cooling trend over the past 4 centuries in northeastern hong kong waters as revealed by alkenone derived sst records abstract the climate history over the past few centuries is important to be used to assess how regional climate responds to global forcing here we report three high resolution alkenone based sea surface temperature sst records over the past 4 centuries from three sediment cores collected in the mirs bay northeastern hong kong all three sst records consistently show a general cooling trend toward the present with most of cooling occurring over the last century alkenone derived sst values stayed around 26 5 27 c at the three sites prior to 1900s and decreased into the range of 25 26 c the magnitude of cooling approximately from the little ice age lia to present tends to be dampened from 2 c nearshore to 1 c offshore the cooling trend as identified in all three sst records is thus opposite to the global temperature rise over the last century assisted with modern observations we interpret that the alkenone derived sst reflects increasing upwelling in the mirs bay which likely results from the strengthened east asian summer monsoon in the context of global warming over the last century

late quaternary environmental changes in the pearl river mouth region china abstract this study presents findings concerning late quaternary environmental changes in the pearl river mouth region china based on the study of over 300 boreholes out of these 35 boreholes are selected for the reconstruction of transects across the deltaic plain and estuary 39 radiocarbon dates obtained from these boreholes are used to help define the chronology of stratigraphic units present including two terrestrial units t1 and t2 and two marine units m1 and m2 diatom assemblages are studied in 6 boreholes revealing similarities and differences between the two marine units before the area was inundated by the last interglacial sea mis 5 an older terrestrial unit of sand and gravel t2 was laid down in a number of palaeo valleys during the last interglacial period an older marine unit of silt and clay m2 was laid down which was subsequently subaerially exposed when sea level regressed during the last glacial period mis 4 2 causing the uppermost section to be weathered during the same period a younger terrestrial unit of sand and gravel t1 was deposited along palaeo river channels around the early holocene before 8 2 cal ka bp the postglacial rise in sea level initiated a new phase of sedimentation in the outer part of the estuary characterised by the high percentages of marine diatoms in the sediments in the early holocene strong monsoon freshwater discharge resulted in sedimentation of a fine sand layer in the inner part of the estuary after 8 2 cal ka bp rapid rises in sea level caused widespread marine inundation and sedimentation the diatom data suggest that the relative sea level associated with the m2 and m1 units were both at similar levels because the m2 unit is typically recorded at altitudes of 15 m and 20 m below the present sea level this is likely to be a result of long term subsidence although numerical dating of the pre m1 units has not been made in the present study the chronology of these units can be inferred from uranium series ages and optically stimulated luminescence dating obtained from the adjacent coastal waters of hong kong the t1 unit has yielded ages of about 30 0 cal ka bp while the m2 unit has yielded ages about 130 0 cal ka bp confirming their mis 4 2 and mis 5 ages respectively

atmospheric oxygen 18 and sea level changes past isotopic composition of atmospheric oxygen 18oatm can be inferred from the analysis of air bubbles trapped in ice caps the longest record covers the last 420 ka thousand of years at the vostok site in east antarctica it shows a strong modulation by the precession and striking similarities but also noticeable differences with the deep sea core oxygen 18 record from which changes in the oxygen content of sea water 18osw and in sea level can be derived indeed 18oatm is driven by complex fractionation processes occuring during respiration and photosynthesis both 18oatm and its difference with respect to 18osw the dole effect are influenced by factors such as the ratio of oceanic and terrestrial productivities which may have significantly changed between different climates also the response time of 18oatm to oceanic changes should be taken in consideration but this parameter itself depends on biospheric activity we review the various aspects of the link between the 18oatm and the 18osw signals we also examine the approach followed by shackleton science 2000 for deriving sea level change from the 18oatm vostok record assuming that the phase between this record and insolation changes is constant and that the dole effect is a fraction of the precessional component of the 18oatm signal glaciological constraints on the vostok chronology and the complexity of the dole effect show that those two assumptions are quite probably too simplistic

a 4 ma record of thermal evolution in the tropical western pacific and its implications on climate change article i nfo orbital resolution thermal histories over the last 4 ma at odp site 1143 in the tropical western pacific are reconstructed using alkenone paleothermometry the temperature profile is characterized by a steady state of 29 c with fluctuations b1 c before 2 7 ma and by a strong oscillating state from 2 7 ma largely due to cooling by up to 4 c from 29 c in interglacial to 26 c in glacial intervals this implies a relative warm and stable surface hydrography during the early and mid pliocene in this region influenced by the warm pool before temperature decreases in responding to global cooling and the formation of the distinct glacial stages since the late pliocene therefore the smaller sst gradient between tropical eastern and western pacific and between southern and northern south china sea before the late pliocene indicates a super sized pliocene pacific warm pool while the larger sst gradient since then marks progressively intensification of the zonal walker circulation and meridional hadley circulation representing the monsoon circulations in the region the intensification of the walker and hadley circulations over the tropical pacific may also have helped on the onset of glaciations and subsequent deglaciations during the late pliocene and pleistocene 2011 published by elsevier b v

sea levels during late marine isotope stage 3 or older reported from the red river delta northern vietnam and adjacent regions abstract a 60 m long sediment core from the lower red river delta in northern vietnam contains three depositional sequences consisting mostly of regressive shallow marine sediments bounded by unconformities the youngest unit represents the modern red river delta the second unit a facies succession comparable to the overlying deltaic succession formed during an earlier sea level highstand as indicated by the marine isotope stage mis 3 age obtained by radiocarbon dating the third undated unit might reflect earlier high sea levels of the middle to late pleistocene the mis 3 ages derived from shoreline related sedimentary facies are supported by records from adjacent mega deltas and shelf sites with paleoshoreline facies proximal sites from the central indochina craton show high sea levels during late mis 3 whereas distal sites from the open continental shelf indicate much lower sea levels at the same time independent globally relevant sea level reconstructions suggest that both positions have been affected by later vertical movement this discrepancy between sea level records from central cratonic sites and the continental margin can be explained by a balanced response to locally differentiated sediment loading and compaction on the shelf as is supported by published seismic data however if the complete set of radiocarbon dates is contaminated by younger material then the second recorded sea level highstand may be associated with mis 5 as no marine deposits have yet been reported in any of the three indochinese mega deltas for this time interval

the environmental conditions of mis5 in the northern south china sea revealed by n alkanes indices and alkenones from a 39 m long sediment sequence abstract in order to reconstruct the environmental conditions of marine isotope stage mis 5 in the coastal area of northern south china sea a sediment core was collected from the south coast of hainan island 18 16 57 n 109 42 38 e from which a thick marine mud unit 39 m is found to be the deposit of mis 5 according to the high abundance of alkenones the thick mud sequence was deposited under marine conditions the high toc and n alkanes concentrations as normalized to toc suggest this was a period of high organic matter om production and the majority of om came from terrestrial vascular plant sources comparatively short chain n alkanes c 18 22 and proportion of aquatic plant index p aq in the lower sub unit appear higher than those in the middle and upper sub units suggesting a gradual increase in terrestrial om supply throughout mis 5e the carbon preference index in long chain n alkanes cpi 25 33 implies high precipitation and or temperature in this interval whilst the average carbon length index in long chain n alkanes acl 25 33 indicates a warm climate during mis 5e

evidence for obliquity forcing of glacial termination ii variations in the intensity of high latitude northern hemisphere summer insolation driven largely by precession of the equinoxes are widely thought to control the timing of late pleistocene glacial terminations however recently it has been suggested that changes in earth s obliquity may be a more important mechanism we present a new speleothem based north atlantic marine chronology that shows that the penultimate glacial termination termination ii commenced 141 000 2500 years before the present too early to be explained by northern hemisphere summer insolation but consistent with changes in earth s obliquity our record reveals that terminations i and ii are separated by three obliquity cycles and that they started at near identical obliquity phases

offshore quaternary sediments and their engineering significance in hong kong yim w w s 1994 offshore quaternary sediments and their engineering significance in hong kong in e f j de mulder editor engineering geology of quaternary deposits eng geol 37 31 50 investigation works undertaken for coastal engineering projects in hong kong has provided abundant information on the quaternary sedimentary sequence beneath the sea floor although the significance of such information may not have been realized at the time of these projects valuable lessons have often been learnt afterwards some examples of the important engineering applications concerning offshore quaternary sediments include 1 the provision of information on water movement sediment transport and sedimentation rates during the holocene period 2 the identification of exploitable offshore sand and gravel resources 3 the interpretation of marine geophysical data through the availability of reliable borehole descriptions 4 the enhancement of engineering soil testing results and their interpretation 5 the prediction of rates of long term ground settlement in coastal land reclaimations 6 the selection of offshore sites for waste disposal 7 the reduction in cost of coastal engineering projects through choosing the most cost effective site 8 the provision of baseline data to assist environmental impact assessment a new geological model is proposed for the offshore quaternary sedimentary sequence of hong kong the engineering properties of the sediments are found to be closely related to the palaco environmental changes

was there an abrupt cold climatic event in the middle eemian pollen record from a palaeolake at the hieronimowo site ne poland abstract seventy samples of lacustrine sediments from a palaeolake at the hieronimowo site ne poland were investigated by pollen analysis method the obtained results indicate that the examined sequence spans the whole eemian interglacial mis 5e the beginning of the early vistulian weichselian mis 5d and some undefined period of the plenivistulian middle weichselian mis 2 4 the specific feature of the studied profile is the great thickness of deposits representing the hornbeam phase of the eemian interglacial e5 r paz which was the younger part of the climatic optimum of this interglacial and the very well developed pollen record of this phase that is absent in other profiles in ne poland due to this our study allowed for the first time in ne poland the detailed reconstruction of changes in the vegetation and in the mean january and july temperature during the middle part of the eemian interglacial this reconstruction unequivocally rules out the existence of an abrupt short lasting cold event at that time only a gradual slight increase in temperature was apparent during the older part of the hornbeam phase to 21 c for july and to 0 c for january and gradual decrease during its younger part to 17 c for july and to 5 c and

evolution of the lian river coastal basin in response to quaternary marine transgressions in southeast china abstract the coastal basin deposit in the lian river plain is among the thickest quaternary sequences along the southeastern coast of china the clastic sediment accumulated in a variety of environmental settings including fluvial channel estuary coastal and marine conditions detailed investigation of lithofacies grain size distributions magnetic susceptibility microfossils and chronology of marine core cn01 compared with regional cores and combined with offshore seismic reflection profiles has allowed us to correlate the spatial stratigraphy in the inner and outer plain and the seismic units grain size distribution analysis of core cn 01 through compositional data analysis and multivariate statistics were applied to clastic sedimentary facies and sedimentary cycles results show that these methods are able to derive a robust proxy information for the depositional environment of the lian river plain we have also been able to reconstruct deltaic evolution in response to marine transgressions on the basis of dating results and chronostratigraphy the estimated age of the onset of deposition in the lian river coastal plain was more than 260 kyr bp three transgressive sedimentary cycles revealed in many regional cores support this age model detailed lithological and microfossil studies confirm that three marine m3 m2 and m1 and three terrestrial t3 t2 and t1 units can be distinguished spatial correlation between the inner plain outer plain typical cores characterized by marine transgression cycles and offshore seismic reflectors reveals coherent sedimentary sequences two major boundaries unconformity and erosion surfaces can be recognized in the seismic profiles and these correspond to weathered reddish and or variegated clay in the study core suggesting that quaternary sediment changes on the lian river plain were largely controlled by sea level variations and coastline shift during glacial interglacial cycles

mineralogical characterization of protolith and fault rocks from the safod main hole 1 washed cuttings provide a continuous record of the rocks encountered during drilling of the main hole of the san andreas fault observatory at depth safod both protolith and fault rocks exhibit a wide variety of mineral assemblages that reflect variations in some combination of lithology p t conditions deformation mechanisms and fluid composition and abundance regions of distinct neomineralization bounded by faults may record alteration associated with fluid reservoirs confined by faults in addition both smectites occurring as mixed layer phases and serpentine minerals are found in association with active strands of the san andreas fault that were intersected during drilling although their rheological influence is not yet fully known faults containing these mineralogical phases are prime candidates for continuous coring during phase 3 of safod drilling in the summer of 2007

four climate cycles of recurring deep and surface water destabilizations on the iberian margin centennial climate variability over the last ice age exhibits clear bipolar behavior high resolution analyses of marine sediment cores from the iberian margin trace a number of associated changes simultaneously proxies of sea surface temperature and water mass distribution as well as relative biomarker content demonstrate that this typical north south coupling was pervasive for the cold phases of climate during the past 420 000 years cold episodes after relatively warm and largely ice free periods occurred when the predominance of deep water formation changed from northern to southern sources these results reinforce the connection between rapid climate changes at mediterranean latitudes and century to millennial variability in northern and southern polar regions

eemian interglacial reconstructed from a greenland folded ice core efforts to extract a greenland ice core with a complete record of the eemian interglacial 130 000 to 115 000 years ago have until now been unsuccessful the response of the greenland ice sheet to the warmer than present climate of the eemian has thus remained unclear here we present the new north greenland eemian ice drilling neem ice core and show only a modest ice sheet response to the strong warming in the early eemian we reconstructed the eemian record from folded ice using globally homogeneous parameters known from dated greenland and antarctic ice core records on the basis of water stable isotopes neem surface temperatures after the onset of the eemian 126 000 years ago peaked at 8 4 degrees celsius above the mean of the past millennium followed by a gradual cooling that was probably driven by the decreasing summer insolation between 128 000 and 122 000 years ago the thickness of the northwest greenland ice sheet decreased by 400 250 metres reaching surface elevations 122 000 years ago of 130 300 metres lower than the present extensive surface melt occurred at the neem site during the eemian a phenomenon witnessed when melt layers formed again at neem during the exceptional heat of july 2012 with additional warming surface melt might become more common in the future

coastal quaternary morphologies on the northern coast of the south china sea china and their implications for current tectonic models a review and preliminary study marine terraces tidal notches and sediments along a 1200 km long stretch of the northern coast of the south china sea passive margin were studied and divided into five areas with varying tectonic characters up to three marine terraces occur that have elevations reaching up to 60 m above mean sea level amsl and two marine notches occur up to 11 m amsl chronology of the morphologies and deposits was obtained mainly by comparison with quaternary sea levels derived from the oxygen isotope curve however prior to the last interglacial highstand mis 5e c 125 ka evidence of history of events is less well constrained leading to less precision on sea level positions prior to mis 5e using the morphological features of mis 5e as a marker mean coastal uplift rates in the last c 125 ka range from 0 07 mm yr to 0 18 mm yr the pattern of deformations is slightly higher than those observed on passive margin coasts in other parts of the world the cause of uplift of the south china coastline is not clear but may relate to the himalayan collision zone or any other large scale phenomena

solar locked and geographical atmospheric structures inferred from a venus general circulation model with radiative transfer abstract solar locked and geographical atmospheric structures of daily averaged wind and temperature on venus were investigated using an atmospheric general circulation model with venusian topography and a two stream radiative code and were compared with wind fields obtained from the akatsuki ultraviolet imager the horizontal wind fields simulated around the subsolar region are similar to the observed ones at the cloud top mid latitude jets of 120 m s 1 and an equatorial fast flow of 90 m s 1 are formed around the cloud top a poleward flow of 8 m s 1 is formed above the cloud layer where solar heating is strong around the cloud top a poleward flow of 1 m s 1 is confined within the equatorward flank of the jet core whereas an indirect circulation is formed in the jet core by the eddy heat fluxes owing to the thermal tide and baroclinic waves in solar fixed coordinates the subsolar to antisolar circulation is predominant around the cloud top thus differences are significant between the zonal and dayside averages of the meridional wind and its related fluxes within the cloud layer this suggests the zonal mean meridional wind of the hadley circulation eddy momentum and heat fluxes from the one side hemisphere must be estimated carefully in the experiment including topography a near surface subrotation is formed in latitudinal zones over high land and mountains a weakly stable layer is formed at 10 20 km at low latitudes and the zonal wind is weakened at the cloud top over the aphrodite terra regional stationary modification of the atmospheric structure due to topographical waves appears in the cloud layer

high resolution uk 37 temperature reconstructions in the south china sea over the past 220 kyr past sea surface temperatures sst in the northern and southern areas of the south china sea have been reconstructed for the past 220 kyr using the uk37 alkenone index the sst profiles follow the glacial interglacial pattern exhibiting differences between last glacial maximum and holocene that are 1 3 c larger than those observed at the same latitudes in the atlantic and pacific oceans in termination i both planktonic foraminiferal 18o and sst exhibit well defined bolling allerod and younger dryas events with temperature differences between both periods of 0 8 and 0 4 c in north and south respectively ssts record a constant north south difference of 1 c in the interglacials and nearly 2 5 c in the glacial stages these differences define two distinct climatic and water circulation patterns that correspond with glacial interglacial sea level oscillations which opened and closed water exchange with the tropical indo pacific ocean through the present sunda shelf

radiocarbon dating and the reconstruction of late quaternary sea level changes in hong kong abstract radiocarbon dating is used widely for the reconstruction of late quaternary sea level changes in the present study eight case studies in hong kong have been chosen to highlight the difficulty in obtaining reliable radiocarbon dates pre holocene radiocarbon dates exceeding about 8100 yr bp have been found to show a young age bias a shell sample dated by two separate radiocarbon laboratories gave last interstadial ages differing by almost 9500 years while an oxygen isotope stage 5e age was obtained using uranium series dating other evidence including stratigraphy have shown that only the last interglacial age is acceptable the young age bias is attributed mainly to the post depositional introduction of young carbon into the sample for the reconstruction of sea level changes it is essential to select samples immediately above of the base of the holocene transgressive unit in offshore boreholes and excavations to satisfy the criteria of rapid burial these samples should preferably include mud plant matter and shells to facilitate interpretation furthermore as many samples as possible from a range of water depth down to about 130 m below the present sea level should be dated to reduce error introduced by counting statistics so the true signal of sea level changes can be reflected

magnetic enhancement is linked to and precedes hematite formation in aerobic soil 1 soil formation usually increases magnetic susceptibility most often by increasing the concentrations of magnetite and maghemite which are two ferrimagnetic iron oxides here we provide evidence that magnetic enhancement in aerobic soils not affected by detrital magnetic inputs or thermal transformation of other iron oxides is mostly due to the formation of maghemite which is later transformed into hematite the iron oxide that gives red color to soil we show that the maghemite hematite ratio is influenced by the particular environment and the degree of soil development so it constitutes an effective tool for paleoenvironmental and planetary studies

the local insolation signature of air content in antarctic ice a new step toward an absolute dating of ice records an accurate chronology of ice cores is still needed for interpreting the paleoclimatic record and to understand the relation between insolation and climate a new domain of research in this area has been stimulated by the work of m bender linking the record of n2 o2 ratio in the air trapped in the ice with the local insolation here we investigate the potential of the air content of polar ice v as another and complementary ice proxy of local insolation we propose that the long term changes in air content recorded in ice from the high antarctic plateau is dominantly imprinted by the local summer insolation the v measurements covering the last 440 000 yr and obtained along the epica dc edc ice core are presented 86 of the variance observed in the v record can be explained neither by air pressure nor by temperature changes and then should reflect properties influencing the porosity at close off other than temperature a wavelet analysis indicates a dominant obliquity period around 41 ka over the last 440 ka we propose a mechanism which can account for the observed anti correlation between local insolation and v and explain how the local insolation via the integrated summer insolation can affect the near surface snow structure and consequently the porosity at close off the v and the integrated summer insolation changes show high coherency over all the record and a variable phase relationship with a maximum phase difference of about 4000 yr around 200 ka ago the phase difference may reflect the difference between the edc2 chronology based on an inverse dating method and an accurately dated insolation curve our work by proposing a new and complementary ice proxy for local insolation should eventually contribute to the establishment of an absolute dating of the ice paleo record

osl dating of coastal sediments from the southwestern korean peninsula a comparison of different size fractions of quartz abstract the comparison of optically stimulated luminescence osl ages of different grain size fractions has given rise to conflicting results over recent years to test the reliability and validity of osl dating of fine and coarse grained fractions 25 samples were collected from a 46 m sediment core taken from the southwestern coast of korea which contained two typically fine grained tidal units separated stratigraphically by a coarse grained sand and gravel layer a single aliquot regenerative dose sar procedure was applied to chemically separated fine 4 11 m n 16 and coarse 90 212 m n 24 grained quartz the ages of coarse grained quartz in the upper unit were relatively consistent with those of fine grained quartz in the same unit of holocene age 12 0 ka in contrast in the lower unit the coarse quartz fraction osl ages are 30 60 mean 46 lower than the fine quartz fraction ages osl ages for all fine grained quartz in the lower unit 139 110 ka were in good agreement with the last interglacial sea level highstand marine isotope stage mis 5e however all osl ages for coarse grained quartz in this lower unit 90 45 ka were younger corresponding broadly to the last glacial period mis 4 and 3 osl ages obtained for fine grained quartz were in agreement with indirect age controls provided by lithological and palynological data implying that the use of the sar protocol to date fine grained quartz is appropriate for age control of coastal sediments extending to the last interglacial period the discrepancies between the ages of different grain size fractions may have arisen from early saturation of the natural signal and in some cases from contamination of the feldspar signal in the coarse quartz however more research is required to assess the reliability of osl ages for fine grained quartz obtained from the high dose linear region of the dose response curve

a millennial scale u37k sea surface temperature record from the south china sea 8 n over the last 150 kyr monsoon and sea level influence we report 150 kyr records of u37 sea surface temperature sst and carbonate content with 150 200 year sampling resolution from the southern south china sea scs in the northern margin of the western pacific warm pool wpwp using images core md972151 the glacial interglacial sst change is about 5 c for termination ii 23 5 to 28 5 c and 4 c for termination i 24 to 28 c the simultaneous rise of sea level and u37 sst during termination i suggests that sea level change has played an important role in the scs sst variability by influencing the exchange of tropical ocean warm surface water with the scs through the sunda shelf region sill depth 30 50 m when sea level drop was less than 30 m relative to today s md972151 sst was constantly above 27 c a situation which occurred during mis 5e part of mis5c and 5a and over the last 11 kyr sea level change was also the main control on carbonate content in the scs this was lower during low sea level stands due to the dilution effect of enhanced terrigenous inputs within the limitations of our age model millennial scale sst oscillations 1 5 c over a few hundred years occurred frequently during the entire glacial period correlating reasonably well with the hulu monsoon record from eastern china and the dansgaard oeschger d o cycles recorded for high latitude regions in the northern hemisphere such correlations suggest a possible teleconnection between higher latitude atmospheric forcing and low latitude climate oscillations in the western pacific tropical region via the asian monsoon system carbonate content also reveals millennial scale oscillations during the glacial period with higher content correlated with higher sst millennial scale fluctuations of sst and carbonate contents at this low latitude scs provide additional evidence that high frequency climate changes are global phenomena

the development of late holocene coastal cooling in the northern south china sea abstract paired high resolution sea surface temperature sst records based on the long chain alkenone unsaturation index u 37 k were reconstructed to decipher the sst evolution over the past 8000 years and its possible driving mechanisms at the hong kong coastal region the two sst records derived from a sediment core in the pearl river estuary and an offshore core in the northern south china sea scs show different patterns of sst changes the coastal record shows relatively stable warm temperatures during the mid holocene 7 4 2 6 ka and substantial cooling 2 c thereafter the cooling was most pronounced in the past 0 6 ka likely associated with the little ice age lia the offshore record generally reveals a warming trend from 8 ka to 3 5 ka and relatively warm temperatures since then as a result the sst difference sst between the two sites increased over time suggesting that the sst gradient gradually developed in the northern scs the declining coastal sst with the increasing sst likely indicates and results from the intensified east asian winter monsoon since 7 ka especially during the late holocene consistent with previous terrestrial records revealing winter monsoon variability and modern observations sst between coastal and offshore sites could thus be used as an indicator of winter monsoon variability

a critical review of marine sedimentaryδ13corg pco2 estimates new palaeorecords from the south china sea and a revisit of other low latitude δ13corg pco2 records in an attempt to understand better the local biogeochemistry of the south china sea scs and to unravel the contribution of this marginal low latitude basin to changes in atmospheric co2 concentrations we analyzed the carbon isotopic composition of organic matter 13corg in four sediment cores from throughout the scs covering the last 220 kyr higher values around 19 5 to 20 5 mark glacial stages while lower values around 21 to 22 5 are characteristic of interglacials following well established procedures the 13corg records are converted to local pco2 estimates on the basis of these and other low latitude 13corg pco2 estimates from the literature we present a critical evaluation of the use of 13c of bulk sedimentary organic matter to hindcast past changes in local co2 aq three crucial pitfalls are identified 1 given the present inability to quantify precisely the time varying amount of terrigenous corg input to marine sediments absolute values of pco2 estimates based on bulk sedimentary corg are questionable 2 none of the low latitude sedimentary 13corg pco2 records shows the expected correlation between temporal changes in upwelling intensity and co2 estimates most likely due to the antagonistic influences of co2 aq and phytoplankton growth rate on 13corg 3 a detailed comparison of marine 13corg pco2 records with the vostok co2 record reveals significant differences in phasing specifically at the end of the last deglaciation and during the oxygen isotope stage 5 4 transition however in areas where equilibrium between oceanic and atmospheric co2 occurs for example the scs and the mediterranean the timing of changes in 13corg should agree with the co2 record from ice cores if 13corg is a reliable proxy for changes in co2 aq taken together the compilation of records presented here cautions the use of 13corg as an unambiguous tracer of dissolved molecular co2 in the surface ocean and calls for a re evaluation of the role of the low latitude ocean on temporal changes in atmospheric co2

uk 37 temperature estimates from eemian marine sediments in the southern coast of hainan island tropical china abstract this study concerns high resolution sea surface temperature sst changes for the eemian interglacial period reconstructed from the southern coast of hainan island china the lower marine unit in the sediment core is composed of monotonous mud 31 m thick dated to be from the eemian interglacial period or lower part of marine isotope stage 5 mis 5 determined by optically stimulated luminescence osl the high sedimentation rate and the richness of organic matter and marine fossils provide good opportunity for the study of palaeo environments in the northern margin of the south china sea scs sediment grain size foraminifer sediment color index and long chain alkenone were used to reveal the near shore sedimentary environments and temperature at millennial scale specifically a high resolution uk 37 sst record was reconstructed for the eemian interglacial period the new evidence in northwestern margin of scs shows that the maximum value of sst during the eemian interglacial is approximately 29 c and the lowest is 26 5 c the trend of decreasing sst from 29 c throughout the marine sequence is consistent with the variations in sediment grain size reflecting the cooling trend of sst and sea level lowering tendency during the last interglacial period this new eemian sst result agrees with other records in the region of scs showing a coherent descending trend but spatial heterogeneity exists in timing and amplitude the insolation changes might be the main force for initiating the sst evolution during the penultimate interglacial period

optically stimulated luminescence dating of a danish eemian coastal marine deposit a test of accuracy abstract it is difficult to test convincingly luminescence dating techniques beyond the range of 14c and yet this is essential if claims that optically stimulated luminescence dating using quartz can reach back to beyond 105 years are to be given credence one possible approach is to use coastal marine sand identified as eemian by an examination of the palaeoecology the eemian period in northern europe is considered to last from 132 to 116 ka marine samples are likely to be linked most closely to at least part of this period and modern coastal sands are known to be well bleached thus from a luminescence dating perspective eemian marine sand can be considered to be of known age and it is very likely to be well bleached we have examined such a known age deposit on the east coast of jutland consisting of about 10 m of fine sand grading up from silty clays and clays in the lower part of the section this material is confidently expected to have been deposited during the very late saalian and early mid eemian 133 125 ka we report on the ages of 25 samples associated with this profile the observed overall precision is compared with the calculated precision on individual ages and the mean value of all the ages is compared with the expected mean of 130 ka

unusual c35 to c38 alkenones in mid holocene sediments from a restricted estuary charlotte harbor florida unusual c 35 to c 38 alkenones were identified in mid holocene 8 3 5 kyr bp sediments from a restricted estuary in southwest florida charlotte harbor the distribution was dominated by a c 36 diunsaturated omega 15 20 ethyl ketone identical to the one present in black sea unit 2 sediments other unusual alkenones were tentatively assigned as a c 35 2 omega 15 20 methyl ketone a c 37 2 omega 17 22 methyl ketone and a c 38 2 omega 17 22 ethyl ketone in late holocene sediments 3 5 kyr bp the common c 37 to c 39 alkenones were found compound specific c 14 c 13 and d isotope measurements were used to constrain the possible origin of the alkenones conventional radiocarbon ages of alkenones and higher plant derived long chain n alcohols indicated no significant difference in age between mid holocene alkenones and higher plant n alcohols both alcohols and alkenones were offset vs calibrated ages of shell fragments in the same sediment core which suggests they were pre aged by 500 800 yr implying resuspension and redistribution of the fine grained sedimentary particles with which they are associated the hydrogen isotopic delta d composition 190 parts per thousand to 200 parts per thousand of the c 37 and c 38 alkenones in the late holocene sediments is in line with values for coastal haptophytes in brackish water however the unusual c 36 and c 38 alkenones from the mid holocene sediments were enriched in d by ca 100 parts per thousand vs the late holocene alkenones also delta c 13 values of mid holocene alkenones were consistently offset compared with late holocene alkenones 21 parts per thousand to 22 parts per thousand and 22 parts per thousand to 23 parts per thousand respectively we suggest that the alkenones in charlotte harbor were produced by unknown alkenone producing haptophyte

pollen record in the northwestern continental shelf of the south china sea in the past 82 ka paleoenvironmental changes in the last glacial period abstract the northwestern continental shelf of the south china sea scs is in a geographic location that was sensitive to the global paleoenvironmental change during the last glacial period here we present a high resolution palynological record of core zbw 100 65 m in length from the continental shelf of the scs in the past 82 ka in contrast to results for the northern scs the core s pollen assemblage was dominated by arboreal trees between mis5a and mis1 even during the glacial period pollen provenance analyses indicated it was mainly from the drainage basin of the red river the yungui plateau and tibetan plateau between 66 and 64 ka the contribution of pinus fell while that of cyclobalanopsis and trilete spores increased indicating a drier and cooler climate conversely during mis3 the contributions of pinus and lowland trees were high indicating a warm and wet climate the sedimentary environment in core zbw alternated between coastal marine and river alluvial or shore facies a sedimentary hiatus between 42 and 13 ka coincided with a significant fall in sea levels seismic data indicate that the hainan paleo river delta hprd process occurred at the core site between 65 and 56 ka with extremely high rates of sediment deposition pollen data indicate the hprd process was coincided with a transition period from cooler and drier climate to warmer and wetter climate and lower sea levels to higher sea levels

holocene and eemian sea surface temperature trends as revealed by alkenone and mg ca paleothermometry in this study we review a global set of alkenone and foraminiferal mg ca derived sea surface temperatures sst records from the holocene and compare them with a suite of published eemian sst records based on the same approach for the holocene the alkenone sst records belong to the actualized ghost database kim j h schneider r r 2004 ghost global database for alkenone derived holocene sea surface temperature records available from http www pangaea de projects ghost while the mg ca derived sst database represents a new compilation the actualized ghost database not only confirms the sst changes previously described but also documents the holocene temperature evolution in new oceanic regions such as the northwestern atlantic the eastern equatorial pacific and the southern ocean a comparison of holocene sst records stemming front the two commonly applied paleothermometry methods reveals contrasting sometimes divergent sst evolution particularly at low latitudes where sst records are abundant enough to infer systematic discrepancies at a regional scale opposite sst trends at particular locations could be explained by out of phase trends in seasonal insolation during the holocene this hypothesis assumes that a strong contrast in the ecological responses of coccolithophores and planktonic foraminifera to winter and summer oceanographic conditions is the ultimate reason for seasonal differences in the origin of the temperature signal provided by these organisms as a simple test for this hypothesis eemian sst records are considered because the holocene and eemian time periods experienced comparable changes in orbital configurations but had a higher magnitude in insolation variance during the eemian for several regions sst changes during both interglacials were of a similar sign but with higher magnitudes during the eemian as compared to the holocene this observation suggests that the ecological mechanism shaping sst trends during the holocene was comparable during the penultimate interglacial period although this ecology hypothesis fails to explain all of the available results we argue that any other mechanism would fail to satisfactorily explain the observed sst discrepancies among proxies c 2010 elsevier ltd all rights reserved

last interglacial arctic warmth confirms polar amplification of climate change the warmest millennia of at least the past 250 000 years occurred during the last interglaciation when global ice volumes were similar to or smaller than today and systematic variations in earth s orbital parameters aligned to produce a strong positive summer insolation anomaly throughout the northern hemisphere the average insolation during the key summer months m j j was ca 11 above present across the northern hemisphere between 130 000 and 127 000 years ago with a slightly greater anomaly 13 over the arctic greater summer insolation early penultimate deglaciation and intensification of the north atlantic drift combined to reduce arctic ocean sea ice allow expansion of boreal forest to the arctic ocean shore across vast regions reduce permafrost and melt almost all glaciers in the northern hemisphere insolation amplified by key boundary condition feedbacks collectively produced last interglacial summer temperature anomalies 4 5 c above present over most arctic lands significantly above the average northern hemisphere anomaly the last interglaciation demonstrates the strength of positive feedbacks on arctic warming and provides a potentially conservative analogue for anticipated future greenhouse warming

late quaternary environmental changes in hong kong abstract the offshore quaternary deposits of hong kong include a wide range of clastic sediments that accumulated in a variety of settings including lacustrine channel overbank coastal and marine environments detailed studies of the sedimentology and diatoms of several long continuously sampled cores combined with seismic reflection profiles has enabled the reconstruction of late pleistocene and holocene palaeoenvironments in hong kong the quaternary sediments comprise several informal seismic units that are separated by marine planation tidal scour and fluvial erosion surfaces seismic unit 1 represents pre quaternary bedrock and weathered bedrock which is separated from a complex assemblage of pleistocene channel floodplain backswamp and lacustrine deposits seismic unit 2 by a major erosion surface u1 sediments that represent the basal part of unit 2 have been dated at about 248 000 yr b p well preserved laminations at several horizons suggest periodic deposition and probably seasonal flooding the presence of kaolin indicates strong chemical weathering and warm humid conditions at the time of deposition seismic unit 3 consists of marine mud that unconformably overlies a fluvial erosion surface fe1 cut into deposits represented by seismic unit 2 the sediments comprising unit 3 are tentatively correlated with oxygen isotope stage 5e and high sea levels at about 128 000 105 000 yr b p a marine planation surface r1 terminates unit 3 and is overlain by coastal and nearshore deposits comprising seismic unit 4 at about 95 000 to 80 000 yr b p this phase of marine deposition was terminated by a major fall in sea level that caused widespread fluvial incision across hong kong and produced surface fe2 a subsequent rise in sea level after about 18 000 yr b p led to deposition of a complex succession of marine sediments and erosion surfaces initially homogeneous mud seismic unit 5a was laid down tidal currents perhaps related to base level changes then caused incision and the formation of surface ts1 at several localities further shallow marine mud comprising unit 5b was laid down between about 9500 and 8000 yr b p a planar erosion surface r2 with local palaeosols and minor incision cuts across earlier deposits the overlying seismic unit 5c represents diatomaceous marine mud and a basal sand at one coring site these sediments have been divided into five major diatom zones that reflect changes in salinity and sea level modern sea level was attained by about 6000 yr b p in broad terms the late quaternary record is one of two periods of marine flooding separated by a major regressive episode with no evidence of older quaternary marine sediments being present

variation in cross sectional asymmetry of coarse bedload river channels alternative indices of cross section asymmetry are compared observed values of two preferred indices for 567 natural sections across eleven confined upland channels are predictably low along such low sinuosity reaches variation in asymmetry of sections located around confined unconfined but stable and freely migrating bends is evaluated consideration of the influence of bed topography emphasizes local plan curvature of bed forms as an important control on degree of asymmetry variation in indices for bed forms in similar planform locations indicates the levels of asymmetry at different stages of the transformation of channel geometry over time

abrupt temperature changes in the western mediterranean over the past 250 000 years a continuous high resolution western mediterranean sea surface temperature sst alkenone record spanning the past 250 000 years shows that abrupt changes were more common at warming than at cooling during marine isotope stage mis 6 sst oscillated following a stadial interstadial pattern but at lower intensities and rates of change than in the dansgaard oeschger events of mis 3 some of the most prominent events occurred over miss 5 and 7 after prolonged warm periods of high stability climate during the whole period was predominantly maintained in interglacial interstadial conditions whereas the duration of stadials was much shorter

alkenone and tetraether lipids reflect different seasonal seawater temperatures in the coastal northern south china sea abstract we examined the lipid based temperature proxies u 37 k and tex 86 h in five short sediment cores from the inner shelf of the northern south china sea and related them to local sea water temperature from the world ocean atlas woa database the u 37 k based temperature values are consistent with euphotic zone temperature in spring and summer when the southeast monsoon prevails and vertical stratification occurs in the water column whereas tex 86 h based temperature values reflect sea surface temperature in winter when the northeast monsoon prevails and vertical mixing occurs the different temperature signals between the tex 86 h and u 37 k proxies could be a result of differences in the growing season between the source organisms with alkenone producing haptophyte algae blooming in the warmer and nutrient rich season with higher fluvial influx and tetraether producing thaumarchaeota blooming in the cooler and oligotrophic season

palaeoclimatic signals recognized by chemometric treatment of molecular stratigraphic data abstract the high resolution stratigraphy of various marker compounds has been studied using gc hplc and gc ms in a 13 m gravity core recovered from the kane gap region eastern equatorial atlantic which provides a record of the glacial interglacial episodes over the last million years downhole variations in many presumed source specific components are observed e g in n alkanes from terrigenous land plants and dinosterol from dinoflagellates which may be due to perturbations or cyclicities resulting from climatic change fluctuations in the unsaturation of alkenones attributable to variations in water temperatures show correlations with the glacial interglacial cycles recorded in the 18 o values for planktonic foraminifera thereby providing a potential organic geochemical measure of past climates these molecular abundance data can be linked to the palaeotemperature record following computer treatments using principal component and spectral analyses molecular stratigraphy shows promise as a new chemostratigraphical tool where other means of stratigraphy fail for example through calcium carbonate dissolution

millennial scale trends in west pacific warm pool hydrology since the last glacial maximum models and palaeoclimate data suggest that the tropical pacific climate system plays a key part in the mechanisms underlying orbital scale and abrupt climate change atmospheric convection over the western tropical pacific is a major source of heat and moisture to extratropical regions and may therefore influence the global climate response to a variety of forcing factors the response of tropical pacific convection to changes in global climate boundary conditions abrupt climate changes and radiative forcing remains uncertain however here we present three absolutely dated oxygen isotope records from stalagmites in northern borneo that reflect changes in west pacific warm pool hydrology over the past 27 000 years our results suggest that convection over the western tropical pacific weakened 18 000 20 000 years ago as tropical pacific and antarctic temperatures began to rise during the early stages of deglaciation convective activity as inferred from oxygen isotopes reached a minimum during heinrich event 1 ref 10 when the atlantic meridional overturning circulation was weak pointing to feedbacks between the strength of the overturning circulation and tropical pacific hydrology there is no evidence of the younger dryas event in the stalagmite records however suggesting that different mechanisms operated during these two abrupt deglacial climate events during the holocene epoch convective activity appears to track changes in spring and autumn insolation highlighting the sensitivity of tropical pacific convection to external radiative forcing together these findings demonstrate that the tropical pacific hydrological cycle is sensitive to high latitude climate processes in both hemispheres as well as to external radiative forcing and that it may have a central role in abrupt climate change events

sedimentary responses to holocene sea level change in a shallow marine environment of southern china abstract this study has examined how the sedimentary processes in the prevalent non deltaic coastal marine environments along the southeast coast of china have responded to sea level change and other environmental drivers during the holocene three sediment cores collected from a shallow marine embayment of the lantau island hong kong on the northern coast of the south china sea were analyzed the results of particle size total organic carbon content organic carbon and nitrogen ratios organic carbon stable isotope ratios abundance of alkenones and radiocarbon dating of these cores have helped reconstruct the sedimentary history of this site this history shares the similarity in sedimentary processes within the deltaic environment for the early holocene because palaeo incised channels exist in both environments the first 1500 years of deposition involved rapid channel infill caused by the rapidly rising sea level and strong monsoon driven discharge this was followed by a period of decelerated sedimentation under strong marine influence as the sea flooded the wide accommodation space in the subsequent two millennia major differences between the two environmental settings occur in the past 7000 years vertical accretion was seen in the non deltaic coastal environment whilst lateral shoreline advance was the dominant process in the deltaic basin the progressively slowing down in sedimentation rate in the non deltaic site during the middle and late holocene was caused by the reduced monsoon discharge intensified disturbance from tropical cyclone activity and coastal currents

stratigraphy and optically stimulated luminescence dating of subaerially exposed quaternary deposits from two shallow bays in hong kong china episodes of subaerial exposure recorded in quaternary sedimentary sequences on continental shelves are indicators of sea level change in this study the quaternary superficial deposits from two shallow bays in hong kong are examined in order to identify the timing of such episodes two rotary boreholes in tai o bay penetrated a succession of marine and terrestrial deposits formed during the last four interglacial glacial cycles the interglacial periods and the glacial periods are found to be represented by siliciclastic dominated shallow marine estuarine deposits and colluvial alluvial fan deposits respectively an excavation of a coastal land reclamation in deep bay revealed holocene intertidal subtidal estuarine deposits overlying aeolian deposits of the last glacial age optically stimulated luminescence dating carried out has confirmed the last glacial age of the terrestrial unit unconformably overlain by the holocene marine unit but only minimum ages can be obtained from the pre last glacial terrestrial units in one of the tai o boreholes studied the density and moisture content distribution is found to reflect the episodes of subaerial exposure of the pre holocene interglacial marine units in the palaeo desiccated crusts of these units density increases through iron cementation resulting from acid sulphate soil development while moisture content decreases as a consequence of desiccation quaternary terrestrial deposits occurring on continental shelves are therefore datable to a greater degree of certainty than their subaerial counterparts

weakened yellow sea warm current over the last 2 3 centuries abstract variations of oceanic currents beyond the instrumental period are often difficult to characterize although sea surface temperature sst changes along current pathways could provide some indirect information here we reconstruct four u 37 k based annual sst records over the past 2 3 centuries from muddy areas in the yellow sea ys and the northern east china sea ecs to characterize the regional sst variation patterns and to assess whether such patterns could be used to infer current changes three offshore sites are located along the pathway of the yellow sea warm current yswc and an additional coastal site near the yangtze river mouth with the minimal yswc influence the records show ssts dropped 3 6 c over the last 2 3 centuries at the three offshore sites and a warming trend toward the present at the coastal site the cooling sst trend observed at the three offshore sites is at odds with the average northern hemisphere temperature and solar irradiance changes strongly suggesting that regional processes or drivers in the ys and northern ecs regions overturned the global temperature signal accordingly we propose that the yswc weakened over the last 2 3 centuries which might be linked to the east asian winter monsoon variability

sea level changes forced ice breakouts in the last glacial cycle new results from coral terraces abstract sea level cycles recorded by coral terraces at huon peninsula hp in papua new guinea match rapid climate changes that occurred between 30 000 and 65 000 years ago seen in greenland ice cores and marine sediments each cycle of 6000 7000 years ended with a sea level rise of 10 15 m lasting 1000 2000 years following a longer period of falling sea level precise dating shows that each rise corresponds to a heinrich episode of ice rafted detritus in north atlantic signalling massive ice outbreak from north america sea level may be the trigger that forced near synchronous breakouts of ice from north america and eastern greenland the hp sea level changes also correspond to similar cycles in benthic oxygen isotopes reported from the north atlantic which are too large to be explained entirely in terms of ice volumes jointly the sea level and isotope records suggest that the north atlantic deep ocean cooled as sea level fell and warmed as sea level rose in each 6000 year cycle

temporal and spatial structure of multi millennial temperature changes at high latitudes during the last interglacial the last interglacial lig 129e116 thousand of years bp ka represents a test bed for climate model feedbacks in warmer than present high latitude regions however mainly because aligning different palaeoclimatic archives and from different parts of the world is not trivial a spatio temporal picture of lig temperature changes is difficult to obtain here we have selected 47 polar ice core and sub polar marine sediment records and developed a strategy to align them onto the recent aicc2012 ice core chronology we provide the first compilation of high latitude temperature changes across the lig associated with a coherent temporal framework built between ice core and marine sediment records our new data synthesis highlights non synchronous maximum temperature changes between the two hemispheres with the southern ocean and antarctica records showing an early warming compared to north atlantic records we also observe warmer than present day conditions that occur for a longer time period in southern high latitudes than in northern high latitudes finally the amplitude of temperature changes at high northern latitudes is larger compared to high southern latitude temperature changes recorded at the onset and the demise of the lig we have also compiled four data based time slices with temperature anomalies compared to present day conditions at 115 ka 120 ka 125 ka and 130 ka and quantitatively estimated temperature uncertainties that include relative dating errors this provides an improved benchmark for performing more robust model data comparison the surface temperature simulated by two general circulation models ccsm3 and hadcm3 for 130 ka and 125 ka is compared to the corresponding time slice data synthesis this comparison shows that the models predict warmer than present conditions earlier than documented in the north atlantic while neither model is able to produce the reconstructed early southern ocean and antarctic warming our results highlight the importance of producing a sequence of time slices rather than one single time slice averaging the lig climate conditions

significant sst differences between peak mis5 and mis1 along the low latitude western north pacific margin abstract the peak period of marine isotope stage 5 mis5e is the most recent warm period largely comparable to the present interglacial marine isotope stage 1 mis1 the spatial variations in sea surface temperature sst between mis5e and mis1 can reveal the important differences in the effects of insolation and oceanographic conditions between the two warm periods which in turns help refine global climate models in order to quantify the differences this study calculated the sst for the peak periods of mis5e c 128 113 ka bp and mis1 c 8 3 ka bp along the low latitude western north pacific margin 18 on to 26 on together with the previously published data from the south china sea 9 on to 19 on the results indicate a generally northwards decreasing trend in the two interglacial periods this latitudinal sst trend in both peak mis 1 and mis 5e can be attributed to the strong influence of ocean currents in the studied region secondly the average sst of peak mis5e is 1 3 0 2 c higher than that of peak mis1 suggesting a higher level of insolation during the previous interglacial however the above general pattern is complicated by the near shore and offshore difference in the effects of winter monsoon on oceanic conditions around 20 22 on the coastal upwelling near 26 on during peak mis5e reduced the sst whilst the sst was raised as the upwelling ceased during peak mis1 finally the ssts of the two warm periods are significantly higher than the present sst from 20 on northwards implying the influence of winter monsoon cold current in the taiwan strait