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1. The Net GHG Balance and Budget of the Permafrost Region (2000–2020) From Ecosystem Flux Upscaling

   https://doi.org/10.1029/2023GB007953  

   Ramage, Justine; Kuhn, McKenzie; Virkkala, Anna‐Maria; Voigt, Carolina; Marushchak, Maija E; Bastos, Ana; Biasi, Christina; Canadell, Josep G; Ciais, Philippe; López‐Blanco, Efrèn; et al (April 2024, Global Biogeochemical Cycles)

   Abstract The northern permafrost region has been projected to shift from a net sink to a net source of carbon under global warming. However, estimates of the contemporary net greenhouse gas (GHG) balance and budgets of the permafrost region remain highly uncertain. Here, we construct the first comprehensive bottom‐up budgets of CO₂, CH₄, and N₂O across the terrestrial permafrost region using databases of more than 1000 in situ flux measurements and a land cover‐based ecosystem flux upscaling approach for the period 2000–2020. Estimates indicate that the permafrost region emitted a mean annual flux of 12 (−606, 661) Tg CO₂–C yr⁻¹, 38 (22, 53) Tg CH₄–C yr⁻¹, and 0.67 (0.07, 1.3) Tg N₂O–N yr⁻¹to the atmosphere throughout the period. Thus, the region was a net source of CH₄and N₂O, while the CO₂balance was near neutral within its large uncertainties. Undisturbed terrestrial ecosystems had a CO₂sink of −340 (−836, 156) Tg CO₂–C yr⁻¹. Vertical emissions from fire disturbances and inland waters largely offset the sink in vegetated ecosystems. When including lateral fluxes for a complete GHG budget, the permafrost region was a net source of C and N, releasing 144 (−506, 826) Tg C yr⁻¹and 3 (2, 5) Tg N yr⁻¹. Large uncertainty ranges in these estimates point to a need for further expansion of monitoring networks, continued data synthesis efforts, and better integration of field observations, remote sensing data, and ecosystem models to constrain the contemporary net GHG budgets of the permafrost region and track their future trajectory. 

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2. Combining Eddy Covariance Towers, Field Measurements, and the MEMS 2 Ecosystem Model Improves Confidence in the Climate Impacts of Bioenergy With Carbon Capture and Storage

   https://doi.org/10.1111/gcbb.70023  

   Falvo, Grant; Zhang, Yao; Abraha, Michael; Mosier, Samantha; Su, Yahn‐Jauh; Lei, Cheyenne; Chen, Jiquan; Cotrufo, M Francesca; Robertson, G Philip (March 2025, GCB Bioenergy)

   ABSTRACT Carbon dioxide removal technologies such as bioenergy with carbon capture and storage (BECCS) are required if the effects of climate change are to be reversed over the next century. However, BECCS demands extensive land use change that may create positive or negative radiative forcing impacts upstream of the BECCS facility through changes to in situ greenhouse gas fluxes and land surface albedo. When quantifying these upstream climate impacts, even at a single site, different methods can give different estimates. Here we show how three common methods for estimating the net ecosystem carbon balance of bioenergy crops established on former grassland or former cropland can differ in their central estimates and uncertainty. We place these net ecosystem carbon balance forcings in the context of associated radiative forcings from changes to soil N₂O and CH₄fluxes, land surface albedo, embedded fossil fuel use, and geologically stored carbon. Results from long term eddy covariance measurements, a soil and plant carbon inventory, and the MEMS 2 process‐based ecosystem model all agree that establishing perennials such as switchgrass or mixed prairie on former cropland resulted in net negative radiative forcing (i.e., global cooling) of −26.5 to −39.6 fW m⁻²over 100 years. Establishing these perennials on former grassland sites had similar climate mitigation impacts of −19.3 to −42.5 fW m⁻². However, the largest climate mitigation came from establishing corn for BECCS on former cropland or grassland, with radiative forcings from −38.4 to −50.5 fW m⁻², due to its higher plant productivity and therefore more geologically stored carbon. Our results highlight the strengths and limitations of each method for quantifying the field scale climate impacts of BECCS and show that utilizing multiple methods can increase confidence in the final radiative forcing estimates. 

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3. Estimates of global surface water dynamics harnessing near real-time land cover observations and open science geospatial capabilities

   https://doi.org/10.1088/1748-9326/ae137b  

   Khare, Arushi; Gupta, Bikas C; Rajib, Adnan; Vanderhoof, Melanie; Wu, Qiusheng (December 2025, Environmental Research Letters)

   Spatio-temporal changes to our world’s surface water resources are escalating. Translating how these changes impact communities and ecosystems requires time-varying data of Global Surface Water Extents (GSWE). Traditionally, GSWE mapping has been limited to static estimates, with recent efforts focusing on annual averages, frequency and occurrence of long-term variations. Building upon these foundational capabilities, we harnessed remotely sensed Sentinel-2 based near real-time Dynamic World (DW) land cover products to produce the first-of-its-kind 10 m resolution GSWE dataset representing 2015–2023. Our dataset estimated 2.5 million km²of permanent waters and 8 million km²of seasonal waters worldwide. Comparing our Sentinel-2 based data to contemporary Landsat-based GSWE, we observed that our data mapped less water within the >50% probability of occurrence range, suggesting a lower presence of open permanent water especially in high latitudes, deviating from what we previously learnt from Landsat data. Statistical analysis compared to well-established observational products and widely used GSWE datasets across some of the world’s most ecologically significant regions, including Pantanal in South America and Haor in South Asia, supports the overall physical realism of our data in predicting global open surface water dynamics. Our key contribution is a prototype Open Science operational framework that extracts routinely available DW products, runs geospatial analytics, and creates actionable water information for educators, researchers, and stakeholders at any scale of practical interest. We present examples of this operational capability through instant mapping of flood in Spain and drought in Lake Urmia, Central Asia, frequent monitoring of river extent changes at the Ganges–Brahmaputra confluence, and above all, interoperability with other existing GSWE applications. 

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4. Increased Terrestrial Carbon Export and CO ₂ Evasion From Global Inland Waters Since the Preindustrial Era

   https://doi.org/10.1029/2023GB007776  

   Tian, Hanqin; Yao, Yuanzhi; Li, Ya; Shi, Hao; Pan, Shufen; Najjar, Raymond G; Pan, Naiqing; Bian, Zihao; Ciais, Philippe; Cai, Wei‐Jun; et al (October 2023, Global Biogeochemical Cycles)

   Abstract Global carbon dioxide (CO₂) evasion from inland waters (rivers, lakes, and reservoirs) and carbon (C) export from land to oceans constitute critical terms in the global C budget. However, the magnitudes, spatiotemporal patterns, and underlying mechanisms of these fluxes are poorly constrained. Here, we used a coupled terrestrial–aquatic model to assess how multiple changes in climate, land use, atmospheric CO₂concentration, nitrogen (N) deposition, N fertilizer and manure applications have affected global CO₂evasion and riverine C export along the terrestrial‐aquatic continuum. We estimate that terrestrial C loadings, riverine C export, and CO₂evasion in the preindustrial period (1800s) were 1,820 ± 507 (mean ± standard deviation), 765 ± 132, and 841 ± 190 Tg C yr⁻¹, respectively. During 1800–2019, multifactorial global changes caused an increase of 25% (461 Tg C yr⁻¹) in terrestrial C loadings, reaching 2,281 Tg C yr⁻¹in the 2010s, with 23% (104 Tg C yr⁻¹) of this increase exported to the ocean and 59% (273 Tg C yr⁻¹) being emitted to the atmosphere. Our results showed that global inland water recycles and exports nearly half of the net land C sink into the atmosphere and oceans, highlighting the important role of inland waters in the global C balance, an amount that should be taken into account in future C budgets. Our analysis supports the view that a major feature of the global C cycle–the transfer from land to ocean–has undergone a dramatic change over the last two centuries as a result of human activities. 

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5. Nitrate Loads From Land to Stream Are Balanced by In‐Stream Nitrate Uptake Across Seasons in a Dryland Stream Network

   https://doi.org/10.1029/2024JG008117  

   Handler, Amalia M; Helton, Ashley M; Grimm, Nancy B (November 2024, Journal of Geophysical Research: Biogeosciences)

   Abstract Exploring nitrogen dynamics in stream networks is critical for understanding how these systems attenuate nutrient pollution while maintaining ecological productivity. We investigated Oak Creek, a dryland watershed in central Arizona, USA, to elucidate the relationship between terrestrial nitrate (NO₃⁻) loading and stream NO₃⁻uptake, highlighting the influence of land cover and hydrologic connectivity. We conducted four seasonal synoptic sampling campaigns along the 167‐km network combined with stream NO₃⁻uptake experiments (in 370–710‐m reaches) and integrated the data in a mass‐balance model to scale in‐stream uptake and estimate NO₃⁻loading from landscape to the stream network. Stream NO₃⁻concentrations were low throughout the watershed (<5–236 μg N/L) and stream NO₃⁻vertical uptake velocity was high (5.5–18.0 mm/min). During the summer dry (June), summer wet (September), and winter dry (November) seasons, the lower mainstem exhibited higher lateral NO₃⁻loading (10–51 kg N km⁻² d⁻¹) than the headwaters and tributaries (<0.001–0.086 kg N km⁻² d⁻¹), likely owing to differences in irrigation infrastructure and near‐stream land cover. In contrast, during the winter wet season (February) lateral NO₃⁻loads were higher in the intermittent headwaters and tributaries (0.008–0.479 kg N km⁻² d⁻¹), which had flowing surface water only in this season. Despite high lateral NO₃⁻loading in some locations, in‐stream uptake removed >81% of NO₃⁻before reaching the watershed outlet. Our findings highlight that high rates of in‐stream uptake maintain low nitrogen export at the network scale, even with high fluxes from the landscape and seasonal variation in hydrologic connectivity. 

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