integration of ice core marine and terrestrial records for the australian last glacial maximum and termination a contribution from the oz intimate group the degree to which southern hemisphere climatic changes during the end of the last glacial period and early holocene 30 8 ka were influenced or initiated by events occurring in the high latitudes of the northern hemisphere is a complex issue there is conflicting evidence for the degree of hemispheric teleconnection and an unresolved debate as to the principle forcing mechanism s the available hypotheses are difficult to test robustly however because the few detailed palaeoclimatic records in the southern hemisphere are widely dispersed and lack duplication here we present climatic and environmental reconstructions from across australia a key region of the southern hemisphere because of the range of environments it covers and the potentially important role regional atmospheric and oceanic controls play in global climate change we identify a general scheme of events for the end of the last glacial period and early holocene but a detailed reconstruction proved problematic significant progress in climate quantification and geochronological control is now urgently required to robustly investigate change through this period copyright c 2006 john wiley sons ltd

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

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

old radiocarbon ages in the southwest pacific ocean during the last glacial period and deglaciation marine radiocarbon 14c dates are widely used for dating oceanic events and as tracers of ocean circulation essential components for understanding ocean climate interactions past ocean ventilation rates have been determined by the difference between radiocarbon ages of deep water and surface water reservoirs but the apparent age of surface waters currently approximately 400 years in the tropics and approximately 1 200 years in antarctic waters might not be constant through time as has been assumed in radiocarbon chronologies and palaeoclimate studies here we present independent estimates of surface water and deep water reservoir ages in the new zealand region since the last glacial period using volcanic ejecta tephras deposited in both marine and terrestrial sediments as stratigraphic markers compared to present day values surface reservoir ages from 11 900 14c years ago were twice as large 800 years and during glacial times were five times as large 2 000 years contradicting the assumption of constant surface age furthermore the ages of glacial deep water reservoirs were much older 3 000 5 000 years the increase in surface to deep water age differences in the glacial southern ocean suggests that there was decreased ocean ventilation during this period

the chronology of palaeoenvironmental changes during the last glacial holocene transition towards an event stratigraphy for the british isles the overall aim of the tigger iib project is to increase our understanding of the manner and rates by which ecosystems responded to climate changes during the last glacial holocene transition success in this venture requires better constrained palaeoenvironmental reconstructions than have been achieved thus far and the tigger project focused in particular on three main aims 1 off setting the limitations of conventional radiocarbon dating in order to provide a more secure chronology of events 2 increasing the resolution and precision of palaeoclimatic reconstructions 3 widening the scope of site specific palaeoecological investigations in this paper we focus on the first of these strategies and describe the progress made in developing a more coherent timescale for the climate history of the lateglacial period this has been achieved by using a number of independent methods including calibration of ams radiocarbon dates obtained from terrestrial plant macrofossils mcr estimates of summer temperatures based on coleopteran records analysis of stable carbon isotope ratios in terrestrial plant macrofossils and tephrochronology following bjorck et al 9s 1998 recommendations we integrate the new results to construct a provisional event stratigraphy for the last glacial holocene transition in the british isles which is based on a sequence of features that are believed to be time parallel this approach is considered to provide a more coherent framework for direct comparison of the palaeoenvironmental evidence from britain with that from elsewhere

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

interaction of small mantle plumes with the spinel perovskite phase boundary implications for chemical mixing abstract geochemical observations of ocean island basalts show a broad variety in the chemical composition of trace elements these observations cannot be explained by different temperature and pressure conditions at the melt production region only but also demand differences in the parental material at the base of the lithosphere here we add a new explanation for this finding based on the different interaction of small and large plumes with the spinel perovskite phase boundary spb in the earth s mantle we assume that mantle plumes detaching from the core mantle boundary cmb are of variable size and excess temperature while rising through the lower mantle they form an approximately spherical plume head when arriving at the spb they are retained from further rise depending on their size and excess temperature we have investigated the interaction of a plume with the spb using a numerical approach for viscous flow to focus particularly on this interaction we simply modelled the initial plume as a hot volume of variable cross section and excess temperature volumes with a radius exceeding about 150 km and an excess temperature of more than 100 c rapidly cross the spb with decreasing size and increasing excess temperature volumes are retarded at the spb and those with a radius smaller than about 80 km stagnate entirely below the spb these results are roughly independent of the particular rheology or two dimensional versus three dimensional geometry in the present study we investigated the degree of thermal entrainment of material at the spb for strongly retarded plumes we estimate the amount of chemical mixing by tracking passive markers from the original plume volume and the regions around the spb to the base of the lithosphere the amount of entrainment of material from close to the spb depends on the retardation time and the thermal growth of the plume head at the spb plume heads which reach the base of the lithosphere after a retardation time of more than 50 ma might entrain in the numerical model large amounts of material from the sbp but they may not be characteristic for the earth since they might be distorted by large scale mantle flow however even if we limit the retardation time to reach the base of the lithosphere to 50 ma plumes originally composed of material from the cmb and the adjacent lower mantle might easily entrain up to 15 of their volume of material originating from the spb

chironomid and pollen evidence for climate fluctuations during the last glacial termination in nw patagonia abstract we present chironomid and pollen records from the huelmo site 41 30 s nw patagonia to examine in detail the timing and structure of climate changes during the last glacial termination in the southern mid latitudes the chironomid record has the highest temporal and taxonomic resolution for this critical interval and constitutes the first account of midge faunas at the culmination of the last glacial maximum lgm for the region the chironomid record suggests cold and wet conditions during the lgm followed by deglacial warming between 17 6 and 16 8 cal kyr bp relatively warm conditions prevailed between 15 14 cal kyr bp followed by a reversal in trend with cooling pulses at 14 and 13 5 cal kyr bp and warming at the beginning of the holocene cool temperate conditions prevailed during the huelmo mascardi cold reversal hmcr which according to chironomid data exhibits a wet phase 13 5 12 8 cal kyr bp followed by a conspicuous drier phase 12 8 11 5 cal kyr bp the chironomid and pollen records from the huelmo site indicate step wise deglacial warming beginning at 17 6 cal kyr bp in agreement with other paleoclimate records from nw patagonia and isotopic signals from antarctic ice cores peak warmth during the last glacial termination was achieved by 14 5 cal kyr bp followed by a cooling trend that commenced during the antarctic cold reversal which later intensified and persisted during the hmcr 13 5 11 5 cal kyr bp we observe a shift toward drier conditions at 12 8 cal kyr bp superimposed upon the hmcr coeval with intense fire activity and vegetation disturbance during younger dryas time

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

the younger dryas relevant in the australian region an assessment of australian climate during the younger dryas chronozone ydc is presented this review focuses on securely dated records from sites of continuous deposition placing greatest emphasis on temperature reconstructions with records of effective precipitation i e the combined effect of precipitation minus evapotranspiration also considered while there is a paucity of australian records covering the last glacial interglacial transition particularly those which directly infer temperature sufficient data exist to examine ydc climate from southern and eastern australia temperature reconstructions from tasmania based on both chironomid and pollen data show no evidence for younger dryas cooling by contrast there is evidence for cooling associated with the antarctic cold reversal from tullabardine dam pollen data and the sediment organic content from eagle and platypus tarns in tasmania records from a number of eastern australian mainland sites provide no evidence of effective precipitation shifts concurrent with the younger dryas chronozone similarly reconstructions of discharge from the murray darling basin which covers a large proportion 14 of the australian continent and dust transport from a larger portion of the continent also show no evidence of climate shifts concomitant with the younger dryas of research published in the past decade only one study located in the great australian bight claims evidence of a ydc cooling andres et al 2003 by contrast this review suggests that there is no conclusive evidence for cooling or indeed any distinctive climate patterning during the younger dryas chronozone in australia

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

mechanisms of abrupt climate change of the last glacial period 1 more than a decade ago ice core records from greenland revealed that the last glacial period was characterized by abrupt climate changes that recurred on millennial time scales since their discovery there has been a large effort to determine whether these climate events were a global phenomenon or were just confined to the north atlantic region and also to reveal the mechanisms that were responsible for them in this paper we review the available paleoclimate observations of abrupt change during the last glacial period in order to place constraints on possible mechanisms three different mechanisms are then reviewed ocean thermohaline circulation sea ice feedbacks and tropical processes each mechanism is tested for its ability to explain the key features of the observations particularly with regard to the abruptness millennial recurrence and geographical extent of the observed changes it is found that each of these mechanisms has explanatory strengths and weaknesses and key areas in which progress could be made in improving the understanding of their long term behavior both from observational and modeling approaches are suggested finally it is proposed that a complete understanding of the mechanisms of abrupt change requires inclusion of processes at both low and high latitudes as well as the potential for feedbacks between them some suggestions for experimental approaches to test for such feedbacks with coupled climate models are given

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

inter regional correlation of palaeoclimatic records for the last glacial interglacial transition a protocol for improved precision recommended by the intimate project group the remit of the intimate project of the inqua palaeoclimate commission is to synthesise marine terrestrial andice core data for the north atlantic region during the last glacial interglacial transition lgit ca 13 10c kyr bp ca 15 11 5 ice core kyr bp a major problem however is the di culty of e ecting correlations at a temporal resolution that are adequate for de ning leads and lags between the polar ice terrestrial marine andatmospheric realms the limitations of the d ating andcorrelation method s currently employed are summarised and new quality assurance protocols are proposed these include recommendations on the contextual information that should accompany radiocarbon dates procedures for radiocarbon calibration the use of an eventstratigraphic approach in inter regional correlations andthe more widespreaduse of time parallel marker horizons basedon tephra layers oxygen isotope stratigraphy palaeomagnetic stratigraphy andradiocarbon wiggle matching to underpin the geochronology and correlation of events during the lgit these protocols will be adopted by the intimate project in future international collaborative research and are recommended to other groups working on this important time period 2001 elsevier science ltd all rights reserved

iron ore mining promotes iron enrichment in sediments of the gualaxo do norte river basin minas gerais state brazil the objective of the present study is to assess the influence of iron ore mining on fe concentrations in fluvial sediments of the gualaxo do norte river basin minas gerais state brazil initially background values were determined for fe by means of the boxplot representation the iterative 2 technique and the calculated distribution function using geochemical data obtained for alluvial terraces geochronologic analyses in carbonaceous materials attested for the proposed background values after that chemical analyses of active drainage sediments collected along the entire basin were carried out and a geochemical map of the study area was prepared the mean background value for fe is relatively high 8 2 wt when compared to the fe concentration in the earth s crust 5 6 wt such background value is strongly associated with the geological characteristics of the region it was observed that most of the high fe concentrations were detected in active sediments collected in the main river of the basin and not in its tributaries this suggests that fe enrichment is not only linked to the local geology but also to possible increase resulting from accidental leakage of iron ore mining tailings from containment dams and lakes upstream it is suggested that measures that help stop or minimize such impact be adopted the large capacity of fe to adsorb and form complexes with toxic metals implicates in environmental hazards that may not be restricted only to the gualaxo do norte river basin but may affect the other basins downstream

the last glacial holocene transition in southern chile warming at the last glacial termination in the north atlantic region was interrupted by a period of renewed glacial activity during the younger dryas chronozone ydc the underlying mechanism of this cooling remains elusive but hypotheses turn on whether it was a global or a north atlantic phenomenon chronological sedimentological and palaeoecological records from sediments of small lakes in oceanic southern chile demonstrate that there was no ydc cooling in southern chile it is therefore likely that there was little or no cooling in southern pacific surface waters and hence that ydc cooling in the north atlantic was a regional rather than global phenomenon

new zealand and uk holocene flooding demonstrates interhemispheric climate asynchrony the timing and controls of interhemispheric holocene climate change have remained poorly understood primarily because of the absence of well dated and continuous climatic records in terrestrial environments here we report a new probability based meta analysis of 1185 14 c dates from fluvial sedimentary sequences in new zealand and the uk which provides a robust means of identifying centennial and multicentennial length episodes of holocene river flooding statistical analysis shows that prior to large scale human impact which began at ca 1000 cal yr b p the incidence of extreme floods in new zealand and the uk has been largely asynchronous during the holocene major periods of flooding are controlled by large scale shifts in atmospheric circulation which alter the frequency of extreme precipitation events our novel synthesis demonstrates that short term climate change of sufficient magnitude to modify flooding regimes was out of phase in the temperate maritime regions of the northern and southern hemispheres during much of the holocene this supports recent evidence from both glacial and marine records that holocene climate changes may have been antiphased between the polar regions and that this could have been related to variation in the strength of deep water formation

paleocean circulation during the last deglaciation a bipolar seesaw hughen et al 1998 have documented that during the first 200 years of younger dryas time the 14c content of atmospheric co2 increased by 50 and that during the remainder of this 1200 year duration cold event it steadily declined the initial increase in 14c c was likely the result of a reduction in the atlantic s conveyor circulation however were the subsequent radiocarbon decline due to the rejuvenation of this potent heat pump then it is difficult to understand why the climate conditions in the northern atlantic basin remained cold throughout the younger dryas modeling exercises by stocker and wright 1996 mikolajewicz 1998 and schiller et al 1998 show that if the conveyor is terminated the transfer of radiocarbon into the deep sea shifts to the southern ocean thereby stabilizing the atmospheric 14c c ratio paleoclimatic evidence from the antarctic continent suggests that this model based scenario might have been played out in the real world while the younger dryas cooling has been documented in many places around the world including new zealand denton and hendy 1994 sowers and bender 1995 using their 18o in o2 based correlation between the ice core 18o in ice records for antarctica and greenland have demonstrated that in antarctica the younger dryas was a time of maximum warming the point of this paper is that the steep rise in 18o rise in antarctic ice which commenced close to the onset of the younger dryas might have been caused by heat released to the atmosphere in response to an increase in deep sea ventilation in the southern ocean

temperature change is the major driver of late glacial and holocene glacier fluctuations in new zealand advance and retreat of temperate glaciers is largely controlled by changes in temperature and precipitation but the relative importance of these drivers is debated numerical modeling of a new zealand glacier reveals that temperature is the dominant control on glacier length we find that a glacial advance dated to ca 13 000 yr b p requires a cooling event of 3 4 c this mid latitude southern hemisphere cooling is similar in magnitude to the antarctic cold reversal in the vostok ice core record and likely to be a response to the same climate signal

evidence for a landslide origin of new zealand s waiho loop moraine the waiho loop moraine has been interpreted as evidence for younger dryas cooling in southern new zealand but recent dating and climatological studies have questioned this idea a detailed analysis of the sedimentology of the moraine suggests it was formed after a large landslide onto the franz josef glacier triggered a glacial surge independent of climate forcing

synchronous climate changes in antarctica and the north atlantic central greenland ice cores provide evidence of abrupt changes in climate over the past 100 000 years many of these changes have also been identified in sedimentary and geochemical signatures in deep sea sediment cores from the north atlantic confirming the link between millennial scale climate variability and ocean thermohaline circulation it is shown here that two of the most prominent north atlantic events the rapid warming that marks the end of the last glacial period and the bolling allerod younger dryas oscillation are also recorded in an ice core from taylor dome in the western ross sea sector of antarctica this result contrasts with evidence from ice cores in other regions of antarctica which show an asynchronous response between the northern and southern hemispheres

renewed glacial activity during the antarctic cold reversal and persistence of cold conditions until 11 5 ka in southwestern patagonia resolving the timing direction and magnitude of paleoclimate changes in the southern midlatitudes is a prerequisite for determining the mechanisms underlying abrupt and widespread climate changes between the hemispheres during the last glacial interglacial transition lgit this issue is still debated with previous studies producing apparently discordant fi ndings here we show evidence for a glacial readvance and a cold episode between ca 14 8 and 12 6 ka in southwestern patagonia 50 s contemporaneous with the antarctic cold reversal this was followed by ice recession under cold but relatively milder conditions until ca 11 5 ka when paleovegetation records indicate the onset of warm interglacial conditions these fi ndings differ from those reported in northern patagonia 40 s where deteriorating conditions before 13 5 ka were followed by the coldest part of the lgit that lasted until ca 11 5 ka we interpret the apparent blend of greenlandic and antarctic cold phases as evidence for their co occurrence in the southern middle latitudes in patagonia and hypothesize that the position of the antarctic polar front modulated the strength of these cold events in regions to the north or south of it

the role of egmont sourced tephra in evaluating the paleoclimatic correspondence between the bio and soil stratigraphic records of central taranaki new zealand abstract on the lower eastern flanks of egmont volcano western north island new zealand several egmont sourced tephras have been correlated to a radiocarbon dated peat site that provides a late last glacial to early post glacial record of vegetation and climate change in central taranaki the pollen spectra at this site indicates a mosaic of grassland shrubland and prumnopitys taxifolia dominant forest at ca 13 100 bp and suggests a climate cooler and drier than at present the ominance of tall podocarp forest by ca 12 900 bp suggests that climatic amelioration was rapid towards the end of the last glacial period initially this forest was dominated by prumnopitys taxifolia but at ca 11 000 bp was succeeded by dacrydium cupressinum indicating a steady shift to warmer and moister climate tephra interbedded with peat allows precise chrono correlation into the andisol forming environment the rapidity of climatic amelioration identified from variations in andisol morphology and mineralogy concurs with that indicated from pollen changes in the peat

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

a detailed 31 000 year record of climate and vegetation change from the isotope geochemistry of two new zealand speleothems abstract uranium series dating and stable isotope analyses of two speleothems from northwest nelson new zealand record changes in regional climate and local forest extent over the past 31 000 years oxygen isotope variation in these speleothems primarily represents changes in the meteoric waters falling above the caves possibly responding to latitudinal changes in the position of the subtropical front in the tasman sea seven positive excursions can be identified in the oxygen isotope record which coincide with periods of glacier advance known to be sensitive to northward movement of the subtropical front four glacier advances occurred during oxygen isotope stage 2 with the most extreme glacial conditions centered on 19 000 cal yr b p 2 an excursion in the oxygen isotope record from 13 800 to 11 700 cal yr b p provides support for a previously identified new zealand glacier advance at the time of the younger dryas stade but suggests it began slightly before the younger dryas as recorded in greenland ice cores carbon isotope variations in the speleothems record changes in forest productivity closely matching existing paleovegetation records on the basis of vegetation changes stage 2 glacial climate conditions terminated abruptly in central new zealand from 15 700 to 14 200 cal yr b p evidence of continuous speleothem growth at one site suggests that depression of the local treeline was limited to 600 700 m below its present altitude throughout the last 31 000 years

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

sea level fingerprinting as a direct test for the source of global meltwater pulse ia the ice reservoir that served as the source for the meltwater pulse ia remains enigmatic and controversial we show that each of the melting scenarios that have been proposed for the event produces a distinct variation or fingerprint in the global distribution of meltwater we compare sea level fingerprints associated with various melting scenarios to existing sea level records from barbados and the sunda shelf and conclude that the southern laurentide ice sheet could not have been the sole source of the meltwater pulse whereas a substantial contribution from the antarctic ice sheet is consistent with these records

geophysical evidence of multiple glacier advances in lago fagnano 54 s southernmost patagonia the island of tierra del fuego at the southernmost extreme of patagonia is located in one of the most extensively glaciated areas of the southern hemisphere outside antarctica during the late pleistocene the lago fagnano region at w54 30 0 s and w68 w has experienced several phases of glacier growth and retreat since the last glacial maximum lgm we illustrate these phases using combined geomorphological geophysical and coring surveys in lago fagnano itself a w105 km long e w oriented glaciotectonic basin we identify and map a complex set of submerged frontal central and lateral moraines covered by lacustrine sediments using seismic stratigraphic analysis of multi channel profiles imaging the sub lake floor we then combine these geophysical data with field observations and regional maps of similar structures around the lake to reconstruct the spatial behavior of the fagnano paleo glacier since the lgm we interpret the preserved frontal moraines as having formed during at least 20 re advance stages of the glacier within a long term deglaciation interval post lgm preliminary tephrochronological dating of a w7 5 m long core indicates a step wise deglaciation pattern comprising a final glacier re advance stage at w11 2 ka bp

glacial interglacial control of terrigenous and biogenic fluxes in the deep ocean off a high input collisional margin a 139 kyr record from new zealand abstract sediment input to the deep ocean off the new zealand collisional plate boundary is large and variable as revealed by a 139 kyr old record from the 34 92 m long core md97 2121 mass accumulation rates mars were derived for terrigenous and biogenic carbonate and silica sedimentary components with temporal control from a stable isotope age model verified by tephra and radiocarbon ages terrigenous mars changed in phase with glacio eustatic fluctuations of sea level highest rates 30 g cm 2 kyr coincided with the late regressive lowstand early transgressive phase of marine isotope stage mis 2 when rivers discharged at or near the shelf edge lesser but still high terrigenous rates 20 30 g cm 2 kyr characterized peak warm phases of early mis 5 and 1 when a strengthened subtropical inflow probably introduced sediment from fluvial and seabed sources to the north of md97 2121 however during prolonged highstands the flux declined as more sediment was retained on a tectonically subsiding shelf with a shore parallel current paradoxically the lowest mars 10 5 g cm 2 kyr occurred in mis 4 either sea level was too high to allow much sediment to escape off shelf or the fluvial input was modest or both these factors despite the terrigenous dominance biogenic mars are high and are 2 4 times larger than sw pacific ocean rates mars were lowest during mis 4 and 3 possibly due to reduced marine production under a lowered input of fluvial micronutrients in contrast mars increased irregularly though glacial maxima to peak at 5 6 g cm 2 kyr carbonate and 2 2 5 g cm 2 kyr silica in early mid mis 5 and 1 such rates reflected the interaction of macronutrient rich subantarctic waters sourced from the south with local micronutrient rich subtropical waters production also responded to warmer temperatures elevated nutrient runoff and a more stratified surface ocean later in mis 5 and 1 fluxes reduced as less productive subtropical waters prevailed that biogenic and aeolian mar profiles are out of phase suggests fe fertilization by aerosolic dust was not a major influence

new zealand maritime glaciation millennial scale southern climate change since 3 9 ma ocean drilling program site 1119 is ideally located to intercept discharges of sediment from the mid latitude glaciers of the new zealand southern alps the natural gamma ray signal from the site s sediment core contains a history of the south island mountain ice cap since 3 9 million years ago ma the younger record to 0 37 ma resembles the climatic history of antarctica as manifested by the vostok ice core beyond and back to the late pliocene the record may serve as a proxy for both mid latitude and antarctic polar plateau air temperature the gamma ray signal which is atmospheric also resembles the ocean climate history represented by oxygen isotope time series

an oceanic cold reversal during the last deglaciation a detailed deuterium excess profile measured along the dome c epica european project for ice coring in antarctica core reveals the timing and strength of the sea surface temperature changes at the source regions for dome c precipitation we infer that an oceanic cold reversal took place in the southern indian ocean 800 years after the antarctic cold reversal the temperature gradient between the oceanic moisture source and antarctica is similar to the dome c sodium profile during the deglaciation illustrating the strong link between this gradient and the strength of the atmospheric circulation

evidence against a significant younger dryas cooling event in new zealand pollen records of deglacial sequences from northwest nelson new zealand demonstrate that there was no significant temperature decline associated with the younger dryas in new zealand records of glacial advances at this time were either the product of increased snow accumulation under enhanced precipitation regimes or random variation rather than the result of a regional thermal decline this finding supports those models of younger dryas initiation that require neither enhanced westerly circulation nor significant thermal decline in the southern hemisphere

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

variability and seasonality of north atlantic climate during the early holocene evidence from faroe island lake sediments based on their position in relation to major ocean currents palaeoclimatic archives in the faroe islands are expected to be sensitive recorders of variations in north atlantic circulation the multiproxy analysis magnetic susceptibility total carbon nitrogen and sulphur biogenic silica grains 255 mu m of a lacustrine record with both winter and summer climate indicators illustrates the variability of faroese climate during the early holocene c 11 300 10 240 cal yr bp and allows comparison with other records in the region our high resolution record suggests a period of predominantly winter cooling and increased storminess centred at c 11 150 cal yr bp followed by a period of stability between c 11 000 and 10 680 cal yr bp which correlates with a time when the north atlantic was particularly free of meltwater incursions after c 10 680 cal yr bp both winter and summer indicators show an increase in variability broadly synchronous with increased variability at other north atlantic sites within this time period a predominantly winter cooling centred at c 10 600 cal yr bp a winter summer cooling centred at c 10 450 cal yr bp and a winter summer cooling centred at c 10 300 cal yr bp are recorded these distinctive coolings correspond to periods of ice core delta o 18 inferred lowered atmospheric temperatures over greenland and the reoccurrence of meltwater outbursts at c 10 600 10 500 and 10 350 cal yr bp less

onset and termination of the late glacial climate reversal in the high resolution diatom and sedimentary records from the annually laminated sg06 core from lake suigetsu japan high resolution diatom sediment and pollen analyses of two sections from the annually laminated sg06 core from lake suigetsu were used to study the onset and termination of the late glacial climate reversal in central japan its broadly recognised counterpart is the younger dryas or greenland stadial 1 ca 12 85 11 65 cal kyr bp based on the ngrip ice core records our study suggests that accumulation of the analysed late glacial sediments occurred in a deep and relatively cold water meso eutrophic lake with a strong mixing regime and relatively high silica content combining these results together with available pollen based environmental reconstructions we suggest that climate cooling together with an intensified winter monsoon and thicker snow cover could influence changes in regional vegetation sedimentation processes and trophic status of the lake during the transition from the last interstadial to stadial around lake suigetsu a decrease in total pollen concentration and increase in fagus pollen percentage indicate local vegetation stress disturbances and suggest that cooling started at least 2 3 decades prior to the major shift in the inorganic sediment accumulation of detrital layers and in diatom assemblages change from aulacoseira ambigua to aulacoseira subarctica dominance which took about 10 years the transition from the last stadial to the holocene again shows that vegetation in the lake catchment area reacted first to the regional climate change i e to the weakening of the winter monsoon and decrease in winter snow accumulation the increase in the vegetation cover density and reduced volume of surface runoff associated with the decrease in melt water supply is likely responsible for the reduced soil erosion activity which caused the cessation in detrital layer accumulation and consequent decrease in the amount of nutrients brought to the lake and lowering of the water nutrient status the latter process finally influenced changes in the diatom assemblages including the return to dominance of a subarctica ca 30 years after the virtual disappearance of detrital layers from the sediment our results demonstrate the rapid response of the lake suigetsu system to the global cooling and subsequent warming and allow clear definition of the onset and termination of the late glacial climate reversal despite the fact that the lake system shows a more abrupt shift from the warm to cold and cold to warm environments than terrestrial records of vegetation demonstrate we do not see any delayed response of local vegetation to the climate change this last conclusion is of particular importance for application of the sg06 pollen record for quantitative climate reconstruction

synchronous radiocarbon and climate shifts during the last deglaciation radiocarbon data from the cariaco basin provide calibration of the carbon 14 time scale across the period of deglaciation 15 000 to 10 000 years ago with resolution available previously only from holocene tree rings reconstructed changes in atmospheric carbon 14 are larger than previously thought with the largest change occurring simultaneously with the sudden climatic cooling of the younger dryas event carbon 14 and published beryllium 10 data together suggest that concurrent climate and carbon 14 changes were predominantly the result of abrupt shifts in deep ocean ventilation

tephrochronology of last termination sequences in europe a protocol for improved analytical precision and robust correlation procedures a joint scotav intimate proposal the precise sequence of events during the last termination 18 000 9000 ka 14 cy r bp and the extent to which major environmental changes were synchronous are difficult to estab lish using the radiocarbon method alone because of serious distortions of the radiocarbon time scale as well as the influences of site specific errors that can affect the materials dated attention has there fore turned to other methods that can provide independent tests of the chronology and correlation of events during the last termination with emphasis on european sequences we summarise here the potential of tephrostratigraphy and tephrochronology to fulfil this role recent advances in the detection and analysis of hidden tephra layers cryptotephra indicate that some tephras of last termination age are much more widespread in europe than appreciated hitherto and a number of new tephra deposits have also been identified there is much potential for developing an integrated tephrochronological framework for europe which can help to underpin the overall chronology of events during the last termination for that potential to be realised however there needs to be a more systematic and robust analysis of tephra layers than has been the practice in the past we pro pose a protocol for improving analytical and reporting procedures as well as the establishment of a centralised data base of the results which will provide an important geochronological tool to support a diverse range of stratigraphical studies including opportunities to reassess volcanic hazards although aimed primarily at europe the protocol proposed here is of equal relevance to other regions and periods of interest copyright 2004 john wiley sons ltd

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