AGU Advances最新文献

{"title":"RECCAP2 Future Component: Consistency and Potential for Regional Assessment to Constrain Global Projections","authors":"Chris D. Jones,&nbsp;Tilo Ziehn,&nbsp;Jatin Anand,&nbsp;Ana Bastos,&nbsp;Eleanor Burke,&nbsp;Josep G. Canadell,&nbsp;Manoel Cardoso,&nbsp;Yolandi Ernst,&nbsp;Atul K. Jain,&nbsp;Sujong Jeong,&nbsp;Elizabeth D. Keller,&nbsp;Masayuki Kondo,&nbsp;Ronny Lauerwald,&nbsp;Tzu-Shun Lin,&nbsp;Guillermo Murray-Tortarolo,&nbsp;Gert-Jan Nabuurs,&nbsp;Mike O’Sullivan,&nbsp;Ben Poulter,&nbsp;Xiaoyu Qin,&nbsp;Celso von Randow,&nbsp;Marcos Sanches,&nbsp;Dmitry Schepaschenko,&nbsp;Anatoly Shvidenko,&nbsp;T. Luke Smallman,&nbsp;Hanqin Tian,&nbsp;Yohanna Villalobos,&nbsp;Xuhui Wang,&nbsp;Jeongmin Yun","doi":"10.1029/2023AV001024","DOIUrl":"10.1029/2023AV001024","url":null,"abstract":"<p>Projections of future carbon sinks and stocks are important because they show how the world's ecosystems will respond to elevated CO₂ and changes in climate. Moreover, they are crucial to inform policy decisions around emissions reductions to stay within the global warming levels identified by the Paris Agreement. However, Earth System Models from the 6th Coupled Model Intercomparison Project (CMIP6) show substantial spread in future projections—especially of the terrestrial carbon cycle, leading to a large uncertainty in our knowledge of any remaining carbon budget (RCB). Here we evaluate the global terrestrial carbon cycle projections on a region-by-region basis and compare the global models with regional assessments made by the REgional Carbon Cycle Assessment and Processes, Phase 2 activity. Results show that for each region, the CMIP6 multi-model mean is generally consistent with the regional assessment, but substantial cross-model spread exists. Nonetheless, all models perform well in some regions and no region is without some well performing models. This gives confidence that the CMIP6 models can be used to look at future changes in carbon stocks on a regional basis with appropriate model assessment and benchmarking. We find that most regions of the world remain cumulative net sources of CO₂ between now and 2100 when considering the balance of fossil-fuels and natural sinks, even under aggressive mitigation scenarios. This paper identifies strengths and weaknesses for each model in terms of its performance over a particular region including how process representation might impact those results and sets the agenda for applying stricter constraints at regional scales to reduce the uncertainty in global projections.</p>","PeriodicalId":100067,"journal":{"name":"AGU Advances","volume":"4 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2023AV001024","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135474623","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Southern Alaska's Forest Landscape Integrity, Habitat, and Carbon Are Critical for Meeting Climate and Conservation Goals","authors":"B. E. Law,&nbsp;L. T. Berner,&nbsp;C. Wolf,&nbsp;W. J. Ripple,&nbsp;E. J. Trammell,&nbsp;R. A. Birdsey","doi":"10.1029/2023AV000965","DOIUrl":"10.1029/2023AV000965","url":null,"abstract":"<p>The interdependent crises of climate change and biodiversity losses require strategic policies to protect, manage, and restore essential ecosystems. Here, we evaluate the relative importance of US national forests (NFs) for protection and conservation as natural climate and biodiversity solutions. We compared landscape integrity (degree of modification by humans), habitat for three keystone species, forest carbon density, accumulation, and total biomass carbon stocks across 154 NFs in the United States. Southern Alaska's Tongass and Chugach NFs hold disproportionally large amounts of high landscape integrity area among all NFs with 25.3% and 5.6% (total 30.9%) of all high (≥9.6) landscape integrity found on NF lands. The Tongass and Chugach store approximately 33% and 3% of all biomass carbon stocks that occur in NFs with high landscape integrity. These two NFs together account for about 49%, 37%, and 18% of all bald eagle, brown bear, and gray wolf habitat found on NF lands. Gray wolf habitat extent was 4% of the total or less on remaining NFs. The Tongass and Chugach were historically wetter and cooler among NFs, and are projected to experience much larger increases in precipitation and much lower increases in maximum temperatures over the coming century. Combined with relatively low recent occurrence of wildfire, this makes permanence more likely. The Tongass and Chugach forests, along with the Pacific Northwest's high carbon density forests should be a high priority for protection and conservation to meet climate and biodiversity goals given their landscape-scale scarcity and high value.</p>","PeriodicalId":100067,"journal":{"name":"AGU Advances","volume":"4 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2023AV000965","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135933525","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Do Two Climate Wrongs Make a Right?","authors":"David Schimel,&nbsp;Charles Miller","doi":"10.1029/2023AV001020","DOIUrl":"10.1029/2023AV001020","url":null,"abstract":"<p>As the planet approaches local and global exceedance of the 1.5°C stabilization target, damages from climate change, mostly due to extremes, are growing far faster than projected. While assessment models have largely estimated high costs of mitigation, the cost of green energy is dropping faster than projected. Climate policy has assumed that damage costs are manageable while decarbonization is expensive. Both these assumptions are wrong, potentially leading to a tipping point in human behavior: scientists need to explore options aligned with this emerging reality.</p>","PeriodicalId":100067,"journal":{"name":"AGU Advances","volume":"4 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2023AV001020","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135934942","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gas Giant Simulations of Eddy-Driven Jets Accompanied by Deep Meridional Circulation","authors":"Keren Duer,&nbsp;Eli Galanti,&nbsp;Yohai Kaspi","doi":"10.1029/2023AV000908","DOIUrl":"10.1029/2023AV000908","url":null,"abstract":"<p>Jupiter's atmosphere comprises several dynamical regimes: the equatorial eastward flows and surrounding retrograde jets; the midlatitudes, with the eddy-driven, alternating jet-streams and meridional circulation cells; and the jet-free turbulent polar region. Despite intensive research conducted on each of these dynamical regimes over the past decades, they remain only partially understood. Saturn's atmosphere also encompasses similar distinguishable regimes, but observational evidence for midlatitude deep meridional cells is lacking. Models offer a variety of explanations for each of these regions, but only a few are capable of simulating more than one of the regimes at once. This study presents new numerical simulations using a 3D deep anelastic model that can reproduce the equatorial flows as well as the midlatitudinal pattern of the mostly barotropic, alternating eddy-driven jets and the meridional circulation cells accompanying them. These simulations are consistent with recent Juno mission gravity and microwave data. We find that the vertical eddy momentum fluxes are as important as the meridional eddy momentum fluxes, which drive the midlatitudinal circulation on Earth. In addition, we discuss the parameters controlling the number of midlatitudinal jets/cells, their extent, strength, and location. We identify the strong relationship between meridional circulation and the zonal jets in a deep convection setup, and analyze the mechanism responsible for their generation and maintenance. The analysis presented here provides another step in the ongoing pursuit of understanding the deep atmospheres of gas giants.</p>","PeriodicalId":100067,"journal":{"name":"AGU Advances","volume":"4 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2023AV000908","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135870748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modeling Denitrification: Can We Report What We Don't Know?","authors":"B. Grosz,&nbsp;A. Matson,&nbsp;K. Butterbach-Bahl,&nbsp;T. Clough,&nbsp;E. A. Davidson,&nbsp;R. Dechow,&nbsp;S. DelGrosso,&nbsp;E. Diamantopoulos,&nbsp;P. Dörsch,&nbsp;E. Haas,&nbsp;H. He,&nbsp;C. V. Henri,&nbsp;D. Hui,&nbsp;K. Kleineidam,&nbsp;D. Kraus,&nbsp;M. Kuhnert,&nbsp;J. Léonard,&nbsp;C. Müller,&nbsp;S. O. Petersen,&nbsp;D. Sihi,&nbsp;I. Vogeler,&nbsp;R. Well,&nbsp;J. Yeluripati,&nbsp;J. Zhang,&nbsp;C. Scheer","doi":"10.1029/2023AV000990","DOIUrl":"https://doi.org/10.1029/2023AV000990","url":null,"abstract":"<p>Biogeochemical models simulate soil nitrogen (N) turnover and are often used to assess N losses through denitrification. Though models simulate a complete N budget, often only a subset of N pools/fluxes (i.e., N₂O, <math>\u0000 <semantics>\u0000 <mrow>\u0000 <msup>\u0000 <msub>\u0000 <mtext>NO</mtext>\u0000 <mn>3</mn>\u0000 </msub>\u0000 <mo>−</mo>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> ${{text{NO}}_{3}}^{-}$</annotation>\u0000 </semantics></math>, NH₃, NO_<i>x</i>) are published since the full budget cannot be validated with measured data. Field studies rarely include full N balances, especially N₂ fluxes, which are difficult to quantify. Limiting publication of modeling results based on available field data represents a missed opportunity to improve the understanding of modeled processes. We propose that the modeler community support publication of all simulated N pools and processes in future studies.</p>","PeriodicalId":100067,"journal":{"name":"AGU Advances","volume":"4 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71986414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tree Growth Enhancement Drives a Persistent Biomass Gain in Unmanaged Temperate Forests","authors":"Laura Marqués,&nbsp;Ensheng Weng,&nbsp;Harald Bugmann,&nbsp;David I. Forrester,&nbsp;Brigitte Rohner,&nbsp;Martina L. Hobi,&nbsp;Volodymyr Trotsiuk,&nbsp;Benjamin D. Stocker","doi":"10.1029/2022AV000859","DOIUrl":"https://doi.org/10.1029/2022AV000859","url":null,"abstract":"<p>While enhanced tree growth over the last decades has been reported in forests across the globe, it remains unclear whether it drives persistent biomass increases of forest stands, particularly in mature forests. Enhanced tree growth and stand-level biomass are often linked with a simultaneous increase in density-driven mortality and a reduction in tree longevity. Identifying empirical evidence regarding the balance between these processes is challenging due to the confounding effects of stand history, management, and environmental changes. Here, we investigate the link between growth and biomass via the negative relationship between average tree size and stand density (tree number per area). We find increasing stand density for a given mean tree size in unmanaged closed-canopy forests in Switzerland over the past six decades and a positive relationship between tree growth and stand density across forest plots—qualitatively consistent with our simulations using a mechanistic, cohort-resolving ecosystem model (BiomeE). Model simulations show that, in the absence of other disturbances, enhanced tree growth persistently increases biomass stocks despite simultaneous decreases in carbon residence time and tree longevity. However, the magnitude of simulated biomass changes for a given growth enhancement critically depends on the shape of the mortality functions. Our analyses reconcile reports of growth-induced reductions of tree longevity with model predictions of persistent biomass increases, and with our finding of trends toward denser forests in response to growth—also in mature stands.</p>","PeriodicalId":100067,"journal":{"name":"AGU Advances","volume":"4 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2022AV000859","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50138298","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Boundary Upwelling of Antarctic Bottom Water by Topographic Turbulence","authors":"L. E. Baker,&nbsp;A. Mashayek,&nbsp;A. C. Naveira Garabato","doi":"10.1029/2022AV000858","DOIUrl":"https://doi.org/10.1029/2022AV000858","url":null,"abstract":"<p>The lower cell of the meridional overturning circulation (MOC) is sourced by dense Antarctic Bottom Waters (AABWs), which form and sink around Antarctica and subsequently fill the abyssal ocean. For the MOC to “overturn,” these dense waters must upwell via mixing with lighter waters above. Here, we investigate the processes underpinning such mixing, and the resulting water mass transformation, using an observationally forced, high-resolution numerical model of the Drake Passage in the Southern Ocean. In the Drake Passage, the mixing of dense AABW formed in the Weddell Sea with lighter deep waters transported from the Pacific Ocean by the Antarctic Circumpolar Current is catalyzed by energetic flows impinging on rough topography. We find that multiple topographic interaction processes facilitate the mixing of the two water masses, ultimately resulting in the upwelling of waters with neutral density greater than 28.19 kg m⁻³, and the downwelling of the lighter waters above. In particular, we identify the role of sharp density interfaces between AABW and overlying waters and find that the dynamics of the interfaces' interaction with topography can modify many of the processes that generate mixing. Such sharp interfaces between water masses have been observed in several parts of the global ocean, but are unresolved and unrepresented in climate-scale ocean models. We suggest that they are likely to play an important role in abyssal dynamics and mixing, and therefore require further exploration.</p>","PeriodicalId":100067,"journal":{"name":"AGU Advances","volume":"4 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2022AV000858","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50138387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Lithospheric Flexure Controls on Geomorphology, Hydrology, and River Chemistry in the Andean Foreland Basin","authors":"Marisa Repasch,&nbsp;Joel S. Scheingross,&nbsp;Kristen L. Cook,&nbsp;Dirk Sachse,&nbsp;Sophia Dosch,&nbsp;Oscar Orfeo,&nbsp;Niels Hovius","doi":"10.1029/2023AV000924","DOIUrl":"https://doi.org/10.1029/2023AV000924","url":null,"abstract":"<p>Tectonics exerts a strong control over the morphology of Earth's surface that is apparent in active mountain belts. In lowland areas, subtle processes like lithospheric flexure and isostatic rebound can impact Earth surface dynamics, hydrologic connectivity, and topography, suggesting that geomorphic and hydrologic analyses can shed light on underlying lithospheric properties. Here we examine the effect of lithospheric flexure on the geomorphology, hydrology, and river water chemistry of the Rio Bermejo fluvial system in the east Andean foreland basin of northern Argentina. Results show that proximal to the mountain front, foredeep basin subsidence causes sedimentation along a braided channel belt that is superelevated relative to the surrounding flood basin. During floods, water flows from the superelevated channel into the groundwater reservoir, causing a net loss of discharge with distance downstream. Further downstream, forebulge uplift forces channel narrowing, high lateral migration rates, and incision up to 13 m into older river deposits. This incision locally allows groundwater flow into the river, causing a ∼20% increase in river solute load. Groundwater emerges from the forebulge into the backbulge, predominantly as spring-fed channels. Here, channel migration rates decrease, suggesting a switch from net uplift to subsidence that reduces the depth to the groundwater table. This analysis shows that subtle lithospheric flexure can have significant effects on river channel morphology that determine hydrologic flow paths, and ultimately influence geochemical and ecological patterns. We suggest that these effects may elucidate lithospheric properties that are otherwise inferred from bulk geophysical observations.</p>","PeriodicalId":100067,"journal":{"name":"AGU Advances","volume":"4 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023AV000924","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50129641","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The 8-Year Solar Cycle During the Maunder Minimum","authors":"Limei Yan,&nbsp;Fei He,&nbsp;Xinan Yue,&nbsp;Yong Wei,&nbsp;Yuqi Wang,&nbsp;Si Chen,&nbsp;Kai Fan,&nbsp;Hui Tian,&nbsp;Jiansen He,&nbsp;Qiugang Zong,&nbsp;Lidong Xia","doi":"10.1029/2023AV000964","DOIUrl":"https://doi.org/10.1029/2023AV000964","url":null,"abstract":"<p>The presence of grand minima, characterized by significantly reduced solar and stellar activity, brings a challenge to the understanding of solar and stellar dynamo. The Maunder Minimum (1645–1715 AD) is a representative grand solar minimum. The cyclic variation of solar activity, especially the cycle length during this period, is critical to understand the solar dynamo but remains unknown. By analyzing the variations in solar activity-related equatorial auroras recorded in Korean historical books in the vicinity of a low-intensity paleo-West Pacific geomagnetic anomaly, we find clear evidence of an 8-year solar cycle rather than the normal 11-year cycle during the Maunder Minimum. This result provides a key constraint on solar dynamo models and the generation mechanism of grand solar minima.</p>","PeriodicalId":100067,"journal":{"name":"AGU Advances","volume":"4 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023AV000964","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50125996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Constitutive Behavior of Rocks During the Seismic Cycle","authors":"Sylvain Barbot","doi":"10.1029/2023AV000972","DOIUrl":"https://doi.org/10.1029/2023AV000972","url":null,"abstract":"<p>Establishing a constitutive law for fault friction is a crucial objective of earthquake science. However, the complex frictional behavior of natural and synthetic gouges in laboratory experiments eludes explanations. Here, we present a constitutive framework that elucidates the rate, state, and temperature dependence of fault friction under the relevant sliding velocities and temperatures of the brittle lithosphere during seismic cycles. The competition between healing mechanisms, such as viscoelastic collapse, pressure-solution creep, and crack sealing, explains the low-temperature stability transition from steady-state velocity-strengthening to velocity-weakening as a function of slip-rate and temperature. In addition, capturing the transition from cataclastic flow to semi-brittle creep accounts for the stabilization of fault slip at elevated temperatures. We calibrate the model using extensive laboratory data on synthetic albite and granite gouge, and on natural samples from the Alpine Fault and the Mugi Mélange in the Shimanto accretionary complex in Japan. The constitutive model consistently explains the evolving frictional response of fault gouge from room temperature to 600°C for sliding velocities ranging from nanometers to millimeters per second. The frictional response of faults can be uniquely determined by the in situ lithology and the prevailing hydrothermal conditions.</p>","PeriodicalId":100067,"journal":{"name":"AGU Advances","volume":"4 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023AV000972","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50142312","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}