scholarly journals Impacts of Permafrost Degradation on Carbon Stocks and Emissions under a Warming Climate: A Review

Atmosphere ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1425
Author(s):  
Huijun Jin ◽  
Qiang Ma
Keyword(s):  
Organic Carbon ◽  
Climate Warming ◽  
Carbon Emissions ◽  
Ecosystem Model ◽  
Carbon Stocks ◽  
Carbon Pools ◽  
Permafrost Degradation ◽  
Arctic Ecosystems ◽  
Warming Climate ◽  
Permafrost Regions

A huge amount of carbon (C) is stored in permafrost regions. Climate warming and permafrost degradation induce gradual and abrupt carbon emissions into both the atmosphere and hydrosphere. In this paper, we review and synthesize recent advances in studies on carbon stocks in permafrost regions, biodegradability of permafrost organic carbon (POC), carbon emissions, and modeling/projecting permafrost carbon feedback to climate warming. The results showed that: (1) A large amount of organic carbon (1460–1600 PgC) is stored in permafrost regions, while there are large uncertainties in the estimation of carbon pools in subsea permafrost and in clathrates in terrestrial permafrost regions and offshore clathrate reservoirs; (2) many studies indicate that carbon pools in Circum-Arctic regions are on the rise despite the increasing release of POC under a warming climate, because of enhancing carbon uptake of boreal and arctic ecosystems; however, some ecosystem model studies indicate otherwise, that the permafrost carbon pool tends to decline as a result of conversion of permafrost regions from atmospheric sink to source under a warming climate; (3) multiple environmental factors affect the decomposability of POC, including ground hydrothermal regimes, carbon/nitrogen (C/N) ratio, organic carbon contents, and microbial communities, among others; and (4) however, results from modeling and projecting studies on the feedbacks of POC to climate warming indicate no conclusive or substantial acceleration of climate warming from POC emission and permafrost degradation over the 21st century. These projections may potentially underestimate the POC feedbacks to climate warming if abrupt POC emissions are not taken into account. We advise that studies on permafrost carbon feedbacks to climate warming should also focus more on the carbon feedbacks from the rapid permafrost degradation, such as thermokarst processes, gas hydrate destabilization, and wildfire-induced permafrost degradation. More attention should be paid to carbon emissions from aquatic systems because of their roles in channeling POC release and their significant methane release potentials.

scholarly journals Temperature response functions introduce high uncertainty in modelled carbon stocks in cold temperature regimes

2010 ◽  
Vol 7 (11) ◽  
pp. 3669-3684 ◽  
Author(s):  
H. Portner ◽  
H. Bugmann ◽  
A. Wolf
Keyword(s):  
Soil Carbon ◽  
Elevation Gradient ◽  
Temperature Response ◽  
Terrestrial Ecosystems ◽  
Ecosystem Model ◽  
Carbon Stocks ◽  
Carbon Pools ◽  
Parameter Estimates ◽  
Response Functions ◽  
Data Set

Abstract. Models of carbon cycling in terrestrial ecosystems contain formulations for the dependence of respiration on temperature, but the sensitivity of predicted carbon pools and fluxes to these formulations and their parameterization is not well understood. Thus, we performed an uncertainty analysis of soil organic matter decomposition with respect to its temperature dependency using the ecosystem model LPJ-GUESS. We used five temperature response functions (Exponential, Arrhenius, Lloyd-Taylor, Gaussian, Van't Hoff). We determined the parameter confidence ranges of the formulations by nonlinear regression analysis based on eight experimental datasets from Northern Hemisphere ecosystems. We sampled over the confidence ranges of the parameters and ran simulations for each pair of temperature response function and calibration site. We analyzed both the long-term and the short-term heterotrophic soil carbon dynamics over a virtual elevation gradient in southern Switzerland. The temperature relationship of Lloyd-Taylor fitted the overall data set best as the other functions either resulted in poor fits (Exponential, Arrhenius) or were not applicable for all datasets (Gaussian, Van't Hoff). There were two main sources of uncertainty for model simulations: (1) the lack of confidence in the parameter estimates of the temperature response, which increased with increasing temperature, and (2) the size of the simulated soil carbon pools, which increased with elevation, as slower turn-over times lead to higher carbon stocks and higher associated uncertainties. Our results therefore indicate that such projections are more uncertain for higher elevations and hence also higher latitudes, which are of key importance for the global terrestrial carbon budget.

scholarly journals Editorial: Organic carbon pools in permafrost regions on the Qinghai–Xizang (Tibetan) Plateau

2015 ◽  
Vol 9 (2) ◽  
pp. 479-486 ◽  
Author(s):  
C. Mu ◽  
T. Zhang ◽  
Q. Wu ◽  
X. Peng ◽  
B. Cao ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Organic Carbon ◽  
Total Organic Carbon ◽  
Carbon Storage ◽  
Carbon Pools ◽  
Permafrost Region ◽  
Arctic Regions ◽  
Deep Layers ◽  
Organic Carbon Storage ◽  
Permafrost Regions

Abstract. The current Northern Circumpolar Soil Carbon Database did not include organic carbon storage in permafrost regions on the Qinghai–Xizang (Tibetan) Plateau (QXP). In this study, we reported a new estimation of soil organic carbon (SOC) pools in the permafrost regions on the QXP up to 25 m depth using a total of 190 soil profiles. The SOC pools were estimated to be 17.3 ± 5.3 Pg for the 0–1 m depth, 10.6 ± 2.7 Pg for the 1–2 m depth, 5.1 ± 1.4 Pg for the 2–3 m depth and 127.2 ± 37.3 Pg for the layer of 3–25 m depth. The percentage of SOC storage in deep layers (3–25 m) on the QXP (80%) was higher than that (39%) in the yedoma and thermokarst deposits in arctic regions. In total, permafrost regions on the QXP contain approximately 160 ± 87 Pg SOC, of which approximately 132 ± 77 Pg (83%) stores in perennially frozen soils and deposits. Total organic carbon pools in permafrost regions on the QXP was approximately 8.7% of that in northern circumpolar permafrost region. The present study demonstrates that the total organic carbon storage is about 1832 Pg in permafrost regions on northern hemisphere.

scholarly journals Projected soil organic carbon loss in response to climate warming and soil water content in a loess watershed

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Fubo Zhao ◽  
Yiping Wu ◽  
Jinyu Hui ◽  
Bellie Sivakumar ◽  
Xianyong Meng ◽  
...  
Keyword(s):  
Climate Change ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Climate Warming ◽  
Root Zone ◽  
Warming Climate ◽  
The Future

Abstract Background Soil organic carbon (SOC) plays a crucial role in the global carbon cycle and terrestrial ecosystem functions. It is widely known that climate change and soil water content (SWC) could influence the SOC dynamics; however, there are still debates about how climate change, especially climate warming, and SWC impact SOC. We investigated the spatiotemporal changes in SOC and its responses to climate warming and root-zone SWC change using the coupled hydro-biogeochemical model (SWAT-DayCent) and climate scenarios data derived under the three Representative Concentration Pathways (RCPs2.6, 4.5, and 8.5) from five downscaled Global Climate Models (GCMs) in a typical loess watershed––the Jinghe River Basin (JRB) on the Chinese Loess Plateau. Results The air temperature would increase significantly during the future period (2017–2099), while the annual precipitation would increase by 2.0–13.1% relative to the baseline period (1976–2016), indicating a warmer and wetter future in the JRB. Driven by the precipitation variation, the root-zone SWC would also increase (by up to 27.9% relative to the baseline under RCP4.5); however, the SOC was projected to decrease significantly under the future warming climate. The combined effects of climate warming and SWC change could more reasonably explain the SOC loss, and this formed hump-shaped response surfaces between SOC loss and warming-SWC interactions under both RCP2.6 and 8.5, which can help explain diverse warming effects on SOC with changing SWC. Conclusions The study showed a significant potential carbon source under the future warmer and wetter climate in the JRB, and the SOC loss was largely controlled by future climate warming and the root-zone SWC as well. The hump-shaped responses of the SOC loss to climate warming and SWC change demonstrated that the SWC could mediate the warming effects on SOC loss, but this mediation largely depended on the SWC changing magnitude (drier or wetter soil conditions). This mediation mechanism about the effect of SWC on SOC would be valuable for enhancing soil carbon sequestration in a warming climate on the Loess Plateau.

How useful are MIR predictions of total, particulate, humus, and resistant organic carbon for examining changes in soil carbon stocks in response to different crop management? A case study

Soil Research ◽  
2013 ◽  
Vol 51 (8) ◽  
pp. 719 ◽  
Author(s):  
K. L. Page ◽  
R. C. Dalal ◽  
Y. P. Dang
Keyword(s):  
Organic Carbon ◽  
Soil Carbon ◽  
Management Practices ◽  
Crop Management ◽  
Carbon Stocks ◽  
Carbon Pools ◽  
Spectroscopic Techniques ◽  
Direct Measurements ◽  
Soil Carbon Stocks

Measures of particulate organic carbon (POC), humus organic carbon (HOC), and resistant organic carbon (ROC) (primarily char) are often used to represent the active, slow, and inert carbon pools used in soil carbon models. However, these fractions are difficult to measure directly, and mid infrared (MIR) spectroscopic techniques are increasingly being investigated to quantify these fractions and total organic carbon (TOC). This study examined the change in MIR-predicted pools of TOC, POC, HOC, and ROC in response to different crop management between two time periods (1981 and 2008) in a long-term wheat cropping trial in Queensland, Australia. The aims were (i) to assess the ability of MIR to detect changes in carbon stocks compared with direct measurements of TOC (LECO-TOC); and (ii) to assess how well the behaviour of POC, HOC, and ROC corresponded with the active, slow, and inert conceptual carbon pools. Significant declines in carbon stocks were observed over time using both LECO-TOC and MIR-predicted stocks of TOC, POC, HOC, and ROC, although MIR-TOC under-estimated loss by 27–30% compared with LECO-TOC. The decline in MIR-POC and MIR-HOC was consistent with the expected behaviour of the active and slow conceptual pools; however, the decline in ROC was not consistent with that of the inert pool. In addition, MIR measurements did not accurately detect differences in the rate of carbon loss under different crop management practices.

scholarly journals The organic carbon pool of permafrost regions on the Qinghai–Xizang (Tibetan) Plateau

2014 ◽  
Vol 8 (5) ◽  
pp. 5015-5033 ◽  
Author(s):  
C. Mu ◽  
T. Zhang ◽  
X. Peng ◽  
B. Cao ◽  
X. Zhang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Organic Carbon ◽  
Deep Layer ◽  
Carbon Pools ◽  
Soil Profiles ◽  
Permafrost Region ◽  
Frozen Soils ◽  
Organic Carbon Pool ◽  
Organic Carbon Storage ◽  
Permafrost Regions

Abstract. Presently, Northern Circumpolar Soil Carbon Database was not involved permafrost organic carbon storage on the Qinghai–Xizang (Tibetan) Plateau (QXP). Here we reported a new estimation of soil organic carbon (SOC) pools of the permafrost regions on the QXP at different layers from the top 1 to 25 m depth using a total of 706 soil profiles. The SOC pools were estimated to be 15.29 Pg for the 0–1 m, 4.84 Pg for the 1–2 m, 3.89 Pg for the 2–3 m and 43.19 Pg for the layer of 3–25 m. The percentage (64.3%) of SOC storage in deep layer (3–25 m) on the QXP was larger than that (38.8%) in the northern circumpolar permafrost region. In total, permafrost region on the QXP contains approximately 67.2 Pg SOC, of which approximately 47.08 Pg (70.1%) stores in perennially frozen soils and deposits. The present study suggested that the permafrost organic carbon pools of Northern Hemisphere should be updated from 1672 to 1739 Pg.

Status, Changes and Impacts of Permafrost on Qinghai-Tibet Plateau

2020 ◽  
Author(s):  
Lin Zhao ◽  
Guojie Hu ◽  
Defu Zou ◽  
Ren Li ◽  
Yu Sheng ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Active Layer ◽  
Climate Warming ◽  
Global Climate ◽  
Tibet Plateau ◽  
Active Layer Thickness ◽  
Permafrost Region ◽  
Permafrost Degradation ◽  
Qinghai Tibet Plateau

<p>Due to the climate warming, permafrost on the Qinghai-Tibet Plateau (QTP) was degradating in the past decades. Since its impacts on East Asian monsoon, and even on the global climate system, it is fundamental to reveal permafrost status, changes and its physical processes. Based on previous research results and new observation data, this paper reviews the characteristics of the status of permafrost on the QTP, including the active layer thickness (ALT), the spatial distribution of permafrost, permafrost temperature and thickness, as well as the ground ice and soil carbon storage in permafrost region.</p><p>The results showed that the permafrost and seasonally frozen ground area (excluding glaciers and lakes) is 1.06 million square kilometters and 1.45 million square kilometters on the QTP. The permafrost thickness varies greatly among topography, with the maximum value in mountainous areas, which could be deeper than 200 m, while the minimum value in the flat areas and mountain valleys, which could be less than 60 m. The mean value of active layer thickness is about 2.3 m. Soil temperature at 0~10 cm, 10~40 cm, 40~100 cm, 100~200 cm increased at a rate of 0.439, 0.449, 0.396, and 0.259°C/10a, respectively, from 1980 to 2015. The increasing rate of the soil temperature at the bottom of active layer was 0.486 oC/10a from 2004 to 2018.</p><p>The volume of ground ice contained in permafrost on QTP is estimated up to 1.27×10<sup>4</sup> km<sup>3</sup> (liquid water equivalent). The soil organic carbon staored in the upper 2 m of soils within the permafrost region is about 17 Pg. Most of the research results showed that the permafrost ecosystem is still a carbon sink at the present, but it might be shifted to a carbon source due to the loss of soil organic carbon along with permafrost degradation.</p><p>Overall, the plateau permafrost has undergone remarkable degradation during past decades, which are clearly proven by the increasing ALTs and ground temperature. Most of the permafrost on the QTP belongs to the unstable permafrost, meaning that permafrost over TPQ is very sensitive to climate warming. The permafrost interacts closely with water, soil, greenhouse gases emission and biosphere. Therefore, the permafrost degradation greatly affects the regional hydrology, ecology and even the global climate system.</p>

scholarly journals The Thermal and Settlement Characteristics of Crushed-Rock Structure Embankments of the Qinghai-Tibet Railway in Permafrost Regions Under Climate Warming

2021 ◽  
Vol 9 ◽  
Author(s):  
Qihang Mei ◽  
Bin Yang ◽  
Ji Chen ◽  
Jingyi Zhao ◽  
Xin Hou ◽  
...  
Keyword(s):  
Climate Warming ◽  
Cold Season ◽  
Base Layer ◽  
Crushed Rock ◽  
Permafrost Degradation ◽  
Rock Layer ◽  
Design Code ◽  
Rock Structure ◽  
The Stability ◽  
Permafrost Regions

The temperature difference at the top and bottom of the crushed-rock layer can drive the heat convection inside. Based on this mechanism, crushed-rock structures with different forms are widely used in the construction and maintenance of the Qinghai-Tibet Railway as cooling measures in permafrost regions. To explore the stability of different forms of crushed-rock structure embankments under climate warming, the temperature and deformation data of a U-shaped crushed-rock embankment (UCRE) and a crushed-rock revetment embankment (CRRE) are analysed. The variations in temperature indicate that permafrost beneath the natural sites and embankments is degrading but at different rates. The thermal regime of ground under the natural site is only affected by climate warming, while that under embankment is also affected by embankment construction and the cooling effect of the crushed-rock structure. These factors make shallow permafrost degradation beneath the embankments slower than that beneath the natural sites and deep permafrost degradation faster than that beneath the natural sites. Moreover, the convection occurring in the crushed-rock base layer during the cold season makes the degradation of permafrost beneath the UCRE slower than that in the CRRE. The faster degradation of permafrost causes the accumulated deformation of the CRRE to be far greater than that of the UCRE, which may exceed the allowable value of the design code. The analysis shows that the stability of the UCRE meets the engineering requirements and the CRRE needs to be strengthened in warm and ice-rich permafrost regions under climate warming.

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