recent progress in snow and ice research a review of snow and ice research in 1987 1990 is presented focusing on the effects of layers in seasonal snow covers ice mechanics on fresh water and sea ice and remote sensig of polar ice sheets these topics provide useful examples of general needs in snow and ice research applicable to most areas such as better representation in models of detailed processes controlled laboratory experiments to quantify processes and field studies to provide the appropriate context for interpretation of processes from remote sensing

palaeoclimatic implications of the occurrence of the arcoid bivalve anadara trapezia deshayes in the quaternary of australasia abstract the arcoid bivalve anadara trapezia deshayes 1840 is a eurythermal estuarine mollusc that flourishes at present in eastern australia between port phillip bay victoria and townsville in northern queensland a trapezia first appeared in the australian quaternary fossil record during oxygen isotope stage ois 7 in new zealand where it is now extinct the earliest known occurrences are in the rangitawa fossil beds and in uppermost castlecliffian strata west of wanganui north island ois 11 ca 400 ka the species had an extensive distribution during the last interglacial maximum ois 5e in both australia and new zealand and appears to have had a slightly wider than present geographic range in southeastern australia during the middle holocene as shown by records from tasmania and western victoria where it no longer lives apart from an isolated population inhabiting oyster harbour western australia a trapezia has not been confirmed living in coastal waters west of port phillip bay victoria it became extinct in new zealand sometime after ois 5e the extensive distribution and abundance of a trapezia and other fauna of subtropical affinity during the last interglacial maximum in areas where both are now extinct appears to be associated with an enhanced leeuwin current at that time coinciding with higher less seasonally concentrated levels of precipitation and river discharge the arrival of a trapezia in australasian coastal waters may have been a consequence of planktonic dispersal from southern south america a bravardi del rio from the middle miocene puerto madryn formation on the valdes peninsula argentina may be a possible ancestor for a trapezia

estimating the mean areal snow water equivalent by integration in time and space by modelling the snow accumulation process in time and space as sums of random gamma distributed variables the mean areal snow water equivalent swe can be estimated in the methodology we make use of the fact that sums of gamma distributed variables with a certain set of parameters also are gamma distributed variables with parameters being functions of the original and the number of summations the measured snow swe at a point and at a certain time t can thus be seen as the accumulation or the sum of snowfall events from the beginning of the snowfall season up to t the integration of these points over an area can be seen as another summation from snow pillows and precipitation gauges the value of daily accumulated precipitation snow has been found to be well represented by a two parameter gamma distribution this distribution has been found to be representative for large areas the number of events where the precipitation was accumulated can be estimated from snow pillows situated in the area the mean snow coverage over an area which represents the summation of the individual points over an area can be derived from satellite images represented in a gis the methodology is tested for two nested catchments of size 4723 km 2 and 19 832 km 2 in a mountainous area in southern norway for ten satellite scenes the results are compared with simulated snow reservoirs using a rainfall runoff model and found to agree well large discrepancies in the snow reservoirs reservoirs using a rainfall runoff model and found to agree well large discrepancies in the snow reservoirs between the proposed method and the rainfall runoff model are found in late spring and are probably due to errors in the estimated mean snow coverage derived from the satellite images

late pleistocene landscape response to climate change eolian and alluvial fan deposition cape liptrap southeastern australia abstract sea cliffs along the western coast of cape liptrap at arch rock provide nearly continuous exposure of calcareous eolianites dated at 68 112 ka five optically stimulated luminescence osl ages calcareous eolian deposition began immediately after the last interglacial marine highstand oxygen isotope stage ois 5e and continued during sea level fall until the beginning of ois 4 west southwesterly winds transported calcareous sand across 12 km of exposed continental shelf by the beginning of ois 4 a brief period of cold arid windy continental climate with ephemeral but intense surface runoff immediately preceded the last glacial maximum lgm this resulted in fluvial reworking of the calcarenites into an alluvial fan dated at 23 25 ka four osl ages the fan overlies peat dated at 25 279 yr cal bp and is capped by a paleosol dated at 6010 yr cal bp concurrent eolian reworking by northwesterly winds of siliceous sediments on marine terraces along the eastern and central portion of cape liptrap formed siliceous longitudinal dunes with ages ranging from 19 to 24 ka five osl ages the phase of maximum landscape instability at cape liptrap coincides with solar insolation and air temperature minima and preceded the lgm by several thousand years

an analysis of snow cover patterns in a small alpine catchment snow cover patterns in a 9 4 km2 basin in the austrian alps are examined during spring and summer 1989 digital mono plotting from oblique aerophotographs is used for mapping on the basis of a square grid with 25 m spacing snow cover as mapped during nine surveys is analysed as a function of elevation and slope during winter conditions the snow cover is found to be much better related to these terrain features than during the late ablation period

impact of the equatorial atlantic on the el nino southern oscillation observations indicate that the atlantic zonal mode influences el nino southern oscillation enso in the pacific as already suggested in previous studies here we demonstrate for the first time using partial coupled experiments that the atlantic zonal mode indeed influences enso the partial coupling experiments are performed by forcing the coupled general circulation model echam5 mpi om with observed sea surface temperature sst in the tropical atlantic but with full air sea coupling allowed in the pacific and indian ocean the ensemble mean of a five member simulation reproduces the observational results well analysis of observations reanalysis and coupled model simulations all indicate the following mechanism sst anomalies associated with the atlantic zonal mode affect the walker circulation driving westward wind anomalies over the equatorial pacific during boreal summer the wind stress anomalies increase the east west thermocline slope and enhance the sst gradient across the pacific the bjerknes positive feedback acts to amplify these anomalies favouring the development of a la nina like anomalies the same mechanisms act for the cold phase of atlantic zonal mode but with opposite sign in contrast to previous studies the model shows that the influence on enso exists before 1970 furthermore no significant influence of the tropical atlantic on the indian monsoon precipitation is found in observation or model

tropical atlantic variability modes 1979 2002 part ii time evolving atmospheric circulation related to sst forced tropical convection abstract the ways in which deep convection over the tropical atlantic affects the midlatitude climate variability through meridional circulation planetary wave teleconnection and wave mean flow interaction is examined for the 1979 2002 period by following the north atlantic anomalous rainfall evolution from summer to late winter in this way the first two covariability modes between anomalous summer tropical atlantic sea surface temperature sst and anomalous summer late winter precipitation over the north atlantic basin are analyzed using the same methodology of extended maximum covariance analysis developed for part i this work updates the results given by other authors whose studies are based on different datasets dating back to the 1950s to this end the climate prediction center cpc merged analysis of precipitation cmap dataset which includes measures over the ocean is used to give a complete picture of the interannual rainfall patterns for the last decades the first mode which accoun

is the boreal spring tropical atlantic variability a precursor of the equatorial mode the equatorial mode em governs the tropical atlantic inter annual variability during boreal summer it has profound impacts on the climate of adjacent and remote areas however predicting the em is one of the most challenging and intriguing issues for the scientific community recent studies have suggested a possible connection between the boreal spring meridional mode mm and the em through ocean wave propagation here we use a set of sensitivity experiments with a medium resolution ocean model to determine the precursor role of a mm to create equatorial sst variability our results demonstrate that boreal summer equatorial ssts following a mm are subject to two counteracting effects the local wind forcing and remotely excited oceanic waves for a positive mm the anomalous easterly winds blowing along the equator shallow the thermocline cooling the sea surface via vertical diffusion and meridional advection anomalous wind curl excites a downwelling rossby wave north of equator which is reflected at the western boundary becoming an equatorial kelvin wave kw this downwelling kw propagates eastward deepening the thermocline and activating the thermocline feedbacks responsible for the equatorial warming moreover the local wind forcing and rw reflected mechanism have a significant and comparable impact on the equatorial sst variability changes in the intensity and persistence of these distinct forcings will determine the equatorial sst response during boreal summer our results give a step forward to the improvement of the em predictability

sea surface temperature in the north tropical atlantic as a trigger for el nino southern oscillation events the el nino southern oscillation in the pacific ocean influences temperature in other tropical ocean basins reanalysis data and model simulations suggest that temperature anomalies in the north tropical atlantic may also influence the development of la nina events

stable isotope record and its palaeoenvironmental interpretation for a late middle pleistocene speleothem from victoria fossil cave naracoorte south australia abstract a speleothem from victoria fossil cave south australia provides a continuous stable isotope record from 185 to 157 ka oxygen isotope analysis indicates that at commencement of deposition mean annual temperatures were much lower than at present and that between 178 and 162 ka regional surface temperatures were similar to today such high temperatures during an interstadial are surprising but may be attributable to increased continentality due to low sealevels carbon isotope analysis indicates the presence of an active vegetation cover dominated by c3 plants during the interstadial while a sparse vegetation dominated by c4 grasses appears to have been dominant during full glacial conditions variations in moisture availability and vegetation productivity are probably closely related to stages in the precessional cycle

processes in the pacific la nina onset triggered by the atlantic nino previous observational and model studies have shown that a warm cold event in the equatorial atlantic during the boreal summer are related to the development of a pacific la nina el nino event that is fully developed in the following winter although the connection takes place via atmospheric bridge the processes at work have not been clarified for such a remote and lagged relationship the present paper uses a partially coupled atmosphere ocean model to infer a mechanism by which a pacific el nino event can be developed in this way enhanced equatorial convection in the equatorial atlantic during a warm event results in enhanced subsidence and surface wind divergence over the equatorial pacific around the dateline this wind anomaly contributes to pile up water in the western equatorial pacific triggering a perturbation in the depth of the oceanic thermocline which propagates eastward as an equatorial kelvin wave from autumn to winter the thermocline shallowing as the wave propagates allows for cooling of the oceanic mixed layer through anomalous temperature advection by anomalous zonal currents and by mean vertical entrainment velocity zonal advective and thermocline feedbacks reinforce the surface winds anomalies over the central eastern equatorial pacific setting up the conditions for the development of a cold event in this ocean the sequence during an atlantic cold event is similar with the appropriate change in signs these findings are relevant to enso predictability at seasonal timescales

on the origin of equatorial atlantic biases in coupled general circulation models many coupled ocean atmosphere general circulation models gcms suffer serious biases in the tropical atlantic including a southward shift of the intertropical convergence zone itcz in the annual mean a westerly bias in equatorial surface winds and a failure to reproduce the eastern equatorial cold tongue in boreal summer the present study examines an ensemble of coupled gcms and their uncoupled atmospheric component to identify common sources of error it is found that the westerly wind bias also exists in the atmospheric gcms forced with observed sea surface temperature but only in boreal spring during this time sea level pressure is anomalously high low in the western eastern equatorial atlantic which appears to be related to deficient excessive precipitation over tropical south america africa in coupled simulations this westerly bias leads to a deepening of the thermocline in the east which prevents the equatorial cold tongue from developing in boreal summer thus reducing atmospheric model errors during boreal spring may lead to improved coupled simulations of tropical atlantic climate

aminostratigraphy of quaternary coastal sequences in southern australia an overview abstract since the early 1980s amino acid racemisation reactions have been applied to the dating of quaternary coastal deposits in australia sequences of middle pleistocene age or younger have received the greatest attention amino acid racemisation has been applied as a relative and numeric dating method as well as for identifying remanie fossils and in delineating the spatial distribution of some fossil mollusc species the method has also been used to verify the radiocarbon ages of fossil molluscs from interstadial sediments it has also been used in studies of coastal neotectonics and in comparisons with other dating methods e g electron spin resonance and thermoluminescence the most reliable results are from replicate analyses of the hinge region of well preserved and diagenetically unmodified fossil bivalve molluscs from deeply buried situations i e 1 m molluscs have been dated from a range of sites around the southern australian coastline and include specimens of plio pleistocene age and from middle pleistocene oxygen isotope stage 7 ca 220 ka bp late pleistocene substage 5e ca 125 ka bp interstadial stage 3 45 to 30 ka bp last glacial stage 2 ca 18 ka bp and holocene sequences amino acid racemisation dating of the australian quaternary coastal record has 1 confirmed the widespread occurrence of last interglacial coastal strata and allowed their correlation with sequences of equivalent age from the northern hemisphere 2 identified strata of penultimate interglacial age and 3 confirmed the interstadial age of marine strata stage 3 in gulf st vincent south australia aminostratigraphic studies of the southern australian quaternary coastal record also indicate that sea levels during the penultimate interglacial stage 7 may have been higher than otherwise predicted on the basis of the oxygen isotope record

an equatorial extratropical dipole structure of the atlantic nino abstractequatorial atlantic variability is dominated by the atlantic nino peaking during the boreal summer studies have shown robust links of the atlantic nino to fluctuations of the st helena subtropical anticyclone and benguela nino events furthermore the occurrence of opposite sea surface temperature sst anomalies in the eastern equatorial and southwestern extratropical south atlantic ocean sao also peaking in boreal summer has recently been identified and termed the sao dipole saod however the extent to which and how the atlantic nino and saod are related remain unclear here an analysis of historical observations reveals the atlantic nino as a possible intrinsic equatorial arm of the saod specifically the observed sporadic equatorial warming characteristic of the atlantic nino 0 4 k is consistently linked to southwestern cooling 0 4 k of the atlantic ocean during the boreal summer heat budget calculations show that the saod is largely driven by the surface net heat flux anoma

enso influence on the atlantic nino revisited multi year versus single year enso events abstractthe influence of el nino southern oscillation enso on the atlantic nino over the past 113 years is investigated by comparing multi year and single year enso events multi year enso events

influence of the meridional overturning circulation on tropical atlantic climate and variability abstract the influence of the meridional overturning circulation on tropical atlantic climate and variability has been investigated using the atmosphere ocean coupled model speedy micom miami isopycnic coordinate ocean model in the ocean model micom the strength of the meridional overturning cell can be regulated by specifying the lateral boundary conditions in case of a collapse of the basinwide meridional overturning cell the sst response in the atlantic is characterized by a dipole with a cooling in the north atlantic and a warming in the tropical and south atlantic the cooling in the north atlantic is due to the decrease in the strength of the western boundary currents which reduces the northward advection of heat the warming in the tropical atlantic is caused by a reduced ventilation of water originating from the south atlantic this effect is most prominent in the eastern tropical atlantic during boreal summer when the mixed layer attains its minimum depth as a consequence the seasonal cycle

equatorial atlantic variability and its relation to mean state biases in cmip5 coupled general circulation model gcm simulations participating in the coupled model intercomparison project phase 5 cmip5 are analyzed with respect to their performance in the equatorial atlantic in terms of the mean state 29 out of 33 models examined continue to suffer from serious biases including an annual mean zonal equatorial sst gradient whose sign is opposite to observations westerly surface wind biases in boreal spring play an important role in the reversed sst gradient by deepening the thermocline in the eastern equatorial atlantic and thus reducing upwelling efficiency and sst cooling in the following months both magnitude and seasonal evolution of the biases are very similar to what was found previously for cmip3 models indicating that improvements have only been modest the weaker than observed equatorial easterlies are also simulated by atmospheric gcms forced with observed sst they are related to both continental convection and the latitudinal position of the intertropical convergence zone itcz particularly the latter has a strong influence on equatorial zonal winds in both the seasonal cycle and interannual variability the dependence of equatorial easterlies on itcz latitude shows a marked asymmetry from the equator to 15 n the equatorial easterlies intensify approximately linearly with itcz latitude when the itcz is south of the equator on the other hand the equatorial easterlies are uniformly weak despite serious mean state biases several models are able to capture some aspects of the equatorial mode of interannual sst variability including amplitude pattern phase locking to boreal summer and duration of events the latitudinal position of the boreal spring itcz through its influence on equatorial surface winds appears to play an important role in initiating warm events

interhemispheric influence of the atlantic warm pool on the southeastern pacific abstract the atlantic warm pool awp is a large body of warm water comprising the gulf of mexico caribbean sea and western tropical north atlantic the awp can vary on seasonal interannual and multidecadal time scales the maximum awp size is in the boreal late summer and early fall with the largest extent in the year being about 3 times the smallest one the awp alternates with the amazon basin in south america as the seasonal heating source for circulations of the hadley and walker type in the western hemisphere during the boreal summer fall a strong hadley type circulation is established with ascending motion over the awp and subsidence over the southeastern tropical pacific this is accompanied by equatorward flow in the lower troposphere over the southeastern tropical pacific as dynamically required by the sverdrup vorticity balance it is shown by analyses of observational data and ncar community atmospheric model simulations that an anomalously large small awp during the boreal summer f

decadal interactions between the western tropical pacific and the north atlantic oscillation the relationship between interdecadal variations of tropical sea surface temperature sst in the last 120 years and circulation anomalies related to the north atlantic oscillation nao is investigated in this study using an atmospheric general circulation model agcm we confirm observational evidence that variations in the sst gradient in the western tropical pacific are related to the nao anomalies on decadal timescale and may be contributing to the shift towards the positive nao phase observed in the late 20th century the role played by the indian ocean nao teleconnection advocated in recent studies focused on the last 50 years is also assessed in the context of the 120 year long record it is suggested that a positive feedback between the pacific sst and the hemispheric circulation pattern embedding the decadal nao signal may act to enhance the internal variability of the coupled ocean atmosphere system and justify the stronger teleconnection found in observational data than in sst forced agcm experiments

interactive feedback between enso and the indian ocean abstract a feedback process of the indian ocean sst on enso is investigated by using observed data and atmospheric gcm it is suggested that warming in the indian ocean produces an easterly wind stress anomaly over indonesia and the western edge of the pacific during the mature phase of el nino the anomalous easterly wind in the western pacific during el nino helps a rapid termination of el nino and a fast transition to la nina by generating upwelling kelvin waves thus warming in the indian ocean which is a part of the el nino signal operates as a negative feedback mechanism to enso this indian ocean feedback appears to operate mostly for relatively strong el ninos and results in a la nina one year after the mature phase of the el nino this 1 yr period of phase transition implies a possible role of indian ocean enso coupling in the biennial tendency of the enso atmospheric gcm experiments show that indian ocean sst forcing is mostly responsible for the easterly wind anomalies in the western pacific

tropical response to the atlantic equatorial mode agcm multimodel approach on the frame of the amma eu project sensitivity experiments for an atlantic equatorial mode aem which origin development and damping resembles the observed one during the last decades of the 20th century has been analysed in order to investigate the influence on the anomalous summer west african rainfall recent studies raise the matter of the aem influence on the next pacific enso episodes and also on the indian monsoon this paper evaluates the response of four different atmospheric global circulation models using the above mentioned aem sensitivity experiments to study the tropical forcing associated with the atlantic nino mode the results show a remote signal in both the pacific and indian basins for a warm phase of the aem the associated southward location of the itcz with rising motions over the equatorial atlantic leads to a global subsidence over the rest of the tropics weakening the asian monsoon and favouring the la nina conditions in the central pacific although ocean atmosphere coupled experiments are required to test the latter hypothesis the present studies shows how the aem is able to influence the rest of the tropics a result with important implications on enso seasonal predictability

tropical atmospheric response to decadal changes in the atlantic equatorial mode it has been shown that the atmospheric response to the atlantic equatorial mode is non stationary after the 1970s sea surface temperature sst anomalies in the tropical atlantic are able to alter the atmosphere in the tropical pacific via modifications of the walker circulation such changes could be related to the differences in the background state of the global ssts before and after the 1970s but also to changes in the interannual equatorial mode itself in this work we first describe the differences in the interannual equatorial mode before and after the 1970s then we use two agcms to perform different sensitivity experiments changing the spatial structure of the equatorial mode and we explore the differences in the atmospheric response over the tropical pacific region to each of the sst patterns considered it is shown that the changes in the walker atlantic pacific cell produced by the em are stronger after the 1970s and are reinforced by the change in the impact of the em over the indian ocean and the maritime continent it is also shown that although the atlantic pacific connection is established by the aforementioned changes in the walker circulation between the two basins the modulation of the indian sector is crucial for a realistic simulation of such connection by climate models

influence of the state of the indian ocean dipole on the following year s el nino el nino southern oscillation enso consists of irregular episodes of warm el nino and cold la nina conditions in the tropical pacific ocean 1 with significant global socio economic and environmental impacts 1 nevertheless forecasting enso at lead times longer than a few months remains a challenge 2 3 like the pacific ocean the indian ocean also shows interannual climate fluctuations which are known as the indian ocean dipole 4 5 positive phases of the indian ocean dipole tend to co occur with el nino and negative phases with la nina 6 9 here we show using a simple forecast model that in addition to this link a negative phase of the indian ocean dipole anomaly is an efficient predictor of el nino 14 months before its peak and similarly a positive phase in the indian ocean dipole often precedes la nina observations and model analyses suggest that the indian ocean dipole modulates the strength of the walker circulation in autumn the quick demise of the indian ocean dipole anomaly in november december then induces a sudden collapse of anomalous zonal winds over the pacific ocean which leads to the development of el nino la nina our study suggests that improvements in the observing system in the indian ocean region and better simulations of its interannual climate variability will benefit enso forecasts

tropical atlantic variability modes 1979 2002 part i time evolving sst modes related to west african rainfall abstract this work presents a description of the 1979 2002 tropical atlantic ta sst variability modes coupled to the anomalous west african wa rainfall during the monsoon season the time evolving sst patterns with an impact on wa rainfall variability are analyzed using a new methodology based on maximum covariance analysis the enhanced climate prediction center cpc merged analysis of precipitation cmap dataset which includes measures over the ocean gives a complete picture of the interannual wa rainfall patterns for the sahel dry period the leading ta sst pattern related to the atlantic el nino is coupled to anomalous precipitation over the coast of the gulf of guinea which corresponds to the second wa rainfall principal component the thermodynamics and dynamics involved in the generation development and damping of this mode are studied and compared with previous works the sst mode starts at the angola benguela region and is caused by alongshore wind anomalies it then propagates wes

indian ocean sea surface temperature and el nino southern oscillation a new perspective abstract here the 1976 77 climate regime shift that was accompanied by a remarkable change in the lead lag relationships between indian ocean sea surface temperature sst and el nino evolution is shown after the 1976 77 regime shift a correlation analysis suggests that southern indian ocean ssts observed during late boreal winter are a key precursor in predicting el nino evolution as the traditional oceanic heat content anomalies in the equatorial pacific or zonal wind anomalies over the equatorial western pacific the possible physical mechanisms underlying this highly significant statistical relationship are discussed after the 1976 77 regime shift southern indian ocean sst anomalies produced by mascarene high pulses during boreal winter trigger coupled air sea processes in the tropical eastern indian ocean during the following seasons this produces a persistent remote forcing on the pacific climate system promoting wind anomalies over the western equatorial pacific and modulating the regional ha

snow accumulation distribution inferred from time lapse photography and simple modelling the spatial and temporal distribution of snow accumulation is complex and significantly influences the hydrological characteristics of mountain catchments many snow redistribution processes such as avalanching slushflow or wind drift are controlled by topography but their modelling remains challenging in situ measurements of snow accumulation are laborious and generally have a coarse spatial or temporal resolution in this respect time lapse photography shows itself as a powerful tool for collecting information at relatively low cost and without the need for direct field access in this paper the snow accumulation distribution of an alpine catchment is inferred by adjusting a simple snow accumulation model combined with a temperature index melt model to match the modelled melt out pattern evolution to the pattern monitored during an ablation season through terrestrial oblique photography the comparison of the resulting end of winter snow water equivalent distribution with direct measurements shows that the achieved accuracy is comparable with that obtained with an inverse distance interpolation of the point measurements on average over the ablation season the observed melt out pattern can be reproduced correctly in 93 of the area visible from the fixed camera the relations between inferred snow accumulation distribution and topographic variables indicate large scatter however a significant correlation with local slope is found and terrain curvature is detected as a factor limiting the maximal snow accumulation copyright 2010 john wiley sons ltd

southern hemisphere extra tropical forcing a new paradigm for el nino southern oscillation the main goal of this paper is to shed additional light on the reciprocal dynamical linkages between mid latitude southern hemisphere climate and the el nino southern oscillation enso signal while our analysis confirms that enso is a dominant source of interannual variability in the southern hemisphere it is also suggested here that subtropical dipole variability in both the southern indian and atlantic oceans triggered by southern hemisphere mid latitude variability may also provide a controlling influence on enso in the equatorial pacific this subtropical forcing operates through various coupled air sea feedbacks involving the propagation of subtropical sea surface temperature sst anomalies into the deep tropics of the atlantic and indian oceans from boreal winter to boreal spring and a subsequent dynamical atmospheric response to these sst anomalies linking the three tropical basins at the beginning of the boreal spring this atmospheric response is characterized by a significant weakening of the equatorial atlantic and indian inter tropical convergence zone itcz this weakened itcz forces an equatorial cold kelvin wave response in the middle to upper troposphere that extends eastward from the heat sink regions into the western pacific by modulating the vertical temperature gradient and the stability of the atmosphere over the equatorial western pacific ocean this kelvin wave response promotes persistent zonal wind and convective anomalies over the western equatorial pacific which may trigger el nino onset at the end of the boreal winter these different processes explain why south atlantic and indian subtropical dipole time series indices are highly significant precursors of the nino34 sst index several months in advance before the el nino onset in the equatorial pacific this study illustrates that the atmospheric internal variability in the mid latitudes of the southern hemisphere may significantly influence enso variability however this surprising relationship is observed only during recent decades after the so called 1976 1977 climate regime shift suggesting a possible linkage with global warming or decadal fluctuations of the climate system

morphology and origin of coastal karst landforms in miocene and quaternary carbonate rocks along the central western coast of sardinia italy in the area of punta funtanas arbus central west sardinia some small surfaces of miocene limestones crop out partially covered with quaternary calcarenites and plio quaternary basalts the biggest of these outcrops forms a fossil wave cut shore platform of up to 50 m wide with an altitude above sea level of approximately 4 5 m on this platform a wide variety of dissolution landforms can be observed these morphologies are related to the influence of the seawater zone of wave action marine splash and spray zone up to progressively more continental environments and to biokarst processes erosional action of marine organisms algae and micro organisms and are arranged in bands parallel to the coast corresponding to different morphological zones this paper describes all the karst landforms observed in this coastal area from a morphological and genetic point of view

mapping snow distribution in the alaskan arctic using aerial photography and topographic relationships a method is presented for mapping the end of winter snow distribution in the arctic using vertical aerial photographs taken during the melt the photos show a limited number of distinctive snowmelt patterns that arise reliably year after year data and results from an energy balance melt model indicate that the patterns are not caused by differential melt but instead represent areas of distinctive end of winter snow depth a map of these snowmelt patterns is thus a map of the end of winter snow distribution because wind transport of snow is common the patterns are closely related to the topography rules based on this pattern topography relationship are developed and used to map the snow cover directly from topographic maps for three areas covering 220 km2 of the kuparuk basin in northern alaska analysis of the snow maps suggests that about 75 of the area was mapped correctly applicability reliability and limitations of this mapping approach are discussed

the genesis of solution pipes evidence from the middle late pleistocene bridgewater formation calcarenite southeastern australia abstract solution pipes are abundant in late pleistocene aeolian calcarenites at cape bridgewater in southwestern victoria and were studied using field work morphometric analysis thin sections mineralogical and chemical analyses and osl dating the solution pipes are vertical tubes formed in aeolian limestone with matrix porosity they are typically 0 1 1 m wide and 1 5 m deep with rounded terminations and cemented rims up to 10 cm thick they are overlain by palaeosols and filled mostly with palaeosol material rhizoliths are commonly present in the solution pipe fills and the surrounding calcarenite the solution pipes have formed by focused dissolution of aeolianite relatively quickly after the sand deposition and concurrently filled with soil as they developed they most likely formed beneath trees as a result of focused infiltration due to stemflow or due to fingered flow unstable wetting front that breaks into fingers as it moves downwards solution pipe formation was strongly dependent on climate periods of solution pipe formation followed the deposition of aeolianites at the end of interglacials mis 7 9 and 11 when the dunes were stabilised by vegetation and there was sufficient rainfall for substantial subsoil dissolution the cemented rims formed in the following drier glacial climates solution pipes are most abundant in the youngest aeolianite probably reflecting the wetter climate at the end of mis 7 that allowed a dense forest to cover the dunes from mis 5 to mis 2 no deposition of calcareous sand occurred on cape bridgewater and combined with a very wet interglacial period mis 5e resulted in additional karstification allowing the pipes in the mis 7 aeolianite to extend deeper and drill down into the underlying member a well developed calcrete layer drapes over these solution pipes and probably formed during the dry windy climate of the last glacial maximum

tropical sst and sahel rainfall a non stationary relationship 1 sea surface temperature sst anomalies in the tropical atlantic have been associated with precipitation anomalies in west africa that form a dipole pattern with centers over the sahel and the gulf of guinea whilst this was clear before the 1970 s the dipole pattern almost disappeared after that date as the anti correlation between rainfall anomalies in the sahel and guinea dropped abruptly simultaneously the anti correlations between sahel rainfall and tropical pacific ssts strengthened it has been posited that these changes after the 1970 s developed as rainfall over west africa started to co vary with ssts in the global tropics in this co variability enhanced summer rainfall over west africa with a monopole pattern corresponds to warmer ssts in the tropical atlantic and maritime continent and colder ssts in the tropical pacific and western indian oceans the present paper describes the hitherto unexplored seasonal evolution of this co variability and the physical mechanisms at work sensitivity experiments with two atmospheric general circulation models demonstrate that after the 1970 s the impacts of sst anomalies in the indo pacific counteract those in the atlantic in terms of generating rainfall anomalies over the sahel and that this superposition of effects is primarily linear therefore at interannual timescales the change in the patterns of co variability between west african rainfall and tropical ssts can explain the non stationary relationship between the anomalies in these two fields

northwest africa upwelling and the atlantic climate variability 1 summer subtropical north atlantic sna sea surface temperature sst anomalies have recently been connected to winter atmospheric variability in the atlantic european sector wind induced surface heat flux changes are believed to be the major cause of sna sst anomalies however the impact of coastal upwelling off northwest africa on sna sst variability has been overlooked since the area is known to have a richer dynamical behavior than other regions of the central sna subsurface thermal anomalies are included in our analysis results show that this upwelling region affects significantly the patterns of co variability between climatically relevant variables suggesting that more intricate processes may be involved in generating surface anomalies that in turn may influence the european sector climate variability

the last glacial cycle from wyelangta the otway region of victoria australia abstract this paper presents the first long quaternary palynological record from the otway region of victoria an area which is biogeographically important in that it is an outlier of the southeastern highlands containing distinctive forest vegetation with great similarities to the island of tasmania the record is derived from a small remnant patch of cool temperate rainforest dominated by nothofagus cunninghamii surrounded by tall open eucalypt forest three clear phases are identified an older rainforest phase dated to beyond 40 000 years bp which probably represents the latter part of oxygen isotope stage 5 a phase of more open vegetation which covers at least part of the last glacial period and a younger rainforest phase of holocene age the record is significant in providing refinements to late quaternary climatic estimates from southeastern australia utilising the climatic profiles of key rainforest taxa and in indicating the likely presence and nature of a glacial rainforest refugium the occurrence of a major rain forest tree phyllocladus during the early forest phase and of the subalpine taxon gunnera during the last glacial period taxa now restricted to tasmania demonstrates an even greater biogeographic link to this island in the recent past their extinction on the mainland is consistent with the general demise of cool temperate taxa with close gondwanan affinities on the australian mainland through the late cenozoic period their late disappearance contributes to the growing list of mainland extinctions of ancient and geographically interesting taxa adding weight to the proposal that aboriginal burning has had a substantial impact on the australian landscape during the last glacial cycle

wetting and drying of australia over the past 300 ka alternately dry and wet climatic episodes across central and eastern australia during the past 300 ka have greatly affected australia9s rivers lakes and dune fields evidence of widespread climate and flow regime changes has been provided by 75 thermoluminescence tl dates and 18 u th dates from alluvial and eolian sediments fluvial conditions dominated part of the last two interglacials stage 5 and 7 resulting in large sand loads in rivers in the present simpson desert and southeastern australia during the last interglacial fluvial activity in central australia peaked at 110 ka stage 5 pluvial probably 5 10 ka behind world temperature and sea level maxima following the last late interglacial wet phase aridity associated with dune building spread from central australia toward its margins achieving greatest intensity during the last glacial maximum a less widespread wet phase identified at about 55 35 ka stage 3 subpluvial is associated with high lake levels and paleochannel activity in southeastern australia this tl record of variable continental aridity in australia correlates well with global changes including the variable eolian dust flux into central china the northern pacific ocean and antarctica

further thermoluminescence dates from the dune sequence in the southeast of south australia abstract our thermoluminescence dating technique has been applied to several new samples from the remarkable sequence of stranded beach dunes in southeast south australia that were formed during the past 800 ka we show that robe iii is probably 100 ka as suggested by schwebel and not 80 ka as we suggested earlier a sample from the west dairy dune is shown to belong to 18 o stage 7 in accordance with schwebel s original suggestion and not stage 5 as he suggested later a new west naracoorte sample yielded acceptable data and an age consistent with formation just after the brunhes matuyama magnetic reversal at 780 ka as required by palaeomagnetic measurements two more samples from the woakwine dune show that our reproducibility is consistent with our derived errors

is there evidence of changes in tropical atlantic variability modes under amo phases in the observational record abstractthe atlantic multidecadal oscillation amo is the leading mode of atlantic sea surface temperature sst variability at multidecadal time scales previous studies have shown that the amo could modulate el nino southern oscillation enso variance however the role played by the amo in the tropical atlantic variability tav is still uncertain here it is demonstrated that during negative amo phases associated with a shallower thermocline the eastern equatorial atlantic sst variability is enhanced by more than 150 in boreal summer consequently the interannual tav modes are modified during negative amo the atlantic nino displays larger amplitude and a westward extension and it is preceded by a simultaneous weakening of both subtropical highs in winter and spring in contrast a meridional seesaw slp pattern evolving into a zonal gradient leads the atlantic nino during positive amo the north tropical atlantic nta mode is related to a scandinavian blocking pattern during winter and spring

fingered flow in two dimensions 1 measurement of matric potential precise management of the changing matric potential during infiltration into unsaturated soil required the development of miniature high speed planar tensiometers a novel design was developed with response time of less than 1 s the applicability of the devices is shown through measurements of the matric potential in growing instabilities both in the induction zone and along the vertical finger profile tensiometry is demonstrated to be a practical method of obtaining data with high temporal and spatial resolution for the study of dynamic flow fields and facilitates testing of theoretical results for unstable flow fields

fingered flow the creator of sand columns in dune and beach sands sand columns sand cones sand mushrooms and other striking sand forms are frequently observed in the dutch and german beach and dune sands this paper aims to clarify the mechanism of sand column formation recently it has become evident that homogeneous beach and dune sands often become irregularly wetted by infiltrating rainwater in otherwise dry sandy soils wet preferential flow paths fingers may develop at two test sites the volumetric soil moisture content varied between 0 2 and 12 0 per cent the wet fingers represent the premature state of sand columns when the dry sand in between these fingers is blown away by the wind the more resistant wet sand of the fingers will remain in its place and appear as sand columns at the surface as a result of wind and erosive sand drifts striking sand forms may be formed

seasonal influence of enso on the atlantic itcz and equatorial south america 1 in late boreal spring especially may a strong relationship exists in observations among precipitation anomalies over equatorial south america and the atlantic intertropical convergence zone itcz and eastern equatorial pacific and central equatorial atlantic sea surface temperature anomalies ssta a chain of correlations of equatorial pacific ssta western equatorial atlantic wind stress wea equatorial atlantic ssta sea surface height and precipitation supports a causal chain in which el nino southern oscillation enso induces wea stress anomalies which in turn affect atlantic equatorial ocean dynamics these correlations show strong seasonality apparently arising within the atmospheric links of the chain this pathway and the influence of equatorial atlantic ssta on south american rainfall in may appear independent of that of the northern tropical atlantic brazil s nordeste is affected by the northern tropical atlantic the equatorial influence lies further to the north over the eastern amazon and the guiana highlands

enhancement of enso variability by a weakened atlantic thermohaline circulation in a coupled gcm abstract a coupled ocean atmosphere general circulation model is used to investigate the modulation of el nino southern oscillation enso variability due to a weakened atlantic thermohaline circulation thc the thc weakening is induced by freshwater perturbations in the north atlantic and leads to a well known sea surface temperature dipole and a southward shift of the intertropical convergence zone itcz in the tropical atlantic through atmospheric teleconnections and local coupled air sea feedbacks a meridionally asymmetric mean state change is generated in the eastern equatorial pacific corresponding to a weakened annual cycle and westerly anomalies develop over the central pacific the westerly anomalies are associated with anomalous warming of sst causing an eastward extension of the west pacific warm pool particularly in august february and enhanced precipitation these and other changes in the mean state lead in turn to an eastward shift of the zonal wind anomalies associated with el nin

el nino variability in simple ocean data assimilation soda 1871 2008 1 a new ocean reanalysis that covers the period from 1871 to 2008 is used to explore the time evolving characteristics of el nino the new reanalysis assimilates all available hydrographic and sea surface temperature data into a model of the global ocean forced with surface boundary conditions from an atmospheric reanalysis that also covers the period from 1871 through 2008 using traditional measures of el nino our reanalysis shows that the timing of el nino events is in agreement with sea surface temperature reconstructions but el nino in the reanalysis is stronger particularly from 1871 to 1920 a new index based on the first moment of the temperature anomaly is introduced the new index is used to characterize the strength and location of el nino events and has the advantage that it is independent of the location of el nino using the new index el nino in the reanalysis shows prominent decadal variability of strength but relatively little long term trend el nino events were strong in the last part of the 19th century and first part of the 20th century and again in the latter part of the 20th century with weak el nino events in the middle of the 20th century the location of el nino also varies considerably ranging from the western to the eastern pacific near the coast of south america however the null hypothesis that the location of el nino can be represented as a random distribution about a central longitude of about 140 w cannot be rejected

on the formation of dissolution pipes in quaternary coastal calcareous arenites in mediterranean settings a large number of uniform cone shaped dissolution pipes has been observed and studied in quaternary coastal calcareous arenites in apulia and sardinia italy and tunisia these cylindrical tubes have a mean diameter of 52 8 cm and are up to 970 cm deep mean depth for sediment free pipes is 1 38 m they generally have smooth walls along their length are perfectly vertical and taper out towards their bottoms their development is not influenced by bedding nor fractures sometimes their walls are coated by a calcrete crust their morphology has been studied in detail and their relationships with the surrounding rocks and with the environment have been analysed the perfectly vertical development is a clear evidence of their genesis controlled by gravity the depth of the dissolution pipes can be described by an exponential distribution law the milanovic distribution strongly suggesting they developed by a diffusion mechanism from the surface vertically downward we believe dissolution pipes preferentially form in a covered karst setting local patches of soil and vegetation cause infiltration water to be enriched in carbon dioxide enhancing dissolution of carbonate cement and local small scale subsidence this process causes the formation of a depression cone that guides infiltrating waters towards these spots giving rise to the downward growth of gravity controlled dissolution pipes a change of climate from wetter phases to drier and hotter ones causes the formation of a calcrete lining fossilizing the pipes when the pipes become exposed to surface agents by erosion of the sediment cover or are laterally breached the loose quartz sand filling them may be transported elsewhere copyright 2010 john wiley sons ltd

rapid sea level changes at the close of the last interglacial substage 5e recorded in bahamian island geology rapid and abrupt relative sea level changes within the last interglacial substage 5e are recorded in the island geology of the tectonically stable bahamas from 132 to 118 ka reef growth reached a maximum elevation near 2 m as indicated by fossil reef elevation across the platform whereas bioeroded notches are incised in coastal cliffs as high as 6 m the end of the interval is characterized by voluminous eolianites exhibiting palm tree and frond impressions it is inferred that sea level for most of the interval remained near 2 m restraining reef growth and that the notch at 6 m represents a rapid and brief excursion just before the close of the substage the subsequent fall must have been rapid in order to leave the notch profile intact and mobilize windward lagoon ooids into dunes before cementation could anchor them in order to explain the rapid rise to 6 m glacial surging is invoked the subsequent fall also rapid may be a consequence of the surge flooding high latitudes and providing enough moisture to initiate reglaciation and drawdown

speleogenesis in aeolian calcarenite a case study in western victoria most studies of karst landscapes and their processes have been concerned with consolidated often well jointed limestones there are particular problems involved in the study of karst procesess in softer less compact limestones such as chalk coral reefs and aeolian calcarenite previous studies in aeolian calcarenite indicated these problems and a scheme was developed of speleogenesis in aeolian calcarenite a study of karst processes in aeolian calcarenite at bats ridge in western victoria has developed this scheme further the karst features and processes at bats ridge are an integral part of the landscape of a mid pleistocene calcarenite dune system the resolution of problems of the rapid subaerial speleogenesis in the area is achieved by the synthesis of the known karst features of the ridge and the geology and geomorphology of the area karst development on this aeolianite ridge depends on lithological conditions as well as the availability of aggressive water capable of solution the diagenesis of the calcarenite is occurring now and must have been occurring by the mid pleistocene this simultaneous lithification of the carbonate dunes into aeolian calcarenite rock and the development of solutional karst features in the dunes is the characteristic feature of the speleogenesis in this area it is the formation of a hardened kankar layer cap rock in the dunes of sufficient compressive and tensile strength to support cavities which is the result of these interrelated factors that has strongly determined the formation of the karst features

on the atlantic pacific ninos connection a multidecadal modulated mode atlantic and pacific el nino are the leading tropical oceanic variability phenomena at interannual timescales recent studies have demonstrated how the atlantic nino is able to influence on the dynamical processes triggering the development of the pacific la nina and vice versa however the stationarity of this interbasin connection is still controversial here we show for the first time that the atlantic pacific ninos connection takes place at particular decades coinciding with negative phases of the atlantic multidecadal oscillation amo during these decades the atlantic pacific connection appears as the leading coupled covariability mode between tropical atlantic and pacific interannual variability the mode is defined by a predictor field the summer atlantic sea surface temperature sst and a set of predictand fields which represent a chain of atmospheric and oceanic mechanisms to generate the pacific el nino phenomenon alteration of the walker circulation surface winds in western pacific oceanic kelvin wave propagating eastward and impacting on the eastern thermocline and changes in the pacific sst by internal bjerknes feedback we suggest that the multidecadal component of the atlantic acts as a switch for el nino prediction during certain decades putting forward the amo as the modulator acting through changes in the equatorial atlantic convection and the equatorial pacific sst variability these results could have a major relevance for the decadal prediction systems

extratropical forcing of enso 1 we present evidence that sea surface temperatures in the north pacific south atlantic and south indian oceans during late boreal winter offer another important source of predictability for el nino southern oscillation enso this new sst predictor may provide accurate prediction of the amplitude of enso events before their onset for both el nino and la nina events which occurred during recent decades

collective role of thermocline and zonal advective feedbacks in the enso mode the vertical advection of anomalous subsurface temperature by the mean upwelling and the zonal advection of mean sea surface temperature sst by anomalous current are known to be essential for the equatorial sst anomaly associated with the el nino southern oscillation enso in the coupled model these two processes are referred to as the thermocline feedback and the zonal advective feedback respectively using a version of a recharge oscillator model for enso obtained from the stripped down approximation of the cane zebiak type model it is demonstrated that these two feedbacks which are linked dynamically through the geostrophic approximation tend constructively to contribute to the growth and phase transition of enso however these two feedbacks control the leading coupled mode in different ways the thermocline feedback leads to a coupled mode through the merging of the damped sst mode and ocean adjustment mode whereas the zonal advective feedback tends to destabilize the gravest ocean basin mode with both of these feedbacks the leading modes of the coupled model still can be traced back to these different origins under moderate changes in the model setup the main consequence of these sensitivities is that the growth rate and frequency of the enso mode may be sensitive to slight changes in basic state parameters which control the strength of these feedbacks