scholarly journals Geomorphological approach to the river runoff evaluation in the geological past (рaper 5. Comparison of the estimates by different methods)

2019 ◽  
pp. 66-79
Author(s):  
A. Yu. Sidorchuk ◽  
A. V. Panin ◽  
O. K. Borisova
Keyword(s):  
Water Resources ◽  
Water Flow ◽  
Climate Changes ◽  
Annual Runoff ◽  
Fossil Flora ◽  
Average Error ◽  
Flow Estimation ◽  
The Past ◽  
Geological Past

The estimates of water flow in the paleorivers with known paleochannel morphometry was compared with basic hydrological and climatic indicators found by paleogeographic analogy in the regions-analogues, determined by fossil flora analysis from the Holocene (from the present to 10 thousand years ago), the Late Valday (17–18 thousand years ago) and before the Eemian (~140 thousand years ago) deposits. Comparison of annual runoff depth obtained by regime equations and equations of hydraulics and taken from the hydrological maps in the regions-analogues, showed quite satisfactory compliance. Relative error of comparison for the different objects is in the range of ±11–23%, which does not exceed the average error of water flow estimation by each of these techniques separately. However, the error of ±20% is significant and geomorphological approaches can be applied only for the cases of sufficient changes in the water flow of ancient rivers (twice or more) and for long-term periods. Nevertheless, the use of geomorphological approaches and the method of paleogeographic analogy is now one of the main ways to reconstruct water resources in the past and to construct water resources scenarios for possible future climate changes.

How the Desert got a Past: A History of Quaternary Research in Australia’s Deserts

2014 ◽  
Vol 25 (2) ◽  
pp. 172 ◽  
Author(s):  
Mike Smith
Keyword(s):  
Climate Changes ◽  
Conceptual Space ◽  
The Past ◽  
History Of ◽  
The 1960S

This paper examines how the past of desert landscapes has been interpreted since European explorers and scientists first encountered them. It charts the research that created the conceptual space within which archaeologists and Quaternarists now work. Studies from the 1840s–1960s created the notion of a ‘Great Australian Arid Period'. The 1960s studies of Lake Mungo and the Willandra Lakes by Jim Bowler revealed the cyclical nature of palaeolakes, that changed with climate changes in the Pleistocene, and the complexity of desert pasts. SLEADS and other researchers in the 1980s used thermoluminescence techniques that showed further complexities in desert lands beyond the Willandra particularly through new studies in the Strzelecki and Simpson Dunefields, Lake Eyre, Lake Woods and Lake Gregory. Australian deserts are varied and have very different histories. Far from ‘timeless lands', they have carried detailed information about long-term climate changes on continental scales.

The «rainfall-runoff» system and its long-term fluctuations in the Siverskyi Donets River Basin (Ukraine)

2021 ◽  
Author(s):  
Hanna Bolbot ◽  
Vasyl Grebin
Keyword(s):  
Climate Change ◽  
Water Resources ◽  
River Basin ◽  
Air Temperature ◽  
River Runoff ◽  
Annual Runoff ◽  
Annual Precipitation ◽  
Spring Flood ◽  
Current Period

<p>The current patterns estimation of the water regime under climate change is one of the most urgent tasks in Ukraine and the world. Such changes are determined by fluctuations in the main climatic characteristics - precipitation and air temperature, which are defined the value of evaporation. These parameters influence on the annual runoff distribution and long-term runoff fluctuations. In particular, the annual precipitation redistribution is reflected in the corresponding changes in the river runoff.<br>The assessment of the current state and nature of changes in precipitation and river runoff of the Siverskyi Donets River Basin was made by comparing the current period (1991-2018) with the period of the climatological normal (1961-1990).<br>In general, for this area, it was defined the close relationship between the amount of precipitation and the annual runoff. Against the background of insignificant (about 1%) increase of annual precipitation in recent decades, it was revealed their redistribution by seasons and separate months. There is a decrease in precipitation in the cold period (November-February). This causes (along with other factors) a decrease in the amount of snow and, accordingly, the spring flood runoff. There are frequent cases of unexpressed spring floods of the Siverskyi Donets River Basin. The runoff during March-April (the period of spring flood within the Ukrainian part of the basin) decreased by almost a third.<br>The increase of precipitation during May-June causes a corresponding (insignificant) increase in runoff in these months. The shift of the maximum monthly amount of precipitation from May (for the period 1961-1990) to June (in the current period) is observed.<br>There is a certain threat to water supply in the region due to the shift in the minimum monthly amount of precipitation in the warm period from October to August. Compared with October, there is a higher air temperature and, accordingly, higher evaporation in August, which reduces the runoff. Such a situation is solved by rational water resources management of the basin. The possibility of replenishing water resources in the basin through the transfer runoff from the Dnieper (Dnieper-Siverskyi Donets channel) and the annual runoff redistribution in the reservoir system causes some increase in the river runoff of summer months in recent decades. This is also contributed by the activities of the river basin management structures, which control the maintenance water users' of minimum ecological flow downstream the water intakes and hydraulic structures in the rivers of the basin.<br>Therefore, in the period of current climate change, the annual runoff distribution of the Siverskyi Donets River Basin has undergone significant changes, which is related to the annual precipitation redistribution and anthropogenic load on the basin.</p>

scholarly journals Characteristics of cold–warm variation in the Hetao region and its surrounding areas in China during the past 5000 years

2010 ◽  
Vol 6 (4) ◽  
pp. 475-481 ◽  
Author(s):  
M.-Q. Li ◽  
Q.-S. Ge ◽  
Z.-X. Hao ◽  
J.-Y. Zheng ◽  
S.-F. He
Keyword(s):  
Climate Changes ◽  
Mean Value ◽  
Data Series ◽  
Proxy Data ◽  
Average Temperature ◽  
The Past ◽  
The Mean ◽  
Temperature Proxy ◽  
Surrounding Areas

Abstract. Using six long-term temperature proxy data series derived from different natural evidences, including pollens and lake-sediments, we reconstructed a temperature series with a 100-yr time resolution for the past 5000 yr in the Hetao region and its surrounding areas. The resulting series suggests that, on a millennial timescale, temperatures in the region were higher than the mean value of the whole series during the 5000~2600 years before present (yr BP) period, and became relatively low comparing with the average temperature of the whole series after 2600 yr BP. Within these two periods, temperature fluctuations comprising numerous short, multi-centennial intervals also existed. A comparison between our reconstructed series and other series in China and across the Northern Hemisphere indicate that, on a long-term scale, cold–warm variations had been in phase across the whole hemisphere during the past 5000 years; on the century to multi-century scale, the beginning and the ending times varied from region to region, thus implying that climate changes did not occur simultaneously in different regions.

scholarly journals Probabilities of Causation of Climate Changes

2018 ◽  
Vol 31 (14) ◽  
pp. 5507-5524 ◽  
Author(s):  
Alexis Hannart ◽  
Philippe Naveau
Keyword(s):  
Climate Changes ◽  
The Past ◽  
Detection And Attribution ◽  
Mitigation And Adaptation ◽  
Event Attribution ◽  
Long Term Trends ◽  
Earth’S Climate ◽  
Anthropogenic Forcings ◽  
Event Occurrence

Multiple changes in Earth’s climate system have been observed over the past decades. Determining how likely each of these changes is to have been caused by human influence is important for decision making with regard to mitigation and adaptation policy. Here we describe an approach for deriving the probability that anthropogenic forcings have caused a given observed change. The proposed approach is anchored into causal counterfactual theory ( Pearl 2009 ), which was introduced recently, and in fact partly used already, in the context of extreme weather event attribution (EA). We argue that these concepts are also relevant to, and can be straightforwardly extended to, the context of detection and attribution of long-term trends associated with climate change (D&A). For this purpose, and in agreement with the principle of fingerprinting applied in the conventional D&A framework, a trajectory of change is converted into an event occurrence defined by maximizing the causal evidence associated to the forcing under scrutiny. Other key assumptions used in the conventional D&A framework, in particular those related to numerical model error, can also be adapted conveniently to this approach. Our proposal thus allows us to bridge the conventional framework with the standard causal theory, in an attempt to improve the quantification of causal probabilities. An illustration suggests that our approach is prone to yield a significantly higher estimate of the probability that anthropogenic forcings have caused the observed temperature change, thus supporting more assertive causal claims.

scholarly journals Evaluation of water resources changes of the Mountain Dniester in 20th century following the RCP8.5 scenario and based on the “climate-runoff” model

2021 ◽  
pp. 48-64
Author(s):  
N. S. Loboda ◽  
M. O. Kozlov ◽  
І. V. Katynska
Keyword(s):  
Global Warming ◽  
Water Resources ◽  
Balance Equation ◽  
Heat Balance ◽  
Climatic Factors ◽  
Annual Runoff ◽  
Climatic Conditions ◽  
Mountain Part ◽  
Runoff Model

The relevance of the research consists in the need for evaluating the water resources changes of the Dniester due to global warming. The mountain part of the Dniester Basin is a zone of the river's runoff formation that determines its water content. The subject of research includes a process of climate changes and their impact on the water resources of the Mountain Dniester’s catchments. The research focuses on determining the water resources changes under current and possible future climatic conditions represented by climatic scenarios. The research aims at evaluating the water resources changes of the mountain part of the Dniester’s catchment area at the present and in the future by the mid-21 st century (2021-2050) based on the “climate-runoff” model using meteorological observations data (up to 2018 inclusive) and scenario data (averaged data based on 14 mathematical models of the CORDEX project, RCP8.5 scenario). During the research the resources of humidification, heat (heat equivalent) and water content for modern (1989-2018) and scenario (RCP8.5, 2021-2050) climatic conditions based on application of the "climate-runoff" model were evaluated. The theoretical basis for estimating the natural (undisturbed by water management) annual runoff in this model is represented by the water-heat balance equation. The meteorological characteristics (average monthly air temperatures and precipitation) serve as input data. The runoff calculated using the water-heat balance equation is called a climatic runoff. One of the peculiarities of the research consists in the use of the vertical zoning law with respect to distribution of runoff and climatic factors of its formation. During the comparative analysis the dependence of annual runoff norms on height of the Mountain Dniester’s terrain specified in modern regulatory documents served as a basic dependence. Such dependence reflects an altitude-dependant distribution of runoff for the climatic conditions that preceded the significant impact of global warming on air temperature (until 1989). The analysis of the dependences of average long-term values of the annual runoff depending on the terrain altitude showed that the runoff changes for two studied periods (before and after 1989) are within ±12,3%. The analysis of the graphs of chronological course of annual water flow of the mountain tributaries of the Dniester made it possible to confirm the absence of statistically significant trends in their fluctuations. According to the RCP8.5 climate scenario over the period of 2021-2050 and following the results of calculations based on the “climate-runoff” model, the dependences of the average long-term altitude-related values of climatic factors and climatic runoff were retrieved. It was found that the effects of global warming decrease with increasing altitude. In the foothills (up to 200 m) the annual precipitation decreases (up to 11%), the maximum possible evaporation increases (up to 17%) and water resources decrease (up to 46%). Heat resources cease to increase and water resources cease to reduce at the altitudes over 800 m. The average deviation of the scenario and baseline values for precipitation over the estimated period will amount to 2.41% for precipitation, 5.79% for maximum possible evaporation and 8.87% for water resources. Thus, reduction of water resources in the mountainous part of the Dniester by the mid-21 st century will be insignificant. When evaluating the current state of water resources of the Mountain Dniester no significant changes were discovered, thereby not contradicting the other authors’ data.

scholarly journals Characteristics of cold-warm variation in the Hetao region and its surrounding areas in China during the past 5000 yr

2010 ◽  
Vol 6 (1) ◽  
pp. 1-18
Author(s):  
M. Li ◽  
Q. Ge ◽  
Z. Hao ◽  
J. Zheng ◽  
S. He
Keyword(s):  
Climate Changes ◽  
Mean Value ◽  
Data Series ◽  
Proxy Data ◽  
Average Temperature ◽  
The Past ◽  
The Mean ◽  
Temperature Proxy ◽  
Surrounding Areas

Abstract. Using six long-term temperature proxy data series derived from different natural evidences, including pollens and lake-sediments, we reconstructed a temperature series with a 100-year time resolution for the past 5000 yr in the Hetao region and its surrounding areas. The resulting series suggests that, on a millennial timescale, temperatures in the region were higher than the mean value of the whole series during the 5000~2600 yr before present (yr BP) period, and became relatively low comparing with the average temperature of the whole series after 2600 yr BP. Within these two periods, temperature fluctuations comprising numerous short, multi-centennial intervals also existed. A comparison between our reconstructed series and other series in China and across the Northern Hemisphere indicate that, on a long-term scale, cold–warm variations had been in phase across the whole hemisphere during the past 5000 yr; on the century to multi-century scale, the beginning and the ending times varied from region to region, thus implying that climate changes did not occur simultaneously in different regions.

Climate change and declining fertility rate in Malaysia: the possible connexions

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Ravindran Jegasothy ◽  
Pallav Sengupta ◽  
Sulagna Dutta ◽  
Ravichandran Jeganathan
Keyword(s):  
Climate Change ◽  
Climate Changes ◽  
Asian Country ◽  
Fertility Rate ◽  
Long Term Effects ◽  
The Past ◽  
Fertility Status ◽  
Quality Of Food

AbstractClimate change is an incessant global phenomenon and has turned contentious in the present century. Malaysia, a developing Asian country, has also undergone significant vicissitudes in climate, which has been projected with significant deviations in forthcoming decades. As per the available studies, climate changes may impact on the fertility, either via direct effects on the gonadal functions and neuroendocrine regulations or via several indirect effects on health, socioeconomic status, demeaning the quality of food and water. Malaysia is already observing a declining trend in the Total fertility rate (TFR) over the past few decades and is currently recorded below the replacement level of 2.1 which is insufficient to replace the present population. Moreover, climate changes reportedly play a role in the emergence and cessation of various infectious diseases. Besides its immediate effects, the long-term effects on health and fertility await to be unveiled. Despite the huge magnitude of the repercussion of climate changes in Malaysia, research that can explain the exact cause of the present reduction in fertility parameters in Malaysia or any measures to preserve the national population is surprisingly very scarce. Thus, the present review aims to elucidate the possible missing links by which climate changes are impairing fertility status in Malaysia.

scholarly journals Truncated bimodal latitudinal diversity gradient in early Paleozoic phytoplankton

2021 ◽  
Vol 7 (15) ◽  
pp. eabd6709
Author(s):  
Axelle Zacaï ◽  
Claude Monnet ◽  
Alexandre Pohl ◽  
Grégory Beaugrand ◽  
Gary Mullins ◽  
...  
Keyword(s):  
Species Richness ◽  
Climate Changes ◽  
Sea Surface ◽  
Marine Phytoplankton ◽  
Sampling Effort ◽  
Early Paleozoic ◽  
Latitudinal Diversity Gradient ◽  
Diversity Gradient ◽  
Geological Past

The latitudinal diversity gradient (LDG)—the decline in species richness from the equator to the poles—is classically considered as the most pervasive macroecological pattern on Earth, but the timing of its establishment, its ubiquity in the geological past, and explanatory mechanisms remain uncertain. By combining empirical and modeling approaches, we show that the first representatives of marine phytoplankton exhibited an LDG from the beginning of the Cambrian, when most major phyla appeared. However, this LDG showed a single peak of diversity centered on the Southern Hemisphere, in contrast to the equatorial peak classically observed for most modern taxa. We find that this LDG most likely corresponds to a truncated bimodal gradient, which probably results from an uneven sediment preservation, smaller sampling effort, and/or lower initial diversity in the Northern Hemisphere. Variation of the documented LDG through time resulted primarily from fluctuations in annual sea-surface temperature and long-term climate changes.

Wavelet Analysis of Natural Annual Runoff in Dongjiang River

2011 ◽  
Vol 383-390 ◽  
pp. 5158-5165
Author(s):  
Jing Li ◽  
Qiu Wen Chen ◽  
Da Mei Li
Keyword(s):  
Water Resources ◽  
Wavelet Coefficient ◽  
Annual Runoff ◽  
Times Series ◽  
The Past ◽  
Dongjiang River ◽  
The Social ◽  
Wavelet Variance ◽  
Wavelet Analyses ◽  
Multi Scales

To maintain the ecosystem health and guarantee the social-economic water demand in the Dongjiang river basin, proper management of the water resources is essential. This research introduced the Morlet Wavelet analyses method to investigate the patterns of the past 45 years runoff times series of the main gauges in the Dongjiang River. The general trend and the changing characteristics in both time domain and frequency domain at different scales were revealed. The results were verified by the real part of the Wavelet coefficient and the Wavelet variance. The study discovered that the runoff in the basin exhibited multi-scales of main circle, synchronization and declining. The results could provide valuable information for the management of the water resources and ecosystem of the Dongjiang River.

Sign in / Sign up

Export Citation Format

Share Document