rates of weathering rind formation on costa rican basalt weathering rind thicknesses were measured on 200 basaltic clasts collected from three regionally extensive alluvial fill terraces qt 1 qt 2 and qt 3 preserved along the pacific coast of costa rica mass balance calculations suggest that conversion of unweathered basaltic core minerals plagioclase and augite to authigenic minerals in the porous rind kaolinite allophane gibbsite fe oxyhydroxides is iso volumetric and ti and zr are relatively immobile the hierarchy of cation mobility ca na k mg si al fe p is similar to other tropical weathering profiles and is indicative of differential rates of mineral weathering anorthite albite hypersthene orthoclase apatite alteration profiles across the cm thick rinds document dissolution of plagioclase and augite and the growth of kaolinite with subsequent dissolution of kaolinite and precipitation of gibbsite as weathering rinds age the rate of weathering rind advance is evaluated using a diffusion limited model which predicts a parabolic rate law for weathering rind thickness rr as a function of time t rr t and an interface limited model which predicts a linear rate law for weathering rind thickness as a function of time rr kappt in these rate laws is a diffusion parameter and kapp is an apparent rate constant the rate of advance is best fit by the interface model terrace exposures are confined to the lower reaches of streams draining the pacific slope near the coast where the stream gradient is less than 3 m km and terrace deposition is influenced by eustatic sea level fluctuations geomorphological evidence is consistent with terrace deposition coincident with sea level maxima when the stream gradient would be lowest assigning the most weathered regionally extensive terrace qt 1 mean rind thickness 6 9 0 6cm to oxygen isotope stage ois 7 ca 240 ka and assuming that at time 0 rind thickness 0 it is inferred that terrace qt 2 rr 2 9 0 1 cm is coincident with stage 5e ca 125 ka and that qt 3 rr 0 9 0 1 cm is consistent with ois 3 ca 37 ka these assignments yield a value of kapp of 8 6 10 13 cm s 1 r 2 0 99 only this value satisfies both the existing age controls and yields ages coincident with sea level maxima using this value elemental weathering release fluxes across a weathering rind from qt 2 range from 6 0 10 9 mol si m 2 s 1 to 2 5 10 11 mol km 2 s 1 the rate of rind advance for the costa rican terraces is 2 8 10 7 my r 1 basalt rind formation rates in lower temperature settings described in the literature are also consistent with interface controlled weathering with an apparent activation energy of about 50 kj mol 1 rates of rind formation in costa rica are an order of magnitude slower than reported for global averages of soil formation rates copyright 2004 elsevier ltd

contributions of the siberian shelf polynyas to the arctic ocean intermediate and deep water the role of the open water regions or polynyas in the winter ice pack over the siberian continental shelves in the production of arctic ocean intermediate and deep water is examined through use of a combination of passive microwave satellite data coastal weather station data and oceanographic data the satellite data allow us to derive a time series of the open water areas of selected polynyas for the 1978 1982 winters the polynyas which occur north of svalbard around franz josef land along the west coast and north end of novaya zemlya and to the east of severnaya zemlya and the taymyr peninsula are the primary oceanographic contributors the open water time series for these polynyas are used in combination with coastal weather station data to estimate the heat loss from each polynya for the region north of svalbard which is historically known as whalers bay the study shows that the heat loss is sufficient to provide the observed cooling of the west spitsbergen current for the other polynyas the heat loss is used to compute the ice production rates and the oceanic salt flux we then use the historic oceanographic salinities with the salt fluxes to estimate the contribution of each polynya to the arctic ocean water masses if we assume that the salt contributes only to the arctic intermediate water our results show that the shelves are capable of producing about 20 60 of this water alternatively if the salt contributes only to the deep water of the eurasian basin then without consideration of the mixing of the bottom water with the greenland and norwegian sea water the contribution from the shelves yields a renewal time of about 100 years our results imply that there is insufficient water produced in the shelf polynyas to perform all of the roles that have been historically assigned to it

element mobilization and redistribution under extreme tropical weathering of basalts from the hainan island south china abstract chemical weathering of rocks has substantial influence on the global geochemical cycle in this paper the geochemical profile of a well developed basalt weathering profile 15 m thick including soil saprolite semi weathered rock and fresh basalt on the island of hainan south china was presented the soil and saprolite samples from this profile are characterized by high al2o3 and fe2o3 concentrations up to 32 3 and 28 5 respectively the mineral assemblage is dominated by kaolinite fe oxides hydroxides and gibbsite or boehmite indicating extensive desilicate and ferrallitic weathering the acidic and organic rich environment in the soil horizon may have promoted elemental remobilization and leaching the strongest sio2 depletion and al2o3 enrichment at about 2 4 m deep indicate that the main kaolinite hydrolysis and gibbsite formation occurred near the soil saprolite interface the mild sr reconcentration at about 3 9 m and 7 1 m deep may be attributed to secondary carbonate precipitation mn oxides hydroxides precipitated at 6 1 m deep accompanied by the strongest enrichment of ba and co uranium is mildly enriched in the middle part about 7 1 m and 9 1 m deep of the weathering profile and the enrichment may have been caused by the decomposition of uranyl carbonates or the accumulation of zircon immobile element i e zr hf nb ta th and ti distributions at different depths are mainly controlled by secondary fe oxides hydroxides and follow the stability sequence of nb ta th zr hf ti the limited thickness 15 cm of the semi weathered basalt horizon at the rock regolith interface 15 28 m deep suggests that plagioclase and pyroxene are readily altered to kaolinite smectite and fe oxides under tropical climate the marked enrichment of transitional metals such as cu zn ni and sc along the rock regolith interface may have associated mainly with increasing ph values as well as the dissolution of primary apatite and formation of secondary phosphates our findings highlight the importance of secondary phosphates in the redistribution of transition metals and in the possible mg cu and ni isotopic fractionation under extreme weathering of basalt in tropic climate

correlation of river water and local sea ice melting on the laptev sea shelf siberian arctic hydrographic and stable isotope 18o data from 4 summer surveys in the laptev sea are used to derive fractions of sea ice meltwater and river water sea ice meltwater fractions are found to be correlated to river water fractions while initial heat of river discharge is too small to melt the observed 0 158 km3 of sea ice meltwater arctic rivers contain suspended particles spm and colored dissolved organic material cdom that preferentially absorb solar radiation accordingly heat content in surface waters is correlated to river water fractions but in years when river water is largely absent within the surface layer absolute heat content values increase to considerably higher values with extended exposure time to solar radiation and sensible heat nevertheless no net sea ice melting is observed on the shelf in years when river water is largely absent within the surface layer the total freshwater volume of the central eastern laptev sea 72 76 n 122 140 e varies between 1000 1500 km3 34 92 reference salinity it is dominated by varying river water volumes 1300 1800 km3 reduced by an about constant freshwater deficit 350 400 km3 related to sea ice formation net sea ice melt 109 158 km3 is only present in years with high river water budgets intermediate to bottom layer 25 salinities contain 60 and 30 of the river budget in years with low and high river budgets respectively the average mean residence time of shelf waters was 2 3 years during 2007 2009

the freshwater budget and under ice spreading of mackenzie river water in the canadian beaufort sea based on salinity and 18o 16o measurements in water and ice observations of salinity and oxygen isotope composition 18o were made for the beaufort shelf mackenzie estuary waters in september 1990 just prior to ice formation and for both the water column and ice in april may 1991 at the end of winter these measurements are used to determine the apportioning of fresh water in the estuary between its two main sources runoff and sea ice melt changes in disposition of water between seasons and amounts frozen into the growing ice sheet are also derived two domains are considered in order to construct a freshwater budget for the mackenzie shelf the nearshore within which landfast ice grows in winter and the outer shelf most of the winter inflow from the mackenzie river appears to remain impounded as liquid under the ice within the landfast zone at the end of winter and about 15 of it is incorporated into the landfast ice oxygen isotopes 18o in ice cores collected from across the shelf record the progress beneath the ice of new mackenzie inflow as it invades the nearshore throughout winter rates of spreading are about 0 2 cm s 1 away from the coast and 1 3 cm s 1 along the coast as this inflow spreads across the shelf it progressively shuts off convection driven by brine production at locations within the landfast ice salinity and 18o in the offshore water column suggest that about 3 m of sea ice was formed in the outer shelf domain since both brine and newly formed sea ice can be advected off the shelf a complete budget for brine or sea ice production cannot be established without first measuring the advection of one of these two components

two circulation regimes of the wind driven arctic ocean the major goal of this paper is to demonstrate the existence in the arctic ocean of two regimes of wind forced circulation we simulated the vertically averaged currents sea level heights and ice drift in the arctic ocean from 1946 to 1993 using a two dimensional wind forced barotropic model that includes frictional coupling between the ocean and ice the model has a spatial resolution of 55 5 km and is driven by winds river runoff and an imposed but realistic sea level slope between the pacific and the atlantic oceans there is a good agreement between velocities from observed buoy motions and velocities of modeled ice drift even though the model lacks ocean baroclinicity and ice thermodynamics the results indicate that wind driven motion in the central arctic alternates between anticyclonic and cyclonic circulation with each regime persisting for 5 7 years based upon our analysis of the modeled sea level and ice motion anticyclonic wind driven motion in the central arctic appeared during 1946 1952 1958 1963 1972 1979 and 1984 1988 and cyclonic motion appeared during 1953 1957 1964 1971 1980 1983 and 1989 1993 shifts from one regime to another are forced by changes in the location and intensity of the icelandic low and the siberian high the two regimes may help explain the significant basin scale changes in the arctic s temperature and salinity structure observed recently the great salinity anomaly and the variability of ice conditions in the arctic ocean

freshwater balance and the sources of deep and bottom waters in the arctic ocean inferred from the distribution of h218o data from sections across the eurasian basin of the arctic ocean occupied in 1987 and 1991 are used to derive information on the freshwater balance of the arctic ocean and on sources of the deep waters of the nansen amundsen and makarov basins using salinity h218o and mass balances we estimate the river runoff and the sea ice melt water fractions contained in the upper waters of the arctic ocean and infer pathways of the river runoff signal from the shelf seas across the central arctic ocean to fram strait the average mean residence time of the river runoff fraction contained in the arctic ocean halocline is determined to be about 11 to 14 years pacific water entering through bering strait is traced using silicate and its influence on the halocline waters of the canadian basin is estimated water column inventories of river runoff and sea ice melt water are calculated for a section just north of fram strait and implications of these inventories for sea ice export through fram strait are discussed comparison of the 18o 16o ratios of shelf water atlantic water and the deep waters of the arctic ocean indicate that the sources of the deep and bottom waters of the eurasian basin are located in the barents and kara seas

surface chemical properties and pedogenesis of tropical soils derived from basalts with different ages in hainan china abstract limited information is available on the changes of surface chemical properties of tropical soils with time during the pedogenesis soil samples of three profiles derived from basalts of 10 1330 and 2290 kilo annum ka in age were collected from adjacent locations in a tropical region of hainan province china the changes in soil surface chemical properties and the mineralogy of the soil clay fraction with time were investigated using ion adsorption micro electrophoresis and x ray diffraction analysis the content of 2 1 type clay minerals decreased while those of kaolinite and gibbsite increased with increasing basalt age and degree of soil development the content of pedogenic free iron fe oxides and the ratio of free fe oxides total fe oxides increased with soil development stage while soil poorly crystalline fe and aluminum al oxides had an opposite trend the positive surface charge of the soils increased with increasing basalt age and degree of soil development this was consistent with the change in their contents of free fe al oxides however the value of negative surface charge had an opposite behavior the soil derived from 10 ka basalt had much more negative charge than soils derived from 1330 and 2290 ka basalt soil net surface charge and zeta potential of the soil clay fraction decreased with the increase in basalt age both net charge ph curves and zeta potential ph curves shifted to positive values with increased basalt age and degree of soil development increasing age also elevated the point of zero net charge of the soil and the isoelectric point of soil colloids

geochronology and geochemistry of late cenozoic basalts from the leiqiong area southern china abstract the leiqiong area which includes the leizhou peninsula and the northern part of the hainan island is the largest province of exposed basalts in southern china ar ar and k ar dating indicates that incipient volcanism in the leiqiong area may have taken place in late oligocene time and gradually increased in tempo toward the miocene and pliocene epoch volcanic activities were most extensive during pleistocene and declined and ended in holocene based on radiometric age dating and geographic distribution pliocene and quaternary volcanism in hainan island can be grouped into two stages and six eruptive regions the early volcanism is dominated by flood type fissure eruption of quartz tholeiites and olivine tholeiites whereas the later phase is dominated by central type eruption of alkali olivine basalts and olivine tholeiites the systematic decrease of mgo feo and tio 2 with increasing sio 2 content for basalts from hainan island indicates that fractional crystallization of olivine clinopyroxene and ti bearing opaques may have occurred during magmatic evolution from coexisting fe ti oxide minerals it is estimated that the equilibrium temperatures range from 895 986 c and oxygen fugacities range from 10 13 4 to 10 10 7 atmospheres in the basaltic magmas the incompatible element ratios and the chondrite normalized ree patterns of basalts from the leiqiong area are generally similar to oib the nb u ratios less than 37 in most of the tholeiitic rocks and the negative nb anomaly observed in the spidergram of some basalts indicated that the influence of a paleo subduction zone derived component can not be excluded in considering the genesis of the basalts from the leiqiong area the tholeiites in the leiqiong area may have mixed with a more enriched lithospheric mantle component as well as undergone relatively larger percentages of partial melting than the alkali basalts

pedogenesis significantly decreases the stability of water dispersible soil colloids in a humid tropical region abstract the stability of soil colloids influences soil physicochemical properties soil development and transfer of nutrients and contaminants to surface and ground waters a better understanding of soil colloids stability dynamics during soil evolution is important for the evaluation of soil s capacity to retain nutrients and or accommodate toxic contaminants this study was aimed to determine changes in the stability of water dispersible soil colloids that accompany mineral transformation and surface charge evolution during pedogenesis using a well characterized chronosequence derived from basalt in the humid tropical region of hainan island south china the results demonstrated that the ph dependent colloid stability decreased significantly with tropical soil development which we attribute to the substantial changes in clay mineral compositions and colloid surface charge properties clay minerals in the studied chronosequence were characterized by an increase of kaolinite gibbsite and fe oxides and a decrease of quartz and halloysite towards more advanced stages of weathering which resulted in the decline of permanent negative charges in the older soils the point of zero charge phpzc increased while ph decreased across the tropical soil chronosequence being in good agreement with the observed lower colloid stability in aged soils dominated by kaolinitic minerals our study of colloid stability at long term pedogenic time scale suggests young tropical soils

stable oxygen and carbon isotopes in planktonic foraminifera neogloboquadrina pachyderma in the arctic ocean an overview of published and new surface sediment data abstract a summary study on oxygen and carbon stable isotopes in planktonic foraminifera from arctic ocean floor appeared in marine geology 20 years ago spielhagen and erlenkeuser 1994 we revisit this topic with a wealth of new data focused on the western amerasian arctic a spotlight in the current climatic and oceanic change neogloboquadrina pachyderma the most abundant polar planktonic foraminiferal species is an important tool for reconstructing surface subsurface water changes in the arctic our new data on n pachyderma 150 250 m from the surface sediments show 18 o and 13 c values of 18 o and 13 c are both influenced by complex water sources water column structure and foraminiferal depth habitat the observed distribution of n pachyderma stable isotopes confirms a shallow habitat of this species in the sea ice covered central arctic especially in the canada basin probably in relation to the shallow chlorophyll maximum the associated light n pachyderma 18 o reflects the long term storage of fresh water at the shelf break a deeper dwelling of n pachyderma with heavier 18 o is supported by a more extensive photic zone and nutrient availability air sea exchange plays an important role in 13 c distribution and is consistent with heavy n pachyderma 13 c in the perennially ice covered central arctic ocean light 13 c composition at the shelf break is additionally influenced by shelf bottom waters enriched in isotopically light remineralized terrestrial carbon distribution of foraminiferal 13 c on the chukchi shelf reflects primary production patterns in the area

the laptev sea as a source for recent arctic ocean salinity changes this study was motivated by observations of significant salinification of the upper eurasian basin that began around 1989 observational data and modeling results provide evidence that increased arctic atmospheric cyclonicity in the 1990s resulted in a dramatic increase of the salinity in the eurasian basin two mechanisms account for the laptev sea salinization eastward diversion of russian rivers and increased brine formation due to enhanced ice production in numerous leads in the laptev sea ice cover both these mechanisms are linked to changes in wind patterns and were essential to the formation of salinity anomalies the resulting laptev sea salinity anomaly was advected to the central eurasian basin the strong salinization over the eurasian basin altered the formation of cold halocline waters weakened vertical stratification and released heat upward from below the cold halocline layer our analysis suggests that local processes in the laptev sea may have a basin wide impact on the thermohaline structure of the arctic ocean

river runoff sea ice meltwater and pacific water distribution and mean residence times in the arctic ocean hydrographic and tracer data collected during ark iv 3 fs polarstern in 1987 arctic91 ib oden and aos94 ccgs louis s st laurent expeditions reveal the evolution of the near surface waters in the arctic ocean during the late 1980s and early 1990s salinity nutrients dissolved oxygen and 18 o data are used to quantify the components of arctic freshwater river runoff sea ice meltwater and pacific water the calculated river runoff fractions suggest that in 1994 a large portion of water from the pechora ob yenisey kotuy and lena rivers did not flow off the shelf closest to their river deltas but remained on the shelf and traveled via cyclonic circulation into the laptev and east siberian seas river runoff flowed off the shelf at the lomonosov ridge and most left the shelf at the mendeleyev ridge arctic91 and aos94 pacific water fraction estimates of upper halocline water the traditionally defined core of the pacific water mass document a decrease in extent compared to historical data the front between atlantic water and pacific water shifted from the lomonosov ridge location in 1991 to the mendeleyev ridge in 1994 the relative age structure of the upper waters is described by using the 3 h 3 he age the mean 3 h 3 he age measured in the halocline within the salinity surface of 33 1 0 3 is 4 3 1 7 years and that for the 34 2 0 2 salinity surface is 9 6 4 6 years lateral variations in the relative age structure within the halocline and atlantic water support the well known cyclonic boundary current circulation

a meteoric water budget for the arctic ocean a budget of meteoric water mw river runoff net precipitation minus evaporation and glacial meltwater over four regions of the arctic ocean is constructed using a simple box model regional precipitation evaporation estimates from reanalysis data sets and estimates of import and export fluxes derived from the literature with a focus on the 2003 2008 period the budget indicates an approximate slightly positive balance between mw imports and exports i e no change in storage thus the observed total freshwater increase observed during this time period likely resulted primarily from changes in non mw freshwater components i e increases in sea ice melt or pacific water and or a decrease in ice export further our analysis indicates that the mw increase observed in the canada basin resulted from a spatial redistribution of mw over the arctic ocean mean residence times for mw were estimated for the western arctic 5 7 years eastern arctic 3 4 years and lincoln sea 1 2 years the mw content over the siberian shelves was estimated 14 000 km3 based on a residence time of 3 5 years the mw content over the entire arctic ocean was estimated to be 44 000 km3 the mw export through fram strait consisted mostly of water from the eastern arctic 3 237 1 370 km3 yr 1 whereas the export through the canadian archipelago was nearly equally derived from both the western arctic 1 182 534 km3 yr 1 and lincoln sea 972 391 km3 yr 1

exchange of laptev sea and arctic ocean halocline waters in response to atmospheric forcing combined delta o18 salinity data reveal a distinctive water mass generated during winter sea ice formation which is found predominantly in the coastal polynya region of the southern laptev sea export of the brine enriched bottom water shows interannual variability in correlation with atmospheric conditions summer anticyclonic circulation is favoring an offshore transport of river water at the surface as well as a pronounced signal of brine enriched waters at about 50 m water depth at the shelf break summer cyclonic atmospheric circulation favors onshore or an eastward alongshore water transport and at the shelf break the river water fraction is reduced and the pronounced brine signal is missing while on the middle laptev sea shelf brine enriched waters are found in high proportions residence times of bottom and subsurface waters on the shelf may thereby vary considerably an export of shelf waters to the arctic ocean halocline might be shut down or strongly reduced during onshore cyclonic atmospheric circulation while with offshore anticyclonic atmospheric circulation brine waters are exported and residence times may be as short as 1 year only

wind driven transport pathways for eurasian arctic river discharge distributions of temperature salinity and barium in near surface waters depth 50 m of the laptev sea and adjacent areas of the arctic ocean are presented for the summers of 1993 1995 and 1996 the tracer data indicate that while fluvial discharge was largely confined to the shelf region of the laptev sea in the summer of 1993 surface waters containing a significant fluvial component extended beyond the shelf break and over the slope and basin areas north of the laptev sea in the summers of 1995 and 1996 these distributions of fluvial discharge are consistent with local winds and suggest two principal pathways by which river waters can enter the central arctic basins from the laptev sea when southerly to southeasterly wind conditions prevail river waters are transported northward beyond the shelf break and over the slope and adjacent basin areas these waters can then enter the interior arctic ocean via upper layer flow in the vicinity of the lomonosov ridge under other wind conditions river waters are steered primarily along the inner laptev shelf and into the east siberian sea as part of the predominantly eastward coastal current system these waters then appear to cross the shelf and enter the interior arctic ocean via upper layer flow aligned roughly along the mendeleyev ridge the extent to which either pathway is favored in a given year is largely determined by local wind patterns during the summer months when fluvial discharge is greatest and shelf waters are at the lowest salinity of their annual cycle

clay minerals in a soil chronosequence derived from basalt on hainan island china and its implication for pedogenesis abstract a soil chronosequence consisting of six profiles formed on quartz tholeiite basalt ranging in age from 10 000 years to 1 8 million years my was studied here soil clays were identified using xrd diffractogram decomposition methods for samples obtained from the a and c horizons of profiles the results showed that kaolinite minerals dominated in all the clay fractions gibbsite was prominent in the c horizons in the soils from older rocks clays in the a horizon of relatively young soils showed an initial stage of illite formation followed by smectite mixed layer minerals illite smectites and then vermiculite illite and finally by vermiculite the initial presence of illite is interesting as there is no magmatic micaceous or phyllosilicate phase in these basalts and the formation of illite we attribute to a secondary process probably created by alkali transport by plant materials the change in 2 1 clay mineralogy reflects the overall change in si al ratios in the soils over longer periods of weathering in all cases gibbsite is more abundant in the c horizons than the a horizons the difference in gibbsite content between the a and c horizons we attribute to plant transport of siliceous phytolite material to the surface continued high rainfall over long periods of time removed the alkali faster than the plants could bring it to the surface which led to continuous lowering of 2 1 minerals from younger to older in the soil chronosequence nevertheless a 2 1 silica rich mineral persists in the clay assemblages although in very minor amounts

wind driven summer surface hydrography of the eastern siberian shelf 1 high interannual variability of summer surface salinity over the laptev and east siberian sea shelves derived from historical records of the 1950s 2000s is attributed to atmospheric vorticity variations in the cyclonic regime positive vorticity the eastward diversion of the laptev sea riverine water results in a negative salinity anomaly to the east of the lena delta and farther to the east siberian sea and a positive anomaly to the north of the lena delta anticyclonic negative vorticity results in negative salinity anomalies northward from the lena delta due to freshwater advection toward the north and a corresponding salinity increase eastward

the influence of soil age and regional climate on clay mineralogy and cation exchange capacity of moist tropical soils a case study from late quaternary chronosequences in costa rica abstract tropical soils exhibit large differences across landscapes in many attributes notably clay mineralogy 2 1 vs 1 1 clays bulk geochemistry ca al ph cation exchange capacity cec organic matter and soil texture in order to examine the factors controlling these variables a series of three chronosequences 120 ka of tropical soils on uplifted terraces along the pacific coast of costa rica were studied the three study locations differ mainly as a function of soil moisture and leaching with conditions ranging from 2700 mm yr mean annual precipitation map on the southern nicoya peninsula 4 month dry season to 3200 mm yr in the esterillos region 3 month dry season and 4250 mm yr on the osa peninsula no dry season analytical methods include x ray diffraction xrd transmission analytical electron microscopy tem aem inductively coupled plasma optical emission and mass spectrometry icp oes icp ms ammonium acetate extraction 1 m nh4oac ph 7 for cec and c n analysis soil weathering reactions and related decrease in cec occur three to four times faster in a sequence of inceptisol to oxisol soils in the wettest climate osa compared to the less moist esterillos area in the even drier monsoon climate soils nicoya this evolved low cec the age related evolution of tropical soils appears to be a predictable sequence in lowland tropical landscapes where periodic tectonism erosion or volcanism produces unweathered parent material at the land surface empirical data from this project enables the extrapolation of simple equations applicable to tropical volcanic arc landscapes where presence of uplifted marine terrace soils facilitates determination of soil age the two variables controlling soil composition can be combined into an effective age ageeff that takes into account soil age and weathering intensity factoring in map and wet dry months from climate data and equations are of the form e g ecec 18 1 ln ageeff 77 with r2 values of 0 75 to 0 87 greatest scatter occurs in the youngest soils given the apparent prevalence of this sequence and the systematic nature of its reaction progression these results could be useful for modeling tropical soils

validity of the isotopic thermometer in central antarctica limited impact of glacial precipitation seasonality and moisture origin the classical interpretation of water stable isotopes deuterium or oxygen 18 retrieved from ice cores into past local temperature relies on the use of the spatial isotope temperature slope as a surrogate of the temporal slope whereas this assumption has been challenged by independent methods in central greenland it is still considered as valid in central antarctica we use an atmospheric general circulation model gcm to study two parameters highlighted by previous studies as being among the most important with respect to this assumption we show that in the gcm between present day and last glacial maximum the change in precipitation seasonality and the cooling of the moisture sources have limited and opposite effects on the isotopic record of the antarctic local temperature this conclusion strengthens the validity of the classical interpretation of isotope records in central antarctica