a multi proxy record of changing environments from ca 30 000 to 9000 cal a bp onepoto maar palaeolake auckland new zealand we present a high resolution record of lacustrine sedimentation spanning ca 30 000 to 9000 cal a bp from onepoto maar northern north island new zealand the multi proxy record of environmental change is constrained by tephrochronology and accelerator mass spectrometric 14c ages and provides evidence for episodes of rapid environmental change during the last glacial coldest period lgcp and last glacial interglacial transition lgit from northern new zealand the multi proxy palaeoenvironmental record from onepoto indicates that the lgcp was cold dry and windy in the auckland region with vegetation dominated by herb and grass in a beech forest mosaic between ca 28 500 and 18 000 cal a bp the lgcp was accompanied by more frequent fires and influx of clastic sediment indicating increased erosion during the lgcp with a mid lgcp interstadial identified between ca 25 000 and 23 000 cal a bp rapid climate amelioration at ca 18 000 cal a bp was accompanied by increased terrestrial biomass exemplified by the expansion of lowland podocarp forest especially dacrydium cupressinum increasing biomass production is reversed briefly by lgit perturbations which are apparent in many of the proxies that span ca 14 000 10 500 cal a bp suggesting generally increased wetness and higher in situ aquatic plant productivity with reduced terrestrial organic matter and terrigenous detrital influx furthermore conditions at that time were probably warmer and frosts rare based on the increasing importance of ascarina the subsequent early holocene is characterised by podocarp conifer forest and moist mild conditions postglacial sea level rise breached the crater rim and deposited 36 m of estuarine mud after ca 9000 cal a bp copyright 2011 john wiley sons ltd

holocene rainfall variability in southern chile a marine record of latitudinal shifts of the southern westerlies geochemical and clay mineral parameters of a high accumulation marine sediment core from the chilean continental slope 41 s provide a 7700 yr record of rainfall variability in southern chile related to the position of the southern westerlies we especially use the iron content measured with a time resolution of ca 10 yr on average of 14 caccelerator mass spectrometry dated marine sediments as a proxy for the relative input of iron poor coastal range and iron rich andean source rocks variations in this input are most likely induced by rainfall changes in the continental hinterland of the core position based on these interpretations we find a pronounced rainfall variability on multicentennial to millennial time scales superimposed on generally more arid conditions during the middle holocene 7700 to 4000 cal yr b p compared to the late holocene 4000 to present this variability and thus changes in the position of the southern westerlies are first compared to regional terrestrial paleoclimate data sets from central and southern chile in order to derive possible wider implications and forcing mechanisms of the holocene latitudinal shifts of the southern westerlies we then compare our data to ice core records from both tropical south america and coastal antarctica these records show similar bands of variability centered at ca 900 and 1500 yr comparisons of band pass filters suggest a close connection of shifts of the southern westerlies to changes within the tropical climate system the correlation to climate conditions in coastal antarctica shows a more complicated picture with a phase shift at the beginning of the late holocene coinciding with the onset of the modern state of el nin o southern oscillation system the presented data provide further evidence that the well known millennial scale climate variability during the last glacial continued throughout the holocene fl 2001 elsevier science b v all rights reserved

zonally asymmetric response of the southern ocean mixed layer depth to the southern annular mode interactions between the atmosphere and ocean are mediated by the mixed layer at the ocean surface the depth of this layer is determined by wind forcing and heating from the atmosphere variations in mixed layer depth affect the rate of exchange between the atmosphere and deeper ocean the capacity of the ocean to store heat and carbon and the availability of light and nutrients to support the growth of phytoplankton however the response of the southern ocean mixed layer to changes in the atmosphere is not well known here we analyse temperature and salinity data from argo profiling floats to show that the southern annular mode sam the dominant mode of atmospheric variability in the southern hemisphere leads to large scale anomalies in mixed layer depth that are zonally asymmetric from a simple heat budget of the mixed layer we conclude that meridional winds associated with departures of the sam from zonal symmetry cause anomalies in heat flux that can in turn explain the observed changes of mixed layer depth and sea surface temperature our results suggest that changes in the sam including recent and projected trends attributed to human activity drive variations in southern ocean mixed layer depth with consequences for air sea exchange ocean sequestration of heat and carbon and biological productivity

the evolution of el nino past and future abstract we review forecasts of the future of el nino and the southern oscillation enso a coupled instability of the ocean atmosphere system in the tropical pacific with global impacts enso in the modern world is briefly described and the physics of the enso cycle is discussed particular attention is given to the bjerknes feedback the instability mechanism which figures prominently in enso past and future our knowledge of enso in the paleoclimate record has expanded rapidly within the last 5 yr the enso cycle is present in all relevant records going back 130 kyr it was systematically weaker during the early and middle holocene and model studies indicate that this results from reduced amplification in the late summer and early fall a consequence of the altered mean climate in response to boreal summer perihelion data from corals shows substantial decadal and longer variations in the strength of the enso cycle within the past 1000 yr it is suggested that this may be due to solar and volcanic variations in solar insolation amplified by the bjerknes feedback there is some evidence that this feedback has operated in the 20th century and some model results indicate that it will hold sway in the greenhouse future but it is very far from conclusive the comprehensive general circulation models used for future climate projections leave us with an indeterminate picture of enso s future some predict more enso activity some less with the highly uncertain consensus forecast indicating little change

mapping of c4 plant input from north west africa into north east atlantic sediments abstract mapping the abundance of 13c in leaf wax components in surface sediments recovered from the seafloor off northwest africa 0 35 n reveals a clear pattern of 13c distribution indicating systematic changes in the proportions of terrestrial c3 and c4 plant input at 20 n latitude we find that isotopically enriched products characteristic of c4 plants account for more than 50 of the terrigenous inputs this signal extends westward beneath the path of the dust laden sahara air layer sal high c4 contributions apparently carried by january trade winds also extend far into the gulf of guinea similar distributions are obtained if summed pollen counts for the chenopodiaceae amaranthaceae and the poaceae are used as an independent c4 proxy we conclude that the specificity of the latitudinal distribution of vegetation in north west africa and the pathways of the wind systems trade winds and sal are responsible for the observed isotopic patterns observed in the surface sediments molecular isotopic maps on the marine sedimentary time horizons e g during the last glacial maximum are thus a robust tool for assessing the phytogeographic changes on the tropical and sub tropical continents which have important implications for the changes in climatic and atmospheric conditions

towards a climate event stratigraphy for new zealand over the past 30 000 years nz intimate project it is widely recognised that the acquisition of high resolution palaeoclimate records from southern mid latitude sites is essential for establishing a coherent picture of inter hemispheric climate change and for better understanding of the role of antarctic climate dynamics in the global climate system new zealand is considered to be a sensitive monitor of climate change because it is one of a few sizeable landmasses in the southern hemisphere westerly circulation zone a critical transition zone between subtropical and antarctic influences new zealand has mountainous axial ranges that amplify the climate signals and consequently the environmental gradients are highly sensitive to subtle changes in atmospheric and oceanic conditions since 1995 intimate has through a series of international workshops sought ways to improve procedures for establishing the precise ages of climate events and to correlate them with high precision for the last 30 000 calendar years the nz intimate project commenced in late 2003 and has involved virtually the entire new zealand palaeoclimate community its aim is to develop an event stratigraphy for the new zealand region over the past 30 000 years and to reconcile these events against the established climatostratigraphy of the last glacial cycle which has largely been developed from northern hemisphere records e g last glacial maximum lgm termination i younger dryas an initial outcome of nz intimate has been the identification of a series of well dated high resolution onshore and offshore proxy records from a variety of latitudes and elevations on a common calendar timescale from 30 000 cal yr bp to the present day high resolution records for the last glacial coldest period lgcp including the lgm sensu stricto and last glacial interglacial transition lgit from auckland maars kaipo and otamangakau wetlands on eastern and central north island marine core md97 2121 east of southern north island speleothems on northwest south island okarito wetland on southwestern south island are presented discontinuous fragmentary records comprising compilations of glacial sequences fluvial sequences loess accumulation and aeolian quartz accumulation in an andesitic terrain are described comparisons with ice core records from antarctica epica dome c and greenland gisp2 are discussed a major advantage immediately evident from these records apart from the speleothem record is that they are linked precisely by one or more tephra layers based on these new zealand terrestrial and marine records a reasonably coherent regionally applicable sequence of climatically linked stratigraphic events over the past 30 000 cal yr is emerging three major climate events are recognised 1 lgcp beginning at ca 28 000 cal yr bp ending at termination i ca 18 000 cal yr bp and including a warmer and more variable phase between ca 27 000 and 21 000 cal yr bp 2 lgit between ca 18 000 and 11 600 cal yr bp including a lateglacial warm period from ca 14 800 to 13 500 cal yr bp and a lateglacial climate reversal between ca 13 500 and 11 600 cal yr bp and 3 holocene interglacial conditions with two phases of greatest warmth between ca 11 600 and 10 800 cal yr bp and from ca 6 800 to 6 500 cal yr bp some key boundaries coincide with volcanic tephras copyright 2007 john wiley sons ltd

southern ocean seasonal temperature and subtropical front movement on the south tasman rise in the late quaternary 1 the subtropical front stf marking the northern boundary of the southern ocean has a steep gradient in sea surface temperature sst of approximately 4c over 0 5 of latitude presently in the region south of tasmania the stf lies nominally at 47s in the summer and 45s in the winter we present here sst reconstructions in a latitudinal transect of cores across the south tasman rise southeast of australia during the late quaternary sst reconstructions are based on two paleotemperature proxies alkenones and faunal assemblages which are used to assess past changes in sst in spring and summer the north south alignment in core locations allows reconstruction of movement of the stf over the last 100 ka surface water temperatures during the last glaciation in this region were 4c colder than today additional temperature changes greater in magnitude than 4c seen in individual cores can be attributed to changes in the water mass overlying the core site caused by the movement of the front across that location during the penultimate interglacial sst was 2c warmer and the stf was largely positioned south of 47s movement of the stf to the north occurred during cool climate periods such as the last marine isotope stages 3 and 4 in the last glaciation the front was at its farthest north position becoming pinned against the tasmanian landmass it moved south by 4 latitude to 47s in summer during the deglaciation but remained north of 45s in spring throughout the early deglaciation after 11 ka b p inferred invigoration of the east australia current appears to have pushed the stf seasonally south of the east tasman plateau until after 6 ka b p when it achieved its present configuration

fingerprints and age models for widespread new zealand tephra marker beds erupted since 30 000 years ago a framework for nz intimate abstract the role of tephras in the nz intimate project is a critical one because most high resolution palaeoclimatic records are linked and dated by one or more tephra layers in this review first we document eruptive distributional and compositional fingerprinting data both mineralogical and geochemical for 22 key marker tephras erupted since 30 000 years ago to facilitate their identification and correlation we include new glass compositional data the selected marker tephras comprise 10 from taupo and nine from okataina volcanoes rhyolitic one from tuhua volcano peralkaline rhyolitic and one each from tongariro and egmont volcanoes andesitic second we use four approaches to develop 2 age models for the tephras youngest to oldest 1 calendar ages for kaharoa and taupo y were obtained by wiggle matching log derived tree ring sequences dated by 14c 2 whakaipo v was dated using an age depth model from peat 3 14 tephras in the montane kaipo peat sequence waimihia s unit k whakatane tuhua mamaku rotoma opepe e poronui c karapiti b okupata konini waiohau rotorua rerewhakaaitu were dated by simultaneously wiggle matching stratigraphic position and 51 independent 14c age points against intcal04 using bayesian probability methods via both oxcal and bpeat and 4 the five oldest tephras erupted before ca 18 000 cal yr bp were dated by calibrating limited numbers of 14c ages using intcal04 okareka or comparison curves of the expanded cariaco basin sequence te rere kawakawa oruanui poihipi okaia kawakawa oruanui tephra the most widely distributed marker tephra was erupted probably ca 27 097 957 cal yr bp potential dating approaches for the older tephras include their identification in antarctic ice cores if present or annually laminated sediments for which robust calendar age models have been constructed high precision ams 14c dating on appropriate material from environmentally stable sites systematic luminescence dating or new radiometric techniques e g u th he if suitable minerals are available and errors markedly reduced further application of bayesian age modelling to stratigraphic sequences of 14c ages possibly augmented with luminescence ages may help refine age models for pre holocene tephras with the largest errors finally we discuss the critical role these marker tephras play in the ongoing construction of an event stratigraphy for the new zealand region which is a key objective of australasian and southern hemisphere intimate projects

el nino southern oscillation signal associated with middle holocene climate change in intercorrelated terrestrial and marine sediment cores north island new zealand a synchronous textural variation in intercorrelated high resolution sediment records from floodplain continental shelf and continental slope settings of the eastern north island new zealand provides evidence of increased storminess after ca 4 ka an upcore change in sediment texture reflects the transition to landsliding which supplanted fluvial incision as the dominant mode of sediment production in the middle holocene this signal which appears in all three records indicates a regional response to external forcing and records the impact of an intensified atmospheric circulation marking the establishment of the contemporary climate that is strongly influenced by the el nino southern oscillation the change in climate was a hemispheric event and in the southern hemisphere its timing is confirmed by independent proxy records from elsewhere in new zealand and the circum south pacific region

340 000 year centennial scale marine record of southern hemisphere climatic oscillation in order to investigate rapid climatic changes at mid southern latitudes we have developed centennial scale paleoceanographic records from the southwest pacific that enable detailed comparison with antarctic ice core records these records suggest close coupling of mid southern latitudes with antarctic climate during deglacial and interglacial periods glacial sections display higher variability than is seen in antarctic ice cores which implies climatic decoupling between mid and high southern latitudes due to enhanced circum antarctic circulation structural and temporal similarity with the greenland ice core record is evident in glacial sections and suggests a degree of interhemispheric synchroneity not predicted from bipolar ice core correlations

divergent trends in land and ocean temperature in the southern ocean over the past 18 000 years reconstructions of land and ocean temperatures over the past 18 000 years in the high southern latitudes have shown conflicting trends analyses of temperatures on campbell island south of new zealand confirm this behaviour and lead to the suggestion that it reflects changes in the position and intensity of the westerly winds over the past 18 000 years sea surface temperatures for the southern ocean do not align with those of the adjacent high latitude landmasses during the late glacial period the ocean surface warmed rapidly to present day temperatures1 whereas the land warmed only slowly as evidenced by the lagged response of forest and glaciers2 3 however in the holocene epoch land based records suggest strong warming whereas marine records indicate that ocean surface temperatures cooled here we present reconstructions of summer temperature for campbell island in the southern ocean over the past 16 500 years based on fossil pollen we find a pronounced warming 12 500 11 000 years ago a cooling until 9 200 years ago and a rapid warming to a peak between 6 000 and 5 000 years ago followed by minor cool intervals from 5 200 4 000 3 000 1 700 and 700 100 years ago as expected our temperature reconstructions show a late glacial lag behind nearby records of sea surface temperature6 7 and opposing trends in the holocene we suggest that this discrepancy arises because land based reconstructions record summer temperatures whereas marine proxies generally reflect annual temperatures we conclude that the divergence of the records therefore reflects changes in the seasonality of atmospheric heat transport as atmospheric heat transport is tied to the southern hemisphere westerly winds we attribute our observed changes to shifts in the position and intensity of the southern westerlies

southwest pacific modulation of abrupt climate change during the antarctic cold reversal younger dryas abstract the giant piston core md97 2121 2314 m water depth collected north of the subtropical front new zealand provides a well dated stable isotopic record of subtropical and sub antarctic influences on the surface and deep ocean over the last deglaciation especially during the antarctic cold reversal acr 14 1 12 4 ka and younger dryas yd 13 0 11 5 ka after the last glacial maximum benthic foraminiferal 18ob changed in phase with antarctica the acr being represented by a pause in the 18ob deglacial trend in contrast surface waters as represented by the stable isotopes of 3 planktic foraminifers from 3 different depth zones and alkenone based sea surface temperatures showed no immediate response to the acr it was not until the reversal was at its coldest starting 13 5 ka that the surface ocean responded it became less warm its fertility reduced sharply and its surface structure changed as shown by the merger of the 18opl planktic profiles onshore these changes were accompanied by an expansion of cool climate vegetation an advancement of alpine glaciers and a likely pause in the post glacial transgression these onshore and offshore changes which continued well into yd time probably resulted from modification of polar conditions by subtropical influences the acr caused cooler temperatures weakened seasonality and stronger winds however its onset and impact were ameliorated by a strengthened inflow of subtropical water although acr driven atmospheric conditions prevailed by comparison south of the subtropical front where subtropical influences are weak and water masses have direct links with antarctica the surface waters cooled in phase with the acr

late quaternary paleolimnology of onepoto maar auckland new zealand implications for the drivers of regional paleoclimate abstract a high resolution record of lacustrine environments spanning ca 30 9 cal ka bp was obtained from onepoto maar northern north island new zealand the multi proxy record of environmental change is constrained by tephrochronology and ams 14 c ages and provides evidence for episodes of rapid environmental change during the last glacial coldest period lgcp 28 5 18 cal ka bp and late glacial interglacial transition lgit from northern new zealand the onepoto pollen record indicates that the lgcp was cold dry and windy in the auckland region with vegetation dominated by herbs and grasses in a beech forest mosaic at the same time the diatom record indicates oligotrophic conditions with low lakes levels and turbulence whilst cladocerans indicate low water temperatures the inference of cold dry and windy conditions during the lgcp is supported by geochemical evidence for increased sediment influx charcoal and co 2 limiting conditions for terrestrial macrophytes rapid climate amelioration and forest expansion after ca 18 cal ka bp corresponds with reduced sediment influx diatom and cladoceran inferred higher lake levels indicating increasing moisture availability and temperature diatom flora indicates that an oligotrophic circumneutral lake was becoming established during the lgit but conditions were still variable between ca 13 8 and 12 5 cal ka bp two brief drier and possibly cooler episodes are apparent ca 13 8 13 2 and 13 12 5 cal ka bp followed by a warm phase combined with generally stable high lake levels between ca 12 5 and 10 5 cal ka bp subsequently the lake water chemistry became more alkaline and eutrophic possibly because sea level had risen high enough by this time to influence ground water chemistry

seasonal variations in aridity and temperature characterize changing climate during the last deglaciation in new zealand abstract new multiproxy records of aridity from northern new zealand assess the seasonality and overall pattern of wetness through the last glacial coldest period lgcp to the early holocene in the subtropical southwest pacific biomass burning indicators based on terrestrial biomarkers and 13 c of individual plant leaf wax carbon compounds n alkanoic acids from a maar lake were used to track aridity in combination with published sea surface temperatures and new pollen based temperature estimates from the same core seasonal climatological changes in the auckland area were determined from 27 to 9 cal ka bp these proxies document a shift from cold and dry conditions in the last glacial maximum to seasonally wetter conditions through the deglaciation spring became warmer first and possibly wetter while summers remained drier and initially cooler the progression from cold dry to warm wet was punctuated by the antarctic cold reversal acr which stands out as having wetter conditions in both spring and summer and mild cooling largely concentrated in spring the seasonal climate trends observed here can be plausibly explained by a rapid change from a subpolar climate to one with subtropical control in this region of the southwest pacific across the last glacial to interglacial transition a southerly shift and decreasing intensity of the westerly wind belt after the lgcp is considered to have driven the early deglacial warming and pulse of wetness whereas a northward shift without a commensurate increase in intensity of the westerlies may explain conditions in the acr

c3 c4 variations in salt marsh sediments an application of compound specific isotopic analysis of lipid biomarkers to late holocene paleoenvironmental research in salt marshes bulk carbon isotope values reflect organic matter contributions not only from salt marsh plants but also from algal and bacterial inputs as well as allochthonous terrestrial organic matter in the present study compound specific isotope analysis was applied to a core and modern plant samples collected from a machiasport maine salt marsh we sampled 10 plant species common to the marsh including spartina alterniftora spartina patens juncus gerardi solidago sempervirens salicornia europa potentilla anserina atriplex patula plantago maritima suaeda maritima and limonium nashii isolation of two n alkanes c 27 and c 29 present in marsh plant samples allowed for the reconstruction of past plant communities present in the cored deposits for the c 27 and c 29 homologues there is a 3 10 separation in carbon isotopic composition between c3 and c4 species carbon isotopic values down core show a transition from a c4 dominated plant community to a c3 dominated community attributable to the migration of lower marsh zones onto brackish freshwater marsh zones during a late holocene relative sea level rise the two homologues used have the potential to provide paleoenvironmental information in future core work where the sea level variable will be controlled

holocene vegetation and climate change in southern new zealand linkages between forest composition and quantitative surface moisture reconstructions from an ombrogenous bog this paper presents a holocene pollen record from an ombrotrophic bog in southland new zealand together with multiproxy data testate amoebae peat humification and plant macrofossils from the same core to establish an independent semiquantitative record of peatland surface moisture linkages between reconstructed peatland surface moisture and regional forest composition are investigated using redundancy analysis of the forest pollen data constrained with predicted bog water table depths over 32 of the pollen data variance can be explained by surface moisture changes in the bog suggesting a common cause of water table and regional vegetation change water tables were higher during the early to mid holocene when the forest was dominated by podocarp taxa water tables lowered after about 3300 cal yr bp coevally with the expansion of nothofagus species culminating with the dominance of nothofagus subgenus fuscospora in the past 1200 cal yr bp this is in apparent opposition to the warm dry to cool wet trend suggested by subjective interpretation of pollen data alone from this and other studies we suggest that during the late holocene drier summers associated with shifts in solar insolation caused reduced surface wetness and summer humidity which together with a trend to cooler winters apparently favoured the regeneration of nothofagus species copyright 2002 john wiley sons ltd

molecular and isotopic records of c4 grassland expansion in the late miocene abstract siwalik paleosol and bengal fan sediment samples were analyzed for the abundance and isotopic composition ofn alkanes in order to test for molecular evidence of the expansion of c4 grasslands on the indian subcontinent the carbon isotopic compositions of high molecular weight alkanes in both the ancient soils and sediments record a shift from low 13c values ca 30 to higher values ca 22 prior to 6 ma this shift is similar in magnitude to that recorded by paleosol carbonate and fossil teeth and is consistent with a relatively rapid transition from dominantly c3 vegetation to an ecosystem dominated by c4 plants typical of semi arid grasslands the n alkane values from our paleosol samples indicate that the isotopic change began as early as 9 ma reflecting either a growing contribution of c4 plants to a dominantly c3 biomass or a decrease in water availability to c3 plants molecular and isotopic analyses of other compounds including n alcohols and low molecular weightn alkanes indicate paleosol organic matter contains contributions from a mixture of sources including vascular plants algae and or cyanobacteria and microorganisms a range of inputs is likewise reflected in the isotopic composition of the total organic carbon from these samples in addition then alkanes from two samples show little evidence for pedegenic inputs and we suggest the compounds were derived instead from the paleosol s parent materials we suggest the record of vegetation in ancient terrestrial ecosystems is better reconstructed using isotopic signatures of molecular markers rather than bulk organic carbon this approach provides a means of expanding the spatial and temporal records of c4 plant biomass which will help to resolve possible tectonic climatic or biological controls on the rise of this important component of the terrestrial biosphere

modulation of the bipolar seesaw in the southeast pacific during termination 1 the termination of the last ice age termination 1 t1 is crucial for our understanding of global climate change and for the validation of climate models there are still a number of open questions regarding for example the exact timing and the mechanisms involved in the initiation of deglaciation and the subsequent interhemispheric pattern of the warming our study is based on a well dated and high resolution alkenone based sea surface temperature sst record from the se pacific off southern chile ocean drilling project site 1233 showing that deglacial warming at the northern margin of the antarctic circumpolar current system acc began shortly after 19 000 years bp 19 kyr bp the timing is largely consistent with antarctic ice core records but the initial warming in the se pacific is more abrupt suggesting a direct and immediate response to the slowdown of the atlantic thermohaline circulation through the bipolar seesaw mechanism this response requires a rapid transfer of the atlantic signal to the se pacific without involving the thermal inertia of the southern ocean that may contribute to the substantially more gradual deglacial temperature rise seen in antarctic ice cores a very plausible mechanism for this rapid transfer is a seesawinduced change of the coupled ocean atmosphere system of the acc and the southern westerly wind belt in addition modelling results suggest that insolation changes and the deglacial co2 rise induced a substantial sst increase at our site location but with a gradual warming structure the similarity of the two step rise in our proxy ssts and co2 over t1 strongly demands for a forcing mechanism influencing both temperature and co2 as ssts at our coring site are particularly sensitive to latitudinal shifts of the acc southern westerly wind belt system we conclude that such latitudinal shifts may substantially affect the upwelling of deepwater masses in the southern ocean and thus the release of co2 to the atmosphere as suggested by the conceptual model of toggweiler j r rusell j l carson s r 2006 midlatitude westerlies atmospheric co2 and climate change during ice ages

slip slidin away a post glacial environmental history of the waipaoa river basin abstract the dramatic changes that occurred to the post glacial landscape in the headwaters of the waipaoa river basin are a consequence of perturbations about the equilibrium that exists between the rate of tectonic uplift and fluvial incision at times when the amount of coarse sediment delivered to channels exceeds the capacity of streams to remove it the channel bed rises at the rate of tectonic uplift once bedload overcapacity is replaced by undercapacity and the alluvial cover is depleted streams reestablish contact with bedrock and recuperate the time lost to fluvial incision the first major perturbation occurred during the final phase of the last glaciation ca 33 17 5 cal ka when aggradation was driven by a climate forced variation in the relative supplies of sediment and water we suggest that the subsequent transformation of channels in the headwaters of the waipaoa river basin from alluvial to bedrock occurred as the atmospheric and oceanic circulation converged on their contemporary patterns ca 12 cal ka a second major perturbation that continues to the present began ca 1910 1912 ce when a massive increase in sediment load was accompanied by a modest increase in water discharge after the native vegetation cover in the headwaters was replaced by pasture the processes of terrace creation and incision are inherently unsteady and in five interim cases incision was arrested by a transient increase in the thickness of the alluvial cover that was a response to climatic forcing events that disrupted the native vegetation cover in the headwaters also modulated patterns of sediment dispersal and accumulation in other parts of the fluvial system and caused rapid storm driven infilling of the poverty bay flats tectonic subsidence dictates the course of the waipaoa river across poverty bay flats which because the modern rate of floodplain construction by vertical accretion is rapid relative to the amount of destruction by lateral channel migration has remained virtually unchanged for the past 100 years during this time the channel assumed a narrower deeper form that is in equilibrium with the contemporary supply of sediment and hydraulic regime

three dimensional spherical models of convection in the earth s mantle three dimensional spherical models of mantle convection in the earth reveal that upwelling cylindrical plumes and downwelling planar sheets are the primary features of mantle circulation thus subduction zones and descending sheetlike slabs in the mantle are fundamental characteristics of thermal convection in a spherical shell and are not merely the consequences of the rigidity of the slabs which are cooler than the surrounding mantle cylindrical mantle plumes that cause hotspots such as hawaii are probably the only form of active upwelling and are therefore not just secondary convective currents separate from the large scale mantle circulation active sheetlike upwellings that could be associated with mid ocean ridges did not develop in the model simulations a result that is in agreement with evidence suggesting that ridges are passive phenomena resulting from the tearing of surface plates by the pull of descending slabs

rapid environmental changes in southern europe during the last glacial period oxygen isotope records from greenland ice cores1 2 indicate numerous rapid climate fluctuations during the last glacial period north atlantic marine sediment cores show comparable variability in sea surface temperature and the deposition of ice rafted debris3 4 5 in contrast very few continental records of this time period provide the temporal resolution and environmental sensitivity necessary to reveal the extent and effects of these environmental fluctuations on the continents here we present high resolution geochemical physical and pollen data from lake sediments in italy and from a mediterranean sediment core linked by a common tephrochronology our lacustrine sequence extends to the past 102 000 years many of its features correlate well with the greenland ice core records demonstrating that the closely coupled ocean atmosphere system of the northern hemisphere during the last glacial4 extended its influence at least as far as the central mediterranean region numerous vegetation changes were rapid frequently occurring in less than 200 years showing that the terrestrial biosphere participated fully in last glacial climate variability earlier than 65 000 years ago our record shows more climate fluctuations than are apparent in the greenland ice cores together the multi proxy data from the continental and marine records reveal differences in the seasonal character of climate during successive interstadials and provide a step towards determining the underlying mechanisms of the centennial millennial scale variability

convection planforms in a fluid with a temperature dependent viscosity beneath a stress free upper boundary this study presents the results of a joint numerical and laboratory study of 3 d planforms of time dependent convection in a newtonian fluid layer with a temperature dependent viscosity planforms are found for the case in which the fluid is bounded from above by a stress free boundary and below by a rigid boundary and compared to the planforms found when the fluid layer is bounded by rigid boundaries all of the laboratory and numerical experiments were performed with nearly the same values of the rayleigh number ra1 2 1 105 and viscosity ratio r 50 and viscosity law to allow direct comparisons when the fluid layer is bounded by rigid boundaries the observed planforms are the spoke patterns which are an interconnected network of descending and ascending sheets however when the upper boundary is stress free the morphology of the downwellings change from spokes to a dendritic network of descending sheets and the wavelength of the planform is more than 3 times as large as the spoke pattern planform in both cases the numerical and laboratory experiments are in good agreement

climatic variability in the southwest pacific during the last termination 20 10 kyr bp the degree to which palaeoclimatic changes in the southern hemisphere co varied with events in the high latitude northern hemisphere during the last termination is a contentious issue with conflicting evidence for the degree of teleconnection between different regions of the southern hemisphere the available hypotheses are difficult to test robustly however because there are few detailed palaeoclimatic records in the southern hemisphere here we present climatic reconstructions from the southwestern pacific a key region in the southern hemisphere because of the potentially important role it plays in global climate change the reconstructions for the period 20 10 kyr bp were obtained from five sites along a transect from southern new zealand through australia to indonesia supported by 125 calibrated c 14 ages two periods of significant climatic change can be identified across the region at around 17 and 14 2 cal kyr bp most probably associated with the onset of warming in the west pacific warm pool and the collapse of antarctic ice during meltwater pulse 1a respectively the severe geochronological constraints that inherently afflict age models based on radiocarbon dating and the lack of quantified climatic parameters make more detailed interpretations problematic however there is an urgent need to address the geochronological limitations and to develop more precise and quantified estimates of the pronounced climate variations that clearly affected this region during the last termination c 2005 elsevier ltd all rights reserved

does the bipolar seesaw extend to the terrestrial southern mid latitudes abstract high precision comparison of greenland and antarctic ice cores suggesting a pervasive antiphased temperature relationship between the polar hemispheres during the last glaciation lends strong support to the bipolar seesaw model epica 2006 the extent to which reorganisation of ocean heat transport during abrupt climate change events affected the southern mid latitudes remains unclear however owing to a paucity of well dated records with robust climate proxies variability between some records and varying interpretations of their significance here we present temperature reconstructions for three key pollen records recognised by the nz intimate nz i group which along with the preliminary nz i climate event stratigraphy alloway et al 2007 and published marine records are compared with polar ice core records for the interval 30 10 cal ka we focus on key events within the context of dansgard oeschger cycles 4 1 and the antarctic cold reversal younger dryas intervals the new zealand records are broadly consistent with an extended bipolar seesaw whereby the oceanic southern mid latitudes are warmed at times of moc weakening or cessation in the north atlantic and vice versa variability between records indicate that other factors must be involved however and nor do these records refute alternative models that predict an antiphased inter hemispheric pattern nevertheless an extended bipolar model may explain an early onset of lgm conditions in new zealand and elsewhere in the southern hemisphere at a time when interstadials gi3 and gi4 kept greenland warm similar inter hemispheric dynamics have been invoked to explain an earlier termination of the lgm in antarctica than in greenland wolff et al 2009 which is also evident in the new zealand records a prominent mid lgm interstadial complex observed in several new zealand records connected by tephrochronology may represent another antiphased event although stronger chronological control is needed to support this assertion by comparison the variability evident between new zealand lateglacial records cannot be explained simply by chronological imprecision and there may be latitudinal controls on the extent to which the antarctic pattern is registered as has been suggested from other records from the southern mid high latitudes consolidation of these patterns is needed from more precise climate reconstructions at sites spread across latitudinal gradients in both the marine and terrestrial realms

land ice teleconnections of cold climatic periods during the last glacial interglacial transition independent calendar year chronologies are a basic requirement for the establishment of high resolution land ice teleconnections the annually laminated meerfelder maar record provides both an independent chronology established by varve counting and high resolution lithological proxy data for the period of the last glacial interglacial transition these data reveal a series of four periods of climatic deterioration coinciding with negative isotopic deviations in the grip record signal thus demonstrating the synchronicity of environment changes in western germany and temperature shifts in greenland the terrestrial data supports a further sub division of the event stratigraphy based on the grip core by introducing the cold event gi 1c2 between 13 500 and 13 400 calendar years bp multiproxy analyses reveal that the environmental response at meerfelder maar was not linear throughout the lateglacial but was modified by local processes a change in the response of the lake environment to climate deterioration was observed during sub stage gi 1b gerzensee oscillation the only event with gradual rather than abrupt transitions the two fold character of the younger dryas as seen in the grip record is more pronounced in the meerfelder maar record this lithological signal occurred with a delay of 60 years to the grip signal and has been linked to a shift in the catchment it is proposed that the trigger for this shift was a trend towards a more humid second half of the younger dryas

late glacial and holocene vegetation and climatic history of the cass basin central south island new zealand abstract lithology pollen macrofossils and stable carbon isotopes from an intermontane basin bog site in southern new zealand provide a detailed late glacial and early holocene vegetation and climate record glacial retreat occurred before 17 000 cal yr b p and tundra like grassland shrubland occupied the basin shortly after between 16 500 and 14 600 cal yr b p a minor regional expansion of forest patches occurred in response to warming but the basin remained in shrubland forest retreated between 14 600 and 13 600 cal yr b p at about the time of the antarctic cold reversal at 13 600 cal yr b p a steady progression from shrubland to tall podocarp forest began as the climate ameliorated tall temperate podocarp trees replaced stress tolerant shrubs and trees between 12 800 and 11 300 cal yr b p indicating sustained warming during the younger dryas chronozone ydc stable isotopes suggest increasing atmospheric humidity from 11 800 to 9300 cal yr b p mild annual temperatures at least 1 c higher than present and moist conditions prevailed from 11 000 to 10 350 cal yr b p cooler more variable conditions followed and podocarp forest was completely replaced by montane nothofagus forest at around 7500 cal yr b p with the onset of the modern climate regime the cass basin late glacial climate record closely matches the antarctic ice core records and is in approximate antiphase with the north atlantic

last glacial pollen climate reconstructions from northland new zealand despite wide ranging interest in the vegetation and climate of northland new zealand during the last glacial cycle the region and timeframe lack quantitative climate reconstructions while land based pollen records have tended to be poorly dated and fragmentary the region is also important for geochronology due to the co occurrence of the rotoehu tephra a widely dispersed isochron near the current limits of radiocarbon dating and extensive subfossil wood remains of agathis australis with strong dendrochronological and dendroclimatological potential we present new pollen records and temperature reconstructions from three sites set in coastal dune belts from western mid northland 35 s all containing rotoehu tephra that collectively span the last 70 ka the phases and amplitude of temperature changes broadly align with those reported from elsewhere in new zealand and with marine isotope climate stratigraphic records including maximum temperature depression of 6 8 c during the last glacial maximum we argue that these climatic patterns are intimately linked to shifts in the southern westerly wind belt the northern margins of which extend to the region today correspondence between the northland temperature shifts and atmospheric co2 supports the model of ocean atmosphere co2 flux modulated by latitudinal migration of the southern westerlies copyright 2017 john wiley sons ltd

a cosmogenic 10be chronology for the local last glacial maximum and termination in the cordillera oriental southern peruvian andes implications for the tropical role in global climate abstract resolving patterns of tropical climate variability during and since the last glacial maximum lgm is fundamental to assessing the role of the tropics in global change both on ice age and sub millennial timescales here we present a10be moraine chronology from the cordillera carabaya 14 3 s a sub range of the cordillera oriental in southern peru covering the lgm and the first half of the last glacial termination additionally we recalculate existing 10be ages using a new tropical high altitude production rate in order to put our record into broader spatial context our results indicate that glaciers deposited a series of moraines during marine isotope stage 2 broadly synchronous with global glacier maxima but that maximum glacier extent may have occurred prior to stage 2 thereafter atmospheric warming drove widespread deglaciation of the cordillera carabaya a subsequent glacier resurgence culminated at 16 100 yrs followed by a second period of glacier recession together the observed deglaciation corresponds to heinrich stadial 1 hs1 18 000 14 600 yrs during which pluvial lakes on the adjacent peruvian bolivian altiplano rose to their highest levels of the late pleistocene as a consequence of southward displacement of the inter tropical convergence zone and intensification of the south american summer monsoon deglaciation in the cordillera carabaya also coincided with the retreat of higher latitude mountain glaciers in the southern hemisphere our findings suggest that hs1 was characterised by atmospheric warming and indicate that deglaciation of the southern peruvian andes was driven by rising temperatures despite increased precipitation recalculated 10be data from other tropical andean sites support this model finally we suggest that the broadly uniform response during the lgm and termination of the glaciers examined here involved equatorial pacific sea surface temperature anomalies and propose a framework for testing the viability of this conceptual model

the effect of rheological parameters on plate behaviour in a self consistent model of mantle convection abstract in a three dimensional numerical model of mantle convection we have explored the self consistent formation and evolution of plates this was done by investigating the influence of temperature stress and pressure dependence of the viscosity on plate like behaviour further the role of a depth dependent thermal expansivity and of internal heating was examined first order self consistent plate tectonics can be obtained for temperature and stress dependent viscosity we observe virtually undeformed moving plates and the phenomenon of trench migration however plate motion only appears during short intervals which are interrupted by long phases characterised by an immobile lid an improvement is achieved by adding pressure dependence of the viscosity and of the thermal expansivity to the model this leads to extended plates with continuous plate motion and the appearance of a low viscosity zone internal heating accelerates subduction and gives an increase in plate velocity the plates are otherwise left intact we find that the surface velocity is largely determined by subduction rather than by upwellings plate like behaviour is restricted to a narrow parameter window the window is bordered by an episodic or a stagnant lid type of flow on the one side and by a domain in which convection is akin to constant viscosity flow on the other side with these different convective regimes the behaviour of various terrestrial planets can be described self consistently occasionally even a change from the plate regime to the stagnant lid regime occurs such a type of transition has possibly changed the style of tectonics on some terrestrial planets such as mars

rerewhakaaitu tephra a land sea marker for the last termination in new zealand with implications for global climate change abstract the rerewhakaaiutu tephra erupted from okataina volcanic centre north island new zealand at 14 700 95 14 c yr bp ca 17 600 cal yr bp at a time of rapid re organisation of earth s climate system at the end of the last glacial termination i it provides a distinctive isochron in a range of different environments in north island and in adjacent south pacific ocean sediments terrestrial evidence based on fluvial aggradation and downcutting relationships loess accumulation rates palaeovegetation patterns and buried soil development and mineralogy shows that marked amelioration of climate occurred shortly before the rerewhakaaitu tephra was deposited similarly marine evidence from around this time shows major changes in accumulation rates of sediment and aeolian quartz and in the abundance of various marine organisms while foraminiferal oxygen and carbon isotope records indicate that the arrival of the glacial meltwater signal occurred close to or just after the deposition of the rerewhakaaitu tephra these changes are discussed in relation to controls on climate by oceanic and atmospheric mechanisms the re organisation of climate commencing at ca 15 000 14 500 14 c yr bp ca 18 000 17 400 cal yr bp is detected elsewhere in the southern hemisphere and evidently was linked to orbitally forced warming which is thought to have initiated ice retreat in both hemispheres

asynchronous climate change between new zealand and the north atlantic during the last deglaciation climatic fluctuations recorded in antarctica and greenland during the last deglaciation 18 10 ka differ markedly in their timing it remains controversial whether local climate fluctuations recorded in southern mid latitudes relate primarily to northern or southern polar records we present multiproxy results from new zealand that show strong evidence for a minor cooling or slowdown in the rate of warming at the time of the north atlantic late glacial interstadial the younger dryas chronozone in new zealand was a period of resumed warming and increased westerly airflow differences between the hemispheres at this time were probably due to a reorganization of the thermohaline circulation system and associated changes in the meridional temperature gradient

mantle dynamics in mars and venus influence of an immobile lithosphere on three dimensional mantle convection numerical calculations of fully three dimensional convection in constant viscosity compressible spherical shells are interpreted in terms of possible convective motions in the mantles of venus and mars the shells are heated both internally and from below to account for radiogenic heating secular cooling and heat flow from the core the lower boundary of each of the shells is isothermal and shear stress free as appropriate to the interface between a mantle and a liquid outer core the upper boundary of each of the shells is rigid and isothermal as appropriate to the base of a thick immobile lithosphere calculations with shear stress free upper boundaries are also carried out to assess the role of the rigid surface condition the ratio of the inner radius of each shell to its outer radius is in accordance with possible core sizes in both venus and mars a calculation is also carried out for a mars model with a small core to simulate mantle convection during early core formation different relative proportions of internal and bottom heating are investigated ranging from nearly complete heating from within to almost all heating from below the rayleigh numbers of all the cases are approximately 100 times the critical rayleigh numbers for the onset of convection cylindrical plumes are the prominent form of upwelling in the models independent of the surface boundary condition so long as sufficient heat derives from the core thus major volcanic centers on mars such as tharsis and elysium and the coronae and some equatorial highlands on venus may be the surface expressions of cylindrical mantle plumes the form of the downwelling sheets is significantly affected by the rigid boundary in that the sheets are more irregular in their horizontal structure than when the top boundary is shear stress free in the mainly heated from within models the downwelling sheets are also shorter and less temporally durable when the top boundary is rigid than when it is stress free thus the free motion of plates on the earth facilitates extensive durable convective currents that drive the plates while the stiffening of the lithospheres on mars and venus promotes a style of convection that is not particularly effective in breaking the lithosphere into plates in the rigid top cases the upper boundary layer surrounding the plumes appears to be interspersed with downwelling currents emanating radially from the plumes axes these currents may establish a stress field at the base of hotspot swells that could lead to radial fractures such as those on tharsis models with rigid upper boundaries have higher interior temperatures than do similar models with shear stress free upper boundaries on this basis venus not only has a higher surface temperature than earth but it would have a hotter mantle as well upwelling plumes are more numerous when the outer boundary is rigid as compared with shear stress free flows dominated by a few stong plumes occur when the proportion of basal heating is large thus if the martian crustal dichotomy were caused by a convective system dominated by spherical harmonic degree l 1 then the convection may have been driven strongly from below by a heating pulse accompanying core formation or from the flow of heat from an early hot core if a convective mechanism is responsible for the crustal dichotomy then the dichotomy is likely a very ancient feature however the small core models we consider consistently produce a convective pattern with a dominant l 2 signature which does not correlate with the martian crustal dichotomy a yet smaller core may be necessary to yield the l 1 pattern the small core convective pattern does correlate with the geoid and topography signatures of tharsis which have strong l 2 components and the model produces dynamic uplift comparable to the total topography of the tharsis rise models with larger cores i e with the probable inner to outer radius ratio of mars present mantle generate 4 km of uncompensated topography similar to estimates of the uncompensated tharsis topography thus the tharsis rise could have achieved its full height early in the evolution of mars by mantle plume dynamic uplift at present the uncompensated portion of the tharsis rise topography can be accounted for by dynamic uplift obviating the need for elastic support the present compensated portion of the tharsis topography could be attributed to volcanic or magmatic crustal thickening or depletion of the underlying mantle large core models appropriate to the present mars produce too many plumes to account for just two major volcanic centers i e tharsis and elysium mantle plume activity could be focussed beneath regions like tharsis if fracturing or thinning of the lithosphere in these regions has facilitated magma and heat transport across the lithosphere a similar mechanism could be responsible for clustering of coronae on venus there are no deep seated active linear upwellings in the venus models that could be associated with linear spreading centers in aphrodite if linear spreading is actually occurring in aphrodite the phenomenon is probably a shallow passive one similar to mid ocean ridges on earth

distal record of multi sourced tephra in onepoto basin auckland new zealand implications for volcanic chronology frequency and hazards we have documented 80 tephra beds dating from ca 9 5 to 50 ka contained within continuously deposited palaeolake sediments from onepoto basin a volcanic explosion crater in auckland new zealand the known sources for distal 190 km from vent tephra include the rhyolitic taupo volcanic centre 4 and okataina volcanic centre 14 and the andesitic taranaki volcano 40 and tongariro volcanic centre 3 the record provides evidence for four new events between ca 50 and 28 ka mangaone subgroup suggesting okataina was more active than previously known the tephra record also greatly extends the known northern dispersal of other mangaone subgroup tephra ten rhyolitic tephra pre date the rotoehu eruption ca 50 ka and some are chemically dissimilar to post 50 ka rhyolites some of these older tephra were produced by large magnitude events however their source remains uncertain eight tephra from the local basaltic auckland volcanic field avf are also identified interpolation of sedimentation rates allow us to estimate the timing of 12 major explosive eruptions from taranaki volcano in the 27 5 9 5 ka period in addition 28 older events are recognised the tephra are trachytic to rhyolitic in composition all have high k2o contents 3 wt and there are no temporal trends this contrasts with the proximal lava record that shows a trend of increasing k2o with time by combining the onepoto tephra record with that of the previously documented pukaki crater 15 avf basaltic fall events are constrained at 34 6 30 9 29 6 29 6 25 7 25 2 24 2 23 8 19 4 19 4 15 8 and 14 5 ka and three pre 50 ka events this provides some of the best age constraints for the avf and the only reliable data for hazard recurrence calculations the minimum event frequency of both distal and local fall events can be estimated and demonstrates the auckland city region is frequently impacted by ash fall from many volcanoes

the last glacial termination a major puzzle of paleoclimatology is why after a long interval of cooling climate each late quaternary ice age ended with a relatively short warming leg called a termination we here offer a comprehensive hypothesis of how earth emerged from the last global ice age a prerequisite was the growth of very large northern hemisphere ice sheets whose subsequent collapse created stadial conditions that disrupted global patterns of ocean and atmospheric circulation the southern hemisphere westerlies shifted poleward during each northern stadial producing pulses of ocean upwelling and warming that together accounted for much of the termination in the southern ocean and antarctica rising atmospheric co2 during southern upwelling pulses augmented warming during the last termination in both polar hemispheres

the significance of maar volcanoes for palaeoclimatic studies in china abstract the sediments of maar lakes often provide paleoenvironmental records which are highly suitable for palaeoclimatic studies the main advantages of the records from maar lakes compared with other lacustrine records are as follows first the presence of varves annually laminated layers and tephra layers as well as other materials like terrestrial plant macrofossils charcoals organic carbon organic shells suitable for isotopic dating like ams 14c 210pb 137cs 238u 230th 40ar 39ar provides the possibility of developing several independent chronologies enabling the development of robust high resolution chronologies second maars and maar lakes can provide continuous sedimentary records spanning tens of thousands of years tianyang maar in china is hosted the longest known record spanning at least 400 kyr bp that are ideal for the investigation of climate change on different timescales including orbital millennial centennial and annual decadal third recent studies of biomarkers based on long chain alkenones lcas and glycerol dialkyl glycerol tetraethers gdgts have demonstrated the potential of maar lakes for quantitative paleotemperature reconstruction in this study we review some of the more significant achievements of palaeoclimatic research based on maar lake sediment sequences from china with the focus on chronology multiple timescales and quantitative paleoclimatic reconstruction

glacial interglacial sea surface temperature changes across the subtropical front east of new zealand based on alkenone unsaturation ratios and foraminiferal assemblages 0 are compared to those derived from foraminiferal assemblages using the modern analog technique in two of these cores reconstructions of sst in core tops and holocene sediments agree well with modern average summer temperatures of 18 c in subtropical waters and 14 c in subpolar waters with a 4 5 c gradient across the front down core u37 k 0 sst estimates indicate that the regional summer sst was 4 5 c cooler during the last glaciation with an sst of 10 c in subpolar waters and an sst of 14 c in subtropical waters temperature reconstructions from foraminiferal assemblages agree with those derived from alkenones for the holocene in subtropical waters reconstructions also agree with a glacial cooling of 4 to 14 c in contrast reconstructions for subantarctic pre holocene waters indicate a cooling of 8 c with glacial age warm season water temperatures of 6 c thus the alkenones suggest the glacial temperature gradient across the front was the same or reduced slightly to 3 5 4 c whereas foraminiferal reconstructions suggest it doubled to 8 c our results support previous work indicating that the stf remained fixed over the chatham rise during the last glacial maximum however the differing results from the two techniques require additional explanation a change in euphotic zone temperature profiles seasonality of growth or preferred growth depth must have affected the temperatures recorded by these biologically based proxies regardless of the specific reason a differential response to the environmental changes between the two climate regimes by the organisms on which the estimates are based suggests increased upwelling associated with increased winds and or a shallowing of the thermocline associated with increased stratification of the surface layer in the last glaciation index terms 4267 oceanography general paleoceanography 4850 oceanography biological and chemical organic marine chemistry 1050 geochemistry marine geochemistry 4835 4850 1055 geochemistry organic geochemistry keywords paleoceanography sea surface temperature alkenones southern ocean last glacial maximum

a review of new zealand palaeoclimate from the last interglacial to the global last glacial maximum abstract results from terrestrial and marine palaeoclimate proxies are integrated to reconstruct palaeoclimate variations in new zealand from the last interglacial to the global last glacial maximum glgm by combining data from 21 speleothems we have constructed composite o c stable isotope sequences from 0 to 88 5 ka bp and from 107 8 to 128 2 ka bp the gaps in the sequence a 19 3 ka break in coverage in mis 5b c and a 2 97 ka gap in mis 5a preclude the construct of a continuous record so data were referenced to a common scale by normalising individual records subtracting means and dividing by standard deviation overlapping records were then merged chronologically these records were compared to integrated summer insolation for 45 s and to terrestrial and marine environmental proxies available for the new zealand region the mis 5e thermal maximum in new zealand was around 128 122 kiloyears bp ka bp and therefore similar in timing to the last interglacial in australia southern europe and greenland temperatures in parts of the north island may have been 2 3 c warmer than present and the sea rose 3 6 m above modern level in mis 5d and 5b cool conditions with glacial advances occurred in the south island but from about 87 to 73 ka in mis 5a warmth within 2 c of present characterised most of the interstadial locally termed the otamangakau interstadial conditions then cooled rapidly and culminated in a mis 4 glacial advance that was the greatest of the new zealand last glacial cycle nzlgm the climate was cool to cold and while wet in westerly windward locations may have been dry in the east combined australian and new zealand evidence suggests glacial culmination around 67 62 ka this regional lgm coincided with severe cooling in europe during mis 3 conditions were very variable the climate in eastern north island hawke bay and the bay of plenty at the start of mis 3 was similar to the holocene and the period 61 43 ka was relatively mild overall and is termed the aurora interstadial although it contained a short interval of mountain glacier expansion around 49 47 ka after 43 ka conditions cooled again with a glacial advance from 42 to 38 ka before a return to milder but still cool conditions during the moerangi interstadial from 37 to 31 ka after this conditions deteriorated at the lead in to the glgm the maximum glacial advance occurred in late mis 3 between 31 and 29 ka the glacial onset was abrupt with te anau glacier in fiordland one of the largest in the southern alps taking only about 2000 years to achieve its maximum glgm depth probably because conditions were wet as well as cold but stable isotope data suggest that the climate then became drier while remaining cold and the glacier progressively ablated such that its surface had lowered 390 m by the start of mis 2 and by 600 m by ca 18 ka the glgm maximum in new zealand may have led the terrestrial ice sheet lgm in the northern hemisphere by a few thousand years possibly because alpine glaciers respond more rapidly to climate change than continental ice sheets the culmination of the glgm in nz occurred in mis 3 about 12 000 years before global ice volume reached its peak as determined by the marine stable isotope record the marine glgm by the time global ice volume was at a maximum 19 ka glaciers had almost disappeared from major fiordland valleys in new zealand whereas polar ice sheet records have revealed a bi polar see saw this is not so evident in the mid latitudes because some temperate zone inter hemispheric climate events coincide closely in time perhaps the see saw effect diminishes with distance from the poles

vegetation and climate of auckland new zealand since ca 32 000 cal yr ago support for an extended lgm auckland occupies a climatically sensitive position close to a major biogeographic boundary in the southern mid latitudes a new pollen record from kohuora maar crater auckland displays vegetation and climatic changes for the past ca 32 000 years of particular interest are the inferred climatic patterns for the first part of the interval encompassing the last glacial maximum lgm the kohuora record corresponds closely with pollen records from other auckland sites indicating that the patterns observed are at least regional in extent it is also broadly consistent with a variety of palaeoenvironmental evidence from across new zealand including the glacial record from westland other palynological records from north island other palaeoecological records from the south island and aeolian quartz sequences from western north island these records show that glacial conditions prevailed across most if not all of new zealand during the interval ca 29 19 k cal yr bp longer and earlier than the lgm sensu stricto we suggest that the term extended lgm elgm may be more appropriate for the new zealand region within this predominantly cold interval the auckland pollen records indicate a climatic amelioration for the interval ca 26 24 k cal yr bp also consistent with other palaeocological data from canterbury that fall within a period of climate amelioration recognised between the first two elgm glacial advances in westland we refer to this warming interval as the elgm interstadial the ca 27 k cal yr bp kawakawa oruanui tephra is instrumental in most of these inter site comparisons and occurs after the first peak of elgm cooling in a short lived comparatively mild phase a subsequent return to apparently colder climate in the auckland records may indicate a volcanic cooling effect or more likely widespread landscape disturbance following this major eruption event strong correspondence between biotic responses glacial fluctuations and aeolian quartz deposition linked to major shifts in strength and latitudinal extent of the southern westerlies suggest that both the elgm and elgm interstadial may be more widely registered at least across the southern ocean support for this assertion comes from parallel investigations in western and southernmost south america and isotopic and palaeoecological records from southern ocean marine cores recent reconstructions of the globally averaged ice equivalent sea level history are in line with this evidence from the southern hemisphere suggesting that the elgm may have a global registration in light of these observations we suggest a re examination of the defined timing of the lgm along with renewed effort to establish climatic patterns during this period and understand their causes copyright 2007 john wiley sons ltd

a 28 000 7600 cal yr bp pollen record of vegetation and climate change from pukaki crater northern new zealand a pollen record of vegetation and climate change representing the interval ca 28 000 7600 cal yr bp was obtained from a 52 5 m sediment core taken from a volcanic explosion crater at present sea level in auckland new zealand 36 59 s this provides one of the few continuous terrestrial records covering marine isotope stage 2 and part of stage 1 from the mid latitudes of the southern hemisphere chronology of the record is underpinned by eight distal taupo volcanic zone rhyolitic tephra of known age augmented by thirteen ams radiocarbon dates the last glacial maximum cooling extended from at least c 28 000 cal yr bp to ca 18 000 cal yr bp when vegetation apparently consisted of patches of beech dominated forest embedded within shrubland and grassland forest patches were probably larger or more widespread than those in central north island to the south but less extensive than further to the north in northland climate warming commenced ca 18 000 cal yr bp marked by the replacement of beech by conifers and angiosperms and by the expansion of forest at the expense of shrubland and grassland no clear late glacial climatic reversal is evident at this site early holocene forest is characterised by the replacement of the dominant forest tree prumnopitys taxifolia by dacrydium cupressinum following breach of the crater rim ca 7600 cal yr bp by rising sea level the maar was rapidly infilled with marine sediments over a period of ca 1000 years

geoid anomalies and dynamic topography from convection in cylindrical geometry applications to mantle plumes on earth and venus summary a variety of evidence suggests that at least some hotspots are formed by quasi cylindrical mantle plumes upwelling from deep in the mantle we model such plumes in cylindrical axisymmetric geometry with depth dependent newtonian viscosity cylindrical and sheet like cartesian upwellings have significantly different geoid and topography signatures however rayleigh number nusselt number systematics in the two geometries are quite similar the geoid anomaly and topographic uplift over a plume are insensitive to the viscosity of the surface layer provided that it is at least 1000 times the interior viscosity increasing the rayleigh number or including a low viscosity asthenosphere decreases the geoid anomaly and the topographic uplift associated with an upwelling plume increasing the aspect ratio increases both the geoid anomaly and the topographic uplift of a plume the nusselt number is a weak function of the aspect ratio with its maximum value occurring at an aspect ratio of slightly less than 1

holocene changes in the position and intensity of the southern westerly wind belt the position and intensity of the southern westerly wind belt varies seasonally as a consequence of changes in sea surface temperature during the austral winter the belt expands northward and the wind intensity in the core decreases conversely during the summer the belt contracts and the intensity within the core is strengthened reconstructions of the westerly winds since the last glacial maximum however have suggested that changes at a single site reflected shifts throughout the entire southern wind belt 1 4 here we use sedimentological and pollen records to reconstruct precipitation patterns over the past 12 500 yr from sites along the windward side of the andes precipitation at the sites located in the present core and northern margin of the westerlies is driven almost entirely by the wind belt 5 and can be used to reconstruct its intensity rather than varying coherently throughout the holocene epoch we find a distinct anti phasing of wind strength between the core and northern margin over multi millennial timescales during the early holocene the core westerlies were strong whereas the northern margin westerlies were weak we observe the opposite pattern in the late holocene as this variation resembles modern seasonal variability we suggest that our observed changes in westerly wind strength can best be explained by variations in sea surface temperature in the eastern south pacific ocean chile is ideally located to reconstruct past variability of the southern westerly wind belt sww as the sww almost entirely controls precipitation on the western side of the andes in southern south america with an extreme northsouth

fine resolution pollen record of late glacial climate reversal from new zealand the temporal relationship between rapid climate shifts in the northern and southern hemispheres at the end of the last glacial is crucial to understanding how the global climate system functions during periods of major transition a detailed southern hemisphere mid latitude pollen record from a climatically sensitive and well dated upland site in new zealand unlike previous interpretations shows clear evidence of late glacial climate changes similar in structure to those in the northern hemisphere including a cooling interval from ca 11 600 to 10 700 14 c yr b p because the cooling interval occurred ca 600 14 c yr before the younger dryas chron our record thus also suggests that some global climatic events during the last deglaciation may have registered earlier in the southern hemisphere

deglacial paleoceanographic history of the bay of plenty new zealand 1 we present sea surface temperature sst records with centennial scale resolution from the bay of plenty north of new zealand foraminiferal assemblage based paleo sst estimates provide a deglacial record of sst since 16 5 14c ka average holocene ssts are 15 6 c for winter and 20 3 c for summer whereas average glacial values were 14 2 c for winter and 19 5 c for summer compared to modern time cooling of ssts at the last glacial maximum lgm was 0 9 c in winter and 1 5 c in summer the shift from glacial to holocene temperatures began at 14 25 14c ka warming by 2 c until 12 85 14c ka when temperatures dipped back to glacial values at 11 65 14c ka the timing of this return to glacial like sst correlates well with the antarctic cold reversal acr rather than the younger dryas and documents that the influence of the acr extended into the subtropics of the southern hemisphere at least in this region of the southwest pacific by 10 55 14c ka an sst maximum in summer ssts of up to 3 c warmer than modern occurred 24 c after which sst dropped remaining at present day temperatures since 9 3 14c ka this early holocene climatic optimum has been widely noted in the southern ocean and this record indicates that this phenomenon also extended into the subtropics to the north of new zealand

cooling and changing seasonality in the southern alps new zealand during the antarctic cold reversal abstract a comprehensively 14c ams dated pollen and chironomid record from boundary stream tarn provides the first chironomid derived temperature reconstruction to quantify temperature change during lateglacial times 17 500 10 000 cal yr bp in the southern alps new zealand the records indicate a ca 1000 year disruption to the lateglacial warming trend and an overall cooling consistent with the antarctic cold reversal acr the main interval of chironomid inferred summer temperature depression 2 3 c lasted about 700 years during the acr following this cooling event both proxies indicate a warming step to temperatures slightly cooler than present during the younger dryas chronozone 12 900 11 500 cal yr bp these results highlight a direct linkage between antarctica and mid latitude terrestrial climate systems and the largely asynchronous nature of the interhemispheric climate system during the last glacial transition the greater magnitude of temperature changes shown by the chironomid record is attributed to the response of the proxies to differences in seasonal climate with chironomids reflecting summer temperature and vegetation more strongly controlled by duration of winter or by minimum temperatures these differences imply stronger seasonality at times during the lateglacial which may explain some of the variability between other paleoclimate records from new zealand and have wider implications for understanding differences between proxy records for abrupt climate change

glacial interglacial environmental changes inferred from molecular and compound specific δ13c analyses of sediments from sacred lake mt kenya abstract molecular stratigraphic analyses including lipid distributions and compound specific 13c measurements have been performed at 15 levels in a sediment core from sacred lake mt kenya a high altitude 2350 m a s l freshwater lake with a record extending from the last glacial 40 000 cal yr bp through the present interglacial terrestrial and aquatic organic matter sources were independently assessed using source specific biomarkers 13c values of long chain n alkyl lipids from terrestrial higher plants exhibit large glacial to interglacial shifts those from the last glacial maximum lgm 20 to 18 indicate a terrestrial vegetation dominated by c4 grasses or sedges whereas those from the early holocene 34 to 27 reflect recolonization of the catchment area by c3 plants consistent with a rapid rise in the upper treeline specific algal biomarkers including five unsaturated hydrocarbons of novel structure ascribed to the microalga botryococcus braunii were abundant as confirmed by scanning electronic microscopy sem an extreme 13c shift of over 25 is displayed by the algal biomarkers an elevated value of 5 1 at the last glacial maximum lgm contrasting with a minimum value of 30 3 at the beginning of the holocene a major change in the molecular distributions of the algal biomarkers parallels this large 13c shift with acyclic isoprenoid hydrocarbons dominating the last glacial and cyclic isoprenoid hydrocarbons the holocene the low atmospheric partial pressure of co2 pco2 at the lgm would favour photosynthetic organisms possessing co2 concentrating mechanisms including terrestrial c4 grasses and freshwater green algae hence glacial interglacial changes in pco2 and in the co2 o2 ratio in particular had a significant impact on both terrestrial and aquatic ecosystems on mt kenya in addition to the effects of climate and local environmental factors

sea surface temperatures of southern midlatitudes 0 160 kyr b p 1 late quaternary climate fluctuated between extremes of glaciations lasting 90 kyr on average and interglacial episodes lasting 10 kyr still largely unknown are the spatial and temporal evolution of these global climate states with vigorous debate still underway on the mechanisms responsible for glacial inceptions and terminations though it is widely believed that the southern hemisphere oceans play a central role in global climate changes few paleoclimate records exist from there here we present three new alkenone derived sst records from the midlatitude southern hemisphere spanning the last 160 kyr a full glacial interglacial cycle our subtropical sst records from the last glacial period are characterized by 1 warming 47 23 kyr b p when high latitudes in both hemispheres cooled and 2 milder temperatures during the penultimate glacial period than during the last glacial interval these sst features are found to be of tropical to subtropical wide extent implying increased thermal gradients at times of high latitude ice sheet growth this has implications for the vigor of atmospheric and upper ocean circulation and the transport of heat and moisture to the poles that may have been instrumental in the growth and maintenance of polar ice sheets during glacial periods

the importance of atmospheric input of terrestrial organic material to deep sea sediments the concentrations of lipids were determined in atmospheric particle gas and rain samples collected from the tropical north pacific to assess lipid sources transport mechanisms and fluxes to the ocean surface four lipid compound classes aliphatic hydrocarbons fatty alcohols fatty acid esters and salts all unequivocally show a terrestrial vascular plant source these aerosol lipids originate from wind erosion of asian and american soils and direct emission from vegetation the major fluxes result from rain rather than dry deposition these fluxes are large enough to have a major potential impact on the inventory of terrestrially derived lipid material found in deep sea sediments this has been showm for n alkanes fatty alcohols fatty acids total lipids and for organic carbon by comparing atmospheric and sediment trap fluxes with sediment accumulation rates it is suggested that some biogenic terrestrial material is more protected from degradation than marine derived material

warming and glacier recession in the rakaia valley southern alps of new zealand during heinrich stadial 1 abstract the termination of the last ice age featured a major reconfiguration of earth s climate and cryosphere yet the underlying causes of these massive changes continue to be debated documenting the spatial and temporal variations of atmospheric temperature during deglaciation can help discriminate among potential drivers here we present a 10be surface exposure chronology and glaciological reconstruction of ice recession following the last glacial maximum lgm in the rakaia valley southern alps of new zealand innermost lgm moraines at big ben have an age of 17 840 240 yrs whereas ice marginal moraines or ice molded bedrock surfaces at distances up valley from big ben of 12 5 km lake coleridge 25 km castle hill 28 km double hill 43 km prospect hill and 58 km reischek knob have ages of 17 020 70 yrs 17 100 110 yrs 16 960 370 yrs 16 250 340 yrs and 15 660 160 yrs respectively these results indicate extensive recession of the rakaia glacier which we attribute primarily to the effects of climatic warming in conjunction with geomorphological maps and a glaciological reconstruction for the rakaia valley we use our chronology to infer timing and magnitude of past atmospheric temperature changes compared to an overall temperature rise of 4 65 c between the end of the lgm and the start of the holocene the glacier recession between 17 840 and 15 660 yrs ago is attributable to a net temperature increase of 4 0 c from 6 25 to 2 25 c accounting for 86 of the overall warming approximately 3 75 c 70 of the warming occurred between 17 840 and 16 250 yrs ago with a further 0 75 c 16 increase between 16 250 and 15 660 yrs ago a sustained southward shift of the subtropical front stf south of australia between 17 800 and 16 000 yrs ago coincides with the warming over the rakaia valley and suggests a close link between southern ocean frontal boundary positions and southern mid latitude climate most of the deglacial warming in the southern alps occurred during the early part of heinrich stadial 1 hs1 of the north atlantic region because the stf is associated with the position of the westerly wind belt our findings support the concept that a southward shift of earth s wind belts accompanied the early part of hs1 cooling in the north atlantic leading to warming and deglaciation in southern middle latitudes

the southern hemisphere westerlies in the australasian sector over the last glacial cycle a synthesis abstract the southern hemisphere westerlies in the southwest pacific are known to have waxed and waned numerous times during the last two glacial cycles though even semi continuous histories of the westerlies extend back no more than about 20 000 years we have good evidence for at least three scales of events a westerly maximum occurs at the last glacial maximum there is less conclusive evidence for another westerly maximum in the late holocene and for a minimum at ca 11 ka it is too early to ascribe even a cycle to these data but there are grounds to suggest that milankovitch precessional forcing may underlie the observed pattern there is also a quasi 2600 year cycle present in antarctic ice cores that appears to correlate to variation in westerly flow there is strong centennial scale variability in historical times the little ice age lia ca 1400 1850 was associated with a poleward shift in the circumpolar trough in the southern ocean strengthened westerly circulation over tasmania and a strengthening of southwesterly circulation and neoglaciation in southern new zealand while the preceding period 800 1400 ad was less certainly marked by reduced westerly flow from modern records we know that decadal and inter annual variability is important e g pacific decadal oscillation high latitude mode also known as the antarctic oscillation el nino southern oscillation only a minority of the proxies examined can identify changes on these temporal scales but data from tree rings ice cores and laminated lake sediments do indicate systematic changes in these phenomena through time rossby wave patterns are shown to play a critical role in long duration events as well as at the synoptic scale we conclude that westerly circulation is as strong now as at any time in the last glacial cycle in addition changes in latitudinal boundaries in the westerlies may be nearly as large in inter annual zonal shifts ca 2 maximum as in glaciation interglaciation movements ca 3 4 there is however reasonable evidence of strengthening weakening across much of the westerly belt at westerly maxima minima such as the lia early holocene

glacial water mass structure and rapid δ18o and δ13c changes during the last glacial termination in the southwest pacific abstract changes in ocean circulation are thought to have contributed to lowering glacial atmospheric co 2 levels by enhancing deep ocean sequestration of carbon that was returned to the atmosphere during glacial terminations high resolution benthic foraminiferal 13 c and 18 o records from a depth transect of cores in the southwest pacific ocean presented here provide evidence that both wind and thermohaline driven circulation drove co 2 from the ocean during the last deglaciation shallow geochemical stratification in the glacial southern ocean was followed by a short pulse of rapid 13 c enrichment to intermediate water depths during heinrich stadial 1 indicative of better ventilated intermediate waters co occurring with documented wind driven upwelling in the southern ocean intermediate depth 13 c enrichment paused at the start of the antarctic cold reversal 14 7 ka implying a brief shallow restratification while deeper layers were progressively flushed of 13 c depleted and 18 o enriched waters likely caused by the increasing influence of deep waters sourced from the north atlantic the coincidence of atmospheric co 2 increases with these geochemical shifts in both shallow and deep cores suggests that shifts in both atmospheric and oceanic circulation contributed to the deglacial rise of co 2

regional insolation forcing of late quaternary climate change in the southern hemisphere southern new zealand positioned within the important southwesterly wind system is a prime site for examining interhemispheric linkages in climate change a series of cores drilled in the okarito pakihi peat bog now provides a continuous record of vegetation and climate change that may become a benchmark for the region the data include clear evidence for modification of the global climate change signal in the southern hemisphere by local variation in the intensity of solar radiation in agreement with the milankovitch orbital forcing hypothesis1 it is often assumed that glacial interglacial climate transitions occurred synchronously in the northern and southern hemispheres of the earth it is difficult to test this assumption because of the paucity of long continuous climate records from the southern hemisphere that have not been dated by tuning them to the presumed northern hemisphere signals2 here we present an independently dated terrestrial pollen record from a peat bog on south island new zealand to investigate global and local factors in southern hemisphere climate changes during the last two glacial interglacial cycles our record largely corroborates the milankovitch model of orbital forcing but also exhibits some differences in particular an earlier onset and longer duration of the last glacial maximum our results suggest that southern hemisphere insolation may have been responsible for these differences in timing our findings question the validity of applying orbital tuning to southern hemisphere records and suggest an alternative mechanism to the bipolar seesaw for generating interhemispheric asynchrony in climate change

three dimensional convection planforms with internal heat generation thermal convection planforms in an infinite prandtl number isoviscous fluid layer with basal and internal heating are determined using three dimensional finite difference calculations with basal heating only at rayleigh number ra sub t 1 5 times 10 sup 5 the planform consists of a weakly time dependent spoke pattern with connected networks of equally buoyant up and downwellings with volumetric heat sources the planform is strongly time variable it consists of negatively buoyant flow concentrated in thermal trenches discrete arcuate sheets and spots cylindrical columns separated by diffuse nonbuoyant upwellings rapid planform changes occur primarily by trench propagation as observed experimentally by weinstein and olson this issue the analogy between thermal trenches in internally heated convection and convergent plate boundaries on earth suggests that the global pattern of subduction may evolve by propagation of wadati benioff zones along the strike of the slab

lateglacial landscape and vegetation change and the younger dryas climatic oscillation in new zealand abstract lateglacial sequences in new zealand show progressive afforestation and landscape stabilization reflecting a warming climate between 14 500 bp and 11 500 bp afforestation and landscape stability was achieved throughout most of the north island and the northwest sector of the south island in the south island scrub and tree ferns were replacing previous grasslands in the east by 11 000 bp and broadleaved forest was spreading in the west no significant reversals of these trends occurred and afforestation was complete by 9500 bp glaciers of the high central part of the southern alps made a series of advances between 14 000 and 9000 bp most of these advances are poorly dated but two moraines are of younger dryas age glacial advances in the face of the general lateglacial warming trend may have been driven by stronger westerly winds increasing snowfall on high altitude neves and by reduced ablation as a consequence of moist cloudy low insolation summers the cause of the northern hemisphere younger dryas cooling is still uncertain and expected southern hemisphere responses may differ according to the mechanism proposed for the cooling poor chronological resolution and apparent conflict between the various types of evidence for climatic change make detection of an unambiguous younger dryas in new zealand problematical

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

el nino like pattern in ice age tropical pacific sea surface temperature sea surface temperatures ssts in the cold tongue of the eastern equatorial pacific exert powerful controls on global atmospheric circulation patterns we examined climate variability in this region from the last glacial maximum lgm to the present using a sst record reconstructed from magnesium calcium ratios in foraminifera from sea floor sediments near the galapagos islands cold tongue sst varied coherently with precession induced changes in seasonality during the past 30 000 years observed lgm cooling of just 1 2 c implies a relaxation of tropical temperature gradients weakened hadley and walker circulation southward shift of the intertropical convergence zone and a persistent el nino like pattern in the tropical pacific this is contrasted with mid holocene cooling suggestive of a la nina like pattern with enhanced sst gradients and strengthened trade winds our results support a potent role for altered tropical pacific sst gradients in global climate variations

southern hemisphere westerly wind influence on southern new zealand hydrology during the lateglacial and holocene southern hemisphere westerly wind influence on new zealand hydrology

absence of cooling in new zealand and the adjacent ocean during the younger dryas chronozone as the climate warmed at the end of the last glacial period a rapid reversal in temperature the younger dryas yd event briefly returned much of the north atlantic region to near full glacial conditions the event was associated with climate reversals in many other areas of the northern hemisphere and also with warming over and near antarctica however the expression of the yd in the mid to low latitudes of the southern hemisphere and the southwest pacific region in particular is much more controversial here we show that the waiho loop advance of the franz josef glacier in new zealand was not a yd event as previously thought and that the adjacent ocean warmed throughout the yd

paleovegetation of marine isotope stages 4 and 3 in northern new zealand and the age of the widespread rotoehu tephra abstract paleolake sediment constrained by tephrochronology from onepoto basin volcanic crater in auckland northern new zealand 36 48 s provides one of the few uninterrupted records of paleovegetation for marine oxygen isotope stages mis 4 and 3 76 000 26 000 yr b p in the region this period was characterized by cool temperate conifer hardwood forest that lacked some of the warmer taxa typical of the holocene the period 64 400 60 500 yr b p was marked by opening of forest canopy and expansion of small trees and shrubs and correlates to the thermal minima of mis 4 however the landscape was never as open as the forest shrubland mosaic of the mis 2 the beginning of mis 3 60 500 50 500 yr b p was marked by the dramatic expansion and then decline of conifer hardwood forest dominated by dacrydium cupressinum a species that prefers wetter conditions this forest was succeeded by the typically montane nothofagus at 50 500 yr b p corresponding to a thermal decline thus mis 3 began with an abrupt change to moist cool conditions that lasted about 5000 yr followed by gradual cooling and dryer conditions this supports some interpretations from other parts of the southwest pacific region that mis 3 was a period of increased precipitation the widespread and stratigraphically important rotoehu tephra erupted from okataina volcanic centre has been variously dated at 45 000 65 000 yr b p at onepoto sedimentation rate and paleovegetation reconstruction imply an age of c 44 300 yr b p the tephra provides a correlation horizon in the marine and terrestrial realms during a period mis 3 difficult to date by radiometric methods

glacier retreat in new zealand during the younger dryas stadial the younger dryas a period of sudden cooling in the northern hemisphere about 12 900 years ago is perhaps the best known example of abrupt climate change but the global extent of the younger dryas is a topic of intense debate particularly in the record of glacial behaviour in new zealand a new reconstruction of the growth and retreat patterns of glaciers in the southern alps in new zealand at the time of the younger dryas supports the suggestion that temperature reductions in the north caused warming and glacial retreat in the southern hemisphere through a series of climate feedbacks the younger dryas during which northern hemisphere temperatures cooled drastically in just a few years is perhaps the best known example of abrupt climate change but its global extent is under debate particularly in the record of glacial behaviour in new zealand these authors present evidence for glacial retreat in new zealand during the younger dryas supporting the hypothesis that northern hemisphere climate changes caused southern hemisphere warming through a series of climate feedbacks millennial scale cold reversals in the high latitudes of both hemispheres interrupted the last transition from full glacial to interglacial climate conditions the presence of the younger dryas stadial 12 9 to 11 7 kyr ago is established throughout much of the northern hemisphere but the global timing nature and extent of the event are not well established evidence in mid to low latitudes of the southern hemisphere in particular has remained perplexing1 2 3 4 5 6 the debate has in part focused on the behaviour of mountain glaciers in new zealand where previous research has found equivocal evidence for the precise timing of increased or reduced ice extent1 2 3 the interhemispheric behaviour of the climate system during the younger dryas thus remains an open question fundamentally limiting our ability to formulate realistic models of global climate dynamics for this time period here we show that new zealand s glaciers retreated after 13 kyr bp at the onset of the younger dryas and in general over the subsequent 1 5 kyr period our evidence is based on detailed landform mapping a high precision 10be chronology7 and reconstruction of former ice extents and snow lines from well preserved cirque moraines our late glacial glacier chronology matches climatic trends in antarctica southern ocean behaviour and variations in atmospheric co2 the evidence points to a distinct warming of the southern mid latitude atmosphere during the younger dryas and a close coupling between new zealand s cryosphere and southern high latitude climate these findings support the hypothesis that extensive winter sea ice and curtailed meridional ocean overturning in the north atlantic led to a strong interhemispheric thermal gradient8 during late glacial times in turn leading to increased upwelling and co2 release from the southern ocean9 thereby triggering southern hemisphere warming during the northern younger dryas

isotopic records of tropical vegetation and climate change from terrestrial vascular plant biomarkers preserved in cariaco basin sediments abstract records of vascular plant leaf wax 13 c and d were generated from terrestrial biomarkers preserved in cariaco basin marine sediments and were found to parallel known regional millennial scale climate changes between the late glacial and preboreal periods the terrestrial biomarkers used consisted of c 24 c 32 n alkanoic acids which originate from vascular plant leaf waxes differences in d between c 16 c 18 and c 24 c 30 n alkanoic acid homologues suggest a marine source for the shorter chain lengths and a terrestrial source for the longer chains both the 13 c and d leaf wax records exhibited enrichment during the late glacial and younger dryas and relative depletion during the bolling allerod and preboreal periods d likely records the hydrogen isotopic composition of plant growth water and thus may act as a proxy for local aridity in agreement with cariaco basin sediment grey scale records the d record suggests that the late glacial and younger dryas were more arid than the bolling allerod and preboreal periods n alkanoic acid 13 c which is a proxy for c 3 versus c 4 plant type indicates that c 3 plants predominated in this area of the tropics during warm and wet periods such as the bolling allerod and the early holocene and c 4 plants proliferated during cooler and more arid periods such as the glacial and younger dryas the biomarker 13 c record agrees with pollen data from cariaco basin sediments confirming that leaf wax compounds preserved in marine sediments can accurately record terrestrial vegetation changes

covariability of the southern westerlies and atmospheric co2 during the holocene a suite of mechanisms has been proposed to account for natural variations in atmospheric co 2 during the holocene all of which have achieved limited success in reproducing the timing direction and magnitude of change recent modeling studies propose that changes in the latitudinal position and strength of the southern hemisphere westerly winds sww can greatly influence large scale ocean circulation and degassing of the deep ocean via changes in wind driven upwelling in the southern ocean the extent to which the hypothesized sww southern ocean coupled system could account for changes in atmospheric co 2 is uncertain because of a lack of observations on the behavior of the sww in the past the paucity of appropriate records of productivity changes in the southern ocean and our limited understanding of the sensitivity of the southern ocean biological and or physical system to sww forcing here we report a reconstruction of the behavior of the sww during the past 14 k y based on terrestrial ecosystem proxies from western patagonia south america the reconstructed variations in the intensity of zonal flow correspond to the timing and structure of atmospheric co 2 changes and are consistent with the modeled magnitude of co 2 changes induced by varying strengths of the sww the close match between data and models supports the view that the sww southern ocean coupled system underpins multimillennial co 2 variations during the current interglacial and possibly during glacial cycles over the past 800 k y

trace elements in sulfide inclusions from yakutian diamonds sulfide inclusions in diamonds may provide the only pristine samples of mantle sulfides and they carry important information on the distribution and abundances of chalcophile elements in the deep lithosphere trace element abundances were measured by proton microprobe in 50 sulfide inclusions sdi from yakutian diamonds about half of these were measured in situ in polished plates of diamonds providing information on the spatial distribution of compositional variations many of the diamonds were identified as peridotitic or eclogitic from the nature of coexisting silicate or oxide inclusions known peridotitic diamonds contain sdis with ni contents of 22 36 consistent with equilibration between olivine monosulfide solid solution mss and sulfide melt whereas sdis in eclogitic diamonds contain 0 12 ni a group of diamonds without silicate or oxide inclusions has sdis with 11 18 ni and may be derived from pyroxenitic parageneses eclogitic sdis have lower ni cu and te than peridotitic sdis the ranges of the two parageneses overlap for se as and mo the mo and se contents range up to 700 and 300 ppm respectively the highest levels are found in peridotitic diamonds among the in situ sdis significant zn and pb levels are found in those connected by cracks to diamond surfaces and these elements reflect interaction with kimberlitic melt significant levels of ru 30 1300 ppm and rh 10 170 ppm are found in many peridotitic sdis sdis in one diamond with wustite and olivine inclusions and complex internal structures have high levels of other platinum group elements pges as well and high chondrite normalized ir pd comparison with experimental data on element partitioning between crystals of monosulfide solid solution mss and sulfide melts suggests that most of the inclusions in both parageneses were trapped as mss while some high cu sdis with high pd rh may represent fractionated sulfide melts spatial variations of sdi composition within single diamonds are consistent with growth histories shown by cathodoluminescence images in which several stages of growth and resorption have occurred within magmatic environments that evolved during diamond formation

timing of the late glacial climate reversal in the southern hemisphere using high resolution radiocarbon chronology for kaipo bog new zealand abstract the pattern of climate change in the southern hemisphere during the younger dryas yd chronozone provides essential constraint on mechanisms of abrupt climate change only if accurate high precision chronologies are obtained a climate reversal reported previously at kaipo bog new zealand had been dated between 13 600 and 12 600 cal yr b p and appeared to asynchronously overlap the yd chron but the chronology based on conventionally radiocarbon dated bulk sediment samples left the precise timing questionable we report a new high resolution ams 14 c chronology for the kaipo record that confirms the original chronology and provides further evidence for a mid latitude southern ocean cooling event dated between 13 800 and 12 400 cal yr b p 2 range roughly equivalent to the antarctic cold reversal

the dependence of convection planform on mode of heating a fundamental property of a convecting fluid is its planform the distribution in the horizontal plane of hot rising regions and cold sinking regions for the earth s mantle the planform might he visualized as a map of subduction zones hotspots and possibly ocean ridges here i report numerical experiments of convection at high rayleigh number which show a strong dependence of planform on heating mode when heat generation is distributed uniformly through the box the preferred planform consists of an ensemble of time dependent cold axial sinkers distributed in a hot diffuse upward flow when half of the heat is generated within the box and the other half is input through the base the preferred planform consists of an array of hot axial plumes and elongated cold sheets in the former case the mean horizontal wavelength is about equal to the layer depth for the latter it is about twice the layer depth

flow discharge influences on input and transport of particulate and sedimentary organic carbon along a small temperate river abstract the relative importance of hydrological conditions and upstream processes on the input and transport of organic carbon from land to sea was investigated in the mullica river a small system located in the southeastern new jersey usa using molecular and 13c compositions sediment and particulate organic carbon poc samples were collected along the river from upstream draining predominantly pine oak forests in the pinelands to the great bay estuary bordered by salt marshes under normal and high flow conditions during base river flow terrestrial biomarkers e g diterpenoids conifer biomarkers were detected predominantly upstream and sharply decreased downstream from mid to down river sites a mixture of higher plants primarily from the salt marsh vegetation and microbial biomarkers e g mycose cholesterol predominated 13c abundances of individual fatty acids presented a consistent pattern with depleted values e g 13csed 30 9 on average upstream becoming heavier toward the great bay e g 13csed 23 1 13cpoc 22 8 during the high discharge event significant amounts of upland biomarkers e g pimaric acid ferruginol ursolic acid and depleted 13c values were observed from the pinelands 13csed 34 6 to mid river 13csed 32 0 13cpoc 30 8 clearly demonstrating the transport of terrestrial material farther down river however downstream of this point the occurrence of the terrestrial material strongly decreased demonstrating that terrestrial plant biomarkers were not transported in significant amounts to the estuarine region even at high river discharge since the mid river site is situated in the upper limit of salt water intrusions it is likely that flocculation and sedimentation provide a depositional sink for terrestrial oc in the mid mullica river thereby depleting the terrigenous signature in downstream oc

convection with internal heat sources and thermal turbulence in the earth s mantle summary the influence of internal heat sources on mantle convection is investigated using numerical calculations of 2 d thermal convection in an infinite prandtl number incompressible fluid the geometry is a cylindrical annulus with inner and outer radii in proportion to the whole mantle time dependent calculations are made starting from random initial conditions with rayleigh numbers rat based on boundary temperature difference and ra based on internal heat production in the range 1dsrats lo7 and osra 524rat at fixed rat increasing ra results in transitions in flow structure from steady cells to a pattern of stationary cells with time variable amplitude and finally to thermally turbulent convection with a non stationary cell count for rat 10 and ra rat approximately the travelling plumes disrupt the large scale circulation producing turbulent convection at ra lo7 the flow is fully developed thermal turbulence and for ra 0 consists of a rapidly fluctuating irregular flow driven by transient rising and sinking sheets of buoyant fluid large fluctuations in total kinetic energy occur in this regime with periodicities ranging from 40 to 1400myr the transition to thermal turbulence occurs in these calculations at rayleigh numbers well below the value estimated for subsolidus convection in the mantle suggesting thermally turbulent convection may occur in the mantle a consequence of internal heat sources thermal turbulence offers an explanation for long term fluctuations in the rate of subduction sea floor spreading and global volcanic activity

zonally symmetric changes in the strength and position of the southern westerlies drove atmospheric co2 variations over the past 14 k y terrestrial records from 41 to 52 s across the southern hemisphere reveal nearly synchronous multimillennial trends in moisture derived from the southern westerly winds sww since 14 ka pointing to a marked zonal symmetry in sww changes across a broad swath of the southern middle latitudes the data suggest a southward shift of the sww that coincided with a rapid atmospheric co 2 rise starting ca 12 5 ka a widespread decline in sww strength between ca 10 and 7 ka contemporaneous with an 8 ppm reversal in the deglacial atmospheric co 2 rise followed by stronger sww and a steady multimillennial increase in co 2 until the preindustrial maximum we conclude that zonally symmetric changes in the intensity of the sww at multimillennial time scales have covaried with atmospheric co 2 variations since 14 ka and suggest that changes in the sww southern ocean coupled system have influenced the atmospheric co 2 concentration through wind driven upwelling of co 2 rich deep waters in the high southern latitudes

possible enso signals prior to the last glacial maximum during the last deglaciation and the early holocene from new zealand annually laminated lake sediments from a maar crater in auckland new zealand were analyzed spectrally for three time slices just prior to the last glacial maximum lgm during the deglaciation and during the early holocene strong spectral power in 2 7 year 9 30 year and a centennial 80 120 year timescale prior to the lgm and during two brief intervals in the deglaciation contrasts with virtually no spectral power during the rest of the deglaciation and during the early holocene the antarctic cold reversal acr appears to be the younger deglacial event the results indicate that el nino southern oscillation enso and possibly the inter decadal pacific oscillation ipo operated in a modern mode prior to the lgm pulsed on and off during the deglaciation and were suppressed or absent from northern new zealand during the early holocene the acr was a period of enhanced southwesterly flow over northern new zealand