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

multiproxy analysis of a lateglacial holocene sedimentary section in the fuegian steppe northern tierra del fuego argentina implications for coastal landscape evolution in relation to climatic variability and sea level fluctuations abstract we report the sedimentology palynology geochemistry and diatom assemblages of a well dated succession at laguna las vueltas lv on the atlantic coast of the fuegian steppe in southern argentina the multiproxy analysis offers a unique opportunity to study the evolution of this coastal landscape in relation to past sea level and climate changes in the southern high latitudes after ca 19 000 cal yr bp the sediments were subjected to subaerial exposure and oxidation linked to a low sea level the sr ba ratio a paleosalinity geochemical parameter indicates variations in the water body level and diatoms imply the existence of an ephemeral and brackish freshwater body subject to desiccation under arid conditions between ca 11 600 and 8500 cal yr bp a shrubby steppe vegetation mainly composed of asteraceae subf asteroideae spread over the coastal area associated with a shallow freshwater body and the deposition of fine grained sediments in low energy environments all indicative of low effective moisture and warm climate conditions between ca 8500 and 8100 cal yr bp salt carpet vegetation dominated by chenopodiaceae developed around a coastal lagoon in response to the holocene marine transgression the record of dinocysts and geochemical data indicate marine influence at this time between ca 8100 and 7000 cal yr bp salt marshes colonized the coastal area a coastal lagoon with a more restricted connection to the sea and minor freshwater input are inferred linked to the beginning of a regressive phase after ca 7000 cal yr bp grassland vegetation and an open shrub stratum developed along with a shallow lake pan that was disconnected from the sea following a fall in the sea level and regression fluctuations in the water level of the pan and changes in the physical chemical conditions as indicated by fluctuations in mn fe ti ca rb sr ca tic and toc suggest abrupt events of desiccation and flooding between ca 4500 and 2000 cal yr bp a drier phase is indicated by changes in vegetation algal content and geochemistry of the pan a grassland vegetation and a shallow lake with seasonal water level variations characterized the last 2000 years our results from llv area match well with andean forest fluctuations and regional climatic conditions recorded from tierra del fuego and chilean southwest

paleobotanical evidence for near present day levels of atmospheric co2 during part of the tertiary understanding the link between the greenhouse gas carbon dioxide co 2 and earth9s temperature underpins much of paleoclimatology and our predictions of future global warming here we use the inverse relationship between leaf stomatal indices and the partial pressure of co 2 in modern ginkgo biloba and metasequoia glyptostroboides to develop a co 2 reconstruction based on fossil ginkgo and metasequoia cuticles for the middle paleocene to early eocene and middle miocene our reconstruction indicates that co 2 remained between 300 and 450 parts per million by volume for these intervals with the exception of a single high estimate near the paleocene eocene boundary these results suggest that factors in addition to co 2 are required to explain these past intervals of global warmth

high spatial resolution electron probe microanalysis of tephras and melt inclusions without beam induced chemical modification wavelength dispersive analysis of tephra grains and melt inclusions by epma has been carried out using a focused beam of 3 m diameter without detected loss of sodium or potassium in standard glasses including anhydrous basalts a slightly hydrated rhyolite and a sodium rich intermediate composition the ability to make analyses without chemical modification is strongly dependent upon current density at the analysis site analysis with narrow beams requires extremely low beam currents that are normally associated with energy dispersive analysis experiments indicate that a value of 0 1 na m2 must not be exceeded at least for moderately hydrated samples if sodium loss is to be avoided high resolution analysis without beam induced analytical artefacts enables fully quantitative analysis of very distal and or highly vesicular tephras and very small melt inclusions without the need to use post analysis corrections this development has enabled high quality analyses from crypto tephra layers that were pre

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

paleolimnological response to climate variability during late glacial and holocene times a record from lake arturo located in the fuegian steppe southern argentina abstract last glacial maximum and holocene environmental conditions are reconstructed from a lacustrine core obtained from lake arturo located in the fuegian steppe of southern argentina proxies include diatoms ostracods plants remains organic matter content and sedimentological studies and they suggest that lake arturo experienced climate related variations in the water level hydrological balance and temporal stability throughout the last 23 200 cal yr bp the late glacial period which ended about 15 400 cal yr bp is characterized by a few low diversity diatom assemblages dominated by benthic and small celled fragilarioid taxa between the pleistocene holocene transition and the mid holocene lake arturo was a shallow fresh to brackish lake with relatively high organic productivity around 6200 cal yr bp the diatom surirella tuberosa replaced thalassiosira patagonica and diatom species richness fell to its lowest level in the records together with the presence of the ostracod limnocythere rionegroensis which lives in ephemeral environments this suggests that the lake was very shallow and experienced negative hydrological balance with hydrochemical and biological conditions that were similar to those of today data from other sites in southern tierra de fuego suggest that around 5000 cal yr bp until 800 cal yr bp the rainfall increased and the temperature decreased as a result of an intensification of the southern westerlies by that time the lake arturo record indicates the existence of an ephemeral shallow highly saline water body this suggests an antiphase response to the atmospheric circulation pattern between the southern humid forest and the northern steppe during the middle to late holocene

dynamics of former ice lobes of the southernmost patagonian ice sheet based on a glacial landsystems approach reconstructions of former ice masses from glacial geomorphology help to constrain the nature and timing of glaciation in relation to climatic forcing this paper presents a new reconstruction of the glacial history of five ice lobes in southernmost south america the bahia inutil san sebastian magellan otway skyring and rio gallegos ice lobes we use previous geomorphological mapping of glacial landforms to reconstruct former glacial limits and proglacial lakes demarcate flow sets from the distribution of glacial lineations and evaluate glacial landsystem signatures and their palaeoglaciological implications evidence suggests that the ice lobes predominantly reflect active temperate glacial landsystems which may have switched to polythermal systems when periods of cold based ice developed ephemerally this complex landsystem signature implies that the ice lobes were sensitive to regional climate variability with active re advances during overall retreat of the ice margins there is also evidence for periods of fast ice flow and possible surge like activity in the region followed by the rapid retreat or even collapse of some of the ice lobes in association with proglacial lakes constraining our new reconstruction with published chronological information suggests that at least some of the ice lobes advanced before the global last glacial maximum glgm ca 26 5 19 ka during the last glacial cycle our new reconstruction demonstrates a more complex picture of ice dynamics than has previously been portrayed and one in which the advance and retreat of the ice lobes was likely to have been primarily driven by changes in climate as such ice advances before the glgm in the southernmost part of the patagonian ice sheet are likely to indicate a wider climatic forcing at this time

late quaternary palaeoenvironmental change in western staaten island 54 5 s 64 w fuegian archipelago abstract late glacial holocene environmental conditions were interpreted in western isla de los estados staaten island from geomorphological and palynological analysis the geomorphological data from caleta lacroix 54 50 s 64 40 w indicate the presence of a fossil dune field that suggest exposition of a larger land surface and stronger wind intensity predominantly from sw and w probably during late glacial times when sea level was lower than today deglaciation and onset of peat formation in the western coastal area began prior to 12 600 cal bp in response to warmer conditions the pollen data indicates initial treeless herbaceous and paludal vegetation with scarce empetrum ericaceae type heaths and scrubs as a result of plant invasion and short term succession vegetal communities spreading over the shoreline areas under locally more humid conditions the vegetation between 10 300 and 8300 cal bp included dwarf shrub heaths scrubs cushion plants and grasses with scattered trees under warmer and drier climate conditions than today after 8300 cal bp more humid conditions allowed the expansion of an open nothofagus forest associated with dwarf shrub heath communities it was followed at 6700 cal bp by a gradual closed forest development in association with drimys winteri and shrub and herb vegetation indicative of subantarctic evergreen forest magellanic moorland vegetation transition under cold and wet conditions after 5500 cal bp the rate of evergreen beech forest greatly increased with the development of almost pure subantarctic evergreen forest communities these vegetation changes accompanied a modification of the climate toward colder and wetter conditions after 2700 cal bp the closed forest was replaced by an open nothofagus forest indicative of warm and dry conditions the minimum of nothofagus pollen registered between 1000 and 500 cal bp may correspond to the medieval climate anomaly mca period all these vegetation changes are in turn related to the positioning and intensity of the southern westerlies wind belt sea ice antarctic extent and changes in the sea level

millennium scale volcanic impact on a superhumid and pristine ecosystem ecosystems damaged by distal volcanic ash and sulfur deposition usually recover within decades however sediment stalagmite and pollen records from the southernmost andes indicate a 2000 yr impact on forest and aquatic ecosystems after deposition of a thin tephra layer so 2 released from altering pumice produced intense soil and lake acidification in a 150 000 km 2 area acidification led to nutrient leaching and affected soil microorganisms causing plant decay and increased soil erosion in an area larger than 8000 km 2 we conclude that weakly buffered soils in humid environments are extremely vulnerable to volcanic and anthropogenic acidification causing long lasting ecosystem damage and perturbations of paleoclimate proxy records

climatic controls of holocene fire patterns in southern south america holocene fire climate vegetation linkages are mostly understood at individual sites by comparing charcoal and pollen records with other paleoenvironmental proxy and model simulations this scale of reconstruction often obscures detection of large scale patterns in past fire activity that are related to changes in regional climate and vegetation a network of 31 charcoal records from southern south america was examined to assess fire history along a transect from subtropic to subantarctic biomes the charcoal data indicate that fire activity was greater than present at ca 12 000 cal yr bp and increased further and was widespread at 9500 cal yr bp fire activity decreased and became more spatially variable by 6000 cal yr bp and this trend continued to present atmospheric circulation anomalies during recent high fire years show a southward shift in westerlies and paleoclimate model simulations and data syntheses suggest that such conditions may have prevailed for millennia in the early holocene when the pole to equator temperature gradients were weaker and annual temperatures were higher than present in response to orbital time scale insolation changes

a geometric model to estimate slip rates from terrace rotation above an offshore listric thrust fault kaikōura new zealand abstract the kaik ura peninsula lies at the transition from subduction to continental collision at the southern end of the hikurangi subduction system this study uses a 2012 lidar survey over the kaik ura peninsula to re map a flight of four uplifted late pleistocene marine terraces at high resolution the lidar shows that the terraces are being progressively tilted landwards in a manner consistent with listric thrust faulting offshore the fault known as the kaik ura peninsula fault dips shallowly at c 30 to the northwest at depth and probably truncates the seaward segment of the hope fault in the footwall of the jordan thrust geometric analysis of the tilt using ages based on previous dating and a regional sea level curve suggests that slip rates on the kaik ura peninsula fault have ranged between 2 3 1 5 mm yr and 4 1 1 3 mm yr over the late pleistocene the elevations of late holocene fringing beaches track regional sea level changes apart from a departure indicating a single uplift event penultimate earthquake in the late 18th to earliest 19th century 1702 1838 ce followed by uplift in the 2016 kaik ura earthquake the slip rate calculated from beach uplift including the kaik ura earthquake is consistent with longer term rates the accumulation of the slip over only c 220 years following 2000 years of quiescence suggests that the offshore thrust and associated faults exhibit clustered behavior possibly as a result of keystone faulting

palaeoenvironmental change in southern patagonia during the lateglacial and holocene implications for forest refugia and climate reconstructions abstract a high resolution palynological record from punta yartou fuego patagonia 53 51 s 70 08 w supported by lithostratigraphy radiocarbon dating and tephrochronology was examined to reconstruct the vegetation changes during the last glacial interglacial transition and the holocene following deglaciation from the last glacial maximum sometime before c 23 070 cal yr bp the vegetation was initially dominated by ericaceous shrubs and following modest climate amelioration between c 20 480 and 14 820 cal yr bp the environment favoured the spread of acaena the trend to a warmer and more humid climate was interrupted between c 14 820 and 13 560 cal yr bp when the vegetation community was dominated by cold tolerant herbs such as poaceae and asteraceae subfamily asteroideae suggesting an open treeless landscape with colder climatic conditions coeval with the antarctic cold reversal after c 13 560 cal yr bp a gradual rise in temperature and humidity is inferred from the colonisation of nothofagus a further warming and increase is inferred from the establishment of the forest steppe ecotone by c 12 900 cal yr bp the early holocene was then characterised by increasing development of nothofagus open canopy forest however between c 8080 and 5060 cal yr bp there was a significant reduction in the forest cover and high values of charcoal which suggest an intense arid phase leading to increased availability of dry fuel between c 5060 and 2170 cal yr bp there were centennial scale periods of increased wetter and colder climatic conditions the punta yartou record demonstrates the sensitivity of fuego patagonian forest to changes in the proximity and intensity of the southern westerly winds

late glacial and holocene climate variability southernmost patagonia abstract a late glacial holocene palaeoecological record constrained by a robust chronology from a peat bog near punta burslem 54 54 s 67 57 w on isla navarino southernmost patagonia documents the shifts in intensity and focus of the southern westerly winds swws at these high latitudes such long term records are required to reconstruct and better understand the likely regional impacts of a poleward shift and intensification of the swws predicted under global warming scenarios deglaciation at punta burslem occurs sometime before c 17 000 cal a bp and the post glacial landscape is dominated by cold tolerant pioneer species nothofagus woodland is established by c 12 250 cal a bp this moisture sensitive vegetation type retreats in the early to mid holocene from c 9700 to 7050 cal a bp reflecting an intense and sustained drier phase associated with a prolonged poleward contraction of the swws after c 6000 cal a bp there is a regional trend to cooler and wetter climate however we identify at least five periods of rapid climate change rcc leading to drier conditions at this southern extreme of patagonia c 5350 4750 cal a bp c 4300 3300 cal a bp c 2600 1850 cal a bp c 1350 1100 cal a bp and c 550 350 cal a bp from a synthesis of our isla navarino records and a latitudinal spread 34 64 s of multiproxy records it is proposed that these periods of rcc and relatively drier conditions indicate latitudinal shifts in the location and intensity of the swws in response to climatic warming leading to reduced precipitation at the southern margins of patagonia

tephra geochemistry a discussion of some persistent analytical problems distal tephrochronological studies are reliant upon precise and accurate geochemical quantitation this quantitation can involve difficulties not often encountered in more conventional petrology solving these problems is of particular importance in the holocene and late quaternary of northwest europe where numerous tephra layers of icelandic origin have been detected in peat bogs and lake and marine sediments electron probe microanalysis epma has proved the most applicable analytical technique when insufficient quantities of tephra are available for bulk analysis standard epma techniques require fine tuning to the tephra problem as the geochemical instability of glass is a common feature in many previous studies geochemical data of avoidably low quality have been produced and little attention appears to have been directed to modification of epma methods it is suggested that the black box approach to geochemical analysis should be avoided by the consideration of several factors these include

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

deglacial palaeoclimate at puerto del hambre subantarctic patagonia chile the primary objective of this study is to further substantiate multistep climatic forcing of late glacial vegetation in southern south america a secondary objective is to establish the age of deglaciation in estrecho de magallanes bahia inutil pollen assemblages at 2 cm intervals in a core of the mire at puerto del hambre 53 36 21 s 70 55 53 w provide the basis for reconstructing the vegetation and a detailed account of palaeoclimate in subantarctic patagonia chronology over the 262 cm length of core is regulated by 20 ams radiocarbon dates between 14 455 and 10 089 14c yr bp of 13 pollen assemblage zones the earliest representing the oldest dryas chronozone 14 455 13 000 14c yr bp records impoverished steppe with decreasing frequencies and loss of southern beech nothofagus successive 100 yr long episodes of grass herbs and of heath empetrum ericaceae before 14 000 14c yr bp infer deglacial successional communities under a climate of increased continentality prior to the establishment of grass dominated steppe the bolling allerod 13 000 11 000 14c yr bp is characterised by mesic grassland under moderating climate that with abrupt change to heath dominance after 12 000 14c yr bp was warmer and not as humid at the time of the younger dryas 11 000 10 000 14c yr bp grass steppe expanded with a return of colder more humid climate later with gradual warming communities were invaded by southern beech the puerto del hambre record parallels multistep deglacial palaeoclimatic sequences reported elsewhere in the southern andes and at taylor dome in antarctica deglaciation of estrecho de magallanes bahia inutil is dated close to 14 455 14c yr bp invalidating earlier dates of between 15 800 and 16 590 14c yr bp copyright 2000 john wiley sons ltd

deglacial holocene environmental changes at the pacific entrance of the strait of magellan abstract we show environmental and nitrogen cycle changes between 13 and 2 5 kyr bp from the latest deglaciation to the holocene based on biogeochemical records in a sediment core from the pacific entrance of the strait of magellan organic carbon total nitrogen and c 37 alkenone contents were low during 13 9 kyr bp but increased rapidly at 8 kyr bp the relative contribution of tetra unsaturated c 37 alkenone used as a salinity proxy suggests low salinity during 13 9 kyr bp changing to high salinity at 8 kyr bp planktic foraminifer data showed that globigerina bulloides was more abundant during the deglacial early holocene than in the mid late holocene whereas abundances of neogloboquadrina pachyderma showed the opposite pattern this evidence plus biogenic opal data suggest that sea level rose surface waters were relatively stratified and in situ productivity was low except for organisms with opal tests from 13 to 9 kyr bp bulk 15 n values were high 9 11 relative to present day values during the deglacial early holocene with consistently lower values 7 after 8 kyr bp these relatively high 15 n values most likely reflect increased nutrient utilization in the southern ocean which resulted in high 15 n water being advected to the patagonian fjords although local denitrification caused by the delivery of copious terrestrial materials and organic matter to the ocean cannot be ruled out by 8 kyr bp continental influences and surface stratification were reduced and characteristic holocene conditions were established with increased influence of southern ocean water in the western strait of magellan sea surface temperatures showed millennial scale changes during the deglaciation and early holocene with relatively warm temperatures 11 12 c corresponding to the antarctic counterpart of the younger dryas cooling event of the northern hemisphere the longer term pattern 10 kyr time scale in alkenone derived sea surface temperatures generally follows orbital changes in insolation during austral spring suggesting a controlling influence of austral spring insolation on southern patagonian climate

middle late holocene palynology and marine mollusks from archipielago cormoranes area beagle channel southern tierra del fuego argentina abstract the palynology and marine mollusks of a marine sequence from rio ovando 54 51 s 68 35 w archipielago cormoranes beagle channel has been studied in order to reconstruct paleoenvironmental conditions during the middle late holocene the dinoflagellate cyst assemblages from rio ovando sequence reflect fjord estuarine environments close to terrestrial ice field affected by glacier meltwater discharge and characterized by short term oscillations of sea surface water parameters the base of the section which is dated at about ca 4160 14 c yr b p 4736 cal yr b p palynological subzone ro 2c is characterized by a high species diversity of dinocyst and mollusks and it is immediately followed by an interval palynological subzone ro 2b characterized by the presence of the echinidinium islandinium complex and the monospecific mytilus mollusk assemblage this subzone registers an inverse correlation between nothofagus dombeyi type and echinidinium islandinium complex concentration values during ca 4160 14 c yr b p 4736 cal yr b p 4064 14 c yr b p 4540 cal yr b p suggesting a variable climatic condition probably related to neoglacial episodes occurred in the southern patagonia andes during this interval the pollen assemblages permit direct correlations with the onshore palynostratigraphy from southern of tierra del fuego the high percentages of nothofagus dombeyi type recorded throughout most of the profile strongly suggest the presence of a closed forest confirming the existence of a variable cool and wet climate for the archipielago cormoranes area during the middle late holocene

the vulnerability of the nothofagus forest steppe ecotone to climate change palaeoecological evidence from tierra del fuego 53 s abstract a new late glacial holocene palaeoenvironmental record from near lago lynch 53 54 s 69 26 w tierra del fuego is presented the record was sampled from a mire located within the deciduous nothofagus forest steppe ecotone and pollen and spore analysis suggest a high degree of vulnerability of past vegetation to changes in effective moisture ams radiocarbon dating supplemented by the application of tephrochronology including the geochemical fingerprinting of six visible and cryptotephra layers provides robust age constraint the lago lynch record commences at c 15 6 ka the sequence of vegetation changes between c 15 6 and 14 4 ka reflect a gradual increase in temperature and humidity followed by a colder interval between c 14 4 and 13 3 ka which is broadly coeval with the antarctic cold reversal after c 13 3 ka patches of nothofagus forest appeared suggesting more mesic temperate conditions leading gradually to the establishment of an open canopy nothofagus forest by c 12 5 ka which marks the start of the holocene moderate to strong effective moisture levels dominated during the early holocene until c 11 0 ka followed by a sustained period c 11 0 6 5 ka of drier climatic conditions particularly two arid phases at c 10 5 10 0 ka and 8 5 6 5 ka an eastwards expansion of the forest margin after c 6 5 ka at the site suggests a return to more humid conditions during the late holocene we argue that the periods of increased moisture and aridity inferred from lago lynch closely reflect the extent to which the southern westerly winds swws push eastwards to the drier regions of fuego patagonia during the holocene the longitudinal variations in moisture are driven by the nature and timing of latitudinal shifts in the swws more significantly the vulnerability of the forest steppe ecotone to moisture changes amplifies the ecological impact of relatively small scale shifts in the swws

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

late and postglacial vegetation and fire history in southern patagonia and tierra del fuego abstract two 17 000 yr old peat bog records from low elevation sites in tierra del fuego harberton 54 54 s and southern patagonia rio rubens 52 4 48 s and one c 14 000 cal yr bp record from the upper treeline in tierra del fuego paso garibaldi 54 43 s were analyzed for pollen charcoal and plant macrofossils to reconstruct changes in regional and local vegetation fire frequency and bog hydrology respectively past environmental changes in both lowland records and in the upper treeline record are interpreted in terms of variations in effective moisture during the late glacial period effective moisture changes at both low and high elevation sites were interpreted from comparable shifts between mesic herb rich grasslands and arid empetrum heath or shrub grassland with abundant disturbance indicators the late glacial effective moisture changes were primarily driven by temperature changes during the early holocene expansion of open nothofagus woodlands in the lowlands in present day areas of dense forest was related to a marked precipitation increase however precipitation must have remained highly variable with century long periods of increased summer drought as evidenced by repeated intervals when bogs dried out and fire frequency was high up slope shifts of the nothofagus forest andean tundra ecotone at 11 000 and 9000 cal yr bp also appear to reflect precipitation increases precipitation variability however must not have affected the upper treeline environments as no fires were recorded and the present day nothofagus forest had become established after 9000 cal yr bp upper treeline apparently was below present from 8000 to 7000 and 2500 to c 400 cal yr bp during those times low elevation environments did not register change which suggests that the upper treeline may have been affected by lower temperatures after c 5000 cal yr bp fires became rare in the lowlands suggesting a shift to an equable precipitation regime with only minor intervals of summer drought no simultaneous change was recorded at the upper treeline thus for the late glacial and early holocene the upper and lower treeline environments apparently responded similarly to primarily moisture changes only during the mid and late holocene environmental changes at high and low elevations differed suggesting responses to different climate signals precipitation in the lowlands and temperature at high elevation

consistent dating for antarctic and greenland ice cores we are hereby presenting a new dating method based on inverse techniques which aims at calculating consistent gas and ice chronologies for several ice cores the proposed method yields new dating scenarios simultaneously for several cores by making a compromise between the chronological information brought by glaciological modeling i e ice flow model firn densification model accumulation rate model and by gas and ice stratigraphic constraints this method enables us to gather widespread chronological information and to use regional or global markers i e methane volcanic sulfate beryllium 10 tephra layers etc to link the core chronologies stratigraphically confidence intervals of the new dating scenarios can be calculated thanks to the probabilistic formulation of the new method which takes into account both modeling and data uncertainties we apply this method simultaneously to one greenland ngrip and three antarctic epica dome c epica dronning maud land and vostok ices cores and refine existent chronologies our results show that consistent ice and gas chronologies can be derived for depth intervals that are well constrained by relevant glaciological data in particular we propose new and consistent dating of the last deglaciation for greenland and antarctic ice and gas records

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

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

large scale control on the patagonian climate abstractpatagonia located in southern south america is a vast and remote region holding a rich variety of past environmental records but a small number of meteorological stations precipitation over this region is mostly produced by disturbances embedded in the westerly flow and is strongly modified by the austral andes uplift on the windward side leads to hyperhumid conditions along the pacific coast and the western slope of the andes in contrast downslope subsidence dries the eastern plains leading to arid highly evaporative conditions the authors investigate the dependence of patagonia s local climate precipitation and near surface air temperature year to year variability on large scale circulation anomalies using results from a 30 yr long high resolution numerical simulation variations of the low level zonal wind account for a large fraction of the rainfall variability at synoptic and interannual time scales zonal wind also controls the amplitude of the air temperature annual cycle by changi