scholarly journals A importância da acção do frio do Quaternário final em Portugal e suas implicações nas morfodinâmicas de vertente.

2012 ◽  
Vol 5 (2) ◽  
pp. 421
Author(s):  
António Sousa Pedrosa
Keyword(s):  
Little Ice Age ◽  
Late Quaternary ◽  
Climatic Conditions ◽  
Ice Age ◽  
Glacial Deposits ◽  
Central Portugal

Resumo   De entre os  factores que tiveram maior influência na evolução do relevo de Portugal no decurso final do Quaternário é incontestável que o frio e os processos que lhe estão associados tiveram um papel muito importante na modelação das formas de relevo. Neste trabalho procuraremos fazer uma síntese dos principais aspectos da evolução das vertentes relacionados com os frio, inferir através dos vestígios que chegaram até ao nossos dias quais as condições morfo-climáticas em que ocorreram e quais os processos que lhes estavam encontravam associados. Realçamos assim o papel da acção dos glaciares nas áreas onde ocorreram assim como a importância dos processos periglaciares na evolução das vertentes. O período tardiglaciar também se mostrou marcante na dinâmica de vertentes tendo mobilizado e remobilizado muito material nas vertentes através de solifluxões generalizadas levando muitas delas à sua regularização. O período conhecido como a pequena idade do gelo também deixou as suas marcas na dinâmica das vertentes às quais se associam as escombreiras de gravidade. Por fim enfatizamos um pouco o papel do frio na actual morfodinâmica de vertentes no Norte de Centro de Portugal.   Palavras-chave: Norte de Portugal; Montanhas, depósitos glaciares, depósitos periglaciares, dinâmica de vertentes Summary   Among the factors that most influenced the evolution of the relief of Portugal during the late Quaternary is incontestable that the cold and the processes associated with it had a very important role in modeling the forms of relief. In this paper, we will try to summarize the importance that the cold had on the evolution of slopes, inferred through the vestiges that have come down to our day, which morpho-climatic conditions in which they occur, and also what processes if they were associated with. Thus enhancing the role of action in areas where glaciers have occurred and the importance of periglacial processes in the evolution of the slopes. In tardiglaciar the dynamics of slopes was very active and mobilized a lot of material through the process of solifluction regularized many of them. The period known as the Little Ice Age has also left its mark on the dynamic slopes which relate to tailings heaps of gravity. Finally we emphasize the role of cold in the current slopes of morphodynamics in north and central Portugal.   Keywords: North of Portugal; mountains, glacial deposits, periglacial deposits, morphodynamics of slopes 

scholarly journals Was the Little Ice Age the coolest Holocene climatic period in the Italian central Alps?

2019 ◽  
Vol 44 (4) ◽  
pp. 495-513 ◽  
Author(s):  
Andrea Zerboni ◽  
Guido S Mariani ◽  
Lanfredo Castelletti ◽  
Elena S Ferrari ◽  
Marco Tremari ◽  
...  
Keyword(s):  
Iron Age ◽  
Little Ice Age ◽  
Late Quaternary ◽  
Climatic Conditions ◽  
Ice Age ◽  
Central Alps ◽  
Temperature Changes ◽  
Medium Resolution ◽  
Climatic Period ◽  
Pedogenetic Processes

The Estimation of the relative intensity of different cold periods occurring during the Late Quaternary is a difficult task, particularly in non-glaciated mountain landscapes and where high- to medium-resolution archives for proxy data are lacking. In this paper, we study a Holocene polycyclic soil sequence in the central Alps (Val Cavargna, Northern Italy) to estimate climatic parameters (specifically Temperature) changes in non-glaciated, high altitude environments. We investigate this key site through palaeopedological and micromorphological analyses in order to understand phases of soil development and detect hidden evidence of cold conditions during its formation. Three phases of pedogenesis can be recognized and attributed in time to different periods during the Holocene. Pedogenetic phases were separated by two truncation and deposition episodes related to the reactivation of slope processes under cold conditions at the onset of the Neoglacial and the Iron Age Cold Epoch, respectively. Micromorphological evidence of frost action in the soil can instead relate to pedogenetic processes acting in the Little Ice Age. The different expression of these three cold periods corresponds to changes in climatic conditions, pointing to the Little Ice Age as a cooler/drier period in comparison to the preceding ones.

scholarly journals Rapid reorganization in ocean biogeochemistry off Peru towards the end of the Little Ice Age

2009 ◽  
Vol 6 (5) ◽  
pp. 835-848 ◽  
Author(s):  
D. Gutiérrez ◽  
A. Sifeddine ◽  
D. B. Field ◽  
L. Ortlieb ◽  
G. Vargas ◽  
...  
Keyword(s):  
Little Ice Age ◽  
Decadal Variability ◽  
Late Quaternary ◽  
Walker Circulation ◽  
Rapid Expansion ◽  
Ice Age ◽  
Ecosystem Structure ◽  
Ocean Biogeochemistry ◽  
Ocean Ecosystem ◽  
Abrupt Shifts

Abstract. Climate and ocean ecosystem variability has been well recognized during the twentieth century but it is unclear if modern ocean biogeochemistry is susceptible to the large, abrupt shifts that characterized the Late Quaternary. Time series from marine sediments off Peru show an abrupt centennial-scale biogeochemical regime shift in the early nineteenth century, of much greater magnitude and duration than present day multi-decadal variability. A rapid expansion of the subsurface nutrient-rich, oxygen-depleted waters resulted in the present-day higher biological productivity, including pelagic fish. The shift was likely driven by a northward migration of the Intertropical Convergence Zone and the South Pacific Subtropical High to their present day locations, coupled with a strengthening of Walker circulation, towards the end of the Little Ice Age. These findings reveal the potential for large reorganizations in tropical Pacific climate with immediate effects on ocean biogeochemical cycling and ecosystem structure.

scholarly journals Simulated retreat of Jakobshavn Isbræ since the Little Ice Age controlled by geometry

2018 ◽  
Vol 12 (7) ◽  
pp. 2249-2266 ◽  
Author(s):  
Nadine Steiger ◽  
Kerim H. Nisancioglu ◽  
Henning Åkesson ◽  
Basile de Fleurian ◽  
Faezeh M. Nick
Keyword(s):  
Little Ice Age ◽  
Ice Age ◽  
Climate Forcing ◽  
Relative Role ◽  
Regional Warming ◽  
History Of ◽  
The Impact ◽  
Term Response

Abstract. Rapid retreat of Greenland's marine-terminating glaciers coincides with regional warming trends, which have broadly been used to explain these rapid changes. However, outlet glaciers within similar climate regimes experience widely contrasting retreat patterns, suggesting that the local fjord geometry could be an important additional factor. To assess the relative role of climate and fjord geometry, we use the retreat history of Jakobshavn Isbræ, West Greenland, since the Little Ice Age (LIA) maximum in 1850 as a baseline for the parameterization of a depth- and width-integrated ice flow model. The impact of fjord geometry is isolated by using a linearly increasing climate forcing since the LIA and testing a range of simplified geometries. We find that the total length of retreat is determined by external factors – such as hydrofracturing, submarine melt and buttressing by sea ice – whereas the retreat pattern is governed by the fjord geometry. Narrow and shallow areas provide pinning points and cause delayed but rapid retreat without additional climate warming, after decades of grounding line stability. We suggest that these geometric pinning points may be used to locate potential sites for moraine formation and to predict the long-term response of the glacier. As a consequence, to assess the impact of climate on the retreat history of a glacier, each system has to be analyzed with knowledge of its historic retreat and the local fjord geometry.

scholarly journals Record of the Climatic Variability and the Sedimentary Dynamics during the Last Two Millennia at Sebkha Dkhila, Eastern Tunisia

ISRN Geology ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Elhoucine Essefi ◽  
Jamel Touir ◽  
Mohamed Ali Tagorti ◽  
Chokri Yaich
Keyword(s):  
Little Ice Age ◽  
Climatic Variability ◽  
Low Frequency ◽  
Climatic Conditions ◽  
Ice Age ◽  
Global Changes ◽  
Medieval Climatic Anomaly ◽  
Grey Scale ◽  
Sedimentary Dynamics ◽  
The Last Two Millennia

This paper aimed to study the record of the climatic variability during the last two millennia within the sebkha of Dkhila. Six climatic stages were recognized along the 104 cm core: the Warming Present (WP), the Late Little Ice Age (Late LIA), the Early Little Ice Age (ELIA), the Medieval Climatic Anomaly (MCA), the Dark Age (DA), and the Roman Warm Period (RWP). The WP stretches along the uppermost 1 cm with a high grey scale as sign of a dry climate. The Late LIA is located between 1 cm and 6 cm. The ELIA is located between 6 cm and 40 cm. The MCA spanning from 40 cm to 72 cm is marked by a sharp increase of the GS revealing a wet period. The DA appears along the part between 72 cm and 84 cm; a shift from light to dark sediments is recorded. The RWP appears between 84 cm and 104 cm. Based on the grain size distribution, two low frequency cycles were identified indicating radical global changes of climatic conditions, the differential tectonics, and the groundwater fluctuations. On the other hand, high frequency cycles indicate local modifications of the climatic conditions.

scholarly journals Late Holocene environmental reconstructions and the implications on flood events, typhoon patterns, and agriculture activities in NE Taiwan

2014 ◽  
Vol 10 (3) ◽  
pp. 1977-2009 ◽  
Author(s):  
L.-C. Wang ◽  
H. Behling ◽  
T.-Q. Lee ◽  
H.-C. Li ◽  
C.-A. Huh ◽  
...  
Keyword(s):  
Little Ice Age ◽  
Phase 1 ◽  
Warm Pool ◽  
Climatic Conditions ◽  
Environmental Stability ◽  
Ice Age ◽  
Flood Events ◽  
Hydrological Conditions ◽  
Enso Events ◽  
The Pacific

Abstract. In this study, we reconstructed the paleoenvironmental changes from a sediment archive of the floodplain lake in Ilan Plain of NE Taiwan on multi-decadal resolution for the last ca. 1900 years. On the basis of pollen and diatom records, we evaluated the record of past vegetation, floods, typhoons and agriculture activities of this area, which is sensitive to the hydrological conditions of the West Pacific. High sedimentation rates with low microfossil preservations reflected multiple flood events and humid climatic conditions during 100–1400 AD. A shortly interrupted dry phase can be found during 940–1010 AD. The driest phase corresponds to the Little Ice Age phase 1 (LIA1, 1400–1620 AD) with less disturbance by flood events, which enhanced the occurrence of wetlands (Cyperaceae) and diatom depositions. Humid phases with frequent typhoons are inferred by high percentages of Lagerstroemia and high ratios of planktonic/benthic diatoms, respectively, during 500–700 AD and Little Ice Age phase 2 (LIA2, 1630–1850 AD). The occurrences of cultivated Poaceae (Oryza) during 1250–1300 AD and the last ~400 years, reflect agriculture activities, which seems to implicate strongly with the environmental stability. Finally, we found flood events which dominated during the El Niño-like stage, but dry events as well as frequent typhoon events happened during the La Niña-like stage. After comparing our results with the reconstructed proxy for tropical hydrological conditions, we suggested that the local hydrology in coastal East Asia were strongly affected by the typhoon-triggered heavy rainfalls which were influenced by the variation of global temperature, expansion of the Pacific warm pool and intensification of ENSO events.

scholarly journals Rapid reorganization in ocean biogeochemistry off Peru towards the end of the Little Ice Age

2008 ◽  
Vol 5 (5) ◽  
pp. 3919-3943 ◽  
Author(s):  
D. Gutiérrez ◽  
A. Sifeddine ◽  
D. B. Field ◽  
L. Ortlieb ◽  
G. Vargas ◽  
...  
Keyword(s):  
Little Ice Age ◽  
Decadal Variability ◽  
Late Quaternary ◽  
Walker Circulation ◽  
Rapid Expansion ◽  
Ice Age ◽  
Ecosystem Structure ◽  
Ocean Biogeochemistry ◽  
Ocean Ecosystem ◽  
Abrupt Shifts

Abstract. Climate and ocean ecosystem variability has been well recognized during the twentieth century but it is unclear if modern ocean biogeochemistry is susceptible to the large, abrupt shifts that characterized the Late Quaternary. Time series from marine sediments off Peru show an abrupt centennial-scale biogeochemical regime shift in the early nineteenth century, of much greater magnitude and duration than present day multi-decadal variability. A rapid expansion of the subsurface nutrient-rich, oxygen-depleted waters resulted in higher biological productivity, including pelagic fish. The shift was likely driven by a northward migration of the Intertropical Convergence Zone and the South Pacific Subtropical High to their present day locations, coupled with a strengthening of Walker circulation, towards the end of the Little Ice Age. These findings reveal the potential for large reorganizations in tropical Pacific climate with immediate effects on ocean biogeochemical cycling and ecosystem structure.

scholarly journals Recent Climatic Mass Balance of the Schiaparelli Glacier at the Monte Sarmiento Massif and Reconstruction of Little Ice Age Climate by Simulating Steady-State Glacier Conditions

Geosciences ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 272
Author(s):  
Stephanie Suzanne Weidemann ◽  
Jorge Arigony-Neto ◽  
Ricardo Jaña ◽  
Guilherme Netto ◽  
Inti Gonzalez ◽  
...  
Keyword(s):  
Steady State ◽  
Mass Balance ◽  
Air Temperature ◽  
Little Ice Age ◽  
Similar Rate ◽  
Climatic Conditions ◽  
Ice Age ◽  
Balance Model ◽  
Climate Conditions ◽  
Recent Climate

The Cordillera Darwin Icefield loses mass at a similar rate as the Northern and Southern Patagonian Icefields, showing contrasting individual glacier responses, particularly between the north-facing and south-facing glaciers, which are subject to changing climate conditions. Detailed investigations of climatic mass balance processes on recent glacier behavior are not available for glaciers of the Cordillera Darwin Icefield and surrounding icefields. We therefore applied the coupled snow and ice energy and mass balance model in Python (COSIPY) to assess recent surface energy and mass balance variability for the Schiaparelli Glacier at the Monte Sarmiento Massif. We further used COSIPY to simulate steady-state glacier conditions during the Little Ice Age using information of moraine systems and glacier areal extent. The model is driven by downscaled 6-hourly atmospheric data and high resolution precipitation fields, obtained by using an analytical orographic precipitation model. Precipitation and air temperature offsets to present-day climate were considered to reconstruct climatic conditions during the Little Ice Age. A glacier-wide mean annual climatic mass balance of −1.8 ± 0.36 m w.e. a − 1 was simulated between between April 2000 and March 2017. An air temperature decrease between −0.9 ° C and −1.7 ° C in combination with a precipitation offset of up to +60% to recent climate conditions is necessary to simulate steady-state conditions for Schiaparelli Glacier in 1870.

Variability to sedimentary dynamics and climatic conditions during the last two millennia at sebkha Souassi in eastern Tunisia

2013 ◽  
Vol 20 (1) ◽  
Author(s):  
Elhoucine Essefi ◽  
Hayet Ben Jmaa ◽  
Jamel Touir ◽  
Mohamed Ali Tagortig ◽  
Chokri Yaicha
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Little Ice Age ◽  
Climatic Variability ◽  
Climatic Conditions ◽  
Ice Age ◽  
Global Changes ◽  
Sedimentary Dynamics ◽  
The Last Two Millennia

AbstractThis paper covers work intended to study the interplay of sedimentary dynamics and climatic variability over the last two millennia within Tunisia’s sebkha Souassi. Based on the Visual Core Description, and magnetic susceptibility, we date the core from sebkha Souassi to the last two millennia. Genetic grain-size distribution then provided a basis for the identification of six climatic stages, i.e. the Warming Present (WP), the Late Little Ice Age (Late LIA), the Early Little Ice Age (ELIA), the Medieval Climatic Anomaly (MCA), the Dark Ages (DA), and the Roman Warm Period (RWP). The WP stretches across the uppermost 3 cm, with a high grey scale indicating a dry climate. The Late LIA is located between 3 and 7 cm, and the ELIA between 7 and 28 cm. Intermediate values for GS indicate that this stage may be classified as moderate. The MCA spanning from 28 to 40 cm is marked by a sharp decrease in GS indicative of a wet period. The DA appear along the part between 40 and 79 cm, a shift from light to dark sediments being recorded. The RWP in turn appears between 79 and 114 cm. Based on the grain-size distribution, two low-frequency cycles were identified, indicating radical global changes in climatic conditions, differential tectonics and groundwater fluctuations. High-frequency cycles in turn attest to local modifications of climatic conditions.

Evidence for glacial deposits during the Little Ice Age in Ny-Alesund, western Spitsbergen

2019 ◽  
Vol 129 (1) ◽  
Author(s):  
Zhongkang Yang ◽  
Wenqing Yang ◽  
Linxi Yuan ◽  
Yuhong Wang ◽  
Liguang Sun
Keyword(s):  
Little Ice Age ◽  
Ice Age ◽  
Glacial Deposits
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