persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

long term sea surface temperature and climate change in the australian new zealand region 1 we compile and compare data for the last 150 000 years from four deep sea cores in the midlatitude zone of the southern hemisphere we recalculate sea surface temperature estimates derived from foraminifera and compare these with estimates derived from alkenones and magnesium calcium ratios in foraminiferal carbonate and with accompanying sedimentological and pollen records on a common absolute timescale using a stack of the highest resolution records we find that first order climate change occurs in concert with changes in insolation in the northern hemisphere glacier extent and inferred vegetation changes in australia and new zealand vary in tandem with sea surface temperatures signifying close links between oceanic and terrestrial temperature in the southern ocean rapid temperature change of the order of 6 c occurs within a few centuries and appears to have played an important role in midlatitude climate change sea surface temperature changes over longer periods closely match proxy temperature records from antarctic ice cores warm events correlate with antarctic events a1 a4 and appear to occur just before dansgaard oeschger events 8 12 14 and 17 in greenland

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

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

holocene optimum events inferred from subglacial sediments at tschierva glacier eastern swiss alps abstract this study investigates the subglacial sedimentary archive at tschierva glacier eastern swiss alps subfossil wood remains found at the retreating glacier tongue indicate that their emergence results from recent transport from an upvalley basin a confluence basin like structure was found to exist by georadar measurements underneath the present glacier in combination with high resolution age determinations based on dendrochronology and radiocarbon dating it is implied that a retreated tschierva glacier allowed vegetation growth and sediment accumulation in that basin three periods of glacier recession were detected which occurred around 9200 cal yr bp from 7450 to 6650 cal yr bp and from 6200 to 5650 cal yr bp these periods are called holocene optimum events hoe accordingly an equilibrium line rise 220 m compared to the reference period from 1960 to 1985 was inferred from digital elevation models of former glacier extents since glacier mass balance depends on summer june july august temperature and precipitation an equilibrium line altitude ela rise of 220 m implies a summer temperature increase of about 1 8 c assuming unchanged precipitation during the dated hoe alternative calculations point to probable temperature increase in a broad interval between 1 0 c taking into account a precipitation change of 250 mm a to 2 5 c with 250 mm a precipitation change supporting earlier paleotemperature estimates it is proposed that higher mean summer insolation caused a stronger seasonality during the mid holocene as compared to late holocene conditions

a review of glacial and holocene paleoclimate records from southernmost patagonia 49 55 s southern south america is the only landmass intersecting the southern westerly wind belt sww that influences the large scale oceanography and controls for example the outgassing of co2 in the southern ocean therefore paleo reconstructions from southernmost patagonia are of global interest and an increasing number of paleoclimate records have been published during the last decades we provide an overview on the different records mostly covering the holocene but partly extending into the late glacial based on a large variety of archives and proxies we particularly discuss possible reasons for regionally diverging palaeoclimatic interpretations and summarize potential climate forcing mechanisms the deglacial and holocene temperature evolution of the region including the adjacent pacific ocean indicates antarctic pattern and timing consistent with glacier re advances during the antarctic cold reversal some records indicate a significant accumulation control on the glacier fluctuations related to changes in sww strength and or position reconstructions of holocene changes in the sww behaviour provide partly inconsistent and controversially discussed pattern while records from the hyperhumid side point to a stronger or southward displaced sww core during the early holocene thermal maximum records from the lee side of the andes show either no long term trend or the opposite suggesting enhanced westerlies during the late holocene neoglacial likewise centennial scale global or hemispheric cold intervals such as the little ice age have been interpreted in terms of enhanced and reduced sww strength some sww variations can be linked to changes in the el nino southern oscillation enso consistent with instrumental climate data sets and might be ultimately forced by solar variability resolving these inconsistencies in southernmost patagonian sww records is a prerequisite for improving hemispheric comparisons and links to atmospheric co2 changes

deglaciation of coastal south western spitsbergen dated with in situ cosmogenic 10be and 14c measurements the svalbard barents ice sheet was predominantly a marine based ice sheet and reconstructing the timing and rate of its decay during the last deglaciation can inform predictions of future decay of marine based ice sheets e g west antarctica records of ice sheet change are now routinely built with cosmogenic surface exposure ages but in some regions this method is complicated by the presence of isotopic inheritance yielding artificially old and erroneous exposure ages here we present forty six 1025 be ages from bedrock n 38 and erratic boulders n 8 in southwestern spitsbergen that when paired with in situ 1427 c measurements n 5 constrain the timing of coastal deglaciation following the last glacial maximum 10be and 1428 c measurements from bedrock along a 400 m elevation transect reveal inheritance skewed 10be ages whereas 1429 c measurements constrain 400 m of ice sheet thinning and coastal deglaciation at 17 4 1 5 ka combined with three additional 10be dated coastal sites we show that the southwestern margin of the svalbard barents ice sheet retreated out of norwegian sea between 18 16 ka in situ 1432 c measurements can provide key chronological information on ice sheet response to the last termination in cases where measurements of long lived nuclides are compromised by isotopic inheritance

west antarctic ice sheet retreat driven by holocene warm water incursions glaciological and oceanographic observations coupled with numerical models show that warm circumpolar deep water cdw incursions onto the west antarctic continental shelf cause melting of the undersides of floating ice shelves because these ice shelves buttress glaciers feeding into them their ocean induced thinning is driving antarctic ice sheet retreat today here we present a multi proxy data based reconstruction of variability in cdw inflow to the amundsen sea sector the most vulnerable part of the west antarctic ice sheet during the holocene epoch from 11 7 thousand years ago to the present the chemical compositions of foraminifer shells and benthic foraminifer assemblages in marine sediments indicate that enhanced cdw upwelling controlled by the latitudinal position of the southern hemisphere westerly winds forced deglaciation of this sector from at least 10 400 years ago until 7 500 years ago when an ice shelf collapse may have caused rapid ice sheet thinning further upstream and since the 1940s these results increase confidence in the predictive capability of current ice sheet models

late holocene glacial advance and ice shelf growth in barilari bay graham land west antarctic peninsula three marine sediment cores were collected along the length of the fjord axis of barilari bay graham land west antarctic peninsula 65 55 s 64 43 w multi proxy analytical results constrained by high resolution geochronological methods 210 pb radiocarbon 137 cs in concert with historical observations capture a record of holocene paleoenvironmental variability our results suggest early and middle holocene 7022 2815 cal calibrated yr b p retreated glacial positions and seasonally open marine conditions with increased primary productivity climatic cooling increased sea ice coverage and decreased primary productivity during the neoglacial 2815 to cal 730 cal yr b p this climatic cooling culminated with glacial advance to maximum holocene positions and expansion of a fjord wide ice shelf during the little ice age lia ca 730 82 cal yr b p seasonally open marine conditions were achieved and remnant ice shelves decayed within the context of recent rapid regional warming 82 cal yr b p to present our findings agree with previously observed late holocene cooling and glacial advance across the antarctic peninsula suggesting that the lia was a regionally significant event with few disparities in timing and magnitude comparison of the lia antarctic peninsula record to the rest of the southern hemisphere demonstrates close synchronicity in the southeast pacific and southern most atlantic region but less coherence for the southwest pacific and indian oceans comparisons with the northern hemisphere demonstrate that the lia antarctic peninsula record was contemporaneous with pre lia cooling and sea ice expansion in the north atlantic arctic suggesting a global reach for these events

a cosmogenic 3he chronology of late quaternary glacier fluctuations in north island new zealand 39 s abstract mountain glaciers advance and retreat primarily in response to changes in climate establishing the timing and magnitude of mountain glacier fluctuations from geological records can thus help to identify the drivers and mechanisms of past climate change in this study we use cosmogenic 3 he surface exposure dating and tephrochronology to constrain the timing of past glaciation on tongariro massif in central north island new zealand 39 s exposure ages from moraine boulders show that valley glaciation persisted between c 30 18 ka which coincides with the global last glacial maximum reinterpretation of moraine tephrostratigraphy using major element geochemistry analysis shows that ice retreat and climatic amelioration at the last glacial termination was well underway prior to 14 ka the equilibrium line altitude in central north island during the last glacial maximum was c 1400 1550 m above sea level which is c 930 1080 m lower than present considering the uncertainties in the glacial reconstruction and temperature lapse rates we estimate that this equilibrium line altitude lowering equates to a temperature depression of 5 6 1 1 c relative to present our mapping and surface exposure dating also show evidence for an earlier period of glaciation of similar magnitude to the last glacial maximum which culminated prior to 57 ka probably during marine isotope stage 4 good agreement between the timing and magnitude of glacier fluctuations in central north island and the southern alps indicate a response to a common climatic forcing during the last glacial cycle

spatial temporal differences in climate change at different altitudes northeastern qinghai tibetan plateau during the holocene period the history of climate change and related driving mechanisms of the gonghe basin northeastern qinghai tibetan plateau china was reconstructed in the holocene epoch based on the comprehensive analysis of multi proxies consisting of magnetic susceptibility grain size and geochemical elements from eolian and peat deposits at different altitudes the results indicate that holocene climate change at different altitudes is both consistent and different a synchronous record of an increased warm humid phase 10 0 8 5 ka and a cold phase around 8 2 ka in the early holocene an optimal warm humid condition in marginal mountains of the gonghe basin in the mid holocene and a gradual decline in temperature and humidity in the late holocene the gonghe basin interior in the mid holocene was relatively arid with increased moisture in the late holocene on this basis we compared our results to the paleoclimatic record in the low latitude asian monsoonal region which indicates that in addition to the asian summer monsoonal strength having influenced regional climate change the upward and subsidence motion of airflow over the qinghai tibetan plateau induced by topographic conditions evaporation and the feedback effect by the substrate was also influential the latter was especially important for spatial temporal differences in middle and late holocene climatic changes at different altitudes

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

palaeoclimate southern westerlies and co2 the southern hemisphere westerly winds affect the exchange of carbon dioxide between the ocean and atmosphere climate reconstructions from the southern mid latitudes may reveal variability in the strength and position of the wind belt since the last glacial maximum

terrestrial and submarine evidence for the extent and timing of the last glacial maximum and the onset of deglaciation on the maritime antarctic and sub antarctic islands this paper is the maritime and sub antarctic contribution to the scientific committee for antarctic research scar past antarctic ice sheet dynamics pais community antarctic ice sheet reconstruction the overarching aim for all sectors of antarctica was to reconstruct the last glacial maximum lgm ice sheet extent and thickness and map the subsequent deglaciation in a series of 5000 year time slices however our review of the literature found surprisingly few high quality chronological constraints on changing glacier extents on these timescales in the maritime and sub antarctic sector therefore in this paper we focus on an assessment of the terrestrial and offshore evidence for the lgm ice extent establishing minimum ages for the onset of deglaciation and separating evidence of deglaciation from lgm limits from those associated with later holocene glacier fluctuations evidence included geomorphological descriptions of glacial landscapes radiocarbon dated basal peat and lake sediment deposits cosmogenic isotope ages of glacial features and molecular biological data we propose a classification of the glacial history of the maritime and sub antarctic islands based on this assembled evidence these include type i islands which accumulated little or no lgm ice type ii islands with a limited lgm ice extent but evidence of extensive earlier continental shelf glaciations type iii seamounts and volcanoes unlikely to have accumulated significant lgm ice cover type iv islands on shallow shelves with both terrestrial and submarine evidence of lgm and or earlier ice expansion type v islands north of the antarctic polar front with terrestrial evidence of lgm ice expansion and type vi islands with no data finally we review the climatological and geomorphological settings that separate the glaciological history of the islands within this classification scheme

an examination of possible relationships between paleoenvironmental conditions during the pleistocene holocene transition and human occupation of southern patagonia argentina east of the andes between 46 and 52 s abstract spatial and temporal variations in evidence for human occupation of argentinian south patagonia closely resemble changes in past vegetation reconstructed from pollen records the antarctic cold reversal was cold and dry in the deseado massif and there is little evidence of humans at this time in contrast the younger dryas interval was warmer and slightly wetter and this was when humans moved into the deseado area increasing temperatures during the early holocene brought higher precipitation to much of patagonia east of the andes except the northern deseado massif explaining the increase in evidence of human occupation in western areas and the decrease in evidence in the massif spatial and temporal variations in the frequency of radiocarbon dates indicating human presence show that in southern patagonia humans were not only influenced by the major climate shifts of the pleistocene holocene transition but possibly also by distinct short term changes lasting only a few to several centuries that are apparent in the high resolution antarctic byrd ice core water availability may have had the greatest influence on human use of the landscape rather than temperature however as temperature is crucial in controlling the latitude of the core of the southern westerly winds associated with reduced precipitation over most of eastern patagonia it is difficult to separate water from temperature in examining impacts on the first humans in southernmost south america

late glacial and early holocene cyclic changes in paleowind conditions and lake levels inferred from diatom assemblage shifts in laguna potrok aike sediments southern patagonia argentina abstract pasado is a multidisciplinary potrok aike sediment archive drilling project which was conducted from 2008 to 2013 focusing on the sedimentary record of the volcanic crater maar laguna potrok aike 52 s 70 w 116 m asl in southern patagonia argentina it represents one of the few non glacial and extra andean sediment archives studied so far on the continental landmass between subtropical south america and antarctica that covers the entire holocene and the late glacial in this study a high resolution diatom analysis of the late glacial time interval situated between 15 60 and 10 51 ka cal bp was performed on the pasado sediment core this period is of particular interest as it encompasses the antarctic cold reversal acr as well as the younger dryas yd chronozone to better refine the variability of environmental and climatic conditions of this late glacial time interval we combined our data with those of a microsedimentological analysis conducted on the same sediments and for the same period to infer changes in lake level and water column stratification our study revealed that diatoms are an ideal proxy to complement microsedimentological analyses by providing important independent information on the past limnological dynamics of laguna potrok aike and the paleoclimatic conditions that prevailed during the late glacial in the study area and allows a new way of explaining shifts in the position of southern hemisphere westerly winds sww during the late glacial peaks of planktonic diatoms particularly cyclostephanos patagonicus correspond to previously detected total organic carbon toc ca si ca and mn peaks and support the hypothesis that relatively high lake levels and weaker sww have prevailed during the late glacial moreover a cyclic pattern observed both in the biological and geochemical indicators suggests at least five shifts in the position of the sww from the beginning of the acr to the end of the yd the periodicity of these shifts seems to be related to antarctic ice sheet discharge aid events in the scotia sea that coincide with enhanced iceberg flux from the antarctic ice sheet

late palaeozoic global changes affecting high latitude environments and biotas an introduction abstract the late palaeozoic ice age lpia spanning approximately from 320 ma serpukhovian late mississippian to 290 ma mid sakmarian early permian represents the vegetated earth s largest and most long lasting regime of severe and multiple glaciations involving processes and patterns probably comparable to those of the last ice age accompanying the lpia occurred a number of broadly synchronous global environmental and biotic changes these global changes as briefly reviewed and summarized in this introductory paper comprised but are not limited to the following massive continental reorganization in the lead up to the final assembly of pangea resulting in profound changes in global palaeogeography palaeoceanography and palaeobiogeogarphy substantially lowered global atmospheric carbon dioxide concentrations p co 2 coupled with an unprecedented increase in atmospheric oxygen concentrations reaching earth s all time high in its last 600 million year history sharp global temperature and sea level drops albeit with considerable spatial and temporal variability throughout the ice age and apparently a prolonged period of global sluggish macro evolution with both low extinction and origination rates compared to other times in the aftermath of the lpia the world s climate entered into a transitional climate phase through the late early to middle permian before its transformation into a greenhouse state towards the end permian in recent years considerable amount of data and interpretations have been published concerning the physical evidence in support of the lpia its broad timeframe and eustatic and ecosystem responses from the lower latitudes but relatively less attention has been drawn to the impact of the ice age on late palaeozoic high latitude environments and biotas it is with this mission in mind that we have organized this special issue with the central focus on late palaeozoic high latitude regions of both hemispheres that is gondwana and northern eurasia our aim is to gather a set of papers that not only document the physical environmental changes that had occurred in the polar regions of gondwana and northern eurasia during the lpia but also review on the biotic responses at different taxonomic ecological and spatial scales to these physical changes in a refined chronological timeframe this introductory paper is designed to provide a global context for the special issue with a brief review of key late palaeozoic global environmental changes including changes in global land sea configurations atmospheric chemistry global climate regimes global ocean circulation patterns and sea levels and large scale biotic biogeographic and evolutionary responses followed by a summary of what we see as unresolved scientific issues and various working hypotheses concerning late palaeozoic global changes and in particular the lpia as a possible reference to future research

holocene glacier variations in new zealand a review abstract in the central southern alps of new zealand ice surface lowering has exposed extensive sections of lateral moraines allowing investigation of moraine stratigraphy and genesis the presence of multiple superposed palaeosurfaces within moraine sequences allows recognition of any disturbances displacements or contamination of till layers and interbedded organic material radiocarbon dating of buried wood and soils allows comparison between the holocene glacial history of the eastern ranges and that of the westland region the periodicity of glacier response has been similar to both areas although the precise timing of events has differed due to local climatic and environmental factors in general glaciers in new zealand expanded about 5000 4500 4200 3700 3500 3000 2700 2200 1800 1700 1500 1100 900 700 600 and 400 100 bp

glaciation in the andes during the lateglacial and holocene this review updates the chronology of andean glaciation during the lateglacial and the holocene from the numerous articles and reviews published over the past three decades the andes which include some of the world s wettest and driest mountainous regions offer an unparalleled opportunity to elucidate spatial and temporal patterns of glaciation along a continuous 68 degree meridional transect the geographic and altitudinal extent of modern glaciers and the sensitivity of both modern and former glaciers to respond to changes in specific climatic variables reflect broad scale atmospheric circulation and consequent regional moisture patterns glaciers in the tropical andes and in the mid latitude andes are likely to have been far more sensitive to changes in temperature than glaciers in the dry subtropical andes broad scale temporal and spatial patterns of glaciation during the lateglacial are apparent in the southernmost andes the lateglacial chronology appears to have a strong antarctic signature with the best dated moraines correlating closely with the antarctic cold reversal the southernmost andes do not appear to have experienced a significant ice advance coeval with the younger dryas yd climatic reversal at the other end of the andes from w 0t o 9 n a stronger yd connection may exist but critical stratigraphic and geochronologic work is required before a yd ice advance can be fully demonstrated in the central andes of peru well dated moraines record a significant ice readvance at the onset of the yd but ice was retreating during much of the remaining yd interval the spatial temporal pattern of holocene glaciation exhibits tantalizing but incomplete evidence for an early to mid holocene ice advance s in many regions but not in the arid subtropical andes where moraines deposited during or slightly prior to the little ice age lia record the most extensive advance of the holocene in many regions there is strong evidence for neoglacial advances in the interval between 1 0 and 2 5 ka moraines that correlate with the lia of the northern hemisphere are seen in all presently glacierized mountain ranges most of these date to within the past 450 years outboard of these moraines in many regions are moraines of a slightly more extensive advance that occurred several hundred years prior to the onset of the lia priorities for future work include filling in several prominent spatial gaps in the distribution of chronologic studies for the lateglacial these gaps include the arid regions of northern chile and argentina the southern peruvian andes between 11 5 and 13 5 s and the andes of northern peru and

the tekapo glacier new zealand during the last glacial maximum an active temperate glacier influenced by intermittent surge activity abstract quaternary glaciations have created impressive landform assemblages that can be used to understand palaeo glacier extent character and behaviour and hence past global and local glacier forcings however in the southern hemisphere and especially in new zealand the quaternary glacial landform record is relatively poorly investigated with regard to glaciological properties in this study a 1 m digital elevation model dem was generated from airborne lidar data and supplemented with aerial imagery and field observations to analyse the exceptionally well preserved glacial geomorphology surrounding lake tekapo new zealand we describe a rich suite of last glacial maximum lgm and recessional ice marginal subglacial supraglacial glaciofluvial and glaciolacustrine landform assemblages these represent two landsystems comprising i fluted till surfaces with low relief push moraine ridges and ii crevasse squeeze ridges zig zag eskers and attenuated lineations the former landsystem records the behaviour of an active temperate glacier and the latter landsystem which is superimposed upon and inset within the former strongly suggests intermittent surge phases the two landsystem signatures indicate a sequential change in ice marginal dynamics during recession that was likely to have been partially non climatically driven overall we present the first evidence of surge type glacier behaviour in new zealand

rise in frequency of surface melting at siple dome through the holocene evidence for increasing marine influence on the climate of west antarctica 1 a new melt layer history from siple dome west antarctica indicates notable late holocene summertime warming visual stratigraphic analyses of the 1004 m ice core identified 62 years with melt layers melting events began around 11 7 ka followed by a period of no melting from 8 8 6 6 ka melt layer frequency increased from 6 6 ka to the present with the 1000 year average melt layer frequency reaching a maximum of 2 at 0 8 ka we use our millennial scale archive of melt events as a unique seasonal paleothermometer to elucidate changes in west antarctic holocene summer climate our calibration suggests the change in melt frequency from 0 to 2 may represent a summer temperature increase of 2 c from the middle to late holocene this temperature change cannot be explained entirely by local change in ice elevation or summer insolation and is in contrast to east antarctic climate records which show peak warmth in the early holocene followed by stable or decreasing temperature we interpret the rise in melt frequency as evidence of an increasing marine influence on the ross sea sector of west antarctica although the surface elevation of siple dome has not changed greatly the continued lateral retreat of the west antarctic ice sheet from its last glacial maximum configuration across the outer continental shelf and the delayed drawdown in ice thickness from the adjacent coastal marie byrd land region in conjunction with periods of increased cyclogenesis perhaps related to variations in enso would allow a moderated maritime climate to more easily reach west antarctica

palaeoclimatology ice sheet history revealed by fossils microscopic fossils show that from 10 400 to 7 500 years ago upwelling of a water mass called circumpolar deep water destabilized antarctic ice shelves a finding that advances our understanding of ice sheet retreat see article p 43 the wind driven upwelling of circumpolar deep water cdw may be destabilizing antarctic ice shelves particularly in the region bordering the amundsen sea however firm evidence that these ice ocean interactions can persist long enough to cause substantial changes to ice sheets has been lacking here claus dieter hillenbrand et al present marine based palaeoclimate evidence to show that over much of the early holocene epoch and since the 1940s variations in the southern hemisphere westerly winds increased the upwelling of cdw this seemingly led to widespread deglaciations in the region and perhaps even a large ice shelf collapse the results confirm that the processes that have long been seen in models were operational in the past

southern weddell sea shelf edge geomorphology implications for gully formation by the overflow of high salinity water 1 submarine gullies are the most common morphological features observed on antarctic continental slopes the processes forming these gullies however remain poorly constrained in some areas gully heads incise the continental shelf edge and one hypothesis proposed is erosion by overflow of cold dense water masses formed on the continental shelf we examined new multibeam echo sounder bathymetric data from the weddell sea continental slope the region that has the highest rate of cold dense water overflow in antarctica ice shelf water isw cascades downslope with an average transport rate of 1 6 sverdrups sv in the southern weddell sea our new data show that within this region isw overflow does not deeply incise the shelf edge the absence of gullies extending deeply into the glacial sediments at the shelf edge implies that cold high salinity water overflow is unlikely to have caused the extensive shelf edge erosion observed on other parts of the antarctic continental margin instead the gullies observed in the southern weddell sea are relatively small and their characteristics indicative of small scale slides probably resulting from the rapid accumulation and subsequent failure of proglacial sediment during glacial maxima

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

glacial geomorphology and chronology of deglaciation south georgia sub antarctic we mapped and dated the glacial geomorphology of north east south georgia in the maritime sub antarctic the aim was to examine the timing of deglaciation of the island in the context of inter hemispheric phasing of climate change former glacier limits are restricted to the inner fjords and our detailed mapping of them has demonstrated a consistent geomorphological pattern that is similar across several different glacier types and sizes the pattern comprises three suites of moraines categories a c not all of which are represented at every site because the outer suite is often overridden by younger suites category a is an outer wide low amplitude moraine ridge category b comprises 2 4 sharp crested bouldery moraines that are often located close to or even over riding a and category c is a series of lower amplitude moraines with overprinted streamlined landforms such as flutings analysis of in situ cosmogenic 10be in boulders on these moraines has allowed us to determine a deglacial chronology for the older two moraine groups the age of the inner youngest group has been estimated from soil development the cosmogenic nuclide ages show that the outermost moraine was deposited ca 12 2 1 5 ka bp but that a subsequent readvance in the mid holocene ca 3 6 1 1 ka bp reached and in places over rode this earlier moraine this latter advance coincides with the mid holocene hypsithermal a final late holocene advance reached closely similar limits to the previous two fluctuations and is estimated from soil data to have an age of ca 1 1 ka bp we suggest that the close concordance of late glacial and interglacial limits in this case associated with warming can be explained by a change in dominant forcing during glacials extensive sea ice limits precipitation availability and so glaciers are restricted to the inner fjords during interglacials precipitation is not limited in the same way by sea ice cover and so during warming precipitation increases and tidewater glaciers on the island have responded by advancing this study emphasises the importance of a clear understanding of geomorphology in order to interpret chronological information

wobbly ocean conveyor circulation during the holocene abstract compared to the last glacial period the climate of the holocene has been quite stable however the record does suggest that at high latitudes in the north temperatures have cooled at least since the middle holocene and that this cooling has been modulated by millennial duration fluctuations that culminated in the medieval warm little ice age oscillation in this paper we explore the possibility that these variations were associated with concurrent changes in the strength of the atlantic s conveyor circulation three lines of evidence are considered one involves records that relate directly to ocean operation a second involves the tie between sea ice extent in the northern atlantic and the extent of mountain glaciers in the european alps and in the cordillera of western north america and a third involves evidence for a bipolarity in climate changes in the northern and southern polar regions in addition we look into clues provided by the atlantic multidecadal oscillation amo although at this point no firm conclusion can be drawn the case for ocean involvement is sufficiently strong to merit further attention

26al 10be 21ne burial dating abstract cosmogenic nuclide burial dating relies on a pair of cosmic ray produced nuclides that are produced in the same rock or mineral target at a fixed ratio but have different half lives for example 26 al and 10 be are produced in quartz at 26 al 10 be 6 75 1 if a sample of quartz is exposed at the surface for a time 26 al and 10 be concentrations reflect this ratio if it is then buried below the penetration depth of cosmic rays production stops and both nuclides decay the half life of 26 al is half that of 10 be so the 26 al 10 be ratio decreases over time and can be used to date the burial event because quartz derived from surface erosion and then buried by sediment accumulation is common the method is widely applicable for dating plio pleistocene clastic sediments all terrestrial applications of burial dating so far have used the 26 al 10 be pair here we show that coupling cosmogenic 21 ne which is also produced in quartz with 26 al or 10 be should improve upon both the age range and accuracy of 26 al 10 be burial dating we establish the feasibility of this approach by 21 ne measurements at two sites that have already been dated using 26 al 10 be burial dating burial ages from all three nuclide pairs agree at both sites which shows that currently accepted values for decay constants and production ratios are internally consistent thus it is possible at present to increase the useful range of cosmogenic nuclide burial dating by incorporating 21 ne fully realizing the potential improvements in accuracy would benefit from additional estimates of 21 ne 26 al and 21 ne 10 be production ratios that are independent of the 26 al and 10 be decay constants

lichenometric dating of the little ice age maximum in mt cook national park southern alps new zealand lichenometric dating studies using the yellow green rhizocarpon subgenus at the eugenie hooker mueller and tasman glaciers in mt cook national park southern alps new zealand reveal a little i

glacier and lake level variations in west central europe over the last 3500 years on the basis of glacier and lake level records this paper attempts for the first time a comparison between high resolution palaeohydrological and palaeoglaciological data in west central europe over the past 3500 years a data set of tree ring width radiocarbon and archaeological data in addition to historical sources were used to reconstruct fluctuations of the great aletsch the gorner and the lower grindelwald glaciers in the swiss alps the three ice streams experienced nearly synchronous advances at c 1000 600 bc and ad 500 600 800 900 1100 1200 and 1300 1860 these glacier fluctuations show strong correspondence with lake level variations reconstructed in eastern france jura mountains and pre alps and on the swiss plateau this supports the hypothesis of climatically driven fluctuations historical data available for the period since ad 1550 reveal in detail various meteorological conditions behind the successive glacier advances however in agreement with the general trend shown by th

glacial fluctuations since the medieval warm period at rothera point western antarctic peninsula at a global scale there is no evidence for synchronous multi decadal warm medieval warm period mwp or cold little ice age lia periods in the late holocene on the other hand there is go

fluctuations of the ultima esperanza ice lobe 52 s chilean patagonia during the last glacial maximum and termination 1 abstract we present a new record from the ultima esperanza region 51 25 52 25 s southwestern patagonia to unravel the timing and structure of glacial fluctuations during the last glacial termination t1 this sector of southern south america represents the only windward facing continental landmass in the southern hemisphere that intersects the core of the southern westerly wind belt geomorphic stratigraphic and geochronological evidence indicate the following stages during and since the last glacial maximum lgm i deposition of prominent moraine complexes during at least two advances dated between 39 and 17 5 ka ii development of an ice dammed proglacial lake glacial lake puerto consuelo accompanying ice recession iii active deposition of moraine complexes at intermediate positions followed by recession at 15 2 ka iv lake level drop and subsequent stabilization between 15 2 12 8 ka v a glacial readvance in glacial lake puerto consuelo between 14 8 12 8 ka vi ice recession stabilization and lake level lowering between 12 8 10 3 ka and vii glacial withdrawal and disappearance of glacial lake puerto consuelo prior to 10 3 ka by comparing our results with the chronologies from neighboring regions we explore whether there was a consistent temporal geographic pattern of glacial fluctuations during the lgm and t1 and examine their implications at regional hemispheric and global scales the correspondence of these variations with key paleoclimate events recorded in the southern and the northern hemispheres suggest a common forcing that most likely propagated through the atmosphere regional heterogeneities at millennial timescales probably reflect the influence of processes related to deep ocean circulation and changes in the position intensity of the antarctic polar front and southern westerly winds

early and mid holocene age for the tempanos moraines laguna san rafael patagonian chile data about the nature and timing of holocene events from the southern hemisphere especially in southern south america are required to provide insight into the extent and nature of past climate change in a region where land based records are restricted here we present the first use of single grain optically stimulated luminescence osl dating of a moraine sequence recording glacial advance along the western side of the patagonian icefields dates from the tempanos moraines at laguna san rafael lsr show that the san rafael glacier srg advanced to maximum holocene positions during the period 9 3 to 9 7 ka and at 5 7 ka outwash lying beneath the moraine in its northern portion dated to 7 7 ka indicates that the glacier front was also advanced at this time since these advances span both the regional early holocene warm dry phase 11 5 ka to 7 8 ka and the subsequent cooling and rise in precipitation in the mid late holocene since 6 6 ka we infer that the advances of the srg are not simply climate driven but that the glacier has also probably responded strongly to non climatic stimuli such as internal ice dynamics and the transition between calving and non calving many westwards flowing glaciers in patagonia were probably calving during much of the late pleistocene and holocene so we conclude that establishing robust glacial chronologies where climatic and non climatic factors cannot be distinguished is likely to remain a challenge

stratigraphy and correlation of glacial deposits from indiana to new york and new jersey the quaternary glacial history of part of the region from indiana to new york and new jersey fig 1 was outlined in three summaries prepared for the vii congress of the international union for quaternary research wayne and zumberge 1965 goldthwait et al 1965 muller 1965 subsequent regional summaries by white 1969 1982 white et al 1969 ray 1974 and coates 1976 reviewed the entire succession of tills in parts of kentucky northeastern ohio pennsylvania and new york other syntheses and discussions by dreimanis and goldthwait 1973 evenson and dreimanis 1976 dreimanis 1977 fullerton 1980 mayewski etal 1981 and mickelson et al 1983 were concerned only with late wisconsin tills the glacial history of the region fig 2 and chart 1 is much more complex than was assumed in 1965 much of the new information is in unpublished theses and dissertations and other publications of limited distribution and it has not been summarized correlations in chart 1 are based primarily on stratigraphic relationships of tills and paleosols and secondarily on radiometric ages paleomagnetic polarity data and relativeage data this summary serves as an expanded explanation of chart 1 glacial events are discussed within a framework of time divisions from older to younger and by glacial lobes as shown in chart 1 paleomagnetic polarity data in chart 1 are from harrison and terasmae 1961 bleuer 1976 and pers commun johnson 1976 this volume and pers commun hoyer 1977 1983 and pers commun bonnett et al 1978 and teller and last 1981 sources of data related to named tills in indiana ohio pennsylvania new york and new jersey are listed in appendix 1 the term glacial lobe here is applied both to a regional physiographically controlled pattern of ice dispersal and to the geographic region influenced by such movement huron erie lobe glaciation includes ice movement from the georgian bay region ontario into the lake erie basin as well as ice movement through the lake huron basin into the lake erie basin fig 3 illinoian and pre illinoian tills throughout the region have not been well studied and they have no radio

synchronous variability in the southern hemisphere atmosphere sea ice and ocean resulting from the annular mode zonally symmetric fluctuations of the midlatitude westerly winds characterize the primary mode of atmospheric variability in the southern hemisphere during all seasons this is true not only in observations but also in an unforced 15 000 yr integration of a coarse resolution r15 coupled ocean atmosphere model here it is documented how this mode of atmospheric variability known as the southern annular mode sam generates ocean circulation and sea ice variations in the model integration on interannual to centennial timescales that are tightly in phase with the sam the positive phase of the sam is associated with an intensification of the surface westerlies over the circumpolar ocean around 608s and a weakening of the surface westerlies farther north this induces ekman drift to the north at all longitudes of the circumpolar ocean and ekman drift to the south at around 308s through mass continuity the ekman drift generates anomalous upwelling along the margins of the antarctic continent and downwelling around 458s the anomalous flow diverging from the antarctic continent also increases the vertical tilt of the isopycnals in the southern ocean so that a more intense circumpolar current is also closely associated with positive sam in addition the anomalous divergent flow advects sea ice farther north resulting in an increase in sea ice coverage finally positive sam drives increases in poleward heat transport at about 308s while decreases occur in the circumpolar region ocean and sea ice anomalies of the opposite sign occur when the sam is negative the ocean and sea ice fluctuations associated with the sam constitute a significant fraction of simulated ocean variability poleward of 308s year round the robustness of the mechanisms relating the sam to oceanic variability suggests that the sam is likely an important source of large scale variability in the real southern hemisphere ocean

an early onset of enso influence in the extra tropics of the southwest pacific inferred from a 14 600 year high resolution multi proxy record from paddy s lake northwest tasmania abstract tropical el nino southern oscillation enso is an important influence on natural systems and cultural change across the pacific ocean basin el nino events result in negative moisture anomalies in the southwest pacific and are implicated in droughts and catastrophic wildfires across eastern australia an amplification of tropical el nino activity is reported in the east pacific after ca 6 7 ka however proxy data for enso driven environmental change in australia suggest an initial influence only after ca 5 ka here we reconstruct changes in vegetation fire activity and catchment dynamics e g erosion over the last 14 6 ka from part of the southwest pacific in which enso is the main control of interannual hydroclimatic variability paddy s lake in northwest tasmania 1065 masl australia our multi proxy approach includes analyses of charcoal pollen geochemistry and radioactive isotopes our results reveal a high sensitivity of the local and regional vegetation to climatic change with an increase of non arboreal pollen between ca 14 6 13 3 ka synchronous with the antarctic cold reversal and a sensitivity of the local vegetation and fire activity to enso variability recorded in the tropical east pacific through the holocene we detect local scale shifts in vegetation fire and sediment geochemistry at ca 6 3 4 8 and 3 4 ka simultaneous with increases in el nino activity in the tropical pacific finally we observe a fire driven shift in vegetation from a pyrophobic association dominated by rainforest elements to a pyrogenic association dominated by sclerophyllous taxa following a prolonged 1 ka phase of tropical enso amplification and a major local fire event at ca 3 4 ka our results reveal the following key insights 1 that enso has been a persistent modulator of southwest pacific climate and fire activity through the holocene 2 that the climate of northwest tasmania is sensitive to long term shifts in tropical enso variability and 3 that there has been possible stationarity in the spatial influence of enso over this region through the holocene

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

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

have the southern westerlies changed in a zonally symmetric manner over the last 14 000 years a hemisphere wide take on a controversial problem the prevailing view in the palaeoclimate literature of the last 20 years is that the southern westerly winds sww were intensified over southern australia and tasmania during the warmer than present early holocene 11e8 ka at similar latitudes on the opposite side of the southern mid latitudes palaeoclimate studies have suggested a poleward shift of the northern edge of the westerlies and focusing at 49 s in southern south america this zonal asymmetry contrasts with the modern day zonal symmetry displayed by the sww and poses a formidable challenge to an understanding of the modes of climatic variability of the southern extra tropics this paper presents an updated synthesis of continuous radiocarbon dated palaeoenvironmental data from the westerlies zone of influence in all southern hemisphere continents synchronous multi millennial trends in moisture vegetation fire and hydrologic balance are remarkably consistent with the way the sww changes impact upon the climate in southern hemisphere landmasses in the modern climate considering the modern relationships between local precipitation and zonal wind speeds it is suggested that the sww changed in a zonally symmetric manner at multi millennial scale between 14 and 5 ka regional asymmetry develops after 5 ka across the southern hemisphere with a pattern of precipitation anomalies akin to the modern functioning of el nino e southern oscillation which started w6200 years ago

holocene climate variability in antarctica based on 11 ice core isotopic records a comparison is made of the holocene records obtained from water isotope measurements along 11 ice cores from coastal and central sites in east antarctica vostok dome b plateau remote komsomolskaia dome c taylor dome dominion range d47 km105 and law dome and west antarctica byrd with temporal resolution from 20 to 50 yr the long term trends possibly reflect local ice sheet elevation fluctuations superimposed on common climatic fluctuations all the records confirm the widespread antarctic early holocene optimum between 11 500 and 9000 yr in the ross sea sector a secondary optimum is identified between 7000 and 5000 yr whereas all eastern antarctic sites show a late optimum between 6000 and 3000 yr superimposed on the long time trend all the records exhibit 9 aperiodic millennial scale oscillations climatic optima show a reduced pacing between warm events typically 800 yr whereas cooler periods are associated with less frequent warm events pacing 1200 yr

reconstructing spatially variable mass balances from past ice extents by inverse modeling with the conclusion of the last glacial maximum lgm about 20 000 years ago ended the most recent long lasting cold phase in earth history this last glacial advance left a strong observable imprint on the landscape such as moraines trimlines and other glacial geomorphic features these features reflect the extent of former glaciers and ice caps which in turn provides information on past temperature and precipitation conditions here we present an inverse approach to reconstruct the equilibrium line altitudes e from observed ice extents the ice flow model is developed solving the mass conservation equation using the shallow ice approximation and implemented using graphical processing units gpus we present the theoretical basis of the inversion method which relies on a tikhonov regularization and demonstrate its ability to constrain spatial variations in mass balance with idealized and real glaciers

holocene glacial history of antarctica and the sub antarctic islands abstract a history of holocene glaciation in the antarctic and sub antarctic affords insight into questions concerning present and future ice sheet and mountain glacier behavior and global climate and sea level change existing records permit broad correlation of holocene ice fluctuations within the region in several areas ice extent was less than at present in mid holocene time an important exception to this is the west antarctic ice sheet which has undergone continued recession throughout the holocene probably in response to internal dynamics the first neoglacial ice advances occurred at 5 0 ka although some sites e g western ross sea lack firm evidence for glacial expansion at that time glaciers in all areas underwent renewed growth in the past millennium and most have subsequently undergone recession in the past 50 years ranging from near catastrophic in parts of the antarctic peninsula to minor in the western ross sea region and sections of east antarctica this magnitude difference likely reflects the much greater warming that is taking place in the antarctic peninsula region today as compared to east antarctica

holocene glacier fluctuations a global overview of glacier advances and retreats grouped by regions and by millennia for the holocene is compiled from previous studies the reconstructions of glacier fluctuations are based on 1 mapping and dating moraines defined by 14 c tcn osl lichenometry and tree rings discontinuous records time series and 2 sediments from proglacial lakes and speleothems continuous records time series using 189 continuous and discontinuous time series the long term trends and centennial fluctuations of glaciers were compared to trends in the recession of northern and mountain tree lines and with orbital solar and volcanic studies to examine the likely forcing factors that drove the changes recorded a general trend of increasing glacier size from the earlyemid holocene to the late holocene in the extra tropical areas of the northern hemisphere nh is related to overall summer temperature forced by orbitally controlled insolation the glaciers in new zealand and in the tropical andes also appear to follow the orbital trend i e they were decreasing from the early holocene to the present in contrast glacier fluctuations in some monsoonal areas of asia and southern south america generally did not follow the orbital trends but fluctuated at a higher frequency possibly triggered by distinct teleconnections patterns during the neoglacial advances clustered at 4 4e4 2 ka 3 8e3 4 ka 3 3e2 8 ka 2 6 ka 2 3e2 1 ka 1 5e1 4 ka 1 2e1 0 ka 0 7e0 5 ka corresponding to general cooling periods in the north atlantic some of these episodes coincide with multidecadal periods of low solar activity but it is unclear what mechanism might link small changes in irradiance to widespread glacier fluctuations explosive volcanism may have played a role in some periods of glacier advances such as around 1 7e1 6 ka coinciding with the taupo volcanic eruption at 232 5 ce but the record of explosive volcanism is poorly known through the holocene the compilation of ages suggests that there is no single mechanism driving glacier fluctuations on a global scale multidecadal variations of solar and volcanic activity supported by positive feedbacks in the climate system may have played a critical role in holocene glaciation but further research on such linkages is needed the rate and the global character of glacier retreat in the 20th through early 21st centuries appears unusual in the context of holocene glaciation though the retreating glaciers in most parts of the northern hemisphere are still larger today than they were in the early and or mid holocene the current retreat

the late quaternary peat vegetation and climate history of the southern oceanic islands of new zealand abstract seven oceanic island groups chatham bounty snares antipodes auckland campbell and macquarie lie to the south and east of the southern new zealand mainland between the subtropical convergence and the antarctic convergence they are highly oceanic experiencing moist cool cloudy and windy climates deep peat soils cover most of the islands except for steep slopes and exposed high altitude sites the three large island groups chatham auckland and campbell support forest and tall scrub in the lowlands in the latter two grading with altitude through shrubland and grassland to upland tundra macrophyllous forbs create luxuriant herbfields in nutrient rich coastal sites and also as stunted forms dominate upland tundra associations the southernmost island macquarie has no woody species and is covered with tussock grassland herbfield and tundra vegetation cover is highly sensitive to soil saturation and exposure to the strong westerly winds of this region extensive oligotrophic bogs occur where drainage is poor and exposure high and forest and tall scrub are abundant only in sheltered well drained lowland sites glacial cirque levels indicate mean annual temperatures fell by 5 6 c during the last glacial maximum a depression of 6 10 c in sea surface temperatures is suggested by deep sea core analyses but this seems incompatible with terrestrial evidence auckland and campbell islands were extensively glaciated and grassland herbfield and tundra landscapes prevailed glaciers retreated by 15 000 yr bp and landscapes had stabilised and peat soils begun forming by 12 000 yr bp by the beginning of the holocene oligotrophic bog grassland and shrubland were dominant scrub and low forest spread slowly during the early holocene in the chatham auckland and campbell islands inhibited by cloudy moist climates low insolation and wet soils maximum extent of forest and scrub occurred between 6000 and 2000 yr bp most probably linked with a drying of the soils and increasing summer insolation upland sites and those exposed to westerly gales on auckland and campbell islands remained in grassland herbfield and bog throughout the holocene wind blown sand and stones in cliff edge peat profiles on auckland and campbell island from 8000 yr bp suggest strengthening westerly winds

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

high frequency holocene glacier fluctuations in new zealand differ from the northern signature understanding the timings of interhemispheric climate changes during the holocene along with their causes remains a major problem of climate science here we present a high resolution 10be chronology of glacier fluctuations in new zealand s southern alps over the past 7000 years including at least five events during the last millennium the extents of glacier advances decreased from the middle to the late holocene in contrast with the northern hemisphere pattern several glacier advances occurred in new zealand during classic northern warm periods these findings point to the importance of regional driving and or amplifying mechanisms we suggest that atmospheric circulation changes in the southwest pacific were one important factor in forcing high frequency holocene glacier fluctuations in new zealand

climatic influence of the latest antarctic isotope maximum of the last glacial period aim4 on southern patagonia abstract this paper presents the first detailed paleoclimate reconstruction of the latest antarctic isotope maximum aim4 33 29 ka cal bp at 52 s in continental southeastern argentine patagonia high resolution sedimentological and geochemical analyses of sediments from the maar lake potrok aike pta reveal a decrease in the thickness of flood induced turbidites and a series of wind burst deposits during aim4 both pointing to increasingly drier conditions this interpretation is also supported by a significant amount of runoff driven micropumices incorporated within the sediments that suggests a lower lake level with canyons incising thick tephra deposits around the lake increased gustiness and or dust availability in southeast patagonia together with intensified antarctic circumpolar circulation in the drake passage dust deposition in the scotia sea and in antarctica ice shelf are consistent with a southward shift of the southern westerly winds sww during the aim4 in contrast to other warmer aims the sww during the aim4 did not migrate far enough south to generate upwelling in the southern ocean and they did not reach 52 s in se patagonia as revealed by unchanged values of the rock magnetic proxy of wind intensity obtained from the same pta core nevertheless the sww displacement during aim4 imposed drier conditions at 52 s in southeast patagonia likely by blocking precipitation from the atlantic ocean in a way similar to modern seasonal variations and the other antarctic warm events

a reconstruction of extratropical indo pacific sea level pressure patterns during the medieval climate anomaly subtropical and extratropical proxy records of wind field sea level pressure slp temperature and hydrological anomalies from south africa australia new zealand patagonian south america and antarctica were used to reconstruct the indo pacific extratropical southern hemisphere sea level pressure anomaly slpa fields for the medieval climate anomaly mca 700 1350 ce and transition to the little ice age lia 1350 1450 ce the multivariate array of proxy data were simultaneously evaluated against global climate model output in order to identify climate state analogues that are most consistent with the majority of proxy data the mean slp and slp anomaly patterns derived from these analogues illustrate the evolution of low frequency changes in the extratropics the indo pacific extratropical mean climate state was dominated by a strong tropical interaction with antarctica emanating from 1 the eastern indian and south west pacific regions prior to 1100 ce then 2 the eastern pacific evolving to the central pacific la nina like pattern interacting with a ve sam to 1300 ce a relatively abrupt shift to ve sam and the central pacific el nino like pattern occurred at 1300 a poleward equatorward shift in the subtropical ridge occurred during the mca mca lia transition the hadley cell expansion in the australian and southwest pacific region together with the poleward shift of the zonal westerlies is contemporaneous with previously reported hadley cell expansion in the north pacific and atlantic regions and suggests that bipolar climate symmetry was a feature of the mca

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

extracting a climate signal from 169 glacier records i constructed a temperature history for different parts of the world from 169 glacier length records using a first order theory of glacier dynamics i related changes in glacier length to changes in temperature the derived temperature histories are fully independent of proxy and instrumental data used in earlier reconstructions moderate global warming started in the middle of the 19th century the reconstructed warming in the first half of the 20th century is 0 5 kelvin this warming was notably coherent over the globe the warming signals from glaciers at low and high elevations appear to be very similar

a new approach to calculating holocene winter precipitation by combining glacier equilibrium line altitudes and pine tree limits a case stud from hardangerjokulen central southern norway at hardangerjokulen central southern norway detailed knowledge of the number age and magnitude of holocene glacier fluctuations is used to reconstruct variations in equilibrium line altitude ela for the last 10 000 years present and past elas are based on an accumulation area ratio aar of 0 7 and are adjusted for land uplift a synchronous relationship between advanced glacier positions and the highest pine tree limits pinus sylvestris l is demonstrated for the early to mid holocene in southern scandinavia which indicates that warm summers were compensated for by high winter precipitation based on pine tree limit fluctuations as a measure of mean ablation season temperature holocene variations in winter precipitation at hardangerjokulen have been calculated by substitution in the close exponential relationship between mean ablation season temperature and winter precipitation at the ela of norwegian glaciers setting the winter precipitation during the period ad 1961 1990 at 100 mean values

deep south atlantic carbonate chemistry and increased interocean deep water exchange during last deglaciation abstract carbon release from the deep ocean at glacial terminations is a critical component of past climate change but the underlying mechanisms remain poorly understood we present a 28 000 year high resolution record of carbonate ion concentration a key parameter of the global carbon cycle at 5 km water depth in the south atlantic we observe similar carbonate ion concentrations between the last glacial maximum and the late holocene despite elevated concentrations in the glacial surface ocean this strongly supports the importance of respiratory carbon accumulation in a stratified deep ocean for atmospheric co 2 reduction during the last ice age after 9 mol kg decline during heinrich stadial 1 deep south atlantic carbonate ion concentration rose by 24 mol kg from the onset of bolling to pre boreal likely caused by strengthening north atlantic deep water formation bolling or increased ventilation in the southern ocean younger drays or both pre boreal the 15 mol kg decline in deep water carbonate ion since 10 ka is consistent with extraction of alkalinity from seawater by deep sea caco 3 compensation and coral reef growth on continental shelves during the holocene between 16 600 and 15 000 years ago deep south atlantic carbonate ion values converged with those at 3 4 km water depth in the western equatorial pacific as did carbon isotope and radiocarbon values these observations suggest a period of enhanced lateral exchange of carbon between the deep south atlantic and pacific oceans probably due to an increased transfer of momentum from southern westerlies to the southern ocean by spreading carbon rich deep pacific waters around antarctica for upwelling invigorated interocean deep water exchange would lead to more efficient co 2 degassing from the southern ocean and thus to an atmospheric co 2 rise during the early deglaciation

holocene variability of the southern hemisphere westerlies in argentinean patagonia 52 s abstract high resolution analyses of allochthonous pollen input into crater lake sediments of laguna potrok aike in the semi arid patagonian steppe reflect the variability of zonal wind intensities during the holocene at 52 southern latitude these indicators for southern hemisphere westerlies shw strength vary on centennial timescales in concert with carbon nitrogen c n ratios and titanium ti contents interpreted as differential organic matter sources and minerogenic input to the sediment respectively the correlations underline a linkage between hydrological variability and west wind variability in extra andean patagonia a shift to generally more intense shw suggests intensification towards modern wind conditions at that latitude since 9 2 ka cal bp

oceanic carbon and water masses during the mystery interval a model data comparison study 1 the mystery interval 17 5 14 5 ka bp is characterized by a large decline in atmospheric 14c synchronous with an increase in atmospheric co2 the most widely accepted hypothesis to explain these observed shifts involves the existence of an isolated old ocean carbon reservoir that was subsequently ventilated here we use the uvic earth system climate model to locate a potential carbon rich and 14c depleted water mass under 17 5 ka bp boundary conditions we then investigate two mechanisms for the potential ventilation of such a reservoir namely the weakening of the north atlantic meridional overturning due to iceberg calving and latitudinal shifts in southern hemisphere westerlies shw due to southern hemispheric warming we find that simulations derived from an equilibrium state forced with present day shw and moderate north atlantic deep water nadw formation are in better agreement with atmospheric and ocean 14c reconstructions than simulations derived from an equilibrium state forced with a northward shifted shw belt resulting in a shut down of the atlantic meridional overturning and formation of north pacific deep water for simulations with present day shw the oldest water masses are found in the north pacific although the southern ocean cannot be ruled out as a potential mystery reservoir according to our simulations the strength of atlantic overturning is the dominant mechanism in increasing the ocean atmosphere carbon flux while shifting shw results in a rearrangement of deep ocean carbon largely between the atlantic and pacific basins in our best case scenario the model can account for 58 of the atmospheric co2 increase and 48 of the atmospheric 14c decline while the rate of ventilation and the age of ventilated water masses are comparable with observations the ventilation in the model could not be sustained long enough to account for the full excursion seen in paleodata

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

the little ice age in the canadian rockies abstract this paper reviews the evidence and history of glacier fluctuations during the little ice age lia in the canadian rockies episodes of synchronous glacier advance occurred in the 12th 13th early 18th and throughout the 19th centuries regional ice cover was probably greatest in the mid 19th century although in places the early 18th century advance was more extensive glaciers have lost over 25 of their area in the 20th century selective preservation of the glacier record furnishes an incomplete chronology of events through the 14th 17th centuries in contrast varve sequences provide continuous annually resolved records of sediments for at least the last millennium in some highly glacierized catchments such records have been used to infer glacier fluctuations evaluation of recent proxy climate reconstructions derived from tree rings provides independent evidence of climate fluctuations over the last millennium most regional glacier advances follow periods of reduced summer temperatures reconstructed from tree rings particularly ca 1190 1250 1280 1340 1690s and the 1800s reconstructed periods of higher precipitation at banff alberta since 1500 are 1515 1550 1585 1610 1660 1680 and the 1880s glacier advances in the early 1700s the late 1800s and in places the 1950 1970s reflect both increased precipitation and reduced summer temperatures negative glacier mass balances from 1976 to 1995 were caused by decreased winter balances the glacier fluctuation record does not contain a simple climate signal it is a complex response to several interacting factors that operate at different timescales evaluation of climate proxies over the last millennium indicates continuous variability at several superimposed timescales dominated by decade century patterns only the 19th century shows a long interval of sustained cold summers this suggests that simplistic concepts of climate over this period should be abandoned and replaced with more realistic records based on continuous proxy data series the use of the term lia should be restricted to describing a period of extended glacier cover rather than being used to define a period with specific climate conditions

mechanisms of holocene palaeoenvironmental change in the antarctic peninsula region the antarctic peninsula is one of the three fastest warming regions on earth here we review holocene proxy records of marine and terrestrial palaeoclimate in the region and discuss possible forcing mechanisms underlying past change with a specific focus on past warm periods our aim is to critically evaluate the mechanisms by which palaeoclimate changes might have occurred in order to provide a longer term context for assessing the drivers of recent warming two warm events are well recorded in the holocene palaeoclimate record namely the early holocene warm period and the mid holocene hypsithermal mhh whereas there are fewer proxy data for the mediaeval warm period mwp and the recent rapid regional rrr warming we show that the early holocene warm period and mhh might be explained by relatively abrupt shifts in position of the southern westerlies superimposed on slower solar insolation changes a key finding of our synthesis is that the marine and terrestrial records in the ap appear to show markedly different behaviour during the mhh this might be partly explained by contrasts in the seasonal insolation forcing between these records circumpolar deep water cdw has been implicated in several of the prominent changes through the holocene but there are still differences in interpretation of the proxy record that make its influence difficult to assess further work is required to investigate contrasts between marine and terrestrial proxy records east west contrasts in palaeoclimate the history of cdw to retrieve a long onshore high resolution record of the holocene and determine the role of sea ice in driving or modulating palaeoclimate change along with further efforts to study the proxy record of the rrr and the mwp

temperature accumulation and ice sheet elevation in central greenland through the last deglacial transition we present a combined heat and ice flow model constrained by measurements of temperature in the greenland ice sheet project 2 gisp2 borehole and by the gisp2 18o record and depth age scale which determines a history of temperature accumulation rate and ice sheet elevation for the past 50 000 years in central greenland important results are that the temperature increase from average glacial to holocene conditions was large approximately 15 c with a 20 c warming from late glacial to holocene that the average accumulation rate during the last glacial maximum between 15 and 30 kyr b p was 5 5 to 7 cm yr 1 approximately 25 of the modern accumulation rate that long term 500 1000 years averaged accumulation rate and temperature have been inversely correlated during the most recent 7 millennia of the holocene and that the greenland ice sheet probably thickened during the deglacial transition the inverse correlation of accumulation rate and temperature in the mid and late holocene suggests that the greenland ice sheet is more prone to volume reduction in a warmed climate than previously thought and demonstrates that accumulation rate is not a reliable proxy for temperature the elevation history of the ice sheet is poorly constrained by the model and independent evidence is needed we also present a simple estimate of the response time for thinning of the interior region of an ice sheet due to retreat of its margins this was approximately 1900 years for central greenland during deglaciation

a diatom conductivity transfer function for reconstructing past changes in the southern hemisphere westerly winds over the southern ocean sub antarctic islands are ideally placed to reconstruct past changes in southern hemisphere westerly wind behaviour they lie within their core belt 50 60 s and the strong winds deliver sea salt ions to the islands resulting in a west to east conductivity gradient in their water bodies this means that the stronger or weaker the winds the higher or lower the conductivity values measured in the water bodies a survey of the water chemistry and diatom assemblages of lakes and ponds on sub antarctic campbell island 52 32 s 169 8 e revealed that similar to other sub antarctic islands conductivity was the most important statistically significant ecological variable explaining turnover in diatom community structure based on this a diatom conductivity transfer function was developed simple weighted averaging with inverse deshrinking r2 0 86 r2jack 0 66 rmsep 0 25 log10 s cm 1 this transfer function will be applied to lake sediment cores from the western edge of the campbell island plateau to reconstruct past conductivity sea spray and therefore directly reconstruct changes in southern hemisphere westerly wind strength within their core belt

late glacial and holocene palaeoenvironmental change in the central strait of magellan southern patagonia abstract high resolution palaeoenvironmental data for the wisconsin late glacial and early holocene is provided from two sites puerto del hambre and estancia esmeralda ii in the central section of the strait of magellan southern chile palaeoecological and lithostratigraphical evidence is correlated with other palaeoenvironmental data from the magellan region using 14 c dating and tephrochronology the oldest record from puerto del hambre commences at 14 470 14 c yr bp 17 330 cal yr bp following retreat of the magellan glacier climatic warming after that time is indicated by ice retreat from the central section of the strait of magellan and palynological evidence however mean annual temperature continued to be cooler than present until c 10 300 14 c yr bp 12 270 12 110 cal yr bp the magellan environment was relatively humid between c 14 100 and c 12 550 14 c yr bp 16 910 and 15 170 14 410 cal yr bp at c 12 550 14 c yr bp there was a sharp decrease in effective moisture levels of humidity fluctuated but remained relatively low until c 10 300 14 c yr bp this period of cool and drier climate is contemporary with a significant glacier advance dated to between c 12 700 and 10 300 14 c yr bp 15 330 and 12 270 12 110 cal yr bp which would have produced an enhanced rainshadow effect around 10 300 14 c yr bp a shift to warmer conditions occurred between c 10 300 and 8550 14 c yr bp 12 270 12 110 and 9530 cal yr bp an extreme arid phase is recorded which led to an increase in fires at c 8550 14 c yr bp an increase in available moisture allowed the eastward spread of nothofagus forest at 8265 14 c yr bp 9270 9160 cal yr bp there was a relative rise in sea level in the strait of magellan this marine incursion lasted until 3970 14 c yr bp 4420 cal yr bp reaching its maximum around c 6450 14 c yr bp 7420 7340 cal yr bp

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

late quaternary vegetation and climate of southern tierra del fuego vegetation and climate over approximately the past 13 000 yr are reconstructed from fossil pollen in a 9 4 m mire section at caleta robalo on beagle channel isla navarino 54 56 s 67 38 w southern tierra del fuego fifty surface samples reflecting modern pollen dispersal serve to interpret the record chronologically controlled by nine radiocarbon dates fossil pollen assemblages are empetrum gramineae gunnera tubuliflorae zone 3b 13 000 11 850 yr b p gramineae empetrum assorted minor taxa zone 3a 11 850 10 000 yr b p nothofagus gramineae tubuliflorae polypodiaceae zone 2 10 000 5000 yr b p nothofagus empetrum zone 1b 5000 3000 yr b p and empetrum nothofagus zone 1a 3000 0 yr b p assemblages show tundra under a cold dry climate zone 3 followed by open woodland zone 2 as conditions became warmer and less dry and later with greater humidity and lower temperatures by closed forest and the spread of mires zone 1 comparisons drawn with records from antarctica new zealand tasmania and the subantarctic islands demonstrate broadly uniform conditions in the circumpolar southern hemisphere the influences of continental and maritime antarctic air masses were apparently considerable in tierra del fuego during cold late glacial time whereas holocene climate was largely regulated by interplay between maritime polar and maritime tropical air

gisp2 oxygen isotope ratios the gisp2 oxygen isotope record with its high resolution detail yields crucial information on past climate change the glacial 18o oscillations of the gisp2 core with their very fast onsets are templates of a prototype oscillation of variable duration with an amplitude of 3 9 the halfway mark of the cold warm transition is reached in 2 years the top is reached in 50 years the 18o time gradient of the leading front is about 7 8 per 100 yr after reaching the top 18o slowly declines by 0 14 per 100 yr the duration of 18o decline varies from a couple of centuries for fast oscillations to about 4000 yr for slower ones the subsequent 18o downturn during the warm cold transition has a 18o time gradient of 3 2 per 100 yr and lasts about 80 yr

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

microsedimentological characterization using image analysis and μ xrf as indicators of sedimentary processes and climate changes during lateglacial at laguna potrok aike santa cruz argentina palaeoclimatic and paleoenvironmental high latitude records in the southern hemisphere are scarce compared to the northern counterpart however understanding global evolution of environmental systems during sudden climate changes is inseparable from an equivalent knowledge of both hemispheres in this context a high resolution study of lacustrine sediments from laguna potrok aike santa cruz province patagonia argentina was conducted for the lateglacial period using concurrent x ray fluorescence xrf and scanning electron microscope analyses peaks of ca si and mn and occurrences of the green alga phacotus lenticularis have been interpreted as variations in ventilation of the water column from 13 6 to 11 1 ka cal bp during this interval mild climate conditions during the younger dryas are characterized by relatively weak westerlies favouring the formation of a stratified water body as indicated by preserved manganese and ca si peaks and high total organic carbon toc values in this environment water in the epilimnion can reach sufficiently high temperature to allow p lenticularis to grow colder conditions are marked by peaks in ca without p lenticularis and occur during the antarctic cold reversal acr in this lateglacial interval micropumices were also detected in large amount image analysis of thin sections allowed the counting and size measurement of detrital particles and micropumices separately micropumices significantly influence the iron and titanium content hence preventing to use them as proxies of detrital input in this interval

changes in el nino southern oscillation enso conditions during the greenland stadial 1 gs 1 chronozone revealed by new zealand tree rings the warming trend at the end of the last glacial was disrupted by rapid cooling clearly identified in greenland greenland stadial 1 or gs 1 and europe younger dryas stadial or yd this reversal to glacial like conditions is one of the best known examples of abrupt change but the exact timing and global spatial extent remain uncertain whilst the wider atlantic region has a network of high resolution proxy records spanning gs 1 the pacific ocean suffers from a scarcity of sub decadally resolved sequences here we report the results from an investigation into a tree ring chronology from northern new zealand aimed at addressing the paucity of data the conifer tree species kauri agathis australis is known from contemporary studies to be sensitive to regional climate changes an analysis of a historic 452 year kauri chronology confirms a tropical pacific teleconnection via the el nino southern oscillation enso we then focus our study on a 1010 year sub fossil kauri chronology that has been precisely dated by comprehensive radiocarbon dating and contains a striking ring width downturn between 12 500 and 12 380 cal bp within gs 1 wavelet analysis shows a marked increase in enso like periodicities occurring after the downturn event comparison to low and mid latitude pacific records suggests a coherency with enso and southern hemisphere atmospheric circulation change during this period the driver s for this climate event remain unclear but may be related to solar changes that subsequently led to establishment and or increased expression of enso across the mid latitudes of the pacific seemingly independent of the atlantic and polar regions

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

evolution of the meridional shift of the subtropical and subpolar westerly jet over the southern hemisphere during the past 21 000 years abstract deciphering the variations in the subtropical westerly jet stj and the subpolar westerly jet spj over the southern hemisphere in earth s history will help us to better understand how the westerlies may respond to various external forcings in the future using simulation of transient climate evolution over the past 21 000 years simulations we demonstrate that the stj migrated equatorward in the last glacial maximum relative to the present which followed by abrupt poleward equatorward and poleward shifts during the heinrich stadial i antarctic cold reversal and younger dryas respectively these large amplitude fluctuations are controlled by changes in meltwater fluxes and polar ice sheet topography during the holocene the stj shows no obvious long term trend due to the offsetting effect between increased orbital insolation in austral summer and decreased antarctic ice sheet topography the meridional shift of the spj shows an in phase change with the stj during the past 21 kyr in terms of the dynamic mechanisms the meridional shift of the stj and spj is induced by changes in the meridional temperature gradient and the maximum eddy growth rate respectively and is also linked to changes in the mean meridional circulations that is the hadley and ferrel cells the modeled meridional shift of the southern westerlies is supported by the results from the paleoclimate modelling intercomparison project phase and is consistent with several reconstructions but it is difficult to constrain robustly by geological evidence as the reconstructed westerlies vary across sites and proxies nevertheless our study provides a possible scenario for the evolution of the southern westerlies during the past 21 kyr and identifies the dominant forcing and the associated mechanisms which may advance our knowledge on the future behavior of the southern westerlies

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

intensified southern hemisphere westerlies regulated atmospheric co2 during the last deglaciation the causes for the rise of atmospheric co 2 during the last deglaciation are complex and remain a matter of controversial scientific discussion one hypothesis explains this phenomenon with co 2 release from the deep ocean a change in atmosphere ocean interaction induced by a shift or intensification of southern hemisphere westerlies shw could have stimulated this process here this hypothesis is tested using oxygen isotope ratios of aquatic cellulose from patagonian lacustrine sediments as west wind proxy our record indicates maximum shw strength at 52 s between 13 4 and 11 3 calibrated kyr b p this is in agreement with an increase in zonal wind strength extending to the southern mid latitudes during the younger dryas chronozone triggering the final co 2 increase comparison with other southern hemisphere records implies southward migration of strengthened shw at that time leading to interglacial co 2 levels and hence terminating the last glacial

subantarctic peatlands and their potential as palaeoenvironmental and palaeoclimatic archives subantarctic islands are located within the antarctic circumpolar current and the southern westerly wind belt the latter called southern westerlies making them unique terrestrial archives to investigate past changes in oceanic and atmospheric circulation patterns in the southern mid latitudes the islands are characterised by a treeless phanerogam poor flora in which bryophytes are of major importance several peat based holocene palaeoenvironmental and palaeoclimatic studies have recently been published for south georgia and ile de la possession iles crozet a range of techniques have been used in these studies mainly plant macrofossil analysis but also analyses of diatoms pollen and non pollen microfossils geochemical and geomagnetic measurements the records are chronologically constrained by radiocarbon dating this paper brings together these data in order to give an overview of the subantarctic peat based palaeoclimatic records a new plant macrofossil record for the island of south georgia is added evidence for millennial scale holocene climate variability was found for both islands of which the most striking one occurred in the late holocene however within the uncertainty of the age depth models the timing for this climate shift to wetter and or colder conditions on south georgia and windier wetter conditions on ile de la possession is different for both islands ile de la possession iles crozet seems to follow the northern hemisphere climate evolution as the event was dated to w2800 cal bp a well known climate event present in many peat based records in north western europe in contrast the south georgian late holocene climate records reveal a shift around w2200e2000 cal bp

reconstructing atmospheric circulation over southern new zealand establishment of modern westerly airflow 5500 years ago and implications for southern hemisphere holocene climate change abstract late twentieth century changes in the intensity and migration of southern hemisphere westerly winds have been implicated in spatially complex variability in atmospheric and ocean circulation and ice sheet dynamics across the mid to high latitudes a major uncertainty however is whether present day hemispheric wide symmetrical airflow is representative of past behaviour here we report a multi proxy study from stewart island and southern fiordland new zealand 46 47 s reconstructing holocene changes at the northern limit of westerly airflow increased minerogenic input and a pronounced shift in cool loving vegetation around 5500 years ago is consistent with the establishment of westerly airflow at this latitude in the southwest pacific in marked contrast stronger winds are reported further south over the subantarctic auckland 50 s and campbell 52 s islands from 8000 years ago intriguingly reconstructions from the east pacific suggest a weakening of core westerly airflow after 8500 years ago but an expansion along the northern limits sometime after 5500 years ago our results suggest similar atmospheric circulation changes have been experienced in the pacific since 5500 years ago but indicate an expanded network of sites is needed to comprehensively test the driver s and impact s of holocene mid latitude westerly winds across the southern hemisphere

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

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

the temperature of europe during the holocene reconstructed from pollen data we present the first area average time series reconstructions of warmest month coldest month and mean annual surface air temperatures across europe during the last 12 000 years these series are based on quantitative pollen climate reconstructions from over 500 pollen sites assimilated using an innovative four dimensional gridding procedure this approach combines three dimensional spatial gridding with a fourth dimension represented by time allowing data from irregular time series to be focussed onto a regular time step we provide six regional reconstructed temperature time series as well as summary time series for the whole of europe the results suggest major spatial and seasonal differences in holocene temperature trends within a remarkably balanced regional and annual energy budget the traditional mid holocene thermal maximum is observed only over northern europe and principally during the summer this warming was balanced by a mid holocene cooling over southern europe whilst central europe occupied an intermediary position changes in annual mean temperatures for europe as a whole suggest an almost linear increase in thermal budget up to 7800 bp followed by stable conditions for the remainder of the holocene this early holocene warming and later equilibrium has been mainly modulated by increasing winter temperatures in the west which have continued to rise at a progressively decreasing rate up to the present day

late holocene glacier reconstruction reveals retreat behind present limits and two stage little ice age on subantarctic south georgia observational data show that climate in the southern ocean region is rapidly changing however past the instrumental period our understanding of climate variability in the region is limited by a scarcity of highresolution palaeoclimate records alpine glaciers present on many southern ocean islands may provide such data because changes in their mass balance extent and erosion rates often mark a response to climate shifts rock flour the fine grained fraction of the glacial erosion process is suspended in meltwater streams and transferred into the sediments of downstream lakes continuously recording glacier variations here we utilize this relationship to present a reconstruction of the late holocene glacier history of subantarctic south georgia using sediments from the glacier fed middle hamberg lake to fingerprint a glacial erosion size signal we used titanium counts validated against changes in sediment density and grain size allowing a continuous reconstruction of glacier variations over the past similar to 1250 years together with local moraine evidence and supporting evidence from other southern hemisphere glaciers on new zealand and in patagonia our findings reveal a series of consecutively diminishing late holocene advances in addition to a glacier maximum before 1250 cal a bp these include a twostage litle ice age with advances around 300 and 120 cal a bp in line with evidence from southern patagonia in addition we present evidence for an unreported retreat behind present limits around 500 cal bp

geochemical methods to infer landscape response to quaternary climate change and land use in depositional archives a review abstract understanding and quantifying the processes and geochemical cycles associated with catchment erosion the development of soils and weathering horizons and terrestrial habitat change beyond the scales of modern observations remain challenging such research however has become increasingly important to help predict future landscape change in light of increasing land use and rapid global warming we herein review organic and inorganic geochemical tools applied to depositional archives to better understand various aspects of landscape evolution on geological time scales we highlight the potentials and limitations of inorganic geochemical analytical methods such as major element geochemistry metal and radiogenic isotopes and in situ cosmogenic nuclides as qualitative semi quantitative and quantitative proxies for the transformation of bedrock material via regolith and soils to sediments we also show how stable isotope geochemistry applied to lacustrine endogenic carbonates can be used to infer rock water interactions vegetation change and soil development in limestone rich catchments proxies focusing on the silicilastic element of sediment formation transport and deposition are ideally combined with organic geochemical proxies for vegetation change and soil organic matter evolution in a catchment to gain a comprehensive picture of the critical zone s evolution over time multi proxy and multidisciplinary research combining organic and inorganic geochemical techniques from several sedimentary archives in the same catchment have high potential to provide comprehensive information on quaternary landscape evolution and thus improve the robustness of associated forecasting models

multi proxy analyses of a peat bog on isla de los estados easternmost tierra del fuego a unique record of the variable southern hemisphere westerlies since the last deglaciation we have analyzed an almost 14 000 year old peat sequence on the island of isla de los estados 55 degrees s 64 degrees w east of tierra del fuego in the core of the southern hemisphere westerlies a multitude of methods have been used high resolution c 14 dating detailed lithologic descriptions including humification degree loss on ignition magnetic susceptibility bulk density pollen and spore analysis and determination of aeolian sand influx by combining proxies for wind and precipitation we have been able to reconstruct how the westerlies have varied over time in the atlantic sector of the southern ocean it shows that this westerly wind belt was most intense at the onset of the record 13 600 13 200 cal bp coinciding with the mid to late part of the antarctic cold reversal followed by a gradual decline at 12 200 cal bp the westerlies seem to have shifted to a position south of tierra del fuego and this phase the calmest and driest period on the island throughout the sequence ended at 10 000 cal bp when the westerlies moved equatorward again since then the westerlies have been present but with a variable impact on the 55 degrees s latitude of the atlantic mostly conditions have been fairly similar to today but occasionally with a wider or narrower and or weaker or stronger wind belt at 7200 cal bp wind intensity began to increase and between 4500 and 3500 cal bp these southern latitudes experienced a distinct wind and precipitation maximum both in terms of perseverance and intensity our results show a both wide and strong wind belt with possible niveo aeolian activity in tierra del fuego in winter and possibly creating milder summers around the antarctic peninsula in the later part of the holocene expansion contraction phases of the wind belt especially in winter seem to have been a common phenomenon c 2012 elsevier ltd all rights reserved

multiproxy record of holocene paleoenvironmental change tierra del fuego argentina abstract we interpret holocene environmental conditions in a subantarctic high andean valley from palynological and diatom analysis peat stratigraphy and local geomorphology the multiproxy data from las cotorras mire 54 41 13 s 68 02 51 w 420 m a s l indicate the development of a soligenous mire as a result of a fine grained tephra layer deposition over the mineral soils sometime prior to 8000 cal yr bp the paleoecological conditions in the mire after 8000 cal yr bp show a rapid succession from a limnic to a telmatic stage as the mire is colonized by sedges cyperaceae and herbaceous communities the upland vegetation changed from cushion and shrub heaths to an expansion of nothofagus forest at high altitudes after 6500 cal yr bp the peat is interbedded with clastic sediment that originates from mass wasting events or floods these depositional changes affected the mire ecosystem water table level and nutrient status oligotrophic and or eutrophic conditions maxima in total pollen influx at about 2800 1100 and 700 cal yr bp coincide with heightened mineral flux and these changes are related to precipitation and slope processes the major vegetational change registered in the pollen record is the decline of nothofagus pollen after 1000 cal yr bp which reaches a minimum between ca 680 and 300 cal yr bp this minimum was likely caused by cool wet conditions that coincided with the little ice age lia in the southern hemisphere our results indicate the sensitivity of subantarctic nothofagus forest and mire ecosystems to changes during the holocene