revised calendar date for the taupo eruption derived by 14c wiggle matching using a new zealand kauri 14c calibration data set taupo volcano in central north island new zealand is the most frequently active and productive rhyolite volcano on earth its latest explosive activity about 1800 years ago generated the spectacu

glacial to holocene implications of the new 27000 year dust record from the epica dome c east antarctica ice core insoluble dust concentrations and volume size distributions have been measured for the new 581 m deep dome c epica ice core antarctica over the 27000 years spanned by the record microparticle measurements from 169 levels to date confirm evidence of the drastic decrease in bulk concentration from the last glacial maximum lgm to the holocene interglacial by a factor of more than 50 in absolute value and of about 26 in flux unique new features revealed by the epica profile include a higher dust concentration during the antarctic cold reversal phase acr by a factor of 2 with respect to the holocene average this event is followed by a well marked minimum that appears to be concomitant with the methane peak that marks the end of the younger dryas in the northern hemisphere particle volume size distributions show a mode close to 2 m in diameter with a slight increase from the lgm to the holocene the lgm holocene concentration ratio appears to be dependent on particle size and for diameters from 2 to 5 m it changes from 50 to 6 glacial samples are characterised by well sorted particles and very uniform distributions while the interglacial samples display a high degree of variability and dispersion this suggests that different modes of transport prevailed during the two climatic periods with easier penetration of air masses into antarctica in the holocene than during glacial times assuming that southern south america remained the main dust source for east antarctica over the time period studied the higher dust content recorded during the acr which preceded the younger dryas period represents evidence of a change in south america environmental conditions at this time a wet period and likely mild climate in south america is suggested at circa 11 5 11 7 kyr bp corresponding to the end of the younger dryas the holocene part of the profile also shows a slight general decrease in concentration but with increasingly large particles that may reflect gradual changes at the source

the anatomy of last glacial maximum climate variations in south westland new zealand derived from pollen records abstract we present pollen records from three sites in south westland new zealand that document past vegetation and inferred climate change between approximately 30 000 and 15 000 cal yr bp detailed radiocarbon dating of the enclosing sediments at one of those sites galway tarn provides a more robust chronology for the structure and timing of climate induced vegetation change than has previously been possible in this region the kawakawa oruanui tephra a key isochronous marker affords a precise stratigraphic link across all three pollen records while other tie points are provided by key pollen stratigraphic changes which appear to be synchronous across all three sites collectively the records show three episodes in which grassland interpreted as indicating mostly cold subalpine to alpine conditions was prevalent in lowland south westland separated by phases dominated by subalpine shrubs and montane lowland trees indicating milder interstadial conditions dating expressed as a bayesian estimated single best age followed in parentheses by younger older bounds of the 95 confidence modelled age range indicates that a cold stadial episode whose onset was marked by replacement of woodland by grassland occurred between 28 730 29 390 28 500 and 25 470 26 090 25 270 cal yr bp years before ad 1950 prior to the deposition of the kawakawa oruanui tephra milder interstadial conditions prevailed between 25 470 26 090 25 270 and 24 400 24 840 24 120 cal yr bp and between 22 630 22 930 22 340 and 21 980 22 210 21 580 cal yr bp separated by a return to cold stadial conditions between 24 400 and 22 630 cal yr bp a final episode of grass dominated vegetation indicating cold stadial conditions occurred from 21 980 22 210 21 580 to 18 490 18 670 17 950 cal yr bp the decline in grass pollen indicating progressive climate amelioration was well advanced by 17 370 17 730 17 110 cal yr bp indicating that the onset of the termination in south westland occurred sometime between ca 18 490 and ca 17 370 cal yr bp a similar general pattern of stadials and interstadials is seen to varying degrees of resolution but generally with lesser chronological control in many other paleoclimate proxy records from the new zealand region this highly resolved chronology of vegetation changes from southwestern new zealand contributes to the examination of past climate variations in the southwest pacific region the stadial and interstadial episodes defined by south westland pollen records represent notable climate variability during the latter part of the last glaciation similar climatic patterns recorded farther afield for example from antarctica and the southern ocean imply that climate variations during the latter part of the last glaciation and the transition to the holocene interglacial were inter regionally extensive in the southern hemisphere and thus important to understand in detail and to place into a global context

ages of 24 widespread tephras erupted since 30 000 years ago in new zealand with re evaluation of the timing and palaeoclimatic implications of the lateglacial cool episode recorded at kaipo bog abstract tephras are important for the nz intimate project because they link all three records comprising the composite inter regional stratotype developed for the new zealand climate event stratigraphy nz ces here we firstly report new calendar ages for 24 widespread marker tephras erupted since 30 000 calendar cal years ago in new zealand to help facilitate their use as chronostratigraphic dating tools for the nz ces and for other palaeoenvironmental and geological applications the selected tephras comprise 12 rhyolitic tephras from taupo nine rhyolitic tephras from okataina one peralkaline rhyolitic tephra from tuhua and one andesitic tephra each from tongariro and egmont taranaki volcanic centres age models for the tephras were obtained using three methods i 14 c based wiggle match dating of wood from trees killed by volcanic eruptions these dates published previously ii flexible depositional modelling of a high resolution 14 c dated age depth sequence at kaipo bog using two bayesian based modelling programs bacon and oxcal s p sequence function and the intcal09 data set with sh offset correction 44 17 yr and iii calibration of 14 c ages using oxcal s tau boundary function and the shcal04 and intcal09 data sets our preferred dates or calibrated ages for the 24 tephras are as follows youngest to oldest all mid point or mean ages of 95 probability ranges kaharoa ad 1314 12 taupo unit y ad 232 10 mapara unit x 2059 118 cal yr bp whakaipo unit v 2800 60 cal yr bp waimihia unit s 3401 108 cal yr bp stent unit q 4322 112 cal yr bp unit k 5111 210 cal yr bp whakatane 5526 145 cal yr bp tuhua 6577 547 cal yr bp mamaku 7940 257 cal yr bp rotoma 9423 120 cal yr bp opepe unit e 9991 160 cal yr bp poronui unit c 11 170 115 cal yr bp karapiti unit b 11 460 172 cal yr bp okupata 11 767 192 cal yr bp konini bed b 11 880 183 cal yr bp waiohau 14 009 155 cal yr bp rotorua 15 635 412 cal yr bp rerewhakaaitu 17 496 462 cal yr bp okareka 21 858 290 cal yr bp te rere 25 171 964 cal yr bp kawakawa oruanui 25 358 162 cal yr bp poihipi 28 446 670 cal yr bp and okaia 28 621 1428 cal yr bp secondly we have re dated the start and end of the lateglacial cool episode climate event nzce 3 in the nz ces previously referred to as the lateglacial climate reversal as defined at kaipo bog in eastern north island new zealand using both bacon and oxcal p sequence modelling with the intcal09 data set the ca 1200 yr long cool episode indicated by a lithostratigraphic change in the kaipo peat sequence to grey mud with lowered carbon content and a high resolution pollen derived cooling signal began 13 739 125 cal yr bp and ended 12 550 140 cal yr bp mid point ages of the 95 highest posterior density regions bacon modelling the oxcal modelling generating almost identical ages confirmed these ages the lateglacial cool episode ca 13 8 12 6 cal ka bp thus overlaps a large part of the entire antarctic cold reversal chronozone ca 14 1 12 4 cal ka bp or ca 14 6 12 8 cal ka bp and an early part of the greenland stadial 1 younger dryas chronozone ca 12 9 11 7 cal ka bp the timing of the lateglacial cool episode at kaipo is broadly consistent with the latitudinal patterns in the antarctic cold reversal signal suggested for the new zealand archipelago from marine and terrestrial records and with records from southern south america

younger dryas and early holocene age glacier advances in patagonia reliable dating of southern hemisphere glacier fluctuations since the last glacial maximum lgm is crucial to resolving debates about millennial scale climate change here we present be 10 dates f

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

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

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

a composite pollen based stratotype for inter regional evaluation of climatic events in new zealand over the past 30 000 years nz intimate project abstract our review of paleoclimate information for new zealand pertaining to the past 30 000 years has identified a general sequence of climatic events spanning the onset of cold conditions marking the final phase of the last glaciation through to the emergence to full interglacial conditions in the early holocene in order to facilitate more detailed assessments of climate variability and any leads or lags in the timing of climate changes across the region a composite stratotype is proposed for new zealand the stratotype is based on terrestrial stratigraphic records and is intended to provide a standard reference for the intercomparison and evaluation of climate proxy records we nominate a specific stratigraphic type record for each climatic event using either natural exposure or drill core stratigraphic sections type records were selected on the basis of having very good numerical age control and a clear proxy record in all cases the main proxy of the type record is subfossil pollen the type record for the period from ca 30 to ca 18 calendar kiloyears bp cal ka bp is designated in lake bed sediments from a small morainic kettle lake galway tarn in western south island the galway tarn type record spans a period of full glacial conditions last glacial coldest period lgcp within the otira glaciation and includes three cold stadials separated by two cool interstadials the type record for the emergence from glacial conditions following the termination of the last glaciation post termination amelioration is in a core of lake sediments from a maar pukaki volcanic crater in auckland northern north island and spans from ca 18 to 15 64 0 41 cal ka bp the type record for the lateglacial period is an exposure of interbedded peat and mud at montane kaipo bog eastern north island in this high resolution type record an initial mild period was succeeded at 13 74 0 13 cal ka bp by a cooler period which after 12 55 0 14 cal ka bp gave way to a progressive ascent to full interglacial conditions that were achieved by 11 88 0 18 cal ka bp although a type section is not formally designated for the holocene interglacial 11 88 0 18 cal ka bp to the present day the sedimentary record of lake maratoto on the waikato lowlands northwestern north island is identified as a prospective type section pending the integration and updating of existing stratigraphic and proxy datasets and age models the type records are interconnected by one or more dated tephra layers the ages of which are derived from bayesian depositional modelling and oxcal based calibrations using the intcal09 dataset along with the type sections and the lake maratoto record important well dated terrestrial reference records are provided for each climate event climate proxies from these reference records include pollen flora stable isotopes from speleothems beetle and chironomid fauna and glacier moraines the regional composite stratotype provides a benchmark against which to compare other records and proxies based on the composite stratotype we provide an updated climate event stratigraphic classification for the new zealand region the stratotype and event classification are not intended to act as definitive statements of paleoclimate history for the new zealand region but rather provide a firm baseline against which to compare other records including those from the marine realm

bayesian tools for tephrochronology it is suggested that bayesian statistical methods for radiocarbon data interpretation already widely used in archaeology also have potential to improve the dating of tephra layers and hence enhance their use for tephrochronology by re analysing data from a recently published paper in which the authors sought to identify the calendar date of the eruption of fourteenth century ad kaharoa tephra a key marker in new zealand prehistory it is shown that bayesian methods can be used to draw together a coherent collection of radiocarbon data undertake formal outlier detection and include prior information regardless of the calibration curve adopted the distribution of likely dates for the kaharoa eruption is multimodal by including prior information from wiggle matched dendrochronology the uncertainty on the estimate of the calendar date is reduced from a range of about 100 years to about 25 years i e 648 623 cal bp with modes at 638 and 632 cal bp using sensitivity analysis however it is shown that such estimates are affected by the quality and nature of the prior information available as a result we urge tephrochronologists to seek fastidiously both high quality radiocarbon data and reliable stratigraphic sequences that might inform future geochronological model building

major lake level fluctuations and climate changes for the past 16 000 years as reflected by diatoms and chironomids preserved in the sediment of laguna potrok aike southern patagonia abstract laguna potrok aike is a maar lake located in southernmost argentina and is one of the few permanent lakes preserving a continuous climatic record from the semiarid patagonian steppe furthermore its location close to antarctica provides a unique opportunity to compare paleoclimate from continental south america with the polar records the analysis of subfossil chironomids and diatoms throughout a 16 m sedimentary record retrieved from this lake combined with a well constrained chronology of the last ca 16 ka bp provided a high resolution paleoenvironmental reconstruction of the limnology of the lake and regional climate conditions the combination of both bioproxies showed humid conditions during the lateglacial followed by drier conditions during the holocene resulting in large variations in lake level despite not showing a clear evidence of a cold reversal similar to the antarctic cold reversal and or the younger dryas both records suggest high water levels and oligotrophic conditions between 16 4 and 11 5 cal ka bp the lake level drop that occurred at ca 8 7 ka bp is well documented by both bioproxies

paleoceanographic control on a large marine reservoir effect offshore of tokai south of japan nw pacific during the last glacial maximum deglaciation abstract knowledge of the marine reservoir effect is important in calibrating radiocarbon ages to calendar ages and in correlating geologic and paleoceanographic events among different sites including global events large explosive volcanic eruptions have yielded numerous volcanic ash layers tephras over geological time because tephra layers are deposited both on land and upon the seafloor they represent a unique and important link between the geological records of terrestrial and marine areas comparison of the radiocarbon ages of a tephra layer deposited in marine planktonic foraminifera and terrestrial peat materials reveals a local marine reservoir age 600 700 years or more during the early part of the last deglaciation off tokai south of japan this age is larger than that determined for the present day pacific coast of japan 82 years and similar to that of the present day subarctic nw pacific 350 580 years this difference between modern day and deglaciation marine reservoir values is thought to reflect the contrasting properties of surface water masses between the two periods

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

a review of the australian new zealand sector of the southern ocean over the last 30ka aus intimate project the australia new zealand region of the southern ocean is influenced by several of the major global water masses of the oceans and is the prime entry point for cold deep waters into the pacific basin during the last glacial there was increased sea ice extent around antarctica as far north as 55 s as well as increased iceberg presence inferred from ice rafted debris evidence from microfossil assemblages suggests that sea surface temperatures sst were up to 7 c cooler consistent with recent estimates of cooling for new zealand derived from glacier modelling and other terrestrial proxies the subtropical front stf subantarctic front saf and polar front pf had migrated north except where the position of the fronts were controlled bathymetrically despite the potential for iron fertilisation by increased dust input into the ocean during the glacial there is limited evidence for higher total biological productivity in the pacific sector of the southern ocean the altered oceanic circulation during the glacial also decreased nutrients in the surface waters and affected the outgassing of co 2 this contributed to an increased storage of co 2 in the deep waters and lowering of the carbonate lysocline during the deglaciation sea ice retreat and sst increased rapidly at 18 ka roughly synchronous with the reinvigoration of deep water circulation in the southern ocean and the release of co 2 stored in the deep waters the gradient in carbon isotopes 13 o benthic between antarctic intermediate water aaiw and lower circumpolar deep water lcdw was greatest at the start of the deglaciation suggesting that the aaiw ventilation preceded lcdw ventilation or there was a significant change in air sea fractionation of 13 o benthic there was a slight enrichment in 18 o planktic decrease in ssts and a reduction in intermediate and deep water circulation between 14 and 12 5 ka bp during the antarctic cold reversal acr coincident with glacier advances in the new zealand southern alps and other terrestrial records of cooling following the acr there was a second more minor release of deep water co 2 most likely related to reinvigoration of north atlantic deep water nadw from 10 ka onwards the modern intermediate and deep water circulation was established air temperatures and ssts reached a maximum in the early holocene with the stf located at its most southerly position and there was a widespread retreat of antarctic ice sheets to their modern position a decline to modern sst and air temperatures in the mid to late holocene followed while millennial cycles overprinted on the sst and 18 o planktic records may be the result of subtle changes in the position and strength of the westerly winds during the holocene

the 8 2 ka event calendar dated glacier response in the alps evidence for an 8 2 ka event related advance for an alpine glacier was missing for a long time in the light of dendrochronological analyses for tree remains found in front of the mont mine glacier swiss alps we present evidence for such an advance related to the 8 2 ka event calendar dates established for dozens of tree remains place this glacier advance 8175 yr before a d 2000 therefore this 8 2 ka advance response of the mont mine glacier terminated a nearly millennial long retreat period with a glacier always shorter than today

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

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

changes in north atlantic radiocarbon reservoir ages during the allerod and younger dryas estimates of the radiocarbon age of seawater are required in correlations between marine and terrestrial records of the late quaternary climate we radiocarbon dated marine shells and terrestrial plant remains deposited in two bays on norway s west coast between 11 000 and 14 000 years ago a time of large and abrupt climatic changes that included the younger dryas yd cold episode the radiocarbon age difference between the shells and the plants showed that sea surface reservoir ages increased from 400 to 600 years in the early yd stabilized for 900 years and dropped by 300 years within a century across the yd holocene transition

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

palaeocirculation across new zealand during the last glacial maximum at 21 ka abstract what circulation pattern drove southern alps glacial advances at 21 ka late 20th century glacial advances in new zealand are commonly attributed to a dual precipitation increase and cooler than normal temperatures associated with enhanced westerly flow that occur under synoptic pressure patterns termed zonal regimes kidson 2000 but was the circulation pattern that supported major southern alps glacial advances during the global lgm similar to the modern analog here a regional climate regime classification rcrc time slice was used to infer past circulation for new zealand during the lgm at 21 ka palaeoclimate information that supported the construction of the 21 ka time slice was derived from the nz intimate climate event stratigraphy ces one new auckland maar proxy record and additional low resolution data sourced from the literature the terrestrial evidence at 21 ka implicates several possibilities for past circulation depending on how interpretations for some proxies are made the interpretation considered most tenable for the lgm based on the agreement between terrestrial evidence marine reconstructions and palaeoclimate model results is an anticyclonic zonal circulation regime characterized by increased influences from blocking highs over the south island during winter and an increase in zonal and trough synoptic types with southerly to westerly quarter wind flow during summer these seasonal circulation traits would have generated lower mean annual temperatures cooler than normal summer temperatures and overall lower mean annual precipitation for new zealand particularly in the western south island at 21 ka the anticyclonic zonal time slice reconstruction presented in this study has different spatial traits than the late 20th century and the early little ice age signatures suggesting more than one type of regional circulation pattern can drive southern alps glacial activity this finding lends support to the hypothesis that temperature over precipitation change is more important as the primary modulator of southern alps ice advances the rcrc approach also demonstrates some subtle advantages of integrating multi proxy data within a palaeocirculation context for new zealand notably because this reconstruction technique enables direct comparisons to coarsely resolved palaeoclimate model outputs that do not have downscaled information

re anchoring the late pleistocene tephrochronology of new zealand based on concordant radiocarbon ages and combined 238u 230th disequilibrium and u th he zircon ages abstract the caldera forming rotoiti eruption from okataina volcano was one of the largest rhyolite events of the last 100 ka in the taupo volcanic zone new zealand its associated widespread tephra layer rotoehu tephra is a significant time marker in terrestrial marine paleoclimate correlation studies in the sw pacific however the accurate and precise age of this eruption and of the subsequent smaller volume earthquake flat eqf eruption has been the subject of controversy despite numerous studies we have applied combined 238u 230th disequilibrium and u th he dating of zircon from rotoiti and eqf deposits and obtained overlapping ages of 45 1 7 3 3 ka and 45 1 6 2 9 ka respectively these results are supported by new and published high precision radiocarbon data bracketing the age of the rotoiti eruption between 44 8 0 3 and 47 5 2 1 ka cal bp these age data are also in good agreement with a range of previously published estimates based on paleoclimate palynology luminescence dating of enclosing sediment and sedimentation rates in terrestrial and marine settings however these results are at variance with a commonly quoted age of 60 ka largely constrained by a single 40ar 39ar age of an overlying glassy lava flow at a distal tephra site this study demonstrates the potential for combined 238u 230th disequilibrium and u th he dating of zircon in tephra and other volcanic deposits to provide age control in the 40 100 ka time interval a period difficult to constrain using more traditional radiocarbon k ar and 40ar 39ar methods

relations between postglacial fluvial incision rates and uplift rates in the north island new zealand 1 fluvial incision rates are increasingly being used as a proxy for rock uplift rates for inland settings we test the validity of this approach by comparing incision rates and rock uplift rates along the hikurangi margin new zealand postglacial fluvial incision rates were calculated by measuring the difference in altitude between the last glacial maximum lgm terrace tread 18 2 calendar ka and the present river bed for 10 major rivers catchment areas 1400 5900 km2 incision rates have thus been measured over a half glacial cycle they also represent average rates over the last 18 kyr during which time variations are likely due to processes such as knickpoint retreat rock uplift rates have been estimated from 1 altitude differences between the treads of pairs of fluvial fill terraces 55 and 18 calendar ka assumed to have formed at the same altitude i e rock uplift relative to the geoid 2 present day altitudes of late neogene paleoshoreline marker horizons 1 6 5 7 ma i e rock uplift relative to sea level and 3 present day altitudes of neogene mudstones for which maximum depth of burial has been calculated from porosity i e rock uplift relative to sea level these rock uplift rates overestimate tectonic uplift rates because they do not take into account isostatic compensation due to erosion mean incision rates range up to 11 7 mm yr 1 and mean rock uplift rates range up to 4 1 and 0 9 mm yr 1 for the three methods respectively we have made some qualitative and semiquantitative observations about nontectonic controls on postglacial incision rates and find that localized influence only is exerted by rainfall base level and bedrock lithology while negative or no correlations are shown with lgm fluvial fill thickness and stream power incision rates and uplift rates display a rough correlation with incision rates typically 1 5 5 times uplift rates this relation suggests that tectonic uplift is likely to exert an important control on fluvial incision in the hikurangi margin

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

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

correlation of late quaternary moraines impact of climate variability glacier response and chronological resolution abstract the last decade has seen a global surge in the number and resolution of well dated geomorphological reconstructions of mountain glacier fluctuations and former ice sheet extents this has been facilitated by the widespread deployment of large samples of terrestrial cosmogenic nuclide dating tcnd allowing more sophisticated probability analyses for reducing the statistical uncertainty of moraine ages and testing of correlations at local regional and hemispheric scales geochronological advances in the field laboratory and on model calibration have taken place in parallel with modelling of palaeoclimate based on glacier reconstructions and of glacier sensitivity to temperature and precipitation forcing in spite of these advances basic conceptual issues remain this review questions whether the technical leap forward in dating has encouraged us to over reach our interpretive limits particularly in terms of the concept and practice of correlation we propose that to enable reliable correlation glacier chronologies should first be examined for their climatic integrity spatial coherence and chronological robustness even with excellent dating interpretive complexity remains due to complex climate signals and glacier response characteristics and to erosion censoring of the landform record all are issues which must be addressed to avoid either spurious lumping correlation or splitting differentiation of glacier chronologies and thus misinterpretation of the climatic significance of reconstructed glacier advances we suggest that the reliability of correlation is no better than the weakest link in the chain of reasoning which connects climatic fluctuations with dated landforms and sediments improved dating means that poor chronological resolution is less likely to be the limiting factor for correlation but shifts the focus onto other less quantifiable sources of uncertainty these conceptual statements are exemplified with reference to holocene glacial chronologies of contrasting mid latitude environments in southern norway iceland and new zealand

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

rapid change in early holocene environments inferred from lake pupuke auckland city new zealand sediment cores from lake pupuke in auckland city new zealand contain a high resolution millennial to centennial scale record of changing climate and catchment hydrology spanning the past ca 10 000 years here we focus on the period between 9500 25 and 7000 155 cal yr bp during which grain size diatom palaeoecology biogenic silica concentrations sediment elemental and carbon isotope geochemistry reflect changes in sediment sources and lake conditions with a significant event commencing at ca 8240 cal yr bp commensurate with a lowering of lake level faster erosion rates and increased sediment influx with a duration of ca 360 yrs however the changes in the lake are not reflected in the terrestrial vegetation where the pollen record indicates that podocarp forest dominated the auckland region with apparent environmental stability during this part of the early holocene the synchronous change in most of the proxies between ca 8240 and 7880 cal yr bp at lake pupuke indicates the presence of a sustained episode of relatively low lake level and concomitant increased rate of erosion in the early holocene that appears to be at least partly coeval with the 8200 cal yr bp meltwater event proposed for the north atlantic region copyright 2008 john wiley sons ltd

last glacial maximum climate in new zealand inferred from a modelled southern alps icefield abstract we present a simulation of the new zealand southern alps icefield at the last glacial maximum lgm c 30 000 20 000 calendar years ago ka in an attempt to constrain the climate of that period we use a 500 m resolution ice sheet model parameterised using empirical glaciological climatological and geological data specific to the model domain to simulate the entire southern alps icefield we find that an lgm cooling of at least 6 6 5 c is necessary to bring about valley glaciers that extend beyond the mountains however climate topography thresholds related to the elevation and hypsometry of individual catchments control the gradient of the rate of glacier expansion in the domain and in order to remain within geologically reconstructed lgm limits we find that the lgm cooling was most likely associated with a precipitation regime up to 25 drier than today wetter than present scenarios give rise to equilibrium line depressions and ice extents that are incompatible with empirical evidence these results perhaps indicate that either the westerly air masses affecting new zealand during the lgm were drier than today or that they were weaker or zonally displaced with respect to present

redating the advance of the new zealand franz josef glacier during the last termination evidence for asynchronous climate change abstract dating climatic and environmental records with accuracy and precision is critical if we are to robustly test hypotheses of synchronous change between the hemispheres in the southern hemisphere the advance of the new zealand franz josef glacier to the waiho loop terminal moraine has been used as evidence of synchronous global change during the younger dryas chronozone however radiocarbon ages for wood incorporated into the sediments associated with the advance span an interval of 900 years here we demonstrate that weathered old wood was incorporated into the deposit prior to or during the advance and that this material is highly susceptible to contamination by young carbon resulting in the wide range of age estimates reported previously we have identified material with little evidence of reworking well preserved wood with bark attached that provides a statistically robust mean radiocarbon age of 11 062 30 bp 13 1 ka for the advance of the franz josef glacier the timing of this event falls within the later part of the antarctic cold reversal comparison with local regional and global records suggests that cold conditions in the southern ocean were probably experienced in new zealand at this time driving the glacial advance

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

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

radiaxial calcite in lower miocene strata subsurface enewetak atoll abstract radiaxial calcite is abundant in lower miocene strata 377 819 m deep on enewetak atoll these radiaxial crystals have equant bladed and fibrous morphologies and occur as isopachous crusts 0 05 2 0 mm thick radiaxial terminations consist of fibrous subcrystals bundled together into larger acute obtuse or rounded shapes enewetak radiaxial calcite ranges from clear to very inclusion rich most inclusions are microcavities caused by organic infestations videtich 1985 alternating bands of inclusion rich and inclusion poor calcite mimic existing termination patterns radiaxial calcites fill intergranular pores sponge borings fractures and aragonite molds aragonite has been pervasively dissolved from the lower miocene strata containing radiaxial calcite banded radiaxial calcit can be traced from intergranular pores into aragonite molds radiaxial calcites have a mean magnesium concentration of 3 2 mole mgco3 with a range from 1 6 to 11 1 mole mgco3 inclusion rich bands and more deeply buried radiaxial calcite tend to have lower magnesium concentrations enewetak radiaxial calcite has 13c values of 1 3 to 2 5 pdb and 18o values of 1 8 to 0 4 pdb petrographic and stable isotopic data are consistent with precipitation of radiaxial calcite in its present form directly from seawater precipitation of radiaxial calcite after aragonite dissolution indicates precipitation distinctly after deposition probably in a burial environment dissolution of aragonite by deep marine water is suggested by 1 abundant marine cement associated with aragonite dissolution 2 a lack of meteoric cements associated with aragonite dissolution and 3 no evidence of subaerial exposure in lower miocene strata between 400 and 819 m modern pacific ocean water is undersaturated with respect to aragonite at depths where aragonite dissolution is observed 375 850 m tidal fluctuations and temperature profiles indicate that lower miocene strata containing radiaxial calcite are in open communication with modern pacific ocean water therefore aragonite dissolution and radiaxial cementation are interpreted as having occurred in seawater undersaturated with respect to aragonite circulating through the atoll variations in magnesium concentration in enewetak radiaxial calcite may be the result of original heterogeneity or differential loss of magnesium during later diagenesis in seawater the first alternative is preferred precipitation of radiaxial calcite at different rates at different degrees of saturation could cause variable magnesium concentrations more deeply buried radiaxial calcite may have precipitated more slowly in deeper less supersaturated water resulting in lower magnesium concentrations likewise slower rates of precipitation may have resultedin organic infestations and lower magnesium concentrations in inclusion rich bands enewetak radiaxial calcites suggest that two factors might be critical to development of radiaxial fabric 1 precipitation at fluctuati g rates and 2 formation in waters undersaturated with respect to aragonite

osl based lateral progradation and aeolian sediment accumulation rates for the apalachicola barrier island complex north gulf of mexico florida article i nfo vertical sediment cores in five separate beach ridge complexes along the north east gulf of mexico coast were recovered and dated using optically stimulated luminescence osl dating of quartz these are located on cape san blas csb little st george island lsgi richardson s hammock rh st joseph peninsula sjp and saint vincent island svi all of these landforms are coastal barrier systems situated along a 100 km stretch of the florida panhandle u s a two samples were collected for dating from each core ridge accumulation rates rar associated with lateral progradation were calculated from the dated samples we also determined average sediment accumulation rates asar for two intervals within each sediment core all osl ages within the sediment cores were found to be in stratigraphic order or in a few cases statistically indistinguishable moreover all dated ridges were found to be in correct temporal sequence based on their geomorphic positions rapidly accreted sequences were found to be backed by st joseph bay in the western region of the study area more slowly accreted sequences were associated with the more eastern stretches of the study area backed by st vincent sound and apalachicola bay our asar results are in accord with an australian study of modern dune accumulation perhaps our most important finding is that in the barrier island environments of this north eastern gulf coast region aeolian sedimentation continues well after full vegetative cover develops and stranding of landward ridges takes place this confirms our similar earlier observation on svi lopez and rink 2008 we find that up to approximately one order of magnitude lower sedimentation rates occur after an initial period of more rapid aeolian accumulation for the vertical intervals studied in foredune ridges lateral progradation rates of ridge sequences were highly variable within the study area ranging from 92 to 848 m 100 years but we did find agreement between some of our slower ridge accumulation rates and those in other areas of florida and around the world determined using osl and 14 c dating we conclude that osl may be used in a regional context to establish variation in progradation rates and aeolian accumulation that varies among systems

the last glacial maximum lgm in western south island new zealand implications for the global lgm and mis 2 abstract the morainic and outwash deposits of the larrikins la and moana mn formations in north westland are correlated with the m5 t5 and m6 t6 deposits in south westland the la m5 deposits resulted from two separate otira glaciation glacial advances la 1 m5 1 la 2 m5 2 of essentially similar extents pollen sequences in peats and coverbeds extending from before to after the kawakawa tephra 26 500 cal yr bp indicate an extensive period of cold with a slight amelioration beginning shortly before tephra deposition this amelioration which is supported by interpretation of coverbed sequences in south westland separates the la 1 m5 1 and la 2 m5 2 advances the three westland glacial advances la 1 m5 1 la 2 m5 2 and mn m6 culminated at ca 28 000 21 500 and 19 000 cal yr bp the last being followed by major rapid glacier retreat pollen and caco 3 records from dsdp 594 east of the south island reflect contemporary glacier fluctuations on the east side of the southern alps they show the last major cold period as lasting from ca 34 000 to ca 16 000 years ago a period starting before the culmination of the la 1 m5 1 advance and ending later than the beginning of glacier retreat from the mn m6 advance the period from the la 1 m5 1 culmination to the mn m6 culmination represents the lgm in new zealand a slightly longer lgm is recorded in chile and a long lgm may also be indicated in australia a long lgm in the southern hemisphere is supported by the global sea level curve and by the regional antarctic temperature criteria of the vostok ice core these different records indicate a southern hemisphere lgm beginning at least as early as 27 000 years ago much earlier than the ocean last isotope maximum lim from 21 500 to 18 000 years ago the beginning of mis 2 defined primarily from deep sea benthic 18 o at 24 000 years is well after the beginning of ice advances leading to the southern hemisphere lgm a review of global land and ocean correlations is desirable

a revised age for the kawakawa oruanui tephra a key marker for the last glacial maximum in new zealand abstract the kawakawa oruanui tephra kot is a key chronostratigraphic marker in terrestrial and marine deposits of the new zealand nz sector of the southwest pacific erupted early during the last glacial maximum lgm the wide distribution of the kot enables inter regional alignment of proxy records and facilitates comparison between nz climatic variations and those from well dated records elsewhere we present 22 new radiocarbon ages for the kot from sites and materials considered optimal for dating and apply bayesian statistical methods via oxcal4 1 7 that incorporate stratigraphic information to develop a new age probability model for kot the revised calibrated age 2 standard deviations for the eruption of the kot is 25 360 160 cal yr bp the age revision provides a basis for refining marine reservoir ages for the lgm in the southwest pacific

reconstructing the largest explosive eruptions of mt ruapehu new zealand lithostratigraphic tools to understand subplinian plinian eruptions at andesitic volcanoes we analysed the tephra record of mt ruapehu for the period 27 097 957 to 10 000 cal years bp to determine the largest scale explosive eruptions expected from the most active new zealand andesitic volcano from the lithostratigraphic analysis a systematic change in the explosive behaviour is identified from older deposits suggesting dry magmatic eruptions and steady eruptive columns characterised by frothy to expanded pumice fabrics to younger deposits that are products of unsteady conditions and collapsing columns characterised by microvesicular fibrous and colour banded pumice fabrics the end members were separated by eruptions with steady columns linked to water magma interaction and highly unstable conduit walls dry magmatic eruptions producing steady plinian columns were most common between 27 097 957 and shortly after 13 635 165 cal years bp following this time activity continued with eruptions that produced dominantly oscillating unsteady columns which engendered pyroclastic density currents until 10 ka when there was an abrupt transition at mt ruapehu since which eruptions have been an order of magnitude lower in intensity and volume these data demonstrate long period transitions in eruption behaviour at an andesitic stratovolcano which is critical to understand if realistic time variable hazard forecasts are to be developed

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

antarctic ice sheet melting provides negative feedbacks on future climate warming we show by using a three dimensional climate model which includes a comprehensive representation of polar ice sheets that on centennial to millennial time scales antarctic ice sheet ais can melt and moderate warming in the southern hemisphere by up to 10 degrees c regionally in a 4 x co2 scenario this behaviour stems from the formation of a cold halocline in the southern ocean which limits sea ice cover retreat under global warming and increases surface albedo reducing local surface warming furthermore we show that ais melting by decreasing antarctic bottom water formation restrains the weakening of the atlantic meridional overturning circulation which is a new illustration of the effect of the bi polar oceanic seesaw consequently it appears that ais melting strongly interacts with climate and ocean circulation globally it is therefore necessary to account for this coupling in future climate and sea level rise scenarios

comment on absence of cooling in new zealand and the adjacent ocean during the younger dryas chronozone barrows et al reports 5 october 2007 p 86 presented cosmogenic exposure dates and data from an ocean sediment core that challenge evidence for glacier advance in new zealand during the younger dryas event we use modeling of geomorphic processes to argue that their cosmogenic exposure dates are inconclusive

evaluation of lateglacial temperatures in the southern alps of new zealand based on glacier modelling at irishman stream ben ohau range abstract climate proxy records from the middle to high latitude southern hemisphere indicate that a lateglacial 15 000 11 500 years ago climate reversal approximately coeval with the antarctic cold reversal acr interrupted a warming trend during deglaciation in new zealand some palaeoclimate proxy records indicate a cool episode during the acr ca 14 500 12 500 years ago while others do not express a significant change in climate recently published moraine maps and ages present an opportunity to improve the palaeoclimate interpretation through numerical modelling of glaciers we use a coupled energy balance and ice flow model to quantify palaeoclimate from past glacier extent constrained by mapped and dated moraines in the headwaters of irishman stream a high elevation catchment in the southern alps first a suite of steady state model runs is used to identify the temperature and precipitation forcing required to fit the modelled glacier to well dated lateglacial moraine crests second time dependent glacier simulations forced by a nearby proxy temperature record derived from chironomids are used to assess the fit with the glacial geomorphic record steady state experiments using an optimal parameter set demonstrate that the conditions under which the 13 000 year old moraine formed were 2 3 3 2 c colder than present with the range in temperature corresponding to a 20 variance in precipitation relative to the present day this reconstructed climate change relative to the present day corresponds to an equilibrium line altitude of ca 2000 40 m above sea level asl which is ca 400 m lower than present time dependent simulations of glacier length produce ice advance to within 100 m of the 13 000 year old terminal moraine indicating that the chironomid based temperature forcing and moraine record provide consistent information about past climate our results together with other climate proxy reconstructions from pollen records and marine sediment cores support the notion that temperatures during the acr in new zealand were 2 3 c cooler than today

synchronisation of palaeoenvironmental events in the north atlantic region during the last termination a revised protocol recommended by the intimate group abstract the north atlantic intimate group of the inqua palaeoclimate commission has previously recommended an event stratigraphy approach for the synchronisation of records of the last termination using the greenland grip isotopic record as the regional stratotype and intcal98 for the calibration of radiocarbon dates lowe j j hoek w intimate group 2001 inter regional correlation of palaeoclimatic records for the last glacial interglacial transition a protocol for improved precision recommended by the intimate project group quaternary science reviews 20 1175 1187 here we present a revised protocol for time stratigraphic correlation in the north atlantic region over a more extended time period 30 8 ka this employs the new ngrip isotopic record and associated greenland ice core chronology 2005 gicc05 as the regional stratotype intcal04 for the calibration of radiocarbon dates bayesian based statistical procedures for the construction of age models and tephrochronology to validate correlations between regional site records

stratigraphy chronology styles and dynamics of late quaternary eruptions from taupo volcano new zealand taupo volcano is the southerly of two dormant caldera volcanoes in the rhyolite dominated central portion of the taupo volcanic zone in the north island of new zealand taupo has an average magma output rate of 0 2 m 3 s 1 over the past 65 000 years and is one of the most frequently active and productive rhyolite volcanoes known the structure of the modern inverse volcano was formed largely by caldera collapse associated with the voluminous 22 600 14 c years bp oruanui eruption and has been little modified since except for collapse following the 1850 14 c years bp eruption the products of 28 eruptions labelled psi omega a ldots z all of which post date the oruanui eruption are defined and described here twenty seven of these eruptions are represented by pyroclastic deposits of which three were accompanied by a mappable lava extrusion and one eruption z solely by evidence for a lava extrusion the deposits of seven eruptions b c e s v x and y largely correspond to previously defined tephra formations karapiti poronui opepe waimihia whakaipo mapara and taupo respectively the previously defined motutere and hinemaiaia tephras are reinterpreted to represent the products of 12 eruptions g to r while the remaining eight deposits and one eruption are newly recognized eruption psi occurred at ca 17 200 14 c or 20 500 calibrated years bp and eruption z about 1740 calibrated years bp eruption volumes vary by more than three orders of magnitude between 0 01 and more than 44 km 3 and repose periods by more than two orders of magnitude from ca 20 to 6000 years the eruption deposits reflect great variations in parameters such as volume the dispersal characteristics of the fall deposits the presence or absence of intraeruptive time breaks the formation of pyroclastic flows the degree of magma water interaction the vesiculation state of the magma on fragmentation and the relative proportions of juvenile obsidian versus foreign lithologies in the lithic fractions all but seven fall deposits are plinian in dispersal two y1 and probably w are sub plinian one y5 has been termed ultraplinian while psi and a are too poorly preserved for their dispersal to be assessed the lengths of repose periods in the post oruanui sequence range are not randomly distributed but show self similar properties fractal dimensionality repose intervals r in years of not more than 350 years follow n 53 5r 0 21 and those of not less than 350 years follow n 2096r 0 83 where n is the number of eruptions the shorter repose periods may reflect triggering processes such as regional extension affecting magma bodies during their viable lifetimes while longer repose intervals i e not less than 350 years may reflect an episodicity of major rifting events or the production of magma bodies below the volcano bulk volumes v in km 3 of the eruption products also show self similar properties fractal dimensionality with n 6 17v 0 46 however there are then apparently random relationships between eruption volumes and the preceding or succeeding repose period such that prediction of the time and size of the next eruption is impossible the post oruanui activity at taupo represents noise superimposed on the more uniform longer term activity in the central taupo volcanic zone where large greater than 100 km 3 eruptions such as the oruanui occur at more evenly spaced intervals of one per 40 60 000 years

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

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

deglacial changes of the southern margin of the southern westerly winds revealed by terrestrial records from sw patagonia 52 s much of the ongoing discussion regarding synchrony or bipolar asynchrony of paleoclimate events has centered on the timing and structure of the last glacial termination in the southern mid latitudes in particular the southwestern patagonian region 50 e55 s its location adjacent to the drake passage and near the southern margin of the southern westerly winds sww allows examining the postulated links between the southern oceanesww coupled system and atmospheric co2 variations through the last glacial termination results from two sites located in the ultima esperanza area 52

black shale deposition on the northwest african shelf during the cenomanian turonian oceanic anoxic event climate coupling and global organic carbon burial high resolution geochemical records from a depth transect through the cenomanian turonian c t tarfaya basin northwest african shelf reveal high amplitude fluctuations in accumulation rates of organic carbon oc redox sensitive and sulphide forming trace metals and biomarkers indicative of photic zone euxinia these fluctuations are in general coeval and thus imply a strong relationship of oc burial and water column redox conditions the pacing and regularity of the records and the absence of a prominent continental signature suggest a dynamic depositional setting linked to orbital and higher frequency forcing determining the dominant frequency depends on the definition of the most pronounced oceanic anoxic event oae2 and its duration we propose that eccentricity is the main forcing factor at tarfaya and controlled fluctuations in wind driven upwelling of nutrient rich oxygen depleted intermediate waters from the adjacent atlantic and the periodic development of photic zone and bottom water euxinia on the mid cretaceous northwest african shelf accumulation records clearly identify the basin center as the primary site of sediment deposition with highest temporal variability and an up to six fold increase in oc burial from similar to2 g m 2 yr prior to the oae2 to similar to12 g m 2 yr during the oae2 photic zone and bottom water euxinia alternated with periods of greater oxygenation of the water column in response to climate forcing mass balance calculations imply that similar to2 of the overall global excess oc burial associated with the oae2 was deposited in the tarfaya basin an area that represented only similar to0 05 of the total global c t ocean floor in fact the lateral extent of similar black shales along the african continental margin indicates that this part of the ocean contributed significantly to the global increase in organic carbon burial during the oae2

interactions between environmental change and shallow water carbonate buildup along the northern tethyan margin and their impact on the early cretaceous carbon isotope record 1 the evolution of the early cretaceous northern tethyan carbonate platform was not only influenced by changes in sea level detrital influx and surface water temperature but also by changes in trophic levels we distinguish between phases of carbonate production dominated by oligotrophic photozoan communities and by mesotrophic and eventually colder water heterozoan communities superimposed on this bimodal trend in platform evolution were phases of platform demise for which we provide improved age control based on ammonite biostratigraphy the initial phase of these episodes of platform demise corresponds in time to episodes of oceanic anoxic events and environmental change in general on the basis of a comparison between the temporal changes in an early cretaceous ammonite calibrated d 13 c record from southeastern france and coeval changes in the platform record we suggest that the history of carbon fractionation along the northern tethyan margin was not only influenced by changes in the oceanic carbon cycle such as in the rate of production and preservation of organic and carbonate carbon and in the size of the oceanic dissolved inorganic carbon reservoir but it was also influenced by the above mentioned changes in the ecology and geometry of the adjacent carbonate platform phases of photozoan carbonate production induced positive trends in the hemipelagic carbonate d 13 c record phases of heterozoan carbonate production pushed the d 13 c system toward more negative values platform drowning episodes implied an initial increase in d 13 c values followed by a longerterm decrease in d 13 c values

a continuous 5300 yr holocene cryptotephrostratigraphic record from northern new zealand and implications for tephrochronology and volcanic hazard assessment a continuous 5280 calendar cal yr long cryptotephrostratigraphic record of a peat core from northern new zealand demonstrates that cryptotephra studies can enhance conventional tephra records by extending the known distribution of ash fall and enabling re assessment of volcanic hazards a systematic sampling strategy was used to locate peaks in glass shard concentrations and to determine loci of individual geochemical populations and a palynological method involving spiking samples with lycopodium spores was adapted to facilitate accurate counting of glass shard concentrations using glass shard major element compositions and a core chronology based on eight ams 14c ages and two visible macroscopic tephra layers taupo tephra unit y 1688 1748 cal bp and tuhua tephra 6800 7230 cal bp 2cr age ranges four cryptotephras were correlated with known eruptions whakaipo unit v 2743 2782 cal bp stent unit q 4240 4510 cal bp and unit k 4970 5290 cal bp erupted from taupo volcanic ce

the 26 5 ka oruanui eruption new zealand an introduction and overview abstract the 26 5 ka oruanui eruption from taupo volcano in the central north island of new zealand is the largest known wet eruption generating 430 km3 of fall deposits 320 km3 of pyroclastic density current pdc deposits mostly ignimbrite and 420 km3 of primary intracaldera material equivalent to 530 km3 of magma erupted magma is 99 rhyolite and 90 pdc deposits range from mm to cm thick ultra thin veneers enclosed within fall material to 200 m thick ignimbrite in proximal areas the farthest travelled 90 km most energetic pdcs velocities 100 m s 1 occurred during phase 8 but the most voluminous pdc deposits were emplaced during phase 10 grain size variations in the pdc deposits are complex with changes seen vertically in thick proximal accumulations being greater than those seen laterally from near source to most distal deposits modern lake taupo partly infills the caldera generated during this eruption a 140 km2 structural collapse area is concealed beneath the lake while the lake outline reflects coeval peripheral and volcano tectonic collapse early eruption phases saw shifting vent positions development of the caldera to its maximum extent indicated by lithic lag breccias occurred during phase 10 the oruanui eruption shows many unusual features its episodic nature wide range of depositional conditions in fall deposits of very wide dispersal and complex interplay of fall and pdc activity

climate induced changes as registered in inorganic and organic sediment components from laguna potrok aike argentina during the past 51 ka total organic carbon total inorganic carbon biogenic silica content and total organic carbon total nitrogen ratios of the laguna potrok aike lacustrine sediment record are used to reconstruct the

integrating the intimate records using tephrochronology rising to the challenge little has challenged our understanding of climate change more so than the abruptness with which large scale shifts in temperature occurred during the late quaternary the causal mechanisms driving

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

glacier advance in southern middle latitudes during the antarctic cold reversal the geographic extent of cooling associated with the antarctic cold reversal is unclear dating of glacial moraines in new zealand suggests that the cooling extended into the southern mid latitudes possibly as a result of the northward migration of the southern subtropical front

un predictability in rip channel systems 1 predicting the development of rip channel systems on beaches is relevant for beach safety nearshore mixing and dispersion and has been puzzling researchers for decades field observations and computer simulations have focused on predicting the spacing and growth time of rip channels as a function of wave characteristics a satisfactory predictor of rip channel spacing and growth time has not yet been proposed here we show that the lack of predictability of rip channels is an inherent property of the system related to the high sensitivity to the bathymetry prior to pattern development sensitivity to the initial cross shore profile appears to be as important as sensitivity to wave height although we might be able to predict rip channel characteristics the information required by such predictors will need to account for the underlying bathymetry implications arising from this study are that other geomorphic patterns could display similar sensitivity

deposition models for chronological records abstract long term sedimentary sequences provide a wealth of useful information for research into the palaeo environment especially in relation to past climate change shorter records provide similar information in many archaeological contexts however if such records are to be used to provide precise timing of events and more critically the relative timing between different records methods are needed to provide accurate and precise age depth models for these sequences given the imprecision of individual calibrated radiocarbon determinations it is necessary to use the information we have about the deposition process to refine our chronologies and also to provide interpolation between dated levels in any sequence even with layer counted chronologies the uncertainties are sometimes hard to quantify this paper outlines a range of bayesian models for deposition which have been implemented in the computer programme oxcal these models can be used to combine information from the sediments themselves with radiocarbon or other direct dating information such models have the potential to integrate information between different records and provide a coherent chronology on which to base environmental or archaeological research