The relative contributions of weathering and aeolian inputs to postglacial formation of Mediterranean alpine loess

Between the southern margin of the European loess belt and Sahara Desert, thin and irregularly distributed loess deposits occur in Mediterranean mountains. During the most recent deglaciation, along the Pleistocene-Holocene boundary, the deposition of glacial, periglacial and outwash sediments, was the main local source of Mediterranean alpine loess, whereas proximal alluvial planes comprised a secondary source. The mid-Holocene termination of African Humid Period and subsequent aridification of Sahara Desert occurred simultaneously with a change of the regional climate from Atlantic to Mediterranean-dominated, characterized by frequent episodes of southerly winds. This resulted to a change of the loess source, as deflation of quartz rich silts enriched in Zr during intense episodes of Sahara dust transport became more dominant. Here, a 32cm loess profile from the Plateau of Muses (PM), below the summit of Mount Olympus, Greece, is investigated on the basis of grain size, mineralogy, environmental magnetism and geochemistry. Comparisons of loess samples with glacial and periglacial deposits, enables us to differentiate relative contributions of local sources and allochthonous aeolian inputs. Calcite sand rich in feldspars makes up the glacial and periglacial clast free matrix. In contrast, PM loess is composed by clay and fine silt fractions with minor calcite sand contributions. The mineralogical matrix of loess contains quartz, phyllosilicates and mixed layer clays, while its geochemical composition contains high amounts of detrital Fe-Ti oxides and aeolian transported Al and Zr. Based on the multi-proxy approach applied here, the loess profile is partitioned in three layers. Holocene average deposition rates (~2.5 cm/ka) broadly agree with modern Sahara dust deposition (~2.0 cm/ka) and long-term postglacial Mediterranean mountain denudation rates (~0.5 cm/ka). Such low rates provided ample time for post depositional modifications, such as decalcification, deferrification and removal of K, evident from the trends of chemical weathering proxies Ca/Sr, Fe/Ti and K/Rb, respectively.

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Using the significant dust deposition event on the glaciers of Mt. Elbrus, Caucasus Mountains, Russia on 5 May 2009 to develop a method for dating and "provenancing" of desert dust events recorded in snow pack

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-1797-2013 ◽

2013 ◽

Vol 13 (4) ◽

pp. 1797-1808 ◽

Cited By ~ 14

Author(s):

M. Shahgedanova ◽

S. Kutuzov ◽

K. H. White ◽

G. Nosenko

Keyword(s):

Eastern Mediterranean ◽

Meteorological Data ◽

Source Region ◽

Secondary Source ◽

Snow Pack ◽

Dust Deposition ◽

Hysplit Model ◽

Pressure System ◽

Desert Dust ◽

Caucasus Mountains

Abstract. A significant desert dust deposition event occurred on Mt. Elbrus, Caucasus Mountains, Russia on 5 May 2009, where the deposited dust later appeared as a brown layer in the snow pack. An examination of dust transportation history and analysis of chemical and physical properties of the deposited dust were used to develop a new approach for high-resolution "provenancing" of dust deposition events recorded in snow pack using multiple independent techniques. A combination of SEVIRI red-green-blue composite imagery, MODIS atmospheric optical depth fields derived using the Deep Blue algorithm, air mass trajectories derived with HYSPLIT model and analysis of meteorological data enabled identification of dust source regions with high temporal (hours) and spatial (ca. 100 km) resolution. Dust, deposited on 5 May 2009, originated in the foothills of the Djebel Akhdar in eastern Libya where dust sources were activated by the intrusion of cold air from the Mediterranean Sea and Saharan low pressure system and transported to the Caucasus along the eastern Mediterranean coast, Syria and Turkey. Particles with an average diameter below 8 μm accounted for 90% of the measured particles in the sample with a mean of 3.58 μm, median 2.48 μm. The chemical signature of this long-travelled dust was significantly different from the locally-produced dust and close to that of soils collected in a palaeolake in the source region, in concentrations of hematite. Potential addition of dust from a secondary source in northern Mesopotamia introduced uncertainty in the "provenancing" of dust from this event. Nevertheless, the approach adopted here enables other dust horizons in the snowpack to be linked to specific dust transport events recorded in remote sensing and meteorological data archives.

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Dust emission size distribution impact on aerosol budget and radiative forcing over the Mediterranean region: a regional climate model approach

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-10545-2012 ◽

2012 ◽

Vol 12 (21) ◽

pp. 10545-10567 ◽

Cited By ~ 55

Author(s):

P. Nabat ◽

F. Solmon ◽

M. Mallet ◽

J. F. Kok ◽

S. Somot

Keyword(s):

Size Distribution ◽

Radiative Forcing ◽

Mediterranean Basin ◽

Climate Model ◽

Regional Climate ◽

Dust Emission ◽

Dust Deposition ◽

The Mediterranean ◽

Dust Distribution ◽

The Mediterranean Basin

Abstract. The present study investigates the dust emission and load over the Mediterranean basin using the coupled chemistry–aerosol–regional climate model RegCM-4. The first step of this work focuses on dust particle emission size distribution modeling. We compare a parameterization in which the emission is based on the individual kinetic energy of the aggregates striking the surface to a recent parameterization based on an analogy with the fragmentation of brittle materials. The main difference between the two dust schemes concerns the mass proportion of fine aerosol that is reduced in the case of the new dust parameterization, with consequences for optical properties. At the episodic scale, comparisons between RegCM-4 simulations, satellite and ground-based data show a clear improvement using the new dust distribution in terms of aerosol optical depth (AOD) values and geographic gradients. These results are confirmed at the seasonal scale for the investigated year 2008. This change of dust distribution has sensitive impacts on the simulated regional dust budget, notably dry dust deposition and the regional direct aerosol radiative forcing over the Mediterranean basin. In particular, we find that the new size distribution produces a higher dust deposition flux, and smaller top of atmosphere (TOA) dust radiative cooling. A multi-annual simulation is finally carried out using the new dust distribution over the period 2000–2009. The average SW radiative forcing over the Mediterranean Sea reaches −13.6 W m−2 at the surface, and −5.5 W m−2 at TOA. The LW radiative forcing is positive over the basin: 1.7 W m−2 on average over the Mediterranean Sea at the surface, and 0.6 W m−2 at TOA.

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Pace, magnitude, and nature of terrestrial climate change through the end-Permian extinction in southeastern Gondwana

Geology ◽

10.1130/g48795.1 ◽

2021 ◽

Author(s):

T.D. Frank ◽

C.R. Fielding ◽

A.M.E. Winguth ◽

K. Savatic ◽

A. Tevyaw ◽

...

Keyword(s):

Climate Change ◽

Land Surface ◽

Chemical Weathering ◽

Regional Climate ◽

Proxy Records ◽

Climate Simulations ◽

Southeastern Margin ◽

Terrestrial Environments ◽

Marine Realm ◽

Permian Extinction

Rapid climate change was a major contributor to the end-Permian extinction (EPE). Although well constrained for the marine realm, relatively few records document the pace, nature, and magnitude of climate change across the EPE in terrestrial environments. We generated proxy records for chemical weathering and land surface temperature from continental margin deposits of the high-latitude southeastern margin of Gondwana. Regional climate simulations provide additional context. Results show that Glossopteris forest-mire ecosystems collapsed during a pulse of intense chemical weathering and peak warmth, which capped ~1 m.y. of gradual warming and intensification of seasonality. Erosion resulting from loss of vegetation was short lived in the low-relief landscape. Earliest Triassic climate was ~10–14 °C warmer than the late Lopingian and landscapes were no longer persistently wet. Aridification, commonly linked to the EPE, developed gradually, facilitating the persistence of refugia for moisture-loving terrestrial groups.

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Chemical Weathering of the Southern Tibetan Plateau: Study the Geochemical Weathering Indices in the Top Soils

10.21203/rs.3.rs-106871/v1 ◽

2020 ◽

Author(s):

Xiaoyan Yang ◽

Juzhi Hou ◽

Feixue San

Keyword(s):

Climate Change ◽

Tibetan Plateau ◽

Chemical Weathering ◽

Regional Climate ◽

Lacustrine Sediment ◽

Mean Annual Temperature ◽

The Tibetan Plateau ◽

Climate Condition ◽

Weathering Indices ◽

Southern Tibetan Plateau

Abstract Continental chemical weathering has been suggested to affect the concentration of atmospheric carbon dioxide that influences global climate change at different time scales. Various indices for chemical weathering have been adopted to investigate past change in chemical weathering intensity and climate change on oceanic and lacustrine sediment archives. The reliability of the chemical weathering indices has been questioned as most sediments likely originate from multiple types of bedrock that may experience various degrees of chemical weathering and can thus be reliably robust indicators of climate and paleoclimate. Here we present Sr-type (e.g. Rb/Sr Sr/Ba) and Na-type (e.g. CIA CIW PIA CPA) chemical weathering indices for top soils across the southern Tibetan Plateau to discuss the chemical weathering characteristic in the Tibetan Plateau and to examine their response to regional climate variation. The results of chemical indices and the A-CN-K ternary plot show that the southern Tibetan Plateau is under the carbonate control of the primary chemical weathering stage with the cold-dry climate. Correlation analyses show shat Sr-type indices co-vary with mean annual temperature and annual precipitation while Na-type indices show little consistence with regional climate. The climate condition is the dominant control of Sr-type indices of top soils in the study area and the bedrock may be the dominant control for the Na-type indices. We also compared the corresponding indices at a Holocene lacustrine sediment profile in the Qaidam Basin in the northeast Tibetan Plateau with regional climatic records which strongly supports our observation in the top soils. The results of the study suggest that for the relative cold and dry climate in Tibetan Plateau the Sr-type indices are more sensitive to climate condition than Na-type indices. This suggests that the Sr-type indices are likely more suitable than Na-type indices to reflect the change of climate on the Tibetan Plateau. Caution should be taken for using the Na-type indices for reconstructing the past change in climate for the study area.

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Periodic input of dust over the Eastern Carpathians during the Holocene linked with Saharan desertification and human impact

10.5194/cp-2017-6 ◽

2017 ◽

Cited By ~ 1

Author(s):

Jack Longman ◽

Daniel Veres ◽

Vasile Ersek ◽

Ulrich Salzmann ◽

Katalin Hubay ◽

...

Keyword(s):

Testate Amoeba ◽

Dust Deposition ◽

Geochemical Composition ◽

The Holocene ◽

Carpathian Region ◽

Dust Flux ◽

Eastern Carpathians ◽

Periodic Input ◽

Balkan Region ◽

The Impact

Abstract. Reconstructions of dust flux have been used to produce valuable global records of changes in atmospheric circulation and aridity. These studies have highlighted the importance of atmospheric dust in marine and terrestrial biogeochemistry and nutrient cycling. By investigating a 10 800-year long paleoclimate archive from the Eastern Carpathians (Romania) we present the first peat record of changing dust deposition over the Holocene for the Carpathian-Balkan region. Using qualitative (XRF core scanning) and quantitative (ICP-OES) measurements of lithogenic (Fe, K, Si, Ti) elements, we identify 11 periods of major dust deposition between: 9500–9100, 8400–8100, 7720–7250, 6350–6000, 5450–5050, 4130–3770, 3450–2850, 2100–1450, 800–620, and 60 cal yr BP to present. In addition, we used testate amoeba assemblages preserved within the peat to infer local palaeohydroclimate conditions. Our record highlights several discrepancies between eastern and western European dust depositional records, and the impact of highly complex hydrological regimes in the Carpathian region. After 6100 cal yr BP, we find that the geochemical indicators of dust flux become uncoupled from the local hydrology. This coincides with the appearance of millennial-scale cycles in the dust input and changes in geochemical composition of dust. We suggest this is indicative of a shift in dust provenance from local/regional (likely loess-related) to distal (Saharan) sources which coincide with the end of the African Humid Period and the onset of Saharan desertification.

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Water-sediment interaction in the Arno- and Tiber river catchments (central Italy)

10.5194/egusphere-egu2020-21502 ◽

2020 ◽

Author(s):

Petra Diendorfer ◽

Caterina Gozzi ◽

Anna Bauer ◽

Antonella Buccianti ◽

Gerd Rantitsch ◽

...

Keyword(s):

Chemical Weathering ◽

River Sediments ◽

Central Italy ◽

River Basins ◽

Geochemical Composition ◽

Physical Weathering ◽

River Waters ◽

Hydrochemical Data ◽

Lithological Composition ◽

Landscape Attributes

The Tiber and the Arno river basins, represent the first (17,156 km2) and the second (8,228 km2) largest catchments in the peninsular Italy, respectively. The recent combined sampling (2017-2019) &#160;of river waters and sediments in the heterogeneous geological environment of the Apennines enables the assessment of the geochemical and mineralogical interaction between bedrock, river sediments and water. The mineralogical and geochemical composition of the stream sediments are related to the corresponding lithological composition of the hydrological catchment, thus assessing physical weathering within the river basins. On the other hand, chemical weathering is assessed by the analysis of hydrochemical data from the Arno and Tiber rivers and their main tributaries. Locally, anthropogenic processes overprint the natural signature and the magnetic properties of the sediments provide effective data to map those areas. The application of multivariate robust statistical techniques on the combined dataset evaluates the water-sediment interaction and their spatial properties in central Italy. The main goal of this research is to investigate how the linkage between surface waters and steam sediments chemistry can be influenced by catchment-specific properties (e.g. landscape attributes, anthropic impact and climate) through an effective comparative analysis between two of the most important Italian watersheds.

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Desert dust and anthropogenic aerosol interactions in the Community Climate System Model coupled-carbon-climate model

Biogeosciences ◽

10.5194/bg-8-387-2011 ◽

2011 ◽

Vol 8 (2) ◽

pp. 387-414 ◽

Cited By ~ 32

Author(s):

N. Mahowald ◽

K. Lindsay ◽

D. Rothenberg ◽

S. C. Doney ◽

J. K. Moore ◽

...

Keyword(s):

Carbon Cycle ◽

Climate Model ◽

Regional Climate ◽

Climate Feedback ◽

Dust Deposition ◽

Anthropogenic Aerosols ◽

Anthropogenic Aerosol ◽

Climate System Model ◽

Desert Dust ◽

The Impact

Abstract. Coupled-carbon-climate simulations are an essential tool for predicting the impact of human activity onto the climate and biogeochemistry. Here we incorporate prognostic desert dust and anthropogenic aerosols into the CCSM3.1 coupled carbon-climate model and explore the resulting interactions with climate and biogeochemical dynamics through a series of transient anthropogenic simulations (20th and 21st centuries) and sensitivity studies. The inclusion of prognostic aerosols into this model has a small net global cooling effect on climate but does not significantly impact the globally averaged carbon cycle; we argue that this is likely to be because the CCSM3.1 model has a small climate feedback onto the carbon cycle. We propose a mechanism for including desert dust and anthropogenic aerosols into a simple carbon-climate feedback analysis to explain the results of our and previous studies. Inclusion of aerosols has statistically significant impacts on regional climate and biogeochemistry, in particular through the effects on the ocean nitrogen cycle and primary productivity of altered iron inputs from desert dust deposition.

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Early-Holocene to present palaeoenvironmental shifts and short climate events from the tropical wetland and lake sediments, Kukkal Lake, Southern India: Geochemistry and palynology

The Holocene ◽

10.1177/0959683616660162 ◽

2016 ◽

Vol 27 (3) ◽

pp. 404-417 ◽

Cited By ~ 8

Author(s):

Vijayaraj Rajmanickam ◽

Hema Achyuthan ◽

Christopher Eastoe ◽

Anjum Farooqui

Keyword(s):

Tamil Nadu ◽

Chemical Weathering ◽

Warm Period ◽

Early Holocene ◽

Ice Age ◽

Terrestrial Plants ◽

Humid Forest ◽

Geochemical Composition ◽

Chemical Index ◽

Dry Spell

The Kukkal basin, Tamil Nadu, India, receives most of its rain from the southwest monsoon (SWM). A sediment core from Kukkal Lake preserves a continuous sediment record from the early-Holocene to present (9000 yr BP to present). The present lake is situated at an elevation of ~1887 m a.s.l., in a small basin that appears to have alternated between a and wetland depositional environment. Climate proxies, including sediment texture, total organic carbon (TOC), total nitrogen (TN), C/N, pollen and geochemical composition indicate a steady progression to wetter conditions, with two stepwise changes at about 8000, and between 3200 and 1800 yr BP. The change at 8000 yr BP appears to correspond to a brief (100–150 years) dry spell recorded elsewhere in India. The change at 3200–1800 yr BP consisted in a rapid intensification of the SWM, and may correlate with the initiation of the ‘Roman Warm Period’. There is no clear evidence of changes at the times of the ‘Medieval Warm Period’ (‘MWP’) and the ‘Little Ice Age’ (‘LIA’). The C/N ratio of the sediments ranges from 14.02 to 8.31, indicating that the organic matter originated from a mixture of lacustrine algae, vascular and terrestrial plants. Chemical weathering indices (Chemical Index of Alteration (CIA), Chemical Index of Weathering (CIW), and Plagioclase Index of Alteration (PIA)) are consistent with extreme silicate weathering. Pollen data show a development from savanna vegetation prior to about 8000 yr BP, followed by grassland with palms, the appearance of ferns just prior to 3200 yr BP and the establishment of the tropical humid forest between 3200 and about 1800 yr BP.

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Luminescence chronostratigraphy for the loess deposits in Złota, Poland

Geochronometria ◽

10.1515/geochr-2015-0073 ◽

2018 ◽

Vol 45 (1) ◽

pp. 44-55 ◽

Cited By ~ 8

Author(s):

Piotr Moska ◽

Grzegorz Adamiec ◽

Zdzisław Jary ◽

Andrzej Bluszcz ◽

Grzegorz Poręba ◽

...

Keyword(s):

Luminescence Dating ◽

Humid Climate ◽

Geochemical Composition ◽

Climate Conditions ◽

Flood Plains ◽

River Flood ◽

Close Relationship ◽

Dating Method ◽

Loess Profile ◽

Loess Deposits

Abstract Loess formations in Poland display a close relationship with cooling and warming trends of the Northern Hemisphere during the Pleistocene. Loess sequences sensitively record regional palaeoclimatic and palaeoecological changes. The Złota loess profile (21°39’E, 50°39’N) provides a unique opportunity to reconstruct climate conditions in the past in this part of Poland. This continuous sequence of loess and palaeosol deposits allows to distinguish between warmer and more humid climate which is favourable for soil development and much colder and dry periods which are conducive to loess accumulation. The silty and sandy aeolian material originates mainly from weathered rock surfaces affected by frost shattering or from glaciofluvial/fluvial deposits of river flood plains. In Poland, loess and loess-like formations occur in the southern part of the country, mostly in the south polish uplands, i.e. in the Lublin, Sandomierz, and Cracow Uplands. We used different techniques to establish a chronological framework for this site. 21 samples for luminescence dating were collected from the investigated loess profile in Złota. Infrared post-IR IRSL dating method was applied to the polymineral fine grains (4–11µm). The dating results are accompanied by detailed analyses of the geochemical composition, organic carbon and carbonate. Also, analysis of magnetic susceptibility and grain-size distribution were investigated. Based on such a large stratigraphic dataset an age-depth model using OxCal has also been constructed for this site.

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Global patterns of oceanic dust deposition during Pliocene-Pleistocene transitions

10.5194/egusphere-egu21-10616 ◽

2021 ◽

Author(s):

Oriol Teruel ◽

Antoni Rosell-Melè ◽

Nuria Penalva-Arias

Keyword(s):

Regional Climate ◽

Global Scale ◽

Dust Deposition ◽

Dust Transport ◽

Major Transitions ◽

The Earth ◽

Global Patterns ◽

Time Periods ◽

Global Atmospheric Circulation ◽

Global Emissions

The is a mounting evidence that global emissions of dust were significantly higher during glacial than interglacial periods of the Pleistocene, and probably the Pliocene epochs. this pattern is observed in records from the low and mid latitudes, albeit with a varying degree of amplitude. During these time periods spanning 4 million years, the Earth climate underwent major transitions, such as the initiation of the Northern Hemisphere Glaciations and the Mid Pleistocene Transition. In parallel, dust transport and deposition on the oceans might have underwent stepwise increases, mainly during glacials. However, it is not clear yet if such changes are representative of global or regional climate response. Thus, dust records in marine sediments reflect changes in the different processes that drive the emission, transport, and deposition of dust on the oceans. In here, we report a compilation of marine dust records spanning the Pliocene-Pleistocene from all the major ocean basins. The synthesis of dust records on a global scale allows the identification of common patterns of variability and drivers. We analyse the data to infer changes in the global atmospheric circulation on orbital time scale, and to assess its meridional and zonal response during major climate transitions since the Pliocene.

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