Search

Alpine glaciers are sensitive indicators of changes in climate, and their ubiquity in mountainous regions make them valuable proxies for terrestrial climate reconstructions worldwide. However, the timing and extent of glacier change across the South American mid-latitudes through the Holocene are still poorly constrained relative to their counterparts in the Northern Hemisphere. Here we report a new 10Be surface exposure-based chronology of moraines recording a series of progressively less-extensive glacier advances of Glaciar Torre (Argentina, 49.3°S/73.0°W) since the Last Glacial Maximum, with expansions culminating at 17,600 ± 900, 13,500 ± 500, 9700 ± 400, 6900 ± 200, 6100 ± 300, 4500 ± 200, and 530 ± 60 yr BP. The declining magnitude of Holocene glacier expansions parallels a gradual rise in local summer insolation intensity during the Holocene, while individual advances occurred during inferred negative Southern Annular Mode (SAM)-like states at centennial to millennial timescales. These observations suggest that (i) summer insolation intensity modulated antiphased trends in glacier extent in the polar hemispheres during the Holocene, and that (ii) centennial-scale ‘SAM-like’ temperature and precipitation anomalies paced glacier fluctuations throughout Patagonia. Given the persistence of the inferred ’SAM-like’ anomalies throughout the Holocene, the modern measured trend towards positive SAM index conditions could mark the onset of a fundamental shift in the climate of the Southern Hemisphere midlatitudes that warrants consideration in projections of future climate.

The history and dynamics of deciduous Nothofagus forests along the eastern slopes of the central Patagonian Andes (44°-49°S) remain insufficiently studied and understood, particularly at timescales ranging from centuries to millennia. Available fossil pollen records point to time-transgressive responses of the arboreal vegetation to climatic changes during the Last Glacial Termination (T1) and early Holocene, and spatial heterogeneity since then along north-south, east-west, and elevation transects. The degree to which these results represent biogeographic and climatic trends, varying environmental gradients, or site-specific phenomena has not been assessed in detail. Here we present a fossil pollen and macroscopic charcoal record from Lago Churrasco (45°41′S, 71°49′W), a small closed-basin lake located in the deciduous Nothofagus forest zone of the central-east Andes of Chilean Patagonia. Our results suggest that Nothofagus trees colonized newly deglaciated terrains at ∼16,000 cal yr BP and formed scrublands/woodlands several millennia earlier than reported by previous studies east of the Andes. This suggests expansion and local densification of tree populations sourced from the eastern margin of the Patagonian Ice Sheet during the Last Glacial Maximum, with the additional implication that temperature and precipitation conditions favorable for tree survival and reproduction developed early during T1. We posit that the amount of moisture delivered by the Southern Westerly Winds was not a limiting factor for arboreal expansion during T1 in this sector of the central Patagonian Andes. Closed-canopy Nothofagus forests established at ∼10,000 cal yr BP and have remained essentially invariant despite climate change and natural disturbance regimes. This resilience was challenged and exceeded by human disturbance during the 20th century through the use of fire, leading to deforestation and spread of invasive exotic species in an extraordinarily rapid event. Our record suggests a permanent influence of the Southern Westerly Winds over the last 10,000 years, with relatively modest variations at centennial and millennial timescales. Fil: Moreno, P. I.. Universidad de Chile; Chile Fil: Simi, E.. Universidad de Chile; Chile Fil: Villa Martínez, R. P.. Universidad de Magallanes; Chile Fil: Vilanova, Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina

This paper reviews current understanding of deglaciation in North, Central and South America from the Last Glacial Maximum to the beginning of the Holocene. Together with paleoclimatic and paleoceanographic data, we compare and contrast the pace of deglaciation and the response of glaciers to major climate events. During the Global Last Glacial Maximum (GLGM, 26.5-19 ka), average temperatures decreased 4° to 8°C in the Americas, but precipitation varied strongly throughout this large region. Many glaciers in North and Central America achieved their maximum extent during the GLGM, whereas others advanced even farther during the subsequent Heinrich Stadial 1 (HS-1). Glaciers in the Andes also expanded during the GLGM, but that advance was not the largest, except on Tierra del Fuego. HS-1 (17.5-14.6 ka) was a time of general glacier thickening and advance throughout most of North and Central America, and in the tropical Andes; however, glaciers in the temperate and subpolar Andes thinned and retreated during this period. During the Bølling-Allerød interstadial (B-A, 14.6-12.9 ka), glaciers retreated throughout North and Central America and, in some cases, completely disappeared. Many glaciers advanced during the Antarctic Cold Reversal (ACR, 14.6-12.9 ka) in the tropical Andes and Patagonia. There were small advances of glaciers in North America, Central America and in northern South America (Venezuela) during the Younger Dryas (12.9-11.7 ka), but glaciers in central and southern South America retreated during this period, except on the Altiplano where advances were driven by an increase in precipitation. Taken together, we suggest that there was a climate compensation effect, or ‘seesaw’, between the hemispheres, which affected not only marine currents and atmospheric circulation, but also the behavior of glaciers. This seesaw is consistent with the opposing behavior of many glaciers in the Northern and Southern Hemispheres.

We present a high-resolution precisely dated terrestrial paleovegetation/paleoclimate record from Lago Pichilaguna, northwestern Patagonia (40°–44°S), which spans continuously from the Last Glacial Maximum (LGM) to the present. We find abundant and continuous presence of arboreal pollen (chiefly Nothofagus) during the LGM, accompanied by other trees, shrubs, and alpine herbs. These results suggest Subantarctic parkland and/or scattered woodlands under a cold and hyperhumid climate during the LGM (∼25,000–17,800 cal. yr BP) with expansion of Nothofagus under relatively warm interstadial conditions between 25,000 and 19,200 cal. yr BP. This was followed by cooling and a precipitation increase between 19,200 and 17,800 cal. yr BP, which was contemporaneous with the youngest LGM advance of Andean glaciers in the region and maximum influence of the Southern Westerly Wind (SWW). The Last Glacial Termination (T1) started at 17,800 cal. yr BP and featured the spread of thermophilous trees and ferns characteristic of North Patagonian rainforests, along with lake level lowering. These results suggest a warm pulse and southward shift of the SWW, concurrent with a rapid collapse of Andean glacier lobes. Subsequent changes led to the establishment of closed-canopy rainforests under peak interstadial warmth between ∼16,000 and 15,000 cal. yr BP. We detect a shift to cold/wet conditions during the Antarctic Cold Reversal (14,800–12,700 cal. yr BP) and a precipitation decline during Younger Dryas time, followed by maximum temperature, relatively lower lake level and minimum SWW influence between 11,300 and 7700 cal. yr BP. Precipitation then rose punctuated by centennial-scale variations since 6200 cal. yr BP. Chilean-European deforestation and spread of invasive exotic species started at ∼350 cal. yr BP aided by fire. We conclude that temperate rainforests have persisted with little interruption since T1, with major changes in floristic composition driven by climate change and fires. Rainforest composition and heterogeneity declined in response to Chilean/European disturbance during the 1600s and intensified since the 1800s. These events constitute the fastest/largest-magnitude vegetation changes of the last ∼25,000 years.

South Westland, New Zealand, and southern Chile, are two narrow continental corridors effectively confined between the Pacific Ocean in the west and high mountain ranges in the east which impart significant influence over regional climate, vegetation and soils. In both these southern mid-latitude regions, evidence for extensive and repeated glaciations during cold phases of the Quaternary is manifested by arrays of successively older glacial drift deposits with corresponding outwash plain remnants. In South Westland, these variably aged glacial landforms are mantled by layered (multisequal) soils characterised by slow loess accretion and pedogenesis in an extreme leaching and weathering environment. These cover-bed successions have undergone repeated coupled phases of topdown and upbuilding soil formation that have been related to fluctuating cycles of interglacial/warm and glacial/cold climate during the Quaternary. In this study, we recognise multisequal soils overlying glacial landforms in southern continental Chile but, unlike the spodic (podzolic) soil sequences of South Westland, these are of dominantly volcanigenic (andic) provenance and are very similar to multisequal soils of andic provenance that predominate in, and adjacent to, areas of rhyolitic to andesitic volcanism in North Island, New Zealand. Here we develop a soil-stratigraphic model to explain the observed occurrence of multisequal soils mantling dominantly glacial landforms of southern continental Chile. Based on proxy data from southern Chile, we propose that persistent vegetation cover and high precipitation on the western side of the Andes, during colder-than-present episodes tended to suppress the widespread production of glacially-derived loessial materials despite the pervasive occurrence of glacial and glacio-fluvial deposits that have frequently inundated large tracts of this landscape during the Quaternary. Given the lack of loess cover-beds that have traditionally assisted in the relative dating of glacial episodes prior to the Late Quaternary, surface exposure dating techniques could provide another chronological alternative to address this issue. However, there have been two main obstacles to successfully apply this dating technique in Patagonia. First, minimum exposure ages may be obtained on moraines older than the last glacial cycle due to erosion, although dating outwash plains is more robust. Second, on the wet western side adjacent to the Andes, persistent vegetation cover during both glacial and post-glacial times, as well as widespread inundation by volcanic mass-flows, appear preventive. We make a case that soil genesis within this region appears to be dominated by a constant flux of intermittently erupted Andean-sourced tephra which has continued to upbuild soils at the ground surface separated by intervals where topdown weathering processes are intensified. As already demonstrated by New Zealand studies, multisequal soil successions have a clear implied connection to coupled glacial and interglacial climate cycles of the Quaternary. On this basis, similar sequences in northwest Patagonia provide a relatively untapped archive to enable Quaternary glacial and environmental changes in this pervasively glaciated volcanic region to be constructed.

Iniciativa Cientifica Milenio NC120066 FONDECYT 11121280 1160488 1151469 CONICYT USA 2013-0035 NSF-BCS 1263474 Fulbright

The anatomy of the Last Glacial Termination (T1) in the southern mid-latitudes, and its relationship with changes in the Southern Westerly Winds (SWW), offers empirical constraints for understanding the mechanisms involved in the transition from the Last Glacial Maximum into the current interglacial. Northwestern Patagonia (40°-44°S) is a sensitive region for monitoring past changes in the SWW, the Patagonian Ice Sheet, terrestrial ecosystems, and fire regimes through T1. Here we present results from Lago Fonk (∼40°S) to examine the structure of T1 based on the palynological, macroscopic charcoal, elemental, and isotopic composition of organic lake sediments. We observe an instantaneous establishment of Nothofagus-dominated forests at the onset of T1, followed by a diversification and densification trend that culminated with the establishment of thermophilous, Myrtaceae-dominated North Patagonian rainforests between ∼15.6–14.7 cal ka BP. The expansion of the conifer Podocarpus nubigena marks a shift to cool-temperate and hyperhumid conditions, coeval with high lake levels and enhanced algal productivity between ∼14.7–11.9 cal ka BP. Stand-replacing fires, driven by enhanced seasonality or high-frequency rainfall variability, started at ∼12.4 cal ka BP and catalyzed the rapid spread of Weinmannia trichosperma. Subsequent warming and a decline in precipitation at ∼11.4 cal ka BP led to intense fire activity, lake-level lowering, and establishment of the Valdivian rainforest trees Eucryphia/Caldcluvia. Our results suggest a coherent linkage between changes documented in the amphi south Pacific region and Antarctic ice cores during T1. This implies a zonal and hemispheric response to changes in the position/intensity of the SWW that emphasizes their central role as a key driver of the hemispheric and global climate evolution through T1.

Resolving the history of vegetation, fire, and glaciation on the eastern slope of the central Patagonian Andes (44°-49°S) since the Last Glacial Termination (T1) has proved difficult. This is due to the steep environmental gradients, vegetation heterogeneity, and scarcity of dated glacial deposits and geomorphic features. Unsurprisingly, published records show important heterogeneities which limit our understanding of the timing and magnitude of climate and vegetation changes, and their driving mechanisms since T1. In this paper, we describe sediment cores from small closed-basin lakes located in the deciduous Nothofagus forest zone near Coyhaique, Chile. Our results indicate that the Coyhaique glacier lobe abandoned its final Last Glacial Maximum position just before ~17.9 cal kyr BP and underwent a step-wise recession that included a halt/readvance that culminated at ~16.8 cal kyr BP, contemporaneous with the formation of an ice-dammed proglacial lake in the Coyhaique/Balmaceda sector. This glacial lake stood at its highest level between ~17.9–17.2 cal kyr BP ( 650 m.a.s.l.), lowered between ~17.2–16.2 cal kyr BP ( 570 m.a.s.l.), and disappeared thereafter. Herbs and shrubs, currently dominant in high Andean and Patagonian steppe environments, colonized the ice-free terrains distal to the glacier margins and proglacial lakes under cold and dry conditions. This was followed by a steady increase in Nothofagus between ~16.6–14.8 cal kyr BP that led to the establishment of forests starting at ~14.8 cal kyr BP. The Holocene started with a sudden increase in Nothofagus and disappearance of conifers in the context of increase fire activity between ~11.7–9.4 cal kyr BP. Closed-canopy Nothofagus forests persisted virtually unaltered from ~9.4 cal kyr BP to the present day, despite frequent explosive volcanism and millennial-scale variations in fire regimes, attesting to their extraordinary postglacial resilience which contrasts with their behavior during T1. Recent large-scale deforestation by fire, livestock grazing, and the spread of non-native invasive plant species drove the fastest and largest-magnitude shifts seen during the last ~16,500 years.

We describe the stratigraphy, age and correlation of a prominent tephra marker, named Lepue Tephra, extensively distributed in north-western Patagonia. Lepue Tephra is well dated at c. 11 000 cal a BP from numerous lake and soil cover-bed sequences and its recognition is useful for assessing the rate and timing of deglaciation as well as associated environmental changes in this region during the last glacial termination and early Holocene. Lepue Tephra has attributes typical of a complex and compositionally zoned phreatomagmatic eruptive. While the initial rhyolitic phase can be readily distinguished from multiple eruptive products sourced from the adjacent Volcan Chaiten, the main erupted end member is of basaltic–andesitic bulk composition − similar to younger tephras sourced from Holocene monogenetic cones adjacent to the Volcan Michimahuida massif (tMim). Lepue Tephra can be correlated to an equivalent-aged pyroclastic flow deposit (Amarillo Ignimbrite) prominently distributed in the south-eastern sector of tMim. The source vent for these co-eruptive events is obscured by an extensive ice field and is currently unknown. The widespread radially symmetrical distribution of Lepue Tephra centred on tMim cannot be attributed solely to volcanological considerations. Reduced Southern Hemisphere westerly wind influence interpreted from climate proxies at the time of eruption are also implicated.

Southern South America is the only continental landmass that intersects the core of the Southern Westerly Winds (SWW), and thus is important for studying their role as a driver/conduit for the initiation/propagation of climate signals since the last glaciation. Their interaction with the Southern Ocean (SO) affects global climate through its influence on high-latitude upwelling and biological productivity, deep-water convection sites and, consequently, ventilation of CO2 from the deep ocean. Variations in the SWW-SO coupled system have been postulated as fundamental drivers of climate change during glacial terminations and the current interglacial. Hence, deciphering the evolution of the SWW from sensitive locations in the southern middle latitudes is essential for understanding important climatic transitions during and since the Last Glacial Termination (T1). Terrestrial records from the central Patagonian Andes (CPA) (44°-49°S), however, show heterogeneities in the timing, rates, and direction of climate change during T1, impeding detailed assessment of its drivers at regional, hemispheric, and global scales. Here we present new data on glacier, vegetation, and fire-regime changes in the Coyhaique sector (45°34′S) of CPA to improve our understanding on the timing and structure of the T1, including the behavior of the SWW. Our results indicate glacial recession from the youngest Last Glacial Maximum moraines just before ∼17.9 ka and development of an ice-dammed proglacial lake during the early stages of T1. Drainage of the ice-dammed lake, triggered by renewed glacial recession, was near-synchronous with the onset of a gradual multi-millennial trend toward arboreal dominance that started at ∼16 ka east and west of the Andes at that latitude. We detect increased influence of the SWW at ∼45°S starting at ∼16.6 ka, relative to the first millennium of T1, that led to positive anomalies in precipitation between ∼16–14.4 and ∼12.8–11.5 ka, followed by negative anomalies between ∼11.5–9 ka. The synchronous spread of arboreal vegetation east and west of the CPA divide during T1, despite the trans-Andean precipitation contrasts, suggests an upward shift in the temperature-controlled Andean tree line, underscoring the role of deglacial warming as the critical driver for afforestation at regional scale. Fil: Vilanova, Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Moreno, P. I.. Universidad de Chile; Chile Fil: Miranda, C. G.. Universidad de Chile; Chile Fil: Villa Martínez, R. P.. Universidad de Magallanes; Chile

The deep-time dynamics of coupled socio-ecological systems at different spatial scales is viewed as a key framework to understand trends and mechanisms that have led to the Anthropocene. By integrating archeological and paleoenvironmental records, we test the hypothesis that Chilean societies progressively escalated their capacity to shape national biophysical systems as socio-cultural complexity and pressures on natural resources increased over the last three millennia. We demonstrate that Pre-Columbian societies intentionally transformed Chile’s northern and central regions by continuously adjusting socio-cultural practices and/or incorporating technologies that guaranteed resource access and social wealth. The fact that past human activities led to cumulative impacts on diverse biophysical processes, not only contradicts the notion of pristine pre-Industrial Revolution landscapes, but suggests that the Anthropocene derives from long-term processes that have operated uninterruptedly since Pre-Columbian times. Moreover, our synthesis suggests that most of present-day symptoms that describe the Anthropocene are rooted in pre-Columbian processes that scaled up in intensity over the last 3000 years, accelerating after the Spanish colonization and, more intensely, in recent decades. The most striking trend is the observed coevolution between the intensity of metallurgy and heavy-metal anthropogenic emissions. This entails that the Anthropocene cannot be viewed as a universal imprint of human actions that has arisen as an exclusive consequence of modern industrial societies. In the Chilean case, this phenomenon is intrinsically tied to historically and geographically diverse configurations in society-environment feedback relationships. Taken collectively with other case studies, the patterns revealed here could contribute to the discussion about how the Anthropocene is defined globally, in terms of chronology, stratigraphic markers and attributes. Furthermore, this deep-time narrative can potentially become a science-based instrument to shape better-informed discourses about the socio-environmental history in Chile. More importantly, however, this research provides crucial “baselines” to delineate safe operating spaces for future socio-ecological systems.

Robust glacial chronologies are needed to address the fundamental questions of when and why Ice Age climates begin and end. Well-preserved glacial deposits left by large ice sheet lobes adjacent to Estrecho de Magallanes (53°S; Chile) in southernmost South America provide a unique opportunity to reconstruct the timing and fine structure of the last two major glaciations, as well as the last termination. We present a new precise 10Be surface exposure dataset of 34 moraine boulders directly tied to a recently published, high resolution glacial geomorphic map of the deposits left by the Magallanes lobe. We find that the southern section of the Patagonian Ice Sheet was more extensive during Marine Isotope Stage 4 (MIS 4) than during MIS 2, representing the first direct dating of the MIS 4 glacier culmination in South America. Similar to the MIS 2 glacial maxima, within MIS 4 there were multiple advances that we date (n = 6 samples) to between 67.5 ± 2.1 and 62.1 ± 2.0 ka. A similarly timed MIS 4 advance was identified in New Zealand, indicating that this is a hemisphere-wide glacier-climate signal, which is further corroborated by South Atlantic and Pacific temperature proxy records. Inboard of the MIS 4 moraine complex, we date a sequence of geomorphically distinct MIS 2 moraines that represent separate major periods of glacial stability. The MIS 2 maximum extent occurred by 27.4 ± 0.8 ka (n = 4; arithmetic mean, with the standard error of the mean and 3% propagated production rate error) and was followed by at least four more full glacial culminations at 25.7 ± 0.8 (n = 3), 23.9 ± 0.8 (n = 5), 19.1 ± 0.7 (n = 3), and 18.1 ± 0.6 ka (n = 3), which represent periods when the glacier was in equilibrium with the climate for long enough to form major moraines. About 18 km inboard, this sequence is followed by smaller-scale recessional moraine crests, deposited on drumlinized terrain rather than a moraine drift, that we date to 18.0 ± 0.8 ka, indicating the glacier was in net retreat at this time. Tentative results from a 2D ice sheet model suggest that the Magallanes lobe may have reached mapped inner and outer MIS 2 moraines from a climate with approximately 4.5 °C and 5.5 °C cooler summers, respectively, assuming ∼25% less annual precipitation, relative to modern climate. We hypothesize that during the last glacial cycle, shifts in the subtropical and subantarctic fronts, and related ocean-atmosphere patterns, explain MIS 4 to 2 glacial behavior in the southern mid-latitudes.

We present results from Lago Negro, a small closed-basin lake adjacent to Lago Rosselot, to examine the vegetation and environmental history of an insufficiently studied sector of Chiloe Continental (41°30′-44°S) in northwestern Patagonia. Lake sediment cores from Lago Negro reveal 27 tephra deposited since ∼12.7 ka, including two prominent rhyodacite tephra marker beds erupted from Volcan Melimoyu, and a stratified basal clastic unit we attribute to meltwater discharge from an ice tongue that originated from Monte Queulat and covered Lago Rosselot during its expanded position, presumably Antarctic Cold Reversal in age. The pollen record shows closed-canopy North Patagonian rainforests since ∼12.7 ka, with variations in species composition and structure that suggest dynamic responses of the vegetation to past environmental changes. Vegetation responses to climate in the Lago Negro record were modulated, sometimes interrupted, by high magnitude and frequent disturbance regimes, most notably during maxima in explosive volcanic activity (∼9.5–7.2 ka and ∼3.6–1.6 ka) and heightened fire activity. Since Lago Negro is the southernmost palynological site so far investigated in the region and is located within a volcanically active sector, it provides a valuable perspective for assessing past vegetation responses along environmental gradients since the last glaciation. When compared with other sites throughout northwestern Patagonia, our record reveals a distinct north-to-south gradient in temperature and precipitation, with peak temperature and rainfall seasonality in the north, and a west-to-east gradient in disturbance regimes, with maximum frequency and magnitude of explosive volcanic events in the east. These gradients have modulated the response of rainforest vegetation to climate forcing at regional scale since ∼12.7 ka. We identify negligible differences in timing for the majority of key vegetation signals during the initial phase of the Lago Negro record, and propose that plant colonization and expansion along the ∼360 km long corridor through the Pacific slope of the northwestern Patagonian Andes was a rapid process during the Last Glacial Termination.

Climate and disturbance regimes play key roles in shaping the structure, composition and functioning of terrestrial ecosystems. Despite this importance, very few stratigraphic studies in the temperate rainforests from northwestern Patagonia have explored this relationship in detail along a time continuum through the entire Holocene. Here we present a high-resolution fossil pollen and charcoal record from Lago Fonk (median resolution: 20 years), a small closed-basin lake in the lowlands of the Chilean Lake District (41°S), where wildfires and explosive volcanism have intermittently taken place during the Holocene, along with pronounced human-induced disturbance in post-colonial time. Our results show persistence of temperate rainforest throughout the Holocene, with changes in the composition and structure of Valdivian rainforests (VRF) at millennial timescales. We detect centennial-scale alternations in dominance between the VRF tree Eucryphia/Caldcluvia and generalist trees found in VRF and North Patagonian rainforests after ∼6.5 cal ka BP. Intervals dominated by VRF coincide with enhanced fire occurrence signaling negative hydroclimate anomalies with a mean duration of ∼150 years, which alternate with positive hydroclimate anomalies lasting ∼312 years on average. Our results suggest that the magnitude and rapidity of vegetation changes detected at 10.2–9.9, 4.0–3.0, ∼1.0, and ∼0.7 cal ka BP were amplified by disturbance regimes, and led to the establishment and maintenance of Eucryphia/Caldcluvia-dominated forests in the Longitudinal Valley of the Chilean Lake District. On several occasions the higher incidence of fire disturbance during warm/dry climate intervals coincided with episodes of heightened explosive volcanic activity from multiple eruptive centers within the Southern Andean Volcanic Zone.

An important coupled ocean-atmospheric system in the mid- and high latitudes involves the Southern Westerly Winds (SWW) and the Southern Ocean (SO), which controls climate in the southernmost third of the world, deep water formation, and ventilation of CO2 from the deep ocean. Most studies have examined its role as a driver of atmospheric CO2 concentrations during glacial terminations, but very few have investigated its influence during the Holocene, i.e. the current interglacial. A fundamental problem, however, is resolving whether the SWW strength increased or declined during the early Holocene (∼11.5–7.5 ka, ka = 1000 cal yr BP) in sectors adjacent to the Drake Passage. Here we assess past changes in SWW influence over the last ∼17,000 years using terrestrial paleoclimate records from southwestern Patagonia (∼52°S). We detect a zonally symmetric Early Holocene Westerly Minimum which diminished wind stress and upwelling on the SO, contributing to a contemporary decline in atmospheric CO2 concentrations and enrichment in the stable carbon isotope ratio of atmospheric CO2 (δ13Catm). Our mid-latitude data also indicate a shift to strong SWW influence at ∼7.5 ka which correlates with a sustained increase in atmospheric CO2 and halt in the δ13Catm rise, suggesting enhancement of high-latitude ocean ventilation by an invigorated SWW-SO coupled system.

We examine hydroclimate changes at centennial/millennial timescales since 16,000 yr BP in northwestern Patagonia based on the pollen and charcoal record from Lago El Salto, a small closed-basin lake located in the Chilean Lake District (41°38′48.02″S, 73° 5′48.42″W). We observe cold/wet conditions between 14,500–16,000 yr BP, followed by further cooling with increased precipitation until 13,000 yr BP, enhanced precipitation seasonality and/or variability between 11,600–13,000 yr BP, and an extended warm-and-dry interval between 7600 and 11,300 yr BP with peak paleofire activity. Colder-and-wetter than present conditions and muted paleofire activity prevail between 5300 and 7600 yr BP, followed by alternating cold/wet and centennial-scale warm/dry phases starting at 5300 yr BP with three conspicuous megadroughts since 2500 yr BP. The most recent megadrought occurred during the Medieval Climate Anomaly. We identify a cold reversal that spans the Antarctic Cold Reversal (ACR) and the Younger Dryas (YD) chrons with stronger-than-present westerly influence during the former and enhanced variability during the latter. These results extend the northern limit of strong cooling and increase in precipitation during the ACR and the southern limit of influence of strong hydrologic variations during the YD in terrestrial environments, suggesting an overlap in the spheres of influence of processes originating from southern and northern polar latitudes. An extended warm southern westerly wind (SWW)-minimum interval is evident between 7600 and 11,300 yr BP, followed by a rapid shift to cool-moist conditions between 5300 and 7600 yr BP brought by a mid-Holocene SWW maximum. Since then we observe centennial-scale hydroclimate variability, which has driven biodiversity and fire-regime shifts of evergreen temperate rainforests.

By virtue of its location in the southern mid-latitudes, northwestern Patagonia (40°-44°S) offers the opportunity to unravel the mechanisms involved in the initiation and propagation of paleoclimate signals of hemispheric and global significance. Of particular importance is deciphering the evolution of the Southern Westerly Winds (SWW) considering their influence at continental, zonal, hemispheric, and global scale. Here I present a multi-decadal record from Lago Proschle, a small closed-basin lake located on the Pacific slope of northwestern Patagonia, to examine the timing and structure of vegetation, fire, and climate change along a continuum since the onset of the Last Glacial Termination (T1). The record shows rapid glacier recession during T1, reaching the western Andean foothills in ∼400 years or less. Nothofagus-dominated forests established between ∼17.4–17 ka, followed by closed-canopy North Patagonian Rain Forests (NPRF) with shade-tolerant thermophilous trees between ∼16.3–15.4 ka. These changes suggest an abrupt warming trend and an increase in precipitation at ∼16.3 ka, associated with a northward shift of the SWW. Subsequent increases in cold-tolerant hygrophilous trees between ∼15.4–12.8 ka imply a shift to cold, more humid conditions during the Antarctic Cold Reversal, suggesting stronger SWW influence. This was followed by stand-replacing fires brought by a sudden decline in summer precipitation at ∼12.8 ka, associated with a millennial-scale southward shift of the SWW which was contemporaneous with the onset of the Younger Dryas. Dominance of thermophilous, summer-drought tolerant Valdivian rainforest trees and high fire activity ensued between ∼10.3–7.8 ka, suggesting peak warmth and overall decline in annual precipitation associated with weakening of the SWW during the early Holocene. A multi-millennial cooling and wetting trend started at ∼7.8 ka, brought by stronger SWW influence, followed by recurrent, centennial-scale variations in temperature and precipitation starting at ∼6.4 ka. Deforestation, fire, and spread of non-native herbs by Chilean/European settlers began during the late 18th century. Abrupt vegetation changes in the Lago Proschle record were driven by rapid climate changes over the last 17,400 years amplified, in some instances, by fire disturbance.

The degree to which vegetation and site type have influenced fire regimes through the Holocene has not been investigated in detail in the temperate ecosystems of southern Patagonia. Here we present a first attempt using a paired-basin approach to study the evolution of fire regimes in sectors dominated by humid Nothofagus forests and the xeric Patagonian steppe in the Magallanes region of Chilean Patagonia (51°S). We analyzed sediment cores from two small lakes and a bog located within the same climate zone on opposite sides of the forest-steppe ecotone, ~28 km apart. The position of this biological boundary east of the Andes is controlled by the strength and position of the southern westerly winds, which constitute the sole source of precipitation throughout western Patagonia. Our results indicate that fires have occurred in the study region repeated times over the last ~13,000 years at bi- and tridecadal timescales. Sectors currently dominated by Patagonian steppe feature high frequency and low magnitude of local fires, and vice versa in humid forests. Climate-driven expansion of Nothofagus scrubland/woodland into steppe environments over the last ~4,200 years increased the magnitude and lowered the frequency of fire events, culminating with peak Nothofagus abundance, fire magnitude and frequency during the last millennium. We also detect divergences between lake-based vs. bog-based paleofire histories among paired sites located within the Patagonian steppe, ~12 km apart, which we attribute to local burning of the bog at times of lowered water table. This divergence suggests to us that bog-based vegetation and fire histories exacerbate a local, azonal, signal blurring extra-local or regional regimes, thus accounting for some discrepancies in the Quaternary paleovegetation/paleoclimate literature of southern Patagonia. Fil: Moreno, Patricio I.. Universidad de Chile; Chile Fil: Vilanova, Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina Fil: Villa Martínez, Rodrigo P.. Universidad de Magallanes; Chile Fil: Francois, Jean P.. Universidad de Playa Ancha; Chile

The Southern Westerly Winds (SWW) are the surface expression of geostrophic winds that encircle the southern mid-latitudes. In conjunction with the Southern Ocean, they establish a coupled system that not only controls climate in the southern third of the world, but is also closely connected to the position of the Intertropical Convergence Zone and CO2 degassing from the deep ocean. Paradoxically, little is known about their behavior since the last ice age and relationships with mid-latitude glacier history and tropical climate variability. Here we present a lake sediment record from Chilean Patagonia (51°S) that reveals fluctuations of the low-level SWW at mid-latitudes, including strong westerlies during the Antarctic Cold Reversal, anomalously low intensity during the early Holocene, which was unfavorable for glacier growth, and strong SWW since ∼7.5 ka. We detect nine positive Southern Annular Mode-like events at centennial timescale since ∼5.8 ka that alternate with cold/wet intervals favorable for glacier expansions (Neoglaciations) in southern Patagonia. The correspondence of key features of mid-latitude atmospheric circulation with shifts in tropical climate since ∼10 ka suggests that coherent climatic shifts in these regions have driven climate change in vast sectors of the Southern Hemisphere at centennial and millennial timescales. Fil: Moreno, P.I.. Universidad de Chile; Chile Fil: Vilanova, Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina Fil: Villa-Martínez, R.. Universidad de Magallanes; Chile Fil: Dunbar, R.B.. University of Stanford; Estados Unidos Fil: Mucciarone, D.A.. University of Stanford; Estados Unidos Fil: Kaplan, M.R.. Columbia University; Estados Unidos Fil: Garreaud, R.D.. Universidad de Chile; Chile Fil: Rojas, M.. Universidad de Chile; Chile Fil: Moy, C.M.. University of Otago; Nueva Zelanda Fil: De Pol-Holz, R.. Universidad de Magallanes; Chile Fil: Lambert, F.. Pontificia Universidad Católica de Chile; Chile

We describe the stratigraphy, age, constituent geochemistry and phenocryst thermobarometry of a closely spaced Holocene tephra couplet from Volcan Melimoyu (VMm), located in the Northern Patagonian Andes. The lower tephra unit (La Junta Tephra, Mm-1) is distinctly banded comprising a dominant lower layer of rhyodacitic (∼70% SiO2) pumiceous ash and lapilli (Mm-1p) that abruptly transitions to a subordinate upper scoriaceous layer (Mm-1s) of basaltic andesite composition (∼53% SiO2). This bimodality within Mm-1 contrasts significantly with the closely overlying Santa Ana Tephra (Mm-2) that has a homogeneous trachyte-dacite (∼63% SiO2) composition and is intermediate between the two magmatic end members of Mm-1. We propose a genetic affiliation between Mm-1 and Mm-2, and that the latter event likely represents a hybridised-remnant of those discrete magmas involved in the earlier Mm-1 eruption. To test this hypothesis we applied whole rock elemental mixing and fractional crystallisation model to reproduce the composition and crystallinity of Mm-2. Results indicate that Mm-2 can be reproduced by mixing ∼70% Mm-1p with ∼30% Mm-1s, with subsequent ∼13% fractional crystallisation of plagioclase, and minor amphibole, orthopyroxene, magnetite and biotite. Equilibrium P-T conditions calculated from Mm-1p phenocrysts point towards magma residency at moderately shallow depths (200–290 MPa, ∼7–10-km depth, 850–1000 °C), whereas Mm-1s phenocrysts indicate higher overall P-T conditions (240–480 MPa, ∼8.5–17-km depth, 1080–1150 °C). P-T conditions determined for Mm-2 (∼290 MPa, ∼10-km depth, 930–1000 °C) are similar to those of Mm-1p. There is no physical and/or geochemical evidence of mafic magma involvement in the Mm-2 eruption. Similar compositionally bimodal tephra are known from other Northern Patagonian Andean centres (i.e. Playas Blanca-Negra Tephra, Antillanca; Lepue Tephra, Michimahuida; Ho and H3 eruptions of Hudson) suggests that the intrusion of mafic magma into more silicic magma bodies is a common occurrence throughout this Andean sector. These widely dispersed, compositionally bimodal tephra not only provide key insights into pre-eruptive magmatic conditions and triggering processes, but can also be readily identified geochemically, and thereby be more fully utilised within future hazard- and paleoenvironmental-related studies.

We examine the timing and magnitude of the last glacial maximum (LGM) and the last glacial termination (LGT) in northwestern Patagonia, situated in the middle latitudes of South America. Our data indicate that the main phase of the LGT began with abrupt warm pulses at 17,800 and 17,100 cal yrs BP, accompanied by rapid establishment of evergreen temperate rainforests and extensive deglaciation of the Andes within 1000 years. This response shows that South American middle-latitude temperatures had approached average interglacial values by 16,800 cal yrs BP. The temperature rise in northwestern Patagonia coincides with the beginning of major warming and glacier recession in the Southern Alps of New Zealand at southern mid-latitudes on the opposite side of the Pacific Ocean. From this correspondence, the warming that began at 17,800 cal yrs BP appears to have been widespread in middle latitudes of the Southern Hemisphere, accounting for at least 75% of the total temperature recovery from the LGM to the Holocene. Moreover, this warming pulse is coeval with the first half of the Heinrich Stadial 1 (HS1) in the North Atlantic region. HS1 featured a decline of North Atlantic meridional overturning circulation, a southward shift of the westerly wind belt in both hemispheres and of the Intertropical Convergence Zone, as well as a weakening of the Asian monsoon. Along with the initiating trigger, identifying the mechanisms whereby these opposing climate signals in the two polar hemispheres interacted —whether through an oceanic or an atmospheric bipolar seesaw, or both— lies at the heart of understanding the LGT.

The 2008 eruption of Volcán Chaitén (VCha) in northwestern Patagonia was the first explosive rhyolitic eruption to have occurred within a century and provided an unprecedented scientific opportunity to examine all facets of the eruption ranging from magma rheology/ascent rates to ash-fall effects on biota and infrastructure. Up to very recently it was thought that the latest eruption prior to the 2008 event occurred c. 9750 cal. a BP. Although a number of researchers have recognised additional eruptive products, but their stratigraphy, age, and geochemical attributes have not been systematically described and/or recorded. In this study, we provide a detailed examination of andic cover-beds and tephra-bearing lake sequences located both proximally and distally to VCha, which record a series of hitherto unknown rhyolitic eruptive products and place all previous observations firmly within a coherent stratigraphic framework. Through major- and trace-element glass shard geochemistry we are able to confidently verify eruptive source. A total of 20 discrete tephra beds are recognised, with at least 10 having widespread areal distributions and/or depositional imprints broadly comparable to, or greater than, the 2008-tephra event. This record indicates that VCha has been continuously but intermittently active as far back as the end of the Last Glacial Maximum (c. 18,000 cal a BP) with two dominant, genetically related magma types and an intermediary ‘mixed’ type. Before this the eruptive record has been largely obscured and/or erased by widespread Andean piedmont glaciation. However, based on the tempo of VCha activity over the last c. 18,000 years, older VCha eruptives can be anticipated to occur as well as future hazardous explosive events. The new eruptive inventory will ultimately be useful for correlating equivalent-aged sequences and refining long-term eruptive tempo as well as corresponding temporal changes in magmatic evolution. Fil: Alloway, Brent V.. The University of Auckland; Nueva Zelanda. University Of Wollongong; Australia Fil: Pearce, Nick J.G.. Aberystwyth University; Reino Unido Fil: Moreno, Patricio I.. Universidad de Chile; Chile Fil: Villarosa, Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto Andino Patagónico de Tecnologías Biológicas y Geoambientales. Universidad Nacional del Comahue. Instituto Andino Patagónico de Tecnologías Biológicas y Geoambientales.; Argentina Fil: Jara, Ignacio. Victoria University Of Wellington; Nueva Zelanda Fil: De Pol-Holz, Ricardo. Universidad de Magallanes; Chile Fil: Outes, Valeria. Universidad de Chile; Chile

We present a detailed record from Lago Pichilafquen to unravel the vegetation, climate and disturbance history of the lowlands of northwestern Patagonia (40 °S) since 14,500 cal yr BP. The presence of 30 tephras throughout the record attest for the proximity of the site to active volcanic centres and allows assessment of the role of volcanic disturbance on past vegetation and fire regime shifts. We interpret alternations in dominance between North Patagonian and Valdivian rainforests driven by changes in temperature and precipitation of westerly origin at multi-millennial and millennial timescales. These trends were punctuated by centennial-scale changes, most of which were coeval with or immediately followed the deposition of tephras and/or paleofires. We identify departures of the local vegetation from the regional trend between 2400 and 7100 cal yr BP, which we interpret as a response of rainforest vegetation and local fire regimes to the disturbance effect of tephra deposition near Lago Pichilafquen. We also find that volcanic disturbance promoted consistent increases in Eucryphia/Caldcluvia within 30 years and paleofires between 60 and 120 years following tephra deposition. Comparisons with palynological records having similar span, time resolution and age control suggest that regional climate has played a central role on the establishment, composition and maintenance of temperate rainforests. This influence is overprinted by disturbance regimes at the local and landscape level, driving divergences and heterogeneity especially at times of relatively weak climatic forcing.

The development of quantitative temperature reconstructions in regions of paleoclimate interest is an important step for providing reliable temperature estimates in that region. Fossil chironomid assemblages have been studied in Patagonia showing great promise for reconstructing paleotemperatures; however there is still a lack of robust temperature inference models in that area. To contribute to the understanding of climate change, a transfer function using chironomids preserved in 46 lakes in Chile and Argentina was developed. The best performing model to infer the mean air temperature of the warmest month was a 3-component WA-PLS model with a coefficient of correlation (r 2 jack ) of 0.56, a root mean square error of prediction (RMSEP) of 1.69 °C and a maximum bias of 2.07 °C. This model was applied to the chironomids preserved in the sediment of the Huelmo mire (41°31′ S, 73°00′ W), in the lake district of northwestern Patagonia. The reconstruction showed several cold spells (one at 13,200 to 13,000 cal yr BP and a cooling trend between 12,600 and 11,500 cal yr BP) associated with the Younger Dryas and/or Huelmo–Mascardi Cold Reversal (HMCR). Our findings support climate models proposing fast acting inter-hemispheric coupling mechanisms including the recently proposed bipolar atmospheric and/or bipolar ocean teleconnections rather than a bipolar see-saw model.

Paleoecological studies from the northern Patagonian Andes (40–44°S) have identified past changes in vegetation, fire regimes and paleoclimate since the last glaciation, including variations in strength and position of the Southern Westerly Winds (SWW). The extent to which records west and east of the Andes provide a congruent paleoclimatic history, however, has not been explored in detail in the literature. Physical and biological contrasts are evident between these regions today and are to be expected in paleoclimate reconstructions. In this context, we present pollen and charcoal records from sediment cores collected in Lago Espejo, a small closed-basin lake located in the core sector of the northern Patagonian Andes that spans uninterrupted the last ∼15,400 years. Following glacier withdrawal, the vegetation surrounding Lago Espejo features scattered Nothofagus woodlands, including relatively thermophilous rainforest trees between ∼15,400 and 14,400 cal yr BP. The disappearance of these trees and an abrupt rise in Nothofagus at ∼14,400 cal yr BP mark the establishment of closed-canopy forests during the Antarctic Cold Reversal, followed by increases in the cold-tolerant hygrophilous conifer Podocarpus nubigena during the Younger Dryas (∼12,700–11,500 cal yr BP). The Holocene vegetation consists of Nothofagus-dominated forests with modest variation in composition and structure until the present, attesting to the resilience of these forest communities to climate change and natural disturbance regimes. Rapid deforestation, anthropogenic fires and the establishment of artificial meadows with exotic herbs introduced by Europeans at ∼150 cal yr BP, triggered a rapid, large-magnitude landscape transformation unprecedented in the last 14,000 years. The timing and structure of vegetation changes revealed by the Lago Espejo record suggest that changes in the SWW were the main driver of vegetation and fire regimes in the Andes of northern Patagonia over the last 15,400 years. Comparison between multiple reconstructions from northern Patagonia reveals overall coherent vegetation and fire regime changes in the western and Andean sectors, and a spatially variable and more divergent behaviour in sites located further east. This spatial patter is akin to the present-day correlation between precipitation and SWW in this region.

Few studies have examined in detail the sequence of events during the last glacial termination (T1) in the core sector of the Patagonian Ice Sheet (PIS), the largest ice mass in the Southern Hemisphere outside of Antarctica. Here we report results from Lago Edita (47°8′ S, 72°25′ W, 570 m a.s.l.), a small closed-basin lake located in a valley overridden by eastward-flowing Andean glaciers during the Last Glacial Maximum (LGM). The Lago Edita record shows glaciolacustrine sedimentation until 19 400 yr BP, followed by organic sedimentation in a closed-basin lake and a mosaic of cold-resistant hygrophilous conifers and rainforest trees, along with alpine herbs between 19 400 and 11 000 yr BP. Our data suggest that the PIS retreated at least ∼ 90 km from its LGM limit between ∼ 21 000 and 19 400 yr BP and that scattered, low-density populations of cold-resistant hygrophilous conifers, rainforest trees, high-Andean and steppe herbs thrived east of the Andes during the LGM and T1, implying high precipitation levels and southern westerly wind (SWW) influence at 47° S. The conifer Podocarpus nubigena increased between 14 500 and 13 000 yr BP, suggesting even stronger SWW influence during the Antarctic Cold Reversal, after which it declined and persisted until 11 000 yr BP. Large increases in arboreal pollen at ∼ 13 000 and ∼ 11 000 yr BP led to the establishment of forests near Lago Edita between 10 000 and 9000 yr BP, suggesting a rise in the regional tree line along the eastern Andean slopes driven by warming pulses at ∼ 13 000 and ∼ 11 000 yr BP and a subsequent decline in SWW influence at ∼ 11 000 yr BP. We propose that the PIS imposed a regional cooling signal along its eastern, downwind margin through T1 that lasted until the separation of the northern and southern Patagonian ice fields along the Andes during the Younger Dryas period. We posit that the withdrawal of glacial and associated glaciolacustrine environments through T1 provided a route for the dispersal of hygrophilous trees and herbs from the eastern flank of the central Patagonian Andes, contributing to the afforestation of the western Andean slopes and pacific coasts of central Patagonia during T1. Fil: Henríquez, William I.. Victoria University Of Wellington; Nueva Zelanda Fil: Villa-Martinez, Rodrigo. Gaia-antártica Universidad de Magallanes; Chile Fil: Vilanova, Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales ; Argentina Fil: De Pol-Holz, Ricardo. Gaia-antártica Universidad de Magallanes; Chile Fil: Moreno, Patricio. Instituto de Ecología y Biodiversidad, Departamento de; Chile

Two Holocene tephras encountered in outcrops, cores and trenches in bogs, and lake cores in the area around Cochrane, southern Chile, are identified (based on their age, tephra glass color and morphology, mineralogy, and both bulk and glass chemistry) as H1 derived from Hudson volcano, and MEN1 derived from Mentolat volcano. New AMS radiocarbon ages indicate systematic differences between those determined in lake cores (MEN1=7,689 and H1=8,440 cal yrs BP) and surface deposits (MEN1=7,471 and H1=7,891 cal yrs BP), with the lake cores being somewhat older. H1 tephra layers range from 8 to 18 cm thick, suggesting that both the area of the 10 cm isopach and the volume of this eruption were larger than previously suggested, but not greatly, and that the direction of maximum dispersion was more to the south. MEN1 tephra layers range from 1-4 cm in thickness, indicating that this was probably a reasonably large (>5 km3) eruption. Some of the lake cores also contain thin layers (

We present detailed pollen and charcoal records from Lago Pichilafquén (~ 41°S) to decipher the effects of climate change and varying disturbance regimes on the composition and structure of the vegetation on the Andean foothills of northwestern Patagonia during the last 2600 yr. Here, temperate rainforests have dominated the landscape since 2600 cal yr BP with variations ranging from cool-temperate and wet north Patagonian rainforests to relatively warm and summer-drought-resistant Valdivian rainforests. We interpret relatively warm/dry conditions between 1900–2600, 690–750 and 320–430 cal yr BP, alternating with cold/wet conditions between 1500–1900, 750–1100 and 430–690 cal yr BP. Rapid deforestation and spread of plants introduced by Europeans occurred at 320 and 140 cal yr BP. The record includes five tephras with ages of 2130, 1460, 1310, 1210, and 340 cal yr BP, all of which precede local fire events and increases in trees favored by disturbance by less than 100 yr. We conclude that centennial-scale changes in the southern westerlies were the primary driver of vegetation shifts in northwestern Patagonia over the last 2600 yr. Within this interval, local disturbance regimes altered the structure, composition, and dynamics of the lowland rainforest vegetation during several discrete, short-lived episodes.

Glacial geologic studies in the Southern Hemisphere (SH) mid-latitudes (40–54°S) indicate renewed glacial activity in southern South America (Patagonia) and New Zealand’s (NZ) South Island starting at ∼7 kyr, the so-called neoglaciation. Available data indicate that neoglacial advances in these regions occurred during a rising trend in atmospheric CO2 and CH4 concentrations, lower-than-present but increasing summer insolation and seasonality contrasts. In this paper we examine the climatological context in which neoglaciations occurred through analysis of the complete Paleoclimate Modelling Inter-comparison Project (PMIP2) database of simulations at 6 kyr for the SH. We observe that the amplitude of the annual insolation cycle in the SH did not change significantly at 6 kyr compared to the pre-industrial values, the largest difference occurring in autumn (MAM, negative anomalies) and spring (SON, positive anomalies). The simulated changes in temperatures over the SH respond to the insolation changes, with a 1–2 month delay over the oceans. This results in a reduced amplitude of the annual cycle of temperature and precipitation over most continental regions, except over Patagonia and NZ, that show a slight increase. In contrast, large-scale circulation features, such as the low and upper level winds and the subtropical anticyclones show an amplified annual cycle, as a direct response to the increased/decreased insolation during the transitional seasons SON/MAM. In the annual mean, there is a small but consistent equatorward shift of the latitude of maximum wind speed of 1–3° over the entire SH, which results in a small increase of wind speed over the South Pacific and Atlantic Oceans north of ∼50°S and a widespread decline south of 50°S. PMIP2 simulations for 6 kyr, indicate that in the annual mean, the SH mid-latitudes were colder, wetter and with stronger winds north of about 50°S. These conditions are consistent with the observed neoglacial advances in the region, as well as with terrestrial paleoclimate records from Patagonia that indicate cooling and a multi-millennial rising trend in Southern Westerly Wind intensity starting at ∼7.8 kyr.

We present chironomid and pollen records from the Huelmo site (∼41°30′S), NW Patagonia, to examine in detail the timing and structure of climate changes during the Last Glacial Termination in the southern mid-latitudes. The chironomid record has the highest temporal and taxonomic resolution for this critical interval, and constitutes the first account of midge faunas at the culmination of the Last Glacial Maximum (LGM) for the region. The chironomid record suggests cold and wet conditions during the LGM, followed by deglacial warming between 17.6 and 16.8 cal kyr BP. Relatively warm conditions prevailed between ∼15–14 cal kyr BP, followed by a reversal in trend with cooling pulses at ∼14 and 13.5 cal kyr BP, and warming at the beginning of the Holocene. Cool-temperate conditions prevailed during the Huelmo Mascardi Cold Reversal (HMCR) which, according to chironomid data, exhibits a wet phase (13.5–12.8 cal kyr BP) followed by a conspicuous drier phase (12.8–11.5 cal kyr BP). The chironomid and pollen records from the Huelmo site indicate step-wise deglacial warming beginning at 17.6 cal kyr BP, in agreement with other paleoclimate records from NW Patagonia and isotopic signals from Antarctic ice cores. Peak warmth during the Last Glacial Termination was achieved by ∼14.5 cal kyr BP, followed by a cooling trend that commenced during the Antarctic Cold Reversal, which later intensified and persisted during the HMCR (13.5–11.5 cal kyr BP). We observe a shift toward drier conditions at ∼12.8 cal kyr BP superimposed upon the HMCR, coeval with intense fire activity and vegetation disturbance during Younger Dryas time.

A high-resolution macroscopic charcoal record from Lago Melli (42°46′S, 73°33′W) documents the occurrence of forest fires in the lowlands of Isla Grande de Chiloé, southern Chile, over the last 16,000 yr. Our data suggest that fire activity in this region was largely modulated by the position/intensity of the southern westerlies at multi-millennial time scales. Fire activity was infrequent or absent between 16,000–11,000 and 8500–7000 cal yr BP and was maximal between ∼ 11,000–8500 and 3000–0 cal yr BP. A mosaic of Valdivian/North Patagonian rainforest species started at ∼ 6000 cal yr BP, along with a moderate increase in fire activity which intensified subsequently at 3000 cal yr BP. The modern transition between these forest communities and the occurrence of fires are largely controlled by summer moisture stress and variability, suggesting the onset of high-frequency variability in summer precipitation regimes starting at ∼ 5500 cal yr BP. Because negative anomalies in summer precipitation in this region are teleconnected with modern El Niño events, we propose that the onset of El Niño-like variability at ∼ 5700–6200 cal yr BP led to a reshuffling of rainforest communities in the lowlands of Isla Grande de Chiloé and an increase in fire activity.

We report pollen and charcoal records from Vega Ñandú (∼ 51°0′S, 72°45′W), a small mire located near the modern forest-steppe ecotone in Torres del Paine National Park, southern Chile. The record shows an open landscape dominated by low shrubs and herbs between 12,600 and 10,800 cal yr BP, under cold and relatively humid conditions. Nothofagus experienced frequent, large-amplitude oscillations between 10,800 and 6800 cal yr BP, indicating recurrent transitions between shrubland/parkland environments, under warm and highly variable moisture conditions. A sustained increase in Nothofagus started at 6800 cal yr BP, punctuated by step-wise increases at 5100 and 2400 cal yr BP, implying further increases in precipitation. We interpret these results as indicative of variations in the amount of precipitation of westerly origin, with prominent increases at 6800, 5100, and 2400 cal yr BP. These pulses led to peak precipitation regimes during the last two millennia in this part of SW Patagonia. Our data suggest variations in the position and/or strength of the southern margin of the westerlies, most likely linked to variations in the extent and/or persistence of sea ice and sea-surface temperature anomalies in the Southern Ocean. Over the last two centuries the record shows a forest decline and expansion of Rumex acetosella, an exotic species indicative of European disturbance.

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.

Within the volcanological community there is a growing awareness that many large- to small-scale, point-source eruptive events can be fed by multiple melt bodies rather than from a single magma reservoir. In this study, glass shard major- and trace-element compositions were determined from tephra systematically sampled from the outset of the Puyehue-Cordón Caulle (PCC) eruption (~1 km3) in southern Chile which commenced on June 4th, 2011. Three distinct but cogenetic magma bodies were simultaneously tapped during the paroxysmal phase of this eruption. These are readily identified by clear compositional gaps in CaO, and by Sr/Zr and Sr/Y ratios, resulting from dominantly plagioclase extraction at slightly different pressures, with incompatible elements controlled by zircon crystallisation. Our results clearly demonstrate the utility of glass shard major- and trace-element data in defining the contribution of multiple magma bodies to an explosive eruption. The complex spatial association of the PCC fissure zone with the Liquiñe-Ofqui Fault zone was likely an influential factor that impeded the ascent of the parent magma and allowed the formation of discrete melt bodies within the sub-volcanic system that continued to independently fractionate. Fil: Alloway, B. V.. University of Wellington; Nueva Zelanda Fil: Pearce, N. J. G.. Aberystwyth University; Reino Unido Fil: Villarosa, Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue; Argentina Fil: Outes, Ana Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue; Argentina Fil: Moreno, P. I.. Universidad de Chile; Chile

Correlations among and identification of the source volcanoes for over 60 Late Glacial and Holocene tephras preserved in eight lacustrine sediment cores taken from small lakes near Coyhaique, Chile (46 degrees S), were made based on the stratigraphic position of the tephra in the cores, lithostratigraphic data (tephra layer thickness and grain size), and tephra petrochemistry (glass color and morphology, phenocryst phases, and bulk-tephra trace element contents determined by ICP-MS). The cores preserve a record of explosive eruptions, since similar to 17,800 calibrated years before present (cal years BP), of the volcanoes of the southernmost Andean Southern Volcanic Zone (SSVZ). The suggested source volcanoes for 55 of these tephras include Hudson (32 events), Mentolat (10 events), and either Maca or Cay or some of the many minor monogenetic eruptive centers (MECs; 13 events) in the area. Only four of these eruptions had been previously identified in tephra outcrops in the region, indicating the value of lake cores for identifying smaller eruptions in tephrochronologic studies. The tephra records preserved in these lake cores, combined with those in marine cores, which extend these records back to 20,000 cal years BP, prior to the Last Glacial Maximum, suggest that no significant temporal change in the frequency of explosive eruptions was associated with deglaciation. Over this time period, Hudson volcano, one of the largest and longest lived volcanoes in the Southern Andes, has had >55 eruptions (four of them were very large) and has produced >45 km(3) of pyroclastic material, making it also one of the most active volcanoes in the SVZ in terms of both frequency and volume of explosive eruptions.

Disentangling the roles of paleofires and explosive volcanism from climatic drivers of past vegetation change is a subject insufficiently addressed in the paleoecological literature. The coastal region of the Chiloé Continental sector of northwestern Patagonia is ideal in this regard considering its proximity to active eruptive centers and the possibility of establishing comparisons with more distal, upwind sites where volcanic influence is minimal. Here we present a fine-resolution pollen and macroscopic charcoal record from Lago Teo with the aim of documenting the local vegetation and climate history, and assessing the role of disturbance regimes as drivers of vegetation change during the last ∼10,000 years. The Lago Teo record shows a conspicuous warm/dry interval between ∼7500 and 10,000 cal yrs BP followed by a cooling trend and increase in precipitation that has persisted until the present, in agreement with previous studies in the region and interpretations of past southern westerly wind activity at multi-millennial scales. The presence of 26 tephras throughout the record allows examination of the relationship between explosive volcanism and vegetation change under contrasting climatic states of the Holocene. We found consistent statistically significant increases in Tepualia stipularis after tephra deposition over the last 10,000 years, in Eucryphia/Caldcluvia between 7500 and 10,000 cal yrs BP and in Hydrangea over the last 7500 years. Our results indicate a primary role of climate change as driver of long-term vegetation change and as a modulator of vegetation responses to volcanic disturbance at multidecadal and centennial timescales. Fil: Henríquez, W. I.. Universidad de Chile; Chile Fil: Moreno, P. I.. Universidad de Chile; Chile Fil: Alloway, B. V.. University of Wellington; Nueva Zelanda Fil: Villarosa, Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue; Argentina

Palynologic and stratigraphic data from Laguna Tahui (42°50′S, 73°30′W) indicate cool–temperate and humid conditions there between 14,000 and 10,000 14C yr B.P., followed by warmer and drier-than-present conditions between 10,000 and 7000 14C yr B.P., and subsequent cooling and rise in precipitation over the last 5800 14C yr. The thermophilous Valdivian trees Eucryphia cordifolia and Caldcluvia paniculata reached their maximum abundance during the early Holocene warm–dry phase (10,000–7000 14C yr B.P.), followed by a rise in lake levels and reexpansion of North Patagonian conifers starting at 7000 and 5800 14C yr B.P., respectively. Variations in the stratigraphic and geographic distribution of temperate rainforests in southern Chile suggest multimillennial trends in temperature and westerly activity, which are spatially and temporally coherent with paleoclimate records from neighboring regions. Climate variability at millennial and submillennial time scales may account for the establishment and persistence of fine-scale mosaics of Valdivian and North Patagonian rainforest species in low- to mid-elevation communities since ∼5800 14C yr B.P.

A pollen record from the Huelmo site (ca. 41°30′S) shows that vegetation and climate changed at millennial time-scales during the last glacial to Holocene transition in the mid-latitude region of western South America. The record shows that a Nothofagus parkland dominated the landscape between 16 400 and 14 600 14C yr BP, along with Magellanic Moorland and cupressaceous conifers. Evergreen North Patagonian rainforest taxa expanded in pulses at 14 200 and 13 000 14C yr BP, following a prominent rise in Nothofagus at 14 600 14C yr BP. Highly diverse, closed canopy rainforests dominated the lowlands between 13 000 and 12 500 14C yr BP, followed by the expansion of cold-resistant podocarps and Nothofagus at ca. 12 500 and 11 500 14C yr BP. Local disturbance by fire favoured the expansion of shade-intolerant opportunistic taxa between 10 900 and 10 200 14C yr BP. Subsequent warming pulses at 10 200 and 9100 14C yr BP led to the expansion of thermophilous, summer-drought resistant Valdivian rainforest trees until 6900 14C yr BP. Our results suggest that cold and hyperhumid conditions characterised the final phase of the Last Glacial Maximum (LGM), between 16 400 and 14 600 14C yr BP. The last ice age Termination commenced with a prominent warming event that led to a rapid expansion of North Patagonian trees and the abrupt withdrawal of Andean ice lobes from their LGM positon at ca. 147 000 14C yr BP. Hyperhumid conditions prevailed between 16 400 and 13 000 14C yr BP, what we term the ‘extreme glacial mode’ of westerly activity. This condition was brought about by a northward shift and/or intensification of the southern westerlies. The warmest/driest conditions of the last glacial–interglacial transition occurred between 9100 and 6900 14C yr BP. During this period, the westerlies shifted to an ‘extreme interglacial mode’ of activity, via a poleward migration of stormtracks. Our results indicate that a highly variable climatic interval lasting 5500 14C years separate the opposite extremes of vegetation and climate during the last glacial-interglacial cycle, i.e. the end of the LGM and the onset of the early Holocene warm and dry period. Copyright © 2003 John Wiley & Sons, Ltd.

Volcán Chaitén (southern Chile, ∼43°S) initiated an historically unprecedented eruption in A.D. 2008, surprising the local inhabitants, Chilean and Argentine authorities, and the geologic community. Available data at the time indicated an absence of explosive eruptions from this rhyolitic volcano since a large-magnitude eruptive event dated at ca. 10,500 yr B.P. We present lake-sediment data from Lago Teo, a small closed-basin lake located in the immediate vicinity of both Chaitén township and the volcano, that spans the past ∼10,000 yr and contains 26 pyroclastic fallout deposits. Glass-shard electron microprobe analyses revealed ten rhyolitic tephras indistinguishable in composition from the 2008 Volcán Chaitén eruption, and ten others potentially derived from the Michinmahuida volcanic complex. Among the rhyolites, we detected three closely spaced tephras deposited between ca. 9460 and 9680 yr B.P., followed by two thick tephras dated at ca. 7700 and ca. 5080 yr B.P. Three other closely spaced tephras occur between ca. 600 and 850 yr B.P., the most recent prehistoric event at ca. 420 yr B.P., and a 3-cm-thick tephra deposited during the 2008 event. We calculate a median recurrence of ∼310 yr between eruptive events from all sources over the past ∼10,000 yr, and ∼200 yr between Volcán Chaitén events over the past millennium. Our results not only challenge the notion of an ∼10,500-yr-long quiescence for Volcán Chaitén activity, but also suggest that the 2008 eruption was an overdue phenomenon in the context of its postglacial eruptive history, illustrating the advantage and absolute necessity of utilizing lake-sediment archives for developing continuous well-dated time series inventories of explosive volcanic events. Fil: Moreno, Patricio I.. Universidad de Chile; Chile Fil: Alloway, B. V.. Victoria University of Wellington; Nueva Zelanda Fil: Villarosa, Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación En Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue; Argentina Fil: Outes, Ana Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación En Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue; Argentina Fil: Henriquez, W. I.. Universidad de Chile; Chile Fil: de Pol Holz, R.. Universidad de Concepción; Chile Fil: Pearce, N. J. G.. Aberystwyth University; Reino Unido

Late twentieth-century instrumental records reveal a persistent southward shift of the Southern Westerly Winds during austral summer and autumn associated with a positive trend of the Southern Annular Mode (SAM) and contemporaneous with glacial recession, steady increases in atmospheric temperatures and CO2 concentrations at a global scale. However, despite the clear importance of the SAM in the modern/future climate, very little is known regarding its behaviour during pre-Industrial times. Here we present a stratigraphic record from Lago Cipreses (51S), southwestern Patagonia, that reveals recurrent B200-year long dry/warm phases over the last three millennia, which we interpret as positive SAM-like states. These correspond in timing with the Industrial revolution, the Mediaeval Climate Anomaly, the Roman and Late Bronze Age Warm Periods and alternate with cold/wet multicentennial phases in European palaeoclimate records. We conclude that SAM-like changes at centennial timescales in southwestern Patagonia represent in-phase interhemispheric coupling of palaeoclimate over the last 3,000 years through atmospheric teleconnections. Fil: Moreno, Patricio. Universidad de Chile; Chile Fil: Vilanova, Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Villa Martinez, R.. Universidad de Chile; Chile Fil: Garreaud, R. D.. Universidad de Chile; Chile Fil: Rojas, M.. Universidad de Chile; Chile Fil: De Pol Holz, R.. Universidad de Chile; Chile

Lakes formed in the Aysen region of southern Chile after the retreat of mountain glaciers, established by ~17,900 calendar years before present (cal years BP) or earlier, contain numerous late-glacial and Holocene tephra layers derived from >70 eruptions of the volcanoes in the region, including Hudson, the southernmost in the Andean Southern Volcanic Zone (SVZ). Sediment cores from seven of these lakes contain an unusually thick late-glacial age tephra layer, which based on its distribution and bulk trace-element composition was derived from a large explosive eruption of Hudson volcano between 17,300 and 17,440 cal years BP and is termed Ho. In 13 cores from six of these lakes, each located ~100 km generally northeast of Hudson, the Ho tephra layer ranges between 50 and 88 cm in thickness, and contains pumice grains up to 2 cm in maximum diameter. Comparison with three previously documented large explosive Holocene Hudson eruptions (H1 at 7,750 cal years BP, H2 at 3,920 cal years BP, and H3 in 1991 AD) suggests that Ho was larger, with an estimated tephra volume of >20 km3, the largest post-glacial eruption documented for any volcano in the southern Andes and most likely responsible for the formation of the Hudson caldera. In total, Hudson has erupted ≥45 km3 of pyroclastic material in the last ~17,500 years, making it the most productive volcano in the southern Andes in terms of the total volume erupted since the beginning of deglaciation in the region. Chemical stratification is not seen in the waterlain Ho tephra, but these deposits are bi-modal, consisting of a much greater proportion of dark glassy basaltic-trachyandesite dense fragments and pumice, with glasses which range between 55 and 59 wt.% SiO2, along with volumetrically less-significant lighter-colored trachydacite pumice, with glass of 66 wt.% SiO2. In contrast, H1 products are trachyandesitic in composition, H2 ones are more felsic than H1, being composed essentially of trachydacite, and although H3 1991 AD again produced tephra of bi-modal compositions, it erupted a much smaller proportion of mafic compared to felsic material than did Ho. Thus, the repetitive large explosive eruptions of Hudson volcano have evolved to progressively less-mafic overall compositions from late-glacial to historic times, and their volumes have decreased. Sr-isotopic composition of bulk samples of the most mafic dense glass and most felsic pumice components of the Ho tephra, as well as samples from other Hudson eruptions, which overall range from 51 to 66 wt.% SiO2, with 525 to 227 ppm Sr, are all similar (0.70444 ± 0.00007), indicating that crystal-liquid fractionation rather than crustal assimilation was the main process responsible for these chemical variations.

We present a detailed record from Lago Lepue to examine vegetation, climate and fire-regime changes since the Last Glacial Maximum (LGM) in central-east Isla Grande de Chiloe (43°S), northwestern Patagonia. Precipitation in this region correlates with the intensity of the southern westerly winds (SWW), allowing reconstruction of past SWW behavior through precipitation-sensitive sensors. Recession from the LGM glacier margins exposed the central-east sector of Isla Grande de Chiloe by 17,800 cal yr BP, followed by the immediate colonization of pioneer cold-resistant herbs/shrubs and rapid establishment of closed-canopy Nothofagus forests by 17,000 cal yr BP. Broad-leaved temperate rainforests have persisted since then with compositional changes driven by changes in temperature, hydrologic balance and disturbance regimes. We detect low lake levels and enhanced fire activity between 800–2000, 4000–4300, ∼8000–11,000 and 16,100–17,800 cal yr BP, implying southward shifts and/or weaker SWW flow that alternated with cold, humid phases with muted fire activity. Covariation in paleoclimate trends revealed by the Lago Lepue record with tropical and Antarctic records since the LGM, suggests that the SWW have been a highly dynamic component of the climate system capable of linking climate changes from low- and high-southern latitudes during the Last Glacial termination and the current interglacial.

Understanding the relative timings of climate events in the Northern and Southern hemispheres is a prerequisite for determining the causes of abrupt climate changes. But climate records from the Patagonian Andes1,2,3,4 and New Zealand5,6,7,8 for the period of transition from glacial to interglacial conditions—about 14.6–10 kyr before present, as determined by radiocarbon dating—show varying degrees of correlation with similar records from the Northern Hemisphere. It is necessary to resolve these apparent discrepancies in order to be able to assess the relative roles of Northern Hemisphere ice sheets and oceanic, atmospheric and astronomical influences in initiating climate change in the late-glacial period. Here we report pollen records from three sites in the Lake District of southern Chile (41° S) from which we infer conditions similar to modern climate between about 13 and 12.2 14C kyr before present (bp), followed by cooling events at about 12.2 and 11.4 14C kyr bp, and then by a warming at about 9.8 14C kyr bp. These events were nearly synchronous with important palaeoclimate changes recorded in the North Atlantic region9, supporting the idea that interhemispheric linkage through the atmosphere was the primary control on climate during the last deglaciation. In other regions of the Southern Hemisphere, where climate events are not in phase with those in the Northern Hemisphere, local oceanic influences may have counteracted the effects that propagated through the atmosphere.

A pollen record from Lago Condorito (41°45′S, 73°07′W) shows that North Patagonian Rain Forest taxa predominated between about 13,000 and 12,200 14C yr B.P. in the lowlands of southern Chile, near the city of Puerto Montt. This was followed by the expansion and persistence of the conifer Podocarpus nubigena between 12,200 and 9900 14C yr B.P. Trees favored by disturbance expanded between 11,200 and 9900 14C yr B.P., concurrent with sharp and sustained increases of microscopic charcoal particles. Taxa of low-elevation rain forests expanded and became more diverse in pulses centered at 9900 and 9000 14C yr B.P., following the disappearance of P. nubigena. These data suggest conditions approaching modern climate between about 13,000 and 12,200 14C yr B.P. The climate cooled between 12,200 and 9900 14C yr B.P., then quickly warmed to interglacial conditions. Stand-replacing fires occurred near Lago Condorito between 11,200 and 9900 14C yr B.P., under cool-temperate, humid conditions. The proximity and reported antiquity of the Monte Verde archeological site raise the possibility that these fires were set by human activities.

We report pollen, spore, and charcoal records from Lago Augusta (47°05′S, 72°23′W, 440 m a.s.l.), a small closed-basin lake located near the modern forest-steppe ecotone east of the Andes in Central Patagonia, Chile. The record shows local ice-free conditions through the last glacial termination in the Rio Chacabuco Valley and flooding by an ice-dammed lake. Once this proglacial lake ceased to inundate areas above 450 m a.s.l., the valley was colonized by herbs, shrubs and evergreen rainforest taxa between 15,600 and 16,000 cal yr BP, indicating an open landscape under cold/wet conditions. Millennial-scale fluctuations in the hygrophilous conifer Fitzroya / Pilgerodendron suggest precipitation variations within a cool/wet climate between 11,800 and 13,400 cal yr BP, followed by the establishment of dense Nothofagus forests between 9800 and 11,800 cal yr BP and declines in hygrophilous and cold-resistant trees, herbs and shrubs. This interval coincided with peak fire activity and laminated carbonate deposition. Nothofagus forests have persisted with little variation since 9800 cal yr BP, except for a sudden decline associated with a rapid increase in Rumex cf. acetosella , an exotic weed introduced by Europeans. Our results and interpretations are best explained by changes in the strength/position of the southern westerly winds at millennial and multi-millennial timescales since the last glaciation. Contrary to previous interpretations, we propose increased precipitation of westerly origin in the Andean sector of central-east Patagonia between 11,800 and 16,000 cal yr BP followed by a decline between 9800 and 11,800 cal yr BP and an increase thereafter. These trends are coherent with variations of the southern westerly winds identified in other terrestrial mid-latitude records, suggesting zonally symmetric changes in atmospheric circulation since the last glaciation.

Much of the ongoing discussion regarding synchrony or bipolar asynchrony of paleoclimate events has centered on the timing and structure of the last glacial termination in the southern mid- latitudes, in particular the southwestern Patagonian region (50 � e55 � S). Its location adjacent to the Drake Passage and near the southern margin of the southern westerly winds (SWW) allows examining the postulated links between the Southern OceaneSWW coupled system and atmospheric CO2 variations through the last glacial termination. Results from two sites located in the Ultima Esperanza area (52