pliocene climate history of the western united states derived from lacustrine ostracodes abstract pliocene sediments from several sites in western north america contain ostracodes indicating deposition in lacustrine and wetland settings the ostracodes offer a means of reconstructing the aquatic paleoenvironment because water temperature chemistry and lake volume are coupled to climate reconstruction of these parameters provides a direct insight into pliocene climate the site ages were determined from tephrochronology paleomagnetics and associated mammals the morphology of many ostracode species also provides direct information about the paleoenvironment in which they lived during the pliocene about 3 5 2 5 ma some species have unusually ornate carapace morphology indicative of large geologically stable lakes which must have required a stable climate to sustain them north american pliocene climate changed from a modern like state 4 5 3 5 ma to a period with greater precipitation and less evaporation than today 3 5 2 5 ma this wetter period inferred from the large geologically long lived lakes implies a stable atmospheric circulation pattern the stable circulation pattern collapsed around 2 5 ma and climate returned to a modern like situation

observed evidence of the anomalous south china sea western boundary current during the summers of 2010 and 2011 seven years of directly measured current data from a mooring in the xisha area of the south china sea scs together with shipboard adcp and satellite data have shown the western boundary current wbc anomaly and its vertical structure during the summers of 2010 and 2011 the observed wbc presented obvious year to year variability especially in the summer overall the summer mean velocity at the mooring site over 7 year 2007 2013 was northeastward the moored adcp showed that the northeastward velocity was particularly strong in the summer of 2010 but the increase was confined in the upper 120 m in contrast the northeastward current disappeared throughout the observed depth range from 50 to 450 m in the summer of 2011 even at the deepest observed position the monthly velocity anomalies reached 14 cm s 1 westward and 12 cm s 1 southward in the zonal and meridional directions respectively both the vietnam offshore current voc and double gyres in the western scs disappeared and the southern anticyclonic gyre expanded to strengthened the northward wbc in the summer of 2010 however in summer of 2011 the voc intensified and the northern cyclonic gyre enlarged with its northern edge reaching 18 degrees n slightly north of mooring site which weakened the northeastward wbc the observed scs circulation anomalies during 2010 and 2011 were mainly induced by the basin scale wind field anomalies associated with the 2009 2010 el nino and 2010 2011 la nina

mesoscale eddies in the south china sea observed with altimeter data 1 a composite time series 1993 2000 of sea surface height anomaly from several satellites is used to identify eddies in the south china sea scs the eddy lifetime radius strength and straight line travel distance are estimated altogether 58 anticyclonic eddies and 28 cyclonic eddies are identified for this period they are grouped into four geographical zones according to known eddy generation mechanisms and their statistics are discussed accordingly our geographical classification is a useful first step in gaining an overview of their generation

carbonate deposition pyramid lake subbasin nevada 2 lake levels and polar jet stream positions reconstructed from radiocarbon ages and elevations of carbonates tufas deposited in the lahontan basin most of the tufas in the pyramid lake subbasin were deposited within the last 35 000 yr including most of the mound tufas that border the existing lake many of the older tufas 21 000 yr b p contained in the mounds were formed in association with ground water discharge the radiocarbon 14c ages of the older tufas represent maximum estimates of the time of their formation lake lahontan experienced large and abrupt rises in level at 22 000 15 000 and 11 000 yr b p and three abrupt recessions in level at 16 000 13 600 and 10 000 yr b p the lake level rises that were initiated at 23 500 and 15 500 yr b p are believed to indicate the passage of the polar jet stream over the lahontan basin during expansion of the laurentide ice sheet the jet stream moved south across the basin and during the contraction of the ice sheet the jet stream moved north across the basin the bulk of the carbonate contained in the mound tufas was deposited during the last major lake cycle 23 500 12 000 yr b p indicating that ground and surface water discharges increased at 23 500 and decreased at 12 000 yr b p a lake level oscillation that occurred between 11 000 and 10 000 yr b p is represented by a 2 cm thick layer of dense laminated tufa that occurs at and below 1180 m in the low elevation tufa mounds and at 1205 m in the winnemucca lake subbasin

late quaternary environmental change in the bonneville basin western usa abstract excavation and analyses of small animal remains from stratified raptor deposits spanning the last 11 5 ka together with collection and analysis of over 60 dated fossil woodrat midden samples spanning the last 50 ka provide a detailed record of changing climate in the eastern great basin during the late pleistocene and holocene sagebrush steppe dominated the northern bonneville basin during the full glacial suggesting that conditions were cold and relatively dry in contrast to the southern basin which was also cold but moister limber pine woodlands dominated 13 11 5 ka indicating increased dryness and summer temperatures 6 7 c cooler than present this drying trend accelerated after 11 5 ka causing lake bonneville to drop rapidly eliminating 11 species of fish from the lake from 11 5 8 2 ka xerophytic sagebrush and shadscale scrub replaced more mesophilic shrubs in a step wise fashion a variety of small mammals and plants indicate the early holocene was 3 c cooler and moister than at present not warmer as suggested by a number of climatic models the diversity of plants and animals changed dramatically after 8 2 ka as many species disappeared from the record some of the upland species returned after 4 ka and great salt lake became fresh enough at 3 4 and 1 2 ka to support populations of utah chub

monsoon surges trigger oceanic eddy formation and propagation in the lee of the philippine islands 1 two winter monsoon surge events northerly and easterly of january 2005 are captured in a one way coupled atmosphere 8 km resolution and ocean 3 km resolution simulation of the philippines region intensified wind jets and wakes in the lee of mindoro and luzon islands induce the generation and migration of a pair of counter rotating oceanic eddies in the model with propagation direction related to the orientation of the winds during each of the surges features shared by the eddies include size 100 200 km depth 300 m and propagation speed 0 1 0 15 m s 1 for cyclones mean wintertime model wind stress positive negative curl coincides with the climatological cyclone anticyclone distribution from a prior 8 year altimetry based census of eddies in the southeast quadrant of the south china sea during the winter monsoon moreover the simulation results agree with contemporaneous satellite and historical in situ data characterizing regional oceanic eddy and atmospheric surface jet properties

interannual variability of the south china sea throughflow inferred from wind data and an ocean data assimilation product 1 the luzon strait transport as an index for the south china sea throughflow has attracted much attention recently in this study the interannual variability of luzon strait transport is examined using the island rule and results from ocean data assimilation transport variability obtained from these two approaches is consistent with each other assessment of contribution from each integral segment involved in the island rule indicates that wind stress in the western and central equatorial pacific is the key factor regulating the interannual variability of the luzon strait transport whereas the effect of local wind stress in the vicinity of the luzon strait is secondary analysis also shows that when the westerly easterly wind anomalies in the tropical pacific break out the luzon strait transport increases decreases associated with the variations in the

fish remains from homestead cave and lake levels of the past 13 000 years in the bonneville basin abstract a late quaternary ichthyofauna from homestead cave utah provides a new source of information on lake history in the bonneville basin the fish represented by 11 freshwater species were accumulated between 11 200 and 1000 14c yr b p by scavenging owls the 87sr 86sr ratio of lake bonneville varied with its elevation 87sr 86sr values of fish from the lowest stratum of the cave suggest they grew in a lake near the terminal pleistocene gilbert shoreline in the lowest deposits a decrease in fish size and an increase in species tolerant of higher salinities or temperatures suggest multiple die offs associated with declining lake levels an initial catastrophic post provo die off occurred at 11 300 11 200 14c yr b p and was followed by at least one rebound or recolonization of fish populations but fish were gone from lake bonneville sometime before 10 400 14c yr b p this evidence is inconsistent with previous inferences of a near desiccation of lake bonneville between 13 000 and 12 000 14c yr b p peaks in gila atraria frequencies in the upper strata suggest the great salt lake had highstands at 3400 and 1000 14c yr b p

interannual to decadal variability and trends of sea level in the south china sea interannual to decadal variability and trends of sea level in the south china sea scs are studied using altimetric data during 1993 2012 and reconstructed sea level data from 1950 2009 the interannual variability shows a strong seasonality surface wind anomalies associated with el nino southern oscillation explain the sea level anomaly pattern in the interior scs while rossby waves radiated from the eastern boundary dominate the sea level variability in the eastern scs decadal variability of sea level in the scs follows that in the western tropical pacific with large variance found west of luzon island local atmospheric forcing makes a negative contribution to decadal variability in the central scs and rossby waves radiated from the eastern boundary appear to be important during 1993 2012 decadal sea level averaged in the scs is significantly correlated with the pacific decadal oscillation pdo r 0 96 the decadal variability associated with the pdo accounts for most part of sea level trends in the scs in the last two decades

reinterpretation of the exposed record of the last two cycles of lake bonneville western united states a substantially modified history of the last two cycles of lake bonneville is proposed the bonneville lake cycle began prior to 26 000 yr b p the lake reached the bonneville shoreline about 16 000 yr b p poor dating control limits our knowledge of the timing of subsequent events lake level was maintained at the bonneville shoreline until about 15 000 yr b p or somewhat later when catastrophic downcutting of the outlet caused a rapid drop of 100 m the provo shoreline was formed as rates of isostatic uplift due to this unloading slowed by 13 000 yr b p the lake had fallen below the provo level and reached one close to that of great salt lake by 11 000 yr b p deposits of the little valley lake cycle are identified by their position below a marked unconformity and by amino acid ratios of their fossil gastropods the maximum level of the little valley lake was well below the bonneville shoreline based on degree of soil development and other evidence the little valley lake cycle may be equivalent in age to marine oxygenisotope stage 6 the proposed lake history has climatic implications for the region first because the fluctuations of lake bonneville and lake lahontan during the last cycle of each were apparently out of phase there may have been significant local differences in the timing and character of late pleistocene climate changes in the great basin second although the bonneville and little valley lake cycles were broadly synchronous with maximum episodes of glaciation environmental conditions necessary to generate large lakes did not exist during early wisconsin time

ship observations and numerical simulation of the marine atmospheric boundary layer over the spring oceanic front in the northwestern south china sea the response of the marine atmospheric boundary layer mabl structure to an oceanic front is analyzed using global positioning system gps sounding data obtained during a survey in the northwestern south china sea nscs over a period of about 1 week in april 2013 the weather research and forecasting wrf model is used to further examine the thermodynamical mechanisms of the mabl s response to the front the wrf model successfully simulates the change in the mabl structure across the front which agrees well with the observations the spatially high pass filtered fields of sea surface temperature sst and 10 m neutral equivalent wind from the wrf model simulation show a tight positive coupling between the sst and surface winds near the front meanwhile the sst front works as a damping zone to reduce the enhancement of wind blowing from the warm to the cold side of the front in the lower boundary layer analysis of the momentum budget shows that the most active and significant term affecting horizontal momentum over the frontal zone is the adjustment of the pressure gradient it is found that the front in the nscs is wide enough for slowly moving air parcels to be affected by the change in underlying sst the different thermal structure upwind and downwind of the front causes a baroclinic adjustment of the perturbation pressure from the surface to the midlayer of the mabl which dominates the change in the wind profile across the front

replacement of aragonite by quasi rhombohedral dolomite in a late pleistocene tufa mound great salt lake utah u s a abstract fabric preserving quasi rhombohedral dolomite forms as cement and replacement of aragonite in a tufa mound 2 m thick on the western shoreline of the great salt lake the rounded crystals range in size from 5 to 20 m in diameter crystal faces are not pitted and have numerous sharp edged steps and kinks the quasi rhombohedral forms are the result of crystal growth phenomena and not of post crystallization dissolution microprobe analyses n 92 of the dolomite yield an average 46 mole mgco3 in agreement with the 44 to 45 mole mgco3 content determined from x ray diffraction 30 8 2 position of the 104 peak the great salt lake dolomite is poorly ordered with relative ordering of 28 5 and a reflection ratio of 0 9503 compared to a well ordered standard dolomite the great salt lake dolomite has the poorest ordering of any natural dolomite recorded to date more than half of the electron microprobe analyses show elevated sr abundance indicating that dolomite formed in a rock buffered diagenetic system where much of the bicarbonate and ca were supplied by dissolution of aragonite and mg from the lake water preservation of the tufa fabric by dolomite was accomplished by the closely related dissolution of aragonite and precipitation of dolomite in a fluid undersaturated with respect to aragonite and supersaturated with respect to ca rich dolomite formation of spheroids might reflect a high growth rate from a high alkalinity fluid that was undersaturated with respect to other carbonate minerals maintenance of this growth rate might have been aided by the ca enrichment and cation disordering of the precipitating dolomite phase and the large surface area of a sphere compared to that of an inscribed rhomb

ecosystem and paleohydrological response to quaternary climate change in the bonneville basin utah we report the results of a detailed paleoecological study of the bonneville basin covering the last 280 000 yr our study used fossil ostracodes and a sedimentological record obtained from the august 2000 glad800 drilling operation at great salt lake we analyzed 125 samples taken at 1 m intervals from site 4 gsl00 4 for ostracodes and other paleoecologic and sedimentologic indicators of environmental change multivariate analyses applied to the ostracode data and qualitative analyses of fossil and sedimentological data indicate an alternation between three major environments at the core site over the cored interval 1 shallow saline or hypersaline lakes 2 salt or freshwater marshes and 3 occasional deep freshwater lakes these environmental changes are consistent with shoreline studies of regional lake level fluctuations but provide considerable new detail on both the timing and environmental conditions associated with the various lake phases our age model using 14 c useries tephra and biostratigraphic chronologies allowed us to associate the core s record of regional paleohydrology with the marine oxygen isotope stages of global climate change the core contains continuous records for the last four glacial interglacial sequences salt freshwater marshes were common during the interglacials and deep freshwater conditions correspond with maximum global ice volume in ois 2 and before a maximum in global ice during ois 6 immediately following deep lake phases crashes in lake level from rapid desiccation resulted in the deposition of thick evaporite units our study suggests that the climate of the great salt lake catchment appears to have been drier during ois 6 than during ois 2 we compare our record of environmental change during ois 6 glaciation with other records from the western united states and find that the overall

accelerator mass spectrometer ams radiocarbon dating of pleistocene lake sediments in the great basin abstract pleistocene lake sediments in the great basin typically contain little organic carbon and thus are difficult to date reliably by conventional radioccarbon methods paleoenvironmental data are abundant in these sediments but are of limited value without adequate age controls with the advent of accelerator mass spectrometer ams radiocarbon dating it is now possible to date these paleolacustrine sediments ams dates were obtained on sediment cores from the bonneville franklin and lahontan basins in the bonneville basin the ams based chronology compares well with other chronologies constructed from dated shore zone features in the bonneville and franklin basins ams dates delimit unconformities not apparent by other means we found that dispersed organic carbon from sediments deposited during relatively freshwater intervals provided apparently reliable ams radiocarbon dates carbonate microfossils from the lahontan basin also produced results that appear reasonable while bulk carbonate yielded erroneous results

late wisconsin early holocene vegetation in the bonneville basin abstract woodrat middens from the northern bonneville basin allow a reconstruction of vegetation changes from 14 000 to 9000 yr ago cold montane steppe dominated by sagebrush covered much of the western bonneville basin prior to 13 000 yr ago from 13 000 10 800 yr ago the region was vegetated by limber pine woodlands in lower montane settings and a mosaic of limber pine and sagebrush steppe along basin flour margins these low elevation limber pine woodlands began to retreat upslope after about 11 000 yr ago due to increasingly drier climatic conditions and were replaced by relatively more xeric desert scrub dominated by sagebrush and shadscale the growth of limber pine at low elevations suggests that summer temperatures were as much as 6 c lower than at present this evidence is in apparent conflict with the currently accepted post provo lake bonneville chronology especially the magnitude of the postulated near dessication of lake bonneville from ca 13 000 12 200 yr ago

desert wetlands in the geologic record abstract desert wetlands support flora and fauna in a variety of hydrologic settings including seeps springs marshes wet meadows ponds and spring pools over time eolian alluvial and fluvial sediments become trapped in these settings by a combination of wet ground conditions and dense plant cover the result is a unique combination of clastic sediments chemical precipitates and organic matter that is preserved in the geologic record as ground water discharge gwd deposits gwd deposits contain information on the timing and magnitude of past changes in water table levels and therefore are a potential source of paleohydrologic and paleoclimatic information in addition they can be important archeological and paleontological archives because desert wetlands provide reliable sources of fresh water and thus act as focal points for human and faunal activities in some of the world s harshest and driest lands here we review some of the physical sedimentological and geochemical characteristics common to gwd deposits and provide a contextual framework that researchers can use to identify and interpret geologic deposits associated with desert wetlands we discuss several lines of evidence used to differentiate gwd deposits from lake deposits they are commonly confused and examine how various types of microbiota and depositional facies aid in reconstructing past environmental and hydrologic conditions we also review how late quaternary gwd deposits are dated as well as methods used to investigate desert wetlands deeper in geologic time we end by evaluating the strengths and limitations of hydrologic and climatic records derived from gwd deposits and suggest several avenues of potential future research to further develop and utilize these unique and complex systems

mechanism of weakening of west luzon eddy during la nina years 1 multi satellite sea level anomalies from january 1993 to december 2004 are used to investigate the variability of sea surface features in the south china sea scs applying empirical orthogonal function eof analysis the dominant spatial features and corresponding temporal variability are revealed the most remarkable characteristic of variability on an interannual time scale is the abnormal weakening of meso scale eddy off west luzon west luzon eddy wle during 1998 2001 the possible mechanism inducing the weakening is found to be associated with a large scale forcing over the pacific intruding into the northern scs along the northern coast of luzon moreover the tight correlation between the nino3 4 sea surface temperature index and the interannual variability of large scale forcing indicates that la nina events may modulate the west pacific water entering the northern scs which contributes to the weakening of the wle eventually

interannual variability of the south china sea in a data assimilation model 1 sea surface height ssh variations in the south china sea are examined using results from a data assimilation model after the ssh data have had the annual cycle removed principal component analysis illustrates two distinct anomaly patterns the first mode strongest off vietnam would affect the basin wide gyre intensity the second mode consists of a meridional dipole feature with a nodal line around 12 n and is related to the development of the eastward jet and upwelling off vietnam both eof modes have significant interannual variations and are highly correlated to the enso events the leading phase of mode 2 coefficient provides preliminary evidence for the air sea interaction and the pacific east asian teleconnection an innovative mechanism is proposed to describe a weakened upwelling off luzon in winter 1998 an extra strong basin wide warming in summer 1998 persists into fall and winter preventing the formation of winter upwelling off luzon in that year

oceanic eddy formation and propagation southwest of taiwan 1 oceanic eddies are active and energetic southwest of taiwan the formation and propagation of eddies in this area were investigated using 17 year satellite altimeter data cyclonic eddies ces and anticyclonic eddies aces often coexisted but there were more ces than aces generated during the period from october 1992 to october 2009 aces were stronger and in general lived longer than ces aces occurred more often in winter than in other seasons while ces were more frequent in summer compared with the direct local wind forcing the kuroshio path variability appears to be a dominant factor for eddy formation in this area a conceptual model of an eddy kuroshio interaction is proposed in summer there exists an outflow northwest of luzon island and the kuroshio likely leaps across the luzon strait to the north of the outflow and left of the kuroshio axis ces are often formed which in turn induce aces to the west of ces in winter under the influence of northeasterly monsoon the kuroshio current loop kcl appears southwest of taiwan more frequently than in other seasons and aces are frequently shed from the kcl most of the aces propagate westward and as a result ces are often spun up to the east of the aces the surface south china sea outflow in summer and the kcl in winter are however likely related to the monsoons therefore the indirect effects of monsoon winds are also evident in the seasonal variations of eddy occurrence

a census of eddy activities in the south china sea during 1993 2007 1 numerous mesoscale eddies occur each year in the south china sea scs but their statistical characteristics are still not well documented a pacific basin wide three dimensional physical biogeochemical model has been developed and the result in the scs subdomain is used to quantify the eddy activities during the period of 1993 2007 the modeled results are compared with a merged and gridded satellite product of sea level anomaly by using the same eddy identification and tracking method on average there are about 32 9 2 4 eddies predicted by the model and 32 8 3 4 eddies observed by satellite each year and about 52 of them are cyclonic eddies the radius of these eddies ranges from about 46 5 to 223 5 km with a mean value of 87 4 km more than 70 of the eddies have a radius smaller than 100 km the mean area covered by these eddies each year is around 160 170 km2 equivalent to 9 8 of the scs area with water depths greater than 1000 m linear relationships are found between eddy lifetime and eddy magnitude and between eddy vertical extent and eddy magnitude showing that strong eddies usually last longer and penetrate deeper than weak ones interannual variations in eddy numbers and the total eddy occupied area indicate that eddy activities in the scs do not directly correspond to the el nino southern oscillation events the wind stress curls are thought to be an important but not the only mechanism of eddy genesis in the scs

upper layer circulation in the south china sea abstract upper layer circulation is investigated by using all available historical temperature profiles combined with climatological temperature salinity relationships in the south china sea two cyclonic eddies are revealed one is located east of vietnam called the east vietnam eddy and the other is off northwest luzon called the west luzon eddy both local ekman pumping and remotely forced basin scale circulation are important mechanisms controlling these two eddies the luzon strait transport relative to 400 db is estimated to be of the order 3 0 sv 1 sv 1 106 m3 s 1 in the mean and has a seasonal cycle dominated by the annual signal with a maximum 5 3 sv in january february and a minimum 0 2 sv in june july pressure gradients are also examined to explore the dynamics of the intrusion of waters from the pacific into the south china sea through the luzon strait

transports and tidal current estimates in the taiwan strait from shipboard adcp observations 1999 2001 tidal and mean flows in the taiwan strait are obtained from analysis of 2 5 years 1999 2001 of shipboard adcp data using a spatial least squares technique the average tidal current amplitude is 0 46 ms 1 the maximum amplitude is 0 80 ms 1 at the northeast and southeast entrances and the minimum amplitude is 0 20 ms 1 in the middle of the strait the tidal current ellipses derived from the shipboard adcp data compare well with the predictions of a high resolution regional tidal model for the mean currents the average velocity is about 0 40 ms 1 the mean transport through the strait is northward into the east china sea at 1 8 sv the transport is related to the along strait wind by a simple regression transport sv 2 42 0 12 wind ms 1 using this empirical formula the maximum seasonal transport is in summer about 2 7 sv the minimum transport is in winter at 0 9 sv and the mean transport is 1 8 sv for comparison this result indicates that the seasonal amplitude is almost identical to the classical estimate by wyrtki physical oceanography of the southeast asian waters scientific results of marine investigations of the south china sea and gulf of thailand 1959 1961 naga report 2 scripps institute of oceanography 195 pp based on the mass balance in the south china sea while the mean is close to the recent estimate by isobe continental shelf research 19 1999 195 based on the mass balance in the east china sea 2003 elsevier science b v all rights reserved

the effects of thermohaline circulation on wind driven circulation in the south china sea abstractthe dynamic influence of thermohaline circulation on wind driven circulation in the south china sea scs is studied using a simple reduced gravity model in which the upwelling driven by mixing in the abyssal ocean is treated in terms of an upward pumping distributed at the base of the upper layer because of the strong upwelling of deep water the cyclonic gyre in the northern scs is weakened but the anticyclonic gyre in the southern scs is intensified in summer while cyclonic gyres in both the southern and northern scs are weakened in winter for all seasons the dynamic influence of thermohaline circulation on wind driven circulation is larger in the northern scs than in the southern scs analysis suggests that the upwelling associated with the thermohaline circulation in the deep ocean plays a crucial role in regulating the wind driven circulation in the upper ocean

interannual variability of the surface summertime eastward jet in the south china sea the summertime eastward jet sej located around 12 n 110 e 113 e as the offshore extension of the vietnam coastal current is an important feature of the south china sea scs surface circulation in boreal summer analysis of satellite derived sea level and sea surface wind data during 1992 2012 reveals pronounced interannual variations in its surface strength ssej and latitudinal position ysej in most of these years the jas july august and september mean ssej fluctuates between 0 17 and 0 55 m s 1 while ysej shifts between 10 7 n and 14 3 n these variations of the sej are predominantly contributed from the geostrophic current component that is linked to a meridional dipole pattern of sea level variations this sea level dipole pattern is primarily induced by local wind changes within the scs associated with the el nino southern oscillation enso enhanced weakened southwest monsoon at the developing decaying stage of an el nino event causes a stronger weaker sej located south north of its mean position remote wind forcing from the tropical pacific can also affect the sea level in the scs via energy transmission through the philippine archipelago but its effect on the sej is small the impact of the oceanic internal variability such as eddy current interaction is assessed using an ocean general circulation model ogcm such impact can lead to considerable year to year changes of sea level and the sej equivalent to 20 of the observed variation this implies the complexity and prediction difficulty of the upper ocean circulation in this region

seasonal structures of upper layer circulation in the southern south china sea from in situ observations 1 conductivity temperature depth and acoustic doppler current profiler data from six cruises spanning 1989 to 1999 are used to investigate the seasonal structure of the upper layer circulation in the southern south china sea scs the surveys were made during winter late spring summer and late fall more detailed structures not presented in previous studies are found in summer the upper layer circulation of the southern scs is dominated by an anticyclonic gyre with a strong eastward flow on its northern border which originates off the southeast coast of vietnam the summer southeast vietnam offshore current in winter a stronger cyclonic gyre exists in the western portion of the southern scs and a weaker anticyclonic circulation in the eastern portion at the juncture of these two gyres there is a strong northward upwind flow called the winter natuna off shelf current in late spring the anticyclonic gyre begins to form in the northwest and a trace of the natuna off shelf current can still be observed especially subsurface in the southern part of the study area mesoscale eddies are active in this period in late fall the winter type pattern begins to appear the natuna off shelf current and the cyclonic gyre in the northwest part of the southern scs emerge and the summer anticyclonic gyre vanishes in the southeast the currents are basically toward the northeast with an anticyclonic trend revealing a multi eddy feature these upper ocean currents appear consistent with the wind forcing

the composite nature of the provo level of lake bonneville great basin western north america abstract deposits of a transgressive phase lake bonneville stillstand or oscillation are found just below the elevation of the regressive phase provo shoreline at numerous exposures throughout the bonneville basin existence of these subprovo shoreline deposits provides a new explanation for the massive size of provo depositional and erosional landforms which can no longer be explained by a long stillstand at the provo shoreline provo coastal landforms are large because they are superimposed on subprovo landforms results also help to clarify divergent interpretations regarding the relative age of the provo shoreline and the number of times it was occupied by the water plane occupation of approximately the same level during both the transgressive and the regressive phase of lake bonneville may be coincidental or it may indicate that a bedrock sill controlled outflow at subprovo as well as provo time rise to the bonneville level could have occurred after massive slope failure plugged the outlet pass

paleomagnetic investigation of the bonneville alloformation lake bonneville utah abstract paleomagnetic secular variation in a portion of the bonneville alloformation is compared with secular variation in lacustrine sediments in the mono basin california and with secular variation in lake lahontan sediments in the northwestern great basin the comparison places an age of about 18 000 yr b p and a span of 1000 to 3000 yr on part of a transgressive stage of lake bonneville near delta utah that is coeval with a wet period in the lahontan basin

eddy heat and salt transports in the south china sea and their seasonal modulations this study describes characteristics of eddy turbulent heat and salt transports in the basin scale circulation as well as in the embedded mesoscale eddy found in the south china sea scs we first showed the features of turbulent heat and salt transports in mesoscale eddies using sea level anomaly sla data in situ hydrographic data and 375 argo profiles we found that the transports were horizontally variable due to asymmetric distributions of temperature and salinity anomalies and that they were vertically correlated with the thermocline and halocline depths in the eddies an existing barrier layer caused the halocline and eddy salt transport to be relatively shallow we then analyzed the transports in the basin scale circulation using an eddy diffusivity method and the sea surface height data the argo profiles and the climatological hydrographic data we found that relatively large poleward eddy heat transports occurred to the east of vietnam eov in summer and to the west of the luzon islands wol in winter while a large equatorward heat transport was located to the west of the luzon strait wls in winter the eddy salt transports were mostly similar to the heat transports but in the equatorward direction due to the fact that the mean salinity in the upper layer in the scs tended to decrease toward the equator using a 21 2 layer reduced gravity model we conducted a baroclinic instability study and showed that the baroclinic instability was critical to the seasonal variation of eddy kinetic energy eke and thus the eddy transports eov wls and wol were regions with strong baroclinic instability and thus with intensified eddy transports in the scs the combined effects of vertical velocity shear latitude and stratification determined the intensity of the baroclinic instability which intensified the eddy transports eov during summer and wls and wol during winter

assessing controls on isolated carbonate platform development in central luconia nw borneo from a regional 3d seismic facies and geomorphology investigation

winter eddy genesis in the eastern south china sea due to orographic wind jets abstract generation of mesoscale eddies in the eastern south china sea scs in winters during august 1999 to july 2002 is studied with a reduced gravity model it is found that the orographic wind jets associated with the northeast winter monsoon and the gaps in the mountainous island chain along the eastern boundary of the scs can spin up cyclonic and anticyclonic eddies over the scs results suggest that direct wind forcing could be an important generation mechanism for the rich eddy activity in the scs and that to simulate this mechanism the resolution of the wind forcing has to be high enough to resolve the local wind jets induced by orographic effects

kuroshio intrusion and the circulation in the south china sea 1 the princeton ocean model is used to study the circulation in the south china sea scs and its seasonal transition kuroshio enters leaves the scs through the southern northern portion of the luzon strait the annually averaged net volume flux through the luzon strait is 2 sv into the scs with seasonal reversals the inflow season is from may to january with the maximum intrusion of kuroshio water reaching the western scs during fall in compensation of summertime surface offshore transport associated with coastal upwelling from february to april the net transport reverses from the scs to the pacific the intruded kuroshio often forms an anticyclonic current loop west of the luzon strait the current loop separates near the dongsha islands with the northward branch continuously feeding the south china sea warm current scswc near the shelf break and the westward branch becoming the south china sea branch of kuroshio on the slope which is most apparent in the fall the scswc appears from december to february on the seaward side of the shelf break flowing eastward against the prevailing wind diagnosis shows that the onshore ekman transport due to northeasterly monsoon generates upwelling when moving upslope and the particular distributions of the density and sea level associated with the cross shelf motion supports the scswc

tropical cyclone enhanced vertical transport in the northwestern south china sea i mooring observation analysis for washi 2005 abstract using mooring observed horizontal velocities and temperature from july 28 to august 2 2005 this study analyzes the temporal vertical variation of the diagnostic vertical velocity and mass transport during passage of tropical storm washi 2005 over the northwestern continental shelf of the south china sea scs the results show that the total vertical velocity is of the order of o 1 10 4 m s 1 in the mixed layer above 25 m and of o 1 10 5 m s 1 in the lower layer dynamically the geostrophic advection and unsteady behavior of density induced by near inertial oscillation are dominant factors in the upper and lower layers respectively as tropical storm washi 2005 passed by from july 29 to 31 2005 the upward vertical velocity was dominant and significantly enhanced to the order of o 1 10 3 m s 1 the diagnosed vertical velocity in the upper layer is one order greater than the averaged ekman pumping velocity which occurred one day earlier the vertical advection transport calculated from the diagnosed vertical velocity reaches o 1 10 5 kg s 1m 3 one order greater than that induced by turbulent mixing time averaged transports by vertical advection and mixing are both upward in the layer above the thermocline during the storm passage

mesoscale eddies in the northern south china sea a fine grid resolution model with realistic bathymetry and forcing has been developed to study the characteristics of the mesoscale eddies for the northern south china sea scs the scs model derives its open boundary conditions from a larger scale model which minimizes errors related to the uncertainty of the kuroshio intrusion at the open boundaries the model results are consistent with previous observations model sea surface height anomaly demonstrates that the hydrography and circulation in the northern scs are modulated by westward propagating mesoscale eddies originating in the vicinity of the luzon strait this explains the observed intra seasonal fluctuations at the southeast asian time series study seats station the mesoscale eddies have the same propagation speed as baroclinic rossby waves 0 1 ms 1 the periods of eddy shedding estimated from strouhal number are around 40 50 days in december and 80 120 days in august respectively the seasonal variability of the kuroshio intrusion results in more eddies in winter than in summer r 2007 elsevier ltd all rights reserved

a gis based method for depicting the characteristics of mesoscale eddies a case study in the northern south china sea the paper presents a geographical information system gis based method for depicting the characteristics particularly the internal structures and evolutionary processes of mesoscale eddies this was done by examining topologic relations among closed sea surface height ssh contours that were reconstructed from the naval research laboratory navy layered ocean model nlom different scenarios of the topological relations among the contour lines permitted the identification of the outermost outline of eddies and the depiction of the number of cores in each mesoscale oceanic eddy with full consideration of the internal structure of the eddies we then reconstructed the evolutionary processes of these eddies and the results were compared with empirical observations on three long lived mesoscale eddies in the northern south china sea scs tracking results were similar thereby validating our method as being efficient and robust in reconstructing mesoscale ocean eddies especially their evolutionary processes based on their internal structures

generation and life cycle of the dipole in the south china sea summer circulation 1 the south china sea scs summer circulation often has a dipole structure associated with an eastward jet appearing off central vietnam the dipole has an anticyclonic eddy ae south of the jet and a cyclonic eddy ce north of it the life cycle of the dipole structure is analyzed using satellite altimetry data and a reduced gravity model on average the dipole structure begins in june peaks in strength in august or september and disappears in october the dipole evolution lags behind the basin scale wind by about 40 days and 40 days are exactly what it takes for baroclinic planetary waves to cross the southern scs our results show that the vorticity transports from the nonlinear effect of the western boundary currents are crucial for the generation of the dipole structure in addition the strength and direction of the offshore wind jet also play a significant role in determining the magnitudes and the core positions of the two concomitant eddies

weakest winter south china sea western boundary current caused by the 2015 2016 el nino event during the winter of 2015 2016 the strongest el nino event of the 21st century occurred at the same time volume transport vt time series of the south china sea western boundary current scswbc exhibited a minimum value of 3 7 sv 1 sv 1 106 m3 s 1 toward the southwest indicating the weakest strength ever recorded in boreal winter from november to february the south china sea scs cyclonic gyre inferred from the satellite derived surface absolute geostrophic current was significantly reduced it was considered that the weakened wind stress curl negative anomaly over the scs resulting from an anticyclone over the philippine sea played an essential role the anticyclone arose from a rossby wave response to a negative sea surface temperature anomaly in the northwest pacific this idea is further supported by composite analysis which shows that during el nino la nina winter negative positive wind stress curl anomalies prevail in the philippines sea and the scs thus the wind stress curl over the scs is reduced strengthened leading to a weaker stronger scs cyclonic gyre and scswbc the mean vt of scswbc is 4 7 sv 5 6 sv which is smaller larger than 5 2 sv in normal years this study provides robust observational evidence from long term in situ volume transport monitoring that el nino can have a significant impact on the scswbc through an atmosphere bridged teleconnection this article is protected by copyright all rights reserved

chronology of lake bonneville 30 000 to 10 000 yr b p abstract 368 radiocarbon ages between 30 and 10 cal ka for samples collected from outcrops and shorelines from the lake bonneville basin have been compiled for this paper samples include 1 organic materials from sources outside the lake such as wood charcoal plant fragments from emergent aquatics and dispersed wetland organics and 2 carbonate materials deposited in the lake such as mollusk shells tufa charophyte debris ooids and marl in general organic materials provide rather than precise ages for lacustrine events but their interpretation is less complicated than interpretation of results from carbonate samples the data set shows evidence of contamination of different carbonate samples with both younger carbon and older carbon for example a radiocarbon reservoir at certain places within the lake during the middle transgressive phase accounts for ages of mollusk shells that are older than basal wood ages at similar altitudes the large number of ages permits an accurate reconstruction of the lake chronology conflicts between ages can be detected and reliable ages can be meaningfully integrated in interpretations if fewer ages were available the chronology might look simpler but its accuracy would be unknown

late quaternary environments in ruby valley nevada abstract palynological data from sediment cores from the ruby marshes provide a record of environmental and climatic changes over the last 40 000 yr the modern marsh waters are fresh but no deeper than 3 m a shallow saline lake occupied this basin during the middle wisconsin followed by fresh and perhaps deep waters by 18 000 to 15 000 yr b p no sediments were recovered for the period between 15 000 and 11 000 yr b p possibly due to lake desiccation by 10 800 yr b p a fresh water lake was again present and deeper than modern conditions lasted until 6800 yr b p the middle holocene was characterized by very shallow water and perhaps complete desiccation the marsh system deepened after 4700 yr b p and fresh water conditions persisted until modern times vegetation changes in ruby valley were more gradual than those seen in the paleolimno logical record sagebrush steppe was more widespread than at present through the late pleistocene and early holocene giving way somewhat to expanded shadscale vegetation between 8500 and 6800 yr b p shadscale steppe contracted by 4000 yr b p but had greater than modern coverage until 1000 to 500 yr ago pinyon juniper woodland was established in the southern ruby mountains by 4700 yr b p

overview of the multi layer circulation in the south china sea abstract the south china sea scs is a semi enclosed ocean basin with its sole deepwater renewal channel in the northeast the luzon strait connected to the northwestern pacific the circulation in the scs is endowed with a distinctive multi layer structure which is influenced by the seasonally reversing southeast asian monsoon at the surface modulated kuroshio intrusion in the upper layer and enhanced diapycnal mixing and persistent luzon strait deepwater overflow in the deep layer after being diapycnally mixed by energetic internal tides internal waves and mesoscale eddies waters entering the scs in the upper and deep layers through the luzon strait are returned to the northwestern pacific in the intermediate layer this inflow outflow inflow structure in vertical induces net inflows of potential vorticity in the upper and deep layers and a net outflow of potential vorticity in the intermediate layer of the luzon strait which are believed to be closely related with the circulation structure in the scs a sandwiched circulation in the scs namely anticyclonic in the intermediate layer and cyclonic in the upper and deeper layers was recently reported but controversial issues still remain on its spatial pattern and temporal variability to ascertain this sandwiched circulation and reveal its driving mechanism is of much scientific interest to the on going discussion on the scs circulation and its role in regional climate different from previous review articles focusing on eddies or circulation in a specific layer or area we overview the full depth circulation of the scs layer by layer and outline its possible forcing mechanisms and furthermore provide perspectives for further investigation

the changing influences of enso and the pacific meridional mode on mesoscale eddies in the south china sea abstractthis study finds that the correlation between el nino southern oscillation enso and the activity of mesoscale oceanic eddies in the south china sea scs changed around 2004 the mesoscal

anticyclonic eddy sheddings from kuroshio loop and the accompanying cyclonic eddy in the northeastern south china sea abstractsheddings of kuroshio loop current klc eddies in the northeastern south china sea scs are investigated using mooring arrays multiple satellite data and data assimilative hycom products based on altimeter sea surface heights between 1992 and 2014 a total of 19 prominent klc eddy shedding klces events were identified among which four events were confirmed by the concurrent moored and satellite observations compared to the leaping behavior of kuroshio klces is a relatively short duration phenomenon that primarily occurs in boreal autumn and winter the klc and its shedding anticyclonic eddy ae trap a large amount of pacific water with high temperature salinity and low chlorophyll concentration in the upper layer the corresponding annual mean transport caused by klces reaches 0 24 0 38 sv 1 sv 106 m3 s 1 accounting for 6 8 10 8 of the upper layer luzon strait transport altimeter based statistics show that among 90 of the historical klces events a cyclonic eddy ce is immedi

mooring observations and numerical modeling of thermal structures in the south china sea 1 three sets of autonomous temperature line acquisition systems were deployed in the south china sea gaps aside the data covered nearly 3 years at the northern station and about 2 years farther south fluctuations ranged from episodic to interannual internal tides more diurnal than semidiurnal were active basinwide twelve typhoons passed during measurement periods the most severe one typhoon babs in 1998 caused a temperature drop of over 7 c at 50 m despite strong monsoons only near surface temperature showed clear seasonal variations intraseasonal variations induced by mesoscale eddy stood out much better at subsurface depths propagating eddies aside some eddies were seasonal and nearly stationary from daily archives of an eddy resolving data assimilating ocean model east asian seas nowcast forecast system we identified two paradigms leading to the generation of a persistent spring summer warm eddy in the central western basin in normal years a complete cyclonic gyre was driven by a strong winter northeast monsoon water piled up along the periphery of the south china sea afterward a warm eddy could be generated from west of luzon island and propagated westward while intensifying under a weak northeast monsoon such as in el nino years piled up water tended to stay in the southern basin when the wind relaxed in spring warm water returned northward to form a warm eddy in the central western basin transition from sw to ne monsoon also often led to a warm eddy generation in southern latitudes when the summer eastward jet departing from central vietnam broke up

the importance of high horizontal resolution and accurate coastline geometry in modeling south china sea inflow as resolution is increased from 1 2 to 1 32 in pacific ocean simulations using the nrl layered ocean model marked changes are found in the kuroshio s mean pathway as it intrudes into the south china sea scs via the luzon strait with increased horizontal resolution comes a more accurate representation of the coastline geometry associated with the batan babuyan islands within the strait and a reduction in the modeled westward intrusion of the kuroshio into the scs the 1 16 model is extremely sensitive to two very small scale shoals calayan bank and a shoal north of calayan island that are resolvable at this grid spacing the exclusion of these three model gridpoints significantly alters the mean kuroshio pathway to resemble the pathway from the 1 8 model in addition excluding all islands within the luzon strait in the 1 16 model gives a deep intrusion mean pathway as found in the 1 2 model

deep structure of the southern apennines italy thin skinned or thick skinned 1 the deep structure of the southern apennines sa accretionary wedge is still debated since industrial seismic reflection and well data provide reliable constraints only to a depth of about 10 km as a consequence two directly linked questions regard 1 the shortening in the accretionary prism particularly within the buried apulian thrust units and 2 the degree of involvement of the lower plate basement i e the apulian crystalline basement to address these issues we have constructed a regional section along a recently released deep seismic reflection profile crop 04 which intersects the entire sa the resulting cross section adequately constrained to a depth of about 15 km has been framed in a geodynamic scenario characterized by the eastward roll back of the westward subducting apulo adriatic lithosphere on the basis of this section we speculate on the deep structure building both thin and thick skinned thrust models a cross check of these end members models against documented tectonic geophysical and geochemical features shows that the thin skinned model is generally more consistent with the available data the development of basement slices with thicknesses of tens of kilometers is unlikely while it remains possible that the apulian basement could have been involved with its upper few kilometers in the thin skinned model the total shortening of the allochthonous units i e apennine and apulian carbonate platforms and lagonegro basin is estimated to be greater than 280 300 km some 90 km of shortening can be attributed to the apulian thrust units

high resolution palynological record of holocene climatic and oceanographic changes in the northern south china sea abstract for the first time palynological records of terrestrial palynomorphs and dinoflagellate cysts are investigated in a sediment core from the northern south china sea scs covering the last 12 500 years both terrestrial and marine palynomorph records show strong signals of the sea level change during the studied interval the highest herb pollen content was associated with extensive grasslands on the exposed shelf at the low sea level stand during the younger dryas and early holocene the increase in fern spores and decrease in concentrations of dinoflagellate cysts and terrestrial palynomorphs was observed during the sea level rise interval from 12 500 to 6800 or 6000 cal yr bp then the sea level became stabilized and consistently low dinoflagellate cyst abundances and high abundances of fern spores were recorded a high abundance of impagidinium in the period 12 000 10 400 cal yr bp possibly resulted from increased input of western philippine sea waters into the scs and the branching of the kuroshio current a short term decrease of impagidinium at 11 700 11 000 cal yr bp corresponding to the mwp 1b event might be associated with input of the east china sea waters through the taiwan strait the relationship between the sedimentation rates and the concentrations of terrestrial palynomorphs indicates a water dominant transport for pollen and spore dispersal prior to 6300 cal yr bp whereas wind transport became more prominent thereafter the timing of this change corresponds to the highest sea level stand at 6800 6000 cal yr bp when the present oceanographic setting was formed the mid holocene optimum can be seen by the highest abundance of subtropical tropical broad leaved arboreal pollen and by the highest abundances of dapsilidinium pastielsii three strengthened winter monsoon intervals at 5500 cal yr bp 4000 cal yr bp and 2500 cal yr bp are reflected by increases in pinus pollen content after the present oceanographic condition formed

great salt lake and precursors utah the last 30 000 years sediment cores up to 6 5 m in length from the south arm of great salt lake utah have been correlated radiocarbon ages and volcanic tephra layers indicate a record of greater than 30 000 years a variety of approaches have been employed to collect data used in stratigraphic correlation and lake elevation interpretation these include acoustic stratigraphy sedimentologic analyses mineralogy geochemistry major element c o and s isotopes and organics paleontology and pollen the results indicate that prior to 32 000 year b p an ephemeral saline lake playa system was present in the basin the perennial lake which has occupied the basin since this time rose in a series of three major steps the freshest water conditions and presumably highest altitude was reached at about 17 000 year b p the lake remained fresh for a brief period followed by a rapid increase in salinity and sharp lowering in elevation to levels below that of the present great salt lake the lake remained at low elevations and divided at times into a north and south basin until about 8 000 year b p since that time with the exception of two short rises to about 1290 m the lake level has remained near the present elevation of 1280 m

a revised chronology for the last pleistocene lake cycle in the central lahontan basin radiocarbon dates of plant materials from packrat middens in caves below the elevation of the last high stand of pleistocene lake lahontan in conjunction with radiocarbon dates of ancient archaeological materials provide evidence that the last high stand terminated before 12 070 yr b p this new information suggests that the last major fluctuation in the level of lake lahontan was approximately synchronous with those of lakes bonneville and russell and that these three lakes probably responded contemporaneously to the same regional paleoclimatic changes

summer kuroshio intrusion through the luzon strait confirmed from observations and a diagnostic model in summer 2009 abstract based on current measurements recorded at mooring station n2 20 40 441 n 120 38 324 e hydrographic data and argo observations in the period starting from july 2009 a diagnostic model with a modified inverse method is used to study the circulation in the luzon strait ls a number of new circulation features in the ls are found as follows 1 both observed and modeled currents show that the intruded kuroshio flow northwestward through the ls into the south china sea scs in the upper 400 m during july 2009 2 the diagnostic model confirms that the kuroshio is located in the area east of 121 20 e and west of 122 20 e at 20 00 n there is a meso scale cyclonic eddy at both the surface and 1000 m depth in the area west of the kuroshio near 20 00 n the meso scale cyclonic eddy forced the argo float 1 to make the cyclonic trajectory then the argo float 1 went into the area of the western kuroshio the argo float 1 was tracked as the flow moved northwestward into the scs across the ls in july and august 2009 reflecting the northwestward flow at both the surface and 1000 m depth which coincided with modeled currents these results confirm the northwestward kuroshio intrusion into the scs across the ls in summer 2009 for the first time 3 from the dimensional analysis for the equation of stream function it is seen that the joint effect of the baroclinity and relief jebar and the effect are two important mechanisms on the kuroshio intrusion into the scs in this period this summer kuroshio intrusion results from the weaker upstream kuroshio transport in summer 2009 el nino initiating period due to inertia effects and is associated with a weak volume transport across the ls 2 15 106 m3 s 1 westward 4 after comparison of the dynamics of the kuroshio intrusion during october 2008 and summer 2009 it is clear that these were influenced by the seasonal variability due to the monsoon winds and the interannual variation resulting from the weak upstream kuroshio transport affected by the enso due to inertia effects

east asian monsoon evolution since the late miocene from the south china sea abstract the south china sea scs has become a global focus for paleoclimatic and paleoceanographic studies due to its location which makes it highly sensitive to the east asian monsoon and to pacific ocean changes we present here a refined magnetostratigraphy for the last 6 5 ma for hole u1431d which was recovered during iodp expedition 349 in the central scs magnetic analyses demonstrate that magnetite is the dominant magnetic carrier except for within a greigite bearing layer at 130 5 132 0 meters below sea floor the greigite layer coincides with the timing of intensification of northern hemisphere glaciation and records an oceanographic response to this event environmental magnetic results indicate that the east asian summer and winter monsoon were stable from 6 5 to 5 ma the summer monsoon intensified at 5 ma and then weakened gradually since 3 8 ma in contrast the winter monsoon weakened at 5 ma and has then been enhanced since 3 8 ma and more stable from 0 6 ma spectral analysis indicates that the east asian summer monsoon was driven directly by low latitude insolation changes before 3 2 ma and that it has been affected by both low latitude insolation and high latitude ice volume changes since 3 2 ma

late quaternary eolian dust in surficial deposits of a colorado plateau grassland controls on distribution and ecologic effects abstract in a semi arid upland setting on the colorado plateau that is underlain by nutrient poor paleozoic eolian sandstone alternating episodes of dune activity and soil formation during the late pleistocene and holocene have produced dominantly sandy deposits that support grass and shrub communities these deposits also contain eolian dust especially in paleosols eolian dust in these deposits is indicated by several mineralogic and chemical disparities with local bedrock but it is most readily shown by the abundance of titaniferous magnetite in the sandy deposits that is absent in local bedrock magnetite and some potential plant nutrients especially p k na mn and zn covary positively with depth 3 4 m in dune crest and dune swale settings magnetite abundance also correlates strongly and positively with abundances of other elements e g ti li as th la and sc that are geochemically stable in these environments soil property variations with depth can be ascribed to three primary factors 1 shifts in local geomorphic setting 2 accumulation of relatively high amounts of atmospheric mineral dust inputs during periods of land surface stability and 3 variations in dust flux and composition that are likely related to changes in dust source regions shifts in geomorphic setting are revealed by large variations in soil texture and are also expressed by changes in soil chemical and magnetic properties variable dust inputs are indicated by both changes in dust flux and changes in relations among magnetic chemical and textural properties the largest of these changes is found in sediment that spans late pleistocene to early holocene time increased dust inputs to the central colorado plateau during this period may have been related to desiccation and shrinkage of large lakes from about 12 to 8 ka in western north america that exposed vast surfaces capable of emitting dust soil properties that result from variable dust accumulation and redistribution in these surficial deposits during the late quaternary are important to modern ecosystem dynamics because some plants today utilize nutrients deposited as long ago as about 12 15 ky and because variations in fine grained silt sediment including eolian dust influence soil moisture capacity

the younger dryas phase of great salt lake utah usa abstract field investigations at the public shooting grounds a wildlife management area on the northeastern shore of great salt lake and radiocarbon dating show that the great salt lake rose to the gilbert shoreline sometime between 12 9 and 11 2 cal ka we interpret a ripple laminated sand unit exposed at the public shooting grounds and dated to this time interval as the nearshore sediments of great salt lake deposited during the formation of the gilbert shoreline the ripple laminated sand is overlain by channel fill deposits that overlap in age 11 9 11 2 cal ka with the sand and by wetland deposits 11 1 to 10 5 cal ka consistent accelerator mass spectrometry radiocarbon ages were obtained from samples of plant fragments including those of emergent aquatic plants but mollusk shells from spring and marsh deposits yielded anomalously old ages probably because of a variable radiocarbon reservoir effect the bonneville basin was effectively wet during at least part of the younger dryas global cooling interval however conflicting results from some great basin locations and proxy records indicate that the regional effects of younger dryas cooling are still not well understood

patterns of hydroclimatic change in the rocky mountains and surrounding regions since the last glacial maximum abstract the paleohydrologic record of western north america since the last glacial maximum reveals a wide range of hydroclimatic variability in time and space to improve the understanding of abrupt hydroclimatic shifts and millennial scale hydrologic changes in the central rocky mountains we reconstruct the lake level histories of two small lakes in the beartooth and bighorn mountains in northern wyoming over the past 17 ka to do so we use ground penetrating radar gpr and sediment cores to track the elevations of shoreline sediments within the lakes through time we compare the stratigraphies with those from four other lakes in wyoming and colorado and find widespread evidence for a terminal pleistocene drought from 15 to 11 ka an early holocene humid period from 11 to 8 ka and mid holocene aridity from 8 to 5 5 ka the northern wyoming lakes also provide evidence of high levels in the pleistocene possibly before ca 15 ka and rapid hydroclimatic changes that may have correlated with heinrich event 1 ca 16 8 ka we place the changes in a broad context by summarizing and mapping water level changes from 107 additional previously studied lakes important patterns include 1 extensive drying across the western u s after 15 ka 2 sub regional differences during the pleistocene holocene transition 3 a north south contrast from 9 to 6 ka consistent with a northward shift in storm tracks as the influence of the laurentide ice sheet diminished and 4 rapid increases in effective moisture across much of western north america from 6 to 4 ka

observed sub inertial current variability and volume transport over the continental shelf in the northern south china sea abstract sub inertial currents sics over the continental shelf of the northern south china sea nscs are investigated using the in situ current observations of acoustic doppler current profiler adcp mooring arrays off the pearl river estuary in 2006 and 2007 the survey was carried out in four separate time periods summer winter spring before the onset of the southwesterly monsoon and fall after the establishment of the northeasterly monsoon the observations showed that the current directions were generally along the shelf consistent with the directions of monsoonal winds the currents were also affected by a few of mesoscale eddy events in summer 2006 the volume transport was northeastward with a mean magnitude of 1 4 sv through a cross shelf section from the site of the depth of 135 m to the coast in winter 2006 2007 spring 2007 and fall 2007 the volume transports were all southwestward with magnitudes of 2 0 2 1 and 0 9 sv respectively through a cross shelf section from the site of the depth of 290 m to the coast the standard deviations of the sics were generally smaller than the velocities of the mean currents and the variability of sics showed significant correlation with the local sea surface winds no persistent counter wind currents were observed in the study area during the fall and winter observational periods

early holocene great salt lake usa shorelines and surficial deposits including buried forest floor mats and organic rich wetland sediments show that great salt lake did not rise higher than modern lake levels during the earliest holocene 11 5 10 2 cal ka bp 10 9 c 14 ka bp during that period finely laminated organic rich muds sapropel containing brine shrimp cysts and pellets and interbedded sodium sulfate salts were deposited on the lake floor sapropel deposition was probably caused by stratification of the water column a freshwater cap possibly was formed by groundwater which had been stored in upland aquifers during the immediately preceding late pleistocene deep lake cycle lake bonneville and was actively discharging on the basin floor a climate characterized by low precipitation and runoff combined with local areas of groundwater discharge in piedmont settings could explain the apparent conflict between evidence for a shallow lake a dry climate and previously published interpretations for a moist climate in the great salt lake basin of the eastern great basin c 2015 university of washington published by elsevier inc all rights reserved

last glacial loess in the conterminous usa the conterminous united states contains an extensive and generally well studied record of last glacial loess the loess occurs in diverse physiographic provinces and under a wide range of climatic and ecological conditions both glacial and non glacial loess sources are present and many properties of the loess vary systematically with distance from loess sources united states midcontinent last glacial loess is probably the thickest in the world and our calculated mass accumulation rates mars are as high as 17 500 g m 2 yr at the bignell hill locality in nebraska and many near source localities have mars greater than 1500 g m 2 yr these mars are high relative to rates calculated in other loess provinces around the world recent models of last glacial dust sources fail to predict the extent and magnitude of dust flux from the mid continent of the united states a better understanding of linkages between climate ice sheet behaviour routing of glacial meltwater land surface processes beyond the ice margin and vegetation is needed to improve the predictive capabilities of models simulating dust flux from this region r 2003 elsevier ltd all rights reserved

basin scale wind forced dynamics of the seasonal southern south china sea gyre 1 using observed wind forcing the seasonal development and disappearance of the near surface anticyclonic gyre in the southern south china sea is modeled along with associated dynamic features forced by monsoon winds the ocean circulation in the south china sea alternates between a single cyclonic gyre during the winter northeast monsoon and a double gyre cyclonic anticyclonic in the northern southern south china sea during the summer southwest monsoon reversing the western boundary current along vietnam with each shift of the monsoon regime during the summer southwest monsoon the poleward western boundary current converges with the equatorward western boundary current of the northern gyre turning offshore to create an eastward jet and flanking dipole recirculation near 13 n the development and timing of the eastward jet and recirculations are consistent with large scale basin dynamics the subsequent transition to the winter northeast monsoon regime destroys the recirculation cells and eastward jet employing high resolution 1 5 layer and 2 0 layer numerical models we demonstrate the applicability of large scale dynamics to the deeper central basin of the south china sea specifically showing that the gyre scale circulation governs the development of the eastward jet and dipole recirculations the destruction of the recirculations by the monsoon winds each autumn is also modeled this effort highlights the dominance of monsoon wind forcing in the south china sea s basin scale dynamics

interactions among the winter monsoon ocean eddy and ocean thermal front in the south china sea 1 sea surface temperature sst in boreal winter shows a robust feature of ocean front west of luzon island where a cyclonic ocean eddy is associated with the winter northeast monsoon our analyses further show that cold warm water is located in the northwest southeast part of the luzon eddy due to ocean advection forming the west luzon front the results suggest a novel mechanism of the positive feedback among the winter monsoon ocean eddy and ocean front over the south china sea a strong positive wind stress curl associated with the winter monsoon and mountainous islands produces the luzon eddy with eddy heat advection the luzon eddy is accompanied by negative positive sst anomalies in the northwest southwest part of the eddy inducing the west luzon thermal front the sst anomalies can further force an anomalous wind pattern that converges onto the positive sst anomalies and diverges from the negative sst anomalies the anomalous wind distribution in turn enhances the positive wind stress curl west of luzon island

an open ocean forcing in the east china and yellow seas 1 recent studies have demonstrated that the annual mean barotropic currents over the east china and yellow seas ecys are forced primarily by the oceanic circulation in the open ocean basin through the kuroshio current kc the western boundary current of the subtropical gyre in the north pacific ocean the local wind stress forcing plays an important but secondary role those previous results were mainly qualitative and from a simple barotropic model forced by a steady wind stress field they remain to be tested in a more complete 3 d model with both wind stress and buoyancy fluxes in addition the seasonal variability of major ecys currents may involve different forcing mechanisms than their annually averaged fields do and this can only be addressed when a seasonally varying forcing is used in the model in this paper we will address these issues by using a 3 d baroclinic model our results confirm the finding from the previous studies that the kc is the primary forcing mechanism for major annually mean currents in the ecys which include the taiwan strait current the tsushima warm current and the yellow sea warm current yswc etc however the local monsoonal forcing plays a prominent role in modulating the seasonal variability of all major currents in the region a deep northwestward intrusion of the yswc in winter for instance is mainly due to a robustly developed china coastal current and korea coastal current which draw water along the yellow sea trough to feed the southward flows along the west and east coasts of the yellow sea

radiocarbon chronology of lake bonneville eastern great basin usa abstract lake bonneville occupied a series of connected topographically closed structural basins in the eastern great basin from about 30 ka to 12 ka the following synthesis of lake bonneville history is based on a critical evaluation of the stratigraphic and geomorphic contexts of 83 radiocarbon ages of a variety of samples including wood charcoal dispersed organic matter mollusk shells and tufa the lake began to rise from levels close to average holocene levels after about 28 ka by 22 ka it had transgressed approximately 100 m between 22 and 20 ka it regressed about 45 m in the stansbury oscillation and the stansbury shoreline was formed transgression after 20 ka proceeded in two phases a rapid phase from 20 to 18 ka and a slower phase from 18 to 15 ka the lake overflowed intermittently at its highest level the bonneville shoreline from about 15 to 14 5 ka then catastrophically dropped 100 m during the bonneville flood to the level of the provo shoreline which it occupied until about 14 ka subsequent closed basin regression was rapid and complete by 12 ka and was followed by a modest transgression to form the gilbert shoreline between 10 9 and 10 3 ka the lake bonneville record is an accurate proxy of the changing water balance in the bonneville basin during the late pleistocene although the nature of the climatic changes during this period are still uncertain

typhoon kai tak an ocean s perfect storm an unusually intense sea surface temperature drop dsst of about 10 88c induced by the typhoon kaitak is observed in the northern south china sea scs in july 2000 observational and high resolution scs model analyses were carried out to study the favorable conditions and relevant physical processes that cause the intense surface cooling by kai tak upwelling and entrainment induced by kai tak account for 62 and 31 of the dsst respectively so that upwelling dominates vertical entrainment in producing the surface cooling for a subcritical storm such as kai tak however wind intensity and propagation speed alone cannot account for the large dsst prior to kai tak the sea surface was anomalously warm and the main thermocline was anomalously shallow the cause was a delayed transition of winter to summer monsoon in the northern scs in may 2000 this produced an anomalously strong wind stress curl and a cold eddy capped by a thin layer of very warm surface water west of luzon kai tak was the ocean s perfect storm in passing over the eddy at the right time producing the record sst drop and high chlorophyll a concentration

determination of the dissolved anion composition of ancient lakes from fossil ostracodes the mineralogy of evaporite and other precipitated minerals together with geochemical studies has provided traditional sources of information about the major dissolved ion composition solutes of ancient lakes the paleocompositional resolving power of these methods is generally greatest in high salinity lakes that precipitate numerous solute sensitive evaporite minerals as opposed to dilute saline lakes that precipitate only a few minerals ostracodes live in dilute saline lakes where a species occurrence is determined by the relative proportions of the lake s major dissolved anions so that each species describes specific areas on an anion trilinear diagram moreover the upper salinity tolerance of each species appears to depend upon the types of major anions in solution and is therefore anion specific knowledge about both anion and anion salinity tolerances of an ostracode may ultimately provide a means of estimating absolute anion concentrations in paleolakes because ostracodes are common fossils in lake sediments they provide an important new source of original paleocompositional information suitable for many geologic climatic geochemical and paleontologic studies

lake bonneville fluctuations and global climate change lake bonneville the largest late pleistocene closed basin lake in the north american great basin fluctuated widely in response to changes in climate the geochemistry and mineralogy of endogenic calcium carbonate deposited in deep water and stratigraphic studies of shore zone deposits provide evidence of millennial scale lake level fluctuations that had amplitudes of about 50 m between 30 and 10 ka falling lake events occurred at 21 18 5 19 17 5 16 15 5 14 13 and 10 ka radiocarbon years synchronously with the terminations of heinrich events h1 and h2 and other smaller scale iceberg rafting events a b c and younger dryas in the north atlantic ocean the lake bonneville results thus support other climate records that suggest that late pleistocene millennial scale climate change was global in extent the size and shape of the northern hemisphere ice sheets which determined the mean positions of storm tracks may have been the primary control on late pleistocene water budgets of great basin lakes

summer upwelling in the south china sea and its role in regional climate variations seasonal and interannual variations of summer upwelling off the south vietnam coast and the offshore spread of cold water are investigated using a suite of new satellite measurements in summer as the southwesterly winds impinge on annam cordillera a north south running mountain range on the east coast of indochina a strong wind jet occurs at its southern tip offshore east of saigon resulting in strong wind curls that are important for ocean upwelling off the coast in july and august an anticyclonic ocean eddy develops to the southeast advecting the cold coastal water offshore into the open south china sea scs the center of this cold filament is located consistently north of the wind speed maximum indicating that open ocean upwelling helps to cool the ocean surface corroborating evidence for the cold filament is found in ocean color observations that reveal a collocated tongue of high chlorophyll concentration the development of this cold filament disrupts the summer warming of the scs and causes a pronounced semiannual cycle in sst moreover the cold filament is an important player in interannual variability in the summer scs in 1998 the cold filament and mid summer cooling never took place giving rise to a strong basin wide surface warming interannual sst variance has a local maximum over the climatological cold filament and is much greater than the variance over the adjacent indian and western pacific oceans a cold filament index is constructed which displays significant lagged correlation with sst in the eastern equatorial pacific and indian oceans indicative of a teleconnection from el nino

mesoscale eddies in the south china sea mean properties spatiotemporal variability and impact on thermohaline structure we investigated mean properties and the spatiotemporal variability of eddies in the south china sea scs by analyzing more than 7000 eddies corresponding to 827 eddy tracks identified using the winding angle method and 17 years of satellite altimetry data eddies are mainly generated in a northeast southwest direction and southwest of luzon strait there is no significant difference between the numbers of two types of eddies anticyclonic and cyclonic in most regions the mean radius and lifetime of eddies are 132 km and 8 8 weeks respectively both depending on where the eddies are formed anticyclonic and cyclonic eddies tend to deform during their lifetimes in different ways furthermore eddy propagation and evolution characteristics are examined in the northern scs eddies mainly propagate southwestward along the continental slope with velocities of 5 0 9 0 cm s 1 while in the central scs eddies tend to move with slight divergence but still in a quasi westward direction with velocities of 2 0 6 4 cm s 1 eddy propagation in the western basin to the east of vietnam is quite random with no uniform propagate direction investigation of 38 long lived eddies shows that eddies have a swift growing phase during the first 12 weeks and then a slow decaying phase that affects the eddy radii and eddy energy densities nevertheless vorticity has less variability in addition the effect of eddies on the thermocline and halocline is analyzed using 763 argo temperature profile data cyclonic eddies drive the thermocline shallower and thinner and significantly strengthen the thermocline intensity whereas anticyclonic eddies cause the thermocline to deepen and thicken and weaken the thermocline intensity to a certain degree the halocline impacted by cyclonic eddies is also shallower and thinner than that impacted by anticyclonic eddies finally eddy temporal variations are examined at seasonal and interannual scales eddy activity is sensitive to the wind stress curl and in the northern scs it is also related with the strength of the background flows

nonlinear multiscale interactions and internal dynamics underlying a typical eddy shedding event at luzon strait eddy shedding is a highly nonlinear process that presents a major challenge in geophysical fluid dynamics using the newly developed localized multiscale energy and vorticity analysis ms eva this study investigates an observed typical warm eddy shedding event as the kuroshio passes the luzon strait in order to gain insight into the underlying internal dynamics through multiscale window transform mwt it is found that the loop form kuroshio intrusion into the south china sea scs is not a transient feature but a quasi equilibrium state of the system a mesoscale reconstruction reveals that the eddy does not have its origin at the intrusion path but comes from the northwest pacific it propagates westward preceded by a cyclonic cold eddy through the kuroshio into the scs as the eddy pair runs across the main current the cold one weakens and the warm one intensifies through a mixed instability in its development another cold eddy is generated to its southeast which also experiences a mixed instability it develops rapidly and cuts the warm eddy off the stream both the warm and cold eddies then propagate westward in the form of a rossby wave first baroclinic mode as the eddies approach the dongsha islands they experience another baroclinic instability accompanied by a sudden accumulation of eddy available potential energy this part of potential energy is converted to eddy kinetic energy through buoyancy conversion and is afterwards transferred back to the large scale field through inverse cascading greatly reducing the intensity of the eddy and eventually leading to its demise this article is protected by copyright all rights reserved

progress on the formation dynamics of the layered circulation in the south china sea abstract in the south china sea scs an alternating cyclonic anticyclonic cyclonic cac circulation is recognized in the upper middle deep layers based on the principle of stokes theorem the cac circulation is driven extrinsically by the east asia monsoonal winds a vertical sandwich like inflow outflow inflow through luzon strait ls and intrinsically by the slope current topography interaction the understandings on the formation mechanisms of cac circulation have been achieved based on different principles and the physically solid interpretation on the cac circulation need to be further clarified in this paper we review different dynamic perspectives from recent researches that describe the combined effects of surface wind forcing lateral external forcing and the intrinsic coupling among different layers our aim is to obtain a consistent understanding of the dynamics of the circulation in the scs the cac circulation forms largely from the planetary vorticity flux that is extrinsically induced by the inflow outflow inflow through ls which is predominantly balanced by the interaction between the cac flow and bottom topography inside basin the vertical motion dynamically links the circulation in three layers and its spatial pattern has a strong impact on the basin circulation particularly in the middle and deep layers vertical coupling of the layers occurs mainly over the slope because of the cross slope motion due to interaction between strong slope current and topography the internal layered circulation and intensified mixing in turn affect and maintain the layered current structure in ls based on the review of the forcing mechanisms we offer perspectives for further investigations

a three layer alternating spinning circulation in the south china sea abstractunderstanding of the three dimensional circulation in the south china sea scs is crucial for determining the transports of water masses energy and biogeochemical substances in the regional and adjacent larger oceans the circulation s kinematic and dynamic natures however are largely unclear results from a three dimensional numerical ocean circulation model and geostrophic currents derived from hydrographic data reveal the existence of a unique three layer cyclonic anticyclonic cyclonic cac circulation in the upper 1500 m layers in the scs with differing seasonality an inflow outflow inflow structure in luzon strait largely induces the cac circulation which leads to vortex stretching in the scs basin because of a lateral planetary vorticity flux in each of the respective layers the formation of joint effects of baroclinicity and relief jebar is an intrinsic dynamic response to the cac circulation the jebar arises from the cac flow topog

imprint of the pacific decadal oscillation on the south china sea throughflow variability abstractanalysis of the 62 yr hindcast outputs from an eddy resolving ocean general circulation model reveals a prominent decadal variability in the upper layer 0 745 m luzon strait transport lst a key component of the south china sea throughflow this variability is in phase with the basin scale wind stress anomalies associated with the pacific decadal oscillation pdo a composite analysis shows that during the positive phase of the pdo the aleutian low and its related positive wind stress curl anomalies intrude southward reducing the trade winds and enhancing the westerly wind anomalies in the tropical north pacific in response the north equatorial current bifurcation shifts northward resulting in a weaker kuroshio east of luzon and consequently a stronger south china sea throughflow in the upper 745 m

pluvial lakes in the great basin of the western united states a view from the outcrop abstract paleo lakes in the western united states provide geomorphic and hydrologic records of climate and drainage basin change at multiple time scales extending back to the miocene recent reviews and studies of paleo lake records have focused on interpretations of proxies in lake sediment cores from the northern and central parts of the great basin in this review emphasis is placed on equally important studies of lake history during the past 30 years that were derived from outcrop exposures and geomorphology in some cases combined with cores outcrop and core records have different strengths and weaknesses that must be recognized and exploited in the interpretation of paleohydrology and paleoclimate outcrops and landforms can yield direct evidence of lake level facies changes that record details of lake level fluctuations and geologic events such as catastrophic floods drainage basin changes and isostatic rebound cores can potentially yield continuous records when sampled in stable parts of lake basins and can provide proxies for changes in lake level water temperature and chemistry and ecological conditions in the surrounding landscape however proxies such as stable isotopes may be influenced by several competing factors the relative effects of which may be difficult to assess and interpretations may be confounded by geologic events within the drainage basin that were unrecorded or not recognized in a core the best evidence for documenting absolute lake level changes lies within the shore nearshore and deltaic sediments that were deposited across piedmonts and at the mouths of streams as lake level rose and fell we review the different shorezone environments and resulting deposits used in such reconstructions and discuss potential estimation errors lake level studies based on deposits and landforms have provided paleohydrologic records ranging from general changes during the past million years to centennial scale details of fluctuations during the late pleistocene and holocene outcrop studies have documented the integration histories of several important drainage basins including the humboldt amargosa owens and mojave river systems that have evolved since the miocene within the active tectonic setting of the great basin these histories have influenced lake levels in terminal basins many pre late pleistocene lakes in the western great basin were significantly larger and record wetter conditions than the youngest lakes outcrop based lake level data provide important checks on core based proxy interpretations we discuss four such comparisons in some cases such as for lakes owens and manix outcrop and core data synthesis yields stronger and more complete records in other cases such as for bonneville and lahontan conflicts point toward reconsideration of confounding factors in interpretation of core based proxies

the south china sea throughflow retrieved from climatological data abstract the salinity distribution in the south china sea scs has a pronounced subsurface maximum from 150 220 m throughout the year this feature can only be maintained by the existence of a mean flow through the scs consisting of a net inflow of salty north pacific tropical water through the luzon strait and outflow through the mindoro karimata and taiwan straits using an inverse modeling approach the authors show that the magnitude and space time variations of the scs thermohaline structure particularly for the salinity maximum allow a quantitative estimate of the scs throughflow and its distribution among the three outflow straits results from the inversion are compared with available observations and output from a 50 yr simulation of a highly resolved ocean general circulation model the annual mean luzon strait transport is found to be 2 4 0 6 sv sv 106 m3 s 1 this inflow is balanced by the outflows from the karimata 0 3 0 5 sv mindoro 1 5 0 4 and taiwan 0 6 0 5 sv str

radiocarbon dating of pollen by accelerator mass spectrometry radiocarbon dating of bulk sediments has been the standard method for establishing chronologies in the studies of lake sediment cores which have contributed significantly to our knowledge of late quaternary paleo environments these bulk sediment dates are presumed to be direct ageindicators for the speciments e g pollen or macrofossils which are actually being studied however several recent studies have reinforced long standing apprehensions concerning this presumption in this study we demonstrate for the first time the radiocarbon dating of pollen concentrate samples by accelerator mass spectrometry the dates obtained by this method should provide more reliable radiocarbon chronologies for paleo environmental studies than have been obtainable by bulk sediment dating