hurricanes and climate in the caribbean during the past 3700 years bp a multiproxy analysis of lacustrine sediments cored in grand case pond at saint martin north of the lesser antilles archipelago reveals three distinct climatic periods for the last 3700 years from 3700 to 2500 yr cal bp and from 1150 yr cal bp to the present carbonate mud deposition occurred in connection with pond lowstands these periods were also punctuated by severe drought events marked by gypsum laminae and hurricane landfalls leading to marine sand inputs into the pond the intermediate time interval from 2500 to 1150 yr cal bp is typified by black organic mud deposition suggesting that hypoxic to anoxic conditions prevailed at the pond bottom these were probably linked with a perennial pond highstand and reflect more uniform and wetter climatic conditions than today the carbon isotopic composition of the ostracod perissocytheridea bisulcata shows that the lowest 13c values are recorded during the hypoxic periods as a consequence of bacterial recycling of isotopically depleted org

quaternary interglacial environmental stability in san salvador island bahamas a land snail isotopic approach abstract the 13c 12c and 18o 16o ratios of modern and fossil shells of two ecologically distinct land snail taxa cerionidae and annularidae from san salvador island were analyzed to estimate the interglacial pleistocene and holocene paleoenvironmental conditions in the bahamas the average 13c value of cerion was 5 0 1 8 for modern 0 0 1 ka specimens 4 3 0 7 for late holocene 2 4 6 ka individuals 3 4 1 6 for middle holocene 5 6 3 ka shells 4 0 1 5 for 85 or 110 ka specimens and 3 6 0 4 for individuals that grew during ois 5e 125 ka annularidae specimens displayed average 13c values of 6 3 2 5 6 1 1 0 2 4 1 0 4 4 1 1 and 5 0 2 9 respectively these results suggest that snails consumed c3 and c4 plants arbitrarily through time however higher proportion of c4 plants may have been consumed in the past compared to the present cerion was 1 higher in average 13c value than annularidae specimens for some time intervals indicating greater c4 plant consumption and or higher ingestion of carbonate rich sediments the average 18o value of cerion was 0 5 0 8 for modern individuals 0 5 0 5 for late holocene specimens 0 8 0 2 for middle holocene shells 0 4 0 6 for 85 or 110 ka specimens and 0 3 0 6 for ois 5e individuals annularidae individuals exhibited average 18o values of 0 7 0 8 0 5 0 9 0 9 0 3 0 3 0 6 and 0 9 0 9 respectively these results point to similar atmospheric conditions over time intervals when shell was deposited the shell 18o values did not significantly differ between species despite the apparent differences in lifestyle calculations from a snail evaporative steady state flux balance model and proxy data suggest that modern individuals deposited shell at air temperatures of 24 25 c ambient water 18o values between 4 5 and 3 5 smow and relative humidity of 87 89 late to middle holocene and interglacial late pleistocene shells appear to have precipitated under a similar environmental setting overall atmospheric conditions during these quaternary interglacial time intervals at coastal sites of san salvador were largely comparable to the present this apparent environmental similarity is consistent with the relatively comparable snail richness and diversity observed at those same locales and time intervals

equatorward pathways of solomon sea water masses and their modifications the solomon sea is a key region of the southwest pacific ocean connecting the thermocline subtropics to the equator via western boundary currents wbcs modifications to water masses are thought to occur in this region because of the significant mixing induced by internal tides eddies and the wbcs despite their potential influence on the equatorial pacific thermocline temperature and salinity and their related impact on the low frequency modulation of el nino southern oscillation modifications to water masses in the solomon sea have never been analyzed to our knowledge a high resolution model incorporating a tidal mixing parameterization was implemented to depict and analyze water mass modifications and the solomon sea pathways to the equator in a lagrangian quantitative framework the main routes from the solomon sea to the equatorial pacific occur through the vitiaz and solomon straits in the thermocline and intermediate layers and mainly originate from the solomon sea south inflow and from the solomon strait itself water mass modifications in the model are characterized by a reduction of the vertical temperature and salinity gradients over the water column the high salinity of upper thermocline water subtropical mode water stmw is eroded and exported toward surface and deeper layers whereas a downward heat transfer occurs over the water column consequently the thermocline water temperature is cooled by 0 15 0 3 c from the solomon sea inflows to the equatorward outflows this temperature modification could weaken the stmw anomalies advected by the subtropical cell and thereby diminish the potential influence of these anomalies on the tropical climate the solomon sea water mass modifications can be partially explained 60 by strong diapycnal mixing in the solomon sea as for stmw about a third of this mixing is due to tidal mixing

nonuniform response of the major surface currents in the nordic seas to insolation forcing implications for the holocene climate variability 1 high resolution sediment cores from the voring plateau the north iceland shelf and the east greenland shelf have been studied to investigate the stability of major surface currents in the nordic seas during the holocene results from diatom assemblages and reconstructed sea surface temperatures ssts indicate a division of the holocene into three periods the holocene climate optimum 9500 6500 calendar cal years bp the holocene transition period 6500 3000 cal years bp and the cool late holocene period 3000 0 cal years bp the overall climate development is in step with the decreasing insolation on the northern hemisphere but regional differences occur regarding both timing and magnitude of sst changes sites under the direct influence of the norwegian atlantic current and the irminger current indicate sst cooling of 4 5 c from early holocene to present compared to 2 c recorded under the east greenland current superimposed on the general holocene cooling trend there is a high frequency sst variability which is in the order of 1 1 5 c for the voring plateau and the east greenland shelf and 2 5 3 c on the north iceland shelf

long term el nino southern oscillation enso like variation with special emphasis on the south pacific mechanisms for el nino southern oscillation enso like decadal 7 35 years variability are analyzed using observational data when a decadal positive temperature anomaly occurs in the eastern tropical pacific the atmospheric response excites negative wind stress curl in the western tropical south pacific which causes the thermocline to shoal and induce a negative temperature anomaly there the cold anomaly moves northwestward to the western and central equatorial region and then turns eastward along the equator to reverse the original temperature anomaly in the east the eastward propagation of the oceanic signal along the equatorial thermocline correlates with a zonal wind anomaly the cold anomaly in the east grows through tropical air sea interaction and induces a positive wind stress curl in the western tropical south pacific associated with the atmospheric teleconnection in the southern hemisphere subsequent evolution of the negative phase is similar to that of the positive phase the complete scenario for this enso like decadal variability due to the air sea interaction processes within the tropics has a period of 14 years we also discuss enso like variation on the interdecadal 35 years timescale with possible relationship to the 1976 1977 climate regime shift

drought in the northern bahamas from 3300 to 2500 years ago abstract intensification and western displacement of the north atlantic subtropical high nash is projected for this century which can decrease caribbean and southeastern american rainfall on seasonal and annual timescales however additional hydroclimate records are needed from the northern caribbean to understand the long term behavior of the nash and better forecast its future behavior here we present a multi proxy sinkhole lake reconstruction from a carbonate island that is proximal to the nash abaco island the bahamas the reconstruction indicates the northern bahamas experienced a drought from 3300 to 2500 cal yrs bp which coincides with evidence from other hydroclimate and oceanographic records e g africa caribbean and south america for a synchronous southern displacement of the intertropical convergence zone and north atlantic hadley cell the specific cause of the hydroclimate change in the northeastern caribbean region from 3300 to 2500 cal yrs bp was probably coeval southern or western displacement of the nash which would have increased northeastern caribbean exposure to subsiding air from higher altitudes

sea surface salinity structure of the meandering gulf stream revealed by smos sensor measurements from the soil moisture ocean salinity smos satellite acquired during 2012 in the western north atlantic are used to reveal the evolution of the sea surface salinity sss structure of the meandering gulf stream with an unprecedented space and time resolution combined with in situ surface and profile measurements satellite derived surface currents sea surface height ssh surface temperature sst and chlorophyll chl data smos sss observations are shown to coherently delineate meanders pinching off from the current to form well identified salty warm and fresh cold core gulf stream rings a covariance analysis at two locations along the separated gulf stream path south of nova scotia and in the gulf stream extension reveals a systematically higher correlation between sss and sea level variability than between sst and ssh during the warmer half of the year within 75 w 40 w 30 n 50 n chl concentration is also found to significantly depend on the sss as sst increases above 20 c

the southwest pacific ocean circulation and climate experiment spice the southwest pacific ocean circulation and climate experiment spice is an international research program under the auspices of clivar the key objectives are to understand the southwest pacific ocean circulation and the south pacific convergence zone spcz dynamics as well as their influence on regional and basin scale climate patterns south pacific thermocline waters are transported in the westward flowing south equatorial current sec toward australia and papua new guinea on its way the sec encounters the numerous islands and straits of the southwest pacific and forms boundary currents and jets that eventually redistribute water to the equator and high latitudes the transit in the coral solomon and tasman seas is of great importance to the climate system because changes in either the temperature or the amount of water arriving at the equator have the capability to modulate the el nino southern oscillation while the southward transports influence the climate and biodiversity in the tasman sea after 7 years of substantial in situ oceanic observational and modeling efforts our understanding of the region has much improved we have a refined description of the spcz behavior boundary currents pathways and water mass transformation including the previously undocumented solomon sea the transports are large and vary substantially in a counter intuitive way with asymmetries and gating effects that depend on time scales this paper provides a review of recent advancements and discusses our current knowledge gaps and important emerging research directions

on thermocline ventilation of active and passive tracers the ventilation propagation of temperature and passive tracer anomalies are compared in a numerical model although both anomalies tend to have pathways close to the mean ventilation flow the temperature anomaly could have a slower propagation speed and a more complex spatial structure the temperature propagation is better understood in terms of baroclinic planetary waves

a decadal spiciness mode in the tropics analysis of a complex climate model suggests the existence of a mode of coupled ocean atmosphere variability in the tropical pacific with the following dynamics anomalous strong pacific trade winds accelerate the north equatorial current and countercurrent at 10 to 15 n in the central pacific thermocline this causes anomalous advection across mean gradients of temperature and salinity on isopycnal surfaces and generates cool fresh spiciness anomalies of the order of 0 3 k these are advected by the mean circulation via the western boundary region to the equatorial pacific in approximately five years at the equatorial outcrops of the isopycnals the cool fresh anomalies affect the surface heat budget and are hypothesized to initiate a relaxation of the trade winds that is reinforced by positive feedbacks with the slope of the thermocline and with air sea fluxes of heat and freshwater at 5 to 10 s the decrease of the trades generates by anomalous advection cool fresh spiciness anomalies that migrate to the equator in one to two years and provide a positive feedback at 10 to 15 n the decrease of the trades decelerates north equatorial current and countercurrent and causes warm salty anomalies on isopycnals that arrive at the equator five years later and close the cycle

observational evidence for propagation of decadal spiciness anomalies in the north pacific 1 the propagation of density compensated warm salty or cool fresh spiciness anomalies in the north pacific thermocline is investigated using argo profiles for the period 2001 2008 a cool fresh spiciness anomaly on 25 25 5 kg m 3 isopycnals appears in the eastern subtropical north pacific at 120 w 150 w in 2003 2004 with a salinity anomaly of about 0 15 pss 78 this spiciness anomaly migrates southwestward and arrives in the western tropical north pacific at 145 e 175 w in 2008 with the salinity anomaly decreasing to about 0 043 pss 78 two warm salty anomalies are observed to propagate along the same path from 2003 to 2005 and after 2005 the propagation path and speed of the anomalies are in good agreement with advection by the mean geostrophic current in the course of propagation the anomalies are diffused and are subject to high frequency injection of spiciness anomalies especially in the eastern subtropical north pacific

strong coherence between solar variability and the monsoon in oman between 9 and 6 kyr ago variations in the amount of solar radiation reaching the earth are thought to influence climate but the extent of this influence on timescales of millennia to decades is unclear a number of climate records show correlations between solar cycles and climate1 but the absolute changes in solar intensity over the range of decades to millennia are small2 and the influence of solar flux on climate is not well established the formation of stalagmites in northern oman has recorded past northward shifts of the intertropical convergence zone3 whose northward migration stops near the southern shoreline of arabia in the present climate4 here we present a high resolution record of oxygen isotope variations for the period from 9 6 to 6 1 kyr before present in a th u dated stalagmite from oman the 18o record from the stalagmite which serves as a proxy for variations in the tropical circulation and monsoon rainfall allows us to make a direct comparison of the 18o record with the 14c record from tree rings5 which largely reflects changes in solar activity6 7 the excellent correlation between the two records suggests that one of the primary controls on centennial to decadal scale changes in tropical rainfall and monsoon intensity during this time are variations in solar radiation

upper water mass variability in the anegada jungfern passage ne caribbean during the last 11 100 cal yr using qualitative and quantitative analyses of planktonic foraminifera assemblages 18o measurements mg ca temperature relationship globigerinoides ruber pink sensu stricto data and sea surface temperatures ssts derived from artificial neural network ann transfer functions a reconstruction was made of upper water mass variability in the anegada jungfern passage ajp northeastern caribbean sea over the last c 11 100 years our record is based on the study of two marine sediment cores and reveals three main circulation stages during the holocene in the early holocene 11 100 6300 cal yr bp ann based sst estimations indicate moderately cooler than present winter condition in the ne caribbean with ssts of 25 5 c these conditions presumably reflect advection of well mixed upper water masses from the guyana upwelling area associated with a strong atlantic meridional overturning circulation amoc and enhanced trade wind activity linked to a more northerly location of the inter tropical convergence zone itcz between 6300 and 3700 cal yr bp a relative warming of winter ssts 26 5 c was probably related to a weaker circulation and upper water mass mixing because of less intense trade wind activity as the itcz moved southwards from 3700 cal yr bp to the present the region was characterised by small seasonal sst variations and generally stable winter and summer ssts the data suggest a minor shift in the sub surface inflow pattern during the last 2000 years possibly related to changes in northern hemisphere large scale atmospheric circulation also observed at higher latitude the ann based temperature pattern is supported by fluctuations in the mg ca derived temperature record although temperature maxima derived from the mg ca ratio appear anomalously high on a holocene timescale we conclude that the northeastern caribbean sst and circulation regime have been mainly dependent on the position of the itcz which in turn is controlled by changes in hemispheric solar insolation

the association between enso and winter atmospheric circulation and temperature in the north atlantic region the association among enso the northern hemisphere sea level pressure slp and temperatures in europe has been analyzed during the period 1873 1995 in the first part the sst of the nino 3 region has been used to select extreme cold and warm enso events and periods that can be regarded as normal the study was carried out for winter with the constraints that the enso events were well developed during the winter of study and that they are extreme events composites of winter slp and temperatures have been made for the selected cold and warm events as well as for normal cases and compared with each other in the north atlantic area no statistically significant slp anomaly patterns were found associated with warm events while during cold events a statistically significant anomaly pattern resembling the positive phase of the north atlantic oscillation nao was found the temperature analysis shows statistically significant negative anomalies during cold events over the iberian peninsula and positive anomalies over the british isles and southern scandinavia consistent with the slp anomalies the slp and temperatures have also been analyzed for spring the patterns resemble those found for winter but the anomalies have lower amplitudes for the completion of the composite analysis the consistency among events of the relationship between enso and slp as well as between enso and temperatures was examined the results show that the significant patterns found in the composite analysis in the north atlantic area are not the result of a few major events but rather because both the slp and temperature anomalies in this area during cold enso events are stable and qualitatively similar to those found during the positive phase of the nao the possible physical basis for this association between nao and enso is discussed

warm period growth of travertine during the last interglaciation in southern germany abstract late quaternary travertine at two sites near stuttgart formed entirely during interglacial periods the travertine contains structures from growth induced by bacteria and such structures have been dated by 230th u mass spectrometry the resulting ages from both sites imply growth episodes of short duration with growth rates up to 5 mm yr 1 at 99 800 1300 yr b p 2 n 8 and 105 900 1300 yr b p 2 n 7 these episodes were likely part of marine isotope stage mis 5 3 deposition of silt interrupted travertine growth at one of the sites 105 000 yr b p likely correlatives of this silt are the st germain i b stade recorded in the grand pile peat bog and a cold episode 1000 yr long recorded by 18o values in the grip ice core travertine also formed during stage 5 5 115 000 yr and during the early holocene we found no evidence for travertine accumulation in stages 2 3 4 and 5 1 at both sites the sr u ratio and the initial 234u 238u activity ratio resemble those of modern spring water however the sites differ in the chemical composition of spring water and in stratigraphic sequence of travertine accumulation

large kinetic isotope effects in modern speleothems the application of stable isotopes in speleothem records requires an understanding of the extent to which speleothem calcite isotopic compositions refl ect the compositions of the cave waters from which they precipitate to test for equilibrium precipitation modern speleothem calcite was grown on glass plates so that the carbon and oxygen isotope composition of the calcite and the water from which it precipitated could be directly compared the plates were placed on the tops of three actively growing stalagmites that occupy a 1 m 2 area in harrison s cave barbados west indies only some of the plate 13 c values and none of the plate 18 o values correspond to equilibrium values indicating signifi cant kinetic isotope effects during speleothem calcite growth we investigate herein mechanisms that may account for the kinetic isotope effects on each plate speleothem calcite was deposited with distinct 18 o and 13 c compositions that increase progressively away from the growth axis with up to 6 6 13 c and 1 7 18 o enrichments the positive 13 c

caribbean hydrological variability during the holocene as reconstructed from crater lakes on the island of grenada contemporary precipitation patterns in the caribbean region are spatially variable and the small number of holocene paleoclimatic records may not adequately capture patterns of variation in the past the hydrological history of grenada was inferred from paleolimnological analyses of sediment cores from two crater lakes on the island the basins were formed by volcanic activity some time during the last termination but were dry between ca 13 000 and ca 7200 cal a bp after filling the lakes were initially very shallow and sedimentation was interrupted by a hiatus ca 6300 5500 cal a bp followed by deposition of a thick tephra in both sites after 5500 cal a bp lake level shows considerable multi centennial variability superimposed upon a long term trend of generally higher lake level after 3200 cal a bp the pattern of lake level variation in grenada shows some similarity with other caribbean paleoclimatic records in terms of the timing of transitions but differs from several classic studies in the sign of inferred precipitation change the differences among records may reflect spatially variable precipitation patterns in the past in response to the position of the intertropical convergence zone and to sea surface temperature influences on the trade winds and caribbean low level jet copyright c 2011 john wiley sons ltd less

generation and initial evolution of a mode water θ s anomaly abstract generation and evolution of an isopycnal potential temperature salinity s or spiciness anomaly is studied around 20 23 s 110 w in the austral winter of 2004 two profiling ctd floats deployed in the region in january 2004 provide the observations the anomaly defined as relative to water properties of the preceding summer is very large initially about 0 35 in s and about 0 9 c in it is associated with the winter ventilation of a thick low potential vorticity layer known as south pacific eastern subtropical mode water regional lateral and s distributions at the surface predispose the ocean to formation of this water mass and allow significant anomalies to be generated there with relative ease the water mass is potentially important for climate in that after northwestward advection in the south equatorial current it contributes to the equatorial undercurrent and eventually resurfaces in the cold tongue of the eastern equatorial pacific ocean the anomaly studied is strong enou

a paleoclimate record of the last 17 600 years in stalagmites from the b7 cave sauerland germany abstract petrographical and geochemical parameters of stalagmites from the b7 cave in iserlohn letmathe northern rhenish massif nw germany record late and postglacial climate changes temperature and or precipitation fabrics and microfacies of the stalagmite profiles lead to a differentiation of four hierarchies of rhythms clastic layers in the stalagmites are caused by flooding events and are time markers twenty four tims th u age dates provide a time calibration of stalagmite growth phases one stalagmite reveals an early growth period between 17 6 and 16 7 ka bp between 9 6 and 5 5 ka bp atlantic episode of the holocene the growth rate of the stalagmites was higher than before and after this time with dominant light porous microfacial laminae and high 18 o and 13 c values representing partly kinetic fractionation effects this part of the holocene is interpreted as a mainly warm episode with frequent interruptions of dripping within the past 4 ka the profiles with predominant dark compact facies reveal low isotopic values which may be interpreted as a temperature proxy record the stalagmite records resemble records from an irish stalagmite correlation with the 14 c record from european tree rings suggests that colder periods in the north atlantic were accompanied by drier winters in central europe

generation mechanism of spiciness anomalies an ogcm analysis in the north atlantic subtropical gyre oceanic teleconnections between the low and midlatitudes are a key mechanism to understanding the climate variability spiciness anomalies density compensated anomalies have been shown to transport temperature and salinity signals when propagating along current streamlines in the subtropical gyres of the atlantic and pacific oceans the generation mechanism of spiciness anomalies in the north atlantic subtropical gyre is investigated using an analytical model based on the late winter subduction of salinity and temperatureanomalies along isopycnal surfaces the keystone ofthis approachisthe change ofthe coordinates frame from isobaric to isopycnic surfaces suited for subduction problems the isopycnal nature of spiciness anomalies and the use of a linear density equation allows for the analytical model to depend only upon surface temperature and salinity anomalies the mean thermocline currents and the surface density ratio this model clarifies and above all quantifies the mechanism by which surface temperature and salinity anomalies are modulated by density ratios to produce fully different isopycnal temperature and salinity anomalies

millennial scale climate variability during the last 12 5 ka recorded in a caribbean speleothem abstract we present a speleothem stable oxygen isotope record for the last 12 5 ka based on two stalagmites from western cuba the 18o signal is interpreted to represent past precipitation variability both stalagmites show a pronounced transition from higher 18o values indicating drier conditions to more negative 18o values suggesting wetter conditions between 10 and 6 ka this transition is also visible in a planktonic 18o record off haiti on orbital timescales the 18o value of caribbean precipitation thus strongly resembles the oxygen isotope composition of caribbean surface water on millenial timescales the speleothem 18o record shows a high correlation to a north atlantic sea surface temperature sst record off west africa as well as a similarity with the bond events periods of lower north atlantic sst correspond to less precipitation in the caribbean and vice versa the potential teleconnection to the caribbean may reflect the position of the intertropical convergence zone because a further southward position of the itcz leads to reduced precipitation in the northern caribbean

effects of sea level rise and climatic changes on mangroves from southwestern littoral of puerto rico during the middle and late holocene abstract we evaluated the response to sea level rise and climatic changes of the northeastern caribbean by establishing a palaeoenvironmental reconstruction of the flamenco lagoon located in the coastal side of the guanica dry forest a mab unesco reserve in the semi arid southwestern coast of puerto rico 17 57 10 31 n 66 50 39 30 w the reconstruction was based on pollen records sediments analysis 13 c 15 n c n data and ams 14 c dating of one sediment core the geology of the area is rocky calcareous karst with rocky outcrops and canyons with intermittent streams that move water during periods of high run off conditions the present lagoon is surrounded by rocky outcrops where dry forest vegetation is present on the terrestrial sides and sand dunes on the coastal side we propose that the studied lagoon developed after the stabilization of sea level rise in the region following three main stages 1 before 5400 cal yr bp sediments were accumulated according to small channels dynamics and trees shrubs and herbs were present the sedimentary organic matter was mainly sourced from terrestrial c 3 and c 4 plants 2 between 5400 and 4400 cal yr bp tidal flats were established and mangroves mainly represented by rhizophora trees migrated landward with sea level rise and established in the area and the sedimentary organic matter was sourced from terrestrial c 3 plants 3 around 4400 cal yr bp sea level was near the stabilization the endorheic minibasin was closed when a coastal sand dune was established as a result of drier climatic conditions mangroves were eliminated from the system as a result of the closure of the area by sand dunes and increased salinity in water due to high evaporative demand of the climate the pollen dominance of herbaceous and shrubby vegetation prevails until present throughout the lagoon development sedimentary organic matter was sourced from c 3 and c 4 plants as well as phytoplankton organic matter the closure of the lagoon and the drier conditions prevalent in the region during the late holocene which lasts until the present day and increased the contribution of salinity tolerant phytoplankton that characterizes the current conditions of the flamenco lagoon

combined records from a stalagmite from barbados and from lake sediments in haiti reveal variable seasonality in the caribbean between 6 7 and 3 ka bp abstract the growth of a well dated stalagmite from barbados records high infiltration rates into the karst aquifer and hence increased rainfall intensity between 6 7 and 3 ka bp in agreement with records from lake miragoane haiti hodell et al 1991 reconstruction of the caribbean climate change over the past 10 500 years nature 352 790 793 mainly reflecting the insolation maximum of the northern hemisphere both the lake record and the stable isotope record of the stalagmite reveal additional centennial variability of recharge high oxygen isotope values in stalagmite calcite corresponding to reduced recharge are synchronous with periods of lower stable isotope values recorded in lake miragoane ostracods previously attributed to enhanced precipitation accordingly periods of increased recharge in barbados correspond to 18o enriched isotope values of ostracods which were attributed to higher evaporation precipitation ratios in the lakes we ascribe this apparent discrepancy to changes in seasonality i e winter periods of reduced temperature and relative humidity following summer months of increased precipitation at present such climate conditions occur during periods of enhanced northern atlantic oscillation nao if enhanced seasonality is a consequence of a nao situation the apparent discrepancy of high isotope values in lakes previously attributed to droughts can be reconciled with lower winter temperatures in the lakes further the correlation of solar intensity derived from 14c and 10be with the isotopic signals recorded in the lacustrine sediments suggests a solar forcing of the nao during the mid holocene

a possible mechanism of solar modulation of the spatial structure of the north atlantic oscillation 1 the spatial structure of the north atlantic oscillation nao in winter differs significantly according to the solar cycle the nao is confined to the atlantic sector during low solar activity ls whereas it has a hemispherical structure during high solar activity hs the present study focuses on identifying the involved processes the results of analyses suggest that the solar activity influence originates in the stratopause region where the mode of interannual variation in the zonal mean zonal winds changes according to solar activity in the early winter of hs the leading zonal wind mode has a meridional dipole type structure that extends downward from the stratosphere to the troposphere through interaction with planetary waves the dipole type anomaly in the zonal winds produces a hemispherical scale seesaw pattern in the surface pressure between the polar region and surrounding regions thus the nao during hs has a hemispherical pattern during ls the downward extension of zonal mean zonal wind anomalies is weak so the regional scale variation becomes dominant in the troposphere

cuban stalagmite suggests relationship between caribbean precipitation and the atlantic multidecadal oscillation during the past 1 3 ka here we present the first high resolution 18o record of a stalagmite from western cuba the record reflects precipitation variability in the northwestern caribbean during the last 1 3 ka and exhib

a cost surface model of volcanic glass quarrying and exchange in hawai i abstract the spatial distribution of artifacts from the pu u wa awa a volcanic glass source north kona district hawai i island shows a pattern of direct access by those living in the immediately vicinity of the source with subsequent down the line exchange most quarrying and exchanges likely occurred within a single day s travel from sites where artifacts were deposited the exception to this is the discovery of non local direct access evident in assemblages from the extreme southern end of hawai i island these visits may have involved voyages by canoe while people did not often travel far for volcanic glass they nonetheless appear to have had unfettered accessed to source material and freely conducted inter community exchanges this implies volcanic glass was treated as a common pooled resource and the existence of informal exchange relationships

mechanisms of tropical pacific interannual to decadal variability in the arpege orca global coupled model spatial and temporal structures of interannual to decadal variability in the tropical pacific ocean are investigated using results from a global atmosphere ocean coupled general circulation model the model produces quite realistic mean state characteristics despite a sea surface temperature cold bias and a thermocline that is shallower than observations in the western pacific the periodicity and spatial patterns of the modelled el nino southern oscillations enso compare well with those observed over the last 100 years although the quasi biennial timescale is dominant lag regression analysis between the mean zonal wind stress and the 20 c isotherm depth suggests that the recently proposed recharge oscillator paradigm is operating in the model decadal thermocline variability is characterized by enhanced variance over the western tropical south pacific 7 s the associated subsurface temperature variability is primarily due to adiabatic displacements of the thermocline as a whole arising from ekman pumping anomalies located in the central pacific south of the equator related wind anomalies appear to be caused by sst anomalies in the eastern equatorial pacific this quasi decadal variability has a timescale between 8 years and 20 years the relationship between this decadal tropical mode and the low frequency modulation of enso variance is also discussed results question the commonly accepted hypothesis that the low frequency modulation of enso is due to decadal changes of the mean state characteristics

a simple model of the mass exchange between the subtropical and tropical ocean abstract a simple ventilated thermocline model is used to study the subtropical tropical mass exchange it is found that the water subducted in the western subtropical gyre recirculating window tends to recirculate within the subtropical gyre while the water subducted in the eastern part exchange window tends to penetrate equatorward the exchange window expands with an increased easterly wind or basin width on the southern boundary of the subtropical gyre but shrinks with an increased wind curl within the subtropical gyre furthermore the total exchange transport increases with the easterly wind or the width of the basin on the southern boundary of the subtropical gyre but it is independent of subtropical wind the ventilation mechanism is important in supporting the exchange transport for wind with realistic strength at the southern boundary the reduction of the exchange transport is about 15 30 of the ekman transport finally relative to the exchange transport in the interior of the ocean

a 10 300 14c yr record of climate and vegetation change from haiti abstract pleistocene and holocene vegetation dynamics in the american tropics are inferred largely from pollen in continental lake sediments maritime influences may have moderated climate and vegetation changes on caribbean islands stable isotope 18 o study of a 7 6 m core from lake miragoane haiti provided a high resolution record of changing evaporation precipitation e p since 10 300 14 c yr b p the miragoane pollen record documents climate influences and human impacts on vegetation in hispaniola the 18 o and pollen data near the base of the core indicate cool dry conditions before 10 000 14 c yr b p lake miragoane filled with water in the early holocene as e p declined and the freshwater aquifer rose despite increasing early holocene moisture shrubby xeric vegetation persisted forest expanded 7000 14 c yr b p in response to greater effective moisture and warming the middle holocene 7000 3200 14 c yr b p was characterized by high lake levels and greatest relative abundance of pollen from moist forest taxa climatic drying that began 3200 14 c yr b p may have driven some mesophilic animal species to extinction the pollen record of the last millennium reflects pre columbian taino and european deforestation long term holocene vegetation trends in southern haiti are comparable to trends from continental lowland circum caribbean sites suggesting a common response to regional climate change

properties formation and dissipation of the north pacific eastern subtropical mode water and its impact on interannual spiciness anomalies abstract the properties formation and dissipation of the north pacific eastern subtropical mode water estmw their interannual variability and impact on spiciness anomalies in the upper permanent pycnocline were investigated using argo profiling float data in 2005 2015 the core temperature and salinity of estmws were horizontally compensated to a constant density and core potential density concentrates in a range of 24 5 25 2 kg m 3 with two distinct peaks estmws showed different spatial distribution and persistence for its core potential density denser estmws with a potential density of 24 9 25 2 kg m 3 were formed in winter mixed layer depth maximum centered at 30 n 140 w and lighter estmws of 24 5 24 9 kg m 3 were formed south and east of it after formation through shoaling of the winter mixed layer the former persisted until the following autumn and a small part of it subducted in winter while the latter dissipated in summer the formation region of estmw corresponded to the summer sea surface density maximum resulting from its poleward sea surface salinity front sea surface density maximum maintains weak stratification during summer preconditioning the deepening of the winter mixed layer and hence the formation of estmws a relationship between the estmw formation region and the summer sea surface density maximum was also found in the north atlantic and the south pacific implying the importance of sea surface salinity fronts and the associated summer sea surface density maximum to estmw formation interannual variations of estmw reflected that of the winter mixed layer in its formation region and the thickness of estmw was related to the pacific decadal oscillation estmw contributed to the occurrence of spice injection and affected spiciness anomalies in the upper permanent pycnocline through its formation and dissipation

speleothem calcite farmed in situ modern calibration of δ18o and δ13c paleoclimate proxies in a continuously monitored natural cave system abstract understanding the relationships between speleothem stable isotopes 13 c 18 o and in situ cave forcing mechanisms is important to interpreting ancient stalagmite paleoclimate records cave studies have demonstrated that the 18 o of inorganically precipitated low temperature speleothem calcite is systematically heavier than the 18 o of laboratory grown calcite for a given temperature to understand this apparent offset rainwater cave drip water groundwater and modern naturally precipitated calcite farmed in situ were grown at multiple locations inside hollow ridge cave in marianna florida high resolution micrometeorological air chemistry time series and ventilation regimes were also monitored continuously at two locations inside the cave supplemented with periodic bi monthly air gas grab sample transects throughout the cave cave air chemistry and isotope monitoring reveal density driven airflow pathways through hollow ridge cave at velocities of up to 1 2 m s 1 in winter and 0 4 m s 1 in summer hollow ridge cave displays a strong ventilation gradient in the front of the cave near the entrances resulting in cave air that is a mixture of soil gas and atmospheric co 2 a clear relationship is found between calcite 13 c and cave air ventilation rates estimated by proxies pco 2 and 222 rn calcite 13 c decreased linearly with distance from the front entrance to the interior of the cave during all seasons with a maximum entrance to interior gradient of 13 c caco3 7 a whole cave hendy test at multiple contemporaneous farming sites reveals that ventilation induces a 1 9 0 96 13 c offset between calcite precipitated in a ventilation flow path and calcite precipitated on the edge or out of flow paths this interpretation of the hendy test has implications for interpreting 13 c records in ancient speleothems calcite 13 c caco3 may be a proxy not only for atmospheric co 2 or overlying vegetation shifts but also for changes in cave ventilation due to dissolution fissures and ceiling collapse creating and plugging ventilation windows farmed calcite 18 o was found to exhibit a 0 82 0 24 offset from values predicted by both theoretical calculations and laboratory grown inorganic calcite unlike 13 c caco3 oxygen isotopes showed no ventilation effects i e 18 o caco3 appears to be a function of growth temperature only although we cannot rule out a small effect of unmeasured gradients in relative humidity evaporation accompanying ventilation our results support the findings of other cave investigators that water calcite fractionation factors observed in speleothem calcite are higher that those measured in laboratory experiments cave and laboratory calcite precipitates may differ mainly in the complex effects of kinetic isotope fractionation combining our data with other recent speleothem studies we find a new empirical relationship for cave specific water calcite oxygen isotope fractionation across a range of temperatures and cave environments 1000 ln 16 1 10 3 t 1 24 6 with a fractionation temperature dependence of 18 o t 0 177 c lower than the currently accepted 0 206 c

sub milankovitch climatic cycles in holocene stalagmites from sauerland germany calcitic stalagmites from caves in the sauerland germany prove the existence of sub milankovitch cycles in precipitation during the last 6000 yr the 18o record dated with th u is interpreted as an indicator of paleohumidity spectral analysis of 18o from 6000 a bp up to the recent top of a stalagmite from the atta cave yields statistically significant peaks at 1450 117 64 and 57 a additionally we find a good correlation of the stalagmite s 18o and 14c from european tree rings the 1450 a cycle in the stalagmite probably is analogous to the pervasive millennial scale climate cycle described by bond et al science 278 1997 1257 1266 294 2001 2130 2136 derived from the amount of ice rafted debris in deep sediments from the north atlantic our results suggest that the centennial to millennial shifts observed in the north atlantic are accompanied by synchronous shifts of the climate in northern and central europe which most probably can be attributed to solar irradiation variations

holocene itcz and indian monsoon dynamics recorded in stalagmites from oman and yemen socotra abstract high resolution oxygen isotope 18o profiles of holocene stalagmites from four caves in northern and southern oman and yemen socotra provide detailed information on fluctuations in precipitation along a latitudinal transect from 12 n to 23 n 18o values reflect the amount of precipitation which is primarily controlled by the mean latitudinal position of the itcz and dynamics of the indian summer monsoon ism during the early holocene rapidly decreasing 18o values indicate a rapid northward displacement in the mean latitudinal position of the summer itcz and the associated ism rainfall belt with decadal to centennial scale changes in monsoon precipitation correlating well with high latitude temperature variations recorded in greenland ice cores during the middle to late holocene the summer itcz continuously migrated southward and monsoon precipitation decreased gradually in response to decreasing solar insolation a trend which is also recorded in other monsoon records from the indian and east asian monsoon domains importantly there is no evidence for an abrupt middle holocene weakening in monsoon precipitation although abrupt monsoon events are apparent in all monsoon records they are short lived and clearly superimposed on the long term trend of decreasing monsoon precipitation for the late holocene there is an anti correlation between ism precipitation in oman and inter monsoon spring autumn precipitation on socotra revealing a possible long term change in the duration of the summer monsoon season since at least 4 5 ka bp together with the progressive shortening of the ism season gradual southward retreat of the mean summer itcz and weakening of the ism the total amount of precipitation decreased in those areas located at the northern fringe of the indian and asian monsoon domains but increased in areas closer to the equator

a lagrangian numerical investigation of the origins and fates of the salinity maximum water in the atlantic the origins and fates of the atlantic salinity maximum water smw formed through excess evaporation in the tropics and subtropics of both hemispheres are studied using monthly mean outputs of a numerical simulation of the world ocean climatological circulation after defining formation domains from the surface salinity field and the vertical stratification a lagrangian technique is used to estimate the formation rates and main pathways in each hemisphere and the role of this water in the framework of the warm water return flow of the meridional overturning cell formation rates around 9 and 11 sv are found in the southern and northern hemispheres respectively while the export of the southern smw from its formation area is realized by the western boundary currents that of the northern smw mainly results from interior subduction equatorward of the formation regions a fraction of each smw variety is entrained in the subtropical cells that connect the subtropics to the equatorial region poleward of them both varieties are seen to feed the regions of subtropical mode water stmw formation around 35 of latitude in both hemispheres the bulk of the transport associated with each variety eventually turns northward this amounts to 6 sv of southern smw gathered in the north brazil undercurrent nbuc and 10 sv of northern smw found in the gulf stream at 35 n of which 8 sv have gone through the caribbean sea of the 13 4 sv northward transport of the meridional overturning cell estimated by the model at 47 n more than 50 6 9 sv is found to have transited through at least one of the smw regions this gives an indication of the likely important role of smw formation in the observed northward salinity increase of the upper atlantic ocean

subduction of decadal north pacific temperature anomalies observations and dynamics abstract observations of oceanic temperature in the upper 400 m reveal decadal signals that propagate in the thermocline along lines of constant potential vorticity from the ventilation region in the central north pacific to approximately 18 n in the western pacific the propagation path and speed are well described by the geostrophic mean circulation and by a model of the ventilated thermocline the approximate southward speed of the thermal signal of 7 mm s 1 yields a transit time of approximately eight years the thermal anomalies appear to be forced by perturbations of the mixed layer heat budget in the subduction region of the central north pacific east of the date line a warm pulse was generated in the central north pacific by a series of mild winters from 1973 to 1976 and reached 18 n around 1982 after 1978 a succession of colder winters initiated a cold anomaly in the central north pacific that propagated along a similar path and with a similar speed as the warm anomaly then arrived in the west

decadal thermocline variability in the north pacific ocean two pathways around the subtropical gyre yearly in situ temperature anomaly data in the north pacific ocean for 1961 90 have been analyzed along constant density surfaces isopycnals in order to better describe and understand decadal thermocline variability in the region various empirical orthogonal function analyses are performed on isopycnals to depict the dominant three dimensional patterns the major finding is of two preferential pathways associated with decadal temperature variability around the subtropical gyre a subduction pathway with a large signal in the upper thermocline originates from the north pacific central eastern outcrop regions about 408n 1508w and then basically follows the mean gyre circulation southwestward along isopycnals toward the western tropics a subtropical pathway extends from the eastern subtropical tropical and boundary regions and appears to continue predominantly westward across the southern part of the gyre between 158 and 308n and then along the kuroshio path toward the midlatitudes along these two pathways thermal anomalies show coherent phase relationships to one another in the surface layer and in the thermocline around the gyre with their source regions variability centers being out of phase on decadal timescales two examples of each type of anomaly pattern can be illustrated for the periods analyzed in the 1960s a negative temperature anomaly signal propagated predominantly westward across the subtropics followed by a subducted warm anomaly from the outcrop region in the early 1970s that subsequently moved southwestward along isopycnals toward the western tropics a similar pattern was observed in the late 1970s and in the 1980s but with the opposite sign a westward propagating positive temperature anomaly signal along the subtropics in the late 1970s through the 1980s and a subducted cold anomaly in the early 1980s that also made its way southwestward with the expected gyre circulation to the western tropics in the late 1980s it is suggested that the southwestward subduction pathway provides a mechanism that connects surface anomalies in the outcrop region to thermocline variations in the western subtropics and in the tropics and that the westward subtropical pathway presents a possible link of tropical subtropical variability to surface temperature anomalies around the kuroshio and its extension regions which may further force variations in the overlying atmospheric circulation in the midlatitudes the results provide an observational basis for verification of theoretical studies and model simulations

estimating recharge thresholds in tropical karst island aquifers barbados puerto rico and guam the hydrology and geochemistry of groundwater in tropical island aquifers such as barbados guam and puerto rico are significantly influenced by tropical climatic conditions recharge to these aquifers is the product of regional and local climate patterns that control rainfall oxygen isotopes can be used to estimate the amount and timing of recharge on these islands because seasonal fluctuations of rainwater oxygen isotopic compositions are related to the amount of rainfall the karst aquifers on barbados guam and puerto rico have similar rainwater and groundwater oxygen isotopic compositions comparison of groundwater and rainwater oxygen isotopic compositions in the three aquifers indicates that 1 recharge occurs by rapid infiltration with little evaporation prior to recharge and 2 recharge is associated with similar monthly rainfall thresholds of 190 200 mm these rainfall thresholds are remarkably similar for three aquifers in different geographic locations differences between the spatial variations of groundwater oxygen isotopic compositions on barbados and puerto rico can be attributed to the more complex groundwater flow system on puerto rico the surprising similarities of hydrologic conditions under which recharge will take place can be attributed to similarities in climate and geologic conditions such as soils and limestone bedrock that exist on the three islands we therefore speculate that similar recharge rainfall thresholds may be observed in other tropical karst aquifers q 2003 elsevier science b v all rights reserved

persistent influence of the north atlantic hydrography on central european winter temperature during the last 9000 years 1 a prominent feature of the n atlantic s holocene climate is a series of centennial and millennial shifts in ocean surface hydrography bond et al 2001 oppo et al 2003 here we compare a climate reconstruction from the central alps for the last 9 000 years derived from the oxygen isotope record in stalagmites with the percentage of hematite stained grains in n atlantic sediments an indicator for the proportion of ice bearing surface water from north of iceland the excellent match between the two curves proves that meteorological conditions in the alpine region responded synchronously to changes in the hydrography of the n atlantic during winter in addition the speleothem record suggests significant multi centennial and millennial variability of n european winters throughout the past 9 000 years that might have been incompletely recorded in tree ring archives

the use of foraminifera as a record of the past neodymium isotope composition of seawater 1 we present new isotopic data for sedimentary planktonic foraminifera as well as for potential water column and sedimentary sources of neodymium nd which confirm that the isotopic composition of the foraminifera is the same as surface seawater and very different from deep water and sedimentary nd the faithfulness with which sedimentary foraminifera record the isotopic signature of surface seawater nd is difficult to explain given their variable and high nd ca ratios ratios that are often sedimentary foraminifera ratios that are often much higher than is plausible for direct incorporation within the calcite structure we present further data that demonstrate a similarly large range in nd ca ratios in plankton tow foraminifera a range that may be controlled by redox conditions in the water column cleaning experiments reveal in common with earlier work that large amounts of nd are released by cleaning with both hydrazine and diethylene triamine penta acetic acid but that the nd released at each step is of surface origin while further detailed studies are required to verify the exact location of the surface isotopic signature and the key controls on foraminiferal nd isotope systematics these new data place the use of planktonic foraminifera as recorders of surface water nd isotope ratios and thus of variations in the past supply of nd to the oceans from the continents via weathering and erosion on a reasonably sure footing

interdecadal changes in eastern pacific itcz variability and its influence on the atlantic itcz the eastern pacific and atlantic intertropical convergence zones itcz exhibit the largest year to year variations in boreal spring we show evidence suggesting that atlantic itcz april may variability is linked to that for the eastern pacific through the walker circulation as it respond to changes in equatorial pacific convection analysis of itcz proxy indices shows the link appears to be strong in the 1980 90 s and 1920 30 s but virtually nonexistent in the 1950 60 s we argue that this apparent nonstationarity results from the nonlinear relationship between sea surface temperature sst and convection in the eastern equatorial pacific and its consequent effect on the walker circulation and the atlantic itcz this mechanism was modulated over 1856 1998 by interdecadal changes in peak sst attained in the eastern equatorial pacific during boreal spring

interannual variability of the subsurface high salinity tongue south of the equator at 165 e abstract a 14 yr time series of salinity at thermocline level was constructed from repeated meridional ctd sections averaging about 110 days apart spanning the equator along 165 e during 1984 97 a tongue of high salinity water extends along the isopycnal t 24 5 from its surface outcrop in the southeast pacific to 175 m depth near 5 10 s along the section at 165 e in the west the tongue moves vertically with the thermocline mostly as part of the enso cycle while salinity in the tongue varied interannually over a range of 0 4 psu most of this variability was due to zonal advection along the isopycnal tongue with similar changes observed at other longitudes in the west and central pacific part of the interannual salinity signal can be attributed to changes in the near zonal flow of the south equatorial current associated with el nino but a general 0 3 psu rise occurring during the 1990s probably starting even earlier was not apparently consistent with this explanation an attempt was made to

hydrogeologic and climatic influences on spatial and interannual variation of recharge to a tropical karst island aquifer 1 the hydrology and geochemistry of groundwater in tropical island aquifers such as on barbados are significantly influenced by tropical climatic conditions recharge to these aquifers is the product of regional and local climate patterns that control rainfall oxygen isotopes can be used to estimate the amount and timing of recharge on these islands because seasonal fluctuations of rainwater oxygen isotopic compositions are related to the amount of rainfall this study shows that estimates of average annual recharge to the limestone aquifer on barbados vary widely displaying a more direct relationship to the distribution of rainfall throughout each year than to total annual rainfall recharge estimates are higher during years when rainfall is concentrated in the peak wet season months than during years when rainfall is more evenly distributed throughout the year the el nino southern oscillation appears to be partially responsible for these rainfall and recharge fluctuations knowledge of interannual variation of recharge and processes responsible is important because recharge variation must be considered when setting groundwater management policies related to groundwater availability

quantitative estimates of temperature and precipitation changes over the last millennium from pollen and lake level data at lake joux swiss jura mountains abstract this paper presents quantitative climate estimates for the last millennium using a multi proxy approach with pollen and lake level data from lake joux swiss jura mountains the climate reconstruction based on the modern analogue technique indicates warmer and drier conditions during the medieval warm period mwp mwp was preceded by a short lived cold humid event around ad 1060 and followed by a rapid return around ad 1400 to cooler and wetter conditions which generally characterize the little ice age lia around ad 1450 solar sporer minimum the lia attained a temperature minimum and a summer precipitation maximum the solar maunder minimum around ad 1690 corresponded at joux to rather mild temperatures but maximal annual precipitation these results generally agree with other records from neighbouring alpine regions however there are differences in the timing of the lia temperature minimum depending on the proxy and or the method used for the reconstruction as a working hypothesis the hydrological signal associated with the mwp and lia oscillations at lake joux may have been mainly driven by a shift around ad 1400 from positive to negative nao modes in response to variations in solar irradiance possibly coupled with changes in the atlantic meridional overturning circulation

high resolution temporal record of holocene ground water chemistry tracing links between climate and hydrology strontium isotope analysis of precisely dated calcite growth layers in holocene speleothems from barbados west indies reveals high resolution temporal variations in ground water composition and may provide a new approach to documenting the links between climate variability andfluctuations in the hydrologic cycle such as recharge rates andflow paths the speleothems grew in a cave that developed in a fresh water aquifer in upliftedpleistocenereeflimestones threeperiodsofground watersrisotopeevolutionare observed 87 sr 86 srvaluesdecreasedfrom6to4ka increasedfrom4to1ka anddecreased again after 1 ka the sr isotope oscillations appear to record periodic variations in the relative sr fluxes to ground water from exchangeable soil sites vs carbonate mineral reactions asreflectedin 87 sr 86 srvaluesofmodernbarbadosgroundwaters ahydrologic model that explains changes in ground waterflow routes in karst aquifers as a function of amountofrainfallrechargecanaccountforthespeleothemsrisotoperecord independent holoceneclimaterecordsthatindicateamajorperiodofaridityataround1 3 1 1kainthe american tropics correspond with periodic variations in rainfall on barbados that are predicted by this hydrologic model

stable isotope proxy records in tropical terrestrial environments abstract the tropics refers to an area that is loosely equatorial characterized by relatively high temperatures at low altitude comparatively low seasonal contrast in temperatures and generally high or highly seasonal rainfall the stable isotopes of carbon oxygen and hydrogen are increasingly important tools of relevance to understanding trajectories and mechanisms of past environmental change in the tropics in the case of carbon this is because at the broadest level the carbon isotope composition of organic and carbon containing inorganic proxy materials formed in the tropics can be read as being derived from the balance between c3 tree and c4 grass photosynthesis hence providing a relative measure of vegetation type and indirectly climate likewise changes in the oxygen and hydrogen isotope composition of many proxy materials again at the broadest level can be read as indicative of changes in hydrological conditions and or altitude in the past this review provides an entry point into the literature relating to the use of stable isotopes as terrestrial environmental proxies for past environmental change with a focus on the measurement and interpretation of stable isotope data from the wide range of proxy materials preserved in tropical environments

wind stress curl and enso discharge recharge in the equatorial pacific discharge and recharge of the warm water volume wwv above the 20 c isotherm in an equatorial pacific ocean box extending across the pacific from 156 e to the eastern ocean boundary between latitudes 5 s and 5 n are key variables in enso dynamics a formula linking wwv anomalies zonally integrated wind stress curl anomalies along the northern and southern edges of the box and flow into the western end of the box is derived and tested using monthly data since 1993 consistent with previous work a wwv balance can only be achieved if the 20 c isotherm surface is not a material surface that is warm water can pass through it for example during el nino part of the wwv anomaly entering the box is cooled so that it is less than 20 c and therefore passes out of the bottom of the box the 20 c isotherm surface the observations suggest that the anomalous volume passing through the 20 c isotherm is approximately the same as t the anomalous wwv entering the western end of the box therefore the observed wwv anomaly can be regarded as being driven by the anomalous wind stress curl along the northern and southern edges of the box the curl anomaly changes the wwv both by divergent meridional flow at the edges of the box and vortex stretching that is the sverdrup balance does not hold in the upper ocean a typical amplitude for the rate of change of wwv for the 5 s 5 n box is 9 6 sv sv 10 6 m 3 s 1 the wind stress curl anomaly and the transport anomaly into the western end of the box are highly correlated with the el nino index nino 3 4 the average sea surface temperature anomaly ssta over the region 5 s 5 n 170 120 w and nino 3 4 leads minus the wwv anomaly by one quarter of a cycle based on the preceding results a simple discharge recharge coupled enso model is derived only water warmer than about 27 5 28 c can give rise to deep atmospheric convection so unlike past discharge recharge oscillator models the west central rather than eastern equatorial sstas are emphasized the model consists of two variables t the ssta averaged over the region of strong enso air sea interaction in the west central pacific equatorial strip 5 s 5 n 156 e 140 w and d the 20 c isotherm depth anomaly averaged over the

observational evidence of winter spice injection abstract temperature and salinity t s profiles from the global array of argo floats support the existence of spice formation regions in the subtropics of each ocean basin where large destabilizing vertical salinity gradients coincide with weak stratification in winter in these characteristic regions convective boundary layer mixing generates a strongly density compensated sdc layer at the base of the well mixed layer the degree of density compensation of the t s gradients of an upper ocean water column is quantified using a bulk vertical turner angle tub between the surface and upper pycnocline the winter generation of the sdc layer in spice formation zones is clearly seen in argo data as a large amplitude seasonal cycle of tub in regions of the subtropical oceans characterized by high mean tub in formation regions argo floats provide ample evidence of large abrupt spice injection t s increase on subducted isopycnals due to vertical mixing associated with the winter increase in tub a simp

changes in the relationship nao northern hemisphere temperature due to solar activity abstract the influence of the north atlantic oscillation nao on wintertime northern hemisphere temperature nht is investigated the results suggest that this relationship has different sign according to the phase of the solar cycle for solar maximum phases nao and nht are positively correlated a result assumed up to the moment but for solar minimum phases correlations are not significant or even negative this result is in agreement with the different extension of the nao for solar cycle phases kodera geophys res lett 29 2002 14557 14560 almost hemispheric for maximum phases and confined to the eastern atlantic for minimum phases

observation of spiciness interannual variability in the pacific pycnocline monthly gridded fields predominantly based on global argo in situ temperature and salinity data are used to analyze the density compensated anomaly of salinity spiciness anomaly in the pycnocline of the subtropical and tropical pacific ocean between 2004 and 2011 interannual variability in the formation propagation and fate of spiciness anomalies are investigated the spiciness anomalies propagate on the isopycnal surface sq 25 5 along the subtropical tropical pycnocline advected by the mean currents they reach the pacific western tropics in about 5 6 years in the southern hemisphere and about 7 8 years in the northern hemisphere their amplitude strongly diminishes along the way and only very weak spiciness anomalies seem to reach the equator in the western tropics a complex eof analysis of interannual salinity anomalies on sq 25 5 highlights two dominant modes of variability at interannual scale i the former shows a variability of 5 7 years predominant in the northern hemisphere and ii the latter displays an interannual variability of 2 to 3 years more marked in the southern hemisphere the significant correlation of this second mode with enso index suggests that spiciness formation in the southeastern pacific sep is affected by enso tropical interannual variability a diagnosis of the mechanisms governing the interannual generation of spiciness in the sep region leads the authors to suggest that the spiciness interannual variability in the sub surface is linked to the equatorward migration of the isopycnal outcrop line sq 25 5 into the area of maximum salinity quantitative analysis based on turner angle reveals the dominance of the spiciness injection mechanism occurring through convective mixing at the base of mixed layer

solar cycle modulation of the north atlantic oscillation implication in the spatial structure of the nao 1 the spatial extent of the north atlantic oscillation nao is investigated the results suggest that the spatial structure of the nao differs significantly according to the phase of the solar cycle during the solar maximum phases the nao has a hemispherical structure extending into the stratosphere which is similar to the arctic oscillation ao except for the pacific sector however during the minimum phase the nao is confined to the eastern atlantic sector in the troposphere whether or not the nao is modulated by the solar cycle these results may shed new light on the controversy of the physical reality of the two modes of variability the nao and the ao

a precisely dated climate record for the last 9 kyr from three high alpine stalagmites spannagel cave austria 1 here we use the 18o time series of three stalagmites from the high alpine spannagel cave austria which grew in small distance from each other to construct a precisely dated continuous 18o curve for the last 9 kyr comnispa this speleothem record is not influenced by effects of kinetic isotope fractionation due to the low temperatures in the cave thus the variations in 18o can be interpreted in terms of past climate change comnispa exhibits several oscillations within the holocene and their timing and duration is in agreement with that documented by other alpine archives

paleoenvironmental evidence for first human colonization of the eastern caribbean abstract identifying and dating first human colonization of new places is challenging especially when group sizes were small and material traces of their occupations were ephemeral generating reliable reconstructions of human colonization patterns from intact archaeological sites may be difficult to impossible given post depositional taphonomic processes and in cases of island and coastal locations the inundation of landscapes resulting from post pleistocene sea level rise paleoenvironmental reconstruction is proving to be a more reliable method of identifying small scale human colonization events than archaeological data alone we demonstrate the method through a sediment coring project across the lesser antilles and southern caribbean paleoenvironmental data were collected informing on the timing of multiple island colonization events and land use histories spanning the full range of human occupations in the caribbean from the initial forays into the islands through the arrival and eventual domination of the landscapes and indigenous people by europeans in some areas our data complement archaeological paleoecological and historical findings from the lesser antilles and in others amplify understanding of colonization history here we highlight data relating to the timing and process of initial colonization in the eastern caribbean in particular paleoenvironmental data from trinidad grenada martinique and marie galante guadeloupe provide a basis for revisiting initial colonization models of the caribbean we conclude that archaeological programs addressing human occupations dating to the early to mid holocene especially in dynamic coastal settings should systematically incorporate paleoenvironmental investigations

southward migration of the intertropical convergence zone through the holocene titanium and iron concentration data from the anoxic cariaco basin off the venezuelan coast can be used to infer variations in the hydrological cycle over northern south america during the past 14 000 years with subdecadal resolution following a dry younger dryas a period of increased precipitation and riverine discharge occurred during the holocene thermal maximum since approximately 5400 years ago a trend toward drier conditions is evident from the data with high amplitude fluctuations and precipitation minima during the time interval 3800 to 2800 years ago and during the little ice age these regional changes in precipitation are best explained by shifts in the mean latitude of the atlantic intertropical convergence zone itcz potentially driven by pacific based climate variability the cariaco basin record exhibits strong correlations with climate records from distant regions including the high latitude northern hemisphere providing evidence for global teleconnections among regional climates

investigation of the stable isotope fractionation in speleothems with laboratory experiments many speleothems show evidence for calcite precipitation under disequilibrium conditions to improve the understanding of these kinetic processes several laboratory experiments were performed to study the fractionation of stable oxygen and carbon isotopes during the precipitation of calcite carbonate was precipitated under controlled conditions from both a body of standing water beaker experiments and a solution flowing along a channel channel experiments at a relative humidity of 100 slow degassing of co2 simulated by the beaker experiments results in 18o values in equilibrium with the solution in contrast the 13c values show a significant enrichment inversely proportional to the height of the solution in the beakers fast degassing of co2 simulated by the channel experiments showed an enrichment of both 13c and 18o and a slope of 13c 18o of 1 4 0 6 these results represent experimental evidence for the hendy effect which is manifested in i a progressive increase in 18o and 13c away from the growth axis and ii a positive correlation between 18o and 13c along a single growth layer of a stalagmite

holocene forcing of the indian monsoon recorded in a stalagmite from southern oman a high resolution oxygen isotope record from a thorium uranium dated stalagmite from southern oman reflects variations in the amount of monsoon precipitation for the periods from 10 3 to 2 7 and 1 4 to 0 4 thousand years before the present ky b p between 10 3 and 8 ky b p decadal to centennial variations in monsoon precipitation are in phase with temperature fluctuations recorded in greenland ice cores indicating that early holocene monsoon intensity is largely controlled by glacial boundary conditions after approximately 8 ky b p monsoon precipitation decreases gradually in response to changing northern hemisphere summer solar insolation with decadal to multidecadal variations in monsoon precipitation being linked to solar activity

poleward propagation of spiciness anomalies in the north atlantic ocean 1 recent modelling results suggest that subsurface salinity anomalies propagating from the tropics can reach and precondition the deep water formation regions thus modulating the thc variability the forcing and propagative aspects of this mechanism are presented in the north atlantic ocean over 1948 2002 using an ogcm density compensated salinity anomalies of 0 1 up to 0 35 psu along s 26 kg m 3 are generated in the salinity maximum region at interannual to decadal frequency the relation between subsurface conditions and late winter sea surface salinity variability supports the subduction mechanism they circulate over isopycnals ranging from 25 6s to 26 2s at current speed between 150 m and 250 m depth toward cape hatteras via the gulf of mexico on a typical 6 year transit although mixing along the pathway reduces the amplitude of salinity anomalies by about 66 they largely determine the subsurface spiciness of the gulf stream up to 30 n upstream of the outcrop region citation laurian a a lazar g reverdin k rodgers and p terray 2006 poleward propagation of spiciness anomalies in the north atlantic ocean geophys res lett 33 l13603

late winter generation of spiciness on subducted isopycnals the origins of density compensating anomalies of temperature and salinity spice are investigated using a model forced with the most realistic surface products available over the 40 years 1958 97 in this hindcast the largest interannual spiciness anomalies are found in the pacific ocean near the isopycnal s 0 5 25 5 where deviations as great as 1 28c and 0 6 psu are generated equatorward of winter outcropping in the eastern subtropics in both hemispheres these source regions are characterized by very unstable salinity gradients and low mean density stratification in winter two related signatures of winter mixing in the southeast pacific sep are density that is well mixed deeper than either temperature or salinity and subsurface density ratios that approach 1 all ocean basins in the model are shown to have regions with these characteristics and signatures however the resultant spiciness signals are focused on different isopycnals ranging from s 0 5 25 0 in the northeast pacific to s 0 5 26 5 in the south indian ocean a detailed examination of the sep finds that large positive anomalies are generated by diapycnal mixing across subducted isopycnals e g s 0 5 25 5 whereas negative anomalies are the result of a steady isopycnal advection moderated by vertical advection and heave there is considerable interannual variability in the strength of anomalies and in the density on which they occur historical observations are consistent with the model results but are insufficient to verify all aspects of the hindcast including the processes of anomaly generation in the sep it was not possible to relate isopycnal anomaly genesis to local surface forcing of any kind a complex scenario involving basinwide circulation of both the ocean and atmosphere especially of surface water through the subtropical evaporation zones is put forward to explain the decadal time scale evident in sep salinity anomalies on s 0 5 25 5 pacific anomalies generated on s 0 5 25 5 can be traced along mean geostrophic streamlines to the western boundary where decadal salinity variations at 78s are about 2 times as large order 60 1 psu as at 128n although there may be more variance on shallower isopycnals in the north at least portions of the s 0 5 25 5 signals appear to continue along the boundary to a convergence at the equator suggesting that the most robust sources of pacific spiciness variance coincide with equatorial exchange pathways

new cnes cls09 global mean dynamic topography computed from the combination of grace data altimetry and in situ measurements 1 an accurate knowledge of the ocean mean dynamic topography mdt is mandatory for the optimal use of altimetric data including their assimilation into operational ocean forecasting systems a new global 1 4 resolution mdt was computed for the 1993 1999 time period with improved data and methodology compared to the previous rio05 mdt field first a large scale mdt is obtained from the cls01 altimetric mean sea surface and a recent geoid model computed from 4 5 years of grace gravity recovery and climate experiment data altimetric sea level anomalies and in situ measurements are then combined to compute synthetic estimates of the mdt and the corresponding mean currents while the rio05 mdt was based on 10 years of in situ dynamic heights and drifting buoy velocities the new field benefits from an enlarged data set of in situ measurements ranging from 1993 to 2008 and includes all hydrological profiles from the argo array moreover the processing of the in situ data has been updated a new ekman model was developed to extract the geostrophic velocity component from the drifting buoy measurements the handling of hydrologic measurements has also been revisited compared to the previous rio05 solution the new global mdt resolves much stronger gradients in western boundary currents with mean velocities being doubled in some places moreover in comparison to several other recent mdt estimates we find that the new cnes cls09 mdt is in better agreement with independent in situ observations

generation of low frequency spiciness variability in the thermocline abstract the generation of variance by anomalous advection of a passive tracer in the thermocline is investigated using the example of density compensated temperature and salinity anomalies or spiciness a coupled markov model is developed in which wind stress curl forces the large scale baroclinic ocean pressure that in turn controls the anomalous geostrophic advection of spiciness the double integration of white noise atmospheric forcing by this markov model results in a frequency spectrum of large scale spiciness proportional to 4 so that spiciness variability is concentrated at low frequencies an eddy permitting regional model hindcast of the northeast pacific 1950 2007 confirms that time series of large scale spiciness variability are exceptionally smooth with frequency spectra 4 for frequencies greater than 0 2 cpy at shorter spatial scales wavelengths less than 500 km the spiciness frequency spectrum is whitened by mesoscale eddies but this eddy forced variability can be fi

stable isotope variations in modern tropical speleothems evaluating equilibrium vs kinetic isotope effects applications of speleothem calcite geochemistry in climate change studies require the evaluation of the accuracy and sensitivity of speleothem proxies to correctly infer paleoclimatic information the present study of harrison s cave barbados uses the analysis of the modern climatology and groundwater system to evaluate controls on the c and o isotopic composition of modern speleothems this new approach directly compares the 18 o and 13 c values of modern speleothems with the values for their corresponding drip waters in order to assess the degree to which isotopic equilibrium is achieved during calcite precipitation if modern speleothems can be demonstrated to precipitate in isotopic equilibrium then ancient speleothems suitable for paleoclimatic studies from the same cave environment may also have been precipitated in isotopic equilib rium if modern speleothems are precipitated out of isotopic equilibrium then the magnitude and direction of the c and o isotopic offsets may allow specific kinetic and or equilibrium isotopic fractionation mechanisms to be identified carbon isotope values for the majority of modern speleothem samples from harrison s cave fall within the range of equilibrium values predicted from the combined use of 1 calcite water fractionation factors from the literature 2 measured temperatures and 3 measured 13 c values of the dissolved inorganic carbon of drip waters calcite samples range from 0 8 higher to 1 1 lower than predicted values the 13 c depletions are likely caused by kinetically driven departures in the fractionation between hco3 aq and caco3 from equilibrium conditions caused by rapid calcite growth 13 c enrichments can be accounted for by rayleigh distillation of the hco3 aq reservoir during degassing of 13 c depleted co2 modern speleothems from harrison s cave are not in o isotopic equilibrium with their corresponding drip waters and are 0 2 to 2 3 enriched in 18 o relative to equilibrium values 18 o variations in modern calcite are likely controlled by kinetically driven changes in the fractionation between hco3 aq and caco3 from equilibrium conditions to nonequilibrium conditions consistent with rapid calcite growth in contrast to 13 c 18 o values of modern calcite may not be affected by rayleigh distillation during degassing because co2 hydration and hydroxylation reactions will buffer the o isotopic composition of the hco3 aq reservoir if the effects of rayleigh distillation manifest themselves in the o isotopic system they will result in 18 o enrichment in the hco3

observations of decadal time scale salinity changes in the subtropical thermocline of the north pacific ocean abstract data from argo floats indicate that significant salinity changes have occurred in the north pacific thermocline relative to data collected in the previous two decades including observations obtained as part of the woce hydrographic program such a salinity decrease on both isopyncals and isobars implies a freshening scenario in the near surface source region of this water mass the frequently repeated meridional section p16 supports this inference the subsurface salinity freshening likely began in the early 1990s strengthened through 1997 and continued into the 2000s the surface salinity freshening had commenced by 1984 and continued through the first decade of the 21st century the spatial distribution of salinity change on the density surface 25 5 is examined through comparisons of argo and most of the north pacific woce sections 1985 1994 and between argo and the hydrobase climatology largely composed of data from the late 1970s through the mid 1980s both comparisons show a large scale basin wide decrease in subsurface salinity through the argo time period used in this analysis 2003 2006 the salinity difference is maximum in the northeast area and spreads southward and westward approximately following geostrophic streamlines

climatology and seasonality of upper ocean salinity a three dimensional view from argo floats primarily due to the constraints of observation technologies both field and satellite measurements our understanding of ocean salinity is much less mature compared to ocean temperature as a result the characterizations of the two most important properties of the ocean are unfortunately out of step the former is one generation behind the latter in terms of data availability and applicability this situation has been substantially changed with the advent of the argo floats which measure the two variables simultaneously on a global scale since early this century the first decade of argo acquired salinity data are analyzed here in the context of climatology and seasonality yielding the following main findings for the global upper oceans first the six well defined salty pools observed around 20 in each hemisphere of the pacific atlantic and indian oceans are found to tilt westward vertically from the sea surface to about 600 m depth forming six saline cores within the subsurface oceans second while potential temperature climatology decreases monotonically to the bottom in most places of the ocean the vertical distribution of salinity can be classified into two categories a double halocline type forming immediately above and below the local salinity maximum around 100 150 m depths in the tropical and subtropical oceans and a single halocline type existing at about 100 m depth in the extratropical oceans third in contrast to the midlatitude dominance for temperature seasonal variability of salinity in the oceanic mixed layer has a clear tropical dominance meanwhile it is found that a two mode structure with annual and semiannual periodicities can effectively penetrate through the upper ocean into a depth of 2000 m fourth signature of rossby waves is identified in the annual phase map of ocean salinity within 200 600 m depths in the tropical oceans revealing a strongly co varying nature of ocean temperature and salinity at specific depths these results serve as significant contributions to improving our knowledge on the haline aspect of the ocean climate

formation mechanism for isopycnal temperature salinity anomalies propagating from the eastern south pacific to the equatorial region abstract equatorward propagation of temperature salinity or spiciness anomalies on an isopycnal surface emanating from the eastern subtropical south pacific and their formation mechanism are investigated based on a hindcast simulation with an eddy resolving quasi global ocean general circulation model because of density compensating meridional distributions of temperature and salinity the meridional density gradient is weak at the sea surface in the eastern subtropical south pacific with these mean fields cool sea surface temperature anomalies sstas can make the outcrop line of an isopycnal surface migrate equatorward more than 5 and induce warm and salty anomalies on the isopycnal surface subducted warm salty anomalies propagate to the equatorial region over approximately 5 yr and may influence equatorial isopycnal temperature salinity anomalies although the associated effects are unclear if these anomalies could further induce warm eastern equatorial sstas that are positively correlated wit