The effect of permafrost area and types on flux and composition of dissolved organic matter in stream from alpine catchments, northeastern Qinghai-Tibet Plateau

2021 ◽  
Author(s):  
Yanxi Pan ◽  
Ziyong Sun
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
River Water ◽  
Frozen Soil ◽  
Tibet Plateau ◽  
Vegetation Coverage ◽  
Permafrost Degradation ◽  
Terrestrial Organic Matter ◽  
The Impact ◽  
Qinghai Tibet Plateau

<p>Understanding optical characteristics, composition and source of dissolved organic matter (DOM) in rivers is important for region and global carbon cycle, especially in the inland rivers of the Qinghai-Tibet Plateau. In order to understand the impact of permafrost degradation on river DOM output under the background of climate warming, we selected 34 typical sub-basins in the upper reaches of the Heihe River basin on the Qinghai-Tibet Plateau according to the different proportion of permafrost area in the basin. Water samples were collected at the outlet of each sub-basin in October 2018, January, April and July 2019, respectively. The variations of DOM structure and source identification in different permafrost basin were investigated using UV–visible absorbance and fluorescence spectroscopy. The results showed that: (1) The concentration of C1 and C2 components and the values ​​of SUVA<sub>254</sub>, HIX and FI increased with the decrease of the percentage of permafrost area. , Indicating that with the degradation of frozen soil, the runoff path deepens, and more terrestrial organic matter is dissolved into the water body, which increases the terrestrial DOM in the river water, which in turn leads to the increase of DOM concentration, humification degree and aromaticity; (2) As the proportion of permafrost area decreases, the S<sub>R</sub> value shows a decreasing trend, indicating that the DOM of rivers in permafrost regions has the characteristics of low molecular weight and low humic acid, while the DOM of rivers in seasonally frozen soil regions is the opposite, indicating a frozen soil Melting may lead to the increase of terrestrial DOM in river water, and the increase in the depth of freeze-thaw cycle may release aromatic substances containing fused ring structure in frozen soil, which will enter the river with runoff, resulting in increased aromaticity and molecular weight of DOM in river water; (3) The concentrations of C1 and C2 components are positively correlated with vegetation coverage, and vegetation coverage is negatively correlated with the percentage of permafrost area. It shows that the degradation of frozen soil will increase the coverage of vegetation, thereby increasing the DOM from terrestrial sources. This study shows that the optical characteristics, composition and source of DOM have important indications for the degradation of permafrost under the background of global warming.</p>

scholarly journals PIC v1.3: comprehensive R package for computing permafrost indices with daily weather observations and atmospheric forcing over the Qinghai–Tibet Plateau

2018 ◽  
Vol 11 (6) ◽  
pp. 2475-2491 ◽  
Author(s):  
Lihui Luo ◽  
Zhongqiong Zhang ◽  
Wei Ma ◽  
Shuhua Yi ◽  
Yanli Zhuang
Keyword(s):  
Ground Surface ◽  
R Package ◽  
Frozen Soil ◽  
Tibet Plateau ◽  
Trend Test ◽  
Active Layer Thickness ◽  
Permafrost Degradation ◽  
Spatial Trends ◽  
The Impact ◽  
Qinghai Tibet Plateau

Abstract. An R package was developed for computing permafrost indices (PIC v1.3) that integrates meteorological observations, gridded meteorological datasets, soil databases, and field measurements to compute the factors or indices of permafrost and seasonal frozen soil. At present, 16 temperature- and depth-related indices are integrated into the PIC v1.3 R package to estimate the possible trends of frozen soil in the Qinghai–Tibet Plateau (QTP). These indices include the mean annual air temperature (MAAT), mean annual ground surface temperature (MAGST), mean annual ground temperature (MAGT), seasonal thawing–freezing n factor (nt∕nf), thawing–freezing degree-days for air and the ground surface (DDTa∕DDTs∕DDFa∕DDFs), temperature at the top of the permafrost (TTOP), active layer thickness (ALT), and maximum seasonal freeze depth. PIC v1.3 supports two computational modes, namely the stations and regional calculations that enable statistical analysis and intuitive visualization of the time series and spatial simulations. Datasets of 52 weather stations and a central region of the QTP were prepared and simulated to evaluate the temporal–spatial trends of permafrost with the climate. More than 10 statistical methods and a sequential Mann–Kendall trend test were adopted to evaluate these indices in stations, and spatial methods were adopted to assess the spatial trends. Multiple visual methods were used to display the temporal and spatial variability of the stations and region. Simulation results show extensive permafrost degradation in the QTP, and the temporal–spatial trends of the permafrost conditions in the QTP are close to those of previous studies. The transparency and repeatability of the PIC v1.3 package and its data can be used and extended to assess the impact of climate change on permafrost.

scholarly journals PIC: Comprehensive R package for permafrost indices computing with daily weather observations and atmospheric forcing over the Qinghai–Tibet Plateau

2018 ◽  
Author(s):  
Lihui Luo ◽  
Zhongqiong Zhang ◽  
Wei Ma ◽  
Shuhua Yi ◽  
Yanli Zhuang
Keyword(s):  
Ground Surface ◽  
R Package ◽  
Frozen Soil ◽  
Tibet Plateau ◽  
Climate Simulation ◽  
Trend Test ◽  
Active Layer Thickness ◽  
Permafrost Degradation ◽  
The Impact ◽  
Qinghai Tibet Plateau

Abstract. An R package permafrost indices computing (PIC) was developed, which integrates meteorological observations, remote sensing data, and field measurements to compute the factors or indices of permafrost and seasonal frozen soil. At present, 16 temperature/depth-related indices are integrated into the R package PIC to estimate the possible change trends of frozen soil in the Qinghai–Tibet Plateau (QTP). These indices include the mean annual air temperature, mean annual ground surface temperature, mean annual ground temperature, seasonal thawing/freezing n factor (nt/nf), thawing/freezing degree-days of air and ground surface (DDTa/DDTs/DDFa/DDFs), temperature at the top of the permafrost, active layer thickness, and maximum seasonal freeze depth. The PIC package supports two computational modes, namely, the stations and region calculation that enables statistical analysis and intuitive visualization on the time series and spatial simulations. Over 10 statistical methods were adopted to evaluate these indices in stations, and a sequential Mann-Kendall trend test and spatial trend method were adopted. Multiple visual manners display the temporal and spatial variabilities on the stations and region. The data sets of 52 weather stations and a central region of QTP were prepared and simulated to evaluate the temporal–spatial change trends of permafrost with the climate. Simulation results show extensive permafrost degradation in QTP, and the temporal–spatial trends of the permafrost conditions in QTP were consistent with those of previous studies. The PIC package will serve engineering applications and can be used to assess the impact of climate change on permafrost.

scholarly journals Spatiotemporal transformation of dissolved organic matter along an alpine stream flow path on the Qinghai–Tibet Plateau: importance of source and permafrost degradation

2018 ◽  
Vol 15 (21) ◽  
pp. 6637-6648 ◽  
Author(s):  
Yinghui Wang ◽  
Robert G. M. Spencer ◽  
David C. Podgorski ◽  
Anne M. Kellerman ◽  
Harunur Rashid ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Molecular Level ◽  
Tibet Plateau ◽  
Permafrost Degradation ◽  
Hydrological Conditions ◽  
14C Age ◽  
Alpine Stream ◽  
Qinghai Tibet Plateau

Abstract. The Qinghai–Tibet Plateau (QTP) accounts for approximately 70 % of global alpine permafrost and is an area sensitive to climate change. The thawing and mobilization of ice-rich and organic-carbon-rich permafrost impact hydrologic conditions and biogeochemical processes on the QTP. Despite numerous studies of Arctic permafrost, there are no reports to date for the molecular-level in-stream processing of permafrost-derived dissolved organic matter (DOM) on the QTP. In this study, we examine temporal and spatial changes of DOM along an alpine stream (3850–3207 m above sea level) by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), accelerator mass spectrometry (AMS) and UV–visible spectroscopy. Compared to downstream sites, dissolved organic matter (DOM) at the headstream site exhibited older radiocarbon age, higher mean molecular weight, higher aromaticity and fewer highly unsaturated compounds. At the molecular level, 6409 and 1345 formulas were identified as unique to the active layer (AL) leachate and permafrost layer (PL) leachate, respectively. Comparing permafrost leachates to the downstream site, 59 % of AL-specific formulas and 90 % of PL-specific formulas were degraded, likely a result of rapid in-stream degradation of permafrost-derived DOM. From peak discharge in the summer to low flow in late autumn, the DOC concentration at the headstream site decreased from 13.9 to 10.2 mg L−1, while the 14C age increased from 745 to 1560 years before present (BP), reflecting an increase in the relative contribution of deep permafrost carbon due to the effect of changing hydrological conditions over the course of the summer on the DOM source (AL vs. PL). Our study thus demonstrates that hydrological conditions impact the mobilization of permafrost carbon in an alpine fluvial network, the signature of which is quickly lost through in-stream mineralization and transformation.

scholarly journals The impact of the freeze–melt cycle of land-fast ice on the distribution of dissolved organic matter in the Laptev and East Siberian seas (Siberian Arctic)

2021 ◽  
Vol 18 (12) ◽  
pp. 3637-3655
Author(s):  
Jens A. Hölemann ◽  
Bennet Juhls ◽  
Dorothea Bauch ◽  
Markus Janout ◽  
Boris P. Koch ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Sea Ice ◽  
River Water ◽  
Set Covering ◽  
The Arctic ◽  
Permafrost Degradation ◽  
Spring Freshet ◽  
Fast Ice ◽  
The Impact

Abstract. Permafrost degradation in the catchment of major Siberian rivers, combined with higher precipitation in a warming climate, could increase the flux of terrestrially derived dissolved organic matter (tDOM) into the Arctic Ocean (AO). Each year, ∼ 7.9 Tg of dissolved organic carbon (DOC) is discharged into the AO via the three largest rivers that flow into the Laptev Sea (LS) and East Siberian Sea (ESS). A significant proportion of this tDOM-rich river water undergoes at least one freeze–melt cycle in the land-fast ice that forms along the coast of the Laptev and East Siberian seas in winter. To better understand how growth and melting of land-fast ice affect dissolved organic matter (DOM) dynamics in the LS and ESS, we determined DOC concentrations and the optical properties of coloured dissolved organic matter (CDOM) in sea ice, river water and seawater. The data set, covering different seasons over a 9-year period (2010–2019), was complemented by oceanographic measurements (T, S) and determination of the oxygen isotope composition of the seawater. Although removal of tDOM cannot be ruled out, our study suggests that conservative mixing of high-tDOM river water and sea-ice meltwater with low-tDOM seawater is the major factor controlling the surface distribution of tDOM in the LS and ESS. A case study based on data from winter 2012 and spring 2014 reveals that the mixing of about 273 km3 of low-tDOM land-fast-ice meltwater (containing ∼ 0.3 Tg DOC) with more than 200 km3 of high-tDOM Lena River water discharged during the spring freshet (∼ 2.8 Tg DOC yr−1) plays a dominant role in this respect. The mixing of the two low-salinity surface water masses is possible because the meltwater and the river water of the spring freshet flow into the southeastern LS at the same time every year (May–July). In addition, budget calculations indicate that in the course of the growth of land-fast ice in the southeastern LS, ∼ 1.2 Tg DOC yr−1 (± 0.54 Tg) can be expelled from the growing ice in winter, together with brines. These DOC-rich brines can then be transported across the shelves into the Arctic halocline and the Transpolar Drift Current flowing from the Siberian Shelf towards Greenland. The study of dissolved organic matter dynamics in the AO is important not only to decipher the Arctic carbon cycle but also because CDOM regulates physical processes such as radiative forcing in the upper ocean, which has important effects on sea surface temperature, water column stratification, biological productivity and UV penetration.

scholarly journals Importance of active layer freeze-thaw cycles on the riverine dissolved carbon export on the Qinghai-Tibet Plateau permafrost region

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e7146 ◽  
Author(s):  
Chunlin Song ◽  
Genxu Wang ◽  
Tianxu Mao ◽  
Xiaopeng Chen ◽  
Kewei Huang ◽  
...  
Keyword(s):  
Active Layer ◽  
Carbonic Acid ◽  
Tibet Plateau ◽  
Vegetation Coverage ◽  
Permafrost Region ◽  
Permafrost Degradation ◽  
Carbon Export ◽  
Dissolved Carbon ◽  
Total Runoff ◽  
Qinghai Tibet Plateau

The Qinghai-Tibet Plateau (QTP) is experiencing severe permafrost degradation, which can affect the hydrological and biogeochemical processes. Yet how the permafrost change affects riverine carbon export remains uncertain. Here, we investigated the seasonal variations of dissolved inorganic and organic carbon (DIC and DOC) during flow seasons in a watershed located in the central QTP permafrost region. The results showed that riverine DIC concentrations (27.81 ± 9.75 mg L−1) were much higher than DOC concentrations (6.57 ± 2.24 mg L−1). DIC and DOC fluxes were 3.95 and 0.94 g C m−2 year−1, respectively. DIC concentrations increased from initial thaw (May) to freeze period (October), while DOC concentrations remained relatively steady. Daily dissolved carbon concentrations were more closely correlated with baseflow than that with total runoff. Spatially, average DIC and DOC concentrations were positively correlated with vegetation coverage but negatively correlated with bare land coverage. DIC concentrations increased with the thawed and frozen depths due to increased soil interflow, more thaw-released carbon, more groundwater contribution, and possibly more carbonate weathering by soil CO2 formed carbonic acid. The DIC and DOC fluxes increased with thawed depth and decreased with frozen layer thickness. The seasonality of riverine dissolved carbon export was highly dependent on active layer thawing and freezing processes, which highlights the importance of changing permafrost for riverine carbon export. Future warming in the QTP permafrost region may alter the quantity and mechanisms of riverine carbon export.

Processes and modes of permafrost degradation on the Qinghai-Tibet Plateau

2009 ◽  
Vol 53 (1) ◽  
pp. 150-158 ◽  
Author(s):  
JiChun Wu ◽  
Yu Sheng ◽  
QingBai Wu ◽  
Zhi Wen
Keyword(s):  
Tibet Plateau ◽  
Permafrost Degradation ◽  
Qinghai Tibet Plateau

Heat Effect Analysis of Buried Oil Pipeline in the Qinghai-Tibet Plateau

2014 ◽  
Vol 501-504 ◽  
pp. 211-217
Author(s):  
Wei Bo Liu ◽  
Wen Bing Yu ◽  
Xin Yi ◽  
Lin Chen
Keyword(s):  
Temperature Field ◽  
Frozen Soil ◽  
Operating Conditions ◽  
Tibet Plateau ◽  
Soil Mechanic ◽  
Insulation Layer ◽  
Effect Analysis ◽  
Oil Pipeline ◽  
Permafrost Table ◽  
Qinghai Tibet Plateau

The Geermu-Lasa oil pipeline was located in the Qinghai-Tibet Plateau permafrost regions. The building and operating of pipeline will change the temperature field of soil around it, which can lead to changes of frozen soil mechanic properties, and this will induces deformation or even fracture of pipeline. These phenomena will affect the normal transportation of oil. In this paper, temperature field around the pipelines were analyzed due to different pipe diameters and different insulation layer thicknesses in the way of finite element method. The rule of thawing and freezing of soil around the pipeline in an annual cycle was obtained. Artificial permafrost table variations under the pipeline were also obtained due to different operating conditions. For 30cm diameter pipeline with 7cm insulation layer, its artificial permafrost table depth change value is just 0.48m after 30-year running. These analysis results can provide references to the construction of the new Geermu-Lasa oil pipeline.

scholarly journals Characterizing Hydrological Connectivity of Artificial Ditches in Zoige Peatlands of Qinghai-Tibet Plateau

Water ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1364 ◽  
Author(s):  
Zhiwei Li ◽  
Peng Gao ◽  
Yuchi You
Keyword(s):  
Google Earth ◽  
Tibet Plateau ◽  
Annual Rainfall ◽  
Water Volume ◽  
Hydrological Connectivity ◽  
Total Water ◽  
Zoigê Basin ◽  
The Impact ◽  
Qinghai Tibet Plateau ◽  
Peatland Degradation

Peats have the unique ability of effectively storing water and carbon. Unfortunately, this ability has been undermined by worldwide peatland degradation. In the Zoige Basin, located in the northeastern Qinghai-Tibet Plateau, China, peatland degradation is particularly severe. Although climate change and (natural and artificial) drainage systems have been well-recognized as the main factors catalyzing this problem, little is known about the impact of the latter on peatland hydrology at larger spatial scales. To fill this gap, we examined the hydrological connectivity of artificial ditch networks using Google Earth imagery and recorded hydrological data in the Zoige Basin. After delineating from the images of 1392 ditches and 160 peatland patches in which these ditches were clustered, we calculated their lengths, widths, areas, and slopes, as well as two morphological parameters, ditch density (Dd) and drainage ability (Pa). The subsequent statistical analysis and examination of an index defined as the product Dd and Pa showed that structural hydrological connectivity, which was quantitatively represented by the value of this index, decreased when peatland patch areas increased, suggesting that ditches in small patches have higher degrees of hydrological connectivity. Using daily discharge data from three local gauging stations and Manning’s equation, we back-calculated the mean ditch water depths (Dm) during raining days of a year and estimated based on Dm the total water volume drained from ditches in each patch (V) during annual raining days. We then demonstrated that functional hydrological connectivity, which may be represented by V, generally decreased when patch areas increased, more sensitive to changes of ditch number and length in larger peatland patches. Furthermore, we found that the total water volume drained from all ditches during annual raining days only took a very small proportion of the total volume of stream flow out of the entire watershed (0.0012%) and this nature remained similar for the past 30 years, suggesting that during annual rainfall events, water drained from connected ditches is negligible. This revealed that the role of connected artificial ditches in draining peatland water mainly takes effect during the prolonged dry season of a year in the Zoige Basin.

scholarly journals Evaluation of Noah-MP Land-Model Uncertainties over Sparsely Vegetated Sites on the Tibet Plateau

Atmosphere ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 458
Author(s):  
Guo Zhang ◽  
Fei Chen ◽  
Yueli Chen ◽  
Jianduo Li ◽  
Xindong Peng
Keyword(s):  
Heat Flux ◽  
Organic Matter ◽  
Soil Organic Matter ◽  
Tibetan Plateau ◽  
Sensible Heat Flux ◽  
Limiting Factors ◽  
Tibet Plateau ◽  
The Tibetan Plateau ◽  
Annual Total ◽  
The Impact

The water budget and energy exchange over the Tibetan Plateau (TP) region play an important role on the Asian monsoon. However, it is not well presented in the current land surface models (LSMs). In this study, uncertainties in the Noah with multiparameterization (Noah-MP) LSM are assessed through physics ensemble simulations in three sparsely vegetated sites located in the central TP. The impact of soil organic matter on energy flux and water cycles, along with the influence of uncertainties in precipitation are explored using observations at those sites during the third Tibetan Plateau Experiment from 1August2014 to31July2015. The greatest uncertainties are in the subprocesses of the canopy resistance, soil moisture limiting factors for evaporation, runoff (RNF) and ground water, and surface-layer parameterization. These uncertain subprocesses do not change across the different precipitation datasets. More precipitation can increase the annual total net radiation (Rn), latent heat flux (LH) and RNF, but decrease sensible heat flux (SH). Soil organic matter enlarges the annual total LH by ~26% but lessens the annual total Rn, SH, and RNF by ~7%, 7%, and 39%, respectively. Its effect on the LH and RNF at the Nagqu site, which has a sand soil texture type, is greater than that at the other two sites with sandy loam. This study highlights the importance of precipitation uncertainties and the effect of soil organic matter on the Noah-MP land-model simulations. It provides a guidance to improve the Noah-MP LSM further and hence the land-atmosphere interactions simulated by weather and climate models over the TP region.

scholarly journals Compound-Specific Radiocarbon Ages of Fatty Acids in Marine Sediments from the Western North Pacific

Radiocarbon ◽  
2001 ◽  
Vol 43 (2B) ◽  
pp. 949-956 ◽  
Author(s):  
Masao Uchida ◽  
Yasuyuki Shibata ◽  
Kimitaka Kawamura ◽  
Yuichiro Kumamoto ◽  
Minoru Yoneda ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Molecular Weight ◽  
Organic Matter ◽  
Marine Sediments ◽  
North Pacific ◽  
Western North Pacific ◽  
Higher Plants ◽  
Bimodal Distribution ◽  
Marine Organisms ◽  
Terrestrial Organic Matter

Compound-specific radiocarbon analysis of five fatty-acid biomarkers was conducted for marine sediments collected from the western North Pacific. The fatty acids (C12 to C34) showed a typical bimodal distribution pattern with two maxima at C16 and C26. Their carbon isotopic compositions ranged from −25.1‰ (C16) to −31.8‰ (C28), suggesting that they derived from terrestrial higher plants and marine organisms. A large variations of 14C ages were found among the fatty acids detected in the same sedimentary horizon of the core, ranging from 530 BP (C18) to 3250 BP (C28). The results of 14C analysis of fatty acids could be divided into two groups, i.e., lower molecular weight (LMW) fatty acids (C16, C18) derived from marine organisms and higher molecular weight (HMW) fatty acids (C24, C26, C28) derived from terrestrial higher plants. The HMW fatty acids showed older ages, ranging from 2550 BP (C24) to 3250 BP (C28), than LMW fatty acids (530 BP [C18] to 1,820 years BP [C16]). On the other hand, bulk-phase total organic matter (TOM) showed the age of 2260 BP that is between those two groups, suggesting that it was likely a mixture of organic matter derived from marine and terrestrial sources. The compound specific 14C ages and δ13C data of sedimentary fatty acids presented here could provide useful information to decipher the fate and transport process of terrestrial organic matter to marine sediments.

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