Amazonia hosts the Earth's largest tropical forests and has been shown to be an important carbon sink over recent decades.sup.1-3. This carbon sink seems to be in decline, however, as a result of ...factors such as deforestation and climate change.sup.1-3. Here we investigate Amazonia's carbon budget and the main drivers responsible for its change into a carbon source. We performed 590 aircraft vertical profiling measurements of lower-tropospheric concentrations of carbon dioxide and carbon monoxide at four sites in Amazonia from 2010 to 2018.sup.4. We find that total carbon emissions are greater in eastern Amazonia than in the western part, mostly as a result of spatial differences in carbon-monoxide-derived fire emissions. Southeastern Amazonia, in particular, acts as a net carbon source (total carbon flux minus fire emissions) to the atmosphere. Over the past 40 years, eastern Amazonia has been subjected to more deforestation, warming and moisture stress than the western part, especially during the dry season, with the southeast experiencing the strongest trends.sup.5-9. We explore the effect of climate change and deforestation trends on carbon emissions at our study sites, and find that the intensification of the dry season and an increase in deforestation seem to promote ecosystem stress, increase in fire occurrence, and higher carbon emissions in the eastern Amazon. This is in line with recent studies that indicate an increase in tree mortality and a reduction in photosynthesis as a result of climatic changes across Amazonia.sup.1,10.
Abstract
The year 2022 saw record breaking temperatures in Europe during both summer and fall. Similar to the recent 2018 drought, close to 30% (3.0 million km
2
) of the European continent was under ...severe summer drought. In 2022, the drought was located in central and southeastern Europe, contrasting the Northern-centered 2018 drought. We show, using multiple sets of observations, a reduction of net biospheric carbon uptake in summer (56-62 TgC) over the drought area. Specific sites in France even showed a widespread summertime carbon release by forests, additional to wildfires. Partial compensation (32%) for the decreased carbon uptake due to drought was offered by a warm autumn with prolonged biospheric carbon uptake. The severity of this second drought event in 5 years suggests drought-induced reduced carbon uptake to no longer be exceptional, and important to factor into Europe’s developing plans for net-zero greenhouse gas emissions that rely on carbon uptake by forests.
Measurements of midday vertical atmospheric CO2 distributions reveal annual-mean vertical CO2 gradients that are inconsistent with atmospheric models that estimate a large transfer of terrestrial ...carbon from tropical to northern latitudes. The three models that most closely reproduce the observed annual-mean vertical CO2 gradients estimate weaker northern uptake of -1.5 petagrams of carbon per year (Pg C year(-1)) and weaker tropical emission of +0.1 Pg C year(-1) compared with previous consensus estimates of -2.4 and +1.8 Pg C year(-1), respectively. This suggests that northern terrestrial uptake of industrial CO2 emissions plays a smaller role than previously thought and that, after subtracting land-use emissions, tropical ecosystems may currently be strong sinks for CO2.
Abstract
Warming of northern high latitude regions (NHL, > 50 °N) has increased both photosynthesis and respiration which results in considerable uncertainty regarding the net carbon dioxide (CO
2
) ...balance of NHL ecosystems. Using estimates constrained from atmospheric observations from 1980 to 2017, we find that the increasing trends of net CO
2
uptake in the early-growing season are of similar magnitude across the tree cover gradient in the NHL. However, the trend of respiratory CO
2
loss during late-growing season increases significantly with increasing tree cover, offsetting a larger fraction of photosynthetic CO
2
uptake, and thus resulting in a slower rate of increasing annual net CO
2
uptake in areas with higher tree cover, especially in central and southern boreal forest regions. The magnitude of this seasonal compensation effect explains the difference in net CO
2
uptake trends along the NHL vegetation- permafrost gradient. Such seasonal compensation dynamics are not captured by dynamic global vegetation models, which simulate weaker respiration control on carbon exchange during the late-growing season, and thus calls into question projections of increasing net CO
2
uptake as high latitude ecosystems respond to warming climate conditions.
We present an estimate of net CO₂ exchange between the terrestrial biosphere and the atmosphere across North America for every week in the period 2000 through 2005. This estimate is derived from a ...set of 28,000 CO₂ mole fraction observations in the global atmosphere that are fed into a state-of-the-art data assimilation system for CO₂ called CarbonTracker. By design, the surface fluxes produced in CarbonTracker are consistent with the recent history of CO₂ in the atmosphere and provide constraints on the net carbon flux independent from national inventories derived from accounting efforts. We find the North American terrestrial biosphere to have absorbed -0.65 PgC/yr (1 petagram = 10¹⁵ g; negative signs are used for carbon sinks) averaged over the period studied, partly offsetting the estimated 1.85 PgC/yr release by fossil fuel burning and cement manufacturing. Uncertainty on this estimate is derived from a set of sensitivity experiments and places the sink within a range of -0.4 to -1.0 PgC/yr. The estimated sink is located mainly in the deciduous forests along the East Coast (32%) and the boreal coniferous forests (22%). Terrestrial uptake fell to -0.32 PgC/yr during the large-scale drought of 2002, suggesting sensitivity of the contemporary carbon sinks to climate extremes. CarbonTracker results are in excellent agreement with a wide collection of carbon inventories that form the basis of the first North American State of the Carbon Cycle Report (SOCCR), to be released in 2007. All CarbonTracker results are freely available at http://carbontracker.noaa.gov.
The uptake of carbonyl sulfide (COS) by terrestrial plants is linked to
photosynthetic uptake of CO2 as these gases partly share the same
uptake pathway. Applying COS as a photosynthesis tracer in ...models requires an
accurate representation of biosphere COS fluxes, but these models have not
been extensively evaluated against field observations of COS fluxes. In this
paper, the COS flux as simulated by the Simple Biosphere Model, version 4
(SiB4), is updated with the latest mechanistic insights and evaluated with site
observations from different biomes: one evergreen needleleaf forest, two
deciduous broadleaf forests, three grasslands, and two crop fields spread over
Europe and North America. We improved SiB4 in several ways to improve its
representation of COS. To account for the effect of atmospheric COS mole
fractions on COS biosphere uptake, we replaced the fixed atmospheric COS mole
fraction boundary condition originally used in SiB4 with spatially and
temporally varying COS mole fraction fields. Seasonal amplitudes of COS mole
fractions are ∼50–200 ppt at the investigated sites with a
minimum mole fraction in the late growing season. Incorporating seasonal
variability into the model reduces COS uptake rates in the late growing
season, allowing better agreement with observations. We also replaced the
empirical soil COS uptake model in SiB4 with a mechanistic model that
represents both uptake and production of COS in soils, which improves the
match with observations over agricultural fields and fertilized grassland
soils. The improved version of SiB4 was capable of simulating the diurnal and
seasonal variation in COS fluxes in the boreal, temperate, and Mediterranean
region. Nonetheless, the daytime vegetation COS flux is underestimated on
average by 8±27 %, albeit with large variability across sites. On a
global scale, our model modifications decreased the modeled COS terrestrial
biosphere sink from 922 Gg S yr−1 in the original SiB4 to
753 Gg S yr−1 in the updated version. The largest decrease in
fluxes was driven by lower atmospheric COS mole fractions over regions with
high productivity, which highlights the importance of accounting for
variations in atmospheric COS mole fractions. The change to a different soil
model, on the other hand, had a relatively small effect on the global
biosphere COS sink. The secondary role of the modeled soil component in the
global COS budget supports the use of COS as a global photosynthesis tracer. A
more accurate representation of COS uptake in SiB4 should allow for improved
application of atmospheric COS as a tracer of local- to global-scale
terrestrial photosynthesis.
Data assimilation systems are used increasingly to constrain the budgets of reactive and long-lived gases measured in the atmosphere. Each trace gas has its own lifetime, dominant sources and sinks, ...and observational network (from flask sampling and in situ measurements to space-based remote sensing) and therefore comes with its own optimal configuration of the data assimilation. The CarbonTracker Europe data assimilation system for CO2 estimates global carbon sources and sinks, and updates are released annually and used in carbon cycle studies. CarbonTracker Europe simulations are performed using the new modular implementation of the data assimilation system: the CarbonTracker Data Assimilation Shell (CTDAS). Here, we present and document this redesign of the data assimilation code that forms the heart of CarbonTracker, specifically meant to enable easy extension and modification of the data assimilation system. This paper also presents the setup of the latest version of CarbonTracker Europe (CTE2016), including the use of the gridded state vector, and shows the resulting carbon flux estimates. We present the distribution of the carbon sinks over the hemispheres and between the land biosphere and the oceans. We show that with equal fossil fuel emissions, 2015 has a higher atmospheric CO2 growth rate compared to 2014, due to reduced net land carbon uptake in later year. The European carbon sink is especially present in the forests, and the average net uptake over 2001–2015 was 0. 17 ± 0. 11 PgC yr−1 with reductions to zero during drought years. Finally, we also demonstrate the versatility of CTDAS by presenting an overview of the wide range of applications for which it has been used so far.
A large quantity of CH4 is emitted to the atmosphere via ventilation shafts of underground coal mines. According to the European Pollutant Release and Transfer Register (E-PRTR), hard coal mines in ...the Upper Silesia Coal Basin (USCB) are a strong contributor (447 kt CH4 in 2017) to the annual European CH4 emissions. However, atmospheric emissions of CH4 from coal mines are poorly characterized, as they are dispersed over large areas. As part of the Carbon Dioxide and CH4 Mission (CoMet) pre-campaign, a study of the USCB's regional CH4 emissions took place in August 2017. We flew a recently developed active AirCore system aboard an unmanned aerial vehicle (UAV) to obtain CH4 mole fractions downwind of a single coal mining ventilation shaft. Besides CH4, we also measured CO2, CO, atmospheric temperature, pressure, and relative humidity. Wind-speed and wind-direction measurements were made using a lightweight balloon-borne radiosonde. Fifteen UAV flights were performed flying perpendicular to the wind direction at several altitude levels, to effectively build a ‘curtain’ of CH4 mole fractions in a two-dimensional plane at a distance between 150 and 350 m downwind of a single ventilation shaft. Furthermore, we have developed an inverse Gaussian approach for quantifying CH4 emissions from a point source using the UAV-based observations, and have applied it as well as the mass balance approach to both simulated data and actual flight data to quantify CH4 emissions. The simulated data experiments revealed the importance of having multiple transects at different altitudes, appropriate vertical spacing between the individual transects, and proper distance between the center height of the plume and the center flight transect. They also showed that the inverse Gaussian approach performed better than the mass balance approach. Our estimate of the CH4 emission rates from the sampled shaft ranges from 0.5 to 14.5 kt/year using a mass balance approach, and between 1.1 and 9.0 kt/year using an inverse Gaussian method. The average difference between the mass balance and the inverse Gaussian approach was 2.3 kt/year. Based on the observed correlation between CO2 and CH4 (R-squared > 0.69), the CO2 emissions from the shaft were estimated to be between 0.3 and 9.8 kt/year. This study demonstrates that the UAV-based active AirCore system provides an effective way of quantifying coal mining shaft emissions of CH4 and CO2.
•The UAV-based active AirCore is an effective sampling tool of quantifying point source emissions of greenhouse gases.•Inverse Gaussian Approach outperforms Mass Balance Approach in estimating point source emissions.•To achieve optimal performance of the Inverse Gaussian Approach, vertical spacing of UAV-based sampling is required to be smaller than 2.5 times the vertical distribution (σz) of the plume.•Continuous and accurate wind measurements are essential to reduce the uncertainties of the quantifications.
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