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Soil-biodegradable plastic films do not decompose in a lake sediment over 9 months of incubation

Agriculture relies heavily on plastic mulch films, which may be transported to aquatic environments. We investigated the breakdown of soil-biodegradable agricultural mulch films in lake sediments. After 40 weeks, films were intact, and no significant CO2 or CH4 was produced from the biodegradable mulch films. We conclude that the mulch films we used have a low biodegradability in lake sediments. The sediment lacks the microbes needed to break down the biodegradable plastics that were used here.

Linear polarization signatures of atmospheric dust with the SolPol direct-sun polarimeter

Atmospheric dust particles may present a preferential alignment due to their shape on long range transport. Since dust is abundant and plays a key role to global climate, the elusive observation of orientation will be a game changer to existing measurement techniques and the representation of particles in climate models. We utilize a specifically designed instrument, SolPol, and target the Sun from the ground for large polarization values under dusty conditions, a clear sign of orientation.

Biomineralization of amorphous Fe-, Mn- and Si-rich mineral phases by cyanobacteria under oxic and alkaline conditions

Iron and manganese are poorly soluble in oxic and alkaline solutions but much more soluble under anoxic conditions. As a result, authigenic minerals rich in Fe and/or Mn have been viewed as diagnostic of anoxic conditions. However, here we reveal a new case of biomineralization by specific cyanobacteria, forming abundant Fe(III)- and Mn(IV)-rich amorphous phases under oxic conditions in an alkaline lake. This might be an overlooked biotic contribution to the scavenging of Fe from water columns.

Rapid saturation of cloud water adjustments to shipping emissions

Aerosol from burning fuel changes cloud properties, e.g., the number of droplets and the content of water. Here, we study how clouds respond to different amounts of shipping aerosol. Droplet numbers increase linearly with increasing aerosol over a broad range until they stop increasing, while the amount of liquid water always increases, independently of emission amount. These changes in cloud properties can make them reflect more or less sunlight, which is important for the earth’s climate.

SI-traceable validation of a laser spectrometer for balloon-borne measurements of water vapor in the upper atmosphere

The abundance of water vapor (H2O) in the upper atmosphere has a significant impact on the rate of global warming. We developed a new lightweight spectrometer (ALBATROSS) for H2O measurements aboard meteorological balloons. Here, we assess the accuracy and precision of ALBATROSS using metrology-grade reference gases. The results demonstrate the exceptional potential of mid-infrared laser absorption spectroscopy as a new reference method for in situ measurements of H2O in the upper atmosphere.

Emulating lateral gravity wave propagation in a global chemistry–climate model (EMAC v2.55.2) through horizontal flux redistribution

The columnar approach of gravity wave (GW) schemes results in dynamical model biases, but parallel decomposition makes horizontal GW propagation computationally unfeasible. In the global model EMAC, we approximate it by GW redistribution at one altitude using tailor-made redistribution maps generated with a ray tracer. More spread-out GW drag helps reconcile the model with observations and close the 60°S GW gap. Polar vortex dynamics are improved, enhancing climate model credibility.

Methane emissions due to reservoir flushing: a significant emission pathway?

Biogeosciences
DOI 10.5194/bg-20-4057-2023
25 September 2023

Based on a large dataset of seasonally resolved methane (CH4) pore water concentrations in a reservoir’s sediment, we assess the significance of CH4 emissions due to reservoir flushing. In the studied reservoir, CH4 emissions caused by one flushing operation can represent 7 %–14 % of the annual CH4 emissions and depend on the timing of the flushing operation. In reservoirs with high sediment loadings, regular flushing may substantially contribute to the overall CH4 emissions.

Element ∕ Ca ratios in Nodosariida (Foraminifera) and their potential application for paleoenvironmental reconstructions

Biogeosciences
DOI 10.5194/bg-20-4043-2023
22 September 2023

We analyzed Mg / Ca and other El / Ca (Na / Ca, B / Ca, Sr / Ca and Ba / Ca) in Nodosariata. Their calcite chemistry is markedly different to that of the other calcifying orders of foraminifera. We show a relation between the species average Mg / Ca and its sensitivity to changes in temperature. Differences were reflected in both the Mg incorporation and the sensitivities of Mg / Ca to temperature.

Advancing the estimation of future climate impacts within the United States

This study utilizes a reduced-complexity model, Framework for Evaluating Damages and Impacts (FrEDI), to assess the impacts from climate change in the United States across 10 000 future probabilistic emission and socioeconomic projections. Climate-driven damages are largest for the health category, with the majority of damages in this category coming from the valuation estimates of premature mortality attributable to climate-driven changes in extreme temperature and air quality scenarios.

Molecular simulations reveal that heterogeneous ice nucleation occurs at higher temperatures in water under capillary tension

Using computer simulations of water, we find that water under tension freezes more easily than under normal conditions. A linear equation describes how freezing temperature increases with tension. Accordingly, simulations show that naturally occurring tension in water capillary bridges leads to higher freezing temperatures. This work is an early step in determining if atmospheric cloud droplets freeze due to naturally occurring tension, for example, during processes such as droplet collisions.

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