calculation of sensible heat flux over a melting ice surface using simple climate data and daily measurements of ablation sensible heat flux is obviously important for glacier ablation but is difficult to measure routinely sensible heat flux can be estimated from wind speed and temperature data using a dimensionless heat transfer coefficient values of the heat transfer coefficient are evaluated for six sites by correlating measured melt energy with a wind temperature variable product of daily mean wind speed temperature and mean atmospheric pressure for the altitude in question data are available for short periods from two sites in arctic canada and two sites in north greenland and for hundreds of days of record at nordbogletscher and qamanarssup sermia in south and west greenland respectively average transfer coefficients for four out of the six sites are close to 0 003 which is in reasonable agreement with values reported elsewhere while larger values of 0 0047 and 0 0057 are found at the other two sites heat transfer coefficients are also estimated on a monthly basis for the two long records and substantial variations are found suggesting that the method should not be used for 20 30 days of data the present study is based on manually observed ablation and climate data but the approach could be updated to use data from automatic recording stations using modern sensors

boron isotopes and b ca in benthic foraminifera proxies for the deep ocean carbonate system abstract accurate records of the state of the ocean carbonate system are critical for understanding past changes in pco 2 ocean acidification and climate the chemical principles underlying the proxy of oceanic ph provided by the boron isotope ratio of foraminiferal carbonate are relatively well understood but the proxy s reliability has been questioned we present 76 new multi collector inductively coupled plasma mass spectrometry mc icpms 11 b measurements on a range of benthic foraminifera from 23 late holocene samples from the atlantic that reaffirm the utility of the 11 b ph proxy our boron isotope measurements on 10 benthic foraminifera tests typically yield a precision of 0 25 at 2 s d equivalent to 0 03 ph units 11 b values of epifaunal species are within analytical uncertainty of those predicted from a simple model assuming sole incorporation of b oh 4 from seawater and no vital effects using the independently determined fractionation factor of 1 0272 between 11 b 10 b of aqueous boron species infaunal foraminifera are consistent with this model but record the combined effects of lower pore water 11 b and ph no influence of partial dissolution or shell size on 11 b is observed we have also measured the b ca ratios of the same samples for individual cibicidoides species b ca shows a good correlation with co 3 2 but the b ca of different co occurring species morphotypes varies considerably these effects are not seen in 11 b which may therefore provide a more robust proxy of the ocean carbonate system whilst in theory 11 b and b ca can be combined to provide a quantitative reconstruction of alkalinity and dissolved inorganic carbonate dic in practice this is precluded by propagated uncertainties 11 b data give significant constraints on foraminifera calcification mechanisms and seem most simply explained by incorporation of b oh 4 into a hco 3 pool which is then completely incorporated in foraminiferal caco 3 our demonstration of the predictable variation of 11 b with ph across a wide range of species and locations provides confidence in the application of mc icpms measurements of foraminiferal 11 b to reconstruct past changes in the ocean carbonate system

millennial scale changes in sea surface temperature and ocean circulation in the northeast pacific 10 60 kyr bp 1 a new centennial scale mg ca temperature record from the california margin odp site 1017e reveals large millennial scale oscillations between 10 to 60 kyr this record indicates that sea surface temperature on the california margin warmed rapidly on the deglacial by 7 4 0 8 c and was preceded by a pre bolling temperature oscillation of 2 6 1 2 c millennial scale events of the last glacial episode were marked by sea surface temperature oscillations of between 3 and 7 c on the california margin and interstadials were associated with an increase in surface water salinity the data are consistent with evidence for a glacial southward shift in the polar jet stream and concomitant strengthening of the relatively cold fresh california current during stadial events the data also support previous hypotheses suggesting a tight coupling between the north atlantic and northeast pacific response to climate instability of the last glacial episode

seawater ph pco2 and co2 3 variations in the caribbean sea over the last 130 kyr a boron isotope and b ca study of planktic foraminifera abstract here a new analytical methodology is described for measuring the isotopic composition of boron in foraminifera using multicollector inductively coupled plasma mass spectrometry mc icpms this new approach is fast 10 samples analysed in duplicate per analytical session and accurate to better than 0 25 at 95 confidence with acceptable sample size requirements 1 3 mg of carbonate a core top calibration of several common planktic and two benthic species from geographically widespread localities shows a very close agreement between the isotopic composition measured by mc icpms and the isotopic composition of b oh 4 in seawater as predicted using the recently measured isotopic equilibrium factor of 1 0272 at the depth of habitat a down core and core top investigation of boron concentration b ca ratio shows that the partition coefficient is influenced by co2 3 complicating the application of this proxy nevertheless it is demonstrated that these two proxies can be used to fully constrain the carbonate system of surface water in the caribbean sea odp site 999a over the last 130 kyr this reconstruction shows that during much of the holocene and the last interglacial period surface water at site 999a was in equilibrium with the atmosphere with respect to co2 during the intervening colder periods although the surface water pco2 was lower than the holocene it was a minor to significant source of co2 to the atmosphere possibly due to either an expansion of the eastern equatorial atlantic upwelling zone or a more local expansion of coastal upwelling in the southern caribbean such reorganisation of the oceanic carbonate system in favour of a larger source of co2 to the atmosphere from the equatorial ocean may require mechanisms responsible for lowering atmospheric co2 during glacial periods to be more efficient than previously supposed

robust empirical relationships for estimating the carbonate system in the southern california current system and application to calcofi hydrographic cruise data 2005 2011 1 the california current system ccs is expected to experience the ecological impacts of ocean acidification oa earlier than most other ocean regions because coastal upwelling brings old co2 rich water relatively close to the surface ocean historical inorganic carbon measurements are scarce so the progression of oa in the ccs is unknown we used a multiple linear regression approach to generate empirical models using oxygen o2 temperature t salinity s and sigma theta as proxy variables to reconstruct ph carbonate saturation states carbonate ion concentration co32 dissolved inorganic carbon dic concentration and total alkalinity ta in the southern ccs the calibration data included high quality measurements of carbon oxygen and other hydrographic variables collected during a cruise from british columbia to baja california in may june 2007 all resulting empirical relationships were robust withr2values 0 92 and low root mean square errors estimated and measured carbon chemistry matched very well for independent data sets from the calcofi and imecocal programs reconstructed ccs ph and saturation states for 2005 2011 reveal a pronounced seasonal cycle and inter annual variability in the upper water column deeper in the water column conditions are stable throughout the annual cycle with perennially low ph and saturation states over sub decadal time scales these empirical models provide a valuable tool for reconstructing carbonate chemistry related to ocean acidification where direct observations are limited however progressive increases in anthropogenic co2 content of southern ccs water masses must be carefully addressed to apply the models over longer time scales

the effect of rock content on nutrients in a sierra nevada forest soil abstract the effects of rock content on nutrient concentrations and contents kg ha 1 in a skeletal soil derived from andesite were investigated rock content to a 60 cm depth ranged from 8 to 69 among 20 quantitative soil pits within a 10 ha area on average rocks contained 9 of total soil c 19 of total soil n 3 of total ecosystem c and 12 of total ecosystem n percent rock content also appeared to cause increases in organic matter concentrations rock content was significantly positively correlated with total c and total n concentrations in the fine earth 2 mm fraction soil c was organic no carbonates were present percent rock content was also significantly positively correlated with fine earth c n ratio suggesting that organic matter in rockier soils was in an earlier stage of decomposition at any given depth other consistent correlations with rock content included bray p positive and exchangeable mg 2 negative the decrease in fine earth mass with increasing percent rock content offsets the increase in c concentration such that there was no correlation between percent rock content and either fine earth or total soil fine earth plus rock c content kg ha 1 percent rock content was significantly negatively correlated with total n bray p inorganic n exchangeable k ca 2 and mg 2 contents however the results of this study show that high rock content can affect soil c and nutrient pools not only because of the contributions of the rocks themselves but also because high rock content appears to cause higher concentrations in the fine earth fraction

size distribution of holocene planktic foraminifer assemblages biogeography ecology and adaptation the size of any organism is influenced by the surrounding ecological conditions in this study we investigate the effects of such factors on the size spectra of planktic foraminiferal assemblages from holocene surface sediments we analyzed assemblages from 69 holocene samples which cover the major physical and chemical gradients of the oceans on a global scale the range of sizes in assemblages triples from the poles to the tropics this general temperature related size increase is interrupted by smaller sizes at temperatures characteristic of the polar and subtropical fronts at 2 c and 17 c respectively as well as in upwelling areas on a regional scale surface water stratification seasonality and primary productivity are highly correlated with the size patterns such environmentally controlled size changes are not only characteristic for entire assemblage but also for the dominant single species

planktonic foraminiferal area density as a proxy for carbonate ion concentration a calibration study using the cariaco basin ocean time series 1 biweekly sediment trap samples and concurrent hydrographic measurements collected between march 2005 and october 2008 from the cariaco basin venezuela are used to assess the relationship between co32 and the area densities a of two species of planktonic foraminifera globigerinoides ruber pink and globigerinoides sacculifer calcification temperatures were calculated for each sample using species appropriate oxygen isotope 18o temperature equations that were then compared to monthly temperature profiles taken at the study site in order to determine calcification depth ambient co32 was determined for these calcification depths using alkalinity ph temperature salinity and nutrient concentration measurements taken during monthly hydrographic cruises the a which is representative of calcification efficiency is determined by dividing individual foraminiferal shell weights 0 43 g by their associated silhouette areas and taking the sample average the results of this study show a strong correlation between a and ambient co32 for both g ruber and g sacculifer r2 0 89 and 0 86 respectively confirming that co32 has a pronounced effect on the calcification of these species though the a for both species reveal a highly significant p 0 001 relationship with ambient co32 linear regression reveals that the extent to which co32 influences foraminiferal calcification is species specific hierarchical regression analyses indicate that other environmental parameters temperature and po43 do not confound the use of g ruber and g sacculifer a as a predictor for co32 this study suggests that g ruber and g sacculifer a can be used as reliable proxies for past surface ocean co32

sea level rise a review of recent past and near future trends global mean sea level is a potentially sensitive indicator of climate change global warming will contribute to worldwide sea level rise slr from thermal expansion of ocean water melting of mountain glaciers and polar ice sheets a number of studies mostly using tide gauge data from the permanent service for mean sea level bidston observatory england have obtained rates of global slr within the last 100 years that range between 0 3 and 3 mm yr 1 with most values concentrated between 1 and 2 mm yr 1 however the reliability of these results has been questioned because of problems with data quality and physical processes that introduce a high level of spatial and temporal variability sources of uncertainty in the sea level data include variations in winds ocean currents river runoff vertical earth movements and geographically uneven distribution of long term records crustal motions introduce a major source of error to a large extent these can be filtered by employing palaeo sea level proxies and geophysical modelling to remove glacio isostatic changes ultimately satellite geodesy will help resolve the inherent ambiguity between the land and ocean level changes recorded by tide gauges future sea level is expected to rise by 1 m with a best guess value of 48 cm by the year 2100 such rates represent an acceleration of four to seven times over present rates local land subsidence could substantially increase the apparent slr for example louisiana is currently experiencing slr trends nearly 10 times the global mean rate these recently reduced slr estimates are based on climate models that predict a zero to negative contribution to slr from antarctica most global climate models gcms indicate an ice accumulation over antarctica because in a warmer world precipitation will exceed ablation snow melt however the impacts of attritional processes such as thinning of the ice shelves have been downplayed according to some experts furthermore not all climate models are in agreement opposite conclusions may be drawn from the results of other gcms in addition the west antarctic ice sheet is potentially subject to dynamic and volcanic instabilities that are difficult to predict because of the great uncertainty in slr projections careful monitoring of future sea level trends by upgraded tide gauge networks and satellite geodesy will become essential finally because of the high spatial variability in crustal subsidence rates wave climates and tidal regimes it will be the set of local conditions especially the relative sea level rise rather than a single global mean sea level trend that will determine each locality s vulnerability to future slr

reevaluation of the oxygen isotopic composition of planktonic foraminifera experimental results and revised paleotemperature equations cultured planktonic foraminifera orbulina universa symbiotic and globigerina bulloides nonsymbiotic are used to reexamine temperature 18o relationships at 15 25 c relationships for both species can be described by linear equations equations for o universa grown under low light ll and high light hl share a slope of 4 80 0 21 c 1 with a hl ll offset of 0 33 due to symbiont photosynthetic activity the effect of co32 on o universa is 0 002 mol 1 kg 1 and is insensitive to temperature for g bulloides ontogenetic effects produce size related trends in temperature 18o whereby larger shells are enriched in 18o relative to smaller specimens the o universa temperature 18o relationships are more accurate than previously published equations for describing plankton tow data our equations do not explain planktonic core top data with the same precision but provide a good fit to benthic cibicidoides data below 10 c temperature 18o relationships for g bulloides provide good agreement with field data for this species from the northeast pacific

planktic foraminiferal sedimentation and the marine calcite budget 1 the vertical flux and sedimentation rate of planktic foraminiferal tests are quantified and a global planktic foraminiferal cac0 3 budget is presented test and calcite flux rates are calculated according to the distribution of species obtained from multinet and sediment trap samples modern planktic foraminiferal population dynamics are discussed as a prerequisite for the quantification of the calcite budget highlighting the importance of ecological autecological e g reproduction and biogeochemical conditions that determine the presence or absence of species to complete the open marine particulate caco 3 inventory the contribution of coccolithophores pteropods and calcareous dinophytes is discussed based on the studied regions the global planktic foraminiferal calcite flux rate at 100 m depth amounts to 1 3 3 2 gt yr 1 equivalent to 23 56 of the total open marine caco 3 flux the preservation of tests varies on a regional and temporal scale and is affected by local hydrography and dissolution during most of the year off peak periods many tests dissolve above 700 m water depth while settling through the water column with on average only 1 3 of the initially exported caco 3 reaching the deep seafloor pulsed flux events mass dumps of fast settling particles yield a major contribution of tests to the formation of deep sea sediments on average 25 of the initially produced planktic foraminiferal test cac0 3 settles on the seafloor the total planktic foraminiferal contribution of caco 3 to global surface sediments amounts to 0 36 0 88 gt yr 1 32 80 of the total deep marine calcite budget

oceanic ph control on the boron isotopic composition of foraminifera evidence from culture experiments culture experiments were carried out with the species orbulina universa at four different ph values 7 70 0 05 8 15 0 05 8 60 0 05 and 9 00 0 10 in order to establish the ph dependence of boron isotope fractionation between seawater and foraminifera a clear relationship between the boron isotopic composition of the foraminifera and the ph of the seawater culture solutions was found showing heavier boron isotopic composition at higher ph this finding supports the viability of boron isotopes as a paleo ph tool it is important to note that orbulina universa cultured in natural seawater as well as those obtained from coretop samples have a significantly lighter boron isotopic ratio than globigerinoides sacculifer from coretop samples suggesting that at least for this species a vital effect is active

latest quaternary north pacific surface water responses imply atmosphere driven climate instability a full sequence of brief interstadials dansgaard oeschger d o cycles are recorded from 60 to 25 ka in santa barbara basin california ocean drilling program hole 893a by planktonic foraminiferal isotopic and assemblage changes at unparalleled high resolution for the oceans synchronous climatic response between north pacific surface waters and the greenland ice sheet during d o cycling is strongly indicated by remarkable similarities in speed magnitude and character of rapid oceanic and atmospheric reorganizations inferred sea surface temperature warmings of as much as 5 c within a few decades and brief warming overshoots of as much as 3 c suggest involvement of an atmospheric amplification top down in situ atmospheric warming of the ocean is implied by differential responses partial decoupling in the changes recorded in surface and thermoclinal waters

stable oxygen isotope composition is biased by shell calcification intensity in planktonic foraminifera planktonic foraminifera are widely used for environmental reconstructions through measurements of their shell s geochemical characteristics including its stable oxygen and carbon isotope composition using these parameters as unbiased proxies requires a firm knowledge of all potential confounding factors influencing foraminiferal shell geochemistry one such parameter is the shell calcification intensity shell weight normalized for shell size that may influence the shell delta 18o value either bioenergetically by reducing energy available and required for equilibrium isotope fractionation during faster calcification or kinetically by influencing calcification depth through the shell s density contrast with seawater specimens from the globigerinoides ruber elongatus compound from a sediment trap in the north atlantic have been used to quantify the influence of shell calcification intensity on shell delta 18o values shell calcification intensity was found to have a significant effect on the shell stable oxygen isotope composition in all species through model fitting it is suggested that the effect size may be in a range of 1 to 2 depending on species depth migration and local oceanographic conditions we show that the confounding effect of shell calcification intensity on stable oxygen isotope composition can be of importance depending on the anticipated precision of the derived reconstructions a framework is provided to quantify this effect in future studies

seasonal variability in the δ18o and δ13c of planktonic foraminifera from an upwelling environment sediment trap results from the san pedro basin southern california bight stable isotopic analyses 18o and 13crpar on four species of planktonic foraminifera collected from high resolution time series sediment trap sampling indicate that rapid and significant seasonal variability occurred in response to rapid changes in both the hydrographic environment and the isotopic composition of ambient seawater specimens were collected at a depth of 500 m for 28 consecutive 1 week periods in the san pedro basin within the southern california bight a region seasonally influenced by upwelling hydrographic monitoring of the study area revealed a 6 week period late april to mid june during which pulses of upwelling occurred causing significant increases in the oxygen isotopic composition of surrounding waters while decreasing the carbon isotopic composition analyses of globigerina bulloides orbulina universa neogloboquadrina dutertrei and neogloboquadrina pachyderma right coiling indicate that during the upwelling period these species live respectively at the surface in the surface mixed layer within the thermocline and below the thermocline globigerina bulloides ascends from well below the thermocline to the surface at the onset of upwelling and increases production to its maximum simultaneously as its morphology changes to less calcified open forms both n dutertrei and n pachyderma follow isothermal ranges migrating to shallower waters during upwelling and subsequently descending after upwelling ceases neogloboquadrina dutertrei appears to inhabit the region associated with both the thermocline base and chlorophyll maximum when it is most abundant following upwelling orbulina universa increases its depth habitat as solar irradiance increases but this species decreases in abundance during upwelling the 18o signal of o universa appears to be a useful indicator of seasonal temperature variations above the thermocline whereas the 18o of g bulloides documents near surface temperatures during upwelling the 13c signal of both n dutertrei and n pachyderma appears to record the 13c of equilibrium calcite for the regions of the thermocline and just below the thermocline respectively due to the relative preservation potentials of the four species analyzed only n dutertrei and n pachyderma are likely to be preserved in the sedimentary record in regions of oxygenated bottom waters thus an actual record of hydrographic conditions during upwelling as would be found in tests of g bulloides is not preserved instead conditions before n pachyderma and just after n dutertrei are more likely recorded

rock fragments evolution and nutrients release in vineyard soils developed on a thinly layered limestone tuscany italy abstract this work dealt with two groups of vineyard soils developed from a thinly layered limestone in central italy so as to evaluate the evolution of the rock fragments and their capability to release nutrients one group consisted of five soils at 1 2 years after plantation of vines renewed soils while the other group was represented by five soils at 20 29 years from plantation aged soils soils were sampled by horizons on a volume basis fine earth rock fragments classed according to the degree of alteration and fresh rock were analyzed for mineralogy porosity ph total nh 4 n and extractable ca mg and k results indicated that the rock fragments of the aged soils were less and appeared more altered than those of the renewed soils this fact was ascribed to weathering processes that progressively transformed rock fragments into fine earth weathering of rock fragments was promoted by the calcite dissolution and the mechanical works made to break up the soil and for routine soil management because of this rock fragments increased porosity and exposed new mineral surfaces to soil solution with consequent reduction of their size and increasing of their friability and release of nh 4 n ca mg and k

modelling albedo and specific balance of the greenland ice sheet calculations for the sondre stromfjord transect glacio meteorological data obtained during the greenland ice margin experiment gimex investigations in west greenland the sondre stromfjord transect have been used to test and calibrate four energy balance mass balance models for the ice snow surface the region is characterised by the development of a wide zone of low surface albedo in the course of the melting season this zone was simulated in one of the energy balance models by including the effect of surficial meltwater on albedo observed mass balance and albedo data were used to constrain the models although all the models are capable of predicting the transect balance reasonably well only the model with the meltwater albedo coupling is able to reproduce the observed albedo pattern and mass balance profile along the transect by including the feedback between surficial meltwater and albedo in the model the sensitivity of the specific balance to changes in air temperature is found to be greatest just below the equilibrium line in contrast to what is generally found for valley glaciers a 1 k warming of the air temperature would increase the mean ablation along the transect by 0 5 m w e year 1

controls on boron incorporation in cultured tests of the planktic foraminifer orbulina universa culture experiments with living planktic foraminifers reveal that the ratio of boron to calcium b ca in orbulina universa increases from 56 to 92 mol mol 1 when ph is raised from 7 61 0 02 to 8 67 0 03 total scale across this ph range the abundances of carbonate bicarbonate and borate ions also change 530 500 and 170 mol kg 1 respectively thus specific carbonate system control s on b ca remain unclear complicating interpretation of paleorecords b ca in cultured o universa also increases with salinity 55 72 mol mol 1 from 29 9 35 4 and seawater boron concentration 62 899 mol mol 1 from 4 40 ppm b suggesting that these parameters may need to be taken into account for paleorecords spanning large salinity changes 2 and for samples grown in seawater whose boron concentration b sw differs from modern by more than 0 25 ppm while our results are consistent with the predominant incorporation of the charged borate species boh4 into foraminiferal calcite the behavior of the partition coefficient kd defined as b ca calcite boh4 hco3 seawater cannot be explained by borate incorporation alone and suggests the involvement of other ph sensitive ions such as co32 for a given increase in seawater boh4 the corresponding increase in b ca is stronger when boh4 is raised by increasing b sw than when it is raised by increasing ph these results suggest that b incorporation controls should be reconsidered additional insight is gained from laser ablation icp ms profiles which reveal variable b ca distributions within individual shells

core top calibration of b ca in pacific ocean neogloboquadrina incompta and globigerina bulloides as a surface water carbonate system proxy abstract practical methods for reconstructing past ocean carbonate chemistry are needed to study past periods of ocean acidification and improve understanding of the marine carbonate system s role in the global climate cycles planktic foraminiferal b ca may fill this role but requires better understanding and improved proxy calibrations we used pacific ocean core top sediments to generate new calibrations of the b ca proxy for past carbonate system parameters in two upwelling subpolar species of asymbiotic planktic foraminifera globigerina bulloides and neogloboquadrina incompta both species show significant positive correlation of b ca with calcite saturation calcite and carbonate ion concentration co 3 2 across a broad range of environmental conditions this suggests a calcification rate control on b ca incorporation as calcite regulates calcification rate in agreement with recent inorganic calcite studies this is also consistent with a surface entrapment model of trace element incorporation into caco3 in neither species is b ca significantly correlated with ph suggesting that ph does not directly regulate boron incorporation and that calculation of ph directly from foraminiferal b ca is not suitable correlations between b ca and b oh 4 b oh 4 hco3 and b oh 4 dic are weaker than with calcite boron partition coefficients k d b ca solid b oh 4 hco 3 seawater show little or no correlation with co32 or temperature and vary widely providing no support for application of kd to calculate carbonate system parameters from b ca we also discuss potential effects of depth related dissolution temperature and salinity on b ca these empirical calibrations linking foraminiferal calcite b ca with calcite provide a strong tool for reconstructing the past ocean carbonate system and improve our understanding of the proxy s geochemical basis

characteristics of the heat balance of the greenland ice sheet for modelling les donnees du bilan thermique recoltees au cours de l egig de 1959 a 1967 sont appliquees au calcul du deplacement de la ligne d equilibre du au changement climatique

the universal ratio of boron to chlorinity for the north pacific and north atlantic oceans abstract we report seawater boron concentration mg kg 1 and chlorinity values measured in seawater samples n 139 collected at various depths in the north pacific and north atlantic oceans and the east japan sea located in the western temperate north pacific our results indicate that variations in seawater boron concentration are strongly coupled to variations in chlorinity and salinity yielding a mean boron to chlorinity ratio of 0 2414 0 0009 mg kg 1 1 boron to salinity ratio 0 1336 0 0005 mg kg 1 1 this ratio was surprisingly universal throughout the water column in the three marine basins and across widely different ocean surface regimes but differs from the generally accepted ratio of 0 232 0 005 mg kg 1 1 determined by uppstrom 1974 which was based on only 20 measurements at four sites in the tropical pacific ocean in converting total alkalinity to carbonate alkalinity and vice versa for thermodynamic calculations the difference between these two ratios leads to a difference of 5 mol kg 1 in estimates for ocean surface waters where the contribution of borate to total alkalinity is typically greatest we suggest the use of the new boron to chlorinity ratio for predicting seawater boron concentrations using chlorinity or salinity data

a dramatic atlantic dissolution event at the onset of the last glaciation 1 measurements of the caco3 content of the caco3 size index and of foraminifera weights demonstrate that a prominent dissolution event occurred in the western equatorial atlantic at the onset of the last glacial period the decrease in co3 ion concentration appears to have been too large to be accounted for by the ocean acidification associated with the demise of excess interglacial biomass rather it appears to have been the result of a temporary strengthening of the penetration of the glacial equivalent antarctic bottom water into the atlantic the co occurrence of massive ethmodiscus rex deposition in the eastern equatorial atlantic bears witness to a reorganization of circulation in the atlantic this reorganization may well reflect a temporary collapse of conveyor circulation at the onset of the last glaciation

surface roughness and bulk heat transfer on a glacier comparison with eddy correlation more than 100 simultaneously measured profiles of wind speed and temperature were analyzed to determine the aerodynamic and thermal roughness lengths of glacier ice the results proved to be extremely sensitive to measurement height which is difficult to define precisely on the hummocky terrain of a glacier therefore aerodynamic roughness lengths were estimated from the microtopography of the surface yielding 2 46 mm for ice and 5 5 mm for snow despite the indeterminate nature of the profile analysis it did support the view that the thermal roughness length must decrease as the roughness reynolds number increases a relationship which has been modelled in the literature good agreement between bulk transfer estimates and eddy correlation measurements of fhe sensible heat flux density on melting ice and snow was obtained by combining the aerodynamic roughness length with a suitable model for thermal roughness length

implications of increased greenland surface melt under global warming scenarios ice sheet simulations abstract the greenland ice sheet is likely to make a faster contribution to sea level rise in a warming world than previously believed based on numerical modelling using a parameterization of recent results showing surface meltwater lubrication of ice flow zwally et al science 297 557 2002 218 documented correlation between increased ice velocity and increased surface melt as parameterized by positive degree days they argued that surface water is piped directly to the bed with little delay causing increased basal water pressures and basal sliding velocities an effect not included in recent greenland ice sheet models known to the authors using the pennsylvania state university university of chicago thermomechanical flowline model numerous simulations were conducted to test a wide range of parameter space linking surface melt with a new sliding law based on the zwally et al data under three different global warming scenarios 2 co2 4 co2 and 8 co2 comparisons to reconstructions generated with a traditional sliding parameterization illustrate an enhanced sensitivity of the ice sheet to surface warming resulting in higher ablation rates additional thinning and retreat of the margin and a reduction in ice volume leading to an increased contribution to global sea level rise

melting of ice shelves and the mass balance of antarctica we calculate the present ice budget for antarctica from measurements of accumulation minus iceberg calving run off and in situ melting beneath the floating ice shelves the resulting negative mass balance of 469 gt year 1 differs substantially from other recent estimates but some components are subject to high temporal variability and budget uncertainties of 20 50 annual accumulation from an earlier review is adjusted to include the antarctic peninsula for a total of 2144 gt year 1 an iceberg production rate of 2016 gt year 1 is obtained from the volume of large icebergs calculated from satellite images since 1978 and from the results of an international iceberg census project ice shelf melting of 544 gt year 1 is derived from physical and geochemical observations of meltwater outflow glaciological field studies and modeling of the sub ice ocean circulation the highest melt rates occur near ice fronts and deep within sub ice cavities run off from the ice sheet surface and from beneath the grounded ice is taken to be 53 gt year 1 less than half of the negative mass balance need come from the grounded ice to account for the unattributed 0 45 mm year 1 in the ipcc best estimate of the recent global sea level rise

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

rock fragments in top soils significance and processes this introductory paper reviews various aspects of rock fragments in top soils such information is required for various reasons and in particular for predicting the impact of climatic or landuse changes on the response of these soils particular attention is paid to the definition and measurement of rock fragment content in top soils the density of soils containing rock fragments the spatial distribution and movement of rock fragments in top soils the effects of rock fragments on some key hydrological processes thermal properties of top soils physical soil degradation soil erosion and soil productivity

biogeochemical anomalies at two southern california current system moorings during the 2014 2016 warm anomaly el nino sequence author s lilly le send u lankhorst m martz tr feely ra sutton aj ohman md abstract 2019 american geophysical union all rights reserved we analyzed impacts of the 2014 2015 pacific warm anomaly and 2015 2016 el nino on physical and biogeochemical variables at two southern california current system moorings cce2 nearshore upwelling off point conception cce1 offshore california current nitrate and chl a fluorescence were l1 m and l1 standardized fluorescence unit respectively at cce2 for the entire durations of the warm anomaly and el nino the two longest periods of such low values in our time series negative nitrate and chl a anomalies at cce2 were interrupted briefly by upwelling conditions in spring 2015 near surface temperature anomalies appeared simultaneously at both moorings in spring 2014 indicating region wide onset of warm anomaly temperatures although sustained negative nitrate and chl a anomalies only occurred offshore at cce1 during el nino summer 2015 to spring 2016 warm anomaly temperature changes were expressed more strongly in near surface l40 m than subsurface 75 m waters at both moorings while el nino produced comparable temperature anomalies at near surface and subsurface depths nearshore aragonite at 76 m showed notably fewer undersaturation events during both warm periods suggesting an environment more conducive to calcifying organisms planktonic calcifying molluscs pteropods and heteropods increased markedly in springs 2014 and 2016 and remained modestly elevated in spring 2015 moorings provide high frequency measurements essential for resolving the onset timing of anomalous conditions and frequency and duration of short term days to weeks perturbations reduced nitrate and aragonite undersaturation events that can affect marine organisms

seasonal and interannual variation in santa barbara basin water temperatures observed in sediment trap foraminiferal mg ca 1 we have generated a santa barbara basin sediment trap mg ca record to evaluate culture based calibration equations for the temperate subpolar planktonic foraminiferal species globigerina bulloides and neogloboquadrina pachyderma dextral g bulloides and n pachyderma mg ca are significantly correlated with seasonal variations in temperature of the near surface and subthermocline depths respectively the average deviation between mg based and 18o based temperature estimates is 0 6 c for g bulloides and 0 8 c for n pachyderma differences between mg derived temperatures and instrumental temperatures may be due to cleaning methods environmental factors such as seasonal variations in foraminiferal depth habitats or possible secondary effects on mg ca core top mg ca of both g bulloides and n pachyderma is in excellent agreement with average values from the sediment trap lending strong support for the interpretation of downcore mg ca from these species as annual average near surface and thermoclinal temperatures

a simple energy balance model to calculate ice ablation at the margin of the greenland ice sheet apres avoir etabli les relations donnees climatiques taux d enlevement de la glace dans 2 glaciers du groenland un modele simple de bilan energetique est effectue pour calculer le taux d enlevement de la glace aux bordures du glacier

increased northeast pacific climatic variability during the warm middle holocene 1 we use a pair of decadally resolved planktonic foraminiferal 18o records from santa barbara basin sbb to show that the warmest interval of the current interglacial the middle holocene was characterized by increased decadal to centennial scale climatic variability modern relationships between the pacific decadal oscillation pdo the el nino southern oscillation enso and upper water conditions in sbb also suggest a preference of the northeast ne pacific climate during the warm mid holocene toward the warm phase of the pdo and more intense enso warm events el ninos in the context of future climate this study suggests increasing decadal to centennial scale climatic variability in a globally warmed world

direct assessment of stable isotope variability in planktonic foraminifera populations abstract a large number of tests of three species of planktonic foraminifera globigerinoides sacculifer orbulina universa and pulleniatina obliquiloculata were analyzed for stable oxygen and carbon isotopes in a western equatorial pacific box core estimates of population variance were calculated using a statistical technique known as the jackknife these estimates were used to generate sampling curves which provide the number of foraminiferal tests required in an isotopic analysis when precision and reliability criteria are specified the jackknife results have important sampling implications 1 a large number of foraminiferal tests are required to obtain statistically reliable isotope data for example given a machine precision standard deviation of 0 09in0 417 tests g sacculifer 355 420 m are required to obtain a 18 o precision of 0 1in0 with 90 reliability 2 variance is a function of test diameter with greater variance being found in larger size fractions 3 variance is dependent on foraminiferal species 4 variance differences between glacial and interglacial samples are not significant 5 in the size interval 600 900 m a systematic relationship is not seen between size and 18 o or 13 c 6 replicate analysis is a practical method of improving isotope data quality size and species related variance differences are probably related to a number of factors including depth habitat seasonal production of tests species vertical migrations and vital and or symbiosis caused effects knowledge of data variance permits error assessment in sediment unmixing analyses and optimization of spectral estimates

the abrupt termination of the younger dryas climate event previous studies on two deep greenland ice cores have shown that a long series of climate oscillations characterized the late weichselian glaciation in the north atlantic region1 and that the last glacial cold period the younger dryas ended abruptly 10 700 years ago2 here we further focus on this epoch defining event and present detailed heavy isotope and dust concentration profiles which suggest that in less than 20 years the climate in the north atlantic region turned into a milder and less stormy regime as a consequence of a rapid retreat of the sea ice cover a warming of 7 c in south greenland was completed in about 50 years

surface melt induced acceleration of greenland ice sheet flow ice flow at a location in the equilibrium zone of the west central greenland ice sheet accelerates above the midwinter average rate during periods of summer melting the near coincidence of the ice acceleration with the duration of surface melting followed by deceleration after the melting ceases indicates that glacial sliding is enhanced by rapid migration of surface meltwater to the ice bedrock interface interannual variations in the ice acceleration are correlated with variations in the intensity of the surface melting with larger increases accompanying higher amounts of summer melting the indicated coupling between surface melting and ice sheet flow provides a mechanism for rapid large scale dynamic responses of ice sheets to climate warming

elevation change of the greenland ice sheet and its measurement with satellite radar altimetry satellite radar altimetry is presently the only method that has provided the spatial coverage and density of observations needed to reduce the present uncertainty in the mass balance of the greenland ice sheet and its contribution to change in eustatic sea level the only such measurement reported however estimated that southern greenland was thickening at 23 6 cm a 1 which is larger than was thought hitherto this value is reconsidered given more recent information concerning the errors in the measurement a survey of measurements of specific mass balance of the greenland ice sheet is given together with estimates of its sensitivity to temperature change the expected behaviour is described of errors in the satellite position and errors in the range measurement to the ice sheet surface the treatment of biases and the number of independent observations of random errors is described it is found in particular that a higher degree of independence was given to the random errors than should have been the case the total error is recalculated with this accounted for and is found to remain dominated by the bias estimate and therefore largely unaffected by this change the estimate is 23 7 cm a 1 it is concluded that the observation does support a recent thickening of the southern greenland ice sheet

testing planktic foraminiferal shell weight as a surface water co32 proxy using plankton net samples planktic foraminiferal size normalized weight snw has been used as a proxy for both past changes in deepwater dissolution and surface ocean co32 the latter potentially providing a way to evaluate paleoatmospheric p co2 variations beyond the ice core records here we examine the relationship between snw in modern planktic foraminifera and surface water co32 in the arabian sea using a suite of samples obtained from plankton net casts in surface waters having a large range in their carbon chemistry our results reveal substantial interspecies and intraspecies specific variations in the strength gradient and even sign of this relationship indicating that co32 does not exert a dominant control on foraminiferal test weight similarly foraminiferal abundance data do not lend support to the hypothesis that snw responds to optimal growth conditions further work is needed perhaps in laboratory cultures to determine those environmental factors that are simply correlated with snw and those that exert control

dansgaard oeschger cycles and the california current system planktonic foraminiferal response to rapid climate change in santa barbara basin ocean drilling program hole 893a high resolution planktonic foraminiferal census data from santa barbara basin ocean drilling program hole 893a demonstrate major assemblage switches between 25 and 60 ka that were associated with dansgaard oeschger cycles stadials dominated by neogloboquadrina pachyderma sinistral and globigerinoides glutinata suggest a strong subpolar california current influence while interstadials marked by abundant n pachyderma dextral and g bulloides indicate a relative increase in subtropical countercurrent influence modern analog technique and transfer function f 20rsc temperature reconstructions support 18o evidence of large rapid 70 years or less sea surface temperature shifts 3 to 5 c between stadials and interstadials changes in the vertical temperature gradient and water column structure thermocline depth are recorded by planktonic faunal oscillations suggest bimodal stability in the organization of north pacific surface ocean circulation santa barbara basin surface water demonstrates the rapid response of the california current system to reorganization of north pacific atmospheric circulation during rapid climate change supporting assemblage data are available on diskette or via anonymous ftp from kosmos agu org directory apend username anonymous password guest diskette may be ordered from american geophysical union 2000 florida avenue n w washington dc 20009 or by phone at 800 966 2481 5 00 payment must accompany order

calibration of the boron isotope proxy in the planktonic foraminifera globigerinoides ruber for use in palaeo co2 reconstruction abstract the boron isotope ph proxy applied to mixed layer planktic foraminifera has great potential for estimating past co2 levels which in turn is crucial to advance our understanding of how this greenhouse gas influences earth s climate previous culture experiments have shown that although the boron isotopic compositions of various planktic foraminifera are ph dependent they do not agree with the aqueous geochemical basis of the proxy here we outline the results of culture experiments on globigerinoides ruber white across a range of ph 7 5 8 2 and analysed via multicollector inductively coupled plasma mass spectrometry mc icpms and compare these data to core top and sediment trap samples to derive a robust new species specific boron isotope ph calibration consistent with earlier culture studies we show a reduced ph dependency of the boron isotopic composition of symbiont bearing planktonic foraminifera compared to borate ion in seawater we also present evidence for a size fraction effect in the 11b of g ruber finally we reconstruct atmospheric co2 concentrations over the last deglacial using our new calibration at two equatorial sites odp site 999a and site geob1523 1 these data provide further grounding for the application of the boron isotope ph proxy in reconstructions of past atmospheric co2 levels

lateral controls on grounding line dynamics we present a theoretical and experimental study of viscous gravity currents introducedat the surface of a denser inviscid uid layer of nite depth inside a vertical hele shaw cell initially the viscous uid oats on the inviscid uid forming a self similar buoyancy driven current resisted predominantly by the viscous stresses due to shearacross the width of the cell once the viscous current contacts the base of the cell the ow can be considered in two regions a grounded region in which the currentlies in full contact with the base and a oating region the subsequent advance ofthe grounding line separating these regions is shown to be controlled by the thickeningof the current associated with balancing the local shear stresses an understanding ofthe ow transitions is developed using asymptotic and numerical analysis of a modelbased on lubrication theory key words geophysical and geological ows hele shaw ows ice sheets

the effect of rock fragments on wheat biomass production under highly variable moisture conditions in mediterranean environments abstract the effects of soil properties that affect water availabilty to plants such as soil depth rock fragments parent material and degree of erosion on biomass production of rainfed wheat were studied on hilly soils under different weather conditions total above ground biomass production tagbp of wheat was measured along catenas of marl and shale sandstone formations in two successive growing periods during the first growing period which was extremely dry total amount of rainfall r 95 mm versus 370 mm in an average year the soils on marl free of rock fragments produced an average tagbp of 1100 kg ha 1 despite their great soil depth whereas on shoulders and footslopes of the stony soils on shale sandstone formations tagbp values of 4620 and 11 100 kg ha 1 were measured respectively the opposite occurred the following growing period which was exceptionally wet r 663 mm soils on marls were more productive due to the higher fertility status than the soils on shale sandstone formations rock fragments more responsible for the lower exploitable soil volume and the generally lower biomass production under wet climatic conditions play an important role on soil water conservation under dry climatic conditions

b ca in planktonic foraminifera as a proxy for surface seawater ph boron isotope systematics indicate that boron incorporation into foraminiferal caco3 is determined by the partition coefficient k d frac left rm b rm ca right rm caco3 left rm b left rm oh right 4 rm hco 3 right rm seawater and b oh 4 hco3 seawater providing in principle a method to estimate seawater ph and pco2 we have measured b ca ratios in globigerina bulloides and globorotalia inflata for a series of core tops from the north atlantic and the southern ocean and in globigerinoides ruber white from ocean drilling program odp site 668b on the sierra leone rise in the eastern equatorial atlantic b ca ratios in these species of planktonic foraminifera seem unaffected by dissolution on the seafloor k d shows a strong species specific dependence on calcification temperature which can be corrected for using the mg ca temperature proxy a preliminary study of g inflata from southern ocean sediment core chat 16k suggests that temperature corrected b ca was 30 higher during the last glacial correspondingly ph was 0 15 units higher and aqueous pco2 was 95 atm lower at this site at the last glacial maximum the covariation between reconstructed pco2 and the atmospheric pco2 from the vostok ice core demonstrates the feasibility of using b ca in planktonic foraminifera for reconstructing past variations in ph and pco2

degree day glacier mass balance modelling with applications to glaciers in iceland norway and greenland a degree day glacier mass balance model is applied to three glaciers in iceland norway and greenland for which detailed mass balance measurements are available over a period of several years model results are in good agreement with measured variations in the mass balance with elevation over the time periods considered for each glacier in addition the model explains 60 80 of the year to year variance in the elevation averaged summer season mass balance measurements on the glaciers using a single parameter set for each glacier the increase in ablation on the glaciers due to a warming of 2 c is predicted to range from about 1 m w e year 1 at the highest elevations to about 2 5 m w e year 1 at the lowest elevations predicted changes in the winter balance measured between fixed date are relatively small except at the lowest elevations on the icelandic and norwegian glaciers where the winter balance is significantly reduced equilibrium line altitudes are raised by 200 300 m on the icelandic and norwegian glaciers except at the highest elevations the winter balance of the icelandic and norwegian glaciers is predicted to decrease even if the warming is accompanied by a 10 increase in the precipitation no firm evidence of a climate related variation in the degree day factors or in the temperature lapse rate on the same glacier could be found the model furthermore reproduces large variations in the mass balance with elevation and from year to year on each glacier using the same parameter set we assume therefore that these parameters will not change significantly for the climate scenarios considered here

using species specific paleotemperature equations with foraminifera a case study in the southern california bight abstract species specific paleotemperature equations were used to reconstruct a record of temperature from foraminiferal 18 o values over the last 25 kyr in the southern california bight the equations yield similar temperatures for the 18 o values of globigerina bulloides and neogloboquadrina pachyderma in contrast applying a single paleotemperature equation to g bulloides and n pachyderma 18 o yields different temperatures which has been used to suggest that these species record the surface to thermocline temperature gradient in santa barbara basin an isotopically distinct morphotype of g bulloides dominates during glacial intervals and yields temperatures that appear too cold when using a paleotemperature equation calibrated for the morphotype common today when a more appropriate paleotemperature equation is used for glacial g bulloides we obtain more realistic glacial temperatures glacial interglacial temperature differences g i t calculated in the present study indicate significant cooling 8 10 c throughout the southern california bight during the last glacial maximum lgm the magnitude of glacial cooling varies from 8 c near the middle of the southern california bight tanner basin and san nicolas basin to 9 c in the north santa barbara basin and 9 5 10 c in the south velero basin and no name basin our temperature calculations agree well with previous estimates based on the modern analog technique in contrast studies using n pachyderma coiling ratios u k 37 indices and transfer functions estimate considerably warmer lgm temperatures and smaller g i t

seasonal variation of ice ablation at the margin of the greenland ice sheet and its sensitivity to climate change qamanârssup sermia west greenland monthly ice ablation was measured at the margin of the greenland ice sheet for june july and august over 7 years 1980 86 the total winter ablation september may has also been measured and a simple ablation temperature model used to assign ablation values to individual months under the present climate the most ablation occurred in june august on average 81 of annual ablation moderate ablation took place in may and september 17 and very little ablation occurred in october april 2 the effect of climate change on ice ablation is simulated using the ablation model to recalculate ablation for higher temperatures summer ice ablation increases with temperature in the model but there is proportionally greater increase for may and september whereas the period from october to april is presently so cold that even a temperature rise of 5 c will hardly increase ablation the difference in annual ice ablation caused by future climate change will therefore depend upon the seasonal distribution of the temperature change changes in precipitation and accumulation will further modify the seasonal variation of ablation

sea surface temperature anomalies associated with the 1997 1998 el nino recorded in the oxygen isotope composition of planktonic foraminifera anomalously warm sea surface temperatures and associated high rainfall propagated northward from the eastern equatorial pacific along the western margin of north america during the 1997 1998 el nino we present data from the guaymas basin gulf of california and the santa barbara basin southern california borderlands that clearly demonstrate that the oxygen isotope composition of planktonic foraminifera accurately records the local sea surface temperature changes related to the el nino phenomenon on the basis of this observation the varved sediments accumulating in these basins should contain a detailed history of both the occurrence and intensity of past el nino events

new precipitation and accumulation maps for greenland annual total precipitation and the annual accumulation on the greenland ice sheet are evaluated and presented in two maps the maps are based on accumulation measurements of 25 1 pits and cores obtained from the upper accumulation zone and precipitation measurements made at 35 meteorological stations in the coastal region to construct the accumulation map the annual precipitation was split into solid and liquid precipitation components annual total precipitation exceeding 2500 mm w e occurs on the southeastern tip of greenland while the minimum precipitation is estimated to occur on the northeastern slope of the ice sheet the mean annual precipitation for all of greenland is 340 mm w e the largest annual accumulation of about 1500 mm w e is found on the glaciers in the southeastern corner of greenland while the smallest accumulation is found on the northeastern slope of the ice sheet west of danmarkshavn the mean accumulation on the greenland ice sheet is estimated at 310 mm w e the regional difference in accumulation is examined with respect to the 850 hpa m bar level circulation the present surface topography is found to play an important role in determining regional accumulation on the ice sheet

particulate organic carbon fluxes along upwelling dominated continental margins rates and mechanisms 1 time series sediment trap samples were used to examine the rates and mechanisms of particulate organic carbon poc flux at three continental margin locations santa barbara basin cariaco basin and guaymas basin marked by seasonal upwelling and high primary production the mean poc flux in santa barbara basin 0 096 g m 2 d 1 is nearly twice that of cariaco basin and 4 times higher than that in guaymas basin with all three sites having poc fluxes significantly higher than the open ocean average 0 007 g m 2 d 1 in cariaco basin the only site with available primary production numbers there is no significant relationship between poc flux and monthly primary production rather poc fluxes in all three areas strongly correlate with mineral carbonate opal and lithogenic material fluxes this supports the mineral ballast hypothesis where it has been suggested that higher density minerals enhance the flux of organic matter to the deep ocean on the basis of multiple regression analysis the three mineral components explain 72 of the total variance in poc fluxes at the three study sites with biogenic carbonate particles being the most effective transport mineral

rock fragments and soil hydrological processes significance and progress abstract in this review we explore the significance of rock fragments in studies of soil hydrological processes because according to research the effects of rock fragments on soil hydrological processes are inconsistent positive negative rock fragments play a critical role in the biosphere as the primary filter for water and solutions containing contaminants and heavy metals rock fragments have a complex influence on soil hydrological processes e g soil erosion runoff generation water infiltration solute transport and water flow and are highly relevant in a typical system in the soil plant atmosphere continuum cracks related to rock fragments provide preferential flow paths through which pollutants are transported into groundwater in this paper the published literature is reviewed concentrating on rock fragments and their effects on soil hydrological processes systematic studies and examples illustrate the effects of rock fragments architecture i e coverage content size position spatial heterogeneity morphology weathering and topography on soil hydrological processes methods and models applied to evaluate the effects of rock fragments on soil hydrological processes are examined in detail we conclude that the relationship between rock fragments and soil hydrological processes is complicated and requires more international research efforts this review concludes with a discussion of perspectives on areas of research that can improve understanding of the effects of rock fragments on soil hydrological processes with insights and suggestions also being provided regarding potential research trends requirements and solutions

aerodynamic stability and turbulent sensible heat flux over a melting ice surface the greenland ice sheet the turbulent sensible heat flux to a melting ice surface is calculated from wind speed and air temperature at 2 m over the ice surface assuming a certain wind profile with the appropriate surface roughness the aerodynamic stability of the boundary layer over melting ice is examined by comparing sensible heat fluxes for logarithmic and log linear wind profiles where the logarithmic profile is strictly valid only for neutral conditions increasing stability reduces the sensible heat flux to the glacier surface and introduces a non linear relation between heat flux and air temperature the stability effect is greatest at low wind speeds and fairly small at the high wind speeds that are common over the ice sheet earlier estimates of ablation by energy balance modelling may be too large due to neglect of stability but this was almost offset by using a surface roughness that was too small the log linear wind profile should be used in future energy balance models to take account of stability but more research is needed on the parameters of the profile as well as on the surface roughness

increased ablation at the margin of the greenland ice sheet under a greenhouse effect climate increased ablation under a greenhouse effec t climate is calculated by an energy balance model for two sites at the margin of the greenland ice sheet nordbogletscher south greenland and qaman lrssop sermia west greenland the change in summer ablation is nearly linear with change in summer temperature with gradients of 0 43 and 0 57 m water a i deg i for nordbogletscher and qamanarssup sermia respectively however the increase in ablation rate must be less in the higher parts of the ice sheet a future climatic warming will therefore cause a rapid retreat of the ice sheet margin and a steeper ice sheet profile

modeling the dissolution of settling caco3 in the ocean 1 the production transport and dissolution of carbonate shells plays an important role in the global carbon cycle for instance these processes affect the ocean s co32 concentration which on glacial interglacial timescales is involved in the regulation of atmospheric pco2 the saturation state of the ocean with respect to calcium carbonate suggests that any dissolution of calcium carbonate takes place not in the water column but at the seafloor on the other hand several authors suggest that a significant part of the dissolution takes place in the upper part of the water column in the present paper a simple model is presented to investigate under which circumstances dissolution of calcium carbonate in the water column may be plausible our analysis also includes dissolution facilitated by co2 release from organic carbon remineralization which may generate a microenvironment that is undersaturated with respect to caco3 in marine snow aggregates however respiration driven dissolution is shown to be insignificant due to the size and settling velocities of the aggregates with respect to aragonite dissolution in the water column attributable to the bulk saturation state alone is significant and may well contribute to the alkalinity maximum in the undersaturated intermediate waters of the north pacific ocean the suggested large loss of calcium carbonate dissolved in the water column 60 80 of caco3 production however cannot be explained by the mechanisms investigated here

impact of the ocean carbonate chemistry on living foraminiferal shell weight comment on carbonate ion concentration in glacial age deep waters of the caribbean sea by w s broecker and e clark broecker and clark 2002 use the size normalized weight of planktic foraminifera to estimate the carbonate ion concentration co3 of atlantic glacial upper deep water this method was introduced by lohmann 1995 and is based on the fact that within a defined size fraction dissolution decreases shell weight in proportion to the degree of undersaturation with respect to caco3 based on the following assumptions 1 the thickness of the foraminiferal shell wall does not depend on growth conditions 2 the saturation co3 for calcite co3 sat increases by 20 mol kg 1 km 1 broecker and clark 2001 3 the weight loss slope is universal and ca 0 3 g mol kg 1 1 broecker and clark 2001 4 the offset between the bottom water and pore water co3 was the same during glacial time as during the holocene broecker and clark 2002 calculate that the co3 of atlantic glacial upper deep water was 14 mol kg 1 higher than during the holocene although they recognize that some of their assumptions are not strictly valid they do not assess the impact of those assumptions on their co3 estimate here we comment on several of those assumptions and attempt to quantify their impact on broecker and clark s 2002 calculations

mapping tide water glacier dynamics in east greenland using landsat data landsat multispectral scanner and thematic mapper images were co registered for the kangerdlugssuaq fjord region in east greenland and were used to map glacier drainage basin areas changes in the positions of tide water glacier termini and to estimate surface velocities of the larger tide water glaciers statistics were compiled to document distance and area changes to glacier termini the methodologies developed in this study are broadly applicable to the investigation of tide water glaciers in other areas the number of images available for consecutive years and the accuracy with which images are co registered are key factors that influence the degree to which regional glacier dynamics can be characterized using remotely sensed data three domains of glacier state were interpreted net increase in terminus area in the southern part of the study area net loss of terminus area for glaciers in upper kangerdlugssuaq fjord and a slight loss of glacier terminus area northward from ryberg fjord local increases in the concentrations of drifting icebergs in the fjords coincide with the observed extension of glacier termini positions ice surface velocity estimates were derived for several glaciers using automated image cross correlation techniques the velocity determined for kangerdlugssuaq gletscher is approximately 5 0 km a 1 and that for kong christian iv gletscher is 0 9 km a 1 the continuous presence of icebergs and brash ice in front of these glaciers indicates sustained rates of ice front calving

calculated variations of annual ice ablation at the margin of the greenland ice sheet west greenland 1961 90 annual ice ablation has been measured at three locations at the margin of the greenland ice sheet nordbogletscher for 6 years 1977 78 to 1982 83 qaman rssup sermia 8 years 1979 80 to 1986 87 and at paakitsup akuliarusersua 7 years 1982 83 to the present as the data sets cover different periods it is difficult to compare ablation directly between the three sites however measured series at each site can be extended over the last 30 years 1961 90 by simulations using climatic data and the extended data series can be compared

planktonic foraminiferal fluxes in the santa barbara basin response to seasonal and interannual hydrographic changes results of a three year time series sediment trap experiment in the santa barbara basin indicate linkages between water column dynamics and variations in plankton fluxes on both seasonal and interannual time scales the two week collection interval utilized for this study allows evaluation of high frequency changes in the production and flux of planktonic foraminifera which are compared to those of siliceous microorganisms diatoms radiolaria and silicoflagellates annual hydrographic conditions in santa barbara basin are influenced by seasonal changes in insolation the wind field and source waters this study includes periods of weak to moderate el nino conditions followed by a transitional period to a non el nino state planktonic foraminiferal fluxes and species turnover are related to seasonal and interannual changes in source waters and water column conditions globigerina bulloides g quinqueloba and neogloboquadrina pachyderma dextral dominate the planktonic foraminiferal population in this location and are present throughout the year globigerina bulloides and g quinqueloba have similar flux patterns and highest fluxes occur in association with diatom blooms the flux patterns of g bulloides and g quinqueloba in general are inversely related to that of n pachyderma dextral globigerina quinqueloba seems to respond earlier to the onset of upwelling than g bulloides three temperature limited species neogloboquadrina dutertrei orbulina universa and globigerinoides ruber are present in lower numbers and show more restricted seasonal ranges in the thermal regime of the santa barbara basin n dutertrei like o universa disappears during upwelling neogloboquadrina dutertrei occurs in highest abundance when the water column is thermally stratified and there is a well developed deep chlorophyll maximum increased fluxes of globigerinoi ruber the most thermally restricted of the dominant species in the basin are associated with the presence of warm oceanic diatoms and warm water radiolarians total planktonic foraminiferal fluxes were lower in 1995 than during the previous two years which were characterized by el nino conditions

variations of near surface firn density in the lower accumulation area of the greenland ice sheet pâkitsoq west greenland firn density variations have been studied in the lower accumulation area of the greenland ice sheet 1440 1620 m a s l near p kitsoq west greenland the main control on density in the near surface firn layer of 5 10 m thickness is the formation of ice layers by the refreezing of meltwater that reaches depths of 2 4 m below the surface the density variations are described by the ratio of annual surface melt m to the annual accumulation c the ratio m c is about 0 6 at the run off limit at about 1400 m a s l in the study area where refreezing of meltwater transforms snow into impermeable ice the mean density of near surface firn decreases with elevation reflecting a decrease in melt with elevation there is a surprising decrease in firn density at depths of more than about 4 m below the 1991 summer surface which reflects lower melt rates and or higher accumulation in the early 1980s and late 1970s when this firn was passing through the surface layer the formation of such low density firn may have partially contributed to the 1978 85 thickening of the ice sheet observed by satellite radar altimetry near surface firn density is therefore very sensitive to climate change and might be an attractive target for climate monitoring

geochemical imprints of genotypic variants of globigerina bulloides in the arabian sea planktonic foraminifera record oceanic conditions in their shell geochemistry many palaeoenvironmental studies have used fossil planktonic foraminifera to constrain past seawater properties by defining species based on their shell morphology recent genetic studies however have identified ecologically distinct genotypes within traditionally recognized morphospecies signaling potential repercussions for palaeoclimate reconstructions here we demonstrate how the presence of globigerina bulloides cryptic genotypes in the arabian sea may influence geochemical signals of living and fossil assemblages of these morphospecies we have identified two distinct genotypes of g bulloides with either cool water type ii or warm water type i temperature preferences in the western arabian sea we accompany these genetic studies with analyses of mg ca and stable oxygen isotope 18o compositions of individual g bulloides shells both mg ca and 18o values display bimodal distribution patterns the distribution of mg ca values cannot be simply explained by seawater parameters and we attribute it to genotype specific biological controls on the shell geochemistry the wide range of 18o values in the fossil assemblage also suggests that similar controls likely influence this proxy in addition to environmental parameters however the magnitude of this effect on the 18o signals is not clear from our data set and further work is needed to clarify this we also discuss current evidence of potential genotype specific geochemical signals in published data on g bulloides geochemistry and other planktonic foraminiferal species we conclude that significant caution should be taken when utilizing g bulloides geochemistry for paleoclimate reconstruction in the regions with upwelling activity or oceanographic fronts

sediment fluxes and varve formation in santa barbara basin offshore california results from a year long sediment trap study provide the first direct observations of seasonal variability in sediment fluxes to the sea floor in santa barbara basin offshore california and are used to evaluate varve formation in this basin sediment fluxes throughout the year are dominated by lithogenic material biogenic sediments primarily silica are of secondary importance we conclude that the combination of high lithogenic fluxes and low biogenic fluxes during the fall winter period results in the deposition of dark laminae the onset of upwelling and high surface productivity in the spring results in high biogenic silica fluxes that last into the summer the relative contribution of silica to the total sediment flux is highest during this spring summer period and we suggest that light laminae are formed at that time this is consistent with previous suggestions that sediment input is the primary factor controlling varve formation in this basin

calcification of the planktonic foraminifera globigerina bulloides and carbonate ion concentration results from the santa barbara basin planktonic foraminiferal calcification intensity reflected by shell wall thickness has been hypothesized to covary with the carbonate chemistry of seawater here we use both sediment trap and box core samples from the santa barbara basin to evaluate the relationship between the calcification intensity of the planktonic foraminifera species globigerina bulloides measured by area density g m2 and the carbonate ion concentration of seawater co32 we also evaluate the influence of both temperature and nutrient concentration po43 on foraminiferal calcification and growth the presence of two g bulloides morphospecies with systematically different calcification properties and offset stable isotopic compositions was identified within sampling populations using distinguishing morphometric characteristics the calcification temperature and by extension calcification depth of the more abundant normal g bulloides morphospecies was determined using 18o temperature estimates calcification depths vary seasonally with upwelling and were used to select the appropriate co32 temperature and po43 depth measurements for comparison with area density seasonal upwelling in the study region also results in collinearity between independent variables complicating a straightforward statistical analysis to address this issue we use additional statistical diagnostics and a down core record to disentangle the respective roles of each parameter on g bulloides calcification our results indicate that co32 is the primary variable controlling calcification intensity while temperature influences shell size we report a modern calibration for the normal g bulloides morphospecies that can be used in down core studies of well preserved sediments to estimate past co32

oxygen and carbon isotopes of individual shells of planktonic foraminifera from ontong java plateau equatorial pacific abstract analyses of single shells of orbulina universa and two other species show ranges of 2 in 18 o and 13 c at various levels in a box core from the western equatorial pacific seasonal and inter annual variations can account for only about half of this range variations in depths of calcification and in metabolic effects must account for the rest the large range must introduce considerable noise in multi shell analysis unless the number of shells in the sample is of the order of 50 or more we did not find a change in the range downcore nor did we find any evidence for the deglacial meltwater spike

effects of climatic perturbations on the equilibrium line altitude west greenland perturbation analysis is applied to the heat balance at the egig line west greenland with respect to climatic changes the shift of the equilibrium line altitude is obtained for perturbations of temperature absolute humidity cloudiness and annual accumulation the total net ice ablation at the egig line increases by 45 with a perturbation of 1 k

temperature accumulation and ice sheet elevation in central greenland through the last deglacial transition we present a combined heat and ice flow model constrained by measurements of temperature in the greenland ice sheet project 2 gisp2 borehole and by the gisp2 18o record and depth age scale which determines a history of temperature accumulation rate and ice sheet elevation for the past 50 000 years in central greenland important results are that the temperature increase from average glacial to holocene conditions was large approximately 15 c with a 20 c warming from late glacial to holocene that the average accumulation rate during the last glacial maximum between 15 and 30 kyr b p was 5 5 to 7 cm yr 1 approximately 25 of the modern accumulation rate that long term 500 1000 years averaged accumulation rate and temperature have been inversely correlated during the most recent 7 millennia of the holocene and that the greenland ice sheet probably thickened during the deglacial transition the inverse correlation of accumulation rate and temperature in the mid and late holocene suggests that the greenland ice sheet is more prone to volume reduction in a warmed climate than previously thought and demonstrates that accumulation rate is not a reliable proxy for temperature the elevation history of the ice sheet is poorly constrained by the model and independent evidence is needed we also present a simple estimate of the response time for thinning of the interior region of an ice sheet due to retreat of its margins this was approximately 1900 years for central greenland during deglaciation

conservation of soil moisture by different stone covers on alpine talus slopes lassen california abstract this study reports on the influence of stone covers with different clast sizes on the soil moisture of alpine talus slopes in lassen california fifteen four plot sets were sampled in the dry season july 1990 in sandy areas and in talus covered with pebbles cobbles or blocks between 2740 and 2775 m three depths 0 5 5 10 10 15 cm were sampled field moisture content increased gradually with depth in all soil profiles and also in plots covered by increasingly larger rocks surface soils in sand areas were very dry but under rocks had water contents 6 to 14 times greater differences among plots decreased with depth but subsoil samples in sand were still drier than those beneath any stone cover at similar depths blocks were most effective in conserving moisture water content below them was higher than even in deep 10 15 cm sand soils soil temperatures were recorded in sand and under blocks for an 11 day period minima were not significantly different but average maxima were 5 6 c lower under blocks than in sand which reached highs 4 4 c lower than the air differences in soil moisture among talus types are ascribed to lower evaporation losses under stones due to both disruption of capillarity by the coarse particles which prevented water flow to the talus surface and to their efficient reduction of maximum temperatures an irrigation experiment was conducted at 2110 m on a steep talus on the chaos crags from july 18 to aug 2 1993 four 100 75 cm plots with the same surface types than at lassen received 22 5 mm water moisture content was then periodically sampled watering produced similar water distributions among soil depths and talus types to those in lassen evaporation occurred quickly in bare soils due to high air and soil temperatures the sand surface was already dry 2 days after watering but stone covered plots remained moist until day 15 when soils under blocks still retained 77 97 of the water content percent by weight at the start of the test

environmental controls on b ca in calcite tests of the tropical planktic foraminifer species globigerinoides ruber and globigerinoides sacculifer abstract the ratio of boron to calcium b ca in the calcite tests of planktic foraminifers may serve as a proxy for past seawater chemistry but controls on b incorporation are not yet certain here we present the results of laboratory culture experiments with live specimens of globigerinoides ruber pink and globigerinoides sacculifer which provide new insight into b incorporation controls we find that in g sacculifer b ca increases with increasing ph lower hco3 higher co32 and b oh 4 but decreases with increasing total dissolved inorganic carbon dic higher hco3 and co32 constant b oh 4 this suggests competition between aqueous boron and carbon species for inclusion into the calcite lattice similar to previous experiments with the subtropical temperate orbulina universa b ca increases with salinity but not with temperature we evaluate possible carbonate system control parameters and compare our tropical culture calibrations with new and published core top data

concentrated flow erosion rates as affected by rock fragment cover and initial soil moisture content abstract concentrated flow experiments using a small hydraulic flume and a constant flow discharge and bed slope have been conducted in order to investigate the effects of rock fragment cover rc on sediment yield for an initially wet and an initially air dry loamy topsoil the experimental results indicate that rc reduces concentrated flow erosion rates e in an exponential way i e e e brc which is similar to previously reported relations for other water erosion processes such as interrill erosion and sheet rill erosion measured on runoff plots the decay rate b of this exponential relationship increased throughout the experiments because of scour hole development and bed armouring the concentrated flow erosion rates and b values also depend on the initial moisture content of the topsoil depending on rc mean concentrated flow erosion rates were 20 to 65 less on initially wet compared to initially air dry topsoils the mean value for b was 0 032 for the initially wet but only 0 017 for the initially air dry topsoil indicating that a rock fragment cover is less efficient in reducing concentrated flow erosion rates when the topsoil is initially air dry than when it is initially wet the results help explain the data scatter in reported relationships between rc and interrill rill erosion rates they also indicate that a given surface rock fragment cover will offer more protection to wet topsoils than to dry topsoils which are very common in mediterranean environments event based water erosion models should incorporate effects of antecedent soil moisture content as well as those of rc on concentrated flow erosion rates