persistence in intra annual snow depth distribution 1 measurements and topographic control 1 terrestrial and airborne laser scanning tls and als techniques have only recently developed to the point where they allow wide area measurements of snow distribution in varying terrain in this paper we present multiple tls measurements showing the snow depth development for a series of precipitation events we observe that the pattern of maximum accumulation is similar for the two years presented here correlation up to r 0 97 storms arriving from the northwest show persistent snow depth distributions and contribute most to the final accumulation pattern snow depth patterns of maximum accumulation for the two years are more similar than the distribution created by any two pairs of individual storms based on the strong link between accumulation patterns and terrain we investigated the ability of a model based on terrain and wind direction to predict accumulation patterns this approach of winstral et al 2002 which describes wind exposure and shelter was able to predict the general accumulation pattern over scales of slopes but failed to match observed variance furthermore a high sensitivity to the local wind direction was demonstrated we suggest that winstral et al s model could form a useful tool for application from hydrology and avalanche risk assessment to glaciology

warming at 18 000 yr b p in the tropical andes abstract palynological paleopedological and glacial geomorphological evidence from the area of the high plain of bogota in the colombian eastern cordillera indicates a significant climatic warming around 18 00014c yr b p comparison of dated vegetation changes pedogenic episodes and glacier fluctuations provides the basis for defining the so called la laguna interstadial that lasted from 19 500 to 17 000 yr b p during this interstadial period mean annual temperatures in the tropical andes were up to 4 c higher than during the preceding and following stadial periods when full glacial conditions prevailed and temperatures were up to 8 c colder than at present

a snow transport model for complex terrain as part of the winter environment in middle and high latitude regions the interactions between wind vegetation topography and snowfall produce snow covers of non uniform depth and snow water equivalent distribution a physically based numerical snow transport model snowtran 3d is developed and used to simulate this three dimensional snow depth evolution over topographically variable terrain the mass transport model includes processes related to vegetation snow holding capacity topographic modification of wind speeds snow cover shear strength wind induced surface shear stress snow transport resulting from saltation and suspension snow accumulation and erosion and sublimation of the blowing and drifting snow the model simulates the cold season evolution of snow depth distribution when forced with inputs of vegetation type and topography and atmospheric foreings of air temperature humidity wind speed and direction and precipitation model outputs include the spatial and temporal evolution of snow depth resulting from variations in precipitation saltation and suspension transport and sublimation using 4 years of snow depth distribution observations from the foothills north of the brooks range in arctic alaska the model is found to simulate closely the observed snow depth distribution patterns and the interannual variability

surface and subsurface seawater temperature reconstruction using mg ca microanalysis of planktonic foraminifera globigerinoides ruber globigerinoides sacculifer and pulleniatina obliquiloculata laser ablation inductively coupled plasma mass spectrometry microanalyses of mg ca across individual final chambers of three planktonic foraminifera species globigerinoides ruber g sacculifer and pulleniatina obliquiloculata reveal significant interspecies differences in test mg concentrations whereas these three species have similar mg ca values at low sea surface temperatures similar to 22 degrees c they diverge markedly at high sea surface temperatures similar to 29 degrees c explanations for these differences in species mg ca values based on detailed comparison of species intratest mg ca distributions suggest that compositional variability within tests cannot account for the observed deviation of species mg ca values in warm water equatorial regions multiple regression modeling and delta o 18 analysis of globigerinoides sacculifer tests indicate that interspecies differences in mg ca values result from different depth habitats the average mg ca values of g ruber final chambers reflect the temperature of the surface mixed layer 0 25 m whereas those of g sacculifer and pulleniatina obliquiloculata correlate best with subsurface temperatures at 50 75 m and 100 125 m water depths respectively mg ca calibration to the temperatures at these depths reveals a similar temperature control on mg test composition in all species combining our results with mg ca values from published culturing experiments we derive a generalized equation for the effect of temperature and seawater salinity on foraminiferal mg ca we also show that the mg ca composition of specific calcite layers within foraminiferal tests including the low mg ca layers of globigerinoides ruber and g sacculifer and the cortex layer of pulleniatina obliquiloculata correlates with seawater temperature and can be used as an additional proxy for seawater temperature

the role of ocean atmosphere reorganizations in glacial cycles abstract a case is made that glacial to interglacial transitions involve major reorganizations of the ocean atmosphere system such reorganizations constitute jumps between stable modes of operation which cause changes in the greenhouse gas content and albedo of the atmosphere only in this way can the rapidity of glacial terminations the hemispheric synchroneity and symmetry of mountain glaciation and the large polar air temperature and dustiness variations be accounted for if these reorganizations are driven in some fashion by orbitally induced seasonal insolation changes then the connection between insolation and climate is most likely through impacts of fresh water transport on the ocean s salinity distribution

deglacial warming of the northeastern atlantic ocean correlation with the paleoclimatic evolution of the european continent abstract isotopic micropaleontologic and pollen analyses of deep sea cores from the bay of biscay and the northeastern atlantic ocean show that the deglacial warming of this oceanic area was closely correlated with the paleoclimatic evolution of the adjacent european continent temperatures were at least as warm as those of today in the bay of biscay between 13 300 and 11 000 b p coinciding with the combined bolling allerod warm continental events a major spread of polar water occurred between 11 000 and 10 000 b p during this event which coincides with the younger dryas continental cold event marine temperatures were almost as low as those of the last glacial maximum the final deglacial warming of the norteastern atlatntic ocean occurred during the following 3000 yr

conference on the last deglaciation timing and mechanism abstract for years paleoclimatologists have held the general view that the last deglaciation began around 17 000 to 15 000 yr ago that the shape of the globally integrated deglacial curve was smoothly sigmoidal with the fastest rate of change centered around 11 000 yr ago and that the deglaciation ended around 7000 to 5000 yr ago recent studies have challenged several aspects of this consensus and have suggested that the mechanisms responsible for the deglaciation are significantly different from those previously proposed as a result an international workshop was held at airlie house in virginia during may 2 6 of 1983 to evaluate a wide range of evidence relevant to this controversy the conference results suggested that 1 the decrease in global ice volume occurred in two steps with the dating of the earlier step still in doubt but the later step occurring at about 10 000 7000 yr ago and 2 the most likely feedback mechanisms for accelerating the initial forcing by orbital variations are delayed bedrock rebound marine downdraw calving and co 2 heating

fine scale modeling of the boundary layer wind field over steep topography 1 this paper describes the adaptation of wind fields to steep and complex terrain using fine scale numerical modeling the work is motivated by the need of high resolution flow fields to predict snow transport and snow cover development for avalanche warning purposes applying the nonhydrostatic and compressible atmospheric prediction model advanced regional prediction system arps to steep alpine topography the boundary layer flow was simulated and evaluated against measurements the adaptation of the wind field to steep terrain for specific initial and boundary conditions was simulated the topography used in our study has a length scale of 500 m a typical height of 150 m and maximum slopes of 45 numerical experiments with idealized triangular ridges were conducted to find an adequate model configuration this analysis indicates that a high resolution grid with horizontal spacing of at least 25 m and vertical spacing of 3 m near the surface is necessary to reproduce small scale flow features such as speed up separation and recirculation the onset of flow separation is highly sensitive to initial and boundary conditions slope angle and surface roughness the results of the comparison between the model simulations and measurements on our experimental site show that typical wind field characteristics are well reproduced the simulated wind fields have been used to drive a numerical three dimensional snow drift model which is presented in a companion paper by lehning et al 2008

observations of boundary layer structure over complex terrain turbulence data collected in an area of complex terrain using a number of instrument packages attached to the tether cable of a captive balloon are presented eddy correlation measurements of the turbulent momentum flux are used to determine the magnitude of the roughness length from the drag coefficient and also to show that the roughness length is a useful concept in parametrizing the surface stress in such areas the relationship between the terrain characteristics and the roughness length is examined using a simple formula results from a numerical model and previous experimental estimates of the roughness length for complex terrain it is found that a formula based on numerical model results for separated flows gives reasonable predictions and that the measured roughness length is representative of an area of order 100 km2 non dimensionalized turbulence data are compared with similar data obtained over flat homogeneous surfaces this comparison suggests that the structure of the turbulent boundary layer over complex terrain is remarkably similar to that over flat homogeneous surfaces because of the limitations of fixed point measurements in complex terrain results from a numerical study of turbulent flow over two dimensional sinusoidal orography are shown to indicate the magnitudes of the perturbations introduced into the boundary layer flow by large undulations in the underlying surface the model results demonstrate the validity of the analysis carried out with the data

mineralogy textures and relative age relationships of massive sulfide ore in the west shasta district california the devonian massive sulfide orebodies of the west shasta district in northern california are composed primarily of pyrite with lesser amounts of other sulfide and gangue minerals examination of polished thin sections of more than 100 samples from the mammoth shasta king early bird balaklala keystone and iron mountain mines suggests that mineralization may be divided into six paragenetic stages the last five each separated by an episode of deformation 1 precipitation of fine grained locally colloform and framboidal pyrite and sphalerite 2 deposition of fine grained arsenopyrite and coarse grained pyrite the latter enclosing tiny inclusions of pyrrhotite 3 penetration and local replacement of sulfide minerals of stages 1 and 2 along growth zones and fractures by chalcopyrite sphalerite galena ten nantite pyrrhotite bornite and idaite 4 recrystallization and remobilization of existing minerals locally increasing their size and euhedralism and promoting their aggregation 5 deposition of quartz white mica chlorite and calcite and 6 formation of bornite digenite chalcocite and covellite during supergene enrichment of several orebodies at the iron mountain mine despite regional greenschist facies metamorphism and local heating by intrusive bodies enough of the original depositional features of the ore remain to suggest that the deposits in the district formed by processes similar to those that formed kuroko and besshi type massive sulfide deposits mineralogic and textural evidence do not support a second major episode of massive sulfide mineralization during the permian

response of western pacific marginal seas to glacial cycles paleoceanographic and sedimentological features abstract this paper reviews the recent progress in late quaternary studies in five northwestern pacific marginal seas especially the south china sea as an example a series of marginal seas separate asia from the pacific ocean and significantly modify the material and energy flux linkage between land and sea during glacial cycles the sea level induced environmental signal was amplified in the marginal seas giving rise to drastic changes in areas and configurations of these seas and to reorganization of sea water circulation in basins since most of the western pacific marginal seas are influenced by monsoon circulation and some of these are located within the western pacific warm pool the glacial geographic changes have produced a profound impact on regional and global climate for example the decrease of sea area and sea surface temperature sst in the marginal seas was one of the factors responsible for the enhanced aridity of inland china during the glaciation glacial intensification of the winter monsoon and increased seasonality of sst in marginal seas might explain at least partly the apparent discrepancy between the tropical paleotemperature estimations based on terrestrial and open ocean records in this region as the western pacific marginal seas trap terrigenous material supplied by east asia the deep water sedimentation rates there can be one to two orders of magnitude higher than in the open ocean down slope sediment transport is more active when the sea level changes particularly during the deglaciation at least four types of carbonate cycles have been recognized in the western pacific marginal seas and each of those contains environmental signals from the surface and deep sea water as well as from the drainage basin

radiocarbon based chronology for the 18o 16o record for the last deglaciation a radiocarbon calibrated box model for today s ocean suggests that a lag of about 1750 years should exist between the arrival of the midpoint of the deglaciation 18o signal in the deep atlantic ocean and its arrival in the deep pacific ocean in order to assess the actual lag we have carried out accelerator radiocarbon measurements on two cores from the atlantic ocean and one core from the pacific ocean although the results are not definitive there is a suggestion that the actual time lag was about 1000 years

high resolution isotope study of the latest deglaciation based on bermuda rise cores abstract a stable isotope and 14c investigation of carbonates from three late quaternary cores with high rates of sedimentation from the northeastern bermuda rise has produced the highest resolution record of the glacial maximum to holocene stable isotope change yet obtained from an open ocean location the record includes a three step termination and the first direct evidence of an early deglacial meltwater spike in the open sea

assessing the global meltwater spike abstract l v worthington 1968 meteorological monographs 8 63 67 hypothesized that a low salinity lid covered the entire world ocean by deconvolving isotopic curves from the western equatorial pacific and equatorial atlantic w h berger r f johnson and j s killingley 1977 nature london 269 661 663 and w h berger 1978 deep sea research 25 473 480 reconstructed meltwater spikes similar to those actually observed in the gulf of mexico and thus apparently confirmed the worthington hypothesis it is shown that this conclusion is unwarranted the primary flaw in the reconstructed meltwater spikes is that the mixing intensity used in the deconvolution operation is overestimated as a result structure recorded in the mixed isotopic record becomes exaggerated in the attempt to restore the original unmixed record this structure can be attributed to variable ice volume decay during deglaciation effects of differential solution on planktonic foraminifera temporal changes in abundance of the foraminifera carrying the isotopic signal and analytical error an alternative geographic view to the global low salinity lid is offered a map showing portions of the ocean potentially affected by increased deglacial meltwater at middle and high latitudes and by increased precipitation induced runoff at low and middle latitudes

deep sea benthic foraminifera and biogenic opal glacial to postglacial productivity changes in the western equatorial pacific the accumulation rate of benthic foraminifera in deep sea sediments is strongly correlated with the productivity of the surface ocean core tops from diverse deep sea settings straddling different export production levels are used in this study for the calibration between the organic carbon flux to the seafloor jsf flux and the benthic foraminifera accumulation rate bfar the correlation can be used to reconstruct organic carbon flux to the seafloor in the past and hence the productivity of past oceans these results are compared with the accumulation rates of carbonate and biogenic opal in the sediments it is found that biogenic opal is more sensitive to productivity changes in the modern ocean than is carbonate the appropriate equations are derived for the equatorial pacific using core material fromeurydice erdc indomed inmd andpleiades plds expeditions these equations are then applied to two selected time horizons in sediments from the ontong java plateau a western equatorial pacific pelagic depth transect the last transition lt and the last glacial lg it is found that productivity was higher during the last glacial relative to the late holocene by a factor between 1 6 and 2 during the last transition productivity was intermediate between glacial and recent values we do not see any corresponding increase in the rates of accumulation of carbonate or biogenic opal during the last glacial this observation questions the importance of ocean productivity as the main controlling factor of carbonate and biogenic opal accumulation rates back through geological time

shelf sequence and characteristic bounding surfaces in a wave dominated setting latest pleistocene holocene examples from northeast japan abstract this paper presents modern models for coastal to shelf sequences in a microtidal and wave dominated setting based on detailed analyses of latest pleistocene holocene sequences on the pacific side of northeast japan the latest pleistocene holocene sequences on the pacific side of northeast japan created in response to sea level changes for the last 30 kyr can be assigned to lowstand transgressive and highstand systems tracts related to sea level changes and show characteristic bounding surfaces and depositional systems these basically support the sequence architecture model of vail however transgression and regression occurred almost simultaneously with rise and fall of sea level in the study areas and so inflection points of sea level curves where the absolute slope or the rate of change is greatest are less significant for these high frequency sequences the characteristic bounding surfaces are a sequence boundary a transgressive surface which is the boundary between the lowstand and the transgressive systems tracts a ravinement surface which is found mainly in deposits of the transgressive systems tract and a maximum flooding surface which is the boundary between the transgressive and the highstand systems tracts the sequence boundary was created in response to falling sea level fluvial entrenchment shifted seaward with falling sea level therefore the boundary is a time transgressive unconformity and is not an isochronous boundary the transgressive surface is a nearby isochronous boundary that occurred when the shoreline had started to move landward from its maximum seaward excursion the ravinement surface is a diachronous surface created by shoreface erosion during transgression the shoreface erosion shifted landward with rising sea level and so the erosion surface created is time transgressive this surface is the most distinct bounding surface in the shelf sequence these characteristics of the bounding surfaces support and clarify the model of thorne and swift 1991 the transgressive systems tract on the shelf can be divided into two backstepping wedges separated by the ravinement surface the lower wedge consists of coastal plain and fluvial systems and the upper wedge is composed of transgressive sand and or sand ridges both the wedges show a backstepping depositional pattern which can be recognized in seismic records and cores these wedges correspond to the backstep backbarrier wedge and backstep shelf wedge of thorne and swift 1991 respectively

box cores from the equatorial pacific 14c sedimentation rates and benthic mixing abstract carbon 14 determinations on box cores of calcareous ooze from the western and eastern equatorial pacific suggest that patterns of mixed layer ages sedimentation rates and mixed layer thicknesses are controlled by gradients of carbonate dissolution and fertility and by small scale redeposition processes mixed layer ages range from 3000 to 7000 years with a mode between 4000 and 5000 years sedimentation rates range from 0 8 to 2 4 cm 1000 years mixed layer depths calculated according to the box model of mixing range from 7 cm to 16 cm observed thicknesses are about one fourth smaller than calculated ones

two step deglaciation 14c dated high resolution δ18o records from the tropical atlantic ocean abstract eight box cores from the tropical atlantic were studied in detail with regard to foraminiferal oxygen isotopes radiocarbon and globorotalia menardii abundance a standard atlantic oxygen isotope signal was reconstructed for the last 20 000 yr it is quite similar to the west equatorial pacific signal published previously deglaciation is seen to occur in two steps which are separated by a pause onset of deglaciation is after 15 000 yr b p the pause is centered between 11 000 and 12 000 yr b p but may be correlative with the younger dryas 10 500 yr b p if allowance is made for a scale shift due to mixing processes on the sea floor step 2 is centered near 10 000 yr b p and is followed by a brief excursion toward light oxygen values this excursion the m event may correlate with the gulf of mexico meltwater spike

holocene upper pleistocene radiolarian biogeography and paleoecology of the equatorial pacific abstract polycystine radiolarians were investigated in 66 samples from 5 box cores spanning the last ca 40 000 years from the western approx 160 e and the central 136 w equatorial pacific the assemblages investigated show clear differences associated with the geographic locations of the sites the central pacific is characterized by higher specific diverities much higher absolute abundances of shells per gram of dry bulk sediment and by conspicuously better radiolarian preservation the differences involved also include significant changes in the relative proportions of several radiolarian species these accounting for approx 25 of total individuals families and orders these dissimilarities are chiefly attributed to differences in the primary production of the two zones and to enhanced advection of colder water species characteristics of the california current to the central equatorial pacific in both areas downcore faunal changes if present at all are so weak that background noise from random sample to sample variations almost completely masks them there do not seem to be any noticeable shifts associated with the 18 k y level inconclusive evidences of environmental changes at 30 20 k y b p are suggested in some of the cores by the increase in the proportions of several species characteristic of colder northeastern pacific waters and by lower radiolarian accumulation rates these changes seem to be paralleled by shifts in the isotopic composition of planktonic foraminifera

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

quasi analytical treatment of spatially averaged radiation transfer in complex terrain 1 we provide a new quasi analytical method to compute the subgrid topographic influences on the shortwave radiation fluxes and the effective albedo in complex terrain as required for large scale meteorological land surface or climate models we investigate radiative transfer in complex terrain via the radiosity equation on isotropic gaussian random fields under controlled approximations we derive expressions for domain averaged fluxes of direct diffuse and terrain radiation and the sky view factor domain averaged quantities can be related to a type of level crossing probability of the random field which is approximated by long standing results developed for acoustic scattering at ocean boundaries this allows us to express all nonlocal horizon effects in terms of a local terrain parameter namely the mean square slope emerging integrals are computed numerically and fit formulas are given for practical purposes as an implication of our approach we provide an expression for the effective albedo of complex terrain in terms of the sun elevation angle mean square slope the area averaged surface albedo and the ratio of atmospheric direct beam to diffuse radiation for demonstration we compute the decrease of the effective albedo relative to the area averaged albedo in switzerland for idealized snow covered and clear sky conditions at noon in winter we find an average decrease of 5 8 and spatial patterns which originate from characteristics of the underlying relief limitations and possible generalizations of the method are discussed

geology wall rock alteration and massive sulfide mineralization in a portion of the west shasta district california devonian ore deposits lens shaped bodies of massive pyrite with minor quartz chalcopyrite and sphalerite paleoenvironment of ore deposition based on 26 diamond drill holes and surface mapping indicates that sulfides accumulated in small 50 700 ft basins that were enclosed by rhyolite domes part of the hydrothermal flow system included lateral solution migration in hot water aquifers with hot spring outlets in the ore basins beneath the main ore horizon the rhyolites are pervasively altered to quartz sericite and pyrite with or without chlorite electron microprobe analyses of sphalerite and alteration chlorite sericite albite and epidote combined with thermodynamic calculations indicate that the solutions responsible for alteration and mineralization were quite enriched in mg and na relative to fe and k and had a ph in the range of 3 to 5 modified journal abstract

on the time scale of deglaciation atlantic deep sea sediments and gulf of mexico deglaciation as seen in the 18o record of deep sea sediments starts about 14 000 yrs ago measured bulk 14c ages are too old by 1000 2000 yrs in the central atlantic compared with ages derived from climate correlation this conclusion rests on the observation that deglaciation occurs in two major steps separated by a pause and on the hypothesis that this pause is correlative to the younger dryas cold period the gulf of mexico record is readily correlated with the deep sea record if it is assumed that the appearance of globorotalia menardii is retarded with respect to the tropical atlantic by about 2000 yrs the major meltwater spike then dates near 9000 yrs ago rather than at 13 500 yrs b p as assumed by kennett and shackleton 1975 or 11 500 yrs b p as in emiliani et al 1975

a reconnaissance rb sr sm nd u pb and k ar study of some host rocks and ore minerals in the west shasta cu zn district california the copley greenstone balaklala rhyolite and mule mountain stock in the west shasta cu zn district california have rb sr sm nd u pb and k ar systematics that indicate they are a cogenetic suite of ensimatic island arc rocks about 400 m y pervasive alteration and mineralization of these rocks for the most part was syngenetic and the major component of the mineralizing fluid was devonian seawater k ar ages of quartz sericite concentrates from ore horizons and rb sr systematics of a few rock and ore specimens record a later thermal and mineralizing event in the district of about 260 m y contamination of some rocks with pelagic sediments is indicated by the sm nd data

time scale of the wisconsin holocene transition oxygen isotope record in the western equatorial pacific an evaluation of both published and new oxygen isotope and radiocarbon data from the west equatorial pacific 7 box cores 2 piston cores 2 gravity cores indicates that there was no significant input of meltwater to the ocean before 14 000 14c yr b p this finding is in conflict with various early deglaciation scenarios suggested several years ago on the basis of wisconsin holocene transition records from the atlantic but agrees with late onset scenarios proposed more recently both for pacific and atlantic deglaciation records

timing of deglaciation from an oxygen isotope curve for atlantic deep sea sediments the exact timing of deglaciation is an important issue in the context of climatic feedback involving the deglacial rise in atmospheric co2 seen in ice cores1 4 we have produced evidence from box cores taken in the equatorial atlantic that the last deglaciation occurred in two major steps which were separated by a brief pause5 here we propose that this pause is equivalent to the period of glacial readvance known as younger dryas which lasted from about 11 to 10 kyr bp if our correlation is correct then the initiation of deglaciation occurred after 14 kyr bp which disagrees with most other deep sea timescales

planktonic foraminifera differential dissolution and the quaternary stable isotope record in the west equatorial pacific differential dissolution affects the isotopic composition of different species of planktonic foraminifera in different ways in the two species studied here in cores from ontong java plateau the less resistant species globigerinoides sacculifer is more readily affected at a shallower depth than the more resistant species pulleniatina obliquiloculata 2 9 versus 3 4 km but shows a smaller and less predictable response to partial dissolution 0 2 to 0 3 per mil versus 0 6 to 0 7 per mil comparison of isotopic values from the last glacial period with those from the late holocene indicates that the apparent dissolution effect is considerably reduced during the last glacial presumably due to reduced dissolution intensity during glacial time a change in the level of the lysocline of about 400 m is suggested in the published isotope records from pacific cores v28 238 and v28 239 the dissolution generated difference in 18o noted previously by shackleton and opdyke 1976 is seen to describe a mid brunhes dissolution maximum between 300 and 500 thousand years ago this mid brunhes dissolution excursion is well known from the pacific and the indian ocean

delayed postglacial uplift and synglacial sea levels in coastal central new england abstract the postglacial uplift pattern indicated by elevations of ice marginal glaciomarine deltas in coastal new england deposited between approximately 15 000 and 14 000 yr b p during ice retreat from northeastern massachusetts into southwestern maine is very similar to that previously recorded for glaciolacustrine deltas of similar age from inland areas of new england multiple regression analyses of elevations from both sets of deltas show an extremely close fit to tilted flat surfaces that rise 0 852 m km to the n 28 5 w along the coast and 0 889 m km to the n 20 5 w in western new england the close similarity of uplift pattern in areas where elevation data are from different base level media along with additional shore line evidence indicates 1 that both areas are part of the same crustal postglacial uplift block 2 that postglacial uplift was delayed until after 14 000 yr b p and 3 that little or no eustatic sea level change occurred between 15 000 and 14 000 yr b p during which time the margin of the late wisconsinan laurentide ice sheet retreated about 100 km from boston massachusetts into southwestern maine elevation data from even younger glaciomarine deltas in the coastal area indicate that soon after the ice margin reached southwestern maine and adjacent new hampshire ca 14 000 yr b p eustatic sea level rose rapidly 7 10 m during the time that the ice margin retreated 5 10 km which may have occurred during an interval of only 50 100 yr our new data not only confirm the delayed postglacial uplift model previously described for western new england but also indicate that little or no eustatic sea level change occurred during a substantial period of early deglaciation however at about 14 000 yr b p sea level rose rapidly postglacial uplift in the region apparently began between 14 000 and 13 300 yr b p before the retreating ice margin reached eastern maine

the role of ocean atmosphere reorganizations in glacial cycles abstract a case is made that glacial to interglacial transitions involve major reorganizations of the ocean atmosphere system such reorganizations constitute jumps between stable modes of operation which cause changes in the greenhouse gas content and albedo of the atmosphere only in this way can the rapidity of glacial terminations the hemispheric synchroneity and symmetry of mountain glaciation and the large polar air temperature and dustiness variations be accounted for if these reorganizations are driven in some fashion by orbitally induced seasonal insolation changes then the connection between insolation and climate is most likely through impacts of fresh water transport on the ocean s salinity distribution

stable isotopes in benthic foraminifera from ontong java plateau box cores erdc 112 and 123 abstract detailed oxygen and carbon isotope stratigraphies for two species of benthic foraminifera planulina wuellerstorfi oridorsalis umbonatus are compared between two box cores spanning the period of deglaciation and holocene within core stratigraphies are quite well correlated between core signals less so vertical mixing and possibly horizontal redeposition processes disturb the signals nevertheless there is a strong suggestion of fluctuations in the ambient bottom water conditions fo the entire time span considered

the mode and mechanism of the last deglaciation oceanic evidence changes in ocean temperature carbonate productivity and ice rafted detritus in the north atlantic suggest that half of the northern hemisphere ice volume at the last glacial maximum had disappeared by 13 000 yr b p despite the still extensive limits of the ice sheets this early thinning of the ice sheets occurred during a time when summer insolation values were slowly rising but when pollen evidence south of the ice margins indicates cold dry air masses we infer that this rapid early ice disintegration 16 000 13 000 yr b p was caused by oceanic mechanisms 1 rising sea level causing increased calving along ice margins 2 the chilling of the sea surface by icebergs and meltwater reducing moisture extraction by the atmosphere and transport to the ice sheets and 3 winter freezing of the low salinity meltwater layer suppressing local moisture extraction and the regional influx of moisture bearing storms from lower latitudes in winter and hence starving the ice sheets these oceanic feedback mechanisms were strongest from 16 000 to 13 000 yr b p and weaker but still active from that date until the end of deglaciation at 6000 yr b p

regional setting and new information on some critical geologic features of the west shasta district california the west shasta massive sulfide district is in the easternmost of a series of accreted island arc and oceanic crust terranes that comprise the klamath mountains a sequence of submarine volcanic rocks of predominantly early devonian age is the principal component of the island arc terrane in which the sulfide deposits are hosted the copley greenstone consisting mainly of andesitic and basaltic pillow lavas and breccias totaling at least 1 800 m in thickness is the oldest rock unit in the sequence it is overlain and also intruded by dikes of the balaklala rhyolite northeast of the west shasta district greenstone also overlies the balaklala rhyolite suggesting that a major greenstone unit may overlie potentially mineralized rhyolite east of the district however recent studies have shown that the complex relations in that area can be explained by folding the balaklala sequence consists of silicic flows breccias and tuffs having a maximum thickness somewhat in excess of 1 000 m the balaklala has been divided by kinkel et al 1956 into three units a lower nonporphyritic to slightly porphyritic unit containing large amounts of breccia and tuff a middle unit characterized by rhyolite containing quartz phenocrysts 1 to 4 mm in diameter but also containing a complex assortment of tuff breccia and pyritic massive sulfide bodies in its upper part and an upper unit typically containing dark quartz phenocrysts in excess of 4 mm in diameter much of the lower part of the upper unit is pyroclastic material whereas most of the upper part of the unit appears to be a massive volcanic flow rock at least half a dozen eruptive centers for the balaklala rhyolite are identified three of them within an area measuring 17 x 3 km that constitutes the limits of the former mining district the youngest unit in the arc sequence is the kennett formation consisting of black shale and chert containing radiolarians which indicate fairly deep water deposition in its lower part and limestone containing a shallow water fauna of probable middle devonian age in the upper part a 400 m y old trondhjemite stock named the mule mountain stock intrudes the copley greenstone and balaklala rhyolite and is considered to be essentially coeval with these volcanic units the pyritic massive sulfide deposits occur in clusters of individual bodies owing in large part to disruption by postmineral faults the deposits are stratigraphically confined to the upper part of the subhorizontal middle unit of the balaklala and their horizontal distribution is here interpreted to have been controlled by an extensional tectonic regime that prevailed during early devonian time the major geologic evidence for such a regime is the marked preferred elongations exhibited by the distribution of the afore mentioned eruptive centers the eight or nine massive sulfide clusters in the district and the geometrically similar distribution of the clusters in relation to each other the preferred directions of elongation in both the detailed and broader senses may be generalized to n 20 degrees to 25 degrees e n 37 degrees e n 60 degrees to 80 degrees e and n 40 degrees to 60 degrees w the three northeast trends dominate throughout the district whereas the northwest trend is evident mainly in the northern part and is more speculative the major deposit clusters fall at intersections of the major trends some of which may have been grabens trend intersections having no known deposits may be good exploration targets in localities where the stratigraphically favorable middle unit of the balaklala is still present

evidence for a bathyal front at 2000 m depth in the glacial pacific based on a depth transect on ontong java plateau data on oxygen and carbon isotope compositions of the benthic foraminifer planulina wullerstorfi from 18 cores 17 box cores and one piston core from ontong java plateau provide proxy depth profiles for temperature water mass and nutrient content for the late holocene the last transition and the last glacial the 18o profile during glacial time shows an increased gradient at a depth near 2000 m the corresponding 13c data suggest that a bathyal nutricline existed close to the same depth level the 13c values provide limits on the global change in carbon content of the glacial ocean which may be estimated as distinctly less than 1 atmospheric carbon mass 1 acm 700 gtc the greater co2 content of glacial deep waters which is reflected in the more negative 13c values may be at least in part due to a more sluggish renewal of abyssal deep waters if so the water of the deep pacific was up to 400 years older than now in turn ventilation in the upper waters above 2000 m may have been more vigorous than today

oxygen hydrogen and sulfur isotope geochemistry of a portion of the west shasta cu zn district california volcanogenic massive sulfide deposits pyrite or chalcopyrite or sphalerite in the west shasta cu zn district are hosted by the devonian balaklala rhyolite dacite and underlain by the copley greenstone basaltic andesitc the deposits occur both near to and at distance from stockwork hydrothermal vent areas whole rock delta 18 o values for greenstone and metadacite vary from 3 65 to 11 0 per mil whole rock delta d values for both rock types fall into a narrow range of values from 45 to 60 per mil which also compare well with the range for sea floor hydrothermally altered greenstones the isotopic compositions of the balaklala rhyolite and copley greenstone do not appear to vary systematically away from the mineralized part of the mining district their mineralogic as well as oxygen and hydrogen isotope compositions can largely be explained by reaction at 200 degrees to 300 degrees c with seawater which circulated through the rocks the delta 34 s values of pyrite from massive sulfide bodies and from stockwork mineralization in the central part of the mining district vary from 4 1 to 5 3 per mil three pyrite chalcopyrite mineral pairs indicate temperatures of equilibration of 340 degrees to 365 degrees c while the variation in delta 18 o values of vein quartz from the stockwork 7 8 to 11 0ppm is consistent with a temperature range for mineralization of 215 degrees to 320 degrees c reduced sulfur predominated in the hydrothermal fluid and sulfur in the ore fluid had a delta 34 s value of about 4 6 per mil sulfur in the ore fluid could have originated from either marine sulfate or magmatic sulfide under certain conditions

parameterization of the spatially averaged sky view factor in complex topography large scale meteorological land surface or climate models require precise subgrid parameterizations to reproduce unresolved subgrid processes this is particularly important in mountainous terrain where subgrid surface properties e g glacier area extent are used to illustrate the impact of global climate change the sky view factor is one of the most frequently used terrain characteristics to parameterize the influence of topography on the surface radiation balance in complex terrain a precise subgrid parameterization of sky view factors is therefore essential for accurate parameterizations of radiative fluxes such as shortwave diffuse sky and terrain reflected radiation while its computation is straightforward for a particular site a systematic characterization of the spatially averaged sky view factor is still missing we use gaussian random fields with a gaussian covariance as topography model and based on an analytical approximation we derive a parameterization for the spatially averaged sky view factor the sky view factor parameterization is solely based on computationally cheap terrain parameters namely the correlation length of subgrid topographic features and the mean squared slope in the grid cell of the large scale model for validation we compare parameterized to numerically exact sky view factors computed for real terrain of the swiss alps from a 25 m digital elevation model with subsequent averaging to varying target domain sizes we obtain a very good agreement when approaching the resolutions of regional climate models the parameterization also compares well for various real topographies from the u s

shortwave radiation parameterization scheme for subgrid topography 1 topography is well known to alter the shortwave radiation balance at the surface a detailed radiation balance is therefore required in mountainous terrain in order to maintain the computational performance of large scale models while at the same time increasing grid resolutions subgrid parameterizations are gaining more importance a complete radiation parameterization scheme for subgrid topography accounting for shading limited sky view and terrain reflections is presented each radiative flux is parameterized individually as a function of sky view factor slope and sun elevation angle and albedo we validated the parameterization with domain averaged values computed from a distributed radiation model which includes a detailed shortwave radiation balance furthermore we quantify the individual topographic impacts on the shortwave radiation balance rather than using a limited set of real topographies we used a large ensemble of simulated topographies with a wide range of typical terrain characteristics to study all topographic influences on the radiation balance to this end slopes and partial derivatives of seven real topographies from switzerland and the united states were analyzed and gaussian statistics were found to best approximate real topographies parameterized direct beam radiation presented previously compared well with modeled values over the entire range of slope angles the approximation of multiple anisotropic terrain reflections with single isotropic terrain reflections was confirmed as long as domain averaged values are considered the validation of all parameterized radiative fluxes showed that it is indeed not necessary to compute subgrid fluxes in order to account for all topographic influences in large grid sizes

glacial deep water properties in the west equatorial pacific bathyal thermocline near a depth of 2000 m abstract the stable isotope stratigraphy of planulina wullerstorfi in three box cores from ontong java plateau in the western equatorial pacific shows that there existed a bathyal thermocline near the depth of 2000 m during glacial time waters below the boundary were colder by about 1 c those above were about the same as now the deep waters were slightly enriched and the upper waters depleted in nutrients compared with present values the differences in 13 c to the present after correcting for the global change are of the order of 0 1 more positive above 2000 m and 0 1 more negative below corresponding to changes in phosphate of the order of 0 1 mol kg less phosphate above and more below the boundary

parameterizing surface wind speed over complex topography subgrid parameterizations are used in coarse scale meteorological and land surface models to account for the impact of unresolved topography on wind speed while various parameterizations have been suggested these were generally validated on a limited number of measurements in specific geographical areas we used high resolution wind fields to investigate which terrain parameters most affect near surface wind speed over complex topography under neutral conditions wind fields were simulated using the advanced regional prediction system arps on gaussian random fields as model topographies to cover a wide range of terrain characteristics we computed coarse scale wind speed i e a spatial average over the large grid cell accounting for influence of unresolved topography using a previously suggested subgrid parameterization for the sky view factor we only require correlation length of subgrid topographic features and mean square slope in the coarse grid cell computed coarse scale wind speed compared well with domain averaged arps wind speed to further statistically downscale coarse scale wind speed we use local fine scale topographic parameters namely the laplacian of terrain elevations and mean square slope both parameters showed large correlations with fine scale arps wind speed comparing downscaled numerical weather prediction wind speed with measurements from a large number of stations throughout switzerland resulted in overall improved correlations and distribution statistics since we used a large number of model topographies to derive the subgrid parameterization and the downscaling framework both are not scale dependent nor bound to a specific geographic region both can readily be implemented since they are based on easy to derive terrain parameters

relative paleointensity of the earth s magnetic field from marine sedimentary records a global perspective abstract to assess the potential of marine sediments as a source of relative paleointensity information we have undertaken an investigation of selected box cores stored in the scripps core repository we present here new results from two north atlantic box cores magnetic remanence in the sediments is carried by magnetite and is univectorial during alternating field and thermal demagnetization the median destructive field is 25 30 mt normalization by anhysteretic remanent magnetization yields relative paleointensity data that are highly concordant within and between cores age control provided by oxygen isotope data from both cores allows comparison of these relative paleointensity data with contemporaneous archeomagnetic data from czechoslavakia both data sets indicate a peak in paleofield intensity at around 8 10 ka this peak is less prominent in box core data from the western pacific and global averages of archeomagnetic and lava flow data however the peak is evident in data estimating changes in production of radiocarbon which is controlled in part by changes in the dipole moment of the geomagnetic field the excellent agreement between production variations predicted by the changes in dipole moment and those observed suggests that long term variations in atmospheric radiocarbon are dominated by geomagnetic field variations