scholarly journals Stalagmite carbon isotopes suggest deglacial increase in soil respiration in Western Europe driven by temperature change

2021 ◽  
Author(s):  
Franziska A. Lechleitner ◽  
Christopher C. Day ◽  
Oliver Kost ◽  
Micah Wilhelm ◽  
Negar Haghipour ◽  
...  
Keyword(s):  
Soil Respiration ◽  
Western Europe ◽  
Terrestrial Ecosystem ◽  
Atmospheric Conditions ◽  
Last Deglaciation ◽  
Northern Spain ◽  
Local Soil ◽  
Response To Temperature ◽  
Climatic And Environmental Change ◽  
Global Carbon

Abstract. The temperate region of Western Europe underwent dramatic climatic and environmental change during the last deglaciation. Much of what is known about the terrestrial ecosystem response to deglacial warming stems from pollen preserved in sediment sequences, providing information on vegetation composition. Other ecosystem processes, such as soil respiration, remain poorly constrained over past climatic transitions, but are critical for understanding the global carbon cycle and its response to ongoing anthropogenic warming. Here we show that speleothem carbon isotope (δ13Cspel) records may retain information on local soil respiration, and allow its reconstruction over time. While this notion has been proposed in the past, our study is the first to rigorously test it, using a combination of multi-proxy geochemical analysis (δ13C, Ca isotopes, and radiocarbon) on three speleothems from Northern Spain, and quantitative forward modelling of processes in soil, karst, and cave. Our study is the first to quantify and remove the effects of prior calcite precipitation (PCP, using Ca isotopes) and bedrock dissolution (using the radiocarbon reservoir effect) from the δ13Cspel signal to derive changes in respired δ13C. Coupling of soil gas pCO2 and δ13C via a mixing line describing diffusive gas transport between an atmospheric and a respired end member allows modelling of changes in soil respiration in response to temperature. Using this coupling and a range of other parameters describing carbonate dissolution and cave atmospheric conditions, we generate large simulation ensembles from which the results most closely matching the measured speleothem data are selected. Our results robustly show that an increase in soil pCO2 (and thus respiration) is needed to explain the observed deglacial trend in δ13Cspel. However, the Q10 (temperature sensitivity) derived from the model results is higher than current measurements, suggesting that part of the signal may be related to a change in the composition of the soil respired δ13C, likely from changing substrate through increasing contribution from vegetation biomass with the onset of the Holocene.

scholarly journals Stalagmite carbon isotopes suggest deglacial increase in soil respiration in western Europe driven by temperature change

2021 ◽  
Vol 17 (5) ◽  
pp. 1903-1918
Author(s):  
Franziska A. Lechleitner ◽  
Christopher C. Day ◽  
Oliver Kost ◽  
Micah Wilhelm ◽  
Negar Haghipour ◽  
...  
Keyword(s):  
Soil Respiration ◽  
Western Europe ◽  
Terrestrial Ecosystem ◽  
Soil Gas ◽  
Atmospheric Conditions ◽  
Last Deglaciation ◽  
Calcite Precipitation ◽  
Response To Temperature ◽  
Climatic And Environmental Change ◽  
Global Carbon

Abstract. The temperate region of western Europe underwent significant climatic and environmental change during the last deglaciation. Much of what is known about the terrestrial ecosystem response to deglacial warming stems from pollen preserved in sediment sequences, providing information on vegetation composition. Other ecosystem processes, such as soil respiration, remain poorly constrained over past climatic transitions but are critical for understanding the global carbon cycle and its response to ongoing anthropogenic warming. Here we show that speleothem carbon isotope (δ13Cspel) records may retain information on soil respiration and allow its reconstruction over time. While this notion has been proposed in the past, our study is the first to rigorously test it, using a combination of multi-proxy geochemical analysis (δ13C, Ca isotopes, and radiocarbon) on three speleothems from the NW Iberian Peninsula and quantitative forward modelling of processes in soil, karst, and cave. Our study is the first to quantify and remove the effects of prior calcite precipitation (PCP, using Ca isotopes) and bedrock dissolution (using the radiocarbon reservoir effect) from the δ13Cspel signal to derive changes in respired δ13C. The coupling of soil gas pCO2 and δ13C via a mixing line describing diffusive gas transport between an atmospheric and a respired end-member allows the modelling of changes in soil respiration in response to temperature. Using this coupling and a range of other parameters describing carbonate dissolution and cave atmospheric conditions, we generate large simulation ensembles from which the results most closely matching the measured speleothem data are selected. Our results robustly show that an increase in soil gas pCO2 (and thus respiration) is needed to explain the observed deglacial trend in δ13Cspel. However, the Q10 (temperature sensitivity) derived from the model results is higher than current measurements, suggesting that part of the signal may be related to a change in the composition of the soil respired δ13C, likely from changing substrate through increasing contribution from vegetation biomass with the onset of the Holocene.

A coupled multi-proxy and process modelling approach for extraction of quantitative terrestrial ecosystem information from speleothems

2021 ◽  
Author(s):  
Franziska Lechleitner ◽  
Christopher C. Day ◽  
Oliver Kost ◽  
Micah Wilhelm ◽  
Negar Haghipour ◽  
...  
Keyword(s):  
Climate Change ◽  
Soil Respiration ◽  
Western Europe ◽  
Global Climate ◽  
Terrestrial Ecosystem ◽  
Terrestrial Ecosystems ◽  
Clear Correlation ◽  
Northern Spain ◽  
Regional Temperature ◽  
Global Carbon

<p>Terrestrial ecosystems are intimately linked with the global climate system, but their response to ongoing and future anthropogenic climate change remains poorly understood. Reconstructing the response of terrestrial ecosystem processes over past periods of rapid and substantial climate change can serve as a tool to better constrain the sensitivity in the ecosystem-climate response.</p><p>In this talk, we will present a new reconstruction of soil respiration in the temperate region of Western Europe based on speleothem carbon isotopes (δ<sup>13</sup>C). Soil respiration remains poorly constrained over past climatic transitions, but is critical for understanding the global carbon cycle and its response to ongoing anthropogenic warming. Our study builds upon two decades of speleothem research in Western Europe, which has shown clear correlation between δ<sup>13</sup>C and regional temperature reconstructions during the last glacial and the deglaciation, with exceptional regional coherency in timing, amplitude, and absolute δ<sup>13</sup>C variation. By combining innovative multi-proxy geochemical analysis (δ<sup>13</sup>C, Ca isotopes, and radiocarbon) on three speleothems from Northern Spain, and quantitative forward modelling of processes in soil, karst, and cave, we show how deglacial variability in speleothem δ<sup>13</sup>C is best explained by increasing soil respiration. Our study is the first to quantify and remove the effects of prior calcite precipitation (PCP, using Ca isotopes) and bedrock dissolution (open vs closed system, using the radiocarbon reservoir effect) from the speleothem δ<sup>13</sup>C signal to derive changes in respired δ<sup>13</sup>C over time. Our approach allows us to estimate the temperature sensitivity of soil respiration (Q<sub>10</sub>), which is higher than current measurements, suggesting that part of the speleothem signal may be related to a change in the composition of the soil respired δ<sup>13</sup>C. This is likely related to changing substrate through increasing contribution from vegetation biomass with the onset of the Holocene.</p><p>These results highlight the exciting possibilities speleothems offer as a coupled archive for quantitative proxy-based reconstructions of climate and ecosystem conditions.</p>

Understanding the deglacial relationship between carbon isotopes and temperature in stalagmites from Western Europe

2020 ◽  
Author(s):  
Franziska A. Lechleitner ◽  
Christopher C. Day ◽  
Micah Wilhelm ◽  
Negar Haghipour ◽  
Oliver Kost ◽  
...  
Keyword(s):  
Western Europe ◽  
Forward Modelling ◽  
Last Deglaciation ◽  
Northern Spain ◽  
Time Period ◽  
Carbonate Host Rock ◽  
The Last Deglaciation ◽  
Temperature Records ◽  
Soil Activity ◽  
Karst Processes

<p>The last deglaciation was a period of rapid and profound climatic change in Western Europe. Speleothem carbon isotope (δ<sup>13</sup>C) records from mid-latitude Western Europe have consistently shown large and reproducible excursions over this time period, strikingly similar to available temperature reconstructions from other archives. The mechanism behind the temperature sensitivity of speleothem δ<sup>13</sup>C, however, remains poorly constrained, due to the complex interplay of multiple processes affecting this proxy.</p><p>Here we use a multi-proxy approach and forward modelling of karst processes to investigate what drives the response of speleothem δ<sup>13</sup>C to the last deglaciation in Western Europe. We present new proxy data (<sup>14</sup>C and δ<sup>44</sup>Ca) from speleothem Candela from El Pindal Cave, northern Spain, which covers the period from the Last Glacial Maximum (25 ka BP) to the Early Holocene (8 ka BP). Previously published stable isotope data (Moreno et al., 2010) revealed a pronounced decrease in δ<sup>13</sup>C over the deglaciation (~8‰ VPDB) which closely tracks regional temperature records from the Iberian Margin. We make use of the different sensitivities of ancillary proxies (<sup>14</sup>C, Mg/Ca, and δ<sup>44</sup>Ca) to processes in soil and karst to quantify their relative importance on the δ<sup>13</sup>C shift. For this, we use the forward modelling software CaveCalc (Owen et al., 2018) to generate a large ensemble of possible solutions, from which the ones closest matching the data are chosen and evaluated.</p><p>Our preliminary results suggest that in-cave and karst processes (carbonate host rock dissolution and reprecipitation) cannot explain the full amplitude of the δ<sup>13</sup>C shift over the deglaciation, and that changes in soil δ<sup>13</sup>C are to some extent translated to the speleothem carbonate δ<sup>13</sup>C. The possibility of quantitatively disentangling processes in the soil from other karst processes could allow the reconstruction of past soil activity from speleothems.</p><p> </p><p>References:</p><p>Moreno, A., Stoll, H., Jiménez-Sánchez, M., Cacho, I., Valero-Garcés, B., Ito, E., Edwards, R.L., 2010. A speleothem record of glacial (25-11.6 kyr BP) rapid climatic changes from northern Iberian Peninsula. Glob. Planet. Change 71, 218–231. doi:10.1016/j.gloplacha.2009.10.002</p><p>Owen, R.A., Day, C.C., Henderson, G.M., 2018. CaveCalc: A new model for speleothem chemistry & isotopes. Comput. Geosci. doi:10.1016/J.CAGEO.2018.06.011</p>

scholarly journals Estimation of Incident Photosynthetically Active Radiation from GOES Visible Imagery

2008 ◽  
Vol 47 (3) ◽  
pp. 853-868 ◽  
Author(s):  
Tao Zheng ◽  
Shunlin Liang ◽  
Kaicun Wang
Keyword(s):  
Photosynthetically Active Radiation ◽  
Terrestrial Ecosystem ◽  
New Method ◽  
High Temporal Resolution ◽  
Atmospheric Conditions ◽  
Ecosystem Models ◽  
Surface Conditions ◽  
Active Radiation ◽  
Ground Measurement ◽  
Visible Imagery

Abstract Incident photosynthetically active radiation (PAR) is an important parameter for terrestrial ecosystem models. Because of its high temporal resolution, the Geostationary Operational Environmental Satellite (GOES) observations are very suited to catch the diurnal variation of PAR. In this paper, a new method is developed to derive PAR using GOES data. What makes this new method distinct from the existing method is that it does not need external knowledge of atmospheric conditions. The new method retrieves both atmospheric and surface conditions using only at-sensor radiance through interpolation of time series of observations. Validations against ground measurement are carried out at four “FLUXNET” sites. The values of RMSE of estimated and ground-measured instantaneous PAR at the four sites are 130.71, 131.44, 141.16, and 190.22 μmol m−2 s−1, respectively. At the four validation sites, the RMSE as the percentage of estimated mean PAR value are 9.52%, 13.01%, 13.92%, and 24.09%, respectively; the biases are −101.54, 16.56, 11.09, and 53.64 μmol m−2 s−1, respectively. The independence of external atmospheric information enables this method to be applicable to many situations in which external atmospheric information is not available. In addition, topographic impacts on surface PAR are examined at the 1-km resolution at which PAR is retrieved using the GOES visible band data.

scholarly journals A global CO<sub>2</sub> flux dataset (2015–2019) inferred from OCO-2 retrievals using the Tan-Tracker inversion system

2021 ◽  
Author(s):  
Zhe Jin ◽  
Xiangjun Tian ◽  
Rui Han ◽  
Yu Fu ◽  
Xin Li ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Carbon Cycle ◽  
Carbon Flux ◽  
Carbon Budget ◽  
Terrestrial Ecosystem ◽  
Carbon Fluxes ◽  
Global Carbon Cycle ◽  
Ocean Carbon ◽  
Global Carbon ◽  
Regional Fluxes

Abstract. Accurate assessment of the various sources and sinks of carbon dioxide (CO2), especially terrestrial ecosystem and ocean fluxes with high uncertainties, is important for understanding of the global carbon cycle, supporting the formulation of climate policies, and projecting future climate change. Satellite retrievals of the column-averaged dry air mole fractions of CO2 (XCO2) are being widely used to improve carbon flux estimation due to their broad spatial coverage. However, there is no consensus on the robust estimates of regional fluxes. In this study, we present a global and regional resolved terrestrial ecosystem carbon flux (NEE) and ocean carbon flux dataset for 2015–2019. The dataset was generated using the Tan-Tracker inversion system by assimilating Observing Carbon Observatory 2 (OCO-2) column CO2 retrievals. The posterior NEE and ocean carbon fluxes were comprehensively validated by comparing posterior simulated CO2 concentrations with OCO-2 independent retrievals and Total Carbon Column Observing Network (TCCON) measurements. The validation showed that posterior carbon fluxes significantly improved the modelling of atmospheric CO2 concentrations, with global mean biases of 0.33 ppm against OCO-2 retrievals and 0.12 ppm against TCCON measurements. We described the characteristics of the dataset at global, regional, and Tibetan Plateau scales in terms of the carbon budget, annual and seasonal variations, and spatial distribution. The posterior 5-year annual mean global atmospheric CO2 growth rate was 5.35 PgC yr−1, which was within the uncertainty of the Global Carbon Budget 2020 estimate (5.49 PgC yr−1). The posterior annual mean NEE and ocean carbon fluxes were −4.07 and −3.33 PgC yr−1, respectively. Regional fluxes were analysed based on TransCom partitioning. All 11 land regions acted as carbon sinks, except for Tropical South America, which was almost neutral. The strongest carbon sinks were located in Boreal Asia, followed by Temperate Asia and North Africa. The entire Tibetan Plateau ecosystem was estimated as a carbon sink, taking up −49.52 TgC yr−1 on average, with the strongest sink occurring in eastern alpine meadows. These results indicate that our dataset captures surface carbon fluxes well and provides insight into the global carbon cycle. The dataset can be accessed at https://doi.org/10.11888/Meteoro.tpdc.271317 (Jin et al., 2021).

scholarly journals Carbon Stock Variation along altitudinal gradient of Wacho Forest in Hawa Galan District, Kellem Wollega Zone, Oromia Region, Ethiopia

2020 ◽  
Author(s):  
Gezahegn Gashu ◽  
Gebre Gidey ◽  
Sime Deressa ◽  
Zame Fekansa ◽  
Halid Awoke
Keyword(s):  
Forest Ecosystem ◽  
Carbon Stock ◽  
Terrestrial Ecosystem ◽  
The Third ◽  
Natural Break ◽  
Below Ground ◽  
Carbon Reservoir ◽  
Potential Strategy ◽  
Atmospheric Concentrations ◽  
Global Carbon

Abstract Background Forest ecosystem plays a crucial role in the global carbon cycle; as such, mitigating high atmospheric concentrations of carbon dioxide and other greenhouse gases by naturally taking carbon from the atmosphere through photosynthesis. Verification and accounting of carbon stock in forest ecosystem have been renowned as a potential strategy to reduce and stabilize atmospheric concentrations of greenhouse gas. Forest sequesters and store more carbon than any other terrestrial ecosystem and it is an important natural break on climate change. It acts as a carbon reservoir by storing large amount of carbon in trees, undergrowth vegetation, forest floor and soil. Result The mean carbon stock of each carbon pool was changed along altitudinal class of the study area. The largest mean above and below ground carbon stock was found in the second altitudinal class(1560.01-1643m) followed by first altitudinal class(1435-1560m) and the third altitudinal class (1643.01-1704m) of the study area. The largest mean dead tree and dead wood carbon stock was also stored in the first altitudinal class followed by the third and the second altitudinal class of the study area. The largest mean litter carbon stock was found in the first altitudinal class followed by the second and the third altitudinal class of the study area. The largest mean soil organic carbon was found in the third altitudinal class followed by the second and the first altitudinal class of the study area. Conclusions The carbon stock variation along altitudinal gradients indicated that, altitude had no a statistically significant effect on any of the carbon pools except litter carbon of the study area at 95% of confidence interval.

scholarly journals Deglacial climate and ice sheet evolution of the Ross Embayment, Antarctica

2021 ◽  
Author(s):  
◽  
Daniel P. Lowry
Keyword(s):  
Spatial Pattern ◽  
Climate Models ◽  
Ice Sheet ◽  
Model Parameters ◽  
Atmospheric Conditions ◽  
Last Deglaciation ◽  
Proxy Records ◽  
External Forcings ◽  
Wide Range ◽  
Grounding Line

<p>Reconstructing past grounding-line evolution can help inform future sea level projections by constraining marine ice sheet sensitivities to changes in climate. The Ross Embayment, the largest sector of Antarctica, experienced substantial grounding-line retreat since the Last Glacial Maximum. However, different interpretations for the timing and spatial pattern of deglacial grounding-line retreat in this region persist, suggesting either very high or low sensitivity to external forcings. Complicating matters is the sparse paleoclimate record, which is limited spatially and temporally. In this thesis, I address these issues by analysing the output of two transient climate simulations in relation to Antarctic ice core and marine sediment records, and performing and analysing the largest ensemble to date of regional ice sheet model simulations of the last deglaciation in the Ross Sea. The climate models and paleoclimate proxy records exhibit key differences in the timing, magnitude and duration of millennial-scale climate change events through the deglacial period. Using this diverse set of deglacial climate trajectories as ocean and atmosphere forcings, the ice sheet model ensemble produces a wide range of ice sheet responses, supporting the view that external forcings are the main drivers of past grounding-line retreat in the region. The simulations demonstrate that atmospheric conditions early in the deglacial period can enhance or diminish ice sheet sensitivity to rising ocean temperatures, thereby controlling the initial timing and spatial pattern of grounding-line retreat. Through the Holocene, grounding-line position is more sensitive to sub-shelf melt rates as the ocean cavity below the ice shelf expands. Model parameters that control the physical properties of the bed, deformation of the continental shelf, and rheological properties of the ice strongly influence the sensitivity of ice sheets to external forcing. Basin-wide differences in these forcings, driven by oceanic and atmospheric circulation, and spatial heterogeneity of bed properties likely contribute to the asynchronous pattern of retreat in the eastern and western parts of the embayment, as indicated by marine and terrestrial proxy records.</p>

scholarly journals A Global Carbon Assimilation System using a modified EnKF assimilation method

2014 ◽  
Vol 7 (5) ◽  
pp. 6519-6547
Author(s):  
S. Zhang ◽  
X. Zheng ◽  
Z. Chen ◽  
B. Dan ◽  
J. M. Chen ◽  
...  
Keyword(s):  
Kalman Filter ◽  
Ensemble Kalman Filter ◽  
Carbon Assimilation ◽  
Terrestrial Ecosystem ◽  
Carbon Fluxes ◽  
Ecosystem Model ◽  
Atmospheric Co2 ◽  
Forecast Errors ◽  
Global Carbon ◽  
Assimilation System

Abstract. A Global Carbon Assimilation System based on Ensemble Kalman filter (GCAS-EK) is developed for assimilating atmospheric CO2 abundance data into an ecosystem model to simultaneously estimate the surface carbon fluxes and atmospheric CO2 distribution. This assimilation approach is based on the ensemble Kalman filter (EnKF), but with several new developments, including using analysis states to iteratively estimate ensemble forecast errors, and a maximum likelihood estimation of the inflation factors of the forecast and observation errors. The proposed assimilation approach is tested in observing system simulation experiments and then used to estimate the terrestrial ecosystem carbon fluxes and atmospheric CO2 distributions from 2002 to 2008. The results showed that this assimilation approach can effectively reduce the biases and uncertainties of the carbon fluxes simulated by the ecosystem model.

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