millennial scale sea surface temperature and patagonian ice sheet changes off southernmost chile 53 s over the past 60 kyr 1 glacial millennial scale paleoceanographic changes in the southeast pacific and the adjacent southern ocean are poorly known due to the scarcity of well dated and high resolution sediment records here we present new surface water records from sediment core md07 3128 recovered at 53 s off the pacific entrance of the strait of magellan the alkenone derived sea surface temperature sst record reveals a very strong warming of ca 8 c over the last termination and substantial millennial scale variability in the glacial section largely consistent with our planktonic foraminifera oxygen isotope 18o record of neogloboquadrina pachyderma sin the timing and structure of the termination and some of the millennial scale sst fluctuations are very similar to those observed in the well dated sst record from odp site 1233 41 s and the temperature record from drowning maud land antarctic ice core supporting the hemispheric wide antarctic timing of sst changes however differences in our new sst record are also found including a long term warming trend over marine isotope stage mis 3 followed by a cooling toward the last glacial maximum lgm we suggest that these differences reflect regional cooling related to the proximal location of the southern patagonian ice sheet and related meltwater supply at least during the lgm consistent with the fact that no longer sst cooling trend is observed in odp site 1233 or any sst chilean record this proximal ice sheet location is documented by generally higher contents of ice rafted debris ird and tetra unsaturated alkenones and a slight trend toward lighter planktonic 18o during late mis 3 and mis 2

preliminary evidence of early deglaciation in southern chile abstract the end of the last ice age in the channels of southern chile is recorded by resumed sedimentation in formerly ice filled basins to identify the timing of initial ice retreat in southern chile we examined ice proximal sediments from a proglacial lake along the eastern margin of the magallanes ice sheet an environment thought to be sensitive to initial melting porter s c clapperton c m sugden d e 1992 chronology and dynamics of deglaciation along and near the strait of magellan southernmost south america sver geol unders 81 233 239 ams radiocarbon dates of the supra till deposits in two cores indicate that sedimentation resumed 18 radiocarbon kyr deposition in kettle holes and bogs on the adjacent land surfaces began at the same time or earlier 17 25 radiocarbon kyr clapperton c m sugden d e kaufman d s mcculloch r d 1995 the last glaciation in central magellan strait southernmost chile quat res 44 133 148 our preliminary interpretation is that these events indicate initial deglaciation in the region and the formation of a large proglacial lake followed several thousand years later by the invasion of salt water as sea level rose deglaciation in southern chile occurred too early to be forced by the resumption of north atlantic deep water formation sea level rise or northern hemisphere summer insolation and we suggest instead that southern insolation played a role the time of initial deglaciation in southern chile 21 27 calendar kyr occurred as southern hemisphere annual insolation increased from a minimum at 29 calendar kyr 6 w m 2 less than today at 80 s

the last glaciation in central magellan strait southernmost chile abstract glacial landforms and drift stratigraphy in central magellan strait southernmost chile document repeated fluctuations during the last glacial cycle of outlet lobes from an ice cap centered over the southern andes the lobes developed comparatively low gradient profiles because of low basal shear stresses over soft deformable beds and this made them sensitive to even small scale changes in the mass balance such low profiles and rapid calving in deep proglacial lakes during deglaciation may have made the magellan ice lobe particularly responsive to climatic fluctuations during the last glacial cycle and to advance and retreat over considerable distances study of the glacial landforms and drift stratigraphy has led to the identification of at least five glacier advances to limits at and south of the segunda angostura fragments of mollusc shells contained in basal till indicate marine incursions between some advances thus documenting extensive deglaciation a partial chronology based on amino acid studies and radiocarbon dating suggests that five of these advances occurred during the last glacial cycle the most extensive advances may have culminated during substages of marine isotope stage 5 substage 5b or 5d and or during stage 4 slightly less extensive advances occurred between ca 28 000 and 14 000 yr b p

the evolution of the patagonian ice sheet from 35 ka to the present day patice abstract we present patice a gis database of patagonian glacial geomorphology and recalibrated chronological data patice includes 58 823 landforms and 1 669 geochronological ages and extends from 38 s to 55 s in southern south america we use these data to generate new empirical reconstructions of the patagonian ice sheet pis and subsequent ice masses and ice dammed palaeolakes at 35 ka 30 ka 25 ka 20 ka 15 ka 13 ka synchronous with the antarctic cold reversal 10 ka 5 ka 0 2 ka and 2011 ad at 35 ka the pis covered of 492 6 x103 km2 had a sea level equivalent of 1 496 mm was 350 km wide and 2090 km long and was grounded on the pacific continental shelf edge outlet glacier lobes remained topographically confined and the largest generated the suites of subglacial streamlined bedforms characteristic of ice streams the pis reached its maximum extent by 33 28 ka from 38 s to 48 s and earlier around 47 ka from 48 s southwards net retreat from maximum positions began by 25 ka with ice marginal stabilisation then at 21 18 ka which was then followed by rapid irreversible deglaciation by 15 ka the pis had separated into disparate ice masses draining into large ice dammed lakes along the eastern margin which strongly influenced rates of recession glacial readvances or stabilisations occurred at least at 14 13 ka 11 ka 6 5 ka 2 1 ka and 0 5 0 2 ka we suggest that 20th century glacial recession a 1 is occurring faster than at any time documented during the holocene

elevated mercury accumulation in a peat bog of the magellanic moorlands chile 53 s an anthropogenic signal from the southern hemisphere increasing mercury deposition rates in the northern hemisphere recorded in natural archives such as peat bogs or lake sediments have been documented in numerous studies however data on atmospheric hg deposition in the southern hemisphere dating back to pre industrial times are rare here we provide a continuous record of atmospheric hg deposition in the southern hemisphere recorded by an ombrotrophic peat bog of the magellanic moorlands chile 53 s extending back 3000 yr pre industrial mercury accumulation rates range between 2 5 and 3 9 wg m 2 yr in the past 100 yr hg accumulation rates increased 18 fold from about 3 wg m 2 yr to a maximum of 62 5 wg m 2 yr if hg accumulation rates were normalized to peat accumulation rates maximum rates were 7 9 wg m 2 yr which is only 2 5 times the pre industrial rates thus hg accumulation rates normalized to peat accumulation rates are more comparable to the three fold net increase in atmospheric hg concentrations estimated for the same period we suggest that the increase in hg accumulation rates in the magellanic moorlands within the past 100 yr is at least partly attributed to global dispersion of hg derived from anthropogenic sources in the northern hemisphere the finding that no increase of atmospheric deposition of pb could be observed in the bog indicates the extraordinary long range transport and ubiquitous dispersion of anthropogenic derived gaseous hg compared to other metals 2002 elsevier science b v all rights reserved

deglacial sea level record from tahiti corals and the timing of global meltwater discharge the timing of the last deglaciation is important to our understanding of the dynamics of large ice sheets1 and their effects on the earth s surface2 3 moreover the disappearance of the glacial ice sheets was responsible for dramatic increases in freshwater fluxes to the oceans which probably disturbed the ocean s thermohaline circulation and hence global climate4 7 sea level increases bear witness to the melting of continental ice sheets but only two such records from barbados8 9 and new guinea10 11 corals have been accurately dated but these corals overlie active subduction zones where tectonic movements are large and often discontinuous especially in new guinea so the apparent sea level records may be contaminated by a complex tectonic component here we date fossil corals from tahiti which is far from plate boundaries and thus is likely to be tectonically relatively stable and remote from the locations of large former ice sheets the resulting record indicates a large sea level jump shortly before 13 800 calendar years bp which corresponds to meltwater pulse 1a in the barbados coral records8 9 the timing of this event is more accurately constrained in the tahiti record revealing that the meltwater pulse coincides with a short and intense climate cooling event12 15 that followed the initiation of the bolling allerod warm period12 16 but preceded the younger dryas cold event by about 1 000 years

rapid rise of sea level 19 000 years ago and its global implications evidence from the irish sea basin supports the existence of an abrupt rise in sea level meltwater pulse at 19 000 years before the present b p climate records indicate a large reduction in the strength of north atlantic deep water formation and attendant cooling of the north atlantic at this time indicating a source of the meltwater pulse from one or more northern hemisphere ice sheets warming of the tropical atlantic and pacific oceans and the southern hemisphere also began at 19 000 years b p these responses identify mechanisms responsible for the propagation of deglacial climate signals to the southern hemisphere and tropics while maintaining a cold climate in the northern hemisphere

climatic variability in the eastern united states over the past millennium from chesapeake bay sediments salinity oscillations caused by multidecadal climatic variability had major impacts on the chesapeake bay estuarine ecosystem during the past 1000 yr microfossils from sediments dated by radiometry 14 c 137 cs 210 pb and pollen stratigraphy indicate that salinity in mesohaline regions oscillated 10 15 ppt during periods of extreme drought low fresh water discharge and wet climate high discharge during the past 500 yr 14 wet dry cycles occurred including sixteenth and early seventeenth century megadroughts that exceeded twentieth century droughts in their severity these droughts correspond to extremely dry climate also recorded in north american tree ring records and by early colonists wet periods occurred every 60 70 yr began abruptly lasted 20 yr and had mean annual rainfall 25 30 and fresh water discharge 40 50 greater than during droughts a shift toward wetter regional climate occurred in the early nineteenth century lowering salinity and compounding the effects of agricultural land clearance on bay ecosystems

late holocene marine productivity changes in northern patagonia chile inferred from a multi proxy analysis of jacaf channel sediments abstract a multi proxy approach based on organic organic carbon alkenones and c n and inorganic geochemical proxies biogenic opal inorganic carbon fe ti and ca preserved in the sediments of the jacaf channel cf7 pc33 44 21 s 72 58 w 510 m water depth chilean fjords yields evidence of major past productivity fluctuations in accordance with climatic changes over the last 1800 years the downcore record clearly shows two productivity climate modes the first period prior to 900 cal yr bp is characterized by decreased marine productivity and a reduced continental signal pointing to diminished precipitation and runoff in contrast the second period between 750 cal yr bp and the late 1800s top of core is illustrated by elevated productivity and an increased continental signal suggesting higher precipitation and runoff both time intervals are separated by a relatively abrupt transition of 150 years which roughly coincides with the beginning of the little ice age the increased content of freshwater diatoms and chrysophyte cysts that characterize the last 200 years of the latter mode coincides with a significant decrease in the carbonate content of the sediment together they further indicate increased terrigenous contributions and decreased marine carbonate productivity at the end of the little ice age the correspondence between our record and other paleoclimate studies carried out in south america and antarctica demonstrates that the chilean fjord area of northern patagonia is not just sensitive to local climatic variability but also to regional and possibly global variability

high resolution marine record of climatic change in mid latitude chile during the last 28 000 years based on terrigenous sediment parameters abstract marine sediment cores from the continental slope off mid latitude chile 33 s were studied with regard to grain size distributions and clay mineral composition the data provide a 28 000 yr14c accelerator mass spectrometry dated record of variations in the terrigenous sediment supply reflecting modifications of weathering conditions and sediment source areas in the continental hinterland these variations can be interpreted in terms of the paleoclimatic evolution of mid latitude chile and are compared to existing terrestrial records glacial climates 28 000 18 000 cal yr b p were generally cold humid with a cold semiarid interval between 26 000 and 22 000 cal yr b p the deglaciation was characterized by a trend toward more arid conditions during the middle holocene 8000 4000 cal yr b p comparatively stable climatic conditions prevailed with increased aridity in the coastal range the late holocene 4000 0 cal yr b p was marked by more variable paleoclimates with generally more humid conditions variations of rainfall in mid latitude chile are most likely controlled by shifts of the latitudinal position of the southern westerlies compared to the holocene the southern westerly wind belt was located significantly farther north during the last glacial maximum less important variations of the latitudinal position of the southern westerlies also occurred on shorter time scales

climatic inferences from glacial and palaeoecological evidence at the last glacial termination southern south america there is uncertainty about the interhemispheric timing of climatic changes during the last glacial interglacial transition different hypotheses relying on different lines of evidence point variously to the northern hemisphere leading the southern hemisphere and vice versa or to synchrony between the hemispheres southern south america is well placed to test the various alternatives using both glacial and palaeoecological evidence we argue here from a synthesis of key proxy records that there was a sudden rise in temperature that initiated deglaciation sychronously over 16 of latitude at 14 600 14 300 14 c yr bp 17 500 17 150 cal yr there was a second step of warming in the chilean lake district at 13 000 12 700 14 cy r bp 15 650 15 350 cal yr which saw temperatures rise to close to modern values a third warming step particularly clear in the south occurred at ca 10 000 14 c yr bp 11 400 cal yr the latter achieving holocene levels of warmth following the initial warming there was a lagged response in precipitation as the westerlies after a delay of ca 1600 yr migrated from their northern glacial location to their present latitude which was attained by 12 300 14 cy r bp 14 300 cal yr the latitudinal contrasts in the timing of maximum precipitation are reflected in regional contrasts in vegetation change and in glacier behaviour the large scale of a 80 km glacier advance in the strait of magellan at 12 700 10 300 14 c yr bp 15 350 12 250 cal yr which spans the antarctic cold reversal and the younger dryas was influenced by the return of the westerlies to southern latitudes the delay in the migration of the westerlies coincides with the heinrich 1 iceberg event in the north atlantic the suppressed global thermohaline circulation at the time may have affected sea surface temperatures in the south pacific and the return of the westerlies to their present southerly latitude only followed ocean reorganisation to its present interglacial mode copyright 2000 john wiley sons ltd

similar meltwater contributions to glacial sea level changes from antarctic and northern ice sheets the period between 75 000 and 20 000 years ago was characterized by high variability in climate and sea level southern ocean records of ice rafted debris suggest a significant contribution to the sea level changes from melt water of antarctic origin in addition to likely contributions from northern ice sheets but the relative volumes of melt water from northern and southern sources have yet to be established here we simulate the first order impact of a range of relative meltwater releases from the two polar regions on the distribution of marine oxygen isotopes using an intermediate complexity model by comparing our simulations with oxygen isotope data from sediment cores we infer that the contributions from antarctica and the northern ice sheets to the documented sea level rises between 65 000 and 35 000 years ago were approximately equal each accounting for a rise of about 15 m the reductions in antarctic ice volume implied by our analysis are comparable to that inferred previously for the antarctic contribution to meltwater pulse 1a refs 16 17 which occurred about 14 200 years ago during the last deglaciation

a gis based weights of evidence model for mapping cliff instabilities associated with mine subsidence the weights of evidence w of e technique was applied within a geographic information system gis to derive a model of rockfall potential associated with mining induced subsidence the purpose of the model was to describe the potential for rockfalls from up to 60 m high steep sandstone gorges and slopes associated with proposed underground longwall operations within the immediate vicinity of a previously mined area ten known rock falls associated with the previous mining operation were used as training points six evidential themes were considered slope cliff height planform curvature profile curvature the distance of the cliff areas from the longwall panels and the distance of the cliff areas from the river two models were created one based on a mine layout in which longwall panels extend beneath the steep areas of a nearby river and a second in which the mine layout is modified so that mining does not occur directly beneath or within 50 m of the steep slopes this is to allow for the comparison of rockfall potential based on different mining configurations the results demonstrate that the w of e method is a suitable tool for mine subsidence impact assessment and suggest that not mining directly under the nepean river may decrease rockfall potential on average by approximately ten times numerous limitations with the results relating to the availability of appropriate evidential theme data and the accuracy of training points are discussed

enhanced sediment scavenging due to double diffusive convection abstract river water intruding into a lake or ocean typically results in a surface layer of warm sediment laden water overriding relatively dense cold fluid though this system is stable with respect to density instability may arise as a result of the different diffusivities of sediment and heat a series of experiments were conducted which indicated that double diffusive convection ddc was responsible for rapid sedimentation of slowly settling particles a simple theory based upon relevant physical processes is developed that describes this behavior it also incorporates the previously neglected effects of ambient stratification on the strength of the ddc application of the theory and our results to field data taken from oceanic river plumes demonstrates that the flux due to double diffusive sedimentation dds can be at least as strong as flocculation enhanced gravitational settling

apparent long term cooling of the sea surface in the northeast atlantic and mediterranean during the holocene reconstructions of upper ocean temperature t during the holocene 10 0 ka b p were established using the alkenone method from seven high accumulation sediment cores raised from the northeast atlantic and the mediterranean sea 361n 751n all these paleo t records document an apparent long term cooling during the last 10 kyr in records with indication of a constant trend the apparent cooling ranges from 0 27 to 0 151c kyr 1 records with indication of time variable trend show peak to peak amplitudes in apparent temperatures of 1 2 2 91c a principal component analysis shows that there is one factor which accounts for a very large fraction 67 of the total variance in the biomarker paleo t records and which dominates these records over other potential secondary influences two possible contributions are 1 a widespread surface cooling which may be associated with the transition fromthe hypsithermal interval b9 5 7 ka b p to the neoglaciation b5 7 0 ka b p and 2 a change in the seasonal timing and or duration of the growth period of alkenone producers prymnesiophyte algae the first contribution is consistent with many climate proxy records from the northeast atlantic area and with climate model simulations including milankovitch forcing the second contribution is consistent with the divergence between biomarker and summer faunal paleo t fromearly to late holocene observed in two cores further work is necessary and in particular the apparent discordance between biomarker and faunal t records for the relative stable holocene period must be understood to better constrain the climatic and ecological contributions to the apparent cooling observed in the former records r 2002 elsevier science ltd all rights reserved

rapid uplift of southern alaska caused by recent ice loss summary extreme uplift rates and sea level changes in southern alaska have been documented by global positioning system gps surveys tide gauge measurements and studies of raised shorelines the movements detected in a network of 45 gps survey points describe a broad pattern of rapid regional uplift the majority of the study area is uplifting at a rate faster than 10 mm yr 1 with several sites uplifting more rapidly than 25 mm yr 1 new tide gauge data presented here consist of repeat occupations of 18 temporary gauge sites sea level rates at these sites agree with similar measurements in southern alaska taken 50 yr earlier and also with the pattern of uplift derived from the gps data raised shoreline studies at 14 sites document total sea level change with a maximum change in sea level of 5 7 m found in upper lynn canal the start of the ongoing uplift episode that raised these shorelines has been dated with dendrochronology and found to be coincident with the start of the collapse of the glacier bay icefield at ca 1750 ad the pattern of total sea level change is in general agreement with upliftrate measurements with greater sea level change found at the sites closest to the peak uplift rates in upper glacier bay we use a viscoelastic earth model subjected to an ice load history built upon observations of glacial change to predict uplift rates at the tide gauge and gps sites as well as the total uplift at the raised shoreline sites our modelling exercises are limited to an ice load model based on independent studies of the region s glacial history over the past 1 7 kyr to evaluate whether the uplift observations can be explained by simple earth models subjected to this load history two layer earth models consisting of an elastic crust and a low viscosity upper mantle half space can be adjusted to fit either the raised shoreline data or the combined gps and tide gauge uplift rate data but cannot fit all the data with a single set of earth model parameters however all three data sets are consistent with an approximated three layer earth model the combined model is constrained by a total of 77 uplift measurements which at the 95 per cent confidence level require a low viscosity asthenosphere a 1 4 0 3 10 19 pa s and thickness 110 20

holocene sea level changes along the strait of magellan and beagle channel southernmost south america abstract radiocarbon dated marine sediments from five coastal sites along the strait of magellan and beagle channel in southernmost chile permit construction of a curve of relative sea level fluctuations during the holocene morphologic and stratigraphic data point to coastal submergence during the early holocene as the sea rose to a maximum level at least 3 5 m higher than present about 5000 yr ago progressive emergence then followed during the late holocene data from widely separated localities define a smooth curve the form of which is explainable in terms of isostatic and hydroisostatic deformation of the crust resulting from changing ice and water loads apparently anomalous data from one site located more than 100 km behind the outer limit of the last glaciation may reflect isostatic response to deglaciation the sea level curve resembles one derived by clark and bloom 1979 in proceedings of the 1978 international symposium on coastal evolution in the quaternary sao paulo brasil pp 41 60 sao paulo using a spherical earth model both in amplitude and in the timing of the maximum submergence

observations of intratidal variability of flows over a sill contraction combination in a chilean fjord underway velocity measurements were carried out for the first time in a chilean fjord using an acoustic doppler velocimeter with the purpose of elucidating the intratidal variability of flows through a pass paso galvarino the pass included a sill where the bottom sloped by roughly 30 and a coastline contraction of 90 the relatively small dimensions of the pass allowed for rapid sampling of the flow evolution throughout the tidal cycle the backscattered sound signal from the velocimeter and from an echo sounder were used to describe the vertical excursions of the pycnocline throughout the domain and to identify regions of enhanced vertical mixing within the pass the spatial variability of the flow in the pass was consistent with uniform two layer flow at the narrowest section of the contraction the pycnocline dropped sharply around both maximum flood and maximum ebb while the flow accelerated downstream relative to the tidal flow the slope of the pycnocline changed sign from flood to ebb which was atypical of other fjord observations but could be explained by the transitions from subcritical to supercritical flow these transitions switched location at either side of the narrowest section of the contraction leeward of this section increased sound backscatter suggested intensified turbulence that extended over a greater area during ebb than during flood because the distance between the point of pycnocline drop and the end of the pass was longer during ebb enhanced vertical mixing within the pass was reflected in the tidally averaged fields by a three layer flow that consisted of near surface and near bottom flow converging toward the pass and flow around the pycnocline diverging away from the pass

antarctic timing of surface water changes off chile and patagonian ice sheet response marine sediments from the chilean continental margin are used to infer millennial scale changes in southeast pacific surface ocean water properties and patagonian ice sheet extent since the last glacial period our data show a clear antarctic timing of sea surface temperature changes which appear systematically linked to meridional displacements in sea ice westerly winds and the circumpolar current system proxy data for ice sheet changes show a similar pattern as oceanographic variations offshore but reveal a variable glacier response time of up to 1000 years which may explain some of the current discrepancies among terrestrial records in southern south america

the significance of chemical isotopic and detrital components in three coeval stalagmites from the superhumid southernmost andes 53 s as high resolution palaeo climate proxies abstract stalagmites are important palaeo climatic archives since their chemical and isotopic signatures have the potential to record high resolution changes in temperature and precipitation over thousands of years we present three u th dated records of stalagmites ma1 ma3 in the superhumid southern andes chile 53 s they grew simultaneously during the last five thousand years ka bp in a cave that developed in schist and granodiorite major and trace elements as well as the c and o isotope compositions of the stalagmites were analysed at high spatial and temporal resolution as proxies for palaeo temperature and palaeo precipitation calibrations are based on data from five years of monitoring the climate and hydrology inside and outside the cave and on data from 100 years of regional weather station records water insoluble elements such as y and hree in the stalagmites indicate the amount of incorporated siliciclastic detritus monitoring shows that the quantity of detritus is controlled by the drip water rate once a threshold level has been exceeded in general drip rate variations of the stalagmites depend on the amount of rainfall however different drip water pathways above each drip location gave rise to individual drip rate levels only one of the three stalagmites ma1 had sufficiently high drip rates to record detrital proxies over its complete length carbonate compatible element contents e g u sr mg which were measured up to sub annual resolution document changes in meteoric precipitation and related drip water dilution in addition these soluble elements are controlled by leaching during weathering of the host rock and soils depending on the ph of acidic pore waters in the peaty soils of the cave s catchment area in general higher rainfall resulted in a lower concentration of these elements and vice versa the mg ca record of stalagmite ma1 was calibrated against meteoric precipitation records for the last 100 years from two regional weather stations carbonate compatible soluble elements show similar patterns in the three stalagmites with generally high values when drip rates and detrital tracers were low and vice versa 13c and 18o values are highly correlated in each stalagmite suggesting a predominantly drip rate dependent kinetic control by evaporation and or outgassing only c and o isotopes from stalagmite ma1 that received the highest drip rates show a good correlation between detrital proxy elements and carbonate compatible elements a temperature related change in rainwater isotope values modified the ma1 record during the little ice age 0 7 0 1 ka bp that was 1 5 c colder than today the isotopic composition of the stalagmites ma2 and ma3 that formed at lower drip rates shows a poor correlation with stalagmite ma1 and all other chemical proxies of ma1 hendy tests indicate that the degassing controlled isotope fractionation of ma2 and ma3 had already started at the cave roof especially when drip rates were low changing pathways and residence times of the seepage water caused a non climatically controlled isotope fractionation which may be generally important in ventilated caves during phases of low drip rates our proxies indicate that the neoglacial cold phases from 3 5 to 2 5 and from 0 7 to 0 1 ka bp were characterised by 30 lower precipitation compared with the medieval warm period from 1 2 to 0 8 ka bp which was extremely humid in this region

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

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

geomorphology avalanches and moraines the waiho loop moraine in new zealand s southern alps had long been viewed as a southern icon of a recent glacier response to cooling climate possibly the younger dryas cold event but a closer look has implicated a landslide in this particular glacial advance

late pleistocene to holocene marine transgression and thermohaline control on sediment transport in the western magellanes fjord system of chile 53 s abstract in the western strait of magellan in southernmost chile marine transgression occurred between 14 500 and 13 500 cal bp this is indicated by strongly increased accumulation of biogenic carbonate and first appearance of foraminifers in sediment records from that time until 11 500 cal bp sedimentation in the western fjords became predominant autochthonous due to higher salinity and clay flocculation and late glacial glacier retreat present day thermohaline zonation pattern extensively representative for the holocene and sedimentation rates indicate that westerlies hampered westward outflow of superficial 0 30 m water depth glacial clay rich freshwater from glaciated areas during the holocene isostatic uplift of the andes overcompensated sea level rise in areas with high glacial glacier loading this led to shallowing fjord sills and restricted exchange with marine water especially since high freshwater inflow produced strong pycnoclines and preserved old saline water in fjord bottoms to the east of the climate divide the seno skyring fjord system shows a year round stable stratification despite a strong wind induced eastward superficial current in the upper 30 50 m of the water column such currents enabled significant late glacial eastward transport of glacial clay sediment cores from this area indicate that east ward sediment flux slowed down during the holocene probably due to less intense westerlies investigated present day thermohaline characteristics of the fjord system across the superhumid climate divide of the southern andes indicate details of the exchange between marine and freshwater which are fundamental for evaluation of sediment transport pathways biogenic productivity and interpretation of paleoclimate records in this area

little ice age glacier fluctuations gran campo nevado southernmost chile moraine systems of glaciar lengua unofficial name and neighbouring glaciers of gran campo nevado 53 s in the southernmost andes were mapped and dated by dendrochronological means they were formed around ad 1628 1872 1875 1886 1902 1912 and 1941 with the advance in the 1870s being calendar dated recessional moraines within each moraine system correspond to brief standstills or minor readvances a significantly older moraine could not be directly dated by dendrochronological methods as the forest on it was assumed to be second generation or older from soil formation rates it is assumed that this moraine was formed at some time between ad 1280 and 1460 a time in which many other glaciers in patagonia formed moraines overall fluctuations of glaciar lengua show a strong synchronicity to other glaciers in the patagonian andes between 41 s and 55 s this study suggests that glaciar lengua and possibly all glaciers of gran campo nevado reached their holocene maximum during the little ice age

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

holocene tephrochronology record of large explosive eruptions in the southernmost patagonian andes for regionally widespread holocene tephra layers in southernmost patagonia correlations based on both chemical and chronological data indicate their derivation from five large volume 1 km3 explosive eruptions of four different volcanoes in the southernmost andes bulk tephra and tephra glass major and trace element chemistry and sr isotopic ratios unambiguously distinguish different source volcanoes and imply that two of the regionally widespread tephra mb1 and mb2 were derived from mt burney 52 s one r1 from reclus 51 s one a1 from aguilera 50 s and one h1 from hudson volcano 46 s the h1 tephra derived from the hudson volcano which is located at the southern end of the andean southern volcanic zone svz 33 46 s contains distinctive greenish andesitic glass with feo 4 5 wt and tio2 1 2 wt in contrast rhyolitic glass in tephra derived from the eruptions of mt burney reclus and aguilera volcanoes which are located in the andean austral volcanic zone avz 49 55 s is clear and transparent and has significantly lower feo and tio2 tephra derived from these three avz volcanoes all contain plagioclase orthopyroxene minor clinopyroxene and amphibole biotite occurs only in the aguilera a1 tephra which also has the highest bulk tephra and tephra glass k2o and rb contents averages of new and published 14c ages determined on organic material in soil and sediment samples above and below these tephra constrain the uncalibrated 14c age of the r1 eruption of reclus volcano to 12 685 260 years bp the mb1 and mb2 eruptions of mt burney to 8 425 500 and 3 830 390 years bp the hudson h1 eruption to 6 850 160 years bp and the a1 eruption of aguilera volcano to 3 000 100 years bp the volume of the largest of these eruptions h1 of the hudson volcano is estimated as 18 km3 the volume of the reclus r1 eruption is estimated at 10 km3 the aguilera a1 eruption at between 4 and 9 km3 and the younger mt burney mb2 eruption at 2 8 km3 the volume of the older mb1 mt burney eruption is the least well constrained but must have been larger than the younger mb2 eruption the data indicate that the frequency of explosive activity of volcanic centers in the avz is lower than in the southern svz

timing of millennial scale climate change in antarctica and greenland during the last glacial period a precise relative chronology for greenland and west antarctic paleotemperature is extended to 90 000 years ago based on correlation of atmospheric methane records from the greenland ice sheet project 2 and byrd ice cores over this period the onset of seven major millennial scale warmings in antarctica preceded the onset of greenland warmings by 1500 to 3000 years in general antarctic temperatures increased gradually while greenland temperatures were decreasing or constant and the termination of antarctic warming was apparently coincident with the onset of rapid warming in greenland this pattern provides further evidence for the operation of a bipolar see saw in air temperatures and an oceanic teleconnection between the hemispheres on millennial time scales

glacier modeling and the climate of patagonia during the last glacial maximum ice cap modeling constrained by empirical studies provides an effective way of reconstructing past climates the former patagonian ice sheet is in a climatically significant location since it lies athwart the southern hemisphere westerlies and responds to the latitudinal migration of climatic belts during glacial cycles a numerical model of the patagonian ice cap for the last glacial maximum lgm is developed which is time dependent and driven by changing the mass balance altitude relationship it relies on a vertically integrated continuity model of ice mass solved over a finite difference grid the model is relatively insensitive to ice flow parameters but highly sensitive to mass balance the climatic input is adjusted to produce the best fit with the known limits of the ice cap at the lgm the ice cap extends 1800 km along the andes and has a volume of 440 000 km3 during the lgm the equilibrium line altitude ela was lower than at present by at least 560 m near latitude 40 s 160 m near latitude 50 s and 360 m near latitude 56 s the latitudinal variation in ela depression can be explained by an overall fall in temperature of about 3 0 c and the northward migration of precipitation belts by about 5 latitude annual precipitation totals may have decreased by about 0 7 m at latitude 50 s and increased by about 0 7 m at latitude 40 s the ela rises steeply by up to 4 m per kilometer from west to east as the westerlies cross the andes and this prevents ice growth to the east the limited decrease in temperature during the lgm could be related to the modest migration of the antarctic convergence between south america and the antarctic peninsula

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

isoprenoid and branched gdgt based proxies for surface sediments from marine fjord and lake environments in chile abstract proxies based on glycerol dialkyl glycerol tetraether gdgt lipids from archaea isoprenoid gdgts and bacteria branched br gdgts in 33 surface sediments from marine fjord and lake systems between 25 s and 50 s in chile were analyzed the regional texh86 calibration obtained from the marine and fjord sediments and mean annual surface temperature t 59 6 texh86 33 0 r2 0 9 n 23 is statistically identical to the global ocean calibration based on suspended particulate material in terms of slope but not in terms of intercept the regional surface and subsurface texh86 calibrations were statistically different from the existing global ocean core top calibrations the tex86 calibration model based on most of the relatively large lakes studied here t 50 7 tex86 11 8 r2 0 9 n 5 is statistically identical to the global lake calibration the relatively high tex86 values from smaller lakes suggested an additional source for isoprenoid gdgts likely terrestrial or aquatic methanogenic archaea application of the soil calibrated mbt cbt methylation and cyclization of br gdgts respectively temperature proxy to the marine and fjord sediments resulted in an overestimation of continental mean annual air temperature maat suggesting in situ production of certain br gdgts in the water column or surface sediment for the lakes mbt cbt based surface air temperature estimates were 3 6 c below maat however temperature estimates from the lake specific mbt cbt global calibration were in good agreement with mean annual surface temperature for all the lakes the results highlight the need for testing local vs global calibrations of gdgt based proxies before their application for palaeoenvironmental reconstruction