Aeolian Dust Transport Research Articles

Satellite monitoring of climatic factors regulating phytoplankton variability in the Arabian (Persian) Gulf

Possible factors regulating phytoplankton variability in the Arabian (Persian) Gulf were analyzed on the basis of satellite observations and meteorological data (1997–2009), including remotely-sensed chlorophyll a concentration (CHL), sea surface temperature, wind, solar radiation, precipitation, and aerosols. Shallow waters of northwestern Gulf influenced by Shatt Al-Arab River discharge were more productive than open Gulf waters, although seasonal CHL patterns in this and other shallow regions looked unrealistic likely because the CHL signal was obscured by bottom reflection. Therefore our further analyses focused on the open Gulf waters, which show a subtropical seasonal CHL cycle with maximum in winter and minimum in spring–summer. This cycle, however, was decoupled from the seasonal extremes of wind mixing. Interannual variations of CHL in the open Gulf regions were correlated with precipitation and aerosol data rather than with wind and sea surface temperature, consistent with the hypothesis of atmospheric deposition as a factor regulating phytoplankton growth. The effect of dust fertilization was likely observed in 2000 and 2008, when low precipitation and aerosol properties indicating elevated level of aeolian dust transport were followed by phytoplankton blooms.

A continuous high‐resolution dust record for the reconstruction of wind systems in central Europe (Eifel, Western Germany) over the past 133 ka

The last glacial cycle in Central Europe is dominated by processes of aeolian dust transport and accumulation. These dust deposits are preserved in soils and lake sediments and provide detailed information about the climate variability during cold and dry periods. Especially the transitions from warm into cold periods are characterized by turbulent climate conditions. The main problems of terrestrial paleoclimate reconstructions are the completeness of the core material and a sampling resolution. To detect single dust storms we use a particle detection method, which allows high resolution, sub‐annual analyses of sediment structures in undisturbed samples. The ELSA (Eifel Laminated Sediment Archive) stack is a compilation of four different lake sediment cores of the Eifel region (Western Germany) and comprise the period of the last 133 ka. The results of our analyses show high frequencies of dust storm events during the first cold events C24 and C23 after the last warm stage. In opposition, the coldest periods of the last glacial cycle OIS‐4 (70–60 ka BP) and OIS‐2 (35–14 ka BP) are characterized by stable climate conditions that provide the accumulation of homogenous dust sediments.

Endosulfan in Wind-Transported African Dust Depositions in Crete

The presence of endosulfan in samples of African dust after a typical red dust storm in May 2007 was investigated. The samples were collected from a remote and mountainous area of Crete (Greece) where olive groves are cultivated. Endosulfan I, endosulfan II and endosulfan sulphate were detected at concentrations of 2.7, 1.4 and 1.1 ng/g, respectively, indicating that long range aeolian dust transport could be a possible source of contamination of olive cultivations.

African monsoon enhancement during the penultimate glacial period (MIS 6.5 ∼ 170 ka) and its atmospheric impact

A reconstruction of northwest African summer monsoon strength during the cold marine isotopic stage (MIS) 6 indicates a link to the seasonal migration of the Intertropical Convergence Zone (ITCZ). High‐resolution studies of eolian dust supply and sea surface temperature recorded in marine core MD03‐2705, on the Mauritanian margin, provide a better understanding about the penultimate glacial history of northwestern African aridity/humidity and upwelling coastal activity. Today, site MD03‐2705 experiences increased upwelling and dust flux during the winter months, when the ITCZ is in a southerly position. Analyses of foraminifera isotopic composition suggest that during MIS 6.5 (180–168 ka) the average position of the ITCZ migrated north, marked by an increase in the strength of the summer monsoon, which decreased eolian dust transport and the coastal upwelling activity. The northward migration is in phase with a specific orbital combination of a low precessional index with a high obliquity signal. High‐resolution analysis of stable isotopes (δ18O and δ13C) and microscale resolution geochemical (Ti/Al and quartz grain counts) determinations reveal that the transition between monsoonal humid (MIS 6.5) and dry (MIS 6.4) conditions has occurred in less than 1.3 ka. Such rapid changes suggest a nonlinear link between the African monsoonal rainfall system and environmental changes over the continent. This study provides new insights about the influence of vegetation and oceanic temperature feedbacks on the onset of African summer monsoon and demonstrates that, during the penultimate glacial period, changes in tropical dynamics had regional and global impacts.

Aeolian dust dynamics in central Asia during the Pleistocene: Driven by the long‐term migration, seasonality, and permanency of the Asiatic polar front

Loess‐paleosol sequences preserve detailed archives of climate change, reflecting the dynamics of aeolian dust sedimentation and the paleodust content of the atmosphere. The detailed investigation of particle size distributions (PSDs) of windblown sediments is an increasingly used approach to assess the paleorecord of aeolian dust dynamics. The central Asian loess belt offers the potential to reconstruct Pleistocene atmospheric circulation patterns along an adjacent west‐east transect within interior Eurasia through granulometric studies. In this study we present the aeolian dust record of the loess sequence at Remisowka (SE Kazakhstan), which reflects a detailed signal of glacial‐interglacial climate and atmospheric dynamics in central Asia. On the basis of radiocarbon and amino acid geochronologic data, long‐term semicontinuous trends in the aeolian dust record of the Last Glacial Cycle are observed and interpreted to reveal their paleoclimate signal. In consideration of the modern synoptical atmospheric circulation patterns and aeolian dust transport in central Asia, it is likely that the observed trends reflect the long‐term migration, seasonal duration, and permanency of the polar front during the late Pleistocene. Previously published models, which focused on the reciprocal glacial‐interglacial influence of the zonal Westerlies and the Asiatic high on the aeolian dust transport in central Asia, were overly simplified and should be modified to include the major influence of the Asiatic polar front. As the polar front activity is intimately connected with the development and position of the interhemispherically active, high‐level planetary frontal zone (HPFZ), the presented data give insight to long‐term aeolian dust dynamics and climate variability of interior Eurasia, which are linked with interhemispheric climates.

Spatiotemporal variations of Zr/Rb ratio in three last interglacial paleosol profiles across the Chinese Loess Plateau and its implications for climatic interpretation

The ratio of Zirconium to Rubidium (Zr/Rb) is suggested to be a better proxy for the East Asian winter monsoon strength than the widely-used grain size distribution. The rationale for the Zr/Rb proxy relies on the following assumptions: (1) Grain size fractionating characteristics during eolian dust transport should be archived in the Zr/Rb ratio records and this assumption is based on the premise that Zr is preferentially enriched in coarser grain size fraction while Rb tend to be enriched in finer grain size fraction; and (2) post-depositional weathering does not change the Zr/Rb ratio due to the immobility of these two elements. To examine these two assumptions, three last interglacial paleosols (S1) from Dingxi, Tianshui and Lantian, along a NW-SE transect across the Chinese Loess Plateau, were geochemically investigated. Our results show that the Rb concentration exhibits an increasing trend along the NW-SE transect both in the paleosol (S1) and the measured portions of the loess units (L1 and L2), being supportive to the assumption that Rb is enriched in the fine particles. But we also found that Rb loss did occur to some extent in the three profiles, contradicting to the presumption of Rb immobility during pedogenic processes. The Zr concentration exhibits an expected decreasing trend in the measured portions of the loess units and an unexpected increasing trend in the paleosol along the NW-SE transect. Moreover, the ratios of Zirconium to Hafnium (Zr/Hf) show different variation patterns between interglacial and glacial, implying that Zr-bearing minerals and their resident grain size fractions are probably not identical during interglacial and glacial. Thus, the assumption that Zr is enriched in coarse grain size fraction can no longer hold. We conclude that the final Zr/Rb value is not only dependent on grain size sorting processes but also on post-depositional alteration and source provenance. Under enhanced chemical weathering, especially when chemical index of alteration (CIA) is greater than 65, the Zr/Rb value loses its validity to be a reliable proxy for the winter monsoon strength. In addition, all the Zr/Rb value is constrained above 1.7, a minimum which is definitely modulated by all the three aforementioned factors.

Variability in terrigenous sedimentation processes off northwest Africa and its relation to climate changes: Inferences from grain-size distributions of a Holocene marine sediment record

Variations in deposition of terrigenous fine sediments and their grain-size distributions from a high-resolution marine sediment record offshore northwest Africa (30°51.0′N; 10°16.1′W) document climate changes on the African continent during the Holocene. End-member grain-size distributions of the terrigenous silt fraction, which are related to fluvial and aeolian dust transport, indicate millennial-scale variability in the dominant transport processes at the investigation site off northwest Africa as well as recurring periods of dry conditions in northwest Africa during the Holocene. The terrigenous record from the subtropical North Atlantic reflects generally humid conditions before the Younger Dryas, during the early to mid-Holocene, as well as after 1.3 kyr BP. By contrast, continental runoff was reduced and arid conditions were prevalent at the beginning of the Younger Dryas and during the mid- and late Holocene. A comparison with high- and low-latitude Holocene climate records reveals a strong link between northwest African climate and Northern Hemisphere atmospheric circulation throughout the Holocene. Due to its proximal position, close to an ephemeral river system draining the Atlas Mountains as well as the adjacent Saharan desert, this detailed marine sediment record, which has a temporal resolution between 15 and 120 years, is ideally suited to enhance our understanding of ocean–continent–atmosphere interactions in African climates and the hydrological cycle of northern Africa after the last deglaciation.

The aeolian flux of calcium, chloride and nitrate to the McMurdo Dry Valleys landscape: evidence from snow pit analysis

We have determined the flux of calcium, chloride and nitrate to the McMurdo Dry Valleys region by analysing snow pits for their chemical composition and their snow accumulation using multiple records spanning up to 48 years. The fluxes demonstrate patterns related to elevation and proximity to the ocean. In general, there is a strong relationship between the nitrate flux and snow accumulation, indicating that precipitation rates may have a great influence over the nitrogen concentrations in the soils of the valleys. Aeolian dust transport plays an important role in the deposition of some elements (e.g. Ca2+) into the McMurdo Dry Valleys' soils. Because of the antiquity of some of the soil surfaces in the McMurdo Dry Valleys regions, the accumulated atmospheric flux of salts to the soils has important ecological consequences. Although precipitation may be an important mechanism of salt deposition to the McMurdo Dry Valley surfaces, it is poorly understood because of difficulties in measurement and high losses from sublimation.

Oxidant Enhancement in Martian Dust Devils and Storms: Storm Electric Fields and Electron Dissociative Attachment

Laboratory studies, numerical simulations, and desert field tests indicate that aeolian dust transport can generate atmospheric electricity via contact electrification or "triboelectricity." In convective structures such as dust devils and dust storms, grain stratification leads to macroscopic charge separations and gives rise to an overall electric dipole moment in the aeolian feature, similar in nature to the dipolar electric field generated in terrestrial thunderstorms. Previous numerical simulations indicate that these storm electric fields on Mars can approach the ambient breakdown field strength of approximately 25 kV/m. In terrestrial dust phenomena, potentials ranging from approximately 20 to 160 kV/m have been directly measured. The large electrostatic fields predicted in martian dust devils and storms can energize electrons in the low pressure martian atmosphere to values exceeding the electron dissociative attachment energy of both CO2 and H2O, which results in the formation of the new chemical products CO/O- and OH/H-, respectively. Using a collisional plasma physics model, we present calculations of the CO/O- and OH/H- reaction and production rates. We demonstrate that these rates vary geometrically with the ambient electric field, with substantial production of dissociative products when fields approach the breakdown value of approximately 25 kV/m. The dissociation of H2O into OH/H- provides a key ingredient for the generation of oxidants; thus electrically charged dust may significantly impact the habitability of Mars.

Composition of sand storm particles in the Southern Far East

Lithostructural composition of the dust storm material (DMS) sampled in the southern Far East in the spring of 2002–2004 has been analyzed. Samples were taken near Vladivostok, where the eolian dust precipitation varied from 0.1 to 6.5 g/m2 at that time. Pelitic and fine-silt particles predominate in eolian dust. Grain size, mineral, and chemical compositions of the DSM are compared to data on the DSM in adjacent territories of China, Korea, and Japan, as well as to background data on aerosol precipitation in southern Primorye. Possible mechanisms of the eolian dust transport from inner parts of Asia at different climatic variations in the Pleistocene-Holocene are discussed.

A magnetic mineral record of Late Quaternary tropical climate variability from Lake Bosumtwi, Ghana

We report magnetic hysteresis results from sediment cores obtained from Lake Bosumtwi, Ghana. As a hydrologically closed basin, the water budget of Lake Bosumtwi is extremely sensitive to changes in the precipitation/evapotranspiration balance. Lake Bosumtwi lies in the path of the seasonal migration of the intertropical convergence zone (ITCZ); hence, the lake is ideally situated to study monsoon variability in West Africa. Five distinctive magnetic mineral zones (A–E) were identified in the 11-m-long sediment cores that span the last 26,000 calendar years. Prior to 12 calendar (cal) ka, low concentrations of multidomain, high-coercivity magnetic minerals are present. Three prominent shifts towards very high concentrations of high-coercivity iron sulfide (greigite) magnetic minerals are centered at 12,470, 17,290, and 22,600 calendar years during the last glacial period (magnetic zones D 1–3). Between 12 and 3.2 cal ka, there is an abrupt shift to moderately high concentrations of mixed multidomain and single-domain, low-coercivity minerals and an organic-rich sapropel lithology. Since 3.2 cal ka, the magnetic mineral parameters reveal a shift to increased amounts of high-coercivity magnetic minerals. These magnetic mineral zones document tropical climate variability on a variety of temporal scales. Glacial age sediments have a high-coercivity magnetic mineralogy due to increased aeolian dust transport from the Sahel to Lake Bosumtwi as well as postdepositional reductive diagenesis. During the last glacial period, the increased strength of Harmattan and North African continental trade winds, the southward depression of the ITCZ, and weakened summer monsoon strength resulted in increased regional aridity and greater dust flux out of Sahel source regions. The greigite-bearing D magnetic zones correspond to brief lowstands in the level of Lake Bosumtwi and likely represent periods of intensified aridity in West Africa. The D magnetic zones closely resemble the timing and duration of Heinrich events and suggest a hemispheric-scale climatic coupling between the tropics and poles. The well-documented African humid period (AHP) is characterized by abrupt shifts in magnetic parameters between 12 and 3.2 cal ka. Dust flux to Lake Bosumtwi is inferred to be very low during this humid interval due to the strengthening of the summer monsoon. Since 3.2 cal ka, the magnetic mineral parameters suggest increased aridity as compared to the AHP. This work demonstrates that the magnetic properties of Lake Bosumtwi sediment are a sensitive recorder of abrupt climate change of global significance.

A magnetic mineral record of Late Quaternary tropical climate variability from Lake Bosumtwi, Ghana

Abstract We report magnetic hysteresis results from sediment cores obtained from Lake Bosumtwi, Ghana. As a hydrologically closed basin, the water budget of Lake Bosumtwi is extremely sensitive to changes in the precipitation/evapotranspiration balance. Lake Bosumtwi lies in the path of the seasonal migration of the intertropical convergence zone (ITCZ); hence, the lake is ideally situated to study monsoon variability in West Africa. Five distinctive magnetic mineral zones (A–E) were identified in the 11-m-long sediment cores that span the last 26,000 calendar years. Prior to 12 calendar (cal) ka, low concentrations of multidomain, high-coercivity magnetic minerals are present. Three prominent shifts towards very high concentrations of high-coercivity iron sulfide (greigite) magnetic minerals are centered at 12,470, 17,290, and 22,600 calendar years during the last glacial period (magnetic zones D1–3). Between 12 and 3.2 cal ka, there is an abrupt shift to moderately high concentrations of mixed multidomain and single-domain, low-coercivity minerals and an organic-rich sapropel lithology. Since 3.2 cal ka, the magnetic mineral parameters reveal a shift to increased amounts of high-coercivity magnetic minerals. These magnetic mineral zones document tropical climate variability on a variety of temporal scales. Glacial age sediments have a high-coercivity magnetic mineralogy due to increased aeolian dust transport from the Sahel to Lake Bosumtwi as well as postdepositional reductive diagenesis. During the last glacial period, the increased strength of Harmattan and North African continental trade winds, the southward depression of the ITCZ, and weakened summer monsoon strength resulted in increased regional aridity and greater dust flux out of Sahel source regions. The greigite-bearing D magnetic zones correspond to brief lowstands in the level of Lake Bosumtwi and likely represent periods of intensified aridity in West Africa. The D magnetic zones closely resemble the timing and duration of Heinrich events and suggest a hemispheric-scale climatic coupling between the tropics and poles. The well-documented African humid period (AHP) is characterized by abrupt shifts in magnetic parameters between 12 and 3.2 cal ka. Dust flux to Lake Bosumtwi is inferred to be very low during this humid interval due to the strengthening of the summer monsoon. Since 3.2 cal ka, the magnetic mineral parameters suggest increased aridity as compared to the AHP. This work demonstrates that the magnetic properties of Lake Bosumtwi sediment are a sensitive recorder of abrupt climate change of global significance.

Radiative forcing due to dust aerosol over east Asia-north Pacific region during spring, 2001

An optical model accounting for the East Asian dust is proposed as a result of theory calculation and composition analysis of the aerosol samples collected in China desert during the international project, “Studies on the Origin and Transport of Aeolian Dust and its Effects on Climate (ADEC)”. Study indicates that dust aerosols emitting from China deserts have smaller imaginary parts of refractive indices, therefore absorb less and scatter more solar radiation than the most dust optical models published so far. Furthermore, the forward fraction of scattering is less and the backscattering is stronger than those of the other models. The seasonal averaged radiative forcing in spring, 2001 over east Asia-north Pacific region is simulated employing the new dust optical model. The net forcing at the top of atmosphere (TOA) is estimated as-0.943 W · m−2 for regional and seasonal mean, with shortwave and longwave contributions of −1.700 and 0.759 W · m−2, respectively. The surface net forcing is calculated to be −5.445 W · m−2, and made up of shortwave component of −6.250 W · m−2 and longwave component of +0.759 W · m−2. The distributions of TOA and surface net forcing over this region are also analyzed in this study.

The Sahara–East Mediterranean dust and climate connection revealed by strontium and uranium isotopes in a Jerusalem speleothem

This paper explores the potential of Sr and U isotope systems in speleothems as tracers of eolian dust transport and hydrological conditions. The study focuses on a speleothem from Jerusalem spanning the past 220 kyr. This speleothem provides a precisely dated record of dust flux from the Sahara to the East Mediterranean. Enhanced dust flux and Terra Rossa soil development are reflected by elevated 87Sr/86Sr ratios in the speleothem (0.7082–0.7086), while lower 87Sr/86Sr ratios (∼0.7078) indicate higher contribution of the local bedrock due to low dust flux and low soil accumulation. The strontium isotope system in the speleothem is a robust monitor of the Sahara monsoon-modulated climate, since dust uptake is related to development or reduction in vegetation cover of Sahara soil. The [234U/238U] activity ratios in the speleothem range between 1.12 and 1.0. The high activity values may indicate selective removal of 234U from the soil while the low values converge to the bedrock. The migration of 234U to the cave reflects mainly the regional hydrological conditions that are modulated by the North Atlantic–Mediterranean climate system. Thus, the speleothem provides a combined record of the monsoon–North Atlantic climatic systems. Long-term stability in glacial 87Sr/86Sr ratios (0.7083±0.0001 over the past 220 kyr) suggests an overall similarity in eolian dust sources, and uniformity in the synoptic conditions that dominate the dust storm tracks during glacial periods.

中国東部および日本国内で2001年から2002年にかけて採取した風送ダストの 大気中濃度と物理化学特性の変動

In order to clarify the variation and characterization of dust particles, we started the JapanChina joint project, “Studies on origin and transport of aeolian dust and its impact on climate”. We set up sampling instruments in Beijing, Qingdao and Hefei in China and Naha, Fukuoka, Nagoya and Tsukuba in Japan and collected aeolian dust that originated in the desert area of western China. In this study, we collected the aeolian dust from February 2001 to May 2002 and studied the monthly variation of dust concentrations. The one-year observation data show that the aerosol has a bimodal size distribution (one peak at around 0.5μm corresponds to particles of anthropogenic origin and another peak at around 4-5μm reflects aeolian dust of continental origin) and the coarser particles increased when a dust event occurred. The seasonal variations of dust concentration showed that the aeolian dust content in spring is higher than other seasons. It sometimes became high in winter in Qingdao. The aerosol concentration under usual conditions at each observation station in Japan does not differ so much, however that in China is larger than in Japan. During the intensive observation period (April 2002) when a dust storm event occurred in China, the coarser fraction increased in grain size, and the average dust concentration increased. The aerosol concentration seems to be in the order of Beijing > Qingdao > Hefei and Beijing > Fukuoka > Nagoya > Tsukuba > Naha. The main chemical components of water-soluble fraction are supposed to be (NH4)2SO4 in finer particles and Ca(NO3)2, CaCl2, NaNO3 and NaCl in coarser particles. Aluminum content in waterinsoluble fraction was high in coarser particles, and this confirmed that they consist of a mineral component.

Is It Possible to Use 90Sr and 137Cs As Tracers for the Aeolian Dust Transport

A noble approach for the estimation of the deposition of the Asian dust over Japan by using atmospheric anthropogenic radioactivity, 90Sr and 137Cs, is proposed. Those radioactivities once deposited globally onto the ground by the past nuclear test, etc. are resuspended along with the surface soil particles in the air by the storm and deposited again on the ground. The difference in 137Cs/90Sr activity ratios in the surface soil between dry and wet climatic conditions gives a clue to know about the source of the dust. It was found that the average activity ratio in the deposited material (average: 2.1, n=82) at MRI, Tsukuba in the 1990s is not close to that of the surface soil taken in neighborhood (median: 6.8, n=8), which had been considered as the primary source. While, it is close to that of the soil samples taken in the arid area in the Asian continent (median: 2.0, n=4), which is the one of the source regions of the aeolian dust. Thus we can reasonably assume that deposited dust in Tsukuba is brought not only from the neighboring fields, etc. but also from the arid area in the continent. Using a simple two-component model it was estimated that the Asian dust may transport about 90% of 90Sr and 70% of 137Cs depositions observed in Tsukuba in the 1990s. Also, Asian dust may transport about 2/3 of the dust deposited in Tsukuba.

Origin and derived courses of eolian dust quartz deposited during marine isotope stage 2 in East Asia, suggested by ESR signal intensity

The ESR signal intensity of fine quartz (finer than 20 μm) during marine isotope stage (MIS) 2 in the Japanese Islands is spatially. Under the assumption that the values of ESR signal intensity of eolian fine quartz reflect those of the quartz at the in-source areas, the source area and trajectory of eolian dust are tentatively reconstructed. In northern Japan, where the ESR signal intensity is high (10–12), the eolian dust seems to have originated from Siberia and Mongolia where the Precambrian rocks with a high ESR signal intensity are widely exposed. In central and southern Japan, where the ESR signal intensity is medium (5.8–8.7), the eolian dust seems to be supplied from central Asia where Paleozoic–Mesozoic rocks with a medium ESR signal intensity are widely exposed. For the southernmost islands of Japan, where the ESR intensity signal increases again (9.7–13.4), seem to have an eolian dust supply from areas south of Himalayan Range where the Precambrian rocks are widely exposed. On the basis of ESR intensity signals, three major courses of eolian dust transport in MIS 2 are proposed: the winter monsoon in eastern and northern Japan, the summer subtropical jet in western and southern Japan, and the winter subtropical jet in the southernmost islands of Japan.

Provenance, transport and characteristics of modern aeolian dust in western Gansu Province, China, and interpretation of the Quaternary loess record

Results of a comparative analysis of a 4-year set of monthly samples of airfall dust with samples from surface alluvial fan deposits, desert sand dunes and late Pleistocene loess and palaeosols in Gansu Province, northern China, are summarized. They suggest a qualification of the conventional view that the sand deserts were the primary single source of the Quaternary loess. It is argued that silts deflated from the surfaces of the large and numerous piedmont alluvial fans in the Hexi Corridor, Gansu, constituted a major contribution to the loess column in the western region of the Chinese Loess Plateau. The present dust fall regime in the Hexi Corridor suggests that distribution and rate of accumulation of airfall silt in the present interglacial is similar to that in parts of the Pleistocene loess record.

地球環境変化とヒマラヤ・チベット山塊の役割 レス・風成塵からみた最終氷期のモンスーンアジアの古環境とヒマラヤ・チベット高原の役割

Loess deposits spread widely in central and East Asia, where the main area of loess deposition is on the Chinese Loess Plateau. Climatic conditions in central and east Asia allowed a substantial loess accumulation since 2, 400ka., while in South and Southeast Asia, the presence of loess is recognized locally in a periphery of Thar Desert and on the terraces of South India and Thailand. A weakened monsoon during glacial phases seems to diminish a loess accumulation in these regions. Most areas of East Asia such as the Japanese Islands, Korea and Taiwan were affected the depositionof eolian dust originated in the drier area of Asian continent, especially during the Last Glacial time. A depositional rate of loess and eolian dust in the glacial period was higher than in the interglacial. Fine silt production in deserts and glacierized areas seems to have increased in glacial period. On the Chinese Loess Plateau and western Japan, a depositional rate of loess and dust in MIS 2 was 1.3 times higher than in MIS 4. On the contrary, in northern Japan, a dust deposition rate of MIS 2 was 2.5 times higher than in MIS 4. The difference of rates between the western and the northern Japan seems to reflect a paleoenvironmental change of the source areas of eolian dust: a desert condition might have increased more in the northern Asia from which the eolian dust mainly came to the northern Japan, because of a drier condition in winter by a decrease of snowfall.ESR intensity signal of fine quartz (finer than 20μm) during MIS 2 in the Japanese Islands varies in different localities. Under the assumption that the values of ESR intensity signal of eolian fine quartz reflect those of the quartz at the source area of eolian dust, the source area and trajectory of eolian dust are tentatively reconstructed. The northern Japan where the ESR intensity signal is high (10-12), the eolian dust seems to be supplied from Siberia and Mongolia where the Precambrian rocks with a high ESR intensity signal are widely exposed. The central and southern Japan where the ESR intensity signal is medium (5.8-8.7), the eolian dust seems to be supplied from central Asia where the Paleozoic-Mesozoic rocks with a medium ESR intensity signal are widely exposed. The southernmost islands of Japan where the ESR intensity signal increases again, seem to have an eolian dust supply from South China and India where the Precambrian rocks are widely exposed. On the basis of ESR intensity signals, three major courses of eolian dust transport in MIS 2 are proposed: the winter monsoon in the northern Japan, the summer subtropical jet in the central and southern Japan, and the winter subtropical jet in the southernmost islands of Japan.The uplift of the Tibetan Plateau and Himalayan Range seems to enhance a production and supply of Asian loess, by the intensification of Siberian high and Asian monsoon system. Glacier extension on the Tibetan Plateau and Himalayan Range, which is related to the uplift of these areas, also enhanced the production of loess material in the source area. The detail study which correlates the glaciation with the loess deposition in central Asia is much more required.

Tropical Atlantic terrigenous fluxes since 25,000 yrs B.P.

Twelve tropical Atlantic cores, each 14C-dated and with δ 18O records, were examined for burial fluxes of terrigenous (mostly eolian) sediment and biogenic (opal and CaCO 3) sediment over the last 25,000 years. The similar flux trends through time of these three components within each core indicates that post-depositional redistribution of sediment is the strongest control on burial fluxes in the tropical Atlantic. Increased terrigenous dust fluxes apparent during the last glacial maximum in several cores are consistent with several previous studies. The lack of significant dust flux maxima following the early Holocene monsoon maximum argues strongly against changes in source-area humidity/aridity being a significant factor in orbital-scale eolian dust transport and deposition in this region. This suggests that the enhanced glacial influxes of dust to the tropical Atlantic are mainly due to changes in transport by winter winds, rather than to glacial hyper-aridity.