Quantitative Precipitation Reconstructions Research Articles

Vegetation, hydrology, and quantitative monsoon precipitation since the Last Glacial Maximum in Central China

The Yangtze River Basin is a crucial region in the monsoon region of China, and reconstructing its hydrological and precipitation evolution is important for developing a more robust understanding of the evolution of the East Asian Summer Monsoon. A pollen record from a strata profile (JZ2010) in the Jianghan Basin of Central China reveals variations in paleovegetation and paleoenvironmental and paleoclimatic conditions covering the last 24 cal kyr BP at ~90 years resolution. We perform a quantitative precipitation reconstruction (based on a weighted averaged partial least squares method). Results of the study show that the vegetation in the region experienced a succession from coniferous and broad-leaved mixed forest to evergreen and deciduous mixed forest and then to secondary coniferous forest. Over the past 24 kyr, the climate was relatively dry during the deglacial period, particularly during HS1 and the Younger Dryas cold event, interrupted by a warm and humid Bølling-Allerød. Precipitation in the early Holocene was at its maximum, peaking between 10.0 and 7.0 cal kyr BP followed by drier conditions between 6.5 and 4.5 cal kyr BP. Subsequent wetter conditions lasted until 3.8 cal kyr BP, after which precipitation gradually declined. Overall, the quantitative precipitation reconstruction is consistent with other proxy-based precipitation reconstructions in the Yangtze River region. However, the temporal pattern of variations in precipitation is distinct from that of the northern China monsoon region, where the precipitation peak occurred during the mid-Holocene. The study suggests that, prior to the Holocene, climate change was controlled by insolation dynamics and high latitude teleconnections, while during the Holocene it was primarily influenced by low latitude teleconnections, including the El Niño-Southern Oscillation, which controlled the dipolar rainfall pattern in the monsoon region of China. The high resolution record of changing climate in the East Asian monsoon region over a period spanning the LGM and Holocene provides a useful benchmark for modelling future precipitation change in southern and northern China against the background of global warming.

Quantitative precipitation reconstruction since mid-Holocene from northeastern Tibetan Plateau: Implications for interplay between Asian summer monsoon and Westerlies

Both the Asian Summer Monsoon (ASM) and Westerlies exhibit strong impacts on climate changes of the Tibetan Plateau (TP), but little is known about their contributions to regional precipitation during the Holocene. Here we reported a pollen record from Lake Alake, based on which the quantitative mean annual precipitation (PANN) was reconstructed. Herbaceous taxa of Cyperaceae, Poaceae, Chenopodiaceae, and Artemisia were dominant in Alake pollen assemblage whose variations were mainly affected by humidity changes. The precipitation was high in 7200–5400 cal. yr BP, followed by decreasing trends in 5000–3000 cal. yr BP, and obviously increased after 3000 cal. yr BP. The variations of PANN in the Alake record suggest that high precipitation in middle Holocene was primarily contributed by the ASM driven by orbital forcing of insolation. However, the rising trend of PANN during the late Holocene probably indicated the increased of non-monsoonal precipitation and highlighted the contribution from the Westerlies. Our results suggest that the variation of precipitation transported by Westerlies might have reduced the seasonal variability of precipitation and contributed to the long-term wetting trend on the northeastern TP during the late Holocene.

Quantitative estimates of Holocene precipitation from aeolian sand-palaeosol sequences across the Ordos Plateau, northern China, based on surface soil geochemistry

Quantitative precipitation reconstructions are important for studies of past Earth surface processes and for predicting future trends, especially in the semi-arid region of northern China, where the dune fields landscape is dominated by shifts of the Asian summer monsoonal boundary. However, the relationships between desert deposits and climatic factors are controversial and it remains unclear how these relationships can be used for quantitative paleoenvironmental reconstruction. We investigated the relationship between the degree of chemical weathering of surface soil, quantified using the Chemical Index of Alteration (CIA) and modern climatic variables, along transects across the Ordos Plateau. The relationship was then used to obtain quantitative estimates of Holocene mean annual precipitation (MAP) from aeolian sand-palaeosol sequences in this region. The results reveal that MAP is the dominant climatic variable controlling the chemical weathering of surface soil, accounting for ∼ 69–91% of the total explained variance. This robust relationship enabled us to establish a regional CIA-based transfer function to reconstruct the MAP. This relationship was confirmed by a study of Holocene climate change and chemical weathering of aeolian sequences across the Ordos Plateau, which indicated that paleo-precipitation explained ∼ 76–88% of the total explained variance. The reconstruction demonstrates that the MAP was respectively ∼ 60–103 mm and ∼ 21–63 mm lower in the early and late Holocene than the modern MAP, while it was ∼ 34–77 mm (∼20–30%) higher in the middle Holocene than the modern MAP. Our results also demonstrate the latitudinal zonality of MAP evolution across the Ordos Plateau during the mid-Holocene. Overall, our findings provide new insights into the chemical weathering of surface soils and the response of Holocene aeolian deposits to climate change, and they confirm the utility of a geochemical proxy for quantitative environmental reconstruction in the semi-arid desert region of northern China.

Quantitative precipitation reconstructions from Chagan Nur revealed lag response of East Asian summer monsoon precipitation to summer insolation during the Holocene in arid northern China

East Asian summer monsoon (EASM) variability is primarily responsible for climate change in East Asia, influencing over a billion lives. The pattern and mechanisms of EASM change during the Holocene are intensely debated. In this study, we produce a high-quality age-depth model for a 11.7 m lacustrine record (CG18B core) from central Chagan Nur (a closed-basin lake located on the southern Mongolia plateau at the fringe of the modern EASM region) using 27 radiocarbon dates on organic materials and 10 quartz optically stimulated luminescence (OSL) ages on the lake sediments. Multiple-proxy analyses of pollen, grain size, total organic content, and CaCO3 content are used to reconstruct Holocene monsoonal precipitation change in the region. Reconstructed Chagan Nur level changes during the Holocene are based on 18 quartz OSL ages from well-preserved paleolake shorelines at different elevations on the northwestern basin margin. A combination of the lacustrine pollen records and a paleohydrology lake level change model is used to define quantitative precipitation change at the fringe of the EASM dominated region during the Holocene. Our results show that a lake highstand of 15-12 m higher than present occurred at 11–5 ka, followed by a decrease in lake levels to 8-7 m higher than present at 4–3 ka, and a general lake lowering during the late Holocene. EASM dominated annual precipitation varied between 420 mm and 280 mm during the Holocene period in the basin, indicating a generally semi-arid environment on the southern Mongolian Plateau, and corresponding to prevailing open steppe vegetation in the basin throughout the Holocene. EASM precipitation intensity increased from the early Holocene to the beginning of the mid-Holocene, with a maximum precipitation 30–50% higher than present at 8–6 ka, followed by a decrease in precipitation during the late Holocene. EASM precipitation shown in these records lags northern Hemisphere solar insolation shifts by ∼3 ka, indicating that variation in EASM intensity did not respond directly to northern Hemisphere summer insolation, but rather was likely modulated by high latitude forcing of ice volume and greenhouse gases.

Reduced rainfall drives biomass limitation of long‐term fire activity in Australia’s subtropical sclerophyll forests

AbstractAimTo understand the long‐term drivers of biomass burning in the sclerophyll‐dominated forests of Australia.LocationSwallow Lagoon, North Stradbroke Island, Queensland, Australia.Time periodLast ca. 8 kyr.Major taxa studiedEucalyptus sensu lato, Leptospermum and Casuarinaceae.MethodsHigh‐resolution pollen and charcoal analyses were undertaken on a ca. 8 kyr sediment record and compared with an independent quantitative precipitation reconstruction inferred from leaf carbon isotopes from the same site. We performed Principal Component Analysis to extract the main vegetation trends around Swallow Lagoon. We then compared vegetation changes to local charcoal records to understand the climate‐vegetation‐fire relationships under different rainfall regimes. The trends in pollen, charcoal and rainfall were analysed using Generalized Additive Models and wavelet coherence.ResultsRelatively high Casuarinaceae pollen abundance and high charcoal influx were found prior to 3.4 ka, during a phase of high rainfall. Between 3.4 and 1.5 ka there was an increase in Leptospermum‐type pollen abundance in concert with a decline in both rainfall and charcoal influx. After 1.5 ka low rainfall was generally maintained and a significant increase in Eucalyptus was detected, along with an increase in microscopic charcoal.Main conclusionsOur study, from a sclerophyll forest setting that is typical of ~30% of Australia's vegetation, provides a unique example of complex climate‐biomass‐fire feedbacks and highlights biomass limitation of fire activity. High rainfall at Swallow Lagoon is linked to dense Casuarinaceae‐dominated forests and high fire activity prior to 3.4 ka. Between 3.4 and 1.5 ka, a decline in rainfall leads to reduced biomass burning during a phase dominated by shrub communities. After 1.5 ka, a change in fuel type was related to a transition to an open eucalypt forest and greater microscopic charcoal influx.

Quantitative precipitation reconstruction in the east-central monsoonal China since the late glacial period

Quantitative reconstruction of past precipitation for the monsoonal region in east-central China is of necessity in understanding East Asian Summer Monsoon (EASM) evolution. In this study, pollen-based quantitative reconstructions of the precipitation for Dajiuhu area since the late glacial period were produced by two appropriate approaches: Weighted Averaged Partial Least Squares (WAPLS) and Locally-Weighted Weighted-Averaging (LWWA). After numerical analysis, a modern pollen training set with a radius of 1000 km around the Dajiuhu Lake was established and two precipitation variables were selected for reconstruction. Mean Annual Precipitation (MAP) and Mean Summer Precipitation (MSP) reconstructed based on the two approaches had relatively high consistency (though the reconstructed value of LWWA is lower than that of WAPLS): (1) in the period of 16.0 ipitation was 10% lower than the mean value for the Holocene; (2) in the period of 10.0 cal ka BP - 7.0 cal ka BP, the precipitation reached an optima of the Holocene; (3) in the period of 7.0 cal ka BP - 4.0 cal ka BP, the precipitation was considerably lower than the mean of the Holocene; (4) in the period of 4.0 cal ka BP - present day, the precipitation fluctuated relatively drastically around the average line of the Holocene. The results indicated that the maximum intensity of the EASM in the data-covering period of the past ∼16,000 years occurred in the early and middle Holocene, specifically from ∼10.0 cal ka BP to ∼7.0 cal ka BP. On the whole, our quantitative reconstruction results were highly coincident with the other proxy-based reconstructions of the changes in the East Asian monsoon. In the early and middle Holocene period when the monsoon was the strongest, synchronous changes in precipitation promoted regional expansion of mixed coniferous forests and broad-leaved forests. We preliminarily conclude that the periodic seasonal variation of longitudinal solar radiation gradient in summer at the low latitudes of the northern and southern hemispheres was the main controlling factor for precipitation in this region.

North Pacific atmospheric rivers and their influence on western North America at the Last Glacial Maximum

AbstractSouthwestern North America was wetter than present during the Last Glacial Maximum. The causes of increased water availability have been recently debated, and quantitative precipitation reconstructions have been underutilized in model‐data comparisons. We investigate the climatological response of North Pacific atmospheric rivers to the glacial climate using model simulations and paleoclimate reconstructions. Atmospheric moisture transport due to these features shifted toward the southeast relative to modern. Enhanced southwesterly moisture delivery between Hawaii and California increased precipitation in the southwest while decreasing it in the Pacific Northwest, in agreement with reconstructions. Coupled climate models that are best able to reproduce reconstructed precipitation changes simulate decreases in sea level pressure across the eastern North Pacific and show the strongest southeastward shifts of moisture transport relative to a modern climate. Precipitation increases of ∼1 mm d−1, due largely to atmospheric rivers, are of the right magnitude to account for reconstructed pluvial conditions in parts of southwestern North America during the Last Glacial Maximum.

East Asian summer monsoon precipitation variability since the last deglaciation.

The lack of a precisely-dated, unequivocal climate proxy from northern China, where precipitation variability is traditionally considered as an East Asian summer monsoon (EASM) indicator, impedes our understanding of the behaviour and dynamics of the EASM. Here we present a well-dated, pollen-based, ~20-yr-resolution quantitative precipitation reconstruction (derived using a transfer function) from an alpine lake in North China, which provides for the first time a direct record of EASM evolution since 14.7 ka (ka = thousands of years before present, where the “present” is defined as the year AD 1950). Our record reveals a gradually intensifying monsoon from 14.7–7.0 ka, a maximum monsoon (30% higher precipitation than present) from ~7.8–5.3 ka, and a rapid decline since ~3.3 ka. These insolation-driven EASM trends were punctuated by two millennial-scale weakening events which occurred synchronously to the cold Younger Dryas and at ~9.5–8.5 ka, and by two centennial-scale intervals of enhanced (weakened) monsoon during the Medieval Warm Period (Little Ice Age). Our precipitation reconstruction, consistent with temperature changes but quite different from the prevailing view of EASM evolution, points to strong internal feedback processes driving the EASM, and may aid our understanding of future monsoon behaviour under ongoing anthropogenic climate change.

3800 Years of Quantitative Precipitation Reconstruction from the Northwest Yucatan Peninsula

Precipitation over the last 3800 years has been reconstructed using modern pollen calibration and precipitation data. A transfer function was then performed via the linear method of partial least squares. By calculating precipitation anomalies, it is estimated that precipitation deficits were greater than surpluses, reaching 21% and <9%, respectively. The period from 50 BC to 800 AD was the driest of the record. The drought related to the abandonment of the Maya Preclassic period featured a 21% reduction in precipitation, while the drought of the Maya collapse (800 to 860 AD) featured a reduction of 18%. The Medieval Climatic Anomaly was a period of positive phases (3.8–7.6%). The Little Ice Age was a period of climatic variability, with reductions in precipitation but without deficits.

Quantitative climate reconstruction linking meteorological, limnological and XRF core scanner datasets: the Lake Sanabria case study, NW Spain

Monthly limnological monitoring in Lake Sanabria (Spain) since 1986 provided a unique opportunity to test relationships among climate, hydrology and lake dynamics and how they are recorded in the lake sediments. Four datasets were employed: (1) meteorological (monthly maximum and minimum air temperature and total precipitation), (2) limnological (Secchi disk, water temperature, conductivity, pH, dissolved oxygen, nitrate, silicon, total and reactive phosphorus, and total chlorophylls and chlorophyll a), (3) hydrological (Tera River water input and output), and (4) XRF core scanner measurements carried out in short cores. Linear models between the different dataset variables allowed us to characterize the climate signal transmission from one to the other and cross-correlation analyses permitted us to identify the different response times (if any) between them. Principal Component Analyses (PCA) of the limnological and geochemical datasets allowed us to identify the main processes that link lake dynamics, primarily nutrient supply and organic productivity, with some sedimentological processes, e.g. organic matter and phosphorus accumulation. Sediment chronology was established by gamma spectrometry (210Pb). Water input to Lake Sanabria is controlled mostly by the Tera River input and is linked directly to precipitation. Response of the Lake Sanabria water budget to climate oscillations is immediate, as the strongest correlation between these two datasets occurs with no lag time. PCA of the limnological dataset indicated that most of the variance is related to nutrient input, and comparison with the Tera River water discharge shows that nutrient input was controlled mainly by oscillations in the hydrological balance. The lag time between the hydrological and limnological datasets is 1 month. The PCA of the XRF core scanner dataset showed that the principal process that controls the chemical composition of the Lake Sanabria sediments is related to sediment and nutrient delivery from the Tera River and organic productivity. Comparison of the nutrient input reconstructed using the limnological dataset and the XRF core scanner data indicated that the sediments act as a low-pass filter, smoothing the climate signal. It was, however, possible to establish the link between these datasets, and obtain a quantitative reconstruction of precipitation for the 1959–2005 AD period that captures the regional variability. This quantitative precipitation reconstruction suggests it is possible to obtain accurate climate reconstructions using non-laminated sediments.

An extended network of documentary data from South America and its potential for quantitative precipitation reconstructions back to the 16th century

In South America (SA) several documentary based climate time series exist, some of them extending back to the 16th century. Most of these records end in the 19th century, and can not be calibrated against instrumental data. Here, we used the newspaper “Los Andes” from Mendoza, Argentina, to extend documentary based indices of Mendoza precipitation and Central Andes snow depth to the late 20th century. A statistical approach to create “pseudo documentary” 20th century data was applied to prolong eight other documentary records. Increased variability of the hydrological cycle in the Central Andes and prevailing periods of wet and dry years in Mendoza suggest that the 20th century is extraordinary in the context of the last 400 years. The final set of extended documentaries explains significant portions of SA precipitation variability in large areas between 20°S and 40°S and can therefore improve the network of annually resolved precipitation proxies.

Dendrochronological analysis of the response of tamarack (Larix laricina) to climate and larch sawfly (Pristiphora erichsonii) infestations in central Saskatchewan

The potential for deriving long records of climate and larch sawfly (Pristiphora erichsonii) infestation for central Canada from tamarack (Larix laricina) ring-width series was investigated. Analysis was based on a 314-year chronology developed from tamarack at a wetland site in Prince Albert National Park, Saskatchewan. The tamarack chronology was compared with a non-host 240-year black spruce (Picea mariana) chronology derived from trees at the same site and with historical records of sawfly infestation in the Prairie provinces. The two chronologies are similar to the late 1800s, after which there appears to be a decoupling. The existence of five major growth suppression events in larch (three preceded by light rings) from ~1880, compared with only two minor growth anomalies in the tree ring record prior to this time (1757-1880), may indicate either i) that tamarack has been relatively recently affected by the introduction of larch sawfly into the region in the late 1800s or ii) that 20th century outbreaks of larch sawfly have been more virulent, perhaps due to increasing temperatures and moisture stress. Climate-growth analysis indicates that larch trees at this location are sensitive to moisture, with low precipitation limiting annual growth. Possibly, increased moisture stress has also made larch more susceptible to the effects of defoliation. Because multiple signals coexist in the tamarack chronology over the 20th century, and there is a high frequency of missing rings, quantitative precipitation reconstruction using trees from this region presents difficulties.

Middle Holocene dry period in the northern Midwestern United States: Lake levels and pollen stratigraphy

Four cores from Lake Mendota in the Yahara River valley of south-central Wisconsin provide pollen, charcoal, and sediment-stratigraphic evidence of a middle Holocene dry period in the northern Midwest. The lake level was lower between about 6500 and 3500 yr B.P. indicating that runoff from the upper Yahara River basin may have ceased during the drier seasons of the year. Derived estimates of precipitation between 6500 and 3500 yr B.P. indicate a decrease of about 10% (down to about 700 mm) from the present precipitation value of 800 mm. A warming between 6500 and 3500 yr B.P. is also interpreted based on a change of vegetation from rich mesophytic forest before 6500 yr B.P. to Quercus savanna, with increased charcoal abundances after that time. After 3500 yr B.P., a closed Quercus forest and decreased charcoal suggest a cooler and wetter climate. The qualitative paleoecological interpretations, quantitative precipitation reconstructions based on pollen from the region (including the Lake Mendota data), and estimates of hydrologic budget based on lake-level changes, all show indications of a dry and warm middle Holocene. Evidence from a large regional array of sites also supports these interpretations.