the late quaternary slip rate of the har us nuur fault mongolian altai from cosmogenic 10be and luminescence dating the altai range western mongolia accommodates nne ssw shortening across the northern india eurasia collision zone by dextral slip on faults trending nnw sse and anticlockwise vertical axis rotations of fault bounded blocks however fault slip rates and the way in which faulting evolves over time are poorly understood and form the motivation for this study we focussed on the har us nuur fault a major transpressional fault bounding the eastern margin of the altai three abandoned alluvial fan surfaces each displaced right laterally by the fault were targeted for dating with cosmogenic 10be and quartz optically stimulated luminescence osl the first surface a2 shows an exponential decrease in 10be with increasing depth with a significant inherited component modelling this profile yielded a minimum age of 74 1 ka material from the same sampling pit was dated at 19 ka with osl but we consider this younger age to be incorrect possibly due to feldspar contamination or abnormal quartz osl characteristics the a2 surface is displaced by 175 m implying a maximum dextral slip rate of 2 4 0 4 mm yr 1 a second fan surface f1 was dated at 6 ka with osl and shows little variation in 10be with depth consistent with this young age the inherited component is higher than for a2 indicating contrasting levels of inheritance for different periods of fan aggradation a final surface f2 shows scattered 10be concentrations and lacks material suitable for osl so cannot be dated precisely using the total vertical displacement across the fault we place the initiation of movement on the fault at 2 ma significantly later than the late oligocene to miocene 28 5 ma onset of shortening in the altai region this suggests that deformation in the altai has widened over time to incorporate new faults at the range margins such as har us nuur possibly because older faults in the range interior have rotated about vertical axes into orientations that require work to be done against gravity

sensitivity studies of the red sea eddies using adjoint method the topography data is derived from general bathymetric chart of the oceans gebco https www gebco net the open boundary conditions are extracted from the estimating the circulation and climate of the ocean ecco product https ecco jpl nasa gov products the data supporting the analysis presented here can be found at figshare https figshare com articles data for 2018jc014531r 7243184 the research reported in this manuscript is supported by king abdullah university of science and technology kaust and made use of the resources of the supercomputing laboratory and computer clusters at kaust

optical dating using infrared diodes young samples abstract ages are reported for unburnt sediment samples from 9 archaeological sites in england spanning 1000 5000 years samples from two modern contexts have also been measured

the pacific subsurface countercurrents and an inertial model abstract the tsuchiya jets or subsurface countercurrents extend across the pacific ocean carrying 7 2 106 m3 s 1 eastward on each side of the equator mean meridional sections of potential temperature salinity neutral density anomaly and the square of buoyancy frequency are presented for the western central and eastern tropical pacific ocean these sections are used together with maps of depth and salinity on isopycnals as well as thickness between isopycnals to describe the evolution of the tsuchiya jets as they flow from west to east an inertial jet model is formulated in which conservation of the bernoulli function and potential vorticity combine with the eastward shoaling of the tropical pycnocline to dictate the jet structure this model jet is consistent with a number of features of the tsuchiya jets their roughly constant volume transports their advection of properties such as salinity and oxygen over long zonal distances their rapidity and narrowness their poleward shift from we

morphological dating of cumulative reverse fault scarps examples from the gurvan bogd fault system mongolia morphological dating of cumulative reverse fault scarps

preparing to predict the second autonomous ocean sampling network aosn ii experiment in the monterey bay abstract the autonomous ocean sampling network phase two aosn ii experiment was conducted in and offshore from the monterey bay on the central california coast during july 23 september 6 2003 the objective of the experiment was to learn how to apply new tools technologies and analysis techniques to adaptively sample the coastal ocean in a manner demonstrably superior to traditional methodologies and to use the information gathered to improve predictive skill for quantities of interest to end users the scientific goal was to study the upwelling relaxation cycle near an open coastal bay in an eastern boundary current region particularly as it developed and spread from a coastal headland the suite of observational tools used included a low flying aircraft a fleet of underwater gliders including several under adaptive autonomous control and propeller driven auvs in addition to moorings ships and other more traditional hardware the data were delivered in real time and assimilated into the harvard ocean prediction system hops the navy coastal ocean model ncom and the jet propulsion laboratory implementation of the regional ocean modeling system jpl roms two upwelling events and one relaxation event were sampled during the experiment the upwelling in both cases began when a pool of cold water less than 13 c appeared near cape ano nuevo and subsequently spread offshore and southward across the bay as the equatorward wind stress continued the primary difference between the events was that the first event spread offshore and southward while the second event spread only southward and not offshore the difference is attributed to the position and strength of meanders and eddies of the california current system offshore which blocked or steered the cold upwelled water the space and time scales of the mesoscale variability were much shorter than have been previously observed in deep water eddies offshore additional process studies are needed to elucidate the dynamics of the flow

macroecological patterns of phytoplankton in the northwestern north atlantic ocean st so that pojjjua pojsjajjju there at s s the fluctuations of s contributing to p j have tc s t and can occur at any moment within t the extrapolation formulas at st e are pojjjuao1a j 2 s 2 upojsjajjjaj 2 s u and

the southwest pacific ocean circulation and climate experiment spice the southwest pacific ocean circulation and climate experiment spice is an international research program under the auspices of clivar the key objectives are to understand the southwest pacific ocean circulation and the south pacific convergence zone spcz dynamics as well as their influence on regional and basin scale climate patterns south pacific thermocline waters are transported in the westward flowing south equatorial current sec toward australia and papua new guinea on its way the sec encounters the numerous islands and straits of the southwest pacific and forms boundary currents and jets that eventually redistribute water to the equator and high latitudes the transit in the coral solomon and tasman seas is of great importance to the climate system because changes in either the temperature or the amount of water arriving at the equator have the capability to modulate the el nino southern oscillation while the southward transports influence the climate and biodiversity in the tasman sea after 7 years of substantial in situ oceanic observational and modeling efforts our understanding of the region has much improved we have a refined description of the spcz behavior boundary currents pathways and water mass transformation including the previously undocumented solomon sea the transports are large and vary substantially in a counter intuitive way with asymmetries and gating effects that depend on time scales this paper provides a review of recent advancements and discusses our current knowledge gaps and important emerging research directions

the california current system off monterey california physical and biological coupling repeated hydrobiological surveys over the period 1988 2002 perpendicular to the central california coast indicate strong coupling between physical circulation and biological production an equatorward flowing jet about 100 200 km from shore marked the inshore edge of the california current cc this cc jet had its highest velocities during late winter and spring the jet divided inshore biologicallyproductive waters from offshore low production waters mean flow in the inshore waters is poleward however this flow is interrupted in late spring and summer bya surfaceenhanced equatorward flowing coastal upwelling jet the upwelling jet coincides with maxima of nutrients chlorophyll a and primaryproduction annual variabilityin the inshore zone is related to 1 vertical py cnocline movements associated with geostrophic adjustments to accelerations of the california current system and 2 coastal upwelling in offshore waters the annual cycle accounted for a small fraction of the variability indicating the dominance of eddies and meanders in this zone j geophys res 92 1987 12 947 the offshore regime was mesotrophic to oligotrophic with a subsurface chlorophyll a maximum above the nutricline considerable subduction mayoccur under the california current jet and be an important process in the export of biogenic material to the deep sea published byelsevier ltd

late pleistocene to holocene slip rates for the gurvan bulag thrust fault gobi altay mongolia estimated with 10be dates 1 we surveyed morphotectonic markers along the central part of the gurvan bulag thrust a fault that ruptured with the bogd fault during the gobi altay earthquake 1957 m 8 3 to document climatic and tectonic processes along the fault for the late pleistoceneholocene period the markers were dated using 10 be produced in situ two major periods of alluviation ended at 131 20 and 16 4 8 ka these appear to be contemporaneous with global climatic changes at the terminations of marine isotope stages mis 6 and 2 the vertical slip rates determined from offset measurements and surfaces ages are 0 14 0 03 mm yr over the late pleistocene holocene and between 0 44 0 11 and 1 05 0 25 mm yr since the end of the late pleistocene the higher of these slip rates for the last 16 kyr is consistent with paleoseismic investigations along the fault prentice et al 2002 and suggests that at the end of late pleistocene the fault evolved from quiescence to having recurrence intervals of 4 0 1 2 kyr for surface ruptures with 4 m vertical offset similar to that of 1957 the inferred recurrence interval is comparable to that of the bogd fault 3 7 1 3 kyr suggesting that the two faults may have ruptured together also earlier during the last 16 kyr index terms 7221 seismology paleoseismology 1208 geodesy and gravity crustal movements intraplate 8110 1824 hydrology geomorphology 1625 7230 seismology seismicity and seismotectonics 8107 tectonophysics continental neotectonics keywords late pleistocene holocene thrust fault slip rate 10be dating mongolia

the origin of the pacific equatorial 13 c water abstract examination of the vertical distributions of temperature salinity oxygen and nutrient salts in the thermostad of the equatorial 13 c water in the eastern pacific ocean indicates that local vertical mixing is unimportant in creating the thermostad and the characteristics of the 13 c water maps are presented that show the oceanwide distributions of depth geostrophic flow salinity oxygen phosphate silica and nitrate on the 160 cl t 1 isanosteric surface which nearly coincides with the core of the 13 c water the maps suggest that the original characteristics of the 13 c water are acquired in the surface and thermocline layers to the northeast of new zealand and in the tasman sea by winter convection and vertical mixing the acquired characteristics are advected to the thermostad in the eastern pacific via a long route starting from the source region the flow is first eastward in high latitudes and then returns westward in low latitudes around the anticyclonic subtropical gyre of the sout

late quaternary rates of uplift and shortening at baatar hyarhan mongolian altai with optically stimulated luminescence we investigate mountain building in the altai range of western mongolia focusing on baatar hyarhan a nw trending massif bounded by active thrust faults our primary aims are to describe how thrusting has evolved over time to calculate late quaternary slip rates by dating offset alluvial markers with optically stimulated luminescence osl and to compare these late quaternary rates with measurements of deformation on decadal and geological timescales patterns of topography and drainage suggest that baatar hyarhan has grown in length and has propagated laterally from the se towards the nw over time on the ne side of the massif the range bounding zereg fault appears active only along younger parts of baatar hyarhan next to the oldest se part of the massif faulting has migrated into the adjacent zereg basin where it has uplifted low linear ridges of folded sediment known locally as forebergs on the sw side of the massif only the range bounding tsetseg fault appears active using osl we establish ages of 223c15 223c20 and 223c85 kyr for alluvial deposits cut by these faults these ages are close to those of alluvial markers in the separate gobi altai range suggesting that periods of fan and terrace formation may correlate over wide tracts of mongolia presumably under the primary control of climate combining our osl ages with offsets measured with differential gps we calculate late quaternary slip rates across forebergs in the zereg basin and across the range bounding zereg and tsetseg faults uncertainties in fault dip due to lack of clear fault exposures and burial ages due to incomplete resetting of the luminescence clock mean that the exact slip rates are poorly constrained nevertheless the vertical displacement rates we calculate across the zereg and tsetseg range front faults20140 220130 6 and 0 120130 4 mm yr22121 respectively2014are at the lower end of long term 223c5 myr estimates of 0 420130 8 and 0 320130 7 mm yr22121 respectively vertical rates of deformation may therefore have remained constant over the past 223c5 myr but equally the late quaternary rates might be lower than the geological ones this possible discrepancy could be accounted for if some of the shortening has shifted away from the range front faults onto other nearby structures the forebergs in the eastern zereg basin are an obvious candidate but they show at least 10 km cumulative shortening which would take a few ma to accumulate at late quaternary rates and cannot simply be regarded as the latest stage of outward mountain growth the total late quaternary shortening rate across all three areas of faulting is 0 720132 4 mm yr22121 making up between one tenth and one third of the 223c7 mm yr22121 convergence across the whole altai range

origin of upper ocean warming and el nino change on decadal scales in the tropical pacific ocean the cause of decadal scale variability in the tropical pacific ocean such as that marked by the 1976 77 shift in the el nino southern oscillation1 2 3 4 5 6 7 is poorly understood unravelling the mechanism of the recent decade long warming in the tropical upper ocean is a particularly important challenge given the link to el nino variability but establishing the hypothesized interannual decadal oceanic connections between middle latitudes and tropics has proved elusive8 here we present observational evidence that pacific upper ocean warming and decadal changes in the el nino southern oscillation after 1976 may originate from decadal mid latitude variability in the middle 1970s the north pacific ocean is observed to have undergone a clear phase transition a see saw subsurface temperature anomaly pattern that rotates clockwise around the subtropical gyre at middle latitudes a subsurface warm anomaly formed in the early 1970s from subducted surface waters and penetrated through the subtropics and into the tropics thus perturbing the tropical thermocline and driving the formation of a warm surface water anomaly that may have influenced el nino in the 1980s the identification of this teleconnection of extratropical thermal anomalies to the tropics through a subsurface ocean bridge may enable improved prediction of decadal scale climate variability

the effect of thermal transfer on the zeroing of the luminescence of quartz from recent glaciofluvial sediments abstract the natural optically stimulated luminescence osl response of quartz grains extracted from a range of recent glaciofluvial and other glaciogenic sediments from western greenland is presented all samples were deposited within the last 10 years many only days or hours before collection consequently we would expect to measure zero or very small d e values had optical resetting of the osl signal been complete in the case of most samples d e values in the range 0 5 10 gy are observed while higher values are observed for a handful of samples however the regenerated osl growth curves constructed after daylight exposure of at least several hours also show large apparent d e values negative x axis intercepts corresponding samples from four different locations in the indian himalaya display similar osl characteristics the measurement of several regenerated osl growth curves omitting the preheat procedure which normally precedes osl measurement confirms that a significant degree of thermal transfer is occurring during the preheating it is this thermal transfer of charge during the preheat which is responsible for a significant contribution to the large apparent d e values observed for the regenerated osl growth in this paper we describe combined osl and tl measurements which have been used to monitor the charge transfer in detail for one sample an attempt is made to describe the charge transfer behaviour and we discuss methods appropriate to eliminating the unwanted effects of this phenomenon during osl dating preliminary results from the application of these techniques are presented and the implications of these observations for the osl dating of glaciogenic sediments are discussed

western pacific coastal sources of iron manganese and aluminum to the equatorial undercurrent 1 we present results from the first zonal transect of iron aluminum and manganese conducted from the western source region of the equatorial undercurrent euc to the central equatorial pacific trace metals were elevated along the slope of papua new guinea and within the new guinea coastal undercurrent ngcu which is the primary southern hemisphere entry path of water to the euc subsurface maxima in total acid soluble iron aluminum and manganese were evident in the euc these maxima were generally greatest in the western equatorial pacific and decreased in magnitude eastward maxima in iron and aluminum persisted to 140 w maxima in manganese extended to 175 w iron and manganese maxima were deeper 25 75 m than aluminum maxima and located in the lower euc which undergoes less interior ocean mixing than shallower waters the depth of the aluminum subsurface maxima correlated strongly r 0 88 with the depth of the euc velocity maximum surface waters were enriched in aluminum and manganese offshore of papua new guinea surface metal concentrations decreased eastward throughout the western warm pool up to the longitude 180 w of the salinity front detrital sediment input from either direct riverine input or sediment resuspension appeared to be the primary mechanism of supplying metals to the ngcu we estimated eastward fluxes of metals in the euc and found greatest fluxes in the western equatorial pacific between 160 e and 165 e except for aluminum fluxes of aluminum and to a lesser extent manganese increased concurrently with water volume transport in the central equatorial pacific iron transport in the euc remained constant east of the dateline apparently due to the combined effects of dilution by meridional entrainment and scavenging iron was mobilized in a highly active western boundary current region and transported eastward in the lower euc

morphological dating of cumulative reverse fault scarps examples from the gurvan bogd fault system mongolia summary we relate reverse fault scarp morphology formed by several earthquake dislocations to the average deformation rate using a morphological dating model based on a diffusion analogue of erosion our scarp degradation model includes diffusive erosion during the interseismic period the gravitational collapse of the coseismic fault scarp just after formation and the variation of the surface rupture location interactions between thrusting and geomorphic processes acting on scarp morphology are analysed along the gurvan bogd range in mongolia four main processes acting on scarp morphology were distinguished i gravitational collapse of the frontal scarp resetting the diffusive scarp if fault offsets are big and faulting is localized 2 progressive erosion of the fault scarp during the interseismic period 3 folding associated with the frontal thrust and backthrusts 4 competing alluvial deposition on mountain piedmont slopes and abrasion of the fault scarp by wash processes the growth of cumulative reverse fault scarps is suppressed when they are located in the outwash of major drainage basins they can grow higher in distance from major catchment discharges the modelling suggests that the morphology of the scarp and its apparent degradation stage depend on the parameters controlling the amount of frontal collapse the magnitude of coseismic offsets the dip of the fault near the surface and the step distance between faults folding associated with thrusting creates a convexity on the upper part of the scarp and increases its height the comparison of different scarp profiles suggests that folding leads to an overestimate of the morphological age we estimate a diffusion coefficient at 3 3 1 7 m 2 ka l morphological ages calculated with our model confirm that slip rate along reverse faults of the gurvan bogd range has not been constant over the last 100 ka

ventilated thermocline strongly affected by a deep mixed layer a theory for subtropical countercurrent abstract the mixed layer thickness generally increases in the northward direction but its change seems to occur rather sharply in a narrow transition zone referred to as a mixed layer front here the author investigates the effects of the mixed layer front on the ventilated thermocline structure especially focusing on the generation mechanism of the subtropical countercurrent if the mixed layer front is not parallel to the surface density contour the fluid with minimum isopycnal potential vorticity is formed around the intersection of the mixed layer front and outcrop line if the mixed layer front slants northeastward and surface density is zonally uniform as seen in a numerical experiment carried out by kubokawa and inui in which the subtropical countercurrent was reproduced the minimum potential vorticity on a high density isopycnal occurs in the east while that in a low density isopycnal occurs in the west in the present study analytic solutions for a simple three layer model are presented f

cold halocline in the northern california current an invasion of subarctic water 1 subsurface upper ocean waters off oregon and vancouver island were about 1 c cooler in july 2002 than in july 2001 the anomalously cool layer coincides with the permanent halocline which has salinities of 32 2 to 33 8 suggesting an invasion of nutrient rich subarctic waters the anomalously cool layer lies at 30 150 m the cool anomaly is likely caused by stronger southward flow in the california current and weaker northward flow in the alaska and davidson currents during spring 2002 other factors may include reduced coastal downwelling in late winter and early spring 2002 enhanced eastward flow in the subarctic current and enhanced winter mixing offshore

the penetration of tritium into the tropical pacific abstract the persistence of subsurface tritium maxima coincident with the equatorial currents is used to show that advection along isopycnals by the mean wind driven circulation is the dominant process in the at most 14 year time scale for the penetration of high northern latitude water to the equator above 26 2 sigma theta ventilation of the equatorial pacific thermocline from the north contrasts sharply with the equatorial atlantic thermocline which is ventilated from the south the most striking manifestation of the north pacific circulation is evidenced by a tritium maximum and salinity minimum at the equator between 145 and 125 w located above 25 6 sigma theta it shows that regardless of time of sampling the eastern sol central equator has received the moat high latitude water probably as a consequence of recirculation by the equatorial currents between the same meridians there is a tritium maximum on and north of the equator at the surface which is interpreted as an expression of upwelling

subthermocline and intermediate zonal currents in the tropical pacific ocean paths and vertical structure abstractthe mean subthermocline and intermediate zonal circulation in the tropical pacific is investigated using a compilation of shipboard adcp measurements and absolute geostrophic velocities constructed from a high resolution 0 2000 m argo climatology referenced to a 1000 m velocity field derived from argo float drifts this reference field is dominated by basinwide alternating zonal jets with a meridional wavelength of about 3 in regions where the sampling of sadcp data is sufficient the consistency between the two independent datasets is striking using the argo drift reference is crucial to capture the current structures two apparently distinct systems of alternating westward and eastward zonal jets are seen in both datasets equatorward of 10 a series of low latitude subthermocline currents llscs below the thermocline extending from about 200 to 800 m including the eastward tsuchiya jets and a series of low latitude intermediate currents llics extending from about 700 to at least 2000

generation and initial evolution of a mode water θ s anomaly abstract generation and evolution of an isopycnal potential temperature salinity s or spiciness anomaly is studied around 20 23 s 110 w in the austral winter of 2004 two profiling ctd floats deployed in the region in january 2004 provide the observations the anomaly defined as relative to water properties of the preceding summer is very large initially about 0 35 in s and about 0 9 c in it is associated with the winter ventilation of a thick low potential vorticity layer known as south pacific eastern subtropical mode water regional lateral and s distributions at the surface predispose the ocean to formation of this water mass and allow significant anomalies to be generated there with relative ease the water mass is potentially important for climate in that after northwestward advection in the south equatorial current it contributes to the equatorial undercurrent and eventually resurfaces in the cold tongue of the eastern equatorial pacific ocean the anomaly studied is strong enou

the termination of the equatorial undercurrent in the eastern pacific abstract the termination of the equatorial undercurrent euc in the eastern tropical pacific has been studied through analysis of the historical hydrographic station data in the region bounded by 5 n 10 s 80 w and 100 w three distinctive hydrographic features associated with the euc are used along with dynamic topography to trace the mean path of the euc and to investigate aspects of its seasonal variation these features are 1 the 13 c thermostad 2 the high salinity core and 3 the high dissolved oxygen concentration tongue the thermostad is thickest just south of the equator to the west of the galapagos islands with a decreasing maximum extending southeast to the coast of south america near 7 s the thermostad is poorly developed in the mean near the equator east of the galapagos islands this pattern appears to be produced by convergence of eastward flow in the euc and in the southern subsurface countercurrent as the euc flows southeastward from the galapagos this interpretation is supported by the geostrophic flow calculated from the mean dynamic topography the isolated high salinity core is found to the south of the equator and is traced all the way to the coast of south america the high oxygen tongue associated with the euc splits at the galapagos with the southward projecting branch disappearing rapidly as an identifiable feature the other branch of the tongue continues around the islands to the north and along the equator to the coast of ecuador some evidence of recirculation of euc water in the south equatorial current is seen to the northwest of the galapagos a strong seasonal pulsation of the euc affects these features in a consistent way with the pulse occurring first west of the galapagos and later along the coast the thermostad first reaches maximum development and then a pronounced downwelling of the thermocline occurs rapidly leading to minimum thermostad extent associated wtih this downwelling is an eastward protruding high salinity tongue near the equator which is later seen as an isolated core along the coast at 4 s and 6 s pressure gradients along the equator and the coast inferred from dynamic topography suggest that this pulse is associated with an increase in the flow of the euc and ultimately the peru chile undercurrent the pressure gradient reversal along the equator occurs prior to the annual wind reversal suggesting that remote forcing plays a role in the seasonal pulse of the euc in the eastern pacific

south pacific origin of the decadal enso like variation as simulated by a coupled gcm 1 the hypothesis of the south pacific origin of the decadal 7 35 years enso like variation is investigated based on 200 year outputs of the echam4 opa oasis coupled gcm associated with the decadal warm cold sst anomalies in the tropical pacific an anomalous cyclonic anticyclonic circulation which is tilted in a southeast northwest direction appears in the south pacific this results in anomalous upward downward ekman pumping along the northeastern edge of the anomalous circulation and hence shallowing deepening the oceanic thermocline there such an external source of heat content tends to slowly discharge recharge the tropical ocean on the decadal timescale the above result is consistent with the observational study of luo and yamagata 2001 besides the model reproduces amazingly a high lagged correlation between the global land surface temperature and the decadal nino3 sst despite the model biases this suggests a potential prediction skill of the global warming based on the enso like decadal variation

slip rates along active faults estimated with cosmic ray exposure dates application to the bogd fault gobi altai mongolia dating morphological features displaced along active faults presents a major difficulty in evaluation of slip rates we used in situ produced 10 be to calculate minimum ages for alluvial surfaces misaligned by movement along a major active fault in the gobi altai western mongolia the maximum slip rate of 1 2 mm yr suggested by this method contrasts strongly with rates of 20 mm yr that we estimated by correlation of alluvial deposition with warm humid periods associated with the last glacial termination estimated to have occurred about 12 ka in western tibet the 10 be based slip rate indicates that strong earthquakes can occur along faults with low slip rates and demonstrates the contribution of cosmic ray exposure dating in quaternary tectonic analyses

late cenozoic transpression in southwestern mongolia and the gobi altai tien shan connection the gobi altai region of southwestern mongolia is a natural laboratory for studying processes of active transpressional intracontinental mountain building at different stages of development the region is structurally dominated by several major e w left lateral strike slip fault systems the north gobi altai fault system is a seismically active right stepping left lateral strike slip fault system that can be traced along the surface for over 350 km the eastern two thirds of the fault system ruptured during a major earthquake m 8 3 in 1957 whereas degraded fault scarps cutting alluvial deposits along the western third of the system indicate that this segment did not rupture during the 1957 event but has been active during the quaternary the highest mountains in the gobi altai are restraining bend uplifts along the length of the fault system detailed transects across two of the restraining bends indicate that they have asymmetric flower structure cross sectional geometries with thrust faults rooting into oblique slip and strike slip master faults continued ne directed convergence across the fault system coupled with left lateral strike slip displacements will lead to growth and coalescence of the restraining bends into a continuous sublinear range possibly obscuring the original strike slip fault system this may be a common mountain building process the largely unknown gobi tien shan fault system is a major left lateral strike slip fault system 1200 km long that links the southern ranges of the gobi altai with the barkol tagh and bogda shan of the easternmost tien shan in china active scarps cutting alluvial deposits are visible on satellite imagery along much of its central section indicating quaternary activity the total displacement is unknown but small parallel splays have apparent offsets of 20 km suggesting that the main fault zone has experienced significantly more displacement field investigations conducted at two locations in southwestern mongolia indicate that late cenozoic transpressional uplift is still active along the fault system the spatial relationship between topography and active faults in the barkol tagh and bogda shan strongly suggests that these ranges are large coalescing restraining bends that have accommodated the fault s left lateral motion by thrusting oblique slip displacement and uplift thus from a mongolian perspective the easternmost tien shan formed where it is because it lies at the western termination zone of the gobi tien shan fault system the gobi tien shan fault system is one of the longest fault systems in central asia and together with the north gobi altai and other smaller subparallel fault systems is accommodating the eastward translation of south mongolia relative to the hangay dome and siberia these displacements are interpreted to be due to eastward viscous flow of uppermost mantle material in the topographically low e w trending corridor between the northern edge of the tibetan plateau and the hangay dome presumably in response to the indo eurasian collision 2500 km to the south

remotely sensed surface currents in monterey bay from shore based hf radar coastal ocean dynamics application radar near surface currents in monterey bay derived from a network of shore based hf radars are presented for august december 1994 and compared with those from april to september 1992 focus is placed on the low frequency 2 to 30 day period motions in the remotely sensed data and on comparison of radar derived currents with moored current and wind observations ship based acoustic doppler current profiler observations satellite based surface temperature imagery and surface drifter velocities the radar derived picture of the late summer mean flow is very similar in the two realizations and is consistent with historical data flow is equatorward in the outer part of the bay poleward in a narrow band nearshore and very sluggish in the middle of the bay low pass filtered time series of radar derived currents are highly correlated with moored current observations and with winds in the outer part of the bay the vector time series are also coherent across a broad frequency band with currents typically in phase between 1 and 9 m depths and with 1 m currents typically 40 60 to the right of the wind overall these results confirm the utility of coastal ocean dynamics applications radar codar type hf radars for the study of coastal surface currents out to ranges 50 km from shore particularly for highly averaged fields data variability and comparison with in situ observations for high frequency 1 to 48 hour period motions point to the need to better characterize and minimize sources of error in the radar observations

the annual cycle of circulation of the southwest subtropical pacific analyzed in an ocean gcm abstract an ocean gcm interpreted in light of linear models and sparse observations is used to diagnose the dynamics of the annual cycle of circulation in the western boundary current system of the southwest pacific ocean the simple structure of annual wind stress curl over the south pacific produces a large region of uniformly phased stationary thermocline depth anomalies such that the western subtropical gyre spins up and down during the year directing flow anomalies alternately toward and away from the boundary at its northern end near 10 s the response of the western boundary currents is to redistribute these anomalies northward toward the equator and southward to the subtropical gyre a redistribution that is determined principally by linear rossby processes not boundary dynamics when the subtropical gyre and south equatorial current sec are strong in the second half of the year the result is both increased equatorward transport of the new guinea coastal current and poleward transport a

oceanic isopycnal mixing by coordinate rotation abstract current numerical models of oceanic circulation differentiate between the eddy diffusion and viscosity transport along the geopotential horizontal and vertical directions only in order to model the effect of anisotropic turbulence as diffusive transport along and across density surfaces the isopycnal mixing tensor has been transformed from a diagonal second rank tensor in the isopycnal coordinate system to a tensor containing off diagonal elements in the geopotential coordinate system

water mass analysis of the coral sea through an optimum multiparameter method a water mass analysis of the coral sea thermocline waters provides a description of their distribution pathways and mixture based on recent oceanographic cruises in this region of strong western boundary currents the optimum multiparameter method is used to determine the relative contribution of core water masses based on their measured temperature salinity and dissolved oxygen the thermocline waters carried by the broad south equatorial current sec are essentially composed of four core water masses of different origins coming from the south the south pacific tropical water south sptws 25 3 kg m 3 and the western south pacific central water wspcw 26 3 kg m 3 enter the coral sea by the channel between the island of new caledonia and the vanuatu archipelago coming from the north the south pacific tropical water north sptwn 24 5 kg m 3 and the pacific equatorial water pew 26 3 kg m 3 flow north of vanuatu the upper thermocline water that exits the coral sea equatorward is mainly composed of sptwn carried by the new guinea coastal undercurrent in contrast upper thermocline waters exiting the coral sea poleward in the east australian current is dominated by sptws the relative contributions are different in the lower thermocline where wspcw dominates both western boundary currents this refined description is consistent with the dynamics of the main currents with a very strong depth dependence in the partitioning of incoming sec waters

relic permafrost structures in the gobi of mongolia age and significance relict permafrost structures ice wedge casts and cryoturbation structures are present in the gobi of southern mongolia luminescence dates of sediments are presented to constrain the age of formation of permafrost structures these data show that there was a phase of permafrost development during the latter part of the last glacial after about 22 to 15 ka that resulted in cryoturbated sediments and ice wedge casts furthermore permafrost degradation occurred during late pleistocene times 13 10 ka and was absent during the early holocene these permafrost structures mark the southernmost evidence of permafrost in northern asia during late quaternary times and indicate that the mean annual air temperature was below approximately 6 c during their formation 1998 john wiley sons ltd

timing of formation of forebergs in the northeastern gobi altai mongolia implications for estimating mountain uplift rates and earthquake recurrence intervals bedrock and quaternary alluvial fans in the forelands of the northern gobi altai have been faulted and warped by foreland propagating thrust faults to form elongate hills known as forebergs forebergs near bogd town north of arsta bogd and at ih hetsuu north of baga bogd were mapped and their formation constrained using luminescence dating of lacustrine and fanglomerates sediments to give localized uplift rates of c 0 05 m ka 1 and between c 1 6 and 4 1 m ka 1 respectively comparisons between vertical surface rupture during the 1957 gobi altai earthquake with the age and amount of uplift of lacustrine sediments provide a tentative estimate of between 1288 382 to 497 120 years for the average recurrence interval of great earthquakes in the baga bogd region these localized uplifts rates support the view that the gobi altai mountains probably took between 50 and 25 million years to form and were therefore coeval with the uplift of the himalayas and the tibetan plateau

iron and macronutrients in california coastal upwelling regimes implications for diatom blooms the supply of iron relative to that of the macronutrients nitrate phosphate and silicic acid plays a critical role in allowing extensive diatom blooms to develop in coastal upwelling regimes the presence or absence of a broad continental shelf influences the supply of iron the iron input to central california upwelling waters varies spatially and can be characterized by two end member regimes one end member which includes monterey bay and extending north to pt reyes is an iron replete regime where upwelling occurs over a relatively broad continental shelf that results in waters with high concentrations of dissolved and particulate iron 10 nm entrained together with high concentrations of nitrate and silicic acid in these iron replete regions extensive blooms of large diatoms deplete macronutrient concentrations which results in correspondingly high chlorophyll a concentrations the other end member located to the south of monterey bay off the big sur coast is an iron deplete regime where upwelling is focused offshore of a narrow continental shelf upwelled waters in the big sur region are characterized by low dissolved and particulate iron concentrations 1 nm together with high concentrations of nitrate and silicic acid extremely low iron concentrations unused nitrate and silicic acid and a low abundance of large diatoms characterize surface waters in these iron deplete regions and thus represent coastal upwelling high nutrient low chlorophyll systems limited by the micronutrient iron

1957 gobi altay mongolia earthquake as a prototype for southern california s most devastating earthquake the 1957 gobi altay earthquake was associated with both strike slip and thrust faulting processes similar to those along the san andreas fault and the faults bounding the san gabriel mountains just north of los angeles california clearly a major rupture either on the san andreas fault north of los angeles or on the thrust faults bounding the los angeles basin poses a serious hazard to inhabitants of that area by analogy with the gobi altay earthquake we suggest that simultaneous rupturing of both the san andreas fault and the thrust faults nearer los angeles is a real possibility that amplifies the hazard posed by ruptures on either fault system separately

links between eastern equatorial pacific stratification and atmospheric co2 rise during the last deglaciation it is difficult to untangle the mixed influences of high and low latitude climate forcing in the eastern equatorial pacific eep here we test the hypothesis that the southern ocean drove change in the eep via subsurface intermediate waters during the last deglaciation we use the 18o signature of benthic foraminifera to reconstruct water density changes during the last 25 kyr at three intermediate water depths 370 m 600 m and 1000 m in the eep carbonate 18o records a combined signature of temperature and salinity and is therefore more closely related to density than temperature or salinity alone we find that benthic foraminiferal 18o values decreased first in the subsurface simultaneously with rising temperatures over antarctica and propagated up to the surface within 3 kyr the early subsurface response initiated a rapid decrease in density stratification over the upper water column as indicated by reduced 18o gradients between surface and intermediate depths stratification of the upper water column remained low through the termination with stratification minima reached during heinrich stadial 1 and the younger dryas yd synchronous with the two part deglacial rise in atmospheric co2 centennial scale shifts toward heavier 18o signatures at 370 and 600 m during the yd indicate short lived shifts in the subantarctic mode water antarctic intermediate water boundary to shallower intermediate depths we suggest that decreased density gradients during the deglaciation accelerated vertical mixing across the eep and potentially the entire south pacific subtropical gyre which enhanced co2 delivery from depth to the surface ocean and atmosphere

the obduction of equatorial 13 c water in the pacific identified by a simulated passive tracer the obduction of equatorial 13 degrees c water in the pacific is investigated using a simulated passive tracer of the consortium for estimating the circulation and climate of the ocean ecco the result shows that the 13 degrees c water initialized in the region 8 degrees n 8 degrees s 130 degrees 90 degrees w enters the surface mixed layer in the eastern tropical pacific mainly through upwelling near the equator in the costa rica dome and along the coast of peru approximately two thirds of this obduction occurs within 10 years after the 13 degrees c water being initialized with the upper portion of the water mass reaching the surface mixed layer in only about a month the obduction of the 13 degrees c water helps to maintain a cool sea surface temperature year round equivalent to a surface heat flux of about 6 0 w m 2 averaged over the eastern tropical pacific 15 degrees s 15 degrees n 130 degrees w eastern boundary for the period of integration 1993 2006 during el nino years when the thermocline deepens as a consequence of the easterly wind weakening the obduction of the 13 degrees c water is suppressed and the reduced vertical entrainment generates a warming anomaly of up to 10 w m 2 in the eastern tropical pacific and in particular along the coast of peru providing explanations for the warming of sea surface temperature that cannot be accounted for by local winds alone the situation is reversed during la nina years

horizontal transport and the distribution of nutrients in the coastal transition zone off northern california effects on primary production phytoplankton biomass and species composition conductivity temperature depth surveys during 1988 encountered strong baroclinic jets that were evident in acoustic doppler current profiler and hydrographic data during june and july 1988 a filament with high surface nitrate high chlorophyll abundant populations of neritic centric diatoms and higher rates of primary production was evident perpendicular to the coast between point arena and point reyes however the high nutrient and phytoplankton regions were not in the baroclinic jets but were south and inshore of them surface water transported offshore by the strong baroclinic jets was found to have relatively low nutrient content suggesting that the jets themselves do not carry significant levels of coastally upwelled high nutrient water to the ocean interior the low nutrient and salinity content of the jet suggests that the water originated several hundred kilometers upstream although the jets themselves do not appear to transport significant levels of nutrients directly from the coastal regime to the oceanic regime dynamic processes associated with a meandering jet are likely responsible for high surface nutrients found several hundred kilometers offshore processes such as upwelling along the southern edge of the seaward jet result in significant enrichment of the coastal transition zone and in large blooms of neritic diatoms during 1988 the high nutrient high phytoplankton filament was present when the survey sequence began but then decayed after a month the surface and subsurface nitrate fields were coherent with the dynamic topography field throughout the survey sequence however the surface and integrated chlorophyll fields were coherent only through the first two surveys a decrease in phytoplankton biomass began during the third survey coincident with physical changes which occurred in that time frame 1 an intensification of the undercurrent and 2 changes in the surface circulation from predominantly offshore to predominantly longshore understanding the processes responsible for the uncoupling between biology and physics is paramount for realistic biological models of this region

from the subtropics to the equator in the southwest pacific continental material fluxes quantified using neodymium data along modeled thermocline water pathways the southwestern tropical pacific part of a major pathway for waters feeding the equatorial undercurrent is a region of important geochemical enrichment through land ocean boundary exchange here we develop an original method based on the coupling between dynamical modeling and geochemical tracer data to identify regions of enrichment along the water pathways from the subtropics to the equator and to allow a refined quantification of continental material fluxes neodymium data are interpreted with the help of modeled lagrangian trajectories of an ocean general circulation model we reveal that upper and lower thermocline waters have different pathways together with different geochemical evolutions the upper thermocline waters entering the solomon sea mainly originate from the central subtropical gyre enter the coral sea in the north vanuatu jet and likely receive radiogenic neodymium from the basaltic island margins encountered along their route the lower thermocline waters entering the solomon sea mainly originate from northeast of new zealand and enter the coral sea in the north caledonian jet depletion of their neodymium content likely occurs when flowing along the australian and papua coasts downstream from the solomon sea waters flowing along the papua new guinea margins near the sepik river mouth become surprisingly depleted in their neodymium content in the upper thermocline while enriched in the lower thermocline this coupled approach is proposed as strong support to interpret the origin of the equatorial pacific natural fertilization through a better understanding of the circulation important objectives of the international geotraces and spice programs respectively

the subtropical mode waters of the south pacific ocean abstract the subtropical mode waters stmw of the southwestern pacific ocean are described including their physical characteristics spatial distribution and temporal variability stmw is a thermostad or minimum in stratification having temperatures of about 15 19 c and vertical temperature gradient less than about 2 c per 100 m typical salinity is 35 5 psu at 16 5 c the stmw layer is formed by deep mixing and cooling in the eastward flowing waters of the separated east australia current surface mixed layers are observed as deep as 300 m north of new zealand in winter in the center of a recurring anticyclonic eddy the stmw thermostad in the south pacific is considerably weaker than its counterparts in the north atlantic and north pacific a contrast that may help to discriminate between physical processes contributing to its formation a quarterly time series of expendable bathythermograph transects between new zealand and fiji is used to study the temporal variability of stmw large fluctuatio

alternating influence of northern versus southern sourced water masses on the equatorial pacific subthermocline during the past 240 ka the eastern equatorial pacific eep is a key area to understand past oceanic processes that control atmospheric co2 concentrations many studies argue for higher nutrient concentrations by enhanced nutrient transfer via southern ocean intermediate water soiw to the low latitude pacific during glacials recent studies however argue against soiw as the primary nutrient source at least during early marine isotope stage 2 mis 2 as proxy data indicate that nutrients are better utilized in the southern ocean under glacial conditions new results from the subarctic pacific suggest that enhanced convection of nutrient rich glacial north pacific intermediate water gnpiw contributes to changes in nutrient concentrations in equatorial subthermocline water masses during mis 2 however the interplay between soiw versus gnpiw and its influence on the nutrient distribution in the eep spanning more than one glacial cycle are still not understood we present a carbon isotope 13c record of subthermocline waters derived from deep dwelling planktonic foraminifera globorotaloides hexagonus in the eep which is compared with published 13c records around the pacific results indicate enhanced influence of gnpiw during mis 6 and mis 2 compared to today with largest contributions of northern sourced intermediate waters during glacial maxima these observations suggest a mechanistic link between relative contributions of northern and southern intermediate waters and past eep nutrient concentrations a switch from increased gnpiw decreased soiw to diminished gnpiw enhanced soiw influence on equatorial subthermocline waters is recognized during glacial terminations and marks changes to modern like conditions in nutrient concentrations and biological productivity in the eep

direct measurements of upper ocean currents and water properties across the tropical pacific during the 1990s abstract meridional sections of upper ocean zonal currents potential temperature and salinity are estimated at ten longitudes from 143 e to 95 w using conductivity temperature depth and acoustic doppler current profiler data from 172 synoptic sections taken in the tropical pacific between 138 e and 86 w mostly in the 1990s data reduction is carried out in a potential isopycnal and mixed layer framework to preserve a sharp pycnocline a mixed layer water property extrema and velocity extrema mean zonal currents potential temperatures and salinities are produced at each longitude the seasonal cycles of these fields are also estimated as well as a simple el nino southern oscillation enso cycle zonal sections along the equator are also presented properties of the near equatorial zonal currents including transports temperatures and salinities are estimated separately from the synoptic sections the seasonal cycles of these quantities and their correlations with the southern oscillation index are investigated the work is distinguished from most existing literature in that direct estimates of zonal velocity are combined with contemporaneous temperature and salinity data allowing trans pacific estimates of near equatorial current transports and properties including those of the northern branch of the south equatorial current the new guinea coastal undercurrent and the equatorial undercurrent

from the subtropics to the central equatorial pacific ocean neodymium isotopic composition and rare earth element concentration variations 1 neodymium isotopic compositions end and rare earth element ree concentrations were measured for filtered surface to deep waters 112 samples in the southern tropical pacific the relatively detailed picture of these tracer distributions allowed us to refine the areas where oceanic end variations occur end values increase for most of the water masses flowing from samoa to the solomon sea and in the papua new guinea png area as already observed furthermore water masses arriving from the eastern equatorial pacific 200 550 m depth also revealed radiogenic values possibly acquired in the vicinity of the south american coasts and galapagos islands these end variations affect the whole water column the most likely process causing such variations is boundary exchange between the numerous radiogenic slopes margins located in this area and seawater flowing past dissolution of atmospheric deposition and or diffuse streaming of volcanic ash are also suggested to explain the radiogenic end observed at the surface in the png area interestingly a positive europium eu anomaly characterizes the normalized ree patterns of most of the studied water masses this anomaly is consistent with the ree patterns of sediment and rock samples that are potential sources for the local waters such consistency reinforces the hypothesis that lithogenic sources play a major role in the oceanic ree budget thanks to boundary exchange the data set presented here is a good basis for further sampling that will be realized in the framework of the ongoing geotraces program www geotraces org

investigating bomb radiocarbon transport in the southern pacific ocean with otolith radiocarbon abstract to explore the transport of carbon into water masses from the surface ocean to depths of 1000 m in the southwest pacific ocean we generated time series of radiocarbon c 14 from fish otoliths otoliths carbonate earstones from long lived fish provide an indirect method to examine the bomb pulse of radiocarbon that originated in the 1950s and 1960s allowing identification of changes to distributions of 14c that has entered and mixed within the ocean we micro sampled ocean perch helicolenus barathri otoliths collected at 400 500 m in the tasman sea to obtain measurements of c 14 for those depths we compared our ocean perch c 14 series to published otolith based marine surface water c 14 values australasian snapper chrysophrys auratus and nannygai centroberyx affinis and to published deep water values 800 1000 m orange roughy hoplostethus atlanticus from the southwest pacific to establish a mid water c 14 series the otolith bomb 14c results from these different depths were consistent with previous water mass results in the upper 1500 m of the southwest pacific ocean e g world ocean circulation experiment and geochemical ocean sections study a comparison between the initial c 14 bomb pulse rise at 400 500 m suggested a ventilation lag of 5 to 10 yr whereas a comparison of the surface and depths of 800 1000 m detailed a 10 to 20 yr lag in the time history of radiocarbon invasion at this depth pre bomb reservoir ages derived from otolith 14c located in tasman sea thermocline waters were 530 yr while reservoir ages estimated for tasman antarctic intermediate water were 730 yr

water mass bio optical properties in the monterey bay region fluorescence based inference of shifts in phytoplankton photophysiology 1 a physical and bio optical field survey of the monterey bay area was conducted during may june 2008 the combined bio optical and physical data may be summarized as a transition between two end member states during the late spring to summer upwelling season 1 the mesotrophic nanoflagellate dominated low salinity surface waters chlorophyll a 0 5 2 mg m 3 s 2 mg m 3 s 33 8 of monterey bay and adjacent continental shelf areas high resolution and collocated spectrophotometric fluorometric and ctd data obtained from a towed platform indicated low salinity subarctic origin surface waters intruded into monterey bay on 4 june the dark in vivo fluorometry ivf phytoplankton response normalized to particle absorption at 676 nm the apparent fluorescence efficiency afe was nearly fourfold larger in this water mass type compared to higher salinity surface waters more typical of monterey bay the collocated fluorescence and optical data were then used to estimate in situ irradiance values and determine apparent light saturation intensities i k based on the remarkably consistent afe water column inflection points i kvalues retrieved from the low salinity surface waters were approximately half those obtained over the continental shelf an analysis of concomitant hplc data in addition to historical data for the region suggest these observed fluorescence trends may be indicative of taxon specific variation in photophysiology specifically the subarctic water mass associated pelagic nanoflagellate group likely possesses a fundamentally different photosynthetic architecture than large diatoms prototypical of coastal upwelling regimes

ice wedges growth thaw transformation and palaeoenvironmental significance frost cracking and ice wedge growth are fundamental processes within the permafrost environment extensive areas of contemporary permafrost terrain are characterised by frost fissure polygons formed by repeated thermal contraction cracking of the ground the incremental growth of ice veins and wedges along the axes of contraction cracks contributes significantly to the volume of ground ice in near surface permafrost in areas beyond the present limit of permafrost the recognition of ice wedge pseudomorphs provides one of the few unambiguous indications of the former existence of permafrost conditions an understanding of the processes of ice wedge growth and thaw transformation is essential if contemporary ice wedges are to be used as analogues for pleistocene frost fissure structures in palaeoenvironmental reconstructions

dissolved rare earth elements distribution in the solomon sea abstract trace elements and isotopes teis were measured as part of the geotraces pandora cruise july august 2012 r v l atalante among them rare earth elements rees as pertinent tracers of land ocean inputs and water mass transformations this work discusses results of 19 dissolved ree dree profiles measured using a trispike method in the coral sea and inside and at the exits of the solomon sea a semi enclosed sea with complex topography and straits overall drees except the insoluble ce show nutrient like profiles i e depleted at the surface and enriched at depth illustrative nd concentrations range from 5 pmol kg at the surface to 25 pmol kg at 5000 m depth however local dree enrichments are observed mostly in the straits indispensable solomon and vitiaz straits and along the island coasts a box model allows calculating and discussing the fate of the drees in the different water layers flowing through the solomon sea finally subtle variations revealed by la ce eu anomalies and the normalized light versus heavy ree ratio expressed as ndn ybn allows the identification of specific mechanisms affecting the distribution of the different drees the positive eu anomaly observed in the surface layers reflects the basaltic origin of external inputs consistent with the intensive weathering and or volcanic activity affecting the surrounding islands these data also confirm that the distributions of heavy drees like yb are better correlated to the dsi concentrations than that of the other rees this article is part of a special issue entitled cycles of trace elements and isotopes in the ocean geotraces and beyond edited by tim m conway tristan horner yves plancherel and aridane g gonzalez

long term earthquake clustering a 50 000 year paleoseismic record in the dead sea graben the temporal distribution of earthquakes in the dead sea graben is studied through a 50 000 year paleoseismic record recovered in laminated sediments of the late pleistocene lake lisan paleo dead sea the lisan represents more than 10 times the 4000 years of historical earthquake records it is the longest and most complete paleoseismic record along the dead sea transform and possibly the longest continuous record on earth it includes unique exposures of seismite beds earthquake induced structures associated with slip events on syndepositional faults the seismites are layers consisting of mixtures of fragmented and pulverized laminae the places where the seismites abut syndepositional faults are interpreted as evidence for their formation at the sediment water interface during slip events on these faults thicker sediment accumulation above the seismites in the downthrown blocks indicates that a seismite formed at the water sediment interface on both sides of the fault scarps modern analogs and the association with surface ruptures suggest that each seismite formed during a m l 5 5 earthquake the 230 th 234 u ages of a columnar section obtained by thermal ionization mass spectrometry give a mean recurrence time of 1600 years of m l 5 5 earthquakes in the dead sea graben the earthquakes cluster in 10 000 year periods separated by quiet periods of similar length this distribution implies that a long term behavior of the dead sea transform should be represented by a mean recurrence of at least 20 000 year record this observation has ramifications for seismic hazard assessment based on shorter records

geomorphological investigations and luminescence dating in the southern part of the khangay and the valley of the gobi lakes central mongolia geomorphological investigations in the catchment area of the baydragiyn river along the southern slope of the khangay and in the valley of the gobi lakes in western mongolia provide evidence for late quaternary glaciations and lake level changes thermoluminescence tl and infrared optically stimulated luminescence irsl dating of aeolian and colluvial sediments from the central khangay place the sediments that overlie fluvial and glaciofluvial terraces in the holocene an age of 21 ka is determined for a sand deposit overlying the terrace that is related to the last glacial ice margin lacustrine sediments from higher beach lines in the valley of the gobi lakes provide evidence for a slightly more humid period around 1 5 ka and a larger extent of the lakes in the early holocene at about 8 5 ka as also reported from other parts of central asia remnants of lacustrine sediments buried by alluvial gravel and indicating a huge palaeolake in the basin of the orog nuur however date to the early stage of the last glaciation around 70 ka copyright 2001 john wiley sons ltd

isopycnal mixing in ocean circulation models abstract a subgrid scale form for mesoscale eddy mixing on isopycnal surfaces is proposed for use in non eddy resolving ocean circulation models the mixing is applied in isopycnal coordinates to isopycnal layer thickness or inverse density gradient as well as to passive scalars temperature and salinity the transformation of these mixing forms to physical coordinates is also presented

origin and pathway of equatorial 13 c water in the pacific identified by a simulated passive tracer and its adjoint abstract the origin and pathway of the thermostad water in the eastern equatorial pacific ocean often referred to as the equatorial 13 c water are investigated using a simulated passive tracer and its adjoint based on circulation estimates of a global general circulation model results demonstrate that the source region of the 13 c water lies well outside the tropics in the south pacific some 13 c water is formed northeast of new zealand confirming an earlier hypothesis on the water s origin the south pacific origin of the 13 c water is also related to the formation of the eastern subtropical mode water estmw and the sub antarctic mode water samw the portion of the estmw and samw that eventually enters the density range of the 13 c water 25 8 26 6 kg m 3 does so largely by mixing water formed in the subtropics enters the equatorial region predominantly through the western boundary while its interior transport is relatively small the fresher north pacific estmw and central mode wate

iron sources and dissolved particulate interactions in the seawater of the western equatorial pacific iron isotope perspectives this work presents iron isotope data in the western equatorial pacific marine aerosols and top core margin sediments display a slightly heavy fe isotopic composition 56 fe of 0 33 0 11 2sd and 0 14 0 07 respectively samples reflecting the influence of papua new guinea runoff sepik river and rabaul volcano water are characterized by crustal values in seawater fe is mainly supplied in the particulate form and is found with a 56 fe between a0 49 and 0 34 0 07 the particulate fe seems to be brought mainly by runoff and transported across continental shelves and slopes aerosols are suspected to enrich the surface vitiaz strait waters while hydrothermal activity likely enriched new ireland waters dissolved fe isotopic ratios are found between a0 03 and 0 53 0 07 they are almost systematically heavier than the corresponding particulate fe and the difference between the signature of both phases is similar for most samples with 56 fe dfe pfe 0 27 0 25 2sd this is interpreted as an equilibrium isotopic fractionation revealing exchange fluxes between both phases the dissolved phase being heavier than the particles suggests that the exchanges result in a net nonreductive release of dissolved fe this process seems to be locally significantly more intense than fe reductive dissolution documented along reducing margins it may therefore constitute a very significant iron source to the ocean thereby influencing the actual estimation of the iron residence time and sinks the underlying processes could also apply to other elements

southern ocean contributions to the eastern equatorial pacific heat content during the holocene abstract temperature reconstructions from a shallow core 375 m from the peru margin are used to test the influence of subantarctic mode water samw on the eastern equatorial pacific eep thermostad and thus the effect of southern high latitude climate on interior ocean heat content ohc temperature estimates based on mg ca measurements of planktonic and benthic foraminifera neogloboquadrina dutertrei and uvigerina spp respectively show higher temperatures in the early holocene a cooling of 2 by 8 kyr b p and after relatively stable temperatures to the present the temperature signal is similar in direction and timing to a rather robust holocene climate signal from the southern high latitudes suggesting it originated there and was advected to the core site in the eep based on the n dutertrei and uvigerina mg ca temperature and 13c records we conclude that samw acted as a conduit transporting the southern high latitude climate to the interior of the equatorial pacific we propose that the early holocene warmth is related to a southward migration of the subtropical front which enhanced the influence of warm subtropical water in the region of samw formation and was then transported to the eep thermostad the early holocene warmth recorded in the eep thermostad has a muted sea surface temperature expression indicating this mechanism is important for sequestering heat in the ocean interior

sources and processes affecting the distribution of dissolved nd isotopes and concentrations in the west pacific abstract in the atlantic where deep circulation is vigorous the dissolved neodymium nd isotopic composition expressed as nd is largely controlled by water mass mixing in contrast the factors influencing the nd distribution in the pacific marked by sluggish circulation is not clear yet indication for regional overprints in the pacific is given based on its bordering volcanic islands our study aims to clarify the impact and relative importance of different nd sources rivers volcanic islands vertical bio geochemical processes and lateral water mass transport in controlling dissolved nd and nd concentration nd distributions in the west pacific between south korea and fiji we find indication for unradiogenic continental input from south korean and chinese rivers to the east china sea in the tropical west pacific volcanic islands supply nd to surface and subsurface waters and modify their nd to radiogenic values of up to 0 7 these radiogenic signatures allow detailed tracing of currents flowing to the east and differentiation from westward currents with open ocean pacific nd composition in the complex tropical pacific zonal current system modified radiogenic nd of west pacific intermediate to bottom waters upstream or within our section also indicates non conservative behavior of nd due to boundary exchange at volcanic island margins submarine ridges and with hydrothermal particles only subsurface to deep waters 3000 m in the open northwest pacific show conservative behavior of nd in contrast we find a striking correlation of extremely low down to 2 77 pmol kg nd and laterally constant nd with the high salinity north and south pacific tropical water indicating lateral transport of preformed nd from the north and south pacific subtropical gyres into the study area this observation also explains the previously observed low subsurface nd in the tropical west pacific similarly western south pacific central water antarctic intermediate water and lower circumpolar deep water in the southern and equatorial west pacific are marked by vertically and laterally almost invariant nd indicating a dominance of conservative behavior of nd in contrast central and intermediate water in the north west pacific are characterized by increasing nd with depth reflecting nd release from particles overall our data demonstrate a dominant lateral transport control on nd distributions and clear non conservative modification of nd in the west pacific the latter affords tracing of surface and subsurface zonal transport in the tropical pacific but prevents the use of nd as strictly conservative tracer of the major meridionally circulating water masses in the west pacific between 15 s and 28 n

horizontal surface slip distribution through several seismic cycles the eastern bogd fault gobi altai mongolia abstract the 1957 mw 8 1 gobi altai earthquake southern mongolia produced a 360 km long surface rupture along the eastern bogd fault cumulative offsets of geomorphic features suggest that the eastern bogd fault might produce characteristic slip over the last seismic cycles using orthophotographs derived from a dataset of historical aerial photographs acquired in 1958 we measured horizontal offsets along two thirds 170 km of the 1957 left lateral strike slip surface rupture we propose a new empirical methodology to extract the average slip for each past earthquake that could be recognized along successive fault segments to determine the slip distribution associated with successive past earthquakes our results suggest that the horizontal slip distribution of the 1957 gobi altai earthquake is fairly flat with an average offset of 3 5 m 1 3 m a combination of our lateral measurements with vertical displacements derived from the literature allows us to re assess the magnitude of the gobi altai earthquake to be between mw 7 8 and mw 8 2 depending on the depth of the rupture and related value of the shear modulus when comparing this magnitude to magnitudes derived from seismic data it suggests that the rupture may have extended deeper than the 15 km to 20 km usually considered for the seismogenic crust we observe that some fault segments are more likely than others to record seismic deformation through several seismic cycles depending on the local rupture complexity and geomorphology additionally our results allow us to model the horizontal slip function for the 1957 gobi altai earthquake and for three previous paleoseismic events along 70 of the studied area along about 50 of the fault sections where we could recognize three past earthquakes our results suggest that the slip per event was similar for each earthquake

aspects of late quaternary geomorphological development in the khangai mountains and the gobi altai mountains mongolia abstract the reconstruction of geomorphological processes as a result of environmental change is approached by investigating and dating some fluvial aeolian and lacustrine archives at specific locations that form a n s basin and range transect across the khangai mountains south to the eastern gobi altai mountains in mongolia geomorphological processes varied a spatially with different climatic conditions and vegetation cover in relation to different elevation and latitude and b temporally due to climatic shifts during the late quaternary in total 15 sections from three distinct sub regions along that transect were dated by 22 osl ages the khangai mountain sub region exhibits mainly late glacial to holocene aeolian silty to sandy cover sediments mainly in the upper catchment reaches 1800 m a s l sections in the northern and central gobi represent river terraces and alluvial fans in basin areas as well as aeolian sediments in the mountains above 2200 m a s l the oldest terrace surface found in this study t2 nga1 dates to the penultimate glacial cycle the t1 terrace surfaces on the northern khangai mountain front and in the central gobi sub region yield a maximum accumulation during the global last glacial maximum glgm and late glacial time during the glgm phase represents rather sheetflow dominated transport built the alluvial fans and in late glacial times the sediments exhibit more debrisflow controlled accumulation incision forming the t1 terrace edges is therefore supposed for the pleistocene holocene transition and subsequent early holocene the geomorphic evidence is interpreted as stronger fluvial morphodynamics induced by enhanced humidity under beginning interglacial conditions these processes coincided with the development of aeolian mantles at higher altitudes in the khangai and gobi altai mountains where higher temperatures and humidities supported the formation of a vegetation cover that served as a dust trap at least since late glacial times and reduced the sediment supply on the alluvial fans

dating past earthquakes and related sediments by thermoluminescence methods a review abstract applications of luminescence dating of geological materials have undergone extensive development and refinement since 1986 when mccalpin first attempted to date faults using thermoluminescence tl today luminescence methods offer high potential for dating paleoearthquakes and coseismic and post seismic deformation features over timescales ranging from 102 to 106 a while luminescence approaches generally do not possess the precision obtained by for example 40ar 39ar and 14c methods they offer a useful alternative approach with advantages in terms of age range and scope of material although the application of luminescence dating has in some cases been successfully described a comprehensive study outlining and defining protocols for routine luminescence methods to paleoseismology and neotectonic studies has not been forthcoming this review surveys previous attempts to apply tl techniques to paleoseismology and determination of the age of sediments associated with seismic events however while the use of tl has been a great success the wide application of tl has been hampered by the problem of daylight signal resetting

late cretaceous palaeogene topography of the chinese tian shan new insights from geomorphology and sedimentology abstract the cenozoic growth of the intra continental tian shan range initiated during the late eocene oligocene and led to a tectonic reactivation of the complex palaeozoic and mesozoic lithospheric structure due to the very low erosion rates linked to the semi arid climate that characterised the tian shan region during most of the cenozoic the topography of the range is not at equilibrium with deformation fragments of pre orogenic low relief surfaces are preserved among the late cenozoic alpine type topography using field observations and satellite image mapping of those fragments as well as sedimentology and biostratigraphic analysis we show that the pre oligocene topography of the tian shan region was indeed complex combining hundreds of metres to one and a half kilometre high reliefs with a multi phased mesozoic planation surface incised by late mesozoic paleo valleys the occurrence of several metres thick late cretaceous palaeogene calcareous paleosols in the basins surrounding the range further implies a semi arid climate very low subsidence rates and no uplift at that time late cretaceous and early miocene fossil records in the northern tian shan suggest a possible connection even if episodic between the drainage system of the south junggar foreland basin and the proto paratethys sea to the west a renewed late eocene early oligocene sedimentation probably marks the onset of the tian shan uplift we argue that in addition to the growth of the pamir and western kunlun ranges this incipient uplift was one of the driving mechanisms for the final retreat of the proto paratethys sea from the tarim basin this regression apparently did not change the climate in the studied area because semi arid conditions seem to prevail at least since the late cretaceous finally the tian shan uplift remained very limited up to the miocene as revealed by the occurrence of burdigalian lake deposits preserved in the paleo valleys inside the present day range in contrast post early miocene deformation of the northern tian shan has produced 4000 to 5000 m of differential vertical movement between the uplifted range and the subsiding proximal foreland basin

late winter generation of spiciness on subducted isopycnals the origins of density compensating anomalies of temperature and salinity spice are investigated using a model forced with the most realistic surface products available over the 40 years 1958 97 in this hindcast the largest interannual spiciness anomalies are found in the pacific ocean near the isopycnal s 0 5 25 5 where deviations as great as 1 28c and 0 6 psu are generated equatorward of winter outcropping in the eastern subtropics in both hemispheres these source regions are characterized by very unstable salinity gradients and low mean density stratification in winter two related signatures of winter mixing in the southeast pacific sep are density that is well mixed deeper than either temperature or salinity and subsurface density ratios that approach 1 all ocean basins in the model are shown to have regions with these characteristics and signatures however the resultant spiciness signals are focused on different isopycnals ranging from s 0 5 25 0 in the northeast pacific to s 0 5 26 5 in the south indian ocean a detailed examination of the sep finds that large positive anomalies are generated by diapycnal mixing across subducted isopycnals e g s 0 5 25 5 whereas negative anomalies are the result of a steady isopycnal advection moderated by vertical advection and heave there is considerable interannual variability in the strength of anomalies and in the density on which they occur historical observations are consistent with the model results but are insufficient to verify all aspects of the hindcast including the processes of anomaly generation in the sep it was not possible to relate isopycnal anomaly genesis to local surface forcing of any kind a complex scenario involving basinwide circulation of both the ocean and atmosphere especially of surface water through the subtropical evaporation zones is put forward to explain the decadal time scale evident in sep salinity anomalies on s 0 5 25 5 pacific anomalies generated on s 0 5 25 5 can be traced along mean geostrophic streamlines to the western boundary where decadal salinity variations at 78s are about 2 times as large order 60 1 psu as at 128n although there may be more variance on shallower isopycnals in the north at least portions of the s 0 5 25 5 signals appear to continue along the boundary to a convergence at the equator suggesting that the most robust sources of pacific spiciness variance coincide with equatorial exchange pathways

south pacific eastern subtropical mode water abstract the structure formation and destruction of south pacific eastern subtropical mode water spestmw are analyzed geographic extent and water properties are discussed by using high quality ctd sections collected between 1991 and 1996 defined as having a planetary potential vorticity magnitude of less than 3 10 10 m 1 s 1 spesmtw has a volume of about 1 1 1015 m3 estimated from ctd data the ventilation of this mode water is described by using data from a high resolution xbt section in concert with 30 month time series from profiling ctd floats some of the first argo deployments published subduction rates allow a mode water formation rate estimate of 8 7 106 m3 s 1 combining this estimate with the volume yields a residence time of about 4 years the density compensating covarying patterns of late winter surface temperature and salinity in the ventilation region of spestmw are shown to contribute to the strength of the mode water however while the destabilizing salinity gradient in sp

the subarctic and northern subtropical fronts in the eastern north pacific ocean in spring abstract the subarctic and subtropical frontal zones of the eastern north pacific ocean were surveyed in june for five consecutive years starting in 1972 these surveys from the basis for a description of the complex frontal distributions and their year to year differences the fronts appear as surface outcroppings of haloclines the subarctic halocline where salinity increases with depth and the subtropical halocline where the opposite prevails between the fronts lies a transition zone where strong vertical gradients of salinity are generally absent an examination of the northern boundary of subtropical waters in this new dataset reveals the presence of two major fronts in the subtropical frontal zone in addition to the front commonly identified as the subtropical front 18 c and 34 8 is a northern subtropical front that forms the northern boundary of the subtropical halocline in the eastern north pacific it falls some 2 to 3 of latitude north of the subtropical front and is the same front observ

control of decadal and bidecadal climate variability in the tropical pacific by the off equatorial south pacific ocean abstractdelayed negative feedback processes determining intrinsic decadal and bidecadal time scales for the tropical variability in the pacific are investigated based on climate model experiments by comparing a control run driven by preindustrial forcing and partial blocking runs driven by the same forcing but with ocean temperature and salinity restored to climatology in selected regions subsurface oceanic signals of south pacific origin are shown to precede sst variability in the nino 3 4 region using a linear reduced gravity ocean model driven only by wind stress changes and an offline tracer model oceanic wave adjustment triggered by changes of wind stress curl in the south pacific extratropics is suggested to be essential for the decadal component of the equatorial sst while slower isopycnal advection of subsurface temperature anomalies from the formation region of south pacific eastern subtropical mode water controls the bidecadal component the intrinsic time scales of the tropical variability

subtropical mode water in the northeast pacific basin a new type of mode water in the upper thermocline of the eastern subtropical north pacific is identified and examined using data from world ocean circulation experiment high resolution repeat expendable bathythermograph xbt section px37 and archives of historical xbt data this water mass labeled eastern subtropical mode water is characterized by a subsurface potential vorticity minimum and is located east of hawaii northeast pacific basin in a density range of 24 25 4 it is a distinct water mass from the classical subtropical mode water stmw of the western pacific eastern stmw is formed as a relatively deep late winter mixed layer associated with the subtropical subpolar water mass boundary near 25 30 n 135 140 w and is capped and subducted into the permanent thermocline along a section between san francisco and honolulu eastern stmw production is seen in every year for which there is adequate data in this section the volume of eastern stmw formed each winter and the temperature of the potential vorticity minimum are similar during the periods 1970 1979 and 1991 1997

methodological considerations in the optical dating of quartz abstract the optically stimulated luminescence from quartz grains extracted from sediments at two archaeological sites has been studied the sites were the upper palaeolithic site at hengistbury head dorset u k and the upper aterian site at chaperon rouge morocco problems associated with the technique of optical dating are discussed particularly the thermal treatment that is necessary to remove thermally unstable charge following artificial irradiation and the extrapolation of growth curves to estimate the equivalent dose the technique used is described and some preliminary dates are presented

poleward flow off central california during the spring and summer of 1981 and 1984 currents and winds measured over the continental shelf and upper continental slope during the first half of 1984 are analyzed to determine the character of the flow off central california point conception to san francisco the mean flow was poleward from point conception to point sur in opposition to the equatorward wind stress the mean flow was equatorward north of point sur fluctuations in alongshore currents over the shelf were highly correlated with local winds everywhere except off point conception where currents were not only uncorrelated with wind but also poorly correlated with currents farther north north of point buchon there is evidence for poleward propagation of shelf current variability at 175 200 cm s the correlation between currents and local wind forcing dropped considerably beyond the shelf break only 10 15 km offshore from the shelf moorings during extended periods of weak equatorward winds the poleward shelf flow south of point sur spreads farther offshore over the continental slope a three week period of calm winds in july 1984 resulted in a 100 km wide tongue of poleward flow extending 300 km along the california coast similar but somewhat weaker poleward surface flow occurred during the same period in 1981 a 2 to 3 week period of calm winds in late june and early july 1981 resulted in a 100 km wide tongue of poleward flow extending at least 150 km along the california coast in contrast to the poleward flow on the shelf which appears to be normal during spring and summer the poleward surface flow observed over the slope in july 1981 and 1984 is unusual based on historical hydrographic surveys off the central california coast poleward surface flow over the continental slope occurs seasonally in the winter but is not generally observed after february

dissolved iron and macronutrient distributions in the southern california current system 1 the distribution of dissolved iron in the southern california current system sccs is presented from seven research cruises between 2002 and 2006 dissolved iron concentrations were generally low in most of the study area 0 5 nm although high mixed layer and water column dissolved iron concentrations up to 8 nm were found to be associated with coastal upwelling both along the continental margin and some island platforms a significant supply of iron was probably not from a deep remineralized source but rather from the continental shelf and bottom boundary layer as identified in previous studies along the central and northern california coast with distance offshore dissolved iron decreased more rapidly relative to nitrate in a transition zone 10 250 km offshore during spring and summer resulting in relatively high ratios of nitrate dissolved iron higher nitrate dissolved iron ratios could be the result of utilization and scavenging in addition to an overall lower supply of iron relative to nitrate in the offshore transition zones the low supply of iron leads to phytoplankton iron limitation and a depletion in silicic acid relative to nitrate in the coastal upwelling and transition zones of the sccs

morphotectonics of the northern bogd fault and implications for middle pleistocene to modern uplift rates in southern mongolia abstract assessing the activity of strike slip faults is often facilitated by cumulative offsets of morphological features the december 4th 1957 mongolia earthquake generally referred to as the gobi altai or bogd earthquake had mw 8 1 and created long and complex surface ruptures of c 350 km length along the bogd fault that cuts across the foothills of the gurvan bogd mountains several left laterally and vertically displaced quaternary alluvial fans and morphogenic markers show cumulative offsets allowing for an assessment of the effect of repeated earthquakes and active tectonics on landscape evolution we propose to expand the active tectonic record along this fault up to a middle pleistocene time scale that spans regional climatic fluctuations i e repeated glacial interglacial cycles and hence varying erosional and depositional rates five main drainage areas crosscutting the north ikh bogd segment of the bogd fault were analysed and compared in terms of hypsometry drainage steepness and alluvial fan slope inclination along the mountain front deposits from all drainages form multiple alluvial fan levels that reflect recurring deposition incision cycles previously published ages as well as the spatial distribution of these fan levels suggest that their incision and abandonment is induced by regionally dominant climate fluctuations however the increase of fan slope angles over time and the increased intensity of sub surface folding observed in ground penetrating radar profiles suggests that cumulative tectonic uplift also has a strong impact on alluvial fan morphology estimates of the increase of fan slope angles as a result of cumulative tectonic uplift imply that middle pleistocene to modern vertical slip rates along the north ikh bogd segment of the bogd fault are in the order of 0 9 1 mm yr however much slower vertical slip rates along individual fault segments ranging between 0 06 0 01 mm yr and 0 28 0 07 mm yr indicate that uplift of the ikh bogd plateau occurs as a result of distributed deformation across multiple parallel fault strands within bedrock as well as alluvial fans our results emphasise the importance of regional studies along active faults that take into account the complexity of surface ruptures as well as the occurrence of related structures that can accommodate deformation