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The Physical Geography of Patagonia and Tierra del Fuego

  • Instituto Patagonico para el Estudio de los Ecosistemas Continentales (IPEEC-CONICET)

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This chapter focuses on the physical geography of Late Cenozoic of Patagonia and Tierra del Fuego. This chapter discusses a junction of natural elements in the southern end of South America. Bedrock substratum and structure, climate, distribution of the superficial runoff, soils, and vegetation, all act together in a systematic, cause–effect relationship and form a group of homogeneous geographical spaces that are joined under first-order geological and atmospheric elements, such as tectonic plates and the general atmospheric circulation. The interaction of the wetter Pacific winds and the Andean Cordillera is the basic natural condition that determines the geographical aspects of the natural, physical environment of the southernmost end of South America. The pluvial and snow régime of the streams, the allochtonous character of the tableland streams, the development of contrasting biomes, such as jungle-like forests and rainshadow deserts, with a modest thermal régime are a consequence of the orographic barrier interaction with the air masses of the Southern Pacific anticyclonic centers and the polar front.
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... Patagonia and Tierra del Fuego, is the region that extends to the southernmost tip of South America, encompassing Chile and Argentina from ~40 • to ~56 • S (Coronato et al., 2008) (Fig. 1). Patagonia includes the Southern Andes, which defines a narrow western flank featuring numerous islands and fjords opened to the Pacific Ocean and an eastern slope characterized by extensive steppes, locally known as pampas, towards the Atlantic Ocean. ...
... The Andean Cordillera interrupts the SWWB that brings humid air from the Pacific. This causes shadow rainfall (>1000 mm) in the western Andes, while the eastern part remains dry (>200 mm, Coronato et al., 2008;Aravena and Luckman, 2009;Garreaud, 2009). Hence, eastern Patagonia is characterized by a semi-arid climate, while western Patagonia is very humid due to the oceanic influence from the Pacific (Borromei and Musotto, 2016). ...
We use pollen and dinocyst assemblages from three sedimentary sequences of the San Jorge Gulf (SJG) to document the vegetation history of the extra-Andean/eastern Patagonia (Argentina), and the latitudinal variations of the Southern Westerly Wind Belt (SWWB) in relation with ocean changes during the Late Pleistocene and Holocene. Our results suggest that prior to 14 cal ka BP, the vegetation of the SJG was dominated by halophytic taxa probably related to arid conditions in coastal environments. After 14 cal ka BP, pollen data suggest the development of shrub and herb vegetation in the Patagonian steppe then characterized by semi-arid conditions. The 14 cal ka BP transition is marked by increasing Nothofagus pollen abundances, suggesting strong westerlies at the onset of the Antarctic Cold Reversal (ACR). This transition is also marked by the occurrence of marine palynomorphs (dinocysts, organic linings of foraminifers), which relate to sea-level rise. The dinocyst assemblages allowed us to quantitatively estimates changes in summer sea-surface temperature (SST) and annual net primary productivity. Between 14 and 10.8 cal ka BP, which encompasses the glacial termination and the early Holocene, dinocyst assemblages are dominated by Operculodinium centrocarpum (∼82%) and Spiniferites mirabilis (∼8%) that suggest warmer conditions than at present. The transition from early to middle Holocene was marked by high SWWB intensity as suggested by pollen assemblages, and an increase of heterotrophic taxa such as Brigantedinium spp., Echinidinium sp., Dubridinium sp., and the cysts of Polykrikos kofoidii, suggesting increased primary productivity and gradual cooling of surface water. After 4 cal ka BP, pollen data suggest a decrease in the SWWB intensity that correlates with glacier advances in Patagonia and a further decrease in summer SST in the SJG.
... The altitude of the present equilibrium line at ca. 1100 m a.s.l. suggests that most of these glaciers are in rapid recession (Coronato et al. 2008). Indeed, Bah ıa Grande also has a small catchment area that supplies sediment directly into it. ...
Tierra del Fuego in Argentina is a unique location to examine past Holocene wind variability since it intersects the core of the Southern HemisphereWesterlyWinds (SHWW). TheSHWWare the most powerful prevailing winds on Earth. Their variation plays a role in regulating atmospheric CO2 levels and rainfall amounts and distribution, both today and in the past. We obtained a piston core (LF06-PC8) from Bahía Grande, a protected sub-basin at the southern margin of Lago Fagnano, the largest lake in Tierra del Fuego. This article focuses on the uppermost 185 cm of this core, corresponding to laminated sediment from the last ~6.3 ka. Laminations consist of millimetrescale paired dark and light layers. Previous studies and new geochemical analysis show that the dark and light layers are characterized by differing concentrations of Mn and Fe.We attribute the distribution of Mn and Fe to episodic hypolimnic oxic–anoxic variations. The age model suggests an approximately bidecadal timescale for the formation of each layer pair. We propose a new model of these redox changes with the SHWW variations. The most likely phenomenon to produce complete water-column mixing is thermobaric instability, which occurs in colder winters with low-intensity SHWW (El Niño-like conditions). In contrast, windier winters are characterized by highertemperatures and reduced mixing in the water column, facilitating a decline in oxygen concentration. Laminations, and the inferred presence of periodic hypolimnion redox changes, are common features of the past ~6.3 ka. Geochemical proxy variability is compatible with an intensification of El Niño/Southern Oscillation activity during the past ~2 ka
Despite being an underpopulated region, Patagonia has attracted the attention of scientists since the very beginning of its settlement. From classical explorers such as Darwin or D´Orbigny, to modern science including nuclear and satellite developments, several disciplines have focused their efforts on unraveling Patagonia’s natural and social history. Today, scientific and technological research is shifting from being shaped by northern agendas, towards more locally oriented objectives, such as the management of natural resources, the modernization of energy production and distribution, and the coexistence of rural and cosmopolitan social lifestyles. At the intersection of all these topics, new conflicts concerning the economy, human development, population, and the proper and long-standing planification and management of the landscape and its natural resources have emerged. These conflicts, of course, have also caught the attention of many interdisciplinary research groups. This series is aimed at describing and discussing various aspects of this complex reality, but also at bridging the gaps between the scientific community and governments, policymakers, and society in general. The respective volumes will analyze and synthesize our knowledge of Patagonian biodiversity at different scales, from alleles, genes and species, to ecosystems and the biosphere, including its multilevel interactions. As humans cannot be viewed as being separate from biodiversity, the series’ volumes will also share anthropological, archaeological, sociological and historical views of humanity, and highlight the wide range of benefits that ecosystems provide to humanity including provisioning, regulating and cultural services.
Andean Patagonian catchments comprise large freshwater networks along a sharp west-to-east bioclimatic gradient. The Nahuel Huapi National Park (Argentina) includes the headwaters of the largest fluvial network of North Patagonia characterized by mountain and piedmont aquatic systems draining toward the Atlantic and Pacific oceans. Several studies in the region have recorded moderate to high mercury (Hg) levels in different environmental compartments of Andean catchments. Lake sediment sequences have revealed that the departure of Hg concentrations from background levels, attributable to global circulation of this toxic metal, is connected to frequent disturbances caused by active volcanoes of the Andean belt (Southern Volcanic Zone of South America) and wildfires. Freshwaters of the region are oligo- to ultraoligotrophic, with extremely low concentrations of dissolved organic matter, displaying high total Hg to dissolved organic carbon ratios which reflect in high Hg availability. This work reviews the evidence from different studies performed in Nahuel Huapi lake catchment, which explored the sources of Hg, the terrestrial and aquatic pathways of its biogeochemical cycling, as well as its circulation in lake food webs. Moreover, potential changes in the cycle of Hg in Andean Patagonian catchments are discussed in the context of the global and regional climate trends. In this regard, changes in Hg cycling in ecosystems of the region are expected to be manyfold because different components influencing this process (Hg stored in ecosystems, processing rates, the lateral transport to aquatic end points, methylation, etc.) are climate-sensitive.KeywordsPatagonian catchments Mercury Mercury sources Freshwater Mercury trophodynamics
Rainbow trout (Oncorhynchus mykiss) was introduced in most lakes of Patagonia, generating concern about its impact on the receiving communities. However, the information about the effects of trout in stocked lakes of this region is still fragmentary. We conducted a comprehensive comparative study of fishless and stocked lakes of the arid southern Patagonia to analyse the extent of trout effects on the community composition, primary productivity and food webs, considering also contrasting climatic conditions (wet and dry years). Rainbow trout shaped the community of pelagic crustaceans, affecting both species’ dominance and size structure. Stocked lakes also showed substantial differences in phytoplankton structure, and higher abundances of microplanktonic cyanobacteria, probably caused by top-down effects. These changes were more pronounced during dry periods, indicating the concomitant effects of trout introduction and climate fluctuations. Trout also generated alterations in food webs, forcing their main prey (amphipods) to shift from predominantly pelagic to benthic/littoral feeders. Differences in stable isotope values also indicate changes in the habitat coupling when trout were present. We discuss results from a conservation perspective, considering the potential consequences for waterbirds, mainly for the critically endangered hooded grebe (Podiceps gallardoi), which have their reproductive habitat in the analysed aquatic systems.
Patagonian wetlands contribute significantly to regional biodiversity and also fulfill a wide range of nature contributions to people such as water storage and purification, carbon sequestration, pasturelands, nutrient cycling, food production, and recreation. Despite covering less than 7% of the region, they exhibit a wide climatic, geomorphologic, and physicochemical variability that drives their biodiversity. Moreover, significant differences exist not only in their ecological conditions but also in the main uses they are subjected to, and the subsequent threats they face. Therefore, among others, vertientes (springs) and lagunas (shallow lakes and ponds) are used as drinking water sources, vegas and mallines as pasturelands, and turberas (peat bogs) for peat extraction. The global loss of wetland biodiversity through increase in human pressures and emerging threats like climate change demands concerted actions based on adequate knowledge about ecosystems dynamics, and functioning, to halt their deterioration and their many valuable contributions to people. Despite being essential for the regional economy, Patagonian wetlands are still far from meeting global conservation targets, with less than 3% of those in arid and semiarid Patagonia being located within protected areas. This chapter aims at summarizing current ecological knowledge on the main Patagonian wetland types, their current uses, and the threats they face, and detecting knowledge gaps to be filled in future studies.
Finkl, C.W. and Makowski, C., 2022. Classification of coastal belts in the Argentine subpolar southeast coast of Tierra del Fuego using the BCCS (Biophysical Cross-shore Classification System). Journal of Coastal Research, 38(5), 908924. Coconut Creek (Florida), ISSN 0749-0208. The Biophysical Cross-shore Classification System (BCCS) was experimentally applied to the southeast coast of Tierra del Fuego, Argentina, by compartmentalizing the coast into seven discrete coastal belts that retained a degree of homogeneity from 2 km offshore to about 5 km inland. By interpreting satellite imagery, coastal belts were subdivided into cross-shore transects with alongshore spread to produce codified concatenations that characterized specific eco-geomorphological sequences comprising domains. Different types of domains were identified by archetypes that specified a particular Dominant Catenary Sequence (DCS), which in turn was refined by the inclusion of subarchetypes to produce a Coastal Ecological Sequence (CES). The seven coastal belts comprising a 58.5 km stretch of shore contained 39 CES transects that averaged about 1.5 km of shore length, but ranged from 0.8 km to 3.3 km in alongshore stretch. Dominant offshore, inshore, and onshore classificatory units included Rock (R), Beach (Be), and Cliff (Cl) catenas, which were followed inland by Wetland (W), Lake (Lk), Channel (Ch), and Upland (U) archetypical sequences. Delta (De) and Beach Ridge (Br) archetypes were noted as minor features in some cross-shore transects. Common trisequent DCS transects included R-Be-Cl and Be-Cl-U, which subsequently incorporated landward variations with Lagoon (L), Lake (Lk), and Wetland (W) archetypes. Results of this experiment showed that the BCCS comprehended how subpolar periglacial and paraglacial coastal belts dominantly comprised by glacial outwash have ground surface manifestations that are recognizable in satellite imagery by recurring spectral patterns. This cold tundra coastal region is thus largely characterized by rocky offshores and gravelly beaches backed by cliffs (composed of unconsolidated materials) and channeled wetland (peatland) hinterlands with coastal marine lakes and forested uplands. In accordance with the BCCS, this classification can be concised to CES subarchetype code sequences such as Rrr-Besi-Clse-Wmr-Chmd-Lkcm-Ufo. This study demonstrates that codification of cross-shore eco-geomorphological transects using the BCCS provides a shorthand notation for classifying coastal belts in high-latitude regions.
Environmental changes were reconstructed from a multiproxy synthesis of over 30 localities from the Isla Grande de Tierra del Fuego and Isla de los Estados, southernmost South America. At a local scale, the results from the mountain forest and gently undulating steppe areas were integrated as well as those from the marine environments of the Beagle Channel and the Atlantic coasts. At a regional scale, the results were integrated with those published for the southernmost Andean and Extra-Andean Patagonia and the Antarctic Peninsula. This study focuses on the environmental evolution during the Late Glacial-Holocene transition, the Middle to Late Holocene transgressive-regressive hemicycle and wet-dry oscillations, the Medieval Climate Anomaly, the Little Ice Age, the tephra inputs from the Patagonian Andes, and the recent climatic warming. Most paleoenvironmental changes are related to variations in the latitudinal position and intensity of the Southern Westerly Winds (SWW) while others are associated with astronomical or endogenous forcings. At a strong intensity of the SWW, a greater contribution of humidity to the forest areas and an increase in the rainfall gradient create windy and arid conditions in the steppe. At a weak intensity of the SWW, lower humidity input in the forest areas and the advection of air masses from the Atlantic Ocean promoted humid and slightly windy conditions in the steppe. Similar environmental trends are observed between terrestrial and marine environments in the center and south of Tierra del Fuego, Isla de los Estados and the Antarctic Peninsula, and between the Fuegian steppe and Extra-Andean Patagonia. The paleoclimatic evidence reveal high environmental variability in the last 10,000 years for this sector of the Southern Hemisphere.
Glaciar Pio XI, the largest glacier in South America, has experienced an advance during the 20th century, unlike virtually all other glaciers in Patagonia, which are retreating rapidly. Climatological records of the last 80 years are analyzed together with ice-velocity and meteorological measurements collected during November 1995 near the tidewater front of Glaciar Pio XI. Ice speeds of up to 50 m d−1 were measured, the maximum occurring during a period when air temperatures were high.