Journal of Geophysical Research: Earth Surface最新文献

{"title":"Life Cycles and Polycyclicity of Mega Retrogressive Thaw Slumps in Arctic Permafrost Revealed by 2D/3D Geophysics and Long-Term Retreat Monitoring","authors":"Michael Krautblatter,&nbsp;Michael Angelopoulos,&nbsp;Wayne H. Pollard,&nbsp;Hugues Lantuit,&nbsp;Josefine Lenz,&nbsp;Michael Fritz,&nbsp;Nicole Couture,&nbsp;Saskia Eppinger","doi":"10.1029/2023JF007556","DOIUrl":"https://doi.org/10.1029/2023JF007556","url":null,"abstract":"<p>Mega retrogressive thaw slumps (MRTS, &gt;10⁶ m³) are a major threat to Arctic infrastructure, alter regional biogeochemistry, and impact Arctic carbon budgets. However, processes initiating and reactivating MRTS are insufficiently understood. We hypothesize that MRTS preferentially develop a polycyclic behavior because the material is thermally and mechanically prepared for subsequent generation failure. In contrast to remote sensing, geophysical reconnaissance reveals the inner structure and relative thermal state of MRTS decameters beneath slump surfaces, potentially controlling polycyclicity. Based on their life cycle development, five (M)RTS were studied on Herschel Island, an MRTS hotspot on the Canadian Beaufort coast. We combine &gt;2 km of electrical resistivity tomography (ERT), 500 m of ground-penetrating radar (GPR) and annual monitoring of headwall retreat from 2004 to 2013 to reveal the thermal state, internal structure, and volume loss of slumps. ERT data were calibrated with unfrozen-frozen transitions from frost probing of active layer thickness and shallow boreholes. In initial stage MRTS, ERT displays surficial thermal perturbations a few meters deep, coincident with recent mud pool and mud flow development. In early stage polycyclic MRTS, ERT shows decameter deep-reaching thermal perturbations persisting even 300 years after the last activation. In peak-stage polycyclic MRTS, 3D-ERT highlights actively extending deep-reaching thermal perturbations caused by gully incisions, mud slides and mud flows. GPR and headwall monitoring reveal structural disturbance by historical mud flows, ice-rich permafrost, and a decadal quantification of headwall retreat and slump floor erosion. We show that geophysical signatures identify long-lasting thermal and mechanical disturbances in MRTS predefining their susceptibility to polycyclic reactivation.</p>","PeriodicalId":15887,"journal":{"name":"Journal of Geophysical Research: Earth Surface","volume":"129 10","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023JF007556","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142328471","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Massive Ice Outcrops and Thermokarst Along the Arctic Shelf Edge: By-Products of Ongoing Groundwater Freezing and Thawing in the Sub-Surface","authors":"Charles K. Paull,&nbsp;Jong Kuk Hong,&nbsp;David W. Caress,&nbsp;Roberto Gwiazda,&nbsp;Ji-Hoon Kim,&nbsp;Eve Lundsten,&nbsp;Jennifer B. Paduan,&nbsp;Young Keun Jin,&nbsp;Mathieu J. Duchesne,&nbsp;Tae Siek Rhee,&nbsp;Virginia Brake,&nbsp;Jeffrey Obelcz,&nbsp;Maureen A. L. Walton","doi":"10.1029/2024JF007719","DOIUrl":"https://doi.org/10.1029/2024JF007719","url":null,"abstract":"<p>Substantial seafloor morphological changes are rapidly occurring along the Canadian Arctic shelf edge. Five multibeam bathymetric mapping surveys, each partially covering a 15 km² study area between 120- and 200-m water depth, were conducted over a 12-year time period. These surveys reveal that 65 new craters have developed between 2010 and 2022, averaging 6.5 m and reaching up to 30 m deep. Remotely operated vehicle investigations revealed massive ice outcrops exposed on two newly formed crater flanks. This ice is not relict subaerially formed Pleistocene permafrost because it is hosted in sediments which were deposited in a submarine setting post-deglaciation. Low salinity porewater and sediment core ice samples with depleted oxygen isotopic compositions indicate waters with a meteoric signature are discharging and freezing in this area. These ascending brackish groundwaters are likely derived in part from thawed relict permafrost hundreds of meters under the continental shelf. They refreeze as they approach the −1.4°C seafloor, leading to the development of widespread, near seafloor, sub-bottom ice layers. Conditions appropriate for ice melting also exist nearby where ice is exposed to seawater or warmed by ascending groundwater. Small variations in temperature and salinity lead to shifts between freezing of ascending brackish groundwater or melting of near seafloor ice layers. These conditions have produced a dramatic submarine thermokarst morphology riddled with multi-aged depressions. Thermokarst geohazards may exist, unmapped, on other Arctic margins with groundwater channeled toward the shelf edge by a relict permafrost cap, and sufficiently cold shelf edge bottom water temperatures.</p>","PeriodicalId":15887,"journal":{"name":"Journal of Geophysical Research: Earth Surface","volume":"129 10","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JF007719","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142316929","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Glacier Surges Controlled by the Close Interplay Between Subglacial Friction and Drainage","authors":"Kjetil Thøgersen,&nbsp;Adrien Gilbert,&nbsp;Coline Bouchayer,&nbsp;Thomas Vikhamar Schuler","doi":"10.1029/2023JF007441","DOIUrl":"https://doi.org/10.1029/2023JF007441","url":null,"abstract":"<p>The flow of glaciers and ice sheets is largely influenced by friction at the ice-bed interface that can trigger rapid changes in glacier motion ranging from seasonal velocity variations to cyclic surge instabilities or even devastating glacier collapse. This wide range of transient glacier dynamics is currently not captured by models, and its implications for long-term glacier evolution are uncertain. This highlights the need of developing improved descriptions for processes that occur at the glacier bed. Here, we present a model that describes the evolution of basal friction inspired by a “rate and state” approach, coupled to models of subglacial drainage and glacier flow, and investigate how these couplings affect the dynamics of glaciers. We show that a wide range of sliding behavior results from a feedback loop between subglacial drainage efficiency and friction which depends on the evolution of a frictional state that can be interpreted as the degree of cavitation or till porosity for hard and soft beds, respectively. In our simulations, we find that glaciers are susceptible to surging if they exhibit a transition to velocity weakening friction associated with a poor sensitivity of the drainage capacity to the frictional state. This potential materializes if the local topography and mass balance create the conditions for high water pressure to build up in an area sufficiently large to exceed a critical length. We advocate accounting for feedback loops between friction and drainage as a promising avenue for better understanding dynamical instabilities of glaciers and ice sheets.</p>","PeriodicalId":15887,"journal":{"name":"Journal of Geophysical Research: Earth Surface","volume":"129 10","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023JF007441","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142316928","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seismic Modeling of Bedload Transport in a Gravel-Bed Alluvial Channel","authors":"Loc Luong,&nbsp;Daniel Cadol,&nbsp;Susan Bilek,&nbsp;J. Mitchell McLaughlin,&nbsp;Jonathan B. Laronne,&nbsp;Jens M. Turowski","doi":"10.1029/2024JF007761","DOIUrl":"https://doi.org/10.1029/2024JF007761","url":null,"abstract":"<p>Recent theoretical models and field observations suggest that fluvial bedload flux can be estimated from seismic energy measured within appropriate frequency bands. We present an application of the Tsai et al. (2012, https://doi.org/10.1029/2011gl050255) bedload seismic model to an ephemeral channel located in the semi-arid southwestern US and incorporate modifications to better estimate bedload flux in this environment. To test the model, we collected streambank seismic signals and directly measured bedload flux during four flash-floods. Bedload predictions calculated by inversion from the Tsai model underestimated bedload flux observations by one-to-two orders of magnitude at low stages. However, model predictions were better for moderate flow depths (&gt;50 cm), where saltation is expected to dominate bedload transport. We explored three differences between the model assumptions and our field conditions: (a) rolling and sliding particles have different impact frequencies than saltating particles; (b) the velocity and angle of impact of rolling particles onto the riverbed differ; and (c) the fine-grained alluvial character of this and similar riverbeds leads to inelastic impacts, as opposed to the originally conceptualized elastic impacts onto rigid bedrock. We modified the original model to assume inelastic bed impacts and to incorporate rolling and sliding by adjusting the statistical distributions of bedload impact frequency, velocity, and angle. Our modified “multiple-transport-mode bedload seismic model” decreased error relative to observations to less than one order of magnitude across all measured flow conditions. Further investigations in other environmental settings are required to demonstrate the robustness and general applicability of the model.</p>","PeriodicalId":15887,"journal":{"name":"Journal of Geophysical Research: Earth Surface","volume":"129 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142316685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Segregation-Induced Flow Transitions in Rock-Ice Mixtures: Implications for Rock-Ice Avalanche Dynamics","authors":"Gordon G. D. Zhou,&nbsp;Kahlil F. E. Cui,&nbsp;Lu Jing,&nbsp;Anne Mangeney,&nbsp;Yifei Cui,&nbsp;Yu Huang,&nbsp;Xiaoqing Chen","doi":"10.1029/2024JF007831","DOIUrl":"https://doi.org/10.1029/2024JF007831","url":null,"abstract":"<p>Global climate change has been intensifying the scale and frequency of rock-ice avalanches and similar catastrophic mass movements in high-mountain regions. The difference in the physical characteristics of rock and ice particles leads to mixing and segregation during flow. Although, both particle segregation and the presence of ice fundamentally alter flow behavior, the joint influence and feedback of these two aspects are overlooked in state-of-the-art rock-ice avalanche models. Using discrete element simulations, we show that by controlling the distribution of inter-particle frictional interactions within the mixture, segregation patterns resulting from the size, density, concentration, and surface friction differences of rock and ice phases can induce sharp velocity gradients along the flowing thickness. Flowing layers where low friction contacts with ice are abundant tend to flow faster and can induce slow creeping motion in an otherwise static basal layer dominated by more frictional rocks. Based on these observations, we find that the effective friction of rock-ice flows for various mixture concentrations and size ratios can be obtained as a sum of the single-phase rheologies of rocks and ice weighted according to their microscopic contact probabilities. This effective friction for rock-ice mixtures allows us to extend a recent non-local granular fluidity framework that captures the complex segregation-flow feedback mechanism in rock-ice flows. The findings provide a deeper micromechanical understanding of how particle interactions influence rock-ice avalanche mobility, which ultimately improves flow models needed for hazard assessment and mitigation.</p>","PeriodicalId":15887,"journal":{"name":"Journal of Geophysical Research: Earth Surface","volume":"129 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142313367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Catchment-Averaged Erosion Rates Reveal Signals of Divide Migration and Drainage Capture","authors":"A. M. Hoskins,&nbsp;M. Attal,&nbsp;S. M. Mudd,&nbsp;M. Castillo","doi":"10.1029/2024JF007701","DOIUrl":"10.1029/2024JF007701","url":null,"abstract":"&lt;p&gt;Divide migration and drainage capture contribute to drainage reorganization. The relative contributions of each are debated, as are the extent to which an observable signal of drainage reorganization may be preserved in quantifiable erosion rates. We numerically model divide migration and drainage capture, and monitor the effects on catchment-averaged erosion rates in the growing (area gaining) and shrinking (area losing) catchments. Divide migration produces a rapid increase in catchment-averaged erosion rates in the headwaters of the growing catchment. However, we find this catchment-averaged erosion rate signal is quickly obscured with increasing distance downstream in non-uniform uplift settings, limiting our ability to detect divide migration through catchment-averaged erosion rate measurements in non-uniform uplift settings. Drainage capture produces the strongest catchment-averaged erosion rate signal immediately adjacent to the point of capture. We find this signal persists in the landscape longest, and without depleting in magnitude, in the area upstream of the point of capture. The Sierra la Laguna mountain range (Mexico) displays substantial evidence of recent and ongoing drainage capture across the main drainage divide, including: beheaded catchments, windgaps, barbed drainages, &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;χ&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $chi $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; profiles and across divide Gilbert Metrics. We use the Sierra la Laguna to test the detectability of drainage reorganization related catchment-averaged erosion rate signals in a natural setting. &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mmultiscripts&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;B&lt;/mi&gt;\u0000 &lt;mi&gt;e&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;mprescripts&gt;&lt;/mprescripts&gt;\u0000 &lt;none&gt;&lt;/none&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;10&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/mmultiscripts&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${}^{10}Be$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;-derived catchment-averaged erosion rates are found to be twice as fast in the suspected growing catchment headwaters (0.17 &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;m&lt;/mi&gt;\u0000 &lt;mi&gt;m&lt;/mi&gt;\u0000 &lt;mspace&gt;&lt;/mspace&gt;\u0000 &lt;mi&gt;y&lt;/mi&gt;\u0000 &lt;msup&gt;\u0000 &lt;mi&gt;r&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $mm y{r}^{-1}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math","PeriodicalId":15887,"journal":{"name":"Journal of Geophysical Research: Earth Surface","volume":"129 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JF007701","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267497","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterizing Seismic Activity From a Rock Cliff With Unsupervised Learning","authors":"Alexi Morin,&nbsp;Bernard Giroux,&nbsp;Francis Gauthier","doi":"10.1029/2024JF007799","DOIUrl":"10.1029/2024JF007799","url":null,"abstract":"<p>Passive seismic monitoring (PSM) is emerging as a tool for detecting rockfall events and pre-failure seismicity. In this paper, the potential of PSM for rockfall monitoring is assessed through a case study carried out in Gros-Morne, Eastern Québec, in a region with prominent roadside cliffs, where more than 500 fallen rocks are found on the main regional road each year. The proposed method relies on using sensitive STA-LTA windows to detect a very large number of seismic events and build a comprehensive catalog. In total, more than 70,000 seismic events were detected over one year. Gaussian mixtures are used to partition the data set. Based on visual inspection of the data, a main working hypothesis is that the seismic events can be clustered into three groups. After analyzing the spatio-temporal distribution of the events in each group, we find that the events of one cluster can be associated with anthropogenic activity. The frequency of occurrence of the events of the different clusters and their link with meteorological data is also examined through a regression exercise, to assess the importance of the meteorological variables as explanatory variables. The results allow us to postulate on the physical origins of the signals in the different clusters, attributing them to rockfall activity and wind-induced seismic noise.</p>","PeriodicalId":15887,"journal":{"name":"Journal of Geophysical Research: Earth Surface","volume":"129 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JF007799","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267498","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Constraining the Effect of Climate and Rock Porosity on Weathering Extent in the Volcanic Island of Santa Cruz (Galápagos, Ecuador)","authors":"R. Paque,&nbsp;I. Alomia Herrera,&nbsp;J. L. Dixon,&nbsp;A. Molina,&nbsp;F. Zehetner,&nbsp;V. Vanacker","doi":"10.1029/2024JF007651","DOIUrl":"https://doi.org/10.1029/2024JF007651","url":null,"abstract":"<p>Volcanic soils are among the most productive soils in the world as they can accumulate large amounts of organic carbon and nitrogen and have good water storage capacity. They are extensively used worldwide for agriculture, which makes it difficult to study the soil-landscape dynamics under natural conditions. By working in the Galápagos Islands, a UNESCO World Heritage Site, we aimed to constrain soil development over millennial timescales using empirical data. Our monitoring sites on Santa Cruz Island cover a 10 km long NW-SE transect with an 8-fold increase in precipitation and associated vegetation changes. By controlling for age and chemical composition of the basaltic parent material, we investigated the influence of precipitation rates on soil weathering. At the landscape scale, soil weathering degree increased with increasing precipitation, as shown by the spatial patterns in soil depth, pH, mass loss coefficients, chemical index of alteration, chemical depletion fraction, and total reserve in bases. In addition to the climatic effect, rock porosity strongly enhanced basalt weathering. Porosity-enhanced weathering is particularly important in the humid and perhumid precipitation regimes: soils developed on porous scoriae developed weathering mantles that are ∼10-fold thicker and have 10-fold higher mass losses due to weathering compared to soils developed on basalt lava flows. Our results demonstrated that variations in rock pore dimensions and distribution can lead to large variations in basalt weathering rates, particularly in humid and perhumid climates where deep leaching can be facilitated by rock porosity.</p>","PeriodicalId":15887,"journal":{"name":"Journal of Geophysical Research: Earth Surface","volume":"129 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JF007651","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142273263","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evolution of Turbulent Boundary Conditions on the Surface of Large Barchan Dunes: Anomalies in Aerodynamic Roughness and Shear Velocity, Aeolian Threshold, and the Role of Dune Skewness","authors":"M. Y. Louge,&nbsp;A. Valance,&nbsp;J. Fang,&nbsp;S. J. Harnett,&nbsp;F. Porté-Agel,&nbsp;P. Chasle","doi":"10.1029/2023JF007599","DOIUrl":"https://doi.org/10.1029/2023JF007599","url":null,"abstract":"<p>We recorded aerodynamic roughness and shear velocity along transects on and around mature crescent-shaped barchan dunes of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>4.5</mn>\u0000 <mspace></mspace>\u0000 <mi>m</mi>\u0000 </mrow>\u0000 <annotation> $4.5 mathrm{m}$</annotation>\u0000 </semantics></math> and <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>27</mn>\u0000 <mspace></mspace>\u0000 <mi>m</mi>\u0000 </mrow>\u0000 <annotation> $27 mathrm{m}$</annotation>\u0000 </semantics></math> height above the horizontal rock-covered Qatar desert by fitting to the log-law time-averaged vertical velocity profiles acquired from triads of ultrasonic anemometers penetrating the inner turbulent boundary layer. Shear velocity first decreased, then recovered as air climbed on the dune, with a local maximum ahead of the crest as predicted by the Jackson and Hunt (1975, https://doi.org/10.1002/qj.49710143015) theory. Unlike flows over gentler bedforms without a slope discontinuity, an anomalous peak of shear velocity also arose on the dune centerline at the brink, which the theory attributed to skewness in the dune transect profile. The onset of aeolian transport produced a log-law passing through the Bagnold (1941, https://doi.org/10.1007/978-94-009-5682-7) focal point. It was bracketed by noticeable hysteretic peaks in the correlation between wind speed and entrained sand flux. The dunes' rocky surroundings and topography produced an aerodynamic roughness at odds with the Nikuradse (1933, https://ntrs.nasa.gov/citations/19930093938) data for fully developed turbulent boundary layers. Large-eddy numerical simulations illustrated the sensitivity of shear velocity to wide changes in aerodynamic roughness from desert floor to dune surface.</p>","PeriodicalId":15887,"journal":{"name":"Journal of Geophysical Research: Earth Surface","volume":"129 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023JF007599","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142245029","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Topography Controls Variability in Circumpolar Permafrost Thaw Pond Expansion","authors":"C. J. Abolt,&nbsp;A. L. Atchley,&nbsp;D. R. Harp,&nbsp;M. T. Jorgenson,&nbsp;C. Witharana,&nbsp;W. R. Bolton,&nbsp;J. Schwenk,&nbsp;T. Rettelbach,&nbsp;G. Grosse,&nbsp;J. Boike,&nbsp;I. Nitze,&nbsp;A. K. Liljedahl,&nbsp;C. T. Rumpca,&nbsp;C. J. Wilson,&nbsp;K. E. Bennett","doi":"10.1029/2024JF007675","DOIUrl":"https://doi.org/10.1029/2024JF007675","url":null,"abstract":"<p>One of the most conspicuous signals of climate change in high-latitude tundra is the expansion of ice wedge thermokarst pools. These small but abundant water features form rapidly in depressions caused by the melting of ice wedges (i.e., meter-scale bodies of ice embedded within the top of the permafrost). Pool expansion impacts subsequent thaw rates through a series of complex positive and negative feedbacks which play out over timescales of decades and may accelerate carbon release from the underlying sediments. Although many local observations of ice wedge thermokarst pool expansion have been documented, analyses at continental to pan-Arctic scales have been rare, hindering efforts to project how strongly this process may impact the global carbon cycle. Here we present one of the most geographically extensive and temporally dense records yet compiled of recent pool expansion, in which changes to pool area from 2008 to 2020 were quantified through satellite-image analysis at 27 survey areas (measuring 10–35 km² each, or 400 km² in total) dispersed throughout the circumpolar tundra. The results revealed instances of rapid expansion at 44% (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>±</mo>\u0000 </mrow>\u0000 <annotation> $pm $</annotation>\u0000 </semantics></math>15%) of survey areas. Considered alone, the extent of departures from historical mean air temperatures did not account for between site variation in rates of change to pool area. Pool growth was most clearly associated with upland (i.e., hilly) terrain and elevated silt content at soil depths greater than one meter. These findings suggest that, at short time scales, pedologic and geomorphologic conditions may exert greater control on pool dynamics in the warming Arctic than spatial variability in the rate of air temperature increases.</p>","PeriodicalId":15887,"journal":{"name":"Journal of Geophysical Research: Earth Surface","volume":"129 9","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JF007675","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142245031","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}