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Investigating the sensitivity of soil heterotrophic respiration to recent snow cover changes in Alaska using a satellite-based permafrost carbon model

We developed a 1 km satellite-data-driven permafrost carbon model to evaluate soil respiration sensitivity to recent snow cover changes in Alaska. Results show earlier snowmelt enhances growing-season soil respiration and reduces annual carbon uptake, while early cold-season soil respiration is linked to the number of snow-free days after the land surface freezes. Our results also show nonnegligible influences of subgrid variability in surface conditions on model-simulated CO ₂ seasonal cycles.

Reviews and syntheses: The mechanisms underlying carbon storage in soil

The 4 per 1000 initiative aims to restore carbon storage in soils to both mitigate climate change and contribute to food security. The French National Institute for Agricultural Research conducted a study to determine the carbon storage potential in French soils and associated costs. This paper is a part of that study. It reviews recent advances concerning the mechanisms that controls C stabilization in soils. Synthetic figures integrating new concepts should be of pedagogical interest.

Factors controlling plankton community production, export flux, and particulate matter stoichiometry in the coastal upwelling system off Peru

The eastern boundary upwelling system off Peru is among Earth’s most productive ocean ecosystems, but the factors that control its functioning are poorly constrained. Here we used mesocosms, moored ~ 6 km offshore Peru, to investigate how processes in plankton communities drive key biogeochemical processes. We show that nutrient and light co-limitation keep productivity and export at a remarkably constant level while stoichiometry changes strongly with shifts in plankton community structure.

Increase in ocean acidity variability and extremes under increasing atmospheric CO2

Ensemble simulations of an Earth system model reveal that ocean acidity extremes have increased in the past few decades and are projected to increase further in terms of frequency, intensity, duration, and volume extent. The increase is not only caused by the long-term ocean acidification due to the uptake of anthropogenic CO ₂ , but also due to changes in short-term variability. The increase in ocean acidity extremes may enhance the risk of detrimental impacts on marine organisms.

Rainfall intensification increases the contribution of rewetting pulses tosoil heterotrophic respiration

Carbon dioxide is produced by soil microbes through respiration, which is particularly fast when soils are moistened by rain. Will respiration increase with future more intense rains and longer dry spells? With a mathematical model, we show that wetter conditions increase respiration. In contrast, if rainfall totals stay the same, but rain comes all at once after long dry spells, the average respiration will not change, but the contribution of the respiration bursts after rain will increase.

CloudRoots: integration of advanced instrumental techniques and processmodelling of sub-hourly and sub-kilometre land–atmosphere interactions

The CloudRoots field experiment has obtained an open comprehensive observational data set that includes soil, plant, and atmospheric variables to investigate the interactions between a heterogeneous land surface and its overlying atmospheric boundary layer, including the rapid perturbations of clouds in evapotranspiration. Our findings demonstrate that in order to understand and represent diurnal variability, we need to measure and model processes from the leaf to the landscape scales.

The recent state and variability of the carbonate system of the CanadianArctic Archipelago and adjacent basins in the context of ocean acidification

Ocean acidification is the process by which the oceans are changing due to carbon dioxide emissions from human activities. Studying this process in the Arctic Ocean is essential as this ocean and its ecosystems are more vulnerable to the effects of acidification. Water chemistry measurements made in recent years show that waters in and around the Canadian Arctic Archipelago are considerably affected by this process and show dynamic conditions that might have an impact on local marine organisms.

On giant shoulders: how a seamount affects the microbial communitycomposition of seawater and sponges

Seamounts are globally abundant submarine structures that offer great potential to study the impacts and interactions of environmental gradients at a single geographic location. In an exemplary way, we describe potential mechanisms by which a seamount can affect the structure of pelagic and benthic (sponge-)associated microbial communities. We conclude that the geology, physical oceanography, biogeochemistry, and microbiology of seamounts are even more closely linked than currently appreciated.

N2O changes from the Last Glacial Maximum to the preindustrial – Part 2: terrestrial N2O emissions and carbon–nitrogen cycle interactions

Results of the first globally resolved simulations of terrestrial carbon and nitrogen (N) cycling and N ₂ O emissions over the past 21 000 years are compared with reconstructed N ₂ O emissions. Modelled and reconstructed emissions increased strongly during past abrupt warming events. This evidence appears consistent with a dynamic response of biological N fixation to increasing N demand by ecosystems, thereby reducing N limitation of plant productivity and supporting a land sink for atmospheric CO ₂ .

Twenty-first century ocean warming, acidification, deoxygenation, and upper-ocean nutrient and primary production decline from CMIP6 model projections

We assess 21st century projections of marine biogeochemistry in the CMIP6 Earth system models. These models represent the most up-to-date understanding of climate change. The models generally project greater surface ocean warming, acidification, subsurface deoxygenation, and euphotic nitrate reductions but lesser primary production declines than the previous generation of models. This has major implications for the impact of anthropogenic climate change on marine ecosystems.

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