scholarly journals Environmental and climatic changes in Central Chilean Patagonia since the Late Glacial (Mallín El Embudo, 44° S)

2013 ◽  
Vol 9 (5) ◽  
pp. 5747-5784
Author(s):  
M. E. de Porras ◽  
A. Maldonado ◽  
F. A. Quintana ◽  
A. Martel-Cea ◽  
O. Reyes ◽  
...  
Keyword(s):  
Regional Scale ◽  
Late Glacial ◽  
Climatic Changes ◽  
Landscape Configuration ◽  
Effective Moisture ◽  
Nothofagus Forest ◽  
Chilean Patagonia ◽  
Precipitation Seasonality ◽  
Fire Activity ◽  
Southern Westerlies

Abstract. Multi-millennial environmental and climatic changes in Central Chilean Patagonia (44–49° S) during the Last Glacial–Interglacial cycle have been of particular interest as changes in the position and strength of the Southern Westerlies are the major forcing factor conditioning the environmental dynamics. Recent attempts to reconstruct regional environmental and climatic signals from Central Chilean Patagonia reveal some discrepancies and unclear issues among the records. This paper presents the 13 ka pollen and charcoal records from Mallín El Embudo (44°40' S; 71°42' W) located in the deciduous Nothofagus forest in the middle Río Cisnes valley. The paper aims to (1) establish the timing and magnitude of local vegetation changes and fire activity since the Late Glacial and (2) integrate these results at the regional scale in order to discuss the discrepancies and depict the Central Chilean Patagonia environmental and climatic dynamics since Late Glacial. Open landscapes dominated by grasses associated with scattered Nothofagus forest patches dominated middle Río Cisnes valley between 13–11.2 ka suggesting low effective moisture but also reflecting that landscape configuration after glacial retreat was still ongoing. At 11.2 ka, a sudden development of an open and quite dynamic Nothofagus forest probably associated to the synchronous high fire activity occurred suggesting a rise in effective moisture. Since 9.5 ka, the record reflects the presence of a closed Nothofagus forest related to higher/similar effective moisture conditions than before but under an unmarked precipitation seasonality. The forest experienced a slight canopy opening since 5.7 ka, probably due to slightly drier conditions than before followed by a sudden change around 4.2 ka associated with fire and volcanic disturbances. The recovery of an open Nothofagus forest related to slight wetter conditions (similar to present) occurred around 2 ka and persisted under highly variable climatic conditions up to 0.1 ka when massive forest burning and logging due to European settlements occurred. Central Chilean Patagonian climatic and environmental changes at millennial-centennial time scales since Late Glacial were driven by changes in the Southern Westerlies latitudinal shift and/or intensity but during the Late Holocene fire, volcanism and humans arise as major forcings contributing to environmental dynamics.

scholarly journals Environmental and climatic changes in central Chilean Patagonia since the Late Glacial (Mallín El Embudo, 44° S)

2014 ◽  
Vol 10 (3) ◽  
pp. 1063-1078 ◽  
Author(s):  
M. E. de Porras ◽  
A. Maldonado ◽  
F. A. Quintana ◽  
A. Martel-Cea ◽  
O. Reyes ◽  
...  
Keyword(s):  
Environmental Changes ◽  
Regional Scale ◽  
Late Glacial ◽  
Climatic Changes ◽  
Landscape Configuration ◽  
Effective Moisture ◽  
Nothofagus Forest ◽  
Chilean Patagonia ◽  
Fire Activity ◽  
Southern Westerlies

Abstract. Multi-millennial environmental and climatic changes in central Chilean Patagonia (44–49° S) during the Last Glacial–Interglacial cycle have been of particular interest as changes in the position and strength of the southern westerlies are the major forcing factor conditioning the environmental dynamics. Recent attempts to reconstruct regional environmental and climatic signals from central Chilean Patagonia reveal some discrepancies and unclear issues among the records. This paper presents the 13 ka pollen and charcoal records from Mallín El Embudo (44° 40' S, 71° 42' W) located in the deciduous Nothofagus forest in the middle Río Cisnes valley. The paper aims to (1) establish the timing and magnitude of local vegetation changes and fire activity since the Late Glacial and (2) integrate these results at the regional scale in order to discuss the discrepancies and depict the environmental and climatic dynamics in central Chilean Patagonia since the Late Glacial. Open landscapes dominated by grasses associated with scattered Nothofagus forest patches dominated the middle Río Cisnes valley between 13 and 11.2 ka suggesting low effective moisture but also indicating that landscape configuration after glacial retreat was still ongoing. At 11.2 ka, the sudden development of an open and quite dynamic Nothofagus forest probably associated with the synchronous high fire activity occurred, suggesting a rise in effective moisture associated with dry summers. Since 9.5 ka, the record reflects the presence of a closed Nothofagus forest related to higher effective moisture conditions than before combined with moderate dry summers that may have triggered a high frequency of low-magnitude crown fires that did not severely affect the forest. The forest experienced a slight canopy opening after 5.7 ka, probably due to slightly drier conditions than before followed by a sudden change to open forest conditions around 4.2 ka associated with fire and volcanic disturbances. Around 2 ka, the recovery of a closed Nothofagus forest related to slightly wetter conditions (similar to present) occurred and persisted under highly variable climatic conditions up to 0.1 ka when massive forest burning and logging due to European settlements occurred. Central Chilean Patagonian climatic and environmental changes at millennial–centennial timescales since the Late Glacial were driven by changes in the southern westerlies latitudinal position and/or intensity, but during the late Holocene fire, volcanism and humans arose as forces contributing to environmental dynamics.

Climate and vegetation change during the late-glacial/early-Holocene transition inferred from multiple proxy records from Blacktail Pond, Yellowstone National Park, USA

2013 ◽  
Vol 79 (3) ◽  
pp. 391-402 ◽  
Author(s):  
Teresa R. Krause ◽  
Cathy Whitlock
Keyword(s):  
Climate Change ◽  
Yellowstone National Park ◽  
National Park ◽  
Pinus Contorta ◽  
Vegetation Change ◽  
Environmental Changes ◽  
Regional Scale ◽  
Late Glacial ◽  
Early Holocene ◽  
Fire Activity

AbstractA series of environmental changes from late-glacial ice recession through the early Holocene are revealed in a 7000-yr-long record of pollen, charcoal, geochemistry, and stable isotopes from Blacktail Pond, a closed-basin lake in Yellowstone National Park. Prior to 11,500 cal yr BP, cool conditions dominated, fire activity was low, and alpine tundra and Picea parkland grew on the landscape. A step-like climate change to warm summer conditions occurred at 11,500 cal yr BP. In response, fire activity increased facilitating a transition from Picea parkland to closed Pinus forest. From 11,500 to 8280 cal yr BP, warm summers and abundant moisture mostly likely from high winter snowfall supported closed Pinus contorta forests. Cooler drier summer conditions prevailed beginning 8280 cal yr BP due to decreased summer insolation and winter snowpack, and lower parkland developed. The timing of vegetation change in the Blacktail Pond record is similar to other low- and middle-elevation sites in the northern Rocky Mountains during the late-glacial period, suggesting local plant communities responded to regional-scale climate change; however, the timing of vegetation changes was spatially variable during the early and middle Holocene due to the varying influences of strengthened summer monsoons and subtropical high on regional precipitation patterns.

scholarly journals A major hydrobiological change in Dasht-e Arjan Wetland (southwestern Iran) during the late glacial – early Holocene transition revealed by subfossil chironomids

2019 ◽  
Vol 56 (8) ◽  
pp. 848-856
Author(s):  
Cyril Aubert ◽  
Morteza Djamali ◽  
Matthew Jones ◽  
Hamid Lahijani ◽  
Nick Marriner ◽  
...  
Keyword(s):  
Lake Level ◽  
Regional Scale ◽  
Younger Dryas ◽  
Late Glacial ◽  
Early Holocene ◽  
Geochemical Data ◽  
The Holocene ◽  
Chironomus Plumosus ◽  
Subfossil Chironomids ◽  
Southwestern Iran

The late glacial – early Holocene transition is a key period in the earth’s history. However, although this transition is well studied in Europe, it is not well constrained in the Middle East and palaeohydrological records with robust chronologies remain scarce from this region. Here we present an interesting hydrobiological record showing a major environmental change occurring in the Dasht-e Arjan Wetland (southwestern Iran, near to Persepolis) during the late glacial – early Holocene transition (ca. 11 650 years cal BP). We use subfossil chironomids (Insecta: Diptera) as a proxy for hydrological changes and to reconstruct lake-level fluctuations. The Arjan wetland was a deep lake during the Younger Dryas marked by a dominance of Chironomus plumosus/anthracinus-type, taxa adapted to anoxic conditions of deep waters. At the beginning of the Holocene, a drastic decrease (more than 80% to less than 10%) of Chironomus plumosus/anthracinus-type, combined with diversification of littoral taxa such as Polypedilum nubeculosum-type, Dicrotendipes nervosus-type, and Glyptotendipes pallens-type, suggests a lake-level decrease and a more vegetalized aquatic environment. We compare and contrast the chironomid record of Arjan with a similar record from northwestern Iran. The palaeoclimatic significance of the record, at a local and regional scale, is subsequently discussed. The increase in Northern Hemisphere temperatures, inferred by geochemical data from NGRIP, at the beginning of the Holocene best explains the change from the Younger Dryas highstand to early Holocene lowstand conditions in the Dasht-e Arjan wetland. However, a contribution of the meltwater inflow from small local glaciers in the catchment basin is not excluded.

scholarly journals Coffee, Migration and Climatic Changes: Challenging Adaptation Dichotomic Narratives in a Transborder Region

2019 ◽  
Vol 8 (12) ◽  
pp. 323
Author(s):  
Celia Ruiz-de-Oña ◽  
Patricia Rivera-Castañeda ◽  
Yair Merlín-Uribe
Keyword(s):  
Climate Change ◽  
Regional Scale ◽  
Climatic Changes ◽  
Local Scale ◽  
Border Region ◽  
Central American ◽  
Adaptation Policy ◽  
Cross Border ◽  
Coffee Farmers

The narratives of migration as adaptation and in situ adaptation are well established in mainstream adaptation policy and are usually presented as independent and opposing trends of action. A common and fundamental element of such narratives is the depoliticized conception of both migration and adaptation. Using a trans-scalar approach, we address the migration–coffee–climate change nexus: first at a regional scale, at the conflictive border of Guatemala–Mexico, to show the contradiction between the current Central American migratory crisis and the narrative of migration as adaptation; second, at a local scale and from an ethnographic perspective, we focus on the process of in situ adaptation in shade-grown coffee plots of smallholder coffee farmers in the Tacaná Volcano cross-border region, between Chiapas and Guatemala. We argue that the dichotomy “in situ adaptation” versus “migration as adaptation” is not useful to capture the intertwined and political nature of both narratives, as illustrated in the case of the renovation of smallholders’ coffee plots in a context of climatic changes. We provide elements to contribute towards the repolitization of adaptation from an integral perspective.

scholarly journals Some aspects of the last glaciation in the Mazury Lake District (north-eastern Poland)

2013 ◽  
Vol 53 (1) ◽  
pp. 3-8 ◽  
Author(s):  
Katarzyna Pochocka-Szwarc
Keyword(s):  
Ice Sheet ◽  
Late Glacial ◽  
Climatic Changes ◽  
Lake District ◽  
Last Glaciation ◽  
North Eastern ◽  
Melt Water ◽  
History Of ◽  
Organic Sediments ◽  
Late Glacial And Holocene

ABSTRACT The morphology of the Mazury Lake District (north-eastern Poland) dates from 24-19 ka (main stadial of the youngest Vistulian glaciation). During this last glacial maximum (MIS 2) a belt with lacustrine basins was formed when the ice sheet retreated at the end of the Pomeranian phase. The ice-sheet retreat is morphologically also expressed by the occurrence of end moraines. The study area is situated in the Skaliska Basin, in the northern part of the Lake District (near the Polish/ Russian border), at the periphery of zone with end moraines. Originally the basin was an ice-dammed depression filled with melt water; the water flowed out into the developing Pregoła valley when the ice retreated and did no longer dam off the depression. The basin, which is surrounded by hill-shaped moraines, is filled now with Late Glacial and Holocene glaciolacustrine sediments. The organic sediments of the basin record the history of the Late Glacial and Holocene climatic changes in this region.

scholarly journals Modeling fire danger in data-poor regions: a case study from the Russian Far East

2009 ◽  
Vol 18 (1) ◽  
pp. 19 ◽  
Author(s):  
Tatiana V. Loboda
Keyword(s):  
Human Life ◽  
Russian Far East ◽  
Regional Scale ◽  
Far East ◽  
Fire Danger ◽  
Data Sources ◽  
Weighted Averaging ◽  
Remotely Sensed Data ◽  
Fire Activity ◽  
The Russian Far East

Wildland fire is a widespread phenomenon that affects how many ecosystems function and often threatens human life and property. Development of fire danger rating systems, aimed at identifying critical periods of high fire danger at early stages of its occurrence, is an important step for proactive fire and resource management. Development of such systems relies on long-term records of fire occurrence as well as numerous data sources for supporting information, but accurate and spatially explicit information is not available in many regions of the world affected by fire. Global satellite systems are becoming a major source of information for data-poor regions. The present paper describes a framework for modeling fire danger at a regional scale using publicly available data sources and global satellite imaging. It details a fuzzy logic-driven fire danger model developed for the Russian Far East using remotely sensed data. Fire activity recorded by the MODIS (Moderate Resolution Imaging Spectroradiometer) active fire product was analyzed for 2001–05 as a function of various parameters. Model performance was evaluated against 2006 data. Fire danger was evaluated within the model using the ordered weighted averaging approach with fuzzification. The model produces three scenarios. All output model scenarios provide a meaningful representation of fire danger levels in the region with the ‘trade-off’ scenario being the most applicable to mapping fire danger during low fire activity seasons.

Late Holocene precipitation variability recorded in the sediments of Reloncaví Fjord (41°S, 72°W), Chile

2015 ◽  
Vol 84 (1) ◽  
pp. 21-36 ◽  
Author(s):  
Lorena Rebolledo ◽  
Carina B. Lange ◽  
Sébastien Bertrand ◽  
Práxedes Muñoz ◽  
Marco Salamanca ◽  
...  
Keyword(s):  
Late Holocene ◽  
Sediment Cores ◽  
Southern Annular Mode ◽  
Organic Carbon Content ◽  
Diatom Assemblages ◽  
Chilean Patagonia ◽  
Precipitation Seasonality ◽  
Rhizosolenia Setigera ◽  
First Occurrence ◽  
Instrumental Records

We present reconstructions of late Holocene changes in the source of organic matter and siliceous export production in the Relocanví Fjord (41°S, 72°W), Northern Chilean Patagonia, based on organic carbon content, δ13Corg, N/C ratio, diatom assemblages and biogenic silica contents from three sediment cores. The age models are based on a combination of 210Pb profiles, AMS 14C dating, and on the first occurrence of the diatom Rhizosolenia setigera f. pungens, as a stratigraphic marker in the fjords. The cores span the last 300 to 700 yr. Diatoms dominate the siliceous assemblages in the three cores (98% on average). Our results suggest that precipitation seasonality in the region of Reloncaví was high in CE 1300–1400 and CE 1700–1850, with a clear decreasing trend since CE 1850. The latter trend is in agreement with instrumental records and tree-ring reconstructions. These fluctuations seem to be associated with the Southern Annular Mode (SAM).

scholarly journals Climatic and in-cave influences on δ18O and δ13C in a stalagmite from northeastern India through the last deglaciation

2017 ◽  
Vol 88 (3) ◽  
pp. 458-471 ◽  
Author(s):  
Franziska A. Lechleitner ◽  
Sebastian F.M. Breitenbach ◽  
Hai Cheng ◽  
Birgit Plessen ◽  
Kira Rehfeld ◽  
...  
Keyword(s):  
Late Glacial ◽  
Masking Effect ◽  
Last Deglaciation ◽  
Local Conditions ◽  
The Holocene ◽  
Oxygen And Carbon Isotope ◽  
Ne India ◽  
Precipitation Seasonality ◽  
Stable Oxygen ◽  
The Last Deglaciation

AbstractNortheastern (NE) India experiences extraordinarily pronounced seasonal climate, governed by the Indian summer monsoon (ISM). The vulnerability of this region to floods and droughts calls for detailed and highly resolved paleoclimate reconstructions to assess the recurrence rate and driving factors of ISM changes. We use stable oxygen and carbon isotope ratios (δ18O and δ13C) from stalagmite MAW-6 from Mawmluh Cave to infer climate and environmental conditions in NE India over the last deglaciation (16–6ka). We interpret stalagmite δ18O as reflecting ISM strength, whereas δ13C appears to be driven by local hydroclimate conditions. Pronounced shifts in ISM strength over the deglaciation are apparent from the δ18O record, similarly to other records from monsoonal Asia. The ISM is weaker during the late glacial (LG) period and the Younger Dryas, and stronger during the Bølling-Allerød and Holocene. Local conditions inferred from the δ13C record appear to have changed less substantially over time, possibly related to the masking effect of changing precipitation seasonality. Time series analysis of the δ18O record reveals more chaotic conditions during the late glacial and higher predictability during the Holocene, likely related to the strengthening of the seasonal recurrence of the ISM with the onset of the Holocene.

Sign in / Sign up

Export Citation Format

Share Document