Long-Term Solar Forcing of the Holocene Climate

1998 ◽  
Vol 9 (6) ◽  
pp. 741-744 ◽  
Author(s):  
W. Karlén
Keyword(s):  
Solar Forcing ◽  
Holocene Climate ◽  
The Holocene

Centennial to millennial-scale variability of Holocene climate and environmental dynamics in the western Mediterranean (Lake Sidi Ali, Middle Atlas, Morocco)

2021 ◽  
Author(s):  
Johannes Schmidt ◽  
Cathleen Kertscher ◽  
Markus Reichert ◽  
Helen Ballasus ◽  
Birgit Schneider ◽  
...  
Keyword(s):  
North Atlantic ◽  
Climate Changes ◽  
Western Mediterranean ◽  
Future Climate ◽  
Holocene Climate ◽  
The Holocene ◽  
The North ◽  
Middle Atlas ◽  
Environmental Responses

<p>The Western Mediterranean region including the North African desert margin is considered one of the most sensitive areas to future climate changes. In order to refine long-term scenarios for hydrological and environmental responses to future climate changes in this region, it is important to improve our knowledge about past environmental responses to climatic variability at centennial to millennial timescales. During the last two decades, the recovery and compilation of Holocene records from the subtropical North Atlantic and the Mediterranean Sea have improved our knowledge about millennial-scale variability of the Western Mediterranean palaeoclimate. The variabilities appear to affect regional precipitation patterns and environmental systems in the Western Mediterranean, but the timescales, magnitudes and forcing mechanisms remain poorly known. To compare the changes in Holocene climate variability and geomorphological processes across temporal scales, we analysed a 19.63-m long sediment record from Lake Sidi Ali (33°03’ N, 5°00’ W, 2080 m a.s.l.) in the sub-humid Middle Atlas that spans the last 12,000 years (23 pollen-based radiocarbon dates accompanied with <sup>210</sup>Pb results). We use calibrated XRF core scanning records with an annual to sub-decadal resolution to disentangle the complex interplay between climate changes and environmental dynamics during the Holocene. Data exploration techniques and time series analysis (Redfit, Wavelet) revealed long-term changes in lake behaviour. Three main proxy groups were identified (temperature proxies: 2ky, 1ky and 0.7ky cycles; sediment dynamic proxies: 3.5ky, 1.5ky cycles; hydrological proxies: 1.5ky, 1.2ky, 0.17ky cycles). For example, redox sensitive elements Fe and Mn show 1ky cycles and higher values in the Early Holocene and 1.5ky cycles and lower values in the Mid- to Late Holocene. All groups show specific periodicities throughout the Holocene, demonstrating their particular climatic and geomorphological dependencies. Furthermore, we discuss these periodicities relating to global and hemispheric drivers, such as the North Atlantic Oscillation (NAO), El-Niño Southern Oscillation (ENSO), Innertropical Convergence Zone variability (ITCZ) and North Atlantic cold relapses (Bond events).</p>

Can we expect pristine mountain peatland ecosystems in Central Europe? Evidence from multi-proxy palaeoecological studies on the Holocene peatland development

2020 ◽  
Author(s):  
Mariusz Gałka ◽  
Klaus-Holger Knorr ◽  
Andrei-Cosmin Diaconu ◽  
Angelica Feurdean ◽  
Adam Hölzer ◽  
...  
Keyword(s):  
Plant Communities ◽  
Stable Carbon Isotopes ◽  
Human Impacts ◽  
Holocene Climate ◽  
Forming Process ◽  
The Holocene ◽  
Climate Shifts ◽  
Recent Climate ◽  
European Mountains

<p>The Holocene climate shifts had a significant impact on the development of ombrotrophic peatland ecosystems located in various biogeographic zones. Disturbances of the plant communities at peatlands ecosystems took place also due to intensified human activities in the past several centuries, that include peat excavation, fires, as well as deposition of dust and pollutants on peatland surfaces. This merger of natural and human impacts has led to direct hydrological and biochemical disturbances that triggered changes in plant populations, e.g. often leading to the decline of some species, such as Sphagnum austinii in Great Britain.</p><p>The knowledge about the development of peatlands across mountain ranges in Europe is still poor. Determining the resilience of peatland vegetation to disturbance is an important and significant task to aid further protection and management of the entire range of ombrotrophic peatlands found in the European mountains, from destroyed or restored to pristine. We carried out high-resolution, multi-proxy studies including plant macrofossils, pollen, testate amoebae, geochemical analyses (XRF and stable carbon isotopes), micro- and macro-charcoal, supported by radiocarbon dating, on replicate peat cores from five well-preserved ombrotrophic peatlands across Europe where peat-forming process is active. The studied peatlands are located along an east west gradient in the Central and Western Europe: Eastern Carpathian Mts. (Calimani-Gurghiu-Harghita, Romania; Bieszczady, Poland), Harz Mts. and Schwarzwald Mts. (Germany), and Vosges Mts (France). In our palaeocological studies we aimed to: i) reconstruct long-term local (mainly Sphagnum populations) and regional (forest communities) vegetation changes at and around selected bogs; ii) reconstruct long-term palaeohydrological shifts; iii) assess mountain peatland ecosystems resilience to Holocene climate shifts and disturbance by fire events and human impact (deforestation, dust and pollution).</p><p>Based on our results, we found that: i) despite human activites (pollutants and dust deposition, drainage) some of the mountain peatlands remained in a pristine state, however some plant communities had changed; ii) plant communities composed mainly by Sphagnum species, could repeatedly self-regenerate via autogenic processes following a decline in stressors; iii) recent climate warming has stimulated the spreading of some species indicative of more dry habitats; vi) lack of macrocharcoal in the peat layers indicate that fires did not play a significant role in the development or evolution of local peatland communities. Results from our studies show that palaeoecological records play an important role for the determination of present peatland ecosystem stage and reference conditions for the restoration of damaged ombrotrophic peatlands in European mountains.</p><p>The research has received support National Science Centre (Poland) grant No UMO-2016/23/B/ST10/00762 (PI: Mariusz Gałka).</p>

scholarly journals Solar cycles or random processes? Evaluating solar variability in Holocene climate records

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
T. Edward Turner ◽  
Graeme T. Swindles ◽  
Dan J. Charman ◽  
Peter G. Langdon ◽  
Paul J. Morris ◽  
...  
Keyword(s):  
Solar Variability ◽  
Solar Cycles ◽  
Climate Data ◽  
Critical Approach ◽  
Solar Forcing ◽  
Holocene Climate ◽  
Proxy Records ◽  
Wide Range ◽  
Solar Type

Abstract Many studies have reported evidence for solar-forcing of Holocene climate change across a range of archives. These studies have compared proxy-climate data with records of solar variability (e.g. 14C or 10Be), or have used time series analysis to test for the presence of solar-type cycles. This has led to some climate sceptics misrepresenting this literature to argue strongly that solar variability drove the rapid global temperature increase of the twentieth century. As proxy records underpin our understanding of the long-term processes governing climate, they need to be evaluated thoroughly. The peatland archive has become a prominent line of evidence for solar forcing of climate. Here we examine high-resolution peatland proxy climate data to determine whether solar signals are present. We find a wide range of significant periodicities similar to those in records of solar variability: periods between 40–100 years, and 120–140 years are particularly common. However, periodicities similar to those in the data are commonly found in random-walk simulations. Our results demonstrate that solar-type signals can be the product of random variations alone, and that a more critical approach is required for their robust interpretation.

A quantitative synthesis of Holocene vegetation change in Nigeria (Western Africa)

The Holocene ◽  
2021 ◽  
pp. 095968362110331
Author(s):  
Matthew Adesanya Adeleye ◽  
Simon Edward Connor ◽  
Simon Graeme Haberle
Keyword(s):  
Vegetation Change ◽  
Climatic Changes ◽  
The Holocene ◽  
Continental Scale ◽  
Western Africa ◽  
Chord Distance ◽  
Quantitative Synthesis ◽  
Climatic Regime ◽  
Pollen Records

Understanding long-term (centennial–millennial scale) ecosystem stability and dynamics are key to sustainable management and conservation of ecosystem processes under the currently changing climate. Fossil pollen records offer the possibility to investigate long-term changes in vegetation composition and diversity on regional and continental scales. Such studies have been conducted in temperate systems, but are underrepresented in the tropics, especially in Africa. This study attempts to synthesize pollen records from Nigeria (tropical western Africa) and nearby regions to quantitatively assess Holocene regional vegetation changes (turnover) and stability under different climatic regimes for the first time. We use the squared chord distance metric (SCD) to assess centennial-scale vegetation turnover in pollen records. Results suggest vegetation in most parts of Nigeria experienced low turnover under a wetter climatic regime (African Humid Period), especially between ~8000 and 5000 cal year BP. In contrast, vegetation turnover increased significantly under the drier climatic regime of the late-Holocene (between ~5000 cal year BP and present), reflecting the imp role of moisture changes in tropical west African vegetation dynamics during the Holocene. Our results are consistent with records of vegetation and climatic changes in other parts of Africa, suggesting the Holocene pattern of vegetation change in Nigeria is a reflection of continental-scale climatic changes.

Long-term summer warming trend during the Holocene in central Asia indicated by alpine peat α-cellulose δ13C record

2019 ◽  
Vol 203 ◽  
pp. 56-67 ◽  
Author(s):  
Zhiguo Rao ◽  
Chao Huang ◽  
Luhua Xie ◽  
Fuxi Shi ◽  
Yan Zhao ◽  
...  
Keyword(s):  
Central Asia ◽  
Warming Trend ◽  
The Holocene ◽  
Summer Warming

scholarly journals The Holocene thermal maximum in the Nordic Seas: the impact of Greenland Ice Sheet melt and other forcings in a coupled atmosphere–sea-ice–ocean model

2013 ◽  
Vol 9 (4) ◽  
pp. 1629-1643 ◽  
Author(s):  
M. Blaschek ◽  
H. Renssen
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Early Holocene ◽  
Surface Cooling ◽  
Holocene Climate ◽  
Nordic Seas ◽  
The Holocene ◽  
Holocene Thermal Maximum ◽  
Thermal Maximum ◽  
The Impact

Abstract. The relatively warm early Holocene climate in the Nordic Seas, known as the Holocene thermal maximum (HTM), is often associated with an orbitally forced summer insolation maximum at 10 ka BP. The spatial and temporal response recorded in proxy data in the North Atlantic and the Nordic Seas reveals a complex interaction of mechanisms active in the HTM. Previous studies have investigated the impact of the Laurentide Ice Sheet (LIS), as a remnant from the previous glacial period, altering climate conditions with a continuous supply of melt water to the Labrador Sea and adjacent seas and with a downwind cooling effect from the remnant LIS. In our present work we extend this approach by investigating the impact of the Greenland Ice Sheet (GIS) on the early Holocene climate and the HTM. Reconstructions suggest melt rates of 13 mSv for 9 ka BP, which result in our model in an ocean surface cooling of up to 2 K near Greenland. Reconstructed summer SST gradients agree best with our simulation including GIS melt, confirming that the impact of the early Holocene GIS is crucial for understanding the HTM characteristics in the Nordic Seas area. This implies that modern and near-future GIS melt can be expected to play an active role in the climate system in the centuries to come.

scholarly journals Three distinct Holocene intervals of stalagmite deposition and nondeposition revealed in NW Madagascar, and their paleoclimate implications

2017 ◽  
Vol 13 (12) ◽  
pp. 1771-1790 ◽  
Author(s):  
Ny Riavo Gilbertinie Voarintsoa ◽  
Loren Bruce Railsback ◽  
George Albert Brook ◽  
Lixin Wang ◽  
Gayatri Kathayat ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
High Resolution ◽  
Late Holocene ◽  
Intertropical Convergence Zone ◽  
Convergence Zone ◽  
High Resolution Data ◽  
The Holocene ◽  
Middle Holocene ◽  
Resolution Data

Abstract. Petrographic features, mineralogy, and stable isotopes from two stalagmites, ANJB-2 and MAJ-5, respectively from Anjohibe and Anjokipoty caves, allow distinction of three intervals of the Holocene in NW Madagascar. The Malagasy early Holocene (between ca. 9.8 and 7.8 ka) and late Holocene (after ca. 1.6 ka) intervals (MEHI and MLHI, respectively) record evidence of stalagmite deposition. The Malagasy middle Holocene interval (MMHI, between ca. 7.8 and 1.6 ka) is marked by a depositional hiatus of ca. 6500 years. Deposition of these stalagmites indicates that the two caves were sufficiently supplied with water to allow stalagmite formation. This suggests that the MEHI and MLHI intervals may have been comparatively wet in NW Madagascar. In contrast, the long-term depositional hiatus during the MMHI implies it was relatively drier than the MEHI and the MLHI. The alternating wet–dry–wet conditions during the Holocene may have been linked to the long-term migrations of the Intertropical Convergence Zone (ITCZ). When the ITCZ's mean position is farther south, NW Madagascar experiences wetter conditions, such as during the MEHI and MLHI, and when it moves north, NW Madagascar climate becomes drier, such as during the MMHI. A similar wet–dry–wet succession during the Holocene has been reported in neighboring locations, such as southeastern Africa. Beyond these three subdivisions, the records also suggest wet conditions around the cold 8.2 ka event, suggesting a causal relationship. However, additional Southern Hemisphere high-resolution data will be needed to confirm this.

scholarly journals Agroforestry and Its Impact in Southeast Asia

2020 ◽  
Author(s):  
Christopher Hunt
Keyword(s):  
Land Management ◽  
Agroforestry Systems ◽  
Management Systems ◽  
Early Interventions ◽  
Significant Component ◽  
The Holocene ◽  
Wide Range ◽  
Vegetational Succession ◽  
Food Procurement

Research during the late 20th and early 21st centuries found that traces of human intervention in vegetation in Southeast Asian and Australasian forests started extremely early, quite probably close to the first colonization of the region by modern people around or before 50,000 years ago. It also identified what may be insubstantial evidence for the translocation of economically important plants during the latest Pleistocene and Early Holocene. These activities may reflect early experiments with plants which evolved into agroforestry. Early in the Holocene, land management/food procurement systems, in which trees were a very significant component, seem to have developed over very extensive areas, often underpinned by dispersal of starchy plants, some of which seem to show domesticated morphologies, although the evidence for this is still relatively insubstantial. These land management/food procurement systems might be regarded as a sort of precursor to agroforestry. Similar systems were reported historically during early Western contact, and some agroforest systems survive to this day, although they are threatened in many places by expansion of other types of land use. The wide range of recorded agroforestry makes categorizing impacts problematical, but widespread disruption of vegetational succession across the region during the Holocene can perhaps be ascribed to agroforestry or similar land-management systems, and in more recent times impacts on biodiversity and geomorphological systems can be distinguished. Impacts of these early interventions in forests seem to have been variable and locally contingent, but what seem to have been agroforestry systems have persisted for millennia, suggesting that some may offer long-term sustainability.

Holocene forest transformations in sandstone landscapes of the Czech Republic: Stand-scale comparison of charcoal and pollen records

The Holocene ◽  
2019 ◽  
Vol 29 (9) ◽  
pp. 1468-1479 ◽  
Author(s):  
Jan Novák ◽  
Vojtěch Abraham ◽  
Petr Šída ◽  
Petr Pokorný
Keyword(s):  
Driving Forces ◽  
Forest Succession ◽  
Environmental Gradients ◽  
Silver Fir ◽  
Pollen Record ◽  
Fire Dynamics ◽  
The Czech Republic ◽  
The Holocene ◽  
Ecosystem Changes

Stand-scale palaeoecology in sandstone landscapes provides insight into contrasting Holocene forest succession trajectories. Sharp geomorphological gradients in this investigated area, which in addition have never been deforested during the Holocene, provide a good model for upscaling the local vegetation histories to the wider territory of Central Europe. In three sandstone areas – Bohemian Paradise, Polemené hory and Broumov – we compare (1) anthracological records from archaeological stratigraphies under rockshelters with (2) pedoanthracological sequences from nearby locations in valleys, rocks and plateaus; and with (3) pollen analyses carried out in nearby peat accumulations. Taphonomical vectors discriminate the source vegetation of each proxy, however thanks to proximity of all sampling sites pollen record and charcoals from rockshelters integrate the signal from pedoanthracology. The results show that past distribution of individual arboreal taxa is clearly related to the position within local environmental gradients. All basic habitats – valleys, rocky edges and plateaus – started with the dominance of pine forest in the early Holocene. Middle Holocene witnessed expansion of spruce inside valleys and oak on plateaus. Pine has maintained its dominance on rocky edges. In the late Holocene, silver fir and beech expanded into valleys, while oak stands remained dominant on plateaus. In the High Medieval and Modern Ages, human impact triggered general spread of fir. Records indicate site-specific local histories connected to various human activities, fire dynamics and erosion. Against the background of these immediate driving forces, the long-term process of ecosystem changes has been influenced by climate of the Holocene.

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