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1. The tension-activated carbon–carbon bond

   https://doi.org/10.1016/j.chempr.2024.05.012  

   Sun, Yunyan; Kevlishvili, Ilia; Kouznetsova, Tatiana B; Burke, Zach P; Craig, Stephen L; Kulik, Heather J; Moore, Jeffrey S (June 2024, Chem)

   Mechanical force drives distinct chemical reactions; yet, its vectoral nature results in complicated coupling with reaction trajectories. Here, we utilize a physical organic model inspired by the classical Morse potential and its differential forms to identify effective force constant (keff) and reaction energy (ΔE) as key molecular features that govern mechanochemical kinetics. Through a comprehensive experimental and computational investigation with four norborn-2-en-7-one (NEO) mechanophores, we establish the relationship between these features and the force-dependent energetic changes along the reaction pathways. We show that the complex kinetic behavior of the tensioned bonds is generally and quantitatively predicted by a simple multivariate linear regression based on the two easily computed features with a straightforward workflow. These results demonstrate a general mechanistic framework for mechanochemical reactions under tensile force and provide a highly accessible tool for the large-scale computational screening in the design of mechanophores. 

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2. The Sunk Carbon Fallacy: Rethinking Carbon Footprint Metrics for Effective Carbon-Aware Scheduling

   https://doi.org/10.1145/3698038.3698542  

   Bashir, Noman; Gohil, Varun; Subramanya, Anagha Belavadi; Shahrad, Mohammad; Irwin, David; Olivetti, Elsa; Delimitrou, Christina (November 2024, ACM)

   The rapid increase in computing demand and corresponding energy consumption have focused attention on computing's impact on the climate and sustainability. Prior work proposes metrics that quantify computing's carbon footprint across several lifecycle phases, including its supply chain, operation, and end-of-life. Industry uses these metrics to optimize the carbon footprint of manufacturing hardware and running computing applications. Unfortunately, prior work on optimizing datacenters' carbon footprint often succumbs to the sunk cost fallacy by considering embodied carbon emissions (a sunk cost) when making operational decisions (i.e., job scheduling and placement), which leads to operational decisions that do not always reduce the total carbon footprint. In this paper, we evaluate carbon-aware job scheduling and placement on a given set of servers for several carbon accounting metrics. Our analysis reveals state-of-the-art carbon accounting metrics that include embodied carbon emissions when making operational decisions can increase the total carbon footprint of executing a set of jobs. We study the factors that affect the added carbon cost of such suboptimal decision-making. We then use a real-world case study from a datacenter to demonstrate how the sunk carbon fallacy manifests itself in practice. Finally, we discuss the implications of our findings in better guiding effective carbon-aware scheduling in on-premise and cloud datacenters. 

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3. The Ocean Carbon Cycle

   https://doi.org/10.1146/annurev-environ-120920-111307  

   DeVries, Tim (October 2022, Annual Review of Environment and Resources)

   The ocean holds vast quantities of carbon that it continually exchanges with the atmosphere through the air-sea interface. Because of its enormous size and relatively rapid exchange of carbon with the atmosphere, the ocean controls atmospheric CO 2 concentration and thereby Earth's climate on timescales of tens to thousands of years. This review examines the basic functions of the ocean's carbon cycle, demonstrating that the ocean carbon inventory is determined primarily by the mass of the ocean, by the chemical speciation of CO 2 in seawater, and by the action of the solubility and biological pumps that draw carbon into the ocean's deeper layers, where it can be sequestered for decades to millennia. The ocean also plays a critical role in moderating the impacts of climate change by absorbing an amount of carbon equivalent to about 25% of anthropogenic CO 2 emissions over the past several decades. However, this also leads to ocean acidification and reduces the chemical buffering capacity of the ocean and its future ability to take up CO 2 . This review closes with a look at the uncertain future of the ocean carbon cycle and the scientific challenges that this uncertainty brings. 

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4. Carbon and carbon-13 in the preindustrial and glacial ocean

   https://doi.org/10.1371/journal.pclm.0000434  

   Schmittner, Andreas; Fillman, Nathaniel J (July 2024, PLOS Climate)

   Carré, Matthieu (Ed.)

   Despite their importance for Earth’s climate and paleoceanography, the cycles of carbon (C) and its isotope¹³C in the ocean are not well understood. Models typically do not decompose C and¹³C storage caused by different physical, biological, and chemical processes, which makes interpreting results difficult. Consequently, basic observed features, such as the decreased carbon isotopic signature (δ¹³C_DIC) of the glacial ocean remain unexplained. Here, we review recent progress in decomposing Dissolved Inorganic Carbon (DIC) into preformed and regenerated components, extend a precise and complete decomposition to δ¹³C_DIC, and apply it to data-constrained model simulations of the Preindustrial (PI) and Last Glacial Maximum (LGM) oceans. Regenerated components, from respired soft-tissue organic matter and dissolved biogenic calcium carbonate, are reduced in the LGM, indicating a decrease in the active part of the biological pump. Preformed components increase carbon storage and decrease δ¹³C_DICby 0.55 ‰ in the LGM. We separate preformed into saturation and disequilibrium components, each of which have biological and physical contributions. Whereas the physical disequilibrium in the PI is negative for both DIC and δ¹³C_DIC, and changes little between climate states, the biological disequilibrium is positive for DIC but negative for δ¹³C_DIC, a pattern that is magnified in the LGM. The biological disequilibrium is the dominant driver of the increase in glacial ocean C and the decrease in δ¹³C_DIC, indicating a reduced sink of biological carbon. Overall, in the LGM, biological processes increase the ocean’s DIC inventory by 355 Pg more than in the PI, reduce its mean δ¹³C_DICby an additional 0.52 ‰, and contribute 60 ppm to the lowering of atmospheric CO₂. Spatial distributions of the δ¹³C_DICcomponents are presented. Commonly used approximations based on apparent oxygen utilization and phosphate are evaluated and shown to have large errors. 

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5. Biogenic carbon pool production maintains the Southern Ocean carbon sink

   https://doi.org/10.1073/pnas.2217909120  

   Huang, Yibin; Fassbender, Andrea J.; Bushinsky, Seth M. (April 2023, Proceedings of the National Academy of Sciences)

   Through biological activity, marine dissolved inorganic carbon (DIC) is transformed into different types of biogenic carbon available for export to the ocean interior, including particulate organic carbon (POC), dissolved organic carbon (DOC), and particulate inorganic carbon (PIC). Each biogenic carbon pool has a different export efficiency that impacts the vertical ocean carbon gradient and drives natural air–sea carbon dioxide gas (CO₂) exchange. In the Southern Ocean (SO), which presently accounts for ~40% of the anthropogenic ocean carbon sink, it is unclear how the production of each biogenic carbon pool contributes to the contemporary air–sea CO₂exchange. Based on 107 independent observations of the seasonal cycle from 63 biogeochemical profiling floats, we provide the basin-scale estimate of distinct biogenic carbon pool production. We find significant meridional variability with enhanced POC production in the subantarctic and polar Antarctic sectors and enhanced DOC production in the subtropical and sea-ice-dominated sectors. PIC production peaks between 47°S and 57°S near the “great calcite belt.” Relative to an abiotic SO, organic carbon production enhances CO₂uptake by 2.80 ± 0.28 Pg C y⁻¹, while PIC production diminishes CO₂uptake by 0.27 ± 0.21 Pg C y⁻¹. Without organic carbon production, the SO would be a CO₂source to the atmosphere. Our findings emphasize the importance of DOC and PIC production, in addition to the well-recognized role of POC production, in shaping the influence of carbon export on air–sea CO₂exchange. 

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