simulations of two last glacial maximum ocean states two stable thermohaline circulation states were produced in simulations of the last glacial maximum lgm ocean both forced by the same prescribed atmosphere direct application of this atmosphere led to an equilibrium state with strong north atlantic deep water formation northern sinking state nss upon applying a weak freshwater flux anomaly to the north atlantic for a short time a state was entered with little north atlantic but significant southern ocean deep water formation southern sinking state sss a fully dynamic and thermodynamic iceberg trajectory model was developed and icebergs were seeded into both states distinctly different pathways were found particularly in the eastern atlantic where the sss icebergs tend to move south along the european coast while they move north in the nss while neither ocean state is claimed to be a definitive model for the lgm ocean paleoclimate data are more consistent with the characteristics of the nss

diatom productivity peak and increased circulation during latest quaternary alboran basin western mediterranean abstract diatoms were studied quantitatively in six latest quaternary 70 kyr b p to recent piston cores from the westernmost mediterranean the alboran basin and the atlantic region immediately to the west of the straits of gibraltar the atlantic cores completely lack diatoms in the alboran basin diatoms are common from late stage 3 27 5 kyr b p to termination ib 9 kyr b p and in recent core tops but are absent in the other latest quaternary intervals maximum accumulation of diatoms and highest abundance of species normally in sediments associated with increased productivity occurred during the latest quaternary deglaciation in the first phase of termination i 14 8 kyr b p in the modern alboran basin a region of high biological productivity occurs immediately east of the gibraltar straits this high productivity results from upwelling associated with the interaction between the atlantic inflow and the bottom topography near the spanish coast the upwelled nutrient rich waters are then advected to the east and southeast by the surficial anticyclonic gyral circulation late quaternary variations in diatom abundance are considered to reflect changes in this upwelling intensity with highest diatom abundances inferred to result from increased upwelling associated with an intensification of the anticyclonic gyral circulation highest inferred upwelling rates occurred during the first phase of latest quaternary deglaciation it is possible that an intensification of circulation within the mediterranean basin as a whole occurred from late stage 3 to mid termination i because widespread hiatus formation has been reported at this time in the straits of sicily due to an increase in the formation of intermediate waters diatoms were not preserved in other latest quaternary intervals due to insufficient productivity to counterbalance their dissolution

stable isotope anomalies in mediterranean pleistocene records oxygen and carbon isotope records of twelve mediterranean cores raised from west alboran sea to east off israel and of four atlantic cores raised from the western side of gibraltar and located respectively inside below and beyond the modern mediterranean outflow are compared to open ocean records of core 71 139c from the north atlantic and core v19 30 from the east pacific oxygen isotope stratigraphies can be established for deep mediterranean records and the major events of the last 150 ka are easily identifiable for instance the five substages of stage 5 or the 18 ka event stage 2 are identified but the 10 ka event younger dryas is only recorded by globigerina bulloides and benthic foraminifera suggesting that the cooling affected only winter sst 14c dates for the two terminations ia and ib of the last deglaciation which are recorded in sediment cores from areas with high sedimentation rates faro ridge alboran sea sicilian strait are in good agreement with the dates published for the same termination in atlantic cores an intermediate step however has been identified in some cores at 14 ka and divides termination ia into two phases oxygen isotope anomalies are recorded by the shallow water species globigerinoides ruber they correspond to 1 a higher amplitude glacial interglacial change in 18o values which exceeds that of the open ocean by 1 in the western basin and by 1 7 in the eastern basin 2 large isotopic depletions during the deposition of sapropel s1 s3 and s5 they are interpreted as the result of fresh water run off responsible for a strong dilution in the shallower layers of the east mediterranean waters the isotopic effect of this dilution averages 0 75 for sapropel s1 and 1 6 for sapropel s5 during the last glacial maximum the mediterranean still acted as a concentration basin and a gradient of 18o values similar to the modern one 0 75 existed from west to east in the deep waters apparently deep water temperatures were lower during the last glacial but the decrease did not exceed 4 c in the eastern basin major anomalies are also contained in the 13c records of g bulloides and benthic foraminifera the 13c records from surface intermediate and deep waters of the eastern basin and from intermediate and deep waters of the western basin are opposite to that of the open ocean during glacial time 13c values were higher in intermediate and deep waters of the whole mediterranean and also in surface water of the eastern basin at the same time the 13c gradient of surface to deep waters was low this gradient increased during the last deglaciation while 13c values of g bulloides and benthic foraminifera decreased this decrease interrupted at 10 ka may have been related to increased fresh water run off from the bordering contintents due to increased precipitation especially in the tropical belt the 13c depletion is clearly recorded in the levantine and deep water masses and can be traced westward in the mediterranean outflow oxygen and carbon isotope anomalies recorded simultaneously in the east mediterranean by the shallow water species globigerinoides ruber during sapropel deposition indicate that increased precipitation on the bordering continents and strong fresh water run off during the time of the last deglaciation may have caused a density stratification and deep stagnation in the eastern basin uncertainties arise from the fact that in the mixing model deglacial mediterranean waters are mixed with continental fresh waters the isotopic characteristics of which are not entirely understood although increased surface water production of biogenic material can not be excluded as a possible cause of 13c depletion it appears that the river discharge including the nile as well as black sea input are also plausible sources for the fresh water layering

the influence of changing orbital parameters and surface boundary conditions on climate simulations for the past 18 000 years abstract general circulation model experiments at 3000 year intervals for the past 18 000 years were made to estimate the magnitude timing and pattern of the climatic response to prescribed changes of orbital parameters date of perihelion axial tilt eccentricity and glacial age lower boundary conditions ice sheets land albedo sea ice and sea surface temperature the experiments used the community climate model ccm of the national center for atmospheric research ncar the response of monsoon circulations and tropical precipitation to the orbitally produced solar radiation changes was much larger than the response to changes of glacial age boundary conditions the continental interior of eurasia was 2 4 k warmer in summer and summer monsoon precipitation of north africa south asia was increased by 10 20 between 12 000 and 6000 yr bp before present when perihelion occurred during northern summer rather than in winter as now and the earth s axial tilt was larger than now southern hemisphe

an ocean general circulation model view of the glacial mediterranean thermohaline circulation reconstructions of the sea surface temperature and salinity of the mediterranean sea during the last glacial maximum lgm suggest that extremely cold winters occurred in the western basin and the aegean with highly saline conditions in the eastern basin it is shown here that forcing the lgm mediterranean sea with a representative paleoclimate model results in significantly less extreme salinity conditions than are suggested by existing reconstructions modeled sea surface salinities are at most 0 1 0 2 higher than today at the lgm rather than the previously suggested 2 3 modeled sea surface temperatures over the western basin however show similar changes to these reconstructions being 3 4 c colder than present day another major difference between the lgm and control simulations is the location and spreading of subsurface water the western basin suffers complete loss of stability in the lgm winter leading to this basin becoming the source for the lgm deep water of the eastern basin the ocean general circulation model results are shown to be qualitatively consistent with cooler drier climate along the northern coast of the mediterranean but not with higher surface salinity thus refining existing paleoclimate reconstructions in the mediterranean region

hydrological changes in the mediterranean sea over the last 30 000 years sea surface temperatures were reconstructed over the last 30 000 years from alkenone paleothermometry sst alk and planktonic foraminifera assemblages using the modern analog technique mat sst foram along two cores of the mediterranean sea md84 632 levantine basin and md04 2797 siculo tunisian strait oxygen isotope of planktonic foraminifera g bulloides for core md04 2797 and g ruber for core md84 632 were also determined sst alk in the levantine basin indicate colder values at the last glacial maximum lgm 14 c than earlier established from mat and a cooling amplitude of 6 7 c comparable to the central mediterranean sea climatic events such as the younger dryas yd and heinrich events 1 and 2 h1 and h2 were times of significant cooling in the two cores in the eastern basin values of local seawater oxygen isotope w indicate relatively saltier waters during the lgm and deglaciation than today with increasing w values higher salinity in the eastern basin and decreasing ones lower salinity in the central mediterranean sea during cold stadials the observed alterations of surface water properties t and w in the central and eastern mediterranean at the lgm are consistent with model experiments showing slightly lower evaporation in the mediterranean than today except for the eastern basin

northern levantine and adriatic quaternary planktic foraminifera reconstruction of paleoenvironmental gradients rohling e j jorissen f j vergnaud grazzini c and zachariasse w j 1993 northern levantine and adriatic quaternary planktic foraminifera reconstruction of paleoenvironmental gradients mar micropaleontol 21 191 218 a detailed study of the planktic foraminiferal records of three cores recovered near crete shows very consistent changes unfortunately the record of t87 2 13g our shallowest core is bioturbated too much for detailed comparisons but it can still be used to discuss the general trends the mutual record of the other two cores t87 2 20g and t87 2 27g extends back to about 125 000 yr b p principal components analyses performed on the combined records of t87 2 20g and t87 2 27g yield two axes that can be interpreted paleoecologically namely a temperature axis and an annual stability axis the latter is a measure of stratification within the euphoric layer in this study we consider t87 2 20g and t87 2 27g to be reference cores for the eastern mediterranean subsequently we interprete the faunal variation in two cores from the adriatic sea in 68 5 and in 68 9 containing records extending back to 15 000 and 18 000 yr b p in the context of these reference cores this is done by calculating scores of the adriatic records along the two relevant pca axes derived from the northern levantine records also cluster analyses of the adriatic and northern levantine records are compared on the average the adriatic sea appears to have been considerably colder than the region around crete during the past 18 000 years this temperature difference was largest during the pleniglacial and only small during the holocene we found no distinct expression of a younger dryas cooling event in the adriatic records neither on our pca axis nor in the oxygen isotope record this contradicts previous paleoclimatic reconstructions based mainly on paleobotanical evidence which suggests that the younger dryas event greatly influenced circum mediterranean areas as yet we have no ready explanation for this discrepancy low annual stability values dominate both the pleniglacial and the holocene intervals of the adriatic records this suggests that homothermal conditions were as prevalent in the adriatic euphoric layer at pleniglacial times as they are at present in the present day adriatic homothermal conditions are associated with deep convection and subsequent eastern mediterranean deep water emdw formation and therefore our data suggest that emdw formation was as effective at pleniglacial times as it is at present high annual stability values in the transitional interval from 12 700 to 9600 yr b p in the adriatic records are suggestive of low emdw formation rates at that time in combination with high productivity throughout the eastern mediterranean which has previously been inferred from the planktic foraminiferal record these low emdw formation rates may have preconditioned the eastern mediterranean for sapropel formation

sensitivity of mediterranean thermohaline circulation to gateway depth a model investigation 1 the neogene sedimentary record of the mediterranean sea holds evidence for changes in water properties and circulation these paleoceanographic changes have been attributed to changes in the flow through the ocean gateway between the mediterranean sea and the atlantic ocean we use an oceanic general circulation model to achieve quantitative physics based understanding of the effect of changes in the depth of the gateway such as may result from tectonic activity or variation in sea level to isolate these effects we use idealized basin geometry and impose simplified atmospheric forcing a reference experiment with present day sill depth demonstrates that the model simulates reasonably well the main features of the present day mediterranean thermohaline circulation as inferred from observations and previous numerical studies subsequently a series of sensitivity simulations is performed with different sill depths the model results show that mediterranean temperature salinity and thermohaline circulation depend strongly on sill depth as the sill depth decreases the upper overturning cell is quasi linearly reduced in strength while contrary to what one would expect the deep cell intensifies and does so in a nonlinear way we find that a shoaling of the sill depth induces a blocking effect on the outflow waters which creates a strong recirculation in the deep layers strengthening the deep cell nevertheless deep water formation is reduced and as a consequence the ventilation of the deep layers diminishes we identify three different circulation modes of the mediterranean thermohaline circulation depending on the sill depth shallow sill moderate sill and deep sill modes coupled with strong weak and negligible blocking effects respectively our results are consistent with the pre messinian paleoceanographic record of the mediterranean sea and may be useful to understanding the behavior of other land locked basins both extant and from the geological past

oxygen isotopic composition of the mediterranean sea since the last glacial maximum constraints from pore water analyses abstract interstitial waters recovered from ocean drilling program leg 161 site 976 in the western mediterranean sea are used in conjunction with a numerical model to constrain the 18o of seawater in the basin since the last glacial maximum including sapropel event 1 to resolve the oxygen isotopic composition of the deep mediterranean we use a model that couples fluid diffusion with advective transport thus producing a profile of seawater 18o variability that is unaffected by glacial interglacial variations in marine temperature comparing our reconstructed seawater 18o to recent determinations of 1 0 for the mean ocean change in glacial interglacial 18o due to the expansion of global ice volume we calculate an additional 0 2 increase in mediterranean 18o caused by local evaporative enrichment this estimate of 18o change due to salinity variability is smaller than previous studies have proposed and demonstrates that mediterranean records of foraminiferal calcite 18o from the last glacial period include a strong temperature component paleotemperatures determined in combination with a stacked record of foraminiferal calcite depict almost 9 c of regional cooling for the last glacial maximum model results suggest a decrease of 1 1 in seawater 18o relative to the modern value caused by increased freshwater input and reduced salinity accompanying the formation of the most recent sapropel the results additionally indicate the existence of isotopically light water circulating down to bottom water depths at least in the western mediterranean supporting the existence of an anti estuarine thermohaline circulation pattern during sapropel event 1

glacial holocene salinity changes in the mediterranean sea hydrographic and depositional effects oxygen isotope changes as recorded by pleistocene foraminifera from open ocean sediments are primarily a function of changes in the isotopic composition of the global seawater reservoir caused by ice volume changes with a secondary temperature component1 oxygen isotope records from marginal basins such as the gulf of mexico2 the mediterranean sea3 5 and the red sea6 also exhibit the global signal but are far more complicated owing to the strong overprint of local climate conditions in particular glacial interglacial changes in continental aridity and river runoff produce significant salinity changes in these semi enclosed basins using available oxygen isotope records we estimate that glacial 18 000 yr bp salinities in the eastern and western mediterranean sea were 2 7 and 1 2 higher respectively than at present these elevated glacial salinities played an important part in preconditioning the eastern mediterranean for the eventual accumulation of organic carbon rich sediments sapropels at the end of deglaciation

abrupt cold spells in the northwest mediterranean hitherto unknown abundance peaks of left coiling l c neogloboquadrina pachyderma from a gulf of lions piston core indicate that abrupt cold spells associated with atlantic heinrich events affected the mediterranean n pachyderma l c is typical of sub polar waters in the open ocean the southern edge of its glacial north atlantic bioprovince reached south portugal only trace abundances of n pachyderma l c are known from quaternary mediterranean sediments suggesting that no significant invasions occured via the strait of gibraltar the gulf of lions abundance peaks therefore seem to reflect area specific thriving of a normally rare but indigenous taxon in the western mediterranean through local favorable habitat development the general planktonic foraminiferal record suggests that the basic hydrographic regime in the gulf of lions with wintertime deep convective overturn was relatively stable over the past 60 kyr under these conditions high abundances of n pachyderma l c would essentially imply temperature reductions of the order of 5 8 relative to the present

spectral wave modeling in fringing reef environments abstract this study examines the implementation and validity of phase averaged spectral models in describing wave transformation over fringing reefs the wave breaking mechanism over the abrupt reef crest dissipation due to bottom friction and nonlinear energy transfer over the reef flat set the problem apart from general applications in non tropical settings the simulating wave nearshore swan model which is widely used in coastal engineering applications has embedded parameterizations of these surf zone processes for examination in addition we extend the model to include a recently implemented bottom friction source term for tropical reefs comparisons of model predictions with laboratory and field observations over fringing reefs identify promising wave breaking and bottom friction parameterizations for calibration the calibrated parameterizations enable swan to reproduce the observed wave height and setup and extend the applicability of spectral models to fringing reef environments swan however lacks the parameterization to describe the nonlinear energy transfer toward the infra gravity band that was observed in the laboratory and field studies

the seasonal characteristics of the circulation in the north mediterranean basin and their relationship with the atmospheric climatic conditions the greater heat losses sustained by the ligurian provencal basin in winter appear to be the major factor leading to the periodic intrusions of the warmer tyrrhenian water from the east this is the main conclusion of a 3 year oceanographic investigation carried out in the eastern ligurian provencal basin in order to monitor the long term characteristics of its exchanges with the tyrrhenian sea the analysis of the whole data set collected in this period shows that two currents converge north of corsica after having flowed along the northwestern side of corsica the west corsican current and through the corsican channel the tyrrhenian current while the former does maintain nearly steady properties year round the latter crosses the strait only during the coldest season thus showing a clear seasonal trend that begins again every year the comparison with the meteorological parameters of the ligurian provencal basin indicates that the winter intrusions of the tyrrhenian current are tightly associated with the heat and water losses through the rise induced in the upper basin density in addition to reintegrating the heat lost to the atmosphere the tyrrhenian flow might also restore the volume of the basin upper layer involved in the deep water formation processes this enables us to infer that a unique circulation pattern mostly driven by atmospheric climatic conditions involves the northern part of the western mediterranean sea

aridity of the mediterranean sea at the last glacial maximum a reinterpretation of the δ18o record paleoclimate data show conflicting evidence for aridity in the mediterranean basin at the last glacial maximum lgm two recent modeling studies of the lgm mediterranean using water balance biome and ocean general circulation models respectively suggest that evaporation over the basin was reduced at the lgm compared with today in apparent conflict with these results is the strongly enhanced 18o signature of the lgm mediterranean surface waters particularly in the eastern basin which has been ascribed to a much higher salinity in an alternative interpretation presented here a box model of the balance between paleoclimate model evaporation and rainfall and paleoceanographic model advective terms shows that the observed lgm 18o signature can be reproduced without the need for an enhanced salinity with advection playing the dominant role in the 18o budget the box model also shows that the 18o data alone are insufficient to determine the type of exchange between the eastern and western basins the results emphasize that regional paleoceanographic water balances should consider all relevant processes and not just the evaporative flux

impact of climatic changes on the benthic foraminiferal fauna in the ionian sea during the last 330 0000 years to reconstruct paleoceanographic changes in the eastern mediterranean during the last 330 000 years we studied benthic foraminifera in a piston core from the ionian sea the fauna exhibits large fluctuations in foraminiferal number diversity and species composition interglacials are characterized by low foraminiferal number and diversity indicating oligotrophic conditions directly below or above interglacial sapropels increased numbers of low oxygen tolerant species indicate a strong reduction of deep water circulation glacials are characterized by increased foraminiferal number and diversity and faunas that are dominated by shallow infaunal species indicating mesotrophic conditions around glacial sapropel s6 very high foraminiferal numbers and the dominance of shallow and deep infaunal species suggest enhanced organic matter fluxes these faunal results provide information about changes in the african and north atlantic climate systems monsoon and westerlies controlling the humidity and wind stress in the mediterranean region

vegetation and climate of anatolia and adjacent regions during the last glacial period abstract reinterpretation of vegetation and climatic conditions of anatolia and neighboring regions during last glacial 30 15 cal ka bp have been done using a non quantitative biomization approach based on previously published plant functional types the results suggest that the climate was cold and humid before 25 cal ka bp and also during the period 23 19 cal ka bp except east anatolia forest vegetation was 80 90 of the land cover in the northwestern anatolia and black sea coast and 50 60 along the mediterranean coast at the same period during heinrich event 2 from 25 to 23 cal ka bp steppe vegetation dominated the anatolian region due to the sudden change to very cold and arid conditions approximately between 18 and 16 cal ka bp in the late glacial during heinrich event 1 a brief interval of cold and arid conditions resulted in weaker steppe vegetation over some part of anatolia around at 15 cal ka bp suitable climatic conditions for forest vegetation prevailed across a great part of anatolia except for eastern anatolia and western iran which are highlands

depth limited design wave heights in very flat regions abstract engineers working on the flat tops of offshore coral reefs or offshore banks require design criteria for depth limited wave heights over horizontal beds particularly in regions leeward of the bank or reef edge surf zone this paper presents convincing evidence of the fact that in engineering practice both in the laboratory and in the field the value of 0 55 is the largest wave height to water depth ratio realizable for stable shallow water oscillatory waves propagating in water of constant depth horizontal bed this value is much lower than that often used in engineering practice namely a value of about 0 8 which is historically based on the theoretical considerations and laboratory experiments associated with solitary waves this result based on a review of laboratory data and the original results of a major field experiment undertaken on the great barrier reef of australia leads to a significant reduction in design wave forces design crest levels and wave induced scour velocities at the bed

palaeoceanographic record of the last deglaciation in the strait of sicily abstract the palaeoceanographic evolution of the levantine waters during the last deglacial time is investigated using the sedimentary record of a deep sea core cs 70 5 from the linosa basin 35 44 4 n 13 11 0 e 1486 m water depth radiocarbon dating and oxygen isotope stratigraphy based on 18 o changes in globigerina bulloides allow us to recognize and to date the different steps of the deglaciation these steps are synchronous with those reported in the north atlantic but correspond to a 18 o decrease of higher amplitude than in the alboran sea or in the north atlantic ocean major faunal events permit the establishment of a local biozonation which differs from those reported either for the alboran sea or the eastern mediterranean basin major breaks in the faunal assemblages occurred during termination i a within the first step of the deglaciation around 14 kyr b p and near 10 6 kyr b p within the younger dryas the onset of the last deglaciation induced important changes in the characteristics of the levantine and atlantic water masses which occupied the strait of sicily the 13 c records of globigerina bulloides and cibicidoides pachyderma indicate that the modifications observed in the assemblages of deep faunas are controlled by the oxygenation of the water column 13 c records of globigerina bulloides are similar throughout the west mediterranean as well as in sediments located below the present mediterranean outflow the distributional pattern as well as its 13 c record suggest that this species could be a good recorder of the upper levantine waters and more precisely of the mixing layer of the overlying atlantic waters with the levantine ones major influxes of atlantic waters during terminations i a and i b could have slowed down the vertical mixing of the different water layers present in the strait of sicily and caused a decrease in the oxygenation of the water column during termination i b the effect of atlantic influxes was reinforced by the occurrence of a low salinity layer in the eastern basin which led to the stagnation of the deep waters the two episodes of decreased oxygenation in the levantine waters also favored the precipitation of inorganic magnesium calcite

the western mediterranean during the last glacial attacking a no analog problem abstract assemblages of planktic foraminifera from the western mediterranean during the last world ice volume maximum 18 000 yrs b p are presented for two rapid sedimentation rate deep sea cores one from the northern and one from the western part of the basin the locations permit monitoring of hydrography in the alboran sea where exchange occurs with the atlantic and in the northern balearic sea where the warm mediterranean out flow to the world ocean is generated by a unique vertical mixing process this latter makes a significant contribution to the heat budget of the global deep sea thus the assemblages reflect western mediterranean oceanography and interaction with the atlantic during the last ice age quantitative empirical paleo oceanographic interpretation of the faunas is not possible because they occur in relative abundances not seen in the north atlantic or mediterranean of today however some more general deductions of paleohydrography are possible the faunas indicate that the western mediterranean was considerably colder 18 000 yrs b p and highly seasonal large annual thermal contrast reflecting the seas nearly land locked position climate surrounding the basin appears to have been quite variable over periods of less than 500 years the faunas also indicate that interchange between the eastern and western mediterranean seas was much altered during the glacial and that the character of the water returned to the atlantic from the mediterranean was quite different probably colder from that of the present the deep world ocean would then have been lacking a significant heat source 18 000 yrs b p

height limits in top down and bottom up wave environments this paper isolates two environments or processes in which maximum stable wave heights can be attained in water of constant depth in top down environments the maximum stable wave height compatible with the depth is approached from above while in bottom up environments it is approached from below the analyses of field data from these two environments are compared in water of constant depth the individual waves in naturally occurring bottom up wave trains are shown to conform to the same upper height limit criteria as naturally occurring top down wave trains that limit being the same function developed from monochromatic laboratory waves however important differences are found in the shallow and transitional wave content of the wave populations generated by the two different processes

breaking probabilities for dominant surface waves on water of finite constant depth this paper extends our previous study of the breaking probability of dominant deep water gravity surface waves into the finite water depth environment it reports a unified behavior of the mean breaking statistics once the effects of finite water depth are taken into account the shallow water wave data that form the basis of this study were acquired at a field experiment site at lake george new south wales australia the breaking events were detected through visual observation of videotaped records of the wave field in combination with acoustic signatures of the breaking waves from a collocated hydrophone following banner et al 2000 we argue that when constant finite depth bottom influence is operative nonlinear hydrodynamical effects associated with energy and momentum fluxes within deforming wave groups remain the primary determinant of breaking onset this underpins our proposed finite depth water parameterization for the environmental dependence of dominant wave breaking probability given by the average number of breakers passing a fixed point per dominant wave period the additional influence of bottom interaction with the wind drift current shear and wind forcing are also included in our finite constant depth formulation this is a natural extension of our recently proposed deep water dependence and reduces to it as the significant wave height becomes much smaller than the water depth in common with the deep water case we propose that there exists a threshold of the significant peak steepness below which negligible dominant wave breaking occurs the available data show encouraging agreement with our proposed dependence with a correlation coefficient approaching 0 9

late quaternary changes in mediterranean intermediate water density and formation rate three recently acquired eastern mediterranean cores containing late quaternary sediments display a marked faunal contrast between the holocene and older sapropels it is suggested that the absence of neogloboquadrinids in the holocene sapropel and their abundance in older sapropels reflect differences in food availability related to the extent of development of a deep chlorophyll maximum layer dcm and the intensity of new primary production associated with this layer the depth of such a layer which consists of phytoplankton with a characteristic taxonomic composition is determined by the vertical hydrodynamical structure during deposition of the older sapropels the pycnocline was apparently positioned well above the base of the euphotic layer a situation that favors a pronounced dcm and an associated relatively high rate of new production shallowing of the pycnocline implies a relatively low density of the mediterranean intermediate water miw on the other hand during deposition of the holocene sapropel the pycnocline had apparently vanished due to termination of miw formation

modeling the late quaternary indian ocean circulation an ocean general circulation model ogcm of the indian ocean is forced by paleoclimate simulations for five time slices over the last 126 000 years using an annual period sinusoidal fit to the perpetual january and july paleoclimatic model forcing the ogcm produces seasonal cycles in velocity fields both vertical and horizontal and temperature salinity fields at these five times the simulations indicate that the southern hemisphere upper ocean circulation of the indian ocean is essentially invariant to climatic fluctuation on this time scale they also suggest that the low insolation 18 000 years b p northern hemisphere upper ocean summer circulation was very much weaker compared to high insolation periods such as 9000 years b p and 126 000 years b p by perhaps an order of magnitude by contrast the simulated low insolation winter northern hemisphere upper ocean circulation was substantially stronger than during high insolation periods equatorial upwelling as simulated is shown to be a mainly boreal summer event reduced by an order of magnitude during low insolation conditions a similar reduction in upwelling is seen along the arabian coast but a less severe decrease along the somalian coast the model simulation of february and august sea surface temperature at 18 000 years b p the height of the last glaciation is generally within 1 2 c of paleoclimate reconstructions the effect of lower glacial sea level on the circulation is shown to be only local

the origin and characteristics of the algerian current satellite and ship data collected between may 1 and 22 1986 show that the algerian current originates in the almeria oran front and remains within 30 km of the algerian coast for over 300 km between oran and algiers the differences between the water masses of the current and the resident regional waters are clearly observed in the chlorophyll concentrations and optical characteristics thus permitting the resulting patterns to be used as tracers of the circulation during this field period the algerian current begins as an extension of the almeria oran front which is found at the western periphery of the eastern alboran gyre this major oceanographic salinity front s 1 km delineates the boundary of the algerian current which has average surface velocities of 40 cm s and maximum speeds reaching 80 cm s the current which has a volume transport between 0 4 and 0 5 sv is confined to the upper 150 m and is in geostrophic balance a sequence of coastal zone color scanner czcs and advanced very high resolution radiometer avhrr satellite imagery showing the rapidly evolving surface circulation features is augmented with in situ ship data of current and water mass characteristics rapid undulations and frontal movements of the current were observed during the study period however the flow remained unbroken between 1 and 3 e current instability increased eastward as the undulations were sharper and the current appeared to depart from the coast near algiers

modeling depth induced wave breaking over complex coastal bathymetries abstract the correct representation of depth induced wave breaking is important for understanding coastal morphology and for design and management in the coastal zone although numerous studies have demonstrated the applicability of a constant scaling of the battjes and janssen 1978 dissipation model for depth induced breaking recent studies have shown its inability to sufficiently reproduce wave dissipation over complex field cases in the present study we contrast the application of such a constant scaling to two alternative wave breaking parameterizations with a variable scaling based on either the wave nonlinearity the parameterization or on both bottom slope and normalized wavelength supplemented with wave directionality the kd parameterization we consider three field data sets characteristic of a simple beach bar profile a bay partially protected by a shoal and a complex intertidal region we demonstrate that in these cases the kd parameterization provides a better alternative to the use of a constant scaling or the parameterization to illustrate the operational consequences we up scale the conditions over the case of the intertidal region to correspond to design conditions for the dutch coast storm conditions with a 4000 year return period under these extreme conditions for locally generated waves both the kd and parameterizations predict qualitatively similar increased significant wave heights but the kd parameterization increased the waves twice as much as the parameterization under other conditions when non locally generated waves swell dissipates over a gently sloping bottom the kd parameterization predicts lower significant wave heights compared to either the constant scaling or parameterization

late glacial to recent deep sea benthic foraminifera from the northeastern atlantic cadiz gulf and western mediterranean alboran sea paleooceanographic results abstract deep sea benthic foraminifera of the region of water exchange between the mediterranean and the atlantic ocean at the gibraltar strait show significant water mass relationships for the past 18 000 years cores used in this benthic foraminifera analysis were selected according to the context of the distribution of various deep bottom water masses on each side of the gibraltar strait 1 1 on the atlantic side of the strait two cores ks 8228 ks 8229 are located in the present day nadw and one kc 8221 in the upper part of the present mediterranean outflow water 2 2 on the mediterranean side of gibraltar two cores kc 8241 su 8107 are located in the deep water mass and one ks 8230 in the intermediate water mass in the two deep basins 1500 2800 m depth in the gulf of cadiz 1200 1300 m depth in the alboran sea the paleooceanographic changes appear to be in an opposite way for the past 18 000 years the alboran basin shows a paleooceanographic evolution from a well oxygenated nutrient rich environment at about 18 000 yr b p to a nutrient poor oxygen depleted environment from 13 000 to the present time moreover for the time span synchronous with the well known development of sapropels in the eastern mediterranean basins between 10 000 and 7000 yr b p the faunal assemblage shows most unusual characteristics implying drastic environmental conditions conversely in the gulf of cadiz the environment pass as from a biotope occupied by an oxygen depleted nutrient poor water mass at about 18 000 years b p to a biotope occupied by nadw since the younger dryas this agrees with previous data obtained in the northeastern atlantic ocean caralp 1987 in the epibathyal zones 550 800 m depth on both sides of the gibraltar strait paleohydrographic changes do not seem so important according to the present and very late holocene assemblages which are similar on both sides of the strait with a strong east west flow two other stratigraphic episodes have shown the same conditions of water exchanges the end of the isotopic stage 2 and the younger dryas conversely during the last glacial maximum the bolling allerod and the lower holocene westward water fluxes were probably lower at no time the hypothesis of a reversal or a stop in the east west exchanges between mediterranean and atlantic ocean may be justified

modeling the water masses of the atlantic ocean at the last glacial maximum 1 we produced gridded monthly sea surface boundary conditions for the atlantic ocean at the last glacial maximum lgm based on the sea surface temperature reconstruction of the glamap project we used an ocean general circulation model ogcm subject to these sea surface boundary conditions and a corresponding wind stress field from an atmospheric general circulation model to study the differences in the distribution of the main water masses between the lgm and the present our global ogcm is characterized by high vertical resolution low vertical diffusion and isopycnal mixing and hence allows for a realistic representation of the hydrology and circulation of the modern atlantic ocean according to a series of lgm experiments with an increasing sea surface salinity anomaly in the weddell sea the ventilated thermocline was colder than today by 2 3 c in the north atlantic ocean and in the experiment with the largest anomaly 1 0 beyond the global anomaly by 4 5 c in the south atlantic ocean its depth was reduced by 50 m on average most notably in the tropics in the north atlantic ocean the outcrop locations of the thermocline isopycnal surfaces migrated southward by 5 10 and the ventilation increased in the south atlantic ocean the mixed layer and thermocline water masses were dominated by cold water originating from drake passage and the import of warm water from the indian ocean was reduced to about 4 sv or 40 of its modern value antarctic intermediate water was colder by 3 4 c and could be traced as far as 10 n the meridional overturning rates of north atlantic deep water nadw and antarctic bottom water aabw in the atlantic ocean were similar to those of the present day experiment 9 10 sv and 4 sv respectively however nadw cooled by 2 5 c and aabw by 1 c aabw was near the freezing point of seawater at the surface and the saltiest water mass in the atlantic ocean even saltier than nadw we show that the differences between the lgm and the present day experiments can be traced back to the changes in the subpolar and interhemispheric sea surface density gradients

modeling the paleocirculation of the mediterranean the last glacial maximum and the holocene with emphasis on the formation of sapropel s 1 an ocean general circulation model is used to simulate the thermohaline circulation in the mediterranean sea during the last glacial maximum and the holocene when the sapropel s1 was deposited the model is forced by prescribed surface temperatures and salinities where present day values lead to very realistic surface buoyancy fluxes different paleoreconstructions for the surface salinity and temperature distributions during these periods are tested in both periods under all reconstructions antiestuarine flow is maintained at gibraltar and sicily the holocene circulation has fresh intermediate water produced in the adriatic and an upward salt flux from the old waters below help maintain its outflow at sicily the depth of ventilation around the basin is broadly consistent with the shallowest sapropel layers observed shoaling of the eastern pycnocline occurs in all experiments in both periods possibly indicating enhanced productivity although the reasons for this are different in each case

mediterranean outflow mixing and dynamics the mediterranean sea produces a salty dense outflow that is strongly modified by entrainment as it first begins to descend the continental slope in the eastern gulf of cadiz the current accelerates to 1 3 meters per second which raises the internal froude number above 1 and is intensely turbulent through its full thickness the outflow loses about half of its density anomaly and roughly doubles its volume transport as it entrains less saline north atlantic central water within 100 kilometers downstream the current is turned by the coriolis force until it flows nearly parallel to topography in a damped geostrophic balance the mixed mediterranean outflow continues westward slowly descending the continental slope until it becomes neutrally buoyant in the thermocline where it becomes an important water mass

sub millennial scale climatic oscillations in the central adriatic during the lateglacial palaeoceanographic implications abstract a multi proxy study of a sedimentary core obtained from the central adriatic basin provides evidence of short term events of palaeoceanographic variability during the last glacial lateglacial period grip event stages gi 1 and gs 1 comparison of the adriatic results with other mediterranean records reveals a common sequence of changes in palaeoceanographic conditions variations in foraminiferal assemblage data and in stable isotopic compositions indicate two short term cold oscillations which interrupted an overall cooling trend that commenced at the beginning of the greenland gi 1 episode bolling allerod episode these cold events considered to be contemporaneous with gi 1b and gi d of the grip ice core record are indicated by distinctive foraminiferal assemblages which reflect episodes of high productivity under relatively restricted water circulation with in particular reduced vertical mixing during winter differences in the foraminiferal assemblages indicate that the younger of the two cold spells is characterized by reduced ventilation of bottom waters our results combined with published data from neighbouring marine basins suggest a widespread reduction in deep water formation in the central mediterranean which commenced during the gi 1b episode and reached its maximum effect during the onset of the gs 1 younger dryas episode moreover three intervals with reduced vertical mixing correspond to the two cold spells during gi 1 and the lower phase of the gs 1 episode and show close similarities with the palaeoceanographic changes reported for the north atlantic this similarity indicates that the mediterranean and north atlantic may have been responding more or less synchronously to common forcing mechanisms

benthic isotope evidence for changes of the mediterranean outflow during the late quaternary a suit of sediment cores close to and south of the strait of gibraltar 12 36 n 500 2800 m water depth were analyzed for stable isotopes in epibenthic foraminifers cibicidoides wuellerstorfi and planulina ariminensis during peak glacial times the data exhibit higher 13c values of up to 1 6 at intermediate depths near the strait of gibraltar 36 n the values decrease to the south as evidenced by our data but also to the north as revealed by data of intermediate depth cores north of 38 n in duplessy et al 1987 thus the distribution pattern of 13c provides crucial evidence for an increased influence of nutrient depleted mediterranean outflow water mow on the glacial northeast atlantic hydrography during oxygen isotope terminations i and ii the meridional carbon isotope gradient indicates a significantly decreased but still active mow as deduced from the 18o fluctuations the temperatures of the mow in the atlantic were lower during glacial times by as much as 5 c during glacial times and during termination i the maximum 13c values of the mow correlate with minimum values of the north atlantic deep water nadw and vice versa this inverse response to climatic change of the carbon isotope signals of both water masses indicates that the supply of saline mow to the north atlantic may be less important for the formation of nadw than previously assumed

palaeoceanography of the last deglaciation in the alboran sea western mediterranean stable isotopes and planktonic foraminiferal records abstract oxygen isotope changes of the foraminiferal species globigerina bulloides and uvigerina peregrina eleven radiocarbon dates on the sediment fraction above 50 m and 13 biostratigraphical events allow us to correlate and to date the sediment record of the last climatic cycle in four cores from the alboran sea nine ecozones are recognized which differ from those previously established for atlantic sediments cored immediately west of gibraltar these ecozones can be grouped into two broad phases from the last glacial maximum up to near 9 500 yr b p cold north atlantic microfaunas are the major component of the assemblages during this interval dominant species replace each other according to the varying temperature and density stratification of the water masses from 9 500 yr b p up to the present time subtropical forms from the central atlantic dominate the northern atlantic forms an abrupt increase in the percentages of g inflata occurred near 7 000 b p this event was diachronous within the mediterranean during the last glacial g inflata was endemic inside the mediterranean and its abrupt increase near the end of the deglaciation did not result from replenishment from the atlantic between 4 000 and 5 000 yr b p percentages of g bulloides also increased abruptly warming conditions associated with the onset of a seasonal thermal stratification and a contrasting winter vertical convection are strongly suggested

use of an ablatometer to measure short term ablation of exposed ground ice an instrument ablatometer was developed to measure rates of ablation of exposed ground ice when the ablatometer is mounted on a melting ice face and linked to a portable micrologger a continuous record of short term ablation is obtained the ablatometer was tested on the headwall of an active ground ice slump located in southwest banks island northwest territories in general it performed satisfactorily with little or no instrument induced melt of the ice data for sunny days showed a strong diurnal rhythm of ground ice ablation and considerable microscale spatial variability rates of ablation and their spatial variation were lower on cloudy days illustrating the importance of solar insolation in inducing melt measurements beneath a debris cover following active layer collapse suggest that ablation soon ceases and does not recommence until after the debris is removed by mud flow as a result of the high degree of spatial variability in energy inputs and consequently in ablation rates results from

luminescence chronology of late pleistocene raised beaches in southern italy new data of relative sea level changes abstract littoral sediments forming terraces along the crotone peninsula coast southern italian have been investigated using sedimentological analysis and luminescence dating techniques and adopting assessments from previous work on fossil assemblages all sediment layers analysed were deposited in the nearshore environment between 20 m below and few metres above sea level during the falling sea level of a temperate warm climate interval the restoration of almost identical environmental conditions occurred in oxygen isotope substages 5e and 5a and in oxygen isotope stage 3 limits given by luminescence physics prevented accurate dating of the uppermost lying terrace former crotonian stage terrace and the presence of a substage 5c terrace is masked by the lack of suitable material for dating constraints on the positions of relative sea level from the reliable data set show that the sea level fell from 2 m during substage 5e to 29 m during substage 5a and then rose to 15 m during stage 3 observations for oxygen isotope stage 3 sea level at the crotone peninsula coast are inconsistent with those at the huon peninsula new guinea and in the western pacific the disagreement highlights the lack of knowledge concerning mediterranean thermohaline circulations and sea water exchanges between the atlantic and mediterranean seas during glacial cycles

abrupt climate change sea surface salinity and paleoproductivity in the western mediterranean sea gulf of lion during the last 28 kyr abstract the planktonic foraminiferal record of core md99 2346 gulf of lion shows a decrease of sea surface temperature sst at the time of heinrich event h2 24 23 5 cal kyr bp younger dryas and during the early to middle holocene these events were associated with a decrease of surface water salinity the salinity lowering events were similar and synchronous to those recorded in the north atlantic ocean during h1 h2 and the younger dryas they can be explained by a decrease in the salinity of the atlantic surface water entering the mediterranean through the strait of gibraltar this result indicates that the mediterranean sea remained a concentration basin and that its freshwater budget was not significantly different from the modern conditions at the time of these low salinity events higher abundances of the benthic foraminifer cibicidoides pachydermus at the time of heinrich events h2 and h1 may result from a seasonal and more pulsed supply of labile organic matter a high abundance of intermediate and deep infaunal taxa globobulimina spp during the warm bolling allerod period is interpreted as a result of an increased lateral advection of organic matter to the deeper environments of the gulf of lion surface water productivity as reflected by the organic flux to the benthic ecosystem reaches a maximum during the cold younger dryas period it is possible that cold conditions at the time of the younger dryas have allowed an enhanced vertical mixing and deep water cascading in the gulf of lion this may have resulted in an increase of primary and export production this putative intensification of deep water cascading would have occurred after the sustained rise of the global sea level from 16 to 12 5 cal kyr bp the deglacial sea level rise may also have played an important role in favouring the downslope movement of dense shelf water enriched in organic matter originating from the early rhone delta complex the conditions during the holocene were characterized by a low surface productivity and oligotrophic environment similar to the modern situation

wave loads on rubble mound breakwater crown walls abstract crown walls are primarily built to reduce wave overtopping of mound breakwaters several methods have been proposed to calculate wave loads on the crown wall e g iribarren and nogales iribarren r nogales c 1964 obras maritimas dossat ed madrid 376 pp jensen jensen o j 1984 a monograph on rubble mound breakwaters danish hydraulic institute and gunbak and gokce gunbak a r gokce t 1984 wave screen stability of rubble mound breakwaters international symposium of maritime structures in the mediterranean sea athens greece pp 2 99 2 112 in this paper a new method based on those previous results and on further experimental work using monochromatic waves is presented the application of the new method requires waves breaking on the armour layer i e only broken waves will reach the crown wall the method is extended to irregular waves via the hypothesis of equivalence introduced by saville saville t 1962 an approximation of the wave run up frequency distribution proc 8th international conference on coastal engineering mexico city and is applied to the crown walls of gijon and bilbao breakwaters in spain the comparison of the probability force distributions obtained by the present method to that measured by burcharth et al burcharth h f frigaard p berenguer j m gonzalez b uzcanga j villanueva j 1995 design of the ciervana breakwater bilbao in t telford ed proc 4th coastal structures and breakwaters chap 3 institution of civil engineers and jensen 1984 is relatively good

late quaternary climatic change in france estimated from multivariate pollen time series abstract in regions like southern france where usual analytical techniques are unsatisfactory due to the heavy influence of human activity and the existence of a complex climate the quantitative reconstruction of climate from pollen is particularly difficult that is why an original method has been performed the first step of the method based on best analogs estimation and multiple regression is to calculate a relationship between climate monthly temperature and precipitation and modern pollen spectra for data from 182 sites the result is called the analog climate the second step of the method an original combination of canonical correlation and principal components analyses extracts the common information from several fossil pollen sequences to produce a so called paleobioclimate this step removes the effects of local differences in the vegetation among nearby sites and also reduces the effects of human disturbance in the third step the signals obtained from the first two steps are merged by kalman filter into a final reconstruction where the noise is reduced by around 37 the results presented with a 95 confidence level suggest that the pleni wurm was 7 to 13 c colder than present and had 20 to 60 less precipitation than today this large confidence takes into account the climatic diversity of the region at 13 000 yr b p the climate reached the modern level of precipitation but the temperature was just less than present the subsequent decrease of precipitation is less important than that of temperature this fact may explain the advance of alpine glaciers during the younger dryas preboreal warming was abrupt 3 to 4 c per 500 yr and precipitation increased more slowly

terrestrial conditions at the last glacial maximum and climap sea surface temperature estimates are they consistent climap 1981 seasonal reconstruction of the earth s surface at the last glacial maximum geological society of america map and chart series mc 36 boundary conditions were used as inputs to the giss general circulation model and the last glacial maximum lgm climate was simulated for six model years the simulation was compared with snow line depression and pollen inferred temperature data at low latitudes specifically for hawaii colombia east africa and new guinea the model does not produced as much cooling at low latitudes as is implied by the terrestrial evidence an alternative experiment in which the climap sea surface temperatures were uniformly lowered by 2 c produces a better fit to the land data although in hawaii model temperatures are still too warm the relatively warm climap tropical sea surface temperatures also provide for only a slight decrease in the hydrologic cycle in the model in contrast to both evidence of lgm tropical aridity and the results of the experiment with colder ocean temperatures with the climap sea surface temperatures the lgm global annual mean surface air temperature is 3 6 c colder than at present if the ocean temperatures were allowed to cool in conformity with the model s radiation balance the lgm simulation would be 5 6 c colder than today and in better agreement with the tropical land evidence

temperature and salinity variations of mediterranean sea surface waters over the last 16 000 years from records of planktonic stable oxygen isotopes and alkenone unsaturation ratios alkenone unsaturation ratios and planktonic d18o records from sediment cores of the alboran ionian and levantine basins in the mediterranean sea show pronounced variations in paleo temperatures and salinities of surface waters over the last 16 000 years average sea surface temperatures ssts are low during the last glacial averages prior to 13 000 years 11 15 c vary rapidly at the beginning of the holocene and increase to 17 18 ca t all sites during s1 formation dated between 9500 and 6600 calendar years the modern temperature gradient 2 3 c between the mediterranean sub basins is maintained during formation of sapropel s1 in the eastern mediterranean sea after s1 ssts have remained uniform in the alboran sea at 18 c and have fluctuated around 20 c in the ionian and levantine basin sites the d18o of planktonic foraminifer calcite decreases by 2 from the late glacial to s1 sediments in the ionian basin and by 2 8 in the levantine basin in the alboran sea the decrease is 1 7 of the 2 8 decrease in the levantine basin the evect of global ice volume accounts for a maximum of 1 05 and the temperature increase explains only a maximum of 1 3 the remainder is attributed to salinity changes we use the temperature and salinity estimates to calculate seawater density changes they indicate that a reversal of water mass circulation is not a likely explanation for increased carbon burial during s1 time instead it appears that intermediate and deep water formation may have shifted to the ionian sea approximately 2000 years before onset of s1 deposition because surface waters were as cold but saltier than surface water in the levantine basin during the younger dryas sapropel s1 began to form at the same time when a significant density decrease also occurred in the ionian sea 2000 elsevier science b v all rights reserved

numerical simulation of nearshore circulation on field topography under random wave environment abstract in order to investigate surf zone hydrodynamics through two dimensional numerical simulations of nearshore circulation under random wave environment a nearshore circulation model shorecirc and a random wave model swan were combined and utilized using this combined model a numerical simulation of the october 2 1997 sandyduck field experiment was performed for this simulation field topography and an input offshore spectrum were constructed using observed data sets synchronized with the experiment the wave breaking model in swan was modified by using breaker parameters varied according to bottom slope the simulation results were compared with the experimental data which revealed a well developed longshore current as well as with results using other combinations which were shorecirc and its original monochromatic wave driver and shorecirc and the default of swan the results from the novel combined model agreed well with the experimental data the results of the present simulation also indicate that alongshore field topography influences shear fluctuation of longshore currents

interbasin exchange of bottom water in ocean general circulation models abstract the abyssal part of the thermohaline circulation can pass through narrow channels between ocean basins which can potentially be resolved by high resolution ocean models such as the fine resolution antarctic model however in the fram as in other models topographic smoothing filled in these channels severely weakening the abyssal circulation and altering the baroclinic structure at shallower depths the authors describe a model covering the vema channel region of the south atlantic which was nested in the fram with a straight single gridpoint channel joining the argentine and brazil basins initialization with the fram results produced a weak northward flow through the channel which decayed after 6 months spinning up the model toward the fram results produced southward flow whereas spinning up toward the levitus climatological fields of temperature and salinity produced northward flow of similar strength to observations an experiment with higher cross channel resolution gave a similar

application of a degree day model to reconstruct pleistocene glacial climates there is empirical evidence of a nonlinear relation between annual precipitation or accumulation and summer mean temperature at the equilibrium line altitude ela on glaciers around the world the degree day model gives a similar relation between accumulation and summer temperature although instead of a single universal curve there is a family of curves depending upon the annual temperature range furthermore the degree day model also gives nonlinear relations between accumulation and annual mean temperature thus estimations of accumulation can be made from both summer and annual temperatures at the ela of former reconstructed glaciers such as those in greece this is particularly useful since these climatic variables have major implications for biological proxies such as vegetation history indicated in the pollen record and for periglacial proxies such as permafrost distributions indicated in the geomorphological record the close relationship between glaciers and climate provides one of the most precise methods for reconstructing former climates and offers considerable potential for resolving our understanding of pleistocene cold stage climates

paleoclimatic tracers an investigation using an atmospheric general circulation model under ice age conditions 2 water isotopes the linear relationship observed between the water isotopic contents of precipitation and surface air temperatures leads to the use of the water isotopes h218o and hdo in paleoclimatology applied to the measurements of the isotopic content of paleowaters like groundwaters and deep ice cores this relationship is used to infer paleotemperatures however this interpretation of paleo isotopic contents is only valid if the isotope temperature relationship is not affected by climate change to address this problem we have developed a water isotope modeling inside an atmospheric general circulation model agcm and performed simulations of both the present day and last glacial maximum lgm climatic conditions agcms are indeed the only appropriate tools able to account the whole complexity of the atmospheric circulation for the present day climate preliminary results for january were presented by joussaume et al 1984 and are complemented by new simulations performed for both february and august climatic conditions with a higher resolution version of the model model results are well corroborated by observations they also exhibit some effects of the atmospheric circulation on the isotopic fields for the simulated lgm climate the model results compare well with paleoclimatic data of water isotopic contents except for a higher than observed spatial variability the overall patterns of the simulated 18o temperature relationship for the lgm climate are practically unchanged which tends to comfort the use of water isotopes in paleoclimatology however concerning the deuterium excess i e the relationship between oxygen 18 and deuterium the model results are not sufficiently valid to allow a discussion of the use of deuterium excess in paleoclimatology