Radiocarbon in the Land and Ocean Components of the Community Earth System Model

Large amounts of the carbon-isotope 14C, entering Earth's carbon cycle, were produced in the atmosphere by atomic bomb tests in the 1950s and 1960s. Here, we forced the ocean and land components of the Community Earth System Model with atmospheric 14CO2 over the historical period to constrain overturning time scales and fluxes. The uptake of bomb 14C by the land model is lower than observation-based estimates. This mismatch is likely linked to too-low 14C uptake by vegetation as the model overestimates 14C/C ratios of modern soils. This suggests model biases in forest productivity or wood carbon allocation and turnover, and, in turn, a bias in the forest sink of anthropogenic carbon. The ocean model matches the observation-based global bomb 14C inventories when applying the quadratic relationship between gas transfer piston velocity and wind speed of Wanninkhof (2014), https://doi.org/10.4319/lom.2014.12.351 and the wind products from Large and Yeager or the Japanese Reanalysis Project. Simulated natural radiocarbon ages in the deep ocean are many centuries older than data-based estimates, indicating too slow deep ocean ventilation. The sluggish circulation causes large biases in biogeochemical tracers and implies a delayed deep ocean uptake of heat and carbon in global warming projections. Our study suggests that 14C observations are key to constrain carbon fluxes and transport timescales for improved representations of land and ocean biogeochemical cycles and Earth system model projections

Effects of short-term variability of meteorological variables on soil temperature in permafrost regions

Effects of the short-term temporal variability of meteorological variables on soil temperature in northern high-latitude regions have been investigated. For this, a process-oriented land surface model has been driven using an artificially manipulated climate dataset. Short-term climate variability mainly impacts snow depth, and the thermal diffusivity of lichens and bryophytes. These impacts of climate variability on insulating surface layers together substantially alter the heat exchange between atmosphere and soil. As a result, soil temperature is 0.1 to 0.8 ∘C higher when climate variability is reduced. Earth system models project warming of the Arctic region but also increasing variability of meteorological variables and more often extreme meteorological events. Therefore, our results show that projected future increases in permafrost temperature and active-layer thickness in response to climate change will be lower (i) when taking into account future changes in short-term variability of meteorological variables and (ii) when representing dynamic snow and lichen and bryophyte functions in land surface models

Ground subsidence effects on simulating dynamic high-latitude surface inundation under permafrost thaw using CLM5

Simulating surface inundation is particularly challenging for the high-latitude permafrost regions. Ice-rich permafrost thaw can create expanding thermokarst lakes as well as shrinking large wetlands. Such processes can have major biogeochemical implications and feedbacks to the climate system by altering the pathways and rates of permafrost carbon release. However, the processes associated with it havenot yet been properly represented in Earth system models. We show a new model parameterization that allows direct representation of surface water dynamics in CLM (Community Land Model), the land surface model of several Earth System Models. Specifically, we coupled permafrost-thaw-induced ground subsidence and surface microtopography distribution to represent surface water dynamics in the high latitudes. Our results show increased surface water fractions around western Siberian plains and northeastern territories of Canada. Additionally, localized drainage events correspond well to severe ground subsidence events. Our parameterization is one of the first steps towards a process-oriented repre-sentation of surface hydrology, which is crucial to assess the biogeochemical feedbacks between land and the atmosphere under changing climat

Quantifying uncertainties of permafrost carbon–climate feedbacks

The land surface models JULES (Joint UK Land Environment Simulator, two versions) and ORCHIDEE-MICT (Organizing Carbon and Hydrology in Dynamic Ecosystems), each with a revised representation of permafrost carbon, were coupled to the Integrated Model Of Global Effects of climatic aNomalies (IMOGEN) intermediate-complexity climate and ocean carbon uptake model. IMOGEN calculates atmospheric carbon dioxide (CO2) and local monthly surface climate for a given emission scenario with the land–atmosphere CO2 flux exchange from either JULES or ORCHIDEE-MICT. These simulations include feedbacks associated with permafrost carbon changes in a warming world. Both IMOGEN–JULES and IMOGEN–ORCHIDEE-MICT were forced by historical and three alternative future-CO2-emission scenarios. Those simulations were performed for different climate sensitivities and regional climate change patterns based on 22 different Earth system models (ESMs) used for CMIP3 (phase 3 of the Coupled Model Intercomparison Project), allowing us to explore climate uncertainties in the context of permafrost carbon–climate feedbacks. Three future emission scenarios consistent with three representative concentration pathways were used: RCP2.6, RCP4.5 and RCP8.5. Paired simulations with and without frozen carbon processes were required to quantify the impact of the permafrost carbon feedback on climate change. The additional warming from the permafrost carbon feedback is between 0.2 and 12 % of the change in the global mean temperature (ΔT) by the year 2100 and 0.5 and 17 % of ΔT by 2300, with these ranges reflecting differences in land surface models, climate models and emissions pathway. As a percentage of ΔT, the permafrost carbon feedback has a greater impact on the low-emissions scenario (RCP2.6) than on the higher-emissions scenarios, suggesting that permafrost carbon should be taken into account when evaluating scenarios of heavy mitigation and stabilization. Structural differences between the land surface models (particularly the representation of the soil carbon decomposition) are found to be a larger source of uncertainties than differences in the climate response. Inertia in the permafrost carbon system means that the permafrost carbon response depends on the temporal trajectory of warming as well as the absolute amount of warming. We propose a new policy-relevant metric – the frozen carbon residence time (FCRt) in years – that can be derived from these complex land surface models and used to quantify the permafrost carbon response given any pathway of global temperature change

The response of terrestrial ecosystem carbon cycling under different aerosol-based radiation management geoengineering

Geoengineering has been discussed as a potential option to offset the global impacts of anthropogenic climate change and at the same time reach the global temperature targets of the Paris Agreement. Before any implementation of geoengineering, however, the complex natural responses and consequences of such methods should be fully understood to avoid any unexpected and potentially degrading impacts. Here we assess the changes in ecosystem carbon exchange and storage among different terrestrial biomes under three aerosol-based radiation management methods with the baseline of RCP8.5 using an Earth system model (NorESM1-ME). All three methods used in this study (stratospheric aerosol injection, marine sky brightening, cirrus cloud thinning) target the global mean radiation balance at the top of the atmosphere to reach that of the RCP4.5 scenario. The three radiation management (RM) methods investigated in this study show vastly different precipitation patterns, especially in the tropical forest biome. Precipitation differences from the three RM methods result in large variability in global vegetation carbon uptake and storage. Our findings show that there are unforeseen regional consequences under geoengineering, and these consequences should be taken into account in future climate policies as they have a substantial impact on terrestrial ecosystems. Although changes in temperature and precipitation play a large role in vegetation carbon uptake and storage, our results show that CO2 fertilization also plays a considerable role. We find that the effects of geoengineering on vegetation carbon storage are much smaller than the effects of mitigation under the RCP4.5 scenario (e.g., afforestation in the tropics). Our results emphasize the importance of considering multiple combined effects and responses of land biomes while achieving the global temperature targets of the Paris Agreement.publishedVersio

The Response of Permafrost and High‐Latitude Ecosystems under Large‐Scale Stratospheric Aerosol Injection and its Termination

Climate engineering arises as one of the potential methods that could contribute to meeting the1.5 °C global warming target agreed under the Paris Agreement. We examine how permafrost and high‐latitude vegetation respond to the large‐scale implementation of climate engineering. Specifically, we explore the impacts of applying the solar radiation management method of stratospheric aerosol injections(SAI) on permafrost temperature and the global extent of near‐surface permafrost area. We compare the RCP8.5 and RCP4.5 scenarios to several SAI deployment scenarios using the Norwegian Earth System Model (CE1 = moderate SAI scenario to bring down the global mean warming in RCP8.5 to the RCP4.5 level,CE2 = aggresive SAI scenario to maintain the global mean temperature toward the preindustrial level). We show that large‐scale application of SAI may help slow down the current rate of permafrost degradation for awide range of emission scenarios. Between the RCP4.5 and CE1 simulations, the differences in the permafrost degradation may be attributed to the spatial variations in surface air temperature, rainfall, andsnowfall, which lead to the differences in the timing of permafrost degradation up to 40 years. Although atmospheric temperatures in CE1 and RCP4.5 simulations are similar, net primary production is higher in CE1 due to CO₂ fertilization. Our investigation of permafrost extent under large‐scale SAI application scenarios suggests that circum‐Arctic permafrost area and extent is rather sensitive to temperature changescreated under such SAI application. Our results highlight the importance of investigating the regional effectsof climate engineering, particularly in high‐latitude ecosystems

?-amylase monitoring by a novel amperometric biosensor based on Au electrode: Its optimization, characterization, and application

PubMed ID: 21838534A low-cost and sensitive amperometric biosensor was developed for the determination of ?-amylase activity. The biosensor was constructed by immobilizing glucose oxidasegelatin via glutaraldehyde on the Au electrode surface. Measurements were carried out chronoamperometrically at -0.7 V. Several parameters such as glucose oxidase activity, gelatin amount, and glutaraldehyde percentage for cross-linking were optimized. Optimum pH, optimum temperature, repeatability, and storage stabilities of the biosensor were identified. Under the optimum experimental conditions, a linear calibration curve was obtained for ?-amylase between 0.819 and 13.110 U/ml. Sample analyses were carried out by detecting ?-amylase activities in bakers yeast samples. © 2012 Informa Healthcare USA, Inc

alpha-Amylase Monitoring by a Novel Amperometric Biosensor Based on Au Electrode: Its Optimization, Characterization, and Application

WOS: 000299696500012PubMed ID: 21838534A low-cost and sensitive amperometric biosensor was developed for the determination of alpha-amylase activity. The biosensor was constructed by immobilizing glucose oxidase-gelatin via glutaraldehyde on the Au electrode surface. Measurements were carried out chronoamperometrically at -0.7 V. Several parameters such as glucose oxidase activity, gelatin amount, and glutaraldehyde percentage for cross-linking were optimized. Optimum pH, optimum temperature, repeatability, and storage stabilities of the biosensor were identified. Under the optimum experimental conditions, a linear calibration curve was obtained for alpha-amylase between 0.819 and 13.110 U/ml. Sample analyses were carried out by detecting alpha-amylase activities in baker's yeast samples

Path-dependent reductions in CO₂ emission budgets caused by permafrost carbon release

Emission budgets are defined as the cumulative amount of anthropogenic CO₂ emission compatible with a global temperature-change target. The simplicity of the concept has made it attractive to policy-makers, yet it relies on a linear approximation of the global carbon-climate system's response to anthropogenic CO2 emissions. Here we investigate how emission budgets are impacted by the inclusion of CO₂ and CH₄ emissions caused by permafrost thaw, a non-linear and tipping process of the Earth system. We use the compact Earth system model OSCAR v2.2.1, in which parameterizations of permafrost thaw, soil organic matter decomposition and CO₂ and CH₄ emission were introduced based on four complex land surface models that specifically represent high-latitude processes. We found that permafrost carbon release makes emission budgets path dependent (that is, budgets also depend on the pathway followed to reach the target). The median remaining budget for the 2 °C target reduces by 8% (1-25%) if the target is avoided and net negative emissions prove feasible, by 13% (2-34%) if they do not prove feasible, by 16% (3-44%) if the target is overshot by 0.5 °C and by 25% (5-63%) if it is overshot by 1 °C. (Uncertainties are the minimum-to-maximum range across the permafrost models and scenarios.) For the 1.5 °C target, reductions in the median remaining budget range from ~10% to more than 100%. We conclude that the world is closer to exceeding the budget for the long-term target of the Paris Climate Agreement than previously thought