an 15 000 year record of el nino driven alluviation in southwestern ecuador debris flows have deposited inorganic laminae in an alpine lake that is 75 kilometers east of the pacific ocean in ecuador these storm induced events were dated by radiocarbon and the age of laminae that are less than 200 years old matches the historic record of el nino events from about 15 000 to about 7000 calendar years before the present the periodicity of clastic deposition is greater than or equal to 15 years thereafter there is a progressive increase in frequency to periodicities of 2 to 8 5 years this is the modern el nino periodicity which was established about 5000 calendar years before the present this may reflect the onset of a steeper zonal sea surface temperature gradient which was driven by enhanced trade winds

sea surface and subsurface circulation dynamics off equatorial peru during the last 17 kyr the complex deglacial to holocene oceanographic development in the gulf of guayaquil eastern equatorial pacific is reconstructed for sea surface and subsurface ocean levels from isotope geochemical proxies based on marine sediment cores at sea surface southern sourced cold coastal water and tropical equatorial surface water tropical surface water are intimately related in particular since 10 ka independent sea surface temperature proxies capturing different seasons emphasize the growing seasonal contrast in the gulf of guayaquil which is in contrast to ocean areas further offshore cold coastal water became rapidly present in the gulf of guayaquil during the austral winter season in line with the strengthening of the southeast trades while coastal upwelling off peru gradually intensified and expanded northward in response to a seasonally changing atmospheric circulation pattern affecting the core locations intensively since 4 ka bp equatorial surface water instead was displaced and tropical surface water moved northward together with the equatorial front at subsurface the presence of equatorial under current sourced equatorial subsurface water was continuously growing prominently since 10 8 ka b p during heinrich stadial 1 and large parts of the bolling allerod and similarly during short holocene time intervals at 5 1 4 ka b p and 1 5 0 5 ka b p the admixture of equatorial subsurface water was reduced in response to both short term weakening of equatorial under current strength from the northwest and emplacement by tropical equatorial surface water considerably warming the uppermost ocean layers

seasonal variation in the flux of planktonic foraminifera time series sediment trap results from the panama basin abstract a mooring array with three automated sediment traps capable of collecting time series samples was deployed in the panama basin for one year beginning in december 1979 a series of six consecutive two month long samples was collected at each of three depths 890 2590 and 3560 m in order to examine seasonal variation in the flux of planktonic foraminifera and evaluate the contribution of foraminifera to the total carbonate flux the flux of the larger planktonic foraminifera 250 500 m and 500 1000 m is greatest during february march when upwelling is most intense in the panama basin in contrast the maximum flux of the smaller foraminifera 125 250 m is associated with a phytoplankton bloom during the summer months june through september this size dependent flux pattern appears to be a species specific effect the flux of the larger foraminifera is dominated by non spinose forms i e neogloboquadrina dutertrei and globorotalia theyeri while the flux of the smaller foraminifera consists predominantly of spinose species i e globigerinoides ruber g sacculifer and g conglobatus although the magnitude of the flux varied throughout the year the average weight of individual foraminiferal tests in different size fractions showed no seasonal variability with the exception of the june july period when there was a major coccolith bloom planktonic foraminifera greater than 125 m account for between 28 and 34 of the total carbonate flux at this location during the coccolith bloom planktonic foraminifera accounted for less than 2 of the total carbonate flux planktonic foraminifera in the 250 500 m size range are the most significant contributors to the overall particulate flux accounting for roughly 70 80 of the total foraminiferal fluxes measured at the three trap depths

late glacial stage and holocene tropical ice core records from huascaran peru two ice cores from the col of huascaran in the north central andes of peru contain a paleoclimatic history extending well into the wisconsinan wurm glacial stage and include evidence of the younger dryas cool phase glacial stage conditions at high elevations in the tropics appear to have been as much as 8 to 12 c cooler than today the atmosphere contained about 200 times as much dust and the amazon basin forest cover may have been much less extensive differences in both the oxygen isotope ratio 18o 8 per mil and the deuterium excess 4 5 per mil from the late glacial stage to the holocene are comparable with polar ice core records these data imply that the tropical atlantic was possibly 5 to 6 c cooler during the late glacial stage that the climate was warmest from 8400 to 5200 years before present and that it cooled gradually culminating with the little ice age 200 to 500 years before present a strong warming has dominated the last two centuries

assessing the reliability of magnesium in foraminiferal calcite as a proxy for water mass temperatures though many studies on the mg contents in the calcitic tests of foraminifers exist the processes controlling its uptake are still a matter of debate laboratory cultures offer an excellent opportunity to reveal these mechanisms the mg concentrations within single chambers of the planktic foraminifer globigerinoides sacculifer brady maintained under controlled laboratory conditions were measured 1 at variable temperatures 19 5 29 5 c and constant salinity and 2 at variable salinity 22 45 and constant temperature the experimental results suggest that under natural conditions temperature is the leading mechanism controlling the mg ca ratio temperature and magnesium are related proportionally a temperature increase of ca 10 c gives rise to an increase of the magnesium concentrations of ca 130 drastic unnatural salinity changes dominate the effects of temperature a 110 change in the mg ca ratio was observed when salinity was elevated or reduced by more than ca 10 specimens which underwent gametogenesis reveal significantly higher mg concentrations than specimens that did not release gametes partition coefficients for mg in foraminiferal calcite are orders of magnitude lower than values from inorganically precipitated calcite when comparing observed mg ca ratios of foraminiferal tests with predicted mg ca ratios calculated according to empirical equations it becomes evident that foraminiferal tests are undersaturated with respect to mg for the water temperature they have experienced apparently foraminifers are capable of controlling their mg concentration the physiological processes presumably responsible for such depressed mg ca ratios appear to be temperature controlled as deduced from the close relationship of the observed mg ca ratios and water temperature this study demonstrates that variations in temperature and salinity are definitely reflected in the mg content of foraminiferal tests magnesium may thus serve as a paleo proxy for past surface water temperatures as long as postdepositional changes and salinity variations are of subordinate importance or can be excluded

a constraint to the wisconsinan glacial history canadian arctic archipelago thick ice bearing permafrost is not observed today beneath the deeper channels of the central queen elizabeth islands canadian arctic archipelago analysis of a precision temperature log recently obtained at an offshore well near ellef ringnes island indicates that the thermal regime beneath the seabed is in equilibrium with today s marine environment if thick permafrost similar to that observed on land today had existed in the pleistocene in areas that are presently offshore then such permafrost must have started melting no later than 25000 years ago in order to allow the present thermal regime to evolve this suggests that the inter island channels must have been water filled at least by that date

oxygen isotopic composition of multiple species of planktonic foraminifera recorders of the modern photic zone temperature gradient abundances of 12 species of planktonic foraminifera collected in two plankton tows from the east tropical atlantic are compared to the chlorophyll content and the temperature of the sea water from which they were collected as expected from previous work in the tropics all dominant tropical species occur in greatest abundance within the photic zone many species occur in greatest abundances in the seasonal thermocline in association with the maximum chlorophyll concentration while a few algal symbiont bearing species occur in greatest abundance in the mixed layer the 18o measurements of planktonic foraminifera shells from core top sediment samples confirm the vertical stratification within the photic zone that is suggested by the relationship between hydrography and abundances found in the plankton tows and found in the statistical study by ravelo et al 1990 comparison between the measured 18o values of planktonic foraminifera with the predicted 18o profiles of the overlying water column at three core locations indicate that species abundances in the sediment record the seasonally integrated conditions of the photic zone and suggests that the abundance of a species in the sediment depends on whether the preferred ecological conditions of that species may be found within the photic zone of the overlying water column sometime during the year species which calcify below the photic zone have only trace relative abundances finally it appears that the total range of 18o values of the dominant species approximates the predicted annual 18o of calcite range in the upper 80 m of the water column

indo pacific warm pool variability during the holocene and last glacial maximum we measured oxygen isotopes and mg ca ratios in the surface dwelling planktonic foraminifer globigerinoides ruber white s s and the thermocline dweller pulleniatina obliquiloculata to investigate upper ocean spatial variability in the indo pacific warm pool ipwp we focused on three critical time intervals the last glacial maximum lgm 18 21 5 ka the early holocene 8 9 ka and the late holocene 0 2 ka our records from 24 stations in the south china sea timor sea indonesian seas and western pacific indicate overall dry and cool conditions in the ipwp during the lgm with a low thermal gradient between surface and thermocline waters during the early holocene sea surface temperatures increased by similar to 3 degrees c over the entire region indicating intensification of the ipwp however in the eastern indian ocean timor sea the thermocline gradually shoaled from the lgm to early holocene reflecting intensification of the subsurface indonesian throughflow itf increased surface salinity in the south china sea during the holocene appears related to northward displacement of the monsoonal rain belt over the asian continent together with enhanced influx of saltier pacific surface water through the luzon strait and freshwater export through the java sea opening of the freshwater portal through the java sea in the early holocene led to a change in the vertical structure of the itf from surface to thermocline dominated flow and to substantial freshening of timor sea thermocline waters

variability in tropical thermocline nutrient chemistry on the glacial interglacial timescale abstract the organic carbon to calcite rain ratio in the tropical ocean may play a role in regulating global climate through its influence on co 2 draw down in the upper ocean the rain ratio may be altered by changes in the nutrient chemistry of the thermocline such changes in the tropical pacific are revealed by the carbon isotope values of thermocline dwelling planktonic foraminifera neogloboquadrina dutertrei the tropical pacific record over the last 30 kyr in the region south or along the equator which is fed by upwelling of deeper equatorial undercurrent water euc shows a carbon isotope signal distinct from any other in global mixed layer or benthic environments this unique record is consistent across the pacific unlike carbon isotope data from other basins and oceanic habitats the tropical pacific thermocline tracer shows last glacial values more positive than those of post glacial times the isotopic shift occurs in the early deglacial 20 17 kyr and leads to a deglacial carbon isotope minimum whose timing differs from that seen elsewhere the deglacial record of the pacific seems best interpreted as the progressive development of the modern nutrient rich thermocline under high nutrient low chlorophyll hnlc conditions the eastern tropical atlantic also has a unique glacial to modern carbon isotope record that is essentially opposite to that seen in the pacific strongly negative values in glacial times differ from those of the standard stratified ocean indicating higher nutrient concentrations a large shift to more positive values occurs rapidly at about 13 14 kyr this indicates a marked reduction in thermocline nutrients the implication is that nutrient flow to the tropics from the deep ocean via sub antarctic sources was stronger for the atlantic during the glacial but was weaker in the pacific transformation to modern conditions occurred in two steps at 17 18 and 13 14 kyr a timing that matches shifts in atmospheric co 2 concentrations and which would be compatible with driving those concentrations higher over deglacial time the mechanism could be an inherent difference in production regimes between the tropical pacific and atlantic

postglacial emergence of amund and ellef ringnes islands nunavut implications for the northwest sector of the innuitian ice sheet this paper presents relative sea level curves from amund and ellef ringnes islands northwest queen elizabeth islands these curves are of exponential form and record continuous ongoing holocene emergence although northwest ellef ringnes island is experiencing a late holocene transgression isobases drawn on postglacial shorelines rise south eastward towards an uplift centre in norwegian bay these suggest the ringnes islands occupied the northwest radius of the innuitian uplift which is congruent with glacial geological evidence suggesting parts of the ringnes islands were covered by the late wisconsinan innuitian ice sheet the isobases provide a provisional reconstruction of glacioisostatic recovery within the northwest innuitian uplift their pattern supports earlier reconstructions that maximum late wisconsinan ice thickness occurred across norwegian bay marking the position of an ice divide which is consistent with ice flow features on amund ringnes island they record the diminishing thickness of the innuitian ice sheet from norwegian bay to the arctic ocean the absence of an isobase embayment across the ringnes islands suggests a relatively uniform ice load across both islands and hassel and massey sounds parallel isobases across peary channel indicate this ice load extended beyond massey sound although their northward deflection suggests an increasing influence of the former

holocene delevelling of devon island arctic canada implications for ice sheet geometry and crustal response the raised beaches and deltas of devon island contain an abundance of dateable materials a large set of radiocarbon dates 228 154 of which are new are used to construct relative sea level curves and isobase maps for the island the best materials for this purpose are driftwood logs 61 dates and bowhead whale bones 74 dates from raised beaches and mollusc shells from marine limit deltas 20 dates or from altitudes close to marine limit 14 dates during the last glacial maximum the island is thought to have lain beneath the southeastern flank of the innuitian ice sheet the relative sea level history is congruent with that inferred ice configuration the island spans half the ice sheet width relative sea level curves are of simple exponential form except near the glacial limit where an early holocene emergence proceeded to a middle holocene lowstand below present sea level which was followed by submergence attending the passage of the crustal forebulge the response times of relative sea lev

living planktic foraminifera in the central tropical pacific ocean articulating the equatorial cold tongue during la nina 1992 abstract in cold tongue conditions of august september 1992 living planktic foraminifera in the equatorial pacific tracked circulation featuresand phytoplankton abundance an equatorial assemblage associated with the cool and productive equatorial region contained g bulloides a species often associated with tropical coastal upwelling as well as the nonspinose herbivores g menardii g glutinata p obliquiloculata and n dutertrei previously associated with equatorial environments within surface subtropical waters poleward of 5 n and 5 s g sacculifer g ruber and g conglobatus dominated foraminiferal populations these species have successfully adapted to oligotrophic conditions by exploiting dinoflagellate endosymbionts high standing stocks of these species in equatorial regions suggest that they can also thrive within equatorial light levels and temperatures a deep southern assemblage dominated by nonspinose g conglomerata and g tumida and spinose g aequilateralis had a subsurface maximum at 80 200 m outside of active upwelling and outcropped to the surface at 1 s from el nino to cold tongue conditions equatorial fauna reflected higher primary productivity and an increase in the role of advection by the south equatorial current

characteristics of radiation and propagation of seismic waves in northern finland estimated based on records of local earthquakes the characteristics of radiation and propagation of seismic waves required in various seismological applications especially in seismic hazard assessment are estimated in northern finland based on records of local earthquakes 80 records from four stations mw 1 5 to 4 1 h 3 to 25 km northern finland possesses relatively low seismic activity however rather strong earthquakes occurred there in the past we applied coda normalization method to estimate the quality factor q f q0fn and then verified and corrected the q f estimates at low frequencies by stochastic simulations we obtained q0 80 to 100 n 1 1 to 1 2 for hypocentral distances of 20 to 150 km and q0 180 to 350 n 0 7 to 0 9 for hypocentral distances of 150 to 320 km other parameters were estimated by the empirical methods and stochastic simulation of local earthquakes ml 2 0 we estimated the stress drop 200 bars geometrical spreading as a two segment function 1 r for r 0 to 80 km and 1 80 for r 80 to 300 km the duration of seismic motion depending on the hypocentral distance kappa value 0 001 to 0 03 s and some other parameters the obtained high estimates of the stress drop along with rather high q values may result in noticeably increased compared to those that could be expected on average pga estimates in seismic hazard assessment in northern finland

identification of the non linear behaviour of liquefied and non liquefied soils during the 1995 kobe earthquake summary a method based on the non linear system identification technique is suggested for estimating the contents of the non linear components which are the result of quadratic cubic and higherorder non linearities in the ground response during the strong motion the method is applied to data from the near fault zone of the 1995 kobe earthquake and the contents of linear and non linear components in the ground response changing with time during the strong motion are estimated for port island pi sgk and tks sites located at 2 6 and 15 km from the fault plane respectively at pi the non linear part of the response increased with developing liquefaction it was as high as 40 60 per cent of the intensity of the response at sgk and tks sites the non linear components of the response did not exceed 40 and 13 per cent of the intensity of the response respectively odd order non linear components predominated in the soil response whereas even order non linear components increased and became comparable with odd order ones in liquefied soils and in cases of high intensity of the strong motion when the loading parts of the stress strain relations of the upper layers gained noticeable even components as a whole the contents of odd order and even order components in the soil response are determined by the shapes of the stress strain relations in the upper most non linear soil layers at the three sites changes in spectra of earthquake signals in subsurface soil layers were substantial as a result of the high non linearity of the soil behaviour and spectra of signals on the surface tend to take the form of e f f k the limiting spectral shape was achieved during the kobe earthquake at pi and sgk sites the proposed methods for processing vertical array records allow understanding of seismic wave transformations in subsurface soils and are useful for predicting the soil behaviour during future earthquakes

site amplifications for generic rock sites seismic shear wave velocity as a function of depth for generic rock sites has been estimated from borehole data and studies of crustal velocities and these velocities have been used to compute frequency dependent amplifications for zero attenuation for use in simulations of strong ground motion we define a genetic rock site as one whose velocity at shallow depths equals the average of those from the rock sites sampled by the borehole data most of the boreholes are in populated areas for that reason the rock sites sampled are of particular engineering significance we consider two genetic rock sites rock corresponding to the bulk of the borehole data and very hard rock such as is found in glaciated regions in large areas of eastern north america or in portions of western north america the amplifications on rock sites can be in excess of 3 5 at high frequencies in contrast to the amplifications of less than 1 2 on very hard rock sites the consideration of unattenuated amplification alone is computationally convenient but what matters for ground motion estimation is the combined effect of amplification and attenuation for reasonable values of the attenuation parameter k 0 the combined effect of attenuation and amplification for rock sites peaks between about 2 and 5 hz with a maximum level of less than 1 8 the combined effect is about a factor of 1 5 at 1 hz and is less than unity for frequencies in the range of 10 to 20 hz depending on t using these amplifications we find provisional values of about ao 70 bars and k 0 0 035 sec for rock sites in western north america by fitting our empirically determined response spectra for an m 6 5 event to simulated values the borehole data yield shear velocities 033o of 618 and 306 rrdsec for rock and soil sites respectively when averaged over the upper 30 m from this we recommend that v30 equals 620 and 310 m sec for applications requiring the average velocity for rock and soil sites in western north america by combining the amplifications for rock sites and the site factors obtained from our analysis of strong motion data we derive amplifications for sites with 17 3o 520 m sec nehrp class c corresponding to a mix of rock and soil sites and v3o 310 and 255 m sec average soil and nehrp class d sites respectively for the average soil site the combined effect of amplification and attenuation exceeds a factor of 2 0 for frequencies between 0 4 and about 4 hz with a peak site effect of 2 4 the peak of the nehrp class d site effect is 2 7

canadian arctic permafrost observatories detecting contemporary climate change through inversion of subsurface temperature time series 1 we describe long term permafrost temperature and climate change observatories established in the northeastern canadian high arctic 77 82 5 n two sites have deep temperature logs 165 and 800 m and thermistor cables and automatic loggers have been installed in the upper 65 m the third site has multiple temperature logs at three 61 m boreholes with thermistor cables frozen into the permafrost a fourth deep site 750 m is included for regional completeness geothermal spectrum inversion is used to determine ground surface temperature histories the little ice age is resolved from the mid 1700s to mid 1800s with surface temperatures 1 k below the long term mean a subsequent recovery yields late 20th century surface temperatures 3 k higher these results correlate with similar reconstructions reported for greenland ice cap holes grip and dye 3 to the southeast the canadian and greenland surface temperatures show a weak inverse correlation with the north atlantic oscillation suggesting recent climate change as a common causal source simultaneous inversions of multiple logs over 22 years at the 61 m holes resolve two to three major cycles in ground surface temperature variation over the latter half of the 20th century here permafrost ground temperatures increase 0 3 0 5 c decade compared to 0 6 c decade for air temperatures annual total snow increases 22 cm decade and may insulate permafrost from the larger transient trends in air temperatures finally atmospheric temperature inversions prevalent in arctic winters may contribute to anomalously high ground surface temperatures observed at two locations

oxygen minimum zone variations in the tropical pacific during the holocene we performed simulations with a global model of ocean biogeochemistry forced with orbitally driven anomalies of oceanic conditions for the mid holocene known as holocene climate optimum to investigate natural variability in the eastern equatorial pacific oxygen minimum zone eep omz while the global mean temperature during the mid holocene was likely slightly higher than the 1961 1990 mean the sea surface temperature in the eep was slightly lower mid holocene oxygen concentrations in the eep omz are generally increased locally by up to 50 and the eep omz volume was depending on definition of the omz threshold at least 6 lower these higher oxygen levels are the combined result of competing physical and biogeochemical processes our results imply that mechanisms for past changes in the eep omz intensity and extension can differ from the global warming driven decline in oxygen levels observed for the recent decades and predicted for the future

hydrologic variability and the onset of modern el nino southern oscillation a 19 250 year record from lake elsinore southern california there are very few terrestrial palaeoclimate archives spanning the last glacial maximum through the holocene from coastal southern california yet knowledge of past climate dynamics is critical for assessing present and future constraints on the region s dwindling freshwater resources we present initial results from two drill cores extracted from the present day edge of lake elsinore southern california s largest natural lake using a multiproxy approach including lithologic description mass magnetic susceptibility loi 550 c total organic matter and loi 950 c total carbonate we infer first order long term climate change over the past 19 250 calendar years furthermore we suggest possible first order forcing mechanisms that drive this change which include presence absence of continental ice sheets insolation and complex ocean atmosphere interactions our results indicate four distinct millennial scale climate modes over the past 19 250 calendar years these modes include a wet last glacial maximum 19 250 17 120 cal yr bp a relatively dry late glacial holocene transition 17 120 9450 cal yr bp a wet early holocene 9450 7670 cal yr bp and a highly variable mid to late holocene climate i e alternating wet dry cycles 7670 cal yr bp present we attribute the mid to late holocene climate interval to the onset of el nino southern oscillation ca 7000 cal yr bp and a more vigorous hydrologic system these results are supported by a variety of regional terrestrial and marine palaeoclimate archives copyright 2005 john wiley sons ltd

seasonal stable isotopic variations in living planktonic foraminifera from bermuda plankton tows abstract seasonal variations in surface water temperature and the 18o 16o ratios of calcite tests of living planktonic foraminifera collected in the upper 10 mare are coincident in the sargasso sea off bermuda the 18o of seasonally restricted globorotalia truncatulinoides and globigerinoides ruber pink and white may be used to determine the seasonal temperature contrast of the oceans in the past a preliminary model based on yearly absolute abundance and isotopic composition of these two species is able to approximate the composite 18o of fossil specimens of these species carbon and oxygen isotopic compositions of most species are size dependent with the largest differences occuring in 13c as a function of size the calcite tests of all living species were depleted in 13c relative to the 13c of total dissolved co2 at 0 and 50 m with no seasonal pattern in 13c being discernible in any species in almost all cases fossil specimens from box core sediments are significantly enriched in 13c and slightly enriched in 18o relative to their counterparts in the living fauna because the sediment populations are generally composed of larger sized specimens compares to the plankton of larger size specimens compared to the plankton

oceanic conditions in the eastern equatorial pacific during the onset of enso in the holocene abstract records from south america show that modern enso el nino southern oscillation did not exist 7000 cal yr b p and has developed progressively since then there has been little information available on oceanic conditions in the eastern equatorial pacific eep to constrain explanations for enso onset we report quantitative observations on thermocline and mixed layer conditions in the eep during enso start up we found important changes in both the thermocline and the mixed layer indicating increased upwelling of cooler waters since 7000 cal yr b p this resulted from change in the source and or properties of waters supplying the equatorial undercurrent which feeds upwelling along the equator and the peru margin modeling shows that enso is sensitive to subsurface conditions in the eastern equatorial pacific and that the changes in the thermocline we observed were driven by extratropical processes giving these a role in conditioning the development of enso this is in contrast to models that call for control of equatorial pacific oceanography by tropical processes only these infer stronger upwelling and cooler surface waters for the eep during the mid holocene which is not supported by our results

seasonal changes in species composition numbers mass size and isotopic composition of planktonic foraminifera settling into the deep sargasso sea abstract planktonic foraminifera recovered from six successive sediment trap samples collected over fourteen months at a depth of 3200 m near bermuda show varied responses to seasonal changes in the near surface hydrography these include changes in species composition and within species changes in number of individuals collected per unit time average size and weight of individuals and in oxygen and carbon isotopic composition a total of seventeen species were identified and eleven were sufficiently abundant for isotopic analysis in at least some of the samples the accumulations on the sea floor of some of these species can be expected to contain a strong seasonal component in their oxygen isotopic composition which may be utilized in paleoclimatic and paleo oceanographic reconstructions best suited to this purpose are those species which form their tests in isotopic equilibrium with surface water and whose abundance is confined to a portion of the year only the best examples are pulleniatina o bliguiloculata globigerinoides conglobatus and neogloboquadrina dutertrei globigerinoides ruber is a good estimator of the average surface water temperature because it occurs in rather even abundance throughout the year hastigerina pelagica though very abundant in surface water is practically eliminated even before arrival on the sea floor by partial resorption and structural weakening of the tests during gametogenesis orbulina universa globorotalia truncaltulinoides and globorotalia hirsuta show morphological and istopic evidence for contibnued calcification in deeper water after initial test formation near ther surface globigerina bulloides represents the most striking example of oxygen isotopic disequilibrium with sea water

characteristics of soil response in near fault zones during the 1999 chi chi taiwan earthquake distribution of parameters characterizing soil response during the 1999 chi chi taiwan earthquake mw 7 6 around the fault plane is studied the results of stochastic finite fault simulations performed in pavlenko and wen 2008 and constructed models of soil behavior at 31 soil sites were used for the estimation of amplification of seismic waves in soil layers average stresses strains and shear moduli reduction in the upper 30 m of soil as well as nonlinear components of soil response during the chi chi earthquake amplification factors were found to increase with increasing distance from the fault or with decreasing the level of input motion to soil layers whereas average stresses and strains shear moduli reduction and nonlinear components of soil response decrease with distance as r 1 the area of strong nonlinearity where soil behavior is substantially nonlinear the content of nonlinear components in soil response is more than 40 50 of the intensity of the response and spectra of oscillations on the surface take the smoothed form close to e f f n is located within 20 25 km from the fault plane 1 4 of its length nonlinearity decreases with increasing distance from the fault and at 40 50 km from the fault 1 2 of the fault length soil response becomes virtually linear comparing soil behavior in near fault zones during the 1999 chi chi the 1995 kobe mw 6 8 and the 2000 tottori japan mw 6 7 earthquakes we found similarity in the behavior of similar soils and predominance of the hard type of soil behavior resonant phenomena in upper soil layers were observed at many studied sites however during the chi chi earthquake they involved deeper layers down to 40 60 m than during lesser magnitude kobe and tottori earthquakes

holocene benthic foraminiferal assemblages indicate long term marginality of reef habitats from moreton bay australia abstract since european settlement ca 1824 ce the subtropical inshore reefs of moreton bay have undergone rapid deterioration in water quality from changes in land use practices resource exploitation and rapid population growth spurring marine managers to assess the drivers of ecological shifts however the short temporal scale of most studies is an inadequate baseline for understanding the severity and magnitude of biological response we present millennial scale records employing palaeoecological and quantitative multivariate techniques within a concise chronological framework to analyse benthic foraminiferal community structure of reefs in moreton bay queensland well constrained u th dated millennial scale records from sediment cores were used to document the long term response of foraminifers to natural environmental variability the temporal and spatial distribution patterns of foraminifers reveal long term marginality throughout the 7400 years of holocene history prior to european settlement while specific faunal response to the effects of relative enso climate and sea level fall are difficult to disentangle the earlier phases of reef development are already represented by marginal taxa indicating possibly an earlier response to a decline in conditions overall long term consistency in conditions favoured two types of low diversity reef assemblages 1 high density of small heterotrophic and opportunistic species and 2 low density of photosymbiotic foraminiferal assemblages comparison of foraminiferal community composition between the holocene and the present day indicates overlap in species composition supporting long term marginality particularly in the western bay such combined palaeoecological and recent studies can benefit long term initiatives for monitoring present and future water quality conditions in the bay s reef habitats

finite source modeling of the 1999 taiwan chi chi earthquake derived from a dense strong motion network the 1999 chi chi earthquake m w 7 6 20 september 1999 17 47 15 9 utc located at 23 853 n 120 816 e and depth of 7 5 km inicted severe re gional scale damage to taiwan the strong motion waveeld was captured by a dense network of stations with average station spacing of 5 km which represents the most complete strong motion dataset to date to use to study the kinematic source process of an earthquake we inverted velocity waveforms recorded by 21 stations for the spatial variation in slip on a planar fault model composed of 416 subfaults each with a dimension of 3 5 km by 3 5 km the planar model has a strike of n5 e and a dip of 30 e and the inversion solves for the direction and magnitude of the slip to account for possible temporal source complexity we allowed each subfault to slip within 10 overlapping time windows each with a duration of 3 sec the results show that the source is composed primarily of three major asperities the rst of which is mainly dip slip extending from the hypocenter to the northern end of the surface rupture in this asperity slip occurred in two pulses separated in time by 5 sec the dislocation rise time for each pulse is short 3n4 sec yielding an approximate av erage slip velocity of 80 cm sec the second asperity is located at shallow depth near the northern end of the rupture where very large ground velocities were observed this asperity is on average oblique and shows a temporal rake rotation from pure dip slip to strike slip the rotating rake suggests a low initial shear stress on the northern end of the fault slip in this asperity is dominated by a large pulse with a dislocation rise time of 8 sec a station near the northern end of the surface rupture recorded a peak velocity of 390 cm sec which we nd to be due to the constructive interference of energy radiated from the rst two asperities the third asperity is located south of the epicenter the total moment from the three asperities is 4 1 10 27 dyne cm which was released over a period of 30n35 sec within an area of 900 km 2 synthetics calculated from the three asperity model explain 85 of the data and represent 98 of the total variance reduction our results indicate that slip is conned to the shallow region of the fault deep slip patches are less constrained and that the slip distribution may be representative of fault segmentation along the chelungpu fault system

glacial isostatic adjustment i the forward problem summary the isostatic adjustment of a radially stratified visco elastic spheroid is treated using space time green functions for the associated surface mass load boundary value problem these impulse response functions are convolved with a heaviside function to give the time dependent deformation of the planet which would be produced by a unit point mass brought up from infinity at t 0 and allowed to remain on the surface the resulting heaviside green functions can be employed to simulate all of the important signatures of glacial isostatic adjustment given a space time dependent surface mass load consisting of ice sheet ablation histories and a model of the simultaneous filling of the ocean basins these source terms are simply convolved with the heaviside green function appropriate to a specific response signature a realistic model of the spatial distribution of the main late pleistocene ice loads and of their temporal disintegration is constructed the response of two visco elastic earth models is computed and compared to a global set of relaxation data relative sea level curves on the basis of this initial comparison of theory and observation the possibility that the lower mantle has a viscosity which is significantly in excess of the viscosity of the upper mantle is excluded in addition clear evidence of the presence of the lithosphere has been found in relaxation data from sites which were near the edge of the laurentide ice sheet such data should therefore prove useful as a basis for analysis of lateral variations in lithosphere thickness further extensions of the calculation are suggested

stable isotope studies of planktonic foraminifera in north atlantic core tops abstract stable isotope analyses of eight species of planktonic foraminifera from 42 north atlantic core tops are used to calculate isotopic depth ranges these depth ranges agree quite well with those based on plankton tows suggesting that no significant departures from oxygen isotopic equilibrium occur in most species reasonable isotherm patterns can be obtained from the 18 o data and the range in 18 o values between species is a useful indicator of the boundary of the subtropical gyre

holocene paleoenvironmental reconstruction from deep ground temperatures a comparison with paleoclimate derived from the δ18o record in an ice core from the agassiz ice cap canadian arctic archipelago

precision logging of temperature gradients and the extraction of past climate abstract with new equipment it is now possible to obtain borehole logs which allow resolution of temperature gradients differing by 0 1 0 2 mk m over a distance of about 0 5 m at a logging rate of 8 m min since such a detailed profile of temperature gradient versus depth is easily obtained disturbances to the equilibrium gradient can now be readily identified in order to identify the forms of surface temperature variation which disturb the equilibrium regime in boreholes to depths of more than 100 m some tests are proposed in which a polynomial curve is fitted to the observed temperature gradient the real roots of the first and second derivative equations of this fitted curve are then used to estimate the types of surface thermal disturbances aplication of these tests to a well characterized borehole indicates that there were increases in temperature of 1 k approx 250 years ago 3 6 k approx 25 years ago and 5 0 k approx 8 years ago the first disturbance may be associated with the ending of the little ice age while the last two are associated with the completion of large buildings nearby in 1958 and 1967

seasonal changes in the isotopic composition of planktonic foraminifera collected in panama basin sediment traps abstract isotopic analyses have been made on five species of planktonic foraminifera collected in two deployments of parflux mark ii time series sediment traps in the panama basin the automated sampling system on the traps provided 4 one month samples from 29 july to 16 november 1979 and 6 two month samples from december 1979 to november 1980 the 18o values of globigerinoides ruber and globigerinoides sacculifer in this region are primarily affected by a low salinity surface layer that forms during the early winter these species each show a 1 total range in 18o the 18o values of the colder water species globorotalia menardii neogloboquadrina dutertrei and globorotalia theyeri show smaller seasonal changes in 18o the 13c values of g ruber and g sacculifer exhibit small seasonal changes 0 35 and 0 4 respectively despite large seasonal changes in surface water productivity the colder water species exhibit only slightly larger changes in 13c up to 0 55 throughout the year all colder water species exhibit minimum or near minimum 13c values during february and march which is the period of maximum upwelling and primary productivity seasonal variations in the flux of foraminifera in the water column at this location will have only a small effect on the isotopic composition of the sediment assemblage extreme values of 18o and 13c do not occur during the periods which are associated with the high flux of foraminiferal tests

holocene variability in the intensity of wind gap upwelling in the tropical eastern pacific wind driven upwelling in pacific panama is a significant source of oceanographic variability in the tropical eastern pacific this upwelling system provides a critical teleconnection between the atlantic and tropical pacific that may impact climate variability on a global scale despite its importance to oceanographic circulation ecology and climate little is known about the long term stability of the panamanian upwelling system or its interaction with climatic forcing on millennial time scales using a combination of radiocarbon and u series dating of fossil corals collected in cores from five sites across pacific panama we reconstructed the local radiocarbon reservoir correction r from 6750 cal b p to present because the r of shallow water environments is elevated by upwelling our data set represents a millennial scale record of spatial and temporal variability of the panamanian upwelling system the general oceanographic gradient from relatively strong upwelling in the gulf of panama to weak to absent upwelling in the gulf of chiriqui was present throughout our record however the intensity of upwelling in the gulf of panama varied significantly through time our reconstructions suggest that upwelling in the gulf of panama is weak at present however the middle holocene was characterized by periods of enhanced upwelling with the most intense upwelling occurring just after of a regional shutdown in the development of reefs at 4100 cal b p comparisons with regional climate proxies suggest that whereas the intertropical convergence zone is the primary control on modern upwelling in pacific panama the el nino southern oscillation drove the millennial scale variability of upwelling during the holocene

regolith modeling and its relation to earthquake induced building damage a remote sensing approach regolith thickness is known as a major factor in influencing the intensity of earthquake induced ground shaking and consequently building damages it is however often simplified or ignored due to its variable and complex nature to evaluate the role of regolith thickness on earthquake induced building damage a remote sensing based methodology is developed to model the spatial variation of regolith thickness based on dem derived topographic attributes and geology regolith thickness samples were evenly collected in geological formations at representative sites of topographic attributes topographic attributes elevation slope twi distance from stream computed from the aster derived dem and a geology map were used to explore their role in spatial variation of regolith thickness stepwise regression was used to model the spatial variation of regolith thickness in erosional landscape of the study area topographic attributes and geology explain 60 of regolith thickness variation in the study area to test if the modeled regolith can be used for prediction of seismic induced building damages it is compared with the 2005 kashmir earthquake induced building damages derived from high resolution remote sensing images and field data the comparison shows that the structural damages increase with increasing regolith thickness the predicted regolith thickness can be used for demarcating site prone to amplified seismic response

otolith δ18o record of mid holocene sea surface temperatures in peru peruvian sea catfish galeichthys peruvianus sagittal otoliths preserve a record of modern and mid holocene sea surface temperatures ssts oxygen isotope profiles in otoliths excavated from ostra 6010 90 years before the present yr b p 8 degrees 55 s indicate that summer ssts were approximately 3 degrees c warmer than those of the present siches otoliths 6450 110 yr b p 4 degrees 40 s recorded mean annual temperatures approximately 3 degrees to 4 degrees c warmer than were measured under modern conditions trophic level and population diversity and equitability data from these faunal assemblages and other peruvian archaeological sites support the isotope interpretations and suggest that upwelling of the peru chile current intensified after approximately 5000 yr b p

geothermal inversion of canadian arctic ground temperatures and effect of permafrost aggradation at emergent shorelines we apply traditional geothermal spectrum inversion to precision temperature logs and thermal conductivity from 10 wells in the canadian arctic archipelago 75 to 81 n sites lie beyond the holocene marine limit and no effect of deep permafrost dynamics is expected ground surface temperature gst changes correlate with the little ice age and little climatic optimum with average amplitudes relative to 1980 of 2 7 k and 1 6 k respectively results correlate broadly with similar reconstructions for this area and greenland ice cap holes grip and dye 3 to the southeast an offshore site in 244 m water yields a little ice age seabed temperature amplitude of 0 7 k suggesting a moderated climate impact on regional ocean temperatures nearshore boreholes where permafrost is aggrading owing to glacioisostatic emergence are excluded we demonstrate that traditional inversion codes without latent heat of phase change predict the magnitude of the emergence signal but a timing far too recent

vertical distribution and isotopic fractionation of living planktonic foraminifera from the panama basin a model1 2 which explains the vertical and seasonal distribution of planktonic foraminifera was developed using data from the western north atlantic and is comprised of three tenets 1 the conditions in the photic zone upper 80 100 m exclusively dictate planktonic foraminifera species composition and abundance throughout the water column 2 species are vertically stratified within the photic zone according to their temperature preference depth distribution according to temperature preference has been proposed by several authors3 based on isotope analyses of sediments due to seasonal temperature variations seasonal variations in the 18o composition of seawater and species specific isotope fractionation rigorous proof of this hypothesis cannot be provided from sediment analyses alone 3 the chlorophyll maximum is a major food source zone which is preferentially exploited by foraminifera our data from the panama basin which are presented here are confirmation of this model the panama basin in the eastern equatorial pacific which has a shallow and steep thermocline was sampled for living planktonic foraminifera a multiple opening closing net and environmental sensing system mocness 4 was used to collect 13 sets of eight vertically stratified oblique samples we report here the quantitative distribution and stable isotopic composition of planktonic foraminifera from four mocness tows taken over 5 days during august 1979 rv knorr cruise 73 at 5 20 n 8 50 w each tow consisted of eight samples which integrated 12 5 m intervals from 0 to 100 m for moc 126 25 m intervals from 0 to 200 m for moc 127 100 150 m intervals from 0 to 1 000 m on moc 128 and 250 m intervals from 0 to 2 000 m on moc 131

inference of ground surface temperature history from subsurface temperature data interpreting ensembles of borehole logs ground surface temperature histories gsths inferred from borehole temperaturedepth t z data are often degraded to a various extent by random or systematic noise in thet z data and in the measurements of thermophysical properties of the earth to minimize the effects of noise and hence improve the fidelity of the inferred gsth a plausible approach is to perform a simultaneous inversion of thet z logs in a region or alternatively to invert the individualt z logs and then average the resulting gsths averaging and simultaneous inversion are conceptually different whereas an averaging can always be peformed a simultaneous inversion is predicated on the assumption of a common transient component of the gsth in all thet z logs in this work we examine and compare the two approaches using a time domain inverse formulation based on the method of least squares we consider a set of scenarios a multiplet z logs from a single borehole b multiple boreholes from a single site c multiple boreholes in similar climatological settings and d multiple boreholes in different climatological settings we show that for a b and c averaging and simultaneous inversion yield nearly identical results for boreholes in different settings the assumption of a common transient gsth may be invalid and averaging and simultaneous inversion give divergent results

simulation of ground motion from strong earthquakes of kamchatka region 1992 1993 at rock and soil sites to estimate the parameters of ground motion in future strong earthquakes characteristics of radiation and propagation of seismic waves in the kamchatka region were studied regional parameters of radiation and propagation of seismic waves were estimated by comparing simulations of earthquake records with data recorded by stations of the kamchatka strong motion network acceleration time histories of strong earthquakes mw 6 8 7 5 depths 45 55 km that occurred near the eastern coast of kamchatka in 1992 1993 were simulated at rock and soil stations located at epicentral distances of 67 195 km in these calculations the source spectra and the estimates of frequency dependent attenuation and geometrical spreading obtained earlier for kamchatka were used the local seismic wave amplification was estimated based on shallow geophysical site investigations and deep crustal seismic explorations and parameters defining the shapes of the waveforms the duration etc were selected showing the best fit to the observations the estimated parameters of radiation and propagation of seismic waves describe all the studied earthquakes well based on the waveforms of the acceleration time histories models of slip distribution over the fault planes were constructed for the studied earthquakes station pet can be considered as a reference rock station having the minimum site effects the intensity of ground motion at the other studied stations was higher than at pet due to the soil response or other effects primarily topographic ones at soil stations ins aer and dch the parameters of soil profiles homogeneous pyroclastic deposits were estimated and nonlinear models of their behavior in the strong motion were constructed the obtained parameters of radiation and propagation of seismic waves and models of soil behavior can be used for forecasting ground motion in future strong earthquakes in kamchatka

holocene hydrologic balance of tropical south america from oxygen isotopes of lake sediment opal venezuelan andes precipitation in the south american andes is derived from atlantic ocean evaporation which is modified by passage over lowland south america the isotopic composition of andean precipitation reflects evaporation conditions over the atlantic ocean moisture recycling during advection across the south american lowlands and uplift to the andes records of the oxygen isotope composition of precipitation in the venezuelan andes derived from lake sediment diatom 18 o measurements show a 2 4 decrease during the past 10 000 yr a simple model of the evaporation advection and uplift processes is used to understand the cause of the isotope shift the data and model suggest that the decreasing 18 o reflects a decrease in the fraction of moisture entering south america that reaches the andes ice cores from peru and bolivia exhibit similar isotope trends indicating that the shift occurred in both hemispheres an isotopic record of amazon river discharge is consistent with the andean records indicating increasing continental runoff was associated with the decreasing export of water vapor orbital changes in solar insolation cannot explain the synchronous trends in both hemispheres changing climate in the tropical pacific is an attractive explanation for the trends because modern interannual variability in this region has similar effects in both hemispheres

orbital controls on the el nino southern oscillation and the tropical climate the global synchroneity of glacial interglacial events is one of the major problems in understanding the link between milankovitch forcing and the climate of the late quaternary in this study we isolate a part of the climate system the tropical pacific and test its sensitivity to changes in solar forcing associated with changes in the earth s orbital parameters we use a simplified coupled ocean atmosphere model that is run for the past 150 000 years and forced with milankovitch changes in the solar insolation this system responds primarily to the precessional cycle in solar forcing and is capable of generating a mean response to the changes in the seasonal distribution of solar radiation even while the annual mean insolation is roughly constant the mean response to the precessional forcing is due to an interaction between an altered seasonal cycle and the el nifio southern oscillation enso changes in the enso behavior result in a mean tropical climate change the hypothesis is advanced that such a change in the tropical climate can generate a globally synchronous climate response to milankovitch forcing

structure and timing of the last deglaciation oxygen isotope evidence foraminiferal oxygen isotope data from 24 tropical atlantic sediment cores constrained by 77 14c dates are stacked to form a composite record of isotopic termination 1 this record indicates that most of the isotopic transition at the end of the last ice age occurred between 14 ka bp and 6 ka bp minor isotopic expression of deglaciation is permitted as early as 16 ka bp but the most rapid rate of change occurred between 14 ka bp and 12 ka bp three steps of maximum change are present although they are close to the statistical limits of detection in the composite record the clear presence of the steps in individual records suggests that they are real we estimate their timing at 14 12 ka bp termination 1 a 10 9 ka bp termination 1 b and 8 6 ka bp termination 1 c centering of the termination near 11 ka bp is consistent with the milankovitch hypothesis that high summer insolation caused deglaciation in detail however maximum rates of change prior to the 11 ka bp insolation extreme and the inferred steps require additional mechanisms controlling the tempo of glacial interglacial climate change steps equivalent to those in 18o have not been detected in ice margin retreat data steps in the isotopic transition if real may record thinning of the ice sheets not accompanied by loss of area alternation between near equilibrium and near stagnant ice sheet profiles during deglaciation is hypothesized perhaps due to calving and unstable down draw of the ice sheets followed by partial re equilibration significant problems remain the effects of temperature on the isotope record are only partially constrained presently available data allow only semi quantitative intercalibration of ice volume sea level and isotopic estimates of glaciation

estimation of nonlinear time dependent soil behavior in strong ground motion based on vertical array data to improve our understanding of nonlinear elastic properties of soils a method is proposed of estimation of stress strain relations of soils in situ in strong ground motion based on vertical array data strong motion records provided by seismic vertical arrays allow estimation of nonlinear stress strain relations in soil layers at different depths from the surface down to the location of the deepest device as an example records obtained during the main shock of the 1995 kobe earthquake at port island sgk and tks sites were used to estimate the stress strain relations in the soil profiles for different layers different types of nonlinear stress strain relations were selected according to the profiling data to account for temporal changes in the soil behavior consecutive parts of records were examined and for successive time intervals the relations were found showing the best fit approximation to the observed data at port island and sgk sites where the strongest accelerations were recorded the obtained stress strain relations showed systematic changes in the upper layers 0 14 m such as a progressive reduction of the slopes of the stress strain curves due to liquefaction at port island and reduction and recovery of the slopes at sgk and tks sites at the three sites the stress strain relations remained stable in layers below 11 14 m thus the proposed approach gives us a representation of the soil behavior in layers at different depths in strong ground motion it allows calculation of the propagation of arbitrary seismic signals in the studied profiles and estimation of nonlinear components in the ground response by the nonlinear system identification technique the method can also be applied to evaluate the ground response at sites where profiling data are available and an imposed motion can be estimated

a wavelet based seismogram inversion algorithm for the in situ characterization of nonlinear soil behavior we present a full waveform inversion algorithm of downhole array seismogram recordings that can be used to estimate the inelastic soil behavior in situ during earthquake ground motion for this purpose we first develop a new hysteretic scheme that improves upon existing nonlinear site response models by allowing adjustment of the width and length of the hysteresis loop for a relatively small number of soil parameters the constitutive law is formulated to approximate the response of saturated cohesive materials and does not account for volumetric changes due to shear leading to pore pressure development and potential liquefaction we implement the soil model in the forward operator of the inversion and evaluate the constitutive parameters that maximize the cross correlation between site response predictions and observations on ground surface the objective function is defined in the wavelet domain which allows equal weight to be assigned across all frequency bands of the non stationary signal we evaluate the convergence rate and robustness of the proposed scheme for noise free and noise contaminated data and illustrate good performance of the inversion for signal to noise ratios as low as 3 we finally employ the proposed scheme to downhole array data and show that results compare very well with published data on generic soil conditions and previous geotechnical investigation studies at the array site by assuming a realistic hysteretic model and estimating the constitutive soil parameters the proposed inversion accounts for the instantaneous adjustment of soil response to the level and strain and load path during transient loading and allows results to be used in predictions of nonlinear site effects during future events

modeling climate shift of el nino variability in the holocene a coupled ocean atmosphere general circulation model is used to investigate climatic shift of el nino in the holocene the model simulates a reduced enso intensity in the early and mid holocene in agreement with paleoclimate record the enso reduction is proposed to be caused by both an intensified asian summer monsoon and a warm water subduction from the south pacific into the equatorial thermocline

regional and global benthic δ18o stacks for the last glacial cycle although detailed age models exist for some marine sediment records of the last glacial cycle 0 150 ka age models for many cores rely on the stratigraphic correlation of benthic 18o which measures ice volume and deep ocean temperature change the large amount of data available for the last glacial cycle offers the opportunity to improve upon previous benthic 18o compilations such as the lr04 global stack not only are the age constraints for the lr04 stack now outdated but a single global alignment target neglects regional differences of several thousand years in the timing of benthic 18o change during glacial terminations here we present regional stacks that characterize mean benthic 18o change for 8 ocean regions and a volume weighted global stack of data from 263 cores age models for these stacks are based on radiocarbon data from 0 to 40 ka correlation to a layer counted greenland ice core from 40 to 56 ka and correlation to radiometrically dated speleothems from 56 to 150 ka the regional 18o stacks offer better stratigraphic alignment targets than the lr04 global stack and furthermore suggest that the lr04 stack is biased 1 2 kyr too young throughout the pleistocene finally we compare global and regional benthic 18o responses with sea level estimates for the last glacial cycle

sedimentological record of subglacial conditions and ice sheet dynamics of the vistula ice stream north central poland during the last glaciation abstract deposits of the vistula ice stream draining the scandinavian ice sheet during the last glaciation were investigated at four field sites in north central poland using micro and macroscale features the study reveals several till units with specific structural textural and lithological characteristics the individual till units are either macroscopically massive or bedded and the contacts between the units are either sharp or transitional the nature of the contacts with the underlying sediments ductile deformation structures largely undeformed clayey clasts tectonic lamination thin horizontal stringers of sorted sediments ploughing marks boulder pavements and striated upper surfaces of pebbles in the till indicate both bed deformation and enhanced basal sliding under high subglacial water pressure conditions it is suggested that the till is a hybrid deposit generated by some combination of lodgement deformation and ploughing punctuated by periods of basal decoupling the depth of deformation at any point in time was thinner up to several decimetres than the maximum till thickness c 2 5 m the ice sliding velocity estimations indicate velocities of less than 100 to over 2000 m yr 1 which suggests an unstable and highly dynamic ice lobe consistent with spatial variability of till characteristics sand wedges in the deposits beneath the till and the nature of the till bed interface indicate permafrost under the advancing ice sheet we suggest that under the increasing ice thickness a layer of thawed water saturated sediment formed on top of the still frozen ground due to inefficient drainage and contributed to ice streaming by promoting pervasive deformation and basal sliding

fault slip inverted from surface displacements during the 1999 chi chi taiwan earthquake we use coseismic surface displacement data to determine the slip distribution on the chelungpu fault during the 1999 chi chi taiwan earthquake the surface displacements were obtained from both gps surveys and integrations of near field strong ground motions the fault rupture is taken as a series of dislocations along the chelungpu fault in a homogeneous elastic half space using this assumption we are able to find both a least squares solution and optimal solutions from genetic algorithm inversion with a step wise rake constraint our results show that with the rake constraint the resulting rupture features are more reasonable and more consistent with geologic observations than with the least squares solution we also evaluate the influence of fault geometry by calculating slip distributions on a simplified 2d fault plane and a more sophisticated 3d fault surface noting that the 3d rupture model can greatly reduce model misfit when compared with the 2d rupture model both models do show however that slip dramatically increases from the hypocenter toward the northern end of the chelungpu fault and that right lateral slip is found at a large asperity near the southern end of the chelungpu fault at depths below 10 km our models predict a much larger average slip than others derived from body wave inversions we interpret this inconsistency to be a result of partitioning of aseismic sliding due to mineral composition state of stress and or frictional heat

ground surface warming history in northern canada inferred from inversions of temperature logs and comparison with other proxy climate reconstructions well temperature logs from 61 sites located in discontinuous and continuous permafrost regions of northern canada are analyzed the method of functional space inversion fsi is applied to the set of precise temperature logs from wells located between 60 and 82 n there is strong evidence of extensive ground surface temperature gst warming beginning in the late 18th century and lasting until the 20th century this was preceded by a lengthy period of cooling the approximate average increase of the surface temperature of canadian arctic based on all individual gst histories is 1 3 c for the last 200 years simultaneous inversion of all well temperature data suggests an even higher warming approximately 2 c there has been no strong south to north gradient in the ground warming magnitude when northern canadian data are compared with eastern and central canadian data south of 60 n which also shows warming close to 2 c in alaska warming of some 2 c has been restricted mainly to the 20th century in general however a high warming magnitude is common for most of canada and alaska for the previous century the averaged gst history gsth for the canadian arctic is calibrated with and compares visually with a variety of recently published regional and hemispheric proxy climate reconstructions these show that gst warming derived from well temperature logs is generally higher than one shown by other proxy mainly tree ring reconstructions

some reconciliation of glacial interglacial calcite flux reconstructions for the eastern equatorial pacific 1 carbonate production in the open ocean plays a significant role in fixing upper water column pco2 and carbonate flux from the surface transfers alkalinity to the deep sea a key region for this is in the eastern equatorial pacific eep reconstructions of calcite accumulation rates with traditional methods mass accumulation rate mar have been used to infer a large last glacial maximum lgm increase in fluxes for the eep the opposite result has been obtained using thorium normalization th norm of accumulation rates new 14c dating combined with detailed correlation among eep cores based on planktonic and benthic stable isotope records emphasizes the sensitivity of the mar approach to the age model and brings some reconciliation to the methodologies the new results lead to lgm mar based accumulation rates that are less than previously estimated and to lower lgm paleofluxes both the mar and thorium normalized methods show a flux maximum during the deglacial with the new age model although the signals show some convergence the magnitudes of mar accumulation rates appear to be between about 2 and 4 times those from th normalization for the lgm at the sites examined thus sediment focusing inferred from th normalization remains significant for the eep

deriving century long trends of surface temperature change from borehole temperatures we have employed a few parameter estimation fpe technique to derive information on past surface temperature variations from present day borehole temperatures synthetic experiments show that the fpe technique can separate reasonably well information on century long trends of surface temperature change from borehole temperatures within a wide range of noise levels the technique also allows a simple illustration and comparison of the inversion results both spatially and temporally we illustrate this technique by analyzing seventeen borehole temperature profiles from eleven sites in northeast usa and southeast canada utilizing a ground surface temperature model of five ramps of century long duration

stochastic finite fault modeling of ground motions from the 1999 chi chi taiwan earthquake application to rock and soil sites with implications for nonlinear site response the stochastic method for simulating strong ground motions from finite faults is applied to the records of the 1999 chi chi taiwan earthquake the method involves discretization of the fault plane into smaller subfaults each of which is assigned an x 2 spectrum the contributions from all subfaults are empirically atten uated to the observation site and summed to produce the synthetic acceleration time history the method is initially calibrated against the data recorded at 24 rock sites located within 7 120 km from the mainshock hypocenter and providing a broad azimuthal coverage of the fault plane the accuracy of the simulations is quantified through the model bias defined as the logarithm of the ratio of the observed to simulated spectrum averaged over all stations the calibrated model for the chi chi event has a near zero average bias in reproducing the ground motions at rock sites in the frequency range from 0 1 to 20 hz an unusually low value is found for the radiation strength factor s controlling the high frequency radiation level and directly related to the maximum slip velocity on the fault compared with the mean value found for north american earthquakes this result reflects the observed low peak ground ac celerations of the chi chi mainshock and physically its lower than usual slip ve locities the calibrated model is then used to simulate soil site site class d records using the linear response assumption the simulated soil site input motions are amplified by the weak motion amplification functions estimated by the spectral ratio technique from available aftershock records this analysis reveals an average reduction in strong motion amplification to about 0 5 0 6 of that in weak motions with an ac celeration threshold for detectable nonlinearity near 200 300 cm sec 2 however the derivation of soil site specific weak motion amplification was limited by the amount of aftershock data available further improvement in the quantification of nonlinear soil response during the chi chi earthquake may be possible with the release of additional aftershock datasets

geoarchaeological evidence from peru for a 5000 years b p onset of el nino for the tropical west coast of south america where el nino southern oscillation enso is most pronounced archaeological and associated paleontological deposits in northern peru revealed a major climate change at about 5000 years before the present yr b p the data implied the presence of stable warm tropical water as far south as 10 s during the early mid holocene about 8000 to 5000 yr b p these data suggest that enso did not occur for some millennia preceding 5000 yr b p when global and regional climate was warmer than today

large ground warming in the canadian arctic inferred from inversions of temperature logs abstract the simultaneous functional space inversion applied for the first time to the set of precise temperature logs from 61 wells located between 60 and 82 n in northern canada shows evidence of large ground surface temperature gst warming these results include highest latitude locations of the well temperature profiles known in the northern hemisphere there is strong evidence that gst warming started in the late 18th century and lasted until the 20th century simultaneous inversion of all well temperature data suggests that the cumulative ground surface temperature change over the past five centuries amounts to about 2 c significantly exceeding recent estimates from conventional climate proxies this large gst warming is also present in other circumpolar locations in the northern hemisphere

calibration of the c 14 timescale over the past 30 000 years using mass spectrometric u th ages from barbados corals uranium thorium ages obtained by mass spectrometry from corals raised off the island of barbados confirm the high precision of this technique over at least the past 30 000 years comparison of the u th ages with 14c ages obtained on the holocene samples shows that the u th ages are accurate because they accord with the dendrochronological calibration before 9 000 yr bp the 14c ages are systematically younger than the u th ages with a maximum difference of 3 500 yr at 20 000 yrbp the u th technique thus provides a way of calibrating the radiocarbon timescale beyond the range of dendrochronological calibration

fault geometry and the dynamics of the 1999 chi chi taiwan earthquake the 1999 m 7 6 chi chi taiwan earthquake produced a data set of unparalleled size and quality particularly in the near source region where data have been previously quite scarce the large amount of near source data allows the verification of many predictions of thrust fault behavior for faults that intersect the surface of the earth through rigorous three dimensional dynamic models of the chi chi earthquake it can be shown that many aspects of the observed near source ground motion in this event are direct effects of the asymmetrical dipping fault geometry these effects include the hanging wall moving more than the footwall with strongly peaked velocities right at the fault trace and a transition from predominantly thrust motion in the south of the fault to largely left lateral motion in the north building on the work of oglesby and day 2001 the current work helps to delineate the effects of fault geometry nonuniform prestress and dynamic waves on the physics of the chi chi earthquake and dip slip faults in general in particular we find that a completely homogeneous prestress pattern still fits the gross features of the near source ground motion quite well additionally the strike slip component of motion near the fault trace is seen to be a combination of dynamic and static effects finally dynamic overshoot is seen to be much larger for dip slip faults than for otherwise identical vertical faults the results emphasize the necessity of rigorous models that correctly account for both the effects of fault geometry and dynamic waves in the rupture and slip processes manuscript received 31 july 2000

east to west retardation in the onset of the recent warming across canada inferred from inversions of temperature logs 1 canadian well temperature logs for 141 sites are analyzed and show evidence of extensive ground surface temperature gst warming beginning in the eighteenth and nineteenth centuries following a lengthy period of cooling the little ice age over most of the past millennium the method of functional space inversion fsi is applied to the complete set of 141 well precise temperature logs from wells located in low conductivity clastic sediments of the western canadian sedimentary basin and higher thermal conductivity crystalline rocks of the canadian shield in central and eastern canada marked regional differences in the onset of recent warming are evident nineteenth century compared to the seventeenth to eighteenth centuries respectively following a prolonged cold period through earlier centuries analysis of spatial patterns of gst history changes across canada based on the individual inversions of temperature logs shows a systematic east to west retardation in the onset of the recent warming yet a higher overall warming magnitude in western canada in the twentieth century

nonlinear behavior of soils revealed from the records of the 2000 tottori japan earthquake at stations of the digital strong motion network kik net acceleration records of the tottori earthquake 6 october 2000 pro vided by stations of the digital strong motion network kik net show clear evidence of the nonlinearity of soil response at sites located in near fault zones in this study records of the mainshock of the tottori earthquake are analyzed and stresses and strains induced by the strong motion in the upper 100 or 200 m of soil are recon structed at sites located within 80 km from the fault plane for reconstructing stresses and strains the method is applied which we developed and used previously for studying the response of soils during the 1995 kobe earthquake nonlinear time dependent stress strain relations in the soil layers are estimated based on vertical array records a good agreement between the observed and simulated accelerograms of the tottori earthquake testifies to the validity of the obtained vertical distributions of stresses and strains in the soil layers we also evaluated variations of the shear moduli of the soil layers caused by the strong motion at stations located at different distances from the fault plane changes in the rheological properties of the upper soil layers were found at the stations closest to the fault plane a similarity in stress strain relations describing the behavior of similar soils during the 1995 kobe earth quake and the 2000 tottori earthquake was obtained indicating the possibility of precasting soil behavior in future earthquakes at sites where profiling data are available

the impact of cold north atlantic sea surface temperatures on climate implications for the younger dryas cooling 11 10 k the sensitivity of global climate to colder north atlantic sea surface temperatures is in vestigated with the use of the giss general circulation model north atlantic ocean temperatures 18 000 b p resembling those prevalent during the younger dryas were incorporated into the model of the present climate and also into an experiment using orbital parameters and land ice characteristic of 11 000 b p the results show that with both 11 000 b p and present conditions the colder ocean temperatures produce cooling over western and central europe in good agreement with younger dryas paleoclimatic evidence cooling also occurs over extreme eastern north america although the precise magnitude and location depends upon the specification of ocean temperature change in the western atlantic despite the presence of increased land ice and colder ocean temperatures the younger dryas summer air temperatures at northern hemisphere midlatitudes in the model are warmer than those of today due to changes in the orbital parameters chiefly precession and atmospheric subsidence at the perimeter of the ice sheets

variation in holocene el nino frequencies climate records and cultural consequences in ancient peru analysis of mollusks from archaeological sites on the north and central coasts of peru indicates that between ca 5800 and 3200 2800 cal yr b p el nino events were less frequent than today with modern rapid recurrence intervals achieved only after that time for several millennia prior to 5 8 ka el nino events had been absent or very different from today the phenomena called el nino have had severe consequences for the modern and colonial historically recorded inhabitants of peru and el nino events also influenced prehistoric cultural development the onset of el nino events at 5 8 ka correlates temporally with the beginning of monumental temple construction on the peruvian coast and the increase in el nino frequency after 3 2 2 8 ka correlates with the abandonment of monumental temples in the same region

mid holocene regional reorganization of climate variability analyses of proxy data in the frequency domain abstract recurrent shifts in holocene climate define the range of natural variability to which the signatures of human interference with the earth system should be compared characterization of holocene climate variability at the global scale becomes increasingly accessible due to a growing amount of paleoclimate records for the last 9000 11 000 yr here we integrate 124 proxy time series of different types e g 18o lithic composition and apply a modified lomb scargle spectral analysis after bootstrapping the data in moving time windows we observe an increased probability for generation or loss of periodic modes at the mid holocene spatial autocorrelation of spectral changes robustly reveals that this in activation of modes was organized in regional clusters of sub continental size within these clusters changes in spectral properties are unexpectedly homogeneous despite different underlying climatological variables oscillations in the climate system were amplified especially at the upwelling areas and dampened in the north atlantic we cross checked the spectral analysis by counting events in the time series and tested against possible dating errors in individual records or against an overestimation of singular events a combination of different mechanisms may have affected the coupling intensity between climate subsystems turning these more or less prone to oscillations

estimation of nonlinear soil behavior during the 1999 chi chi taiwan earthquake the 1999 chi chi taiwan earthquake mw 7 6 was one of the strongest earthquakes in recent years recorded by a large number of strong motion devices though only surface records are available the obtained strong motion database indicates the variety of ground responses in the near fault zones in this study accelerograms of the chi chi earthquake were simulated at rock and soil sites and models of soil behavior were constructed at seven soil sites tcu065 tcu072 tcu138 chy026 chy104 chy074 and chy015 for which parameters of the soil profiles are known down to depths of at least 70 m and at 24 other soil sites for which parameters of the soil profiles are known down to 30 40 m all the sites were located within 50 km from the fault for reconstructing stresses and strains in the soil layers we used a method similar to that developed for the estimation of soil behavior based on vertical array records as input for the soil layers acceleration time histories simulated by stochastic finite fault modelling with a prescribed slip distribution over the fault plane were taken in spite of the largeness of the earthquake s magnitude and the proximity of the studied soil sites to the fault plane the soil behavior at these sites was relatively simple i e a fairly good agreement between the spectra of the observed and simulated accelerograms and between their waveforms was obtained even in cases where a single stress strain relation was used to describe the behavior of whole soil thickness down to 70 80 m during strong motion obviously this is due to homogeneity in the characteristics of soil layers in depth at all the studied sites resonant phenomena in soil layers down to 40 60 m and nonlinearity of soil response were the main factors defining soil behavior at tcu065 tcu110 tcu115 chy101 chy036 and chy039 liquefaction phenomena occurred in the upper soil layers estimated strains achieved 0 6 0 8 at other stations maximum strains in the soil layers were as high as 0 1 0 4 according to our estimates thus valuable data on the in situ soil behavior during the chi chi earthquake was obtained similarity in the behavior of similar soils during the 1995 kobe 2000 tottori japan and chi chi taiwan earthquakes was found indicating the possibility of forecasting soil behavior in future earthquakes in the near fault zones of the three earthquakes hard type soil behavior and resonant phenomena in the upper surface layers prevail both leading to high acceleration amplitudes on the surface

el nino like pattern in ice age tropical pacific sea surface temperature sea surface temperatures ssts in the cold tongue of the eastern equatorial pacific exert powerful controls on global atmospheric circulation patterns we examined climate variability in this region from the last glacial maximum lgm to the present using a sst record reconstructed from magnesium calcium ratios in foraminifera from sea floor sediments near the galapagos islands cold tongue sst varied coherently with precession induced changes in seasonality during the past 30 000 years observed lgm cooling of just 1 2 c implies a relaxation of tropical temperature gradients weakened hadley and walker circulation southward shift of the intertropical convergence zone and a persistent el nino like pattern in the tropical pacific this is contrasted with mid holocene cooling suggestive of a la nina like pattern with enhanced sst gradients and strengthened trade winds our results support a potent role for altered tropical pacific sst gradients in global climate variations

estimation of ground surface temperatures from borehole temperature data to infer past climatic changes from temperatures measured in boreholes one must obtain reliable estimates of ground surface temperature gst histories from these data this paper presents a method that uses a bayesian inverse technique to estimate the gst in the fourier frequency domain by assuming the a priori gst to be stationary with a prescribed standard deviation and a cutoff period the time series is constrained to be bounded and smooth because accounting for conductivity variations with depth is crucial to the estimation of gst a layered earth medium has been used for which the forward analytical solution of one dimensional heat conduction is available borehole data from flin flon and lac dufault in canada are inverted with this method the flin flon hole logged to a depth of 2900 m provides an opportunity to study long term gst variations and the estimated gst from this hole shows some effects of deglaciation at the end of pleistocene at lac dufault similar gsts were obtained independently from three holes ranging from 550 to 900 m and hence the results are considered more reliable in the lac dufault gsts there is a warm period centered about 1000 years bp and a cold period about 400 years b p confirming the presence of the little climatic optimum and the little ice age respectively the flin flon result does not show the little climatic optimum and the little ice age occurs about 100 200 years earlier however in both locations the gsts show another brief cold period around the turn of the century followed by rapid warming until 1940 1950 in good agreement with the trend of northern hemisphere surface air temperatures

geothermal gradients and terrestrial heat flow along a south north profile in the sverdrup basin canadian arctic archipelago data from eleven petroleum exploration wells along a south north profile in the sverdrup basin of the canadian arctic islands indicate large variations in temperature gradients 18 2 to 39 2 mk m and heat flow values 38 8to73 11mw m2 high values occur near the axis of the basin and values decrease systematically toward the southern and northern flanks of the basin the basin axis in this area is the zone of maximum crustal attenuation and lower cretaceous dike and sill intrusion but any thermal anomaly associated with these events will have dissipated by now the present heat flow pattern is likely the result of thermal refraction or fluid flow in the basin

holocene changes in eastern tropical pacific climate inferred from a galapagos lake sediment record abstract paleoclimate records from the tropical pacific suggest the early to mid holocene was a period of reduced el nino southern oscillation enso variability with a transition to modern increased enso frequency occurring some time in the last few thousand years however the nature and timing of this shift remains uncertain due to the discontinuous nature and or coarse resolution of many enso proxies as well as a lack of agreement between previously published records a new continuous climate record from el junco crater lake in the galapagos islands reveals several abrupt changes in lake level and precipitation through the holocene hydroclimatic model simulations suggest that el junco lake level responds sensitively to increases in precipitation associated with el nino events rising during wet el nino events and falling during the intervening dry periods grain size data from el junco sediment cores indicate past lake level variability likely associated with changing seasonal precipitation and enso frequency the grain size data suggest increased precipitation intensity prior to 9000 120 cal years bp and after 4200 130 cal years bp as well as a two step increase in precipitation at 3200 160 and 2000 100 cal years bp maximum holocene precipitation and inferred enso variability occurred between 2000 100 and 1500 70 cal years bp during the same period that six other independent proxy records suggest higher enso frequency and longer stronger el nino events decreasing sediment carbon nitrogen c n ratios in el junco sediments indicate rising lake levels from the early holocene to present corroborating the grain size data the inferred increase in precipitation at 4200 130 cal years bp and at 2000 100 cal years bp coincides with decreasing southwest asian and east asian monsoon intensity suggesting tropical pacific climate and the asian monsoon were interconnected systems at centennial to millennial timescales during the holocene a weakening trend in the asian monsoon and the trend toward wetter conditions at el junco also coincide with a trend toward cooler and drier conditions inferred from cariaco basin sediment proxies from the mid holocene to present suggesting the migration of the intertropical convergence zone itcz likely influenced hydrological changes in both the eastern tropical pacific and the asian monsoon region during the holocene

marine transgression shoreline emergence evidence in seabed and terrestrial ground temperatures of changing relative sea levels arctic canada precise temperatures to depths of several hundred meters have been measured in abandoned petroleum exploration wells in coastal and offshore areas of the canadian arctic in these regions changes in relative sea level during the quaternary have left a strong thermal signature on deep ground temperatures surface temperature changes of the order of 10 20 k accompanied shoreline emergence due to uplift in some regions and marine transgression due to eustatic changes in sea levels in others classical analytic techniques are used to demonstrate that these anomalous features are a direct consequence of recent changes in sea level in coastal areas of the queen elizabeth islands modelling of the large near surface temperature depth gradients and the distinct curvature in the measured profiles yield emergence times in general agreement with dates taken from emergence curves the analysis suggests that surface temperatures of these coastal areas were 16 19 k higher than at present from the late wisconsinan until emergence in the holocene suggesting either marine conditions for this period or glacial ice cover with basal temperatures near the pressure melting point in contrast at two offshore wells on the beaufort shelf analyses of the negative temperature depth gradients below the seabed and profile curvature yield times of marine transgression generally consistent with the published sea level curve for the area the analyses suggest that surface temperatures of some present offshore areas were 10 16 k lower than today s sea bottom temperatures from the late wisconsinan until marine transgression in the holocene the characteristic ground temperature profiles measured in such arctic areas provide independent evidence for the relative changes in sea level indicated by proxy data it is especially valuable for these areas where there is little historical record and from which datable material such as shells driftwood and pumice fragments may be scarce or ambiguous these effects may not be observable in temperate areas because of the smaller contrast in sea bottom and terrestrial temperatures

changes in silicate utilisation and upwelling intensity off peru since the last glacial maximum insights from silicon and neodymium isotopes we combine the stable silicon isotope composition 30si of diatoms and the radiogenic neodymium isotope compositions end of past seawater extracted from the authigenic fraction of the sediments mn fe coatings of particles and benthic foraminifers as well as the radiogenic isotope compositions nd sr of the detrital material itself to reconstruct silicic acid utilisation water mass mixing and upwelling intensity from the same marine sediments in the peruvian upwelling region during the past 20 000 years additionally the sedimentary signals were compared to the water column isotope compositions along the peruvian shelf the dissolved end in the water column ranges from 5 7 to 0 6 the corresponding end signatures of the coatings and the benthic foraminifers of the surface sediments range from 4 5 to 1 8 and from 2 5 to 2 2 respectively the detrital end 87sr 86sr signatures range from 6 3 to 0 0 70508 0 71049 all phases show a trend from more radiogenic end values in the north towards less radiogenic values in the south broadly reflecting local weathering inputs and hinterland geology the end signatures of the coatings extracted from sediment core so147 106kl located in the present day centre of coastal upwelling near 12 s have been essentially constant 1 5 throughout the past 20 000 years while the detrital end 87sr 86sr varied between values of 0 7 0 70620 during the last glacial and 4 5 0 70849 during the late holocene reflecting changes in the origin of the sediment and current transport from a more northerly towards a more southerly source and from overall stronger to weaker upwelling the 30si signature of both total biogenic opal 30siopal and of hand picked diatoms 30sidiatom ranged from 0 3 last glacial to 1 4 late holocene confirming large variations in upwelling intensity driving silicic acid utilisation by diatoms our combined bsio2 mar 30siopal and detrital radiogenic isotope results demonstrate that the strongest el nino southern oscillation conditions off peru of the past 20 ka have prevailed during the past 5 ka

forms response times and variability of relative sea level curves glaciated north america abstract relative sea level curves from glaciated north america reveal coherent spatial patterns of response times in the laurentide ice sheet area curve half lives range from 1 2 1 4 ka at the uplift centre to 1 7 2 ka in a ridge of high values inboard of the glacial limit half lives decline from this ridge to less than 1 ka along the margin in the innuitian ice sheet area half lives are about 2 ka at the uplift centre and decline to less than 1 ka at the margin the central laurentide response times are about half those of central fennoscandia this accords with the theoretical expectation that central response times are inversely proportional to ice sheet radius for ice loads large enough that rebound at the centre is insensitive to lithospheric thickness the innuitian central response time indicates that rebound at the centre of this ice sheet which is much smaller than the fennoscandian ice sheet remains sensitive to lithospheric thickness radial gradients in response times reflect the increasing influence of the lithosphere at sites increasingly closer to the margin along this gradient rebound progresses as though at the centres of smaller and smaller ice sheets that is the effective spatial scale of the ice load decreases toward the margin near the glacial limit postglacial isostatic adjustment is complicated by forebulge migration and collapse this is seen most strongly in the relative sea level record of atlantic canada which has subsided during the holocene more than 20 m more than the adjacent american seaboard the relative sea level history of some areas notably the st lawrence estuary is complicated by tectonic processes

a rainy northern atacama desert during the last interglacial 1 the response of the northern extension of the atacama desert and the peruvian upwelling system to climate conditions during the last interglacial lig 125kyr ago was tracked using molecular fossils of marine and terrestrial organisms preserved in peruvian shelf sediments high resolution records of odp site 1229 past 145 kyr indicated that warmer and wetter conditions rainfall and river runoff along the coast occurred during the lig when global temperatures were comparable or even higher than today a 3 c warming of surface waters enhanced water column stratification rainfall and river runoff were associated with low primary productivity and a 1 5 c decrease in the temperature gradient across the equatorial pacific i e weak walker circulation suggesting a prolonged el nino like response of the tropical pacific during the lig in contrast the late holocene lh last 3 kyr was characterized by colder surface waters higher export and primary productivity and a drier climate

permafrost heat flow and the geothermal regime at prudhoe bay alaska temperature measurements through permafrost in the oil field at prudhoe bay alaska combined with laboratory measurements of the thermal conductivity of drill cuttings permit an evaluation of in situ thermal properties and an understanding of the general factors that control the geothermal regime a sharp contrast in temperature gradient at approx 600 m represents a contrast in thermal conductivity caused by the downward change from interstitial ice to interstitial water at the base of permafrost under near steady state conditions interpretation of the gradient contrast in terms of a simple mode for the conductivity of an aggregate yields the mean ice content approx 39 and thermal conductivities for the frozen and thawed section 8 1 and 4 7 mcal cm s sup 0 c respectively these results yield a heat flow of approx 1 3 hfu which is similar to other values on the alaskan arctic coast the anomalously deep permafrost is a result of the anomalously high conductivity of the siliceous ice rich sediments curvature in the upper 160 m of the temperature profiles represents a warming of approx 1 8 sup 0 c of the mean surface temperature and a net accumulation of 5 6 kcal cm sup 2 by the solid earth surface during the last 100 years or so rising sea levelmore and thawing of ice rich sea cliffs probably caused the shoreline to advance tens of kilometers in the last 20 000 years inundating a portion of the continental shelf that is presently the target of intensive oil exploration a simple conduction model suggests that this recently inundated region is underlain by near melting ice rich permafrost to depths of 300 500 m its presence is important to seismic interpretations in oil exploration and to engineering considerations in oil production with confirmation of the permafrost configuration by offshore drilling heat conduction models can yield reliable new information on the chronology of arctic shorelines less

foraminiferal faunal estimates of paleotemperature circumventing the no analog problem yields cool ice age tropics the sensitivity of the tropics to climate change particularly the amplitude of glacial to interglacial changes in sea surface temperature sst is one of the great controversies in paleoclimatology here we reassess faunal estimates of ice age ssts focusing on the problem of no analog planktonic foraminiferal assemblages in the equatorial oceans that confounds both classical transfer function and modern analog methods a new calibration strategy developed here which uses past variability of species to define robust faunal assemblages solves the no analog problem and reveals ice age cooling of 5 o to 6oc in the equatorial current systems of the atlantic and eastern pacific oceans classical transfer functions underestimated temperature changes in some areas of the tropical oceans because core top assemblages misrepresented the ice age faunal assemblages our finding is consistent with some geochemical estimates and model predictions of greater ice age cooling in the tropics than was inferred by climate long range investigation mapping and prediction climap 1981 and thus may help to resolve a long standing controversy our new foraminiferal transfer function suggests that such cooling was limited to the equatorial current systems however and supports climap s inference of stability of the subtropical gyre centers

source process of the chi chi earthquake a joint inversion of strong motion data and global positioning system data with a multifault model the chi chi taiwan earthquake of 21 september 1999 was a large thrust earthquake that caused disastrous damage the surface fracture trace runs along the chelungpu fault which strikes n5 e along most of the faulting area but turns to the northeast while approaching its northern end it finally presents a horsetaillike faulting system and bends to an east northeast direction at the northern end both strong motion and global positioning system gps data recorded large displace ments in the northern part in this study we use a multifault model to simulate the observed large strong motion and gps data the results of the joint inversion reveal that in the southern part slip occurred mainly in the shallow portion reaching a maximum about 20 m on the ene fault where the rupture propagated to the deep part of the fault there was obviously slip vector rotation from south to north such that the slip on the branched fault plane was almost purely reverse faulting the seismic moment a total of 2 7 10 20 n m was released in less than 40 sec during the mainshock aftershocks occurred mainly in areas where little or no slip occurred slip vector rotation can be explained by the complexity of regional tectonic stress changes in tectonic stress at the northern end of the fault inhibited the northward propagation of the rupture and favored the rupturing of the ene fault

comparison of isotopic composition of planktonic foraminifera in plankton tows sediment traps and sediments planktonic foraminifera from plankton tows sediment traps and sediments in the central north atlantic were studied in order to understand what determines their oxygen and carbon isotope composition a clear separation of species and genera on a 18o vs 13c plot for all samples suggests that their isotopic composition is controlled to a certain degree by biological factors within a species population the globorotaliids show a positive linear correlation between 18o and 13c while the shallow dwelling spinose species mostly globigerinoides species do not show a definite trend the latter species when collected in plankton tows often show slight negative deviations from isotopic equilibrium with respect to oxygen all species deviate from carbon isotope equilibrium by 1 5 to 6 these deviations from equilibrium are probably caused by incorporation of isotopically light metabolic co2 into the skeleton which is enhanced by the activity of symbiotic algae during their ontogeny the average weight per individual of most species increases which indicates that calcification continues to a depth of about 100 m this additional skeleton roughly 50 by weight is isotopically heavier because temperatures are lower and photosynthesis of symbiotic algae stops below the photic zone therefore the skeleton of foraminifera collected in sediment traps below 400 m has an overall oxygen isotope composition that seems to be in equilibrium for caco3 deposited in the upper 100 m