden which generates an inverted structure bounded by new reverse faults both experiments show that structural inversion not only reactivates pre existing faults but also generates new faults in the overburden faults related to inversion are the result of horizontal compression either associated with rotation of one of the fault blocks or with vertical uplift of basement blocks

on the role of sea surface temperature gradients in forcing low level winds and convergence in the tropics abstract we examine the importance of pressure gradients due to surface temperature gradients to low level p 700 mb flow and convergence in the tropics over time scales 1 month the latter plays a crucial role in determining the distribution of cumulonimbus convection and rainfall our approach is to consider a simple one layer model of the trade cumulus boundary layer wherein surface temperature gradients are mixed vertically consistent with ecmwf analyzed data the top of the layer is taken at 700 mb the influence from higher levels is intentionally suppressed by setting horizontal pressure gradients and frictional stresses to zero at the top of the layer horizontal convergence within the layer is taken up by cumulonimbus mass flux however the development of the cumulonimbus mass flux is associated with a short relaxation time o hr roughly the development time for such convection during this short time horizontal convergence acts to redistribute mass so as to reduce horizontal pressur

causes of changes in the denmark strait overflow abstract the warming nordic seas potentially tend to decrease the overflow across the greenland iceland scotland ridge gisr system recent observations by macrander et al document a significant drop in the intensity of outflowing denmark strait overflow water of more than 20 over 3 yr and a simultaneous increase in the temperature of the bottom layers of more than 0 4 c a simulation of the exchange across the gisr with a regional ocean circulation model is used here to identify possible mechanisms that control changes in the denmark strait overflow and its relations to changed forcing condition on seasonal and longer time scales the authors establish links of the overflow anomalies to a decreasing capacity of the dense water reservoir caused by a change of circulation pattern north of the sill on annual and shorter time scales the wind stress curl around iceland determines the barotropic circulation around the island and thus the barotropic flow through denmark strait for the overlapping time sc

balanced cross section construction from seismic sections in areas of extensional tectonics abstract the application of the technique of balanced section construction initially developed for areas of compressional folding and faulting is reviewed with reference to extensional tectonics a number of examples are discussed where these techniques have been successfully applied in the north sea the interpretation of geoseismic sections is considered to be greatly assisted by careful application of geometrical balance and a consideration of strain even in areas of low crustal extensions the nature of seismic sections however places limitations on the validity of balancing which must be borne in mind with such interpretations and wherever possible the balancing of a geoseismic section should be confirmed by complete depth conversion the rapid testing of the integrity of the geoseismic section by attempting to balance the section at the interpretational phase can eliminate many problems as well as allowing the fullest use to be made of the geophysical information

development of the north viking graben inferences from laboratory modelling abstract the north viking graben is a classic sedimentary basin in the north sea that has been thoroughly studied over the last decade despite the amount and quality of seismic and well data now available the processes of extension remain unclear and the relationship between sedimentation and deformation is still a matter of debate we present the results of small scale laboratory modelling the models are made with sand and silicone putty to simulate brittle and ductile behaviour on a crustal scale the experiments were designed to study the effects of a the degree of coupling between brittle and ductile layers b the obliquity of extension and c the reactivation of inherited crustal scale structures the results are used to discuss the symmetry of extensional processes on crustal and lithospheric scales as well as the relationship between sedimentation and deformation it is proposed that the asymmetry of faulting in the upper crust and the nearly symmetric thinning of the whole crust are not mutually exclusive a model involving nearly pure shear on the lithospheric scale is used to explain the development of an asymmetrical basin at shallow level in addition this model accounts for the nearly horizontal stratification of lower cretaceous sediments the basal cretaceous unconformity which caps many of the normal faults and the localization of deformation to the west of the graben during the lower cretaceous

effect of overburden thickness on thrust belt geometry and development laboratory sand models simulating development of thrust belts indicate that 1 distance between the backstop and the first formed thrust is a linear function of initial sand layer thickness 2 spacing between the first two thrusts is most likely a nonlinear function of initial sand layer thickness 3 initial dip of successive ramps decreases progressively toward the foreland because of variations in principal stress directions with depth and or changes of mechanical properties of sand with increasing overburden 4 faults to the hinterland steepen and become less active as hinterland thrust sheets undergo penetrative shear during sand wedge growth and 5 new ramp initiation occurs to the hinterland of the basal detachment tip line these observations can be interpreted both in context of area balance considerations and soil mechanics theory if initial sand layer thicknesses in our models represent syntectonic overburden in natural thrust belts i e distance between the ground surface and the detachment then our results suggest that locations of some thrust belt salients are controlled by along strike variations in stratigraphic thicknesses and that initial thrust spacing decreases progressively to the foreland if the thrust belt involves a foreland tapering basin furthermore our sand model observations suggest that the concept of a fixed rigid backstop in the hinterland of thrust belts may be misleading as a consequence of thickening the hinterland portion of the thrust belt becomes stabilized and effectively becomes the backstop itself

two types of thermobaric deep convection possible in the greenland sea 1 a numerical experiment has been executed with a fine resolution grid size of 1 m two dimensional model to investigate detailed features of open ocean deep convection related to the nonlinearity of the equation of state for seawater and to interpret recent summer observations in the greenland sea suggesting two types of winter convection when cold fresh waters arctic origin occupy the surface mixed layer convective overturning of the water column occurs abruptly thermobaric convective plumes branch into small scale o 10 100 m eddies and engulf ambient deep water on the way down they induce significant fluctuations in profiles of water properties but do not homogenize the overturned layer completely as a result stable stratification remains at depths where temperature salinity and potential density decrease when warm saline waters atlantic origin exist in the surface mixed layer it deepens by surface cooling entraining the underlying water vigorously water properties are nearly homogenized in the deepening mixed layer and have opposite features to the first case these results support a deduction that two different profiles of water properties observed in the greenland sea are signatures of two types of deep convection

arctic warming through the fram strait oceanic heat transport from 3 years of measurements we present estimates of volume and heat transport through fram strait for the period 1997 to 2000 from data of moored instruments full depth volume transports at 78 55 n were in the order of 10 sv both northwards and southwards with an annual mean net transport between 2 and 4 sv to the south the temperature of the northward flow of atlantic water had a strong seasonality with a minimum in winter nevertheless the northward heat transport was highest in winter caused by the winter maximum of northward volume transport during the three years of observation the heat transport in the west spitsbergen current increased from 28 to 46 tw as a result of both increased speed and temperature in contrast to the west spitsbergen current the volume and heat transport of east greenland current remained fairly constant an integration over a subsection of the east greenland current showed similar values of volume transport to that obtained by measurements in the 1980s foldvik et al 1988 the southward heat transport through modified atlantic water weakened slightly between 1997 and 1999 despite increased temperatures

the effects of sst induced surface wind speed and direction gradients on midlatitude surface vorticity and divergence abstract the effects of surface wind speed and direction gradients on midlatitude surface vorticity and divergence fields associated with mesoscale sea surface temperature sst variability having spatial scales of 100 1000 km are investigated using vector wind observations from the seawinds scatterometer on the quick scatterometer quikscat satellite and sst from the advanced microwave scanning radiometer for earth observing system amsr e aqua satellite the wind sst coupling is analyzed over the period june 2002 august 2008 corresponding to the first 6 years of the amsr e mission previous studies have shown that strong wind speed gradients develop in response to persistent mesoscale sst features associated with the kuroshio extension gulf stream south atlantic and agulhas return current regions midlatitude sst fronts also significantly modify surface wind direction the surface wind speed and direction responses to typical sst differences of about 2 4 c are on average about 1 2 m s 1 and 4

observations of marine atmospheric boundary layer transitions across the summer kuroshio extension abstract the baiu and kuroshio extension ke fronts both zonally oriented and nearly collocated east of japan are the dominant summertime features of the atmosphere and ocean respectively over the midlatitude northwest pacific an atmospheric sounding campaign was conducted on board the r v roger revelle during the 2005 summer transects of soundings across the ke front are analyzed to study its effects on the atmosphere along with continuous surface meteorological and ceilometer cloud base observations while the ke front remained nearly stationary during the cruise the baiu front displayed large meridional displacements that changed wind direction across the ke front the presence of sharp sea surface temperature sst gradients anchored by the ke enhanced the thermal and moisture advection causing substantial changes in the marine atmospheric boundary layer mabl structure when the baiu front was displaced north of the ke front southwesterly winds advected warm humid air from the subtropics

decreasing overflow from the nordic seas into the atlantic ocean through the faroe bank channel since 1950 the overflow of cold dense water from the nordic seas across the greenland scotland ridge and into the atlantic ocean is the main source for the deep water of the north atlantic ocean this flow also helps drive the inflow of warm saline surface water into the nordic seas the faroe bank channel is the deepest path across the ridge and the deep flow through this channel accounts for about one third of the total overflow previous work has demonstrated that the overflow has become warmer and less saline over time here we show using direct measurements and historical hydrographic data that the volume flux of the faroe bank channel overflow has also decreased estimating the volume flux conservatively we find a decrease by at least 20 per cent relative to 1950 if this reduction in deep flow from the nordic seas is not compensated by increased flow from other sources it implies a weakened global thermohaline circulation and reduced inflow of atlantic water to the nordic seas

squeeze box in a centrifuge abstract a squeeze box which operates in a centrifuge is presented in the experimental set up the centrifugal body force mimics the role of gravity in nature and at the same time drives a hydraulic press which simulates lateral forces the rate of lateral shortening is controlled by varying the loads placed on the hydraulic press utilization of a squeeze box in a centrifuge enhances the range of scaling and enables the use of coherent model materials without violating similitude requirements in the traditional squeeze box which operates under normal gravity similitude requirements severely limit the choice of model materials as a test of the apparatus simple experiments were carried out comparing models shortened in a centrifuge with similar models shortened under normal gravity the realistic form of decollement structures e g folds faults and diapirs shortened in a centrifuge in these tests as well as in other tests which will be reported later show the potential of this new technique for rigorous modelling of geodynamic systems which evolve under the influence of both gravity and a push from the rear the set up can also be used as a simple shear box in a centrifuge after a slight adjustment

baiu rainband termination in atmospheric and coupled atmosphere ocean models abstractthe baiu rainband is a summer rainband stretching from eastern china through japan toward the northwestern pacific the climatological termination of the baiu rainband is investigated using the japanese 25 yr reanalysis jra 25 a stand alone atmospheric general circulation model gcm forced with observed sea surface temperature sst and an atmosphere ocean gcm aogcm the baiu rainband over the north pacific abruptly shifts northward and weakens substantially in early july in the atmospheric gcm agcm too early compared to observations late july the midtroposphere westerly jet and its thermal advection explain this meridional shift of the baiu rainband but the ocean surface evaporation modulates the precipitation intensity in agcm deep convection in the subtropical northwestern pacific sets in prematurely displacing the westerly jet northward over the cold ocean surface earlier than in observations the suppressed surface evaporation over the cold ocean suppresses precipitation even

causes and development of repeated arctic ocean warming events 1 a model hindcast for 1948 2002 shows several warming events in the atlantic layer of the arctic ocean the most recent warming event in the 1990s spread from fram strait to the lomonosov ridge and into the canadian basin only a warming event in the 1960s can also be followed into the eastern eurasian basin these two warming events are reinforced by anomalously warm flow from the barents sea while warming events in the 1970s and 1980s encounter average or below normal temperatures in the barents sea branch of the atlantic water the warm barents sea outflow in the 1960s is caused by extensive ice cover and a melt water induced halocline in the barents sea that reduced heat loss from the atlantic water in the 1990s however the warm inflow from the nordic seas was responsible for warmer than normal flow from the barents sea into the arctic ocean

a new path for the denmark strait overflow water from the iceland sea to denmark strait 1 denmark strait overflow water dsow is one of the main components of the thermohaline circulation there has been no consensus on where it is formed and by which way it is brought to the denmark strait it is shown here that it is brought to the sill by a hitherto unknown current that is traced from the sill back into the iceland sea north of iceland the transport of this current is sufficient to account for a major part of the transport of dsow as it has been measured at the sill if some entrainment of ambient water is assumed this supports theories suggesting that the iceland sea is the main source for the dsow and this has consequences for the way in which climate change affects the thermohaline circulation

influence of the kuroshio on mesoscale convective systems in the baiu frontal zone over the east china sea abstracttwo mesoscale convective events in the baiu frontal zone bfz were documented based on intensive atmospheric soundings and oceanic castings in the east china sea during may 2011 in addition to continuous surface meteorological observations satellite products and objective analyses these events occurred while the bfz was nearly stagnant and a mesolow was deepening in the zone near surface southerlies associated with the low level jet transported a warm humid air mass from south of the bfz enhanced evaporation which was mainly attributable to the high sea surface temperature of the kuroshio augmented the moisture content of the air mass and helped maintain a convectively unstable stratification in the lower troposphere around the bfz

large scale dynamics of the meiyu baiu rainband environmental forcing by the westerly jet abstract meiyu baiu is the major rainy season from central china to japan brought by a zonally elongated rainband from june to mid july large scale characteristics and environmental forcing of this important phenomenon are investigated based on a reanalysis dataset the meiyu baiu rainband is accompanied by a trough of sea level pressure horizontal shears and sharp moisture gradients near the surface a westerly jet tilted northward with height and large northeastward moisture transport from the south the analysis here reveals the westerly jet as an important culprit for meiyu baiu along the rainband mean ascending motion corresponds well with a band of warm horizontal temperature advection in the midtroposphere throughout summer this adiabatic induction of upward motion originates from the advection of warm air by the westerlies from the eastern flank of the tibetan plateau the ascending motion both induces convection and is enhanced by the resultant condensational heating the westerly jet anch

climatology and seasonal variability of ocean fronts in the east china yellow and bohai seas from satellite sst data front detection and declouding algorithms developed at the uri have been applied to the 12 year 1985 1996 pathfinder sst data set to produce the first comprehensive objectively derived year round climatology of ocean thermal fronts in the eastern china seas from 24 n to 41 n ten fronts have been distinguished namely kuroshio zhejiang fujian jiangsu shandong peninsula bohai sea seohan bay kyunggi bay western and eastern chejudo south korean coastal front and yangtze bank ring front the fronts are seasonally persistent they emerge and disappear in the same seasons of different years the frontal pattern remains fairly stable from one year to another whereas individual fronts display different modes of seasonal variability

high resolution satellite measurements of the atmospheric boundary layer response to sst variations along the agulhas return current abstract the marine atmospheric boundary layer mabl response to sea surface temperature sst perturbations with wavelengths shorter than 30 longitude by 10 latitude along the agulhas return current arc is described from the first year of sst and cloud liquid water clw measurements from the advanced microwave scanning radiometer amsr on the earth observing system eos aqua satellite and surface wind stress measurements from the quikscat scatterometer amsr measurements of sst at a resolution of 58 km considerably improves upon a previous analysis that used the reynolds sst analyses which underestimate the short scale sst gradient magnitude over the arc region by more than a factor of 5 the amsr sst data thus provide the first quantitatively accurate depiction of the sst induced mabl response along the arc warm cold sst perturbations produce positive negative wind stress magnitude perturbations leading to short scale perturbations in the wind stress curl and divergence fields that are li

generation and stability of a quasi permanent vortex in the lofoten basin abstract in the nordic seas the lofoten basin is a region of high mesoscale activity the generation mechanism and the conditions for the stability of a quasi permanent vortex in the center of the lofoten basin are studied with a high resolution ocean circulation model and altimeter data the vortex and its generation mechanism manifest themselves by a pronounced sea surface height ssh signature and variability which are found to be in agreement with altimeter data the vortex results primarily from anticyclonic eddies shed from the eastern branch of the norwegian atlantic current which propagate southwestward the large scale bottom depression of the lofoten basin plays a crucial role for attracting anticyclones into the trough and for enabling the dynamical stability of the vortex the water mass characteristics of the anticyclone lead to enhanced atmospheric interaction heat loss during wintertime the cold water trapped in the upper part of the vortex preconditions convection in the following wi

experiments on strike slip faulting and block rotation analogue model experiments investigating strike slip faulting in zones of distributed shear deformation show that fault orientations and fault evolution indicate modifications of the stress field with increasing bulk shear strain dextral bulk shear deformation at low strain is accommodated dominantly by synthetic strike slip faults riedel shears at higher strain secondary antithetic and synthetic faults develop mostly between earlier formed major riedel shears closely spaced parallel antithetic faults cross faults delimit domains that rotate about vertical axes with continuing shear deformation rotation of fault bounded domains results in sigmoidal antithetic faults that have a dip slip component and a dip direction that changes along strike there is good agreement between models and natural examples of distributed shear zones where block rotations about vertical axes have been documented

covariations of sea surface temperature and wind over the kuroshio and its extension evidence for ocean to atmosphere feedback abstract satellite microwave measurements are analyzed revealing robust covariability in sea surface temperature sst and wind speed over the kuroshio extension ke east of japan ocean hydrodynamic instabilities cause the ke to meander and result in large sst variations increased reduced wind speeds are found to be associated with warm cold sst anomalies this positive sst wind correlation in ke is confirmed by in situ buoy measurements and is consistent with a vertical shear adjustment mechanism namely an increase in sst reduces the static stability of the near surface atmosphere intensifying the vertical turbulence mixing and bringing fast moving air from aloft to the sea surface south of japan the kuroshio is known to vary between nearshore and offshore paths these paths are very persistent and can last for months to years as the kuroshio shifts its path coherent wind changes are detected from satellite data in particular winds are high south of tokyo when the kuroshio takes the near

global analysis of the pressure adjustment mechanism over sea surface temperature fronts using airs aqua data 1 we investigate the signatures of atmospheric pressure adjustment mechanism for surface wind convergence divergence over major sea surface temperature sst frontal regions using global observations of satellite sounding and scatterometer lower tropospheric air thickness which includes a sea level pressure component modified by air temperature in the marine atmospheric boundary layer is analyzed and the relation between the laplacian of the thickness and wind convergence are examined among four sst frontal regions in mid latitudes correlation between the thickness laplacian and wind convergence is the largest over the gulf stream followed by those for the agulhas return current and for the brazil malvinas current and relatively small but still significant over the kuroshio oyashio extension these correlations strongly suggest that the pressure adjustment mechanism ubiquitously plays an important role in air sea interaction over the global sst frontal regions furthermore air temperatures in the first two regions exhibit sst relating signatures even in the mid troposphere

clay modeling of rift asymmetry and associated structures abstract a clay model is used to simulate the development of half graben of alternating asymmetry in a rift zone the sense of asymmetry is determined by the spatial arrangement and movement pattern of plates below the clay the plates can be thought of as analogous to low angle detachment horizons below rifts the change in half graben asymmetry occurs across a transfer zone marked by a highly faulted anticlinal saddle whose axis is oblique to the rift trend

extensional fault systems in sedimentary basins a review of analogue model studies abstract scaled analogue models have provided graphic new insights into the progressive development of extensional fault systems this paper reviews recent results of an on going analogue modelling programme and compares the structural styles in the models with examples of natural extensional fault systems four fundamental model styles scaled to simulate deformation in brittle sedimentary rocks in the upper 10 km of the crust are reviewed extension above a basal detachment which undergoes stretching over a limited are produces an asymmetric rift graben bounded by planar faults and in which the internal deformation is accommodated by rotational domino faults these experimental results are directly comparable to structures found in intracontinental rifts extension above a basal detechment which undergoes extension under the whole model and which has no constraints at the ends produces domino style fault arrays in the pre rift sequence and listric growth faults in the syn rift sequence these results compare with highly extended rift basins and terranes such as the basin and range province usa extension above a simple listric fault produces a characteristic hangingwall roll over and crestal collapse graben system at high values of extension superposed crestal collapse grabens occur and a fan of listric growth faults is developed these structures bear striking similarities to growth faults in progradational delta systems ramp flat listric extensional fault systems using sand mica models produce a characteristic family of structures with an upper roll over crestal collapse system a ramp syncline and reverse fault fold zone and a lower roll over crestal collapse system an example of a ramp flat fault system from the gulf coast usa is presented as a comparison with the analogue model results preliminary results of three dimensional extensional model experiments are presented to illustrate the complexities in such fault systems in all of the experimental models it is found that the geometry of the underlying detachment system exerts fundamental control on structures produced in the hangingwall the analogue models illustrated in this review provide valid geometric and kinematic templates for the progressive evolution of extensional fault systems in sedimentary basins

observed and modelled stability of overflow across the greenland scotland ridge the continuous flow or overflow of cold dense water from the nordic seas across the greenland scotland ridge and into the atlantic ocean is a substantial contributor to the production of the north atlantic deep water that feeds the lower limb of the atlantic meridional overturning circulation the two main overflow branches pass the denmark strait and the faroe bank channel steffen olsen et al present the results of direct current measurements in the faroe bank channel between 1995 and 2005 combined with ocean general circulation model simulations in contrast to earlier reports that the overflow has weakened in the past 50 years they find that overflow of the faroe bank channel and also the total overflow are in fact stable though the model does show a weakening total atlantic meridional overturning circulation due to changes south of the greenland scotland ridge across the greenland scotland ridge there is a continuous flow of cold dense water termed overflow from the nordic seas to the atlantic ocean1 this is a main contributor to the production of north atlantic deep water2 that feeds the lower limb of the atlantic meridional overturning circulation which has been predicted to weaken as a consequence of climate change3 4 the two main overflow branches pass the denmark strait and the faroe bank channel here we combine results from direct current measurements in the faroe bank channel5 for 1995 2005 with an ensemble hindcast experiment6 for 1948 2005 using an ocean general circulation model for the overlapping period we find a convincing agreement between model simulations and observations on monthly to interannual timescales both observations and model data show no significant trend in volume transport in addition for the whole 1948 2005 period the model indicates no persistent trend in the faroe bank channel overflow or in the total overflow transport in agreement with the few available historical observations deepening isopycnals in the norwegian sea have tended to decrease the pressure difference across the greenland scotland ridge7 but this has been compensated for by the effect of changes in sea level in contrast with earlier studies7 8 we therefore conclude that the faroe bank channel overflow and also the total overflow did not decrease consistently from 1950 to 2005 although the model does show a weakening total atlantic meridional overturning circulation as a result of changes south of the greenland scotland ridge

decadal variability in the outflow from the nordic seas to the deep atlantic ocean the global thermohaline circulation is the oceanic overturning mode which is manifested in the north atlantic ocean as northward flowing surface waters which sink in the nordic greenland iceland and norwegian seas and return southwards after overflowing the greenland scotland ridge as deep water this process has been termed the conveyor belt and is believed to keep europe 5 8 c warmer than it would be if the conveyor were to shut down the variability of today s conveyor belt is therefore an important component of climate regulation the nordic seas are the only northern hemisphere source of deep water and a previous study has revealed no long term variability in the outflow of deep water from the nordic seas to the atlantic ocean here i use flows derived from hydrographic data to show that this outflow has approximately doubled and then returned to previous values over the past four decades i present evidence which suggests that this variability is forced by variability in polar air temperature which in turn may be connected to the recently reported arctic warming

multi scale temporospatial variability of the east asian meiyu baiu fronts characterization with a suite of new objective indices the meiyu baiu front mbf is the primary weather system modulating the monsoonal rainfall in east asia and it exhibits pronounced variability across multiple temporal and spatial scales a suite of new objective indices based upon daily reanalysis data are developed to characterize such variability which include an intensity index effectively measuring the meridional gradient of equivalent potential temperature across the frontal zone a location index documenting the central latitude and longitude of the front and a stationarity index corresponding to the standard deviation of the daily central latitude all these indices are characterized by strong interannual to interdecadal variations specifically the mbf has shown a tendency of southwestward shift since the mid 1990s and become more stationary over southern china with reduced intraseasonal meandering the western north pacific subtropical high wnpsh is the main circulation feature affecting the location of the mbf on interannual timescales the mbf moves northward southward when the wnpsh is anomalously strong weak and the surface high over the region of 35 50 n 100 120 e is anomalously weak strong when the wnpsh is strong the mbf is often situated northwest to its climatological position and becomes more stationary on interdecadal timescales enhanced activity of high latitude blocking over east asia is often accompanied with a stronger but less stationary mbf while a negative phase of the arctic oscillation favors a southward shifted and more stationary mbf

variability of the meridional overturning in the north atlantic from the 50 year gecco state estimation abstract the german partner of the consortium for estimating the circulation and climate of the ocean gecco provided a dynamically consistent estimate of the time varying ocean circulation over the 50 yr period 1952 2001 the gecco synthesis combines most of the data available during the entire estimation period with the ecco massachusetts institute of technology mit ocean circulation model using its adjoint this gecco estimate is analyzed here for the period 1962 2001 with respect to decadal and longer term changes of the meridional overturning circulation moc of the north atlantic a special focus is on the maximum moc values at 25 n over this period the dynamically self consistent synthesis stays within the error bars of h l bryden et al but reveals a general increase of the moc strength the variability on decadal and longer time scales is decomposed into contributions from different processes changes in the model s moc strength are strongly influenced by the southward communication of d

observations of coupling between surface wind stress and sea surface temperature in the eastern tropical pacific satellite measurements of surface wind stress from the quikscat scatterometer and sea surface temperature sst from the tropical rainfall measuring mission microwave imager are analyzed for the three month period 21 july 20 october 1999 to investigate ocean atmosphere coupling in the eastern tropical pacific oceanic tropical instability waves tiws with periods of 20 40 days and wavelengths of 1000 2000 km perturb the sst fronts that bracket both sides of the equatorial cold tongue which is centered near 1 8s to the east of 1308w these perturbations are characterized by cusp shaped features that propagate systematically westward on both sides of the equator the space time structures of these sst perturbations are reproduced with remarkable detail in the surface wind stress field the wind stress divergence is shown to be linearly related to the downwind component of the sst gradient with a response on the south side of the cold tongue that is about twice that on the north side the wind stress curl is linearly related to the crosswind component of the sst gradient with a response that is approximately half that of the wind stress divergence response to the downwind sst gradient the perturbed sst and wind stress fields propagate synchronously westward with the tiws this close coupling between sst and wind stress supports the wallace et al hypothesis that surface winds vary in response to sst modification of atmospheric boundary layer stability