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  • Disappearing cities on US coasts
    Ohenhen, Leonard O.; Shirzaei, Manoochehr; Ojha, Chandrakanta; Sherpa, Sonam F.; Nicholls, Robert J. (Nature Research, 2024-03-06)
    The sea level along the US coastlines is projected to rise by 0.25–0.3 m by 2050, increasing the probability of more destructive flooding and inundation in major cities. However, these impacts may be exacerbated by coastal subsidence— the sinking of coastal land areas—a factor that is often underrepresented in coastal-management policies and long-term urban planning. In this study, we combine high-resolution vertical land motion (that is, raising or lowering of land) and elevation datasets with projections of sea-level rise to quantify the potential inundated areas in 32 major US coastal cities. Here we show that, even when considering the current coastal-defence structures, further land area of between 1,006 and 1,389 km² is threatened by relative sea-level rise by 2050, posing a threat to a population of 55,000–273,000 people and 31,000–171,000 properties. Our analysis shows that not accounting for spatially variable land subsidence within the cities may lead to inaccurate projections of expected exposure. These potential consequences show the scale of the adaptation challenge, which is not appreciated in most US coastal cities.
  • Controls on the Leeside Angle of Dunes in Shallow Unidirectional Flows
    Cisneros, Julia; Best, Jim (Wiley, 2024)
    Dunes are ubiquitous features in alluvial channels, serve as major agents of sediment transport and contribute significantly to flow resistance. Research in the past decade has illustrated the complexity of dune geometry and widespread occurrence of dunes that have a low leeside angle. However, debate exists concerning the occurrence of such dunes and their formative processes. This paper seeks to further our understanding of low-angle dunes by utilizing data from a robust set of shallow flow laboratory experiments detailing equilibrium bedform morphology across a range of sediment transport conditions. Analysis of bedform morphology demonstrates that dunes with low-angle leesides are generated in shallow laboratory flows, and hence are not restricted to deep rivers. Of the possible processes that have been proposed to explain the formation of low-angle dunes, this finding unequivocally shows that liquefied leeside avalanches, which rely on deep flows for their generation, are not a controlling mechanism. In addition, dunes formed under suspension-dominated conditions possess lower leeside angles compared to those formed in bedload-dominated conditions. However, where bedload transport dominates and sediment suspension is likely of lesser importance, low-angle dunes are still present, and preliminary analysis shows that bedform superimposition can result in lowering of the dune leeside angle. Low and intermediate angle dunes formed in these various conditions also have a lower potential for large-scale, permanent, leeside flow separation compared to angle-of-repose dunes, confirming the need to account for these differences in predictions of flow resistance associated with dune form roughness.
  • Transient ice loss in the Patagonia Icefields during the 2015-2016 El Nino event
    Gomez, Demian D.; Bevis, Michael G.; Smalley, Robert; Durand, Michael; Willis, Michael J.; Caccamise, Dana J.; Kendrick, Eric; Skvarca, Pedro; Sobrero, Franco S.; Parra, Hector; Casassa, Gino (Nature Portfolio, 2022-06-10)
    The Patagonia Icefields (PIF) are the largest non-polar ice mass in the southern hemisphere. The icefields cover an area of approximately 16,500 km2 and are divided into the northern and southern icefields, which are ~ 4000 km2 and ~ 12,500 km2, respectively. While both icefields have been losing mass rapidly, their responsiveness to various climate drivers, such as the El Niño-Southern Oscillation, is not well understood. Using the elastic response of the earth to loading changes and continuous GPS data we separated and estimated ice mass changes observed during the strong El Niño that started in 2015 from the complex hydrological interactions occurring around the PIF. During this single event, our mass balance estimates show that the northern icefield lost ~ 28 Gt of mass while the southern icefield lost ~ 12 Gt. This is the largest ice loss event in the PIF observed to date using geodetic data.
  • A Machine Learning Approach to Flood Depth and Extent Detection Using Sentinel 1A/B Synthetic Aperture Radar
    Tiampo, K.; Woods, C.; Huang, L.; Sharma, P.; Chen, Z.; Kar, B.; Bausch, D.; Simmons, C.; Estrada, R.; Willis, Michael J.; Glasscoe, M. (IEEE, 2021-01-01)
    The rising number of flooding events combined with increased urbanization is contributing to significant economic losses due to damages to structures and infrastructures. Here we present a method for producing all weather maps of flood inundation using a combination of synthetic aperture radar (SAR) remote sensing data and machine learning methods that can be used to provide information on the evolution of flood hazards to DisasterAware©, a global alerting system, that is used to disseminate flood risk information to stakeholders across the globe. While these efforts are still in development, a case study is presented for the major flood event associated with Hurricane Harvey and associated floods that impacted Houston, TX in August of 2017.
  • 3D models of the leader valley using satellite & UAV imagery following the 2016 Kaikoura earthquake
    Zekkos, D.; Clark, M.; Willis, Michael J.; Athanasopoulos-Zekkos, A.; Manousakis, J.; Knoper, L.; Stahl, T.; Massey, C.; Archibald, G.; Greenwood, W.; Medwedeff, W. (2018-01-01)
    The ability to quickly, efficiently and reliably characterize changes in the landscape following an earthquake has remained a challenge for the earthquake engineering profession. The 2016 Mw7.8 Kaikoura earthquake provided a unique opportunity to document changes in topography following an earthquake on a regional scale using satellite derived high-resolution digital models. Along-track stereo satellite imagery had been collected for the pre-event topography. Satellites were tasked and collected stereo-mode post-event imagery. Both sets of images were used to create digital surface models (DSMs) of the affected area before and after the event. The procedure followed and indicative results for the Leader valley are presented with emphasis on the challenges associated with the implementation of the technique for the first time in this environment. The valley is of interest because of the variety of features it includes, i.e., the large Leader landslide, smaller landslides, stable sloping and flat ground as well as fault rupture lineaments. The open-source SETSM software is used to provide multiple DSMs. Our workflow is described and results are compared against the DSM created using Structure-from-Motion with imagery collected by Unmanned Aerial Vehicles (UAV) and aerial LIDAR. Overall, the sub-meter agreement between the DSM created using satellites and the DSM created using UAV and LIDAR datasets demonstrates viability for use in seismic studies, but features smaller than about 0.5 m are more difficult to discern.
  • Understanding of Contemporary Regional Sea-Level Change and the Implications for the Future
    Hamlington, Benjamin D.; Gardner, Alex S.; Ivins, Erik; Lenaerts, Jan T. M.; Reager, J. T.; Trossman, David S.; Zaron, Edward D.; Adhikari, Surendra; Arendt, Anthony; Aschwanden, Andy; Beckley, Brian D.; Bekaert, David PS S.; Blewitt, Geoffrey; Caron, Lambert; Chambers, Don P.; Chandanpurkar, Hrishikesh A.; Christianson, Knut; Csatho, Beata; Cullather, Richard; DeConto, Robert M.; Fasullo, John T.; Frederikse, Thomas; Freymueller, Jeffrey T.; Gilford, Daniel M.; Girotto, Manuela; Hammond, William C.; Hock, Regine; Holschuh, Nicholas; Kopp, Robert E.; Landerer, Felix; Larour, Eric; Menemenlis, Dimitris; Merrifield, Mark; Mitrovica, Jerry X.; Nerem, R. Steven; Nias, Isabel J.; Nieves, Veronica; Nowicki, Sophie; Pangaluru, Kishore; Piecuch, Christopher G.; Ray, Richard D.; Rounce, David R.; Schlegel, Nicole-Jeanne; Seroussi, Helene; Shirzaei, Manoochehr; Sweet, William; Velicogna, Isabella; Vinogradova, Nadya; Wahl, Thomas; Wiese, David N.; Willis, Michael J. (American Geophysical Union, 2020-07-20)
    Global sea level provides an important indicator of the state of the warming climate, but changes in regional sea level are most relevant for coastal communities around the world. With improvements to the sea-level observing system, the knowledge of regional sea-level change has advanced dramatically in recent years. Satellite measurements coupled with in situ observations have allowed for comprehensive study and improved understanding of the diverse set of drivers that lead to variations in sea level in space and time. Despite the advances, gaps in the understanding of contemporary sea-level change remain and inhibit the ability to predict how the relevant processes may lead to future change. These gaps arise in part due to the complexity of the linkages between the drivers of sea-level change. Here we review the individual processes which lead to sea-level change and then describe how they combine and vary regionally. The intent of the paper is to provide an overview of the current state of understanding of the processes that cause regional sea-level change and to identify and discuss limitations and uncertainty in our understanding of these processes. Areas where the lack of understanding or gaps in knowledge inhibit the ability to provide the needed information for comprehensive planning efforts are of particular focus. Finally, a goal of this paper is to highlight the role of the expanded sea-level observation network—particularly as related to satellite observations—in the improved scientific understanding of the contributors to regional sea-level change.
  • 'Boundary': mapping and visualizing climatically changed landscapes at Kaskawulsh Glacier and Kluane Lake, Yukon
    Shugar, D. H.; Colorado, K. A.; Clague, J. J.; Willis, Michael J.; Best, J. L. (Taylor & Francis, 2018-06-04)
    This paper describes a collaboration between a visual artist and geoscientists, who together viewed the same rugged, high mountain landscape through different, yet complementary, lenses. We pair scientific mapping and historic comparative photography with a series of site-specific sculptural installations to interpret the dramatic geological changes that occurred at Kaskawulsh Glacier, Yukon, in the spring of 2016. In the summer of that year, artist K.A. Colorado accompanied geoscientists D.H. Shugar, J.J. Clague, and J.L. Best to the terminus of Kaskawulsh Glacier, as well as Kluane Lake downstream of the glacier, to document the landscape changes that occurred earlier in the year. The Boundary images were created as on-site, three-dimensional, artistic interpretations of the markedly changed boundaries that occurred as a result of climate-induced glacier retreat and the sudden subcontinental-scale reorganization of drainage. Both the scientific study conducted by the geomorphologists and the art installations created by the artist were performed simultaneously. The Boundary installation art project, together with satellite imagery and historical photographs, conveys the death of Slims River as a result of climate change.
  • Controls on Eolian Landscape Evolution in Fractured Bedrock
    Perkins, Jonathan P.; Finnegan, Noah J.; de Silva, Shanaka L.; Willis, Michael J. (American Geophysical Union, 2019-11-08)
    Wind abrasion is important for planetary landscape evolution, and wind-abraded bedrock landscapes contain many landforms that are difficult to interpret. Here we exploit a natural experiment in Chile where topographic shielding by an upwind lava flow yields diverse erosional landforms in a downwind ignimbrite. Using a 3-D topographic wind model, we find that low velocities in the wake of a lava lobe coincide with a transition from landforms reflecting fracture-parallel erosion to flow-parallel erosion. Erosion rates across these landforms vary with shear velocity and abrasion susceptibility of the windward escarpment. We hypothesize that this morphologic threshold is controlled by whether particles can be lofted in suspension and overcome topographic steering imposed by fractured bedrock blocks. Within a phase space set by Rouse and Stokes numbers, our data illustrate that wind-abraded landforms reflect a competition between the material skeleton of the landscape and the strength of the flow that shapes it.
  • Sedimentology and geomorphology of a large tsunamigenic landslide, Taan Fiord, Alaska
    Dufresne, A.; Geertsema, M.; Shugar, D. H.; Koppes, M.; Higman, B.; Haeussler, P. J.; Stark, C.; Venditti, J. G.; Bonno, D.; Larsen, C.; Gulick, S. P. S.; McCall, N.; Walton, M.; Loso, M. G.; Willis, Michael J. (Elsevier, 2018-02)
    On 17 October 2015, a landslide of roughly 60 × 106 m3 occurred at the terminus of Tyndall Glacier in Taan Fiord, southeastern Alaska. It caused a tsunami that inundated an area over 20 km2, whereas the landslide debris itself deposited within a much smaller area of approximately 2 km2. It is a unique event in that the landslide debris was deposited into three very different environments: on the glacier surface, on land, and in the marine waters of the fjord. Part of the debris traversed the width of the fjord and re-emerged onto land, depositing coherent hummocks with preserved source stratigraphy on an alluvial fan and adjacent moraines on the far side of the fjord. Imagery from before the landslide shows that the catastrophic slope failure was preceded by deformation and sliding for at least the two decades since the glacier retreated to its current terminus location, exposing steep and extensively faulted slopes. A small volume of the total slide mass remains within the source area and is topped by striated blocks (> 10 m across) and standing trees that were transported down the slope in intact positions during the landslide. Field work was carried out in the summer of 2016, and by the time this paper was written, almost all of the supraglacial debris was advected into the fjord and half the subaerial hummocks were buried by glacial advance; this rapid change illustrates how highly active sedimentary processes in high-altitude glacial settings can skew any landslide-frequency analyses, and emphasizes the need for timely field investigations of these natural hazards.
  • Satellite-derived volume loss rates and glacier speeds for the Cordillera Darwin Icefield, Chile
    Melkonian, A. K.; Willis, Michael J.; Pritchard, M. E.; Rivera, A.; Bown, F.; Bernstein, S. A. (Copernicus, 2013-05-14)
    We produce the first icefield-wide volume change rate and glacier velocity estimates for the Cordillera Darwin Icefield (CDI), a 2605 km2 temperate icefield in southern Chile (69.6°W, 54.6° S). Velocities are measured from optical and radar imagery between 2001-2011. Thirty-six digital elevation models (DEMs) from ASTER and the SRTM DEM are stacked and a weighted linear regression is applied to elevations on a pixel-by-pixel basis to estimate volume change rates. The CDI lost mass at an average rate of -3.9±1.5 Gt yr-1 between 2000 and 2011, equivalent to a sea level rise (SLR) of 0.01±0.004mmyr-1 and an area-averaged thinning rate of -1.5±0.6mw.e.(water equivalent) yr-1. Thinning is widespread, with concentrations near the front of two northern glaciers (Marinelli, Darwin) and one western (CDI-08) glacier. Thickening is apparent in the south, most notably over the advancing Garibaldi Glacier. The northeastern part of the CDI has an average thinning rate of -1.9±0.7mw.e. yr-1, while the southwestern part has an average thinning rate of -1.0±0.4mw.e. yr -1. Velocities are obtained over many of the CDI glaciers for the first time. We provide a repeat speed time series at the Marinelli Glacier. There we measure maximum front speeds of 7.5±0.2mday-1 in 2001, 9.5±0.6mday-1 in 2003 and 10±0.3mday-1 in 2011. The maintenance of high front speeds from 2001 to 2011 supports the hypothesis that Marinelli is in the retreat phase of the tidewater cycle, withdynamic thinning governed by the fjord bathymetry. © Author(s) 2013.
  • Assessment of Sea Level Rise and Associated Impacts for Tuvalu
    Adams, Kyra; Blackwood, Carmen; Cullather, Richard; Hamlington, Benjamin; Heijkoop, Eduard; Karnauskas, Kristopher; Kopp, Robert; Larour, Eric; Lee, Tong; Nerem, R. Steven; Nowicki, Sophie; Piecuch, Christopher G.; Ray, Richard; Rounce, David; Thompson, Philip; Vinogradova, Nadya; Wang, Ou; Willis, Michael J. (2023)
    For low-lying island nations in the Pacific Ocean, increasing sea levels pose an existential threat. One of these nations, Tuvalu, has already begun experiencing impacts driven by the combined effects of the rising ocean, storms, naturally-occurring ocean variability, and changes in other physical processes. These impacts are expected to worsen in the future, and planning and adaptation is underway in Tuvalu. In this technical report, the NASA Sea Level Change Team (NSLCT) assesses the available observations and latest scientific understanding to provide information on future sea level rise and associated impacts for Tuvalu. This report is written in support of the objectives of the Rising Nations Initiative (RNI), enabled by the UN Global Center for Climate Mobility, and serves as a scientific foundation upon which activities and plans can be based.
  • Morphodynamic and modeling insights from global sensitivity analysis of a barrier island evolution model
    Hoagland, Steven; Irish, Jennifer L.; Weiss, Robert (Elsevier, 2024-02)
    Recently developed models of coastal barrier morphodynamics include marsh and lagoon processes that have been shown to impact barrier island evolution. To gain additional insights into the simulated barrier-backbarrier system dynamics, this study explores the parameter space of a barrier evolution model using global sensitivity analysis. Influential parameters, their interactions with one another, and regions of sensitivity within the parameter space were identified using Sobol indices and factor mapping techniques for model results through the end of the century. The results of this study highlight an important relationship between initial and critical barrier island geometries and suggest that narrow and low-relief barriers are most vulnerable to be eroded away (width drowning) or overtaken by sea level rise (height drowning), respectively. Width drowning was also strongly associated with other model input parameters such as toe depth, sea level rise rate, and backbarrier critical bed shear stress, which suggests that sub-centennial drowning is dependent on a unique combination of input parameter values and may be averted (or delayed) with a single input parameter change. Barrier dynamics were significantly influenced by the backbarrier marsh platform, which was more impacted by sediment transport parameters such as critical bed shear stress and ocean sediment concentration than maximum annual overwash flux. This suggests that inorganic sediment deposition through tidal inlet dispersion is much more significant to the backbarrier marsh and lagoon system than overwash over sub-centennial timescales and can help to reduce the risk of width drowning.
  • Ordovician origin and subsequent diversification of the brown algae
    Choi, Seok-Wan; Graf, Louis; Choi, Ji Won; Jo, Jihoon; Boo, Ga Hun; Kawai, Hiroshi; Choi, Chang Geun; Xiao, Shuhai; Knoll, Andrew H.; Andersen, Robert A.; Yoon, Hwan Su (Elsevier, 2024-01-19)
    Brown algae are the only group of heterokont protists exhibiting complex multicellularity. Since their origin, brown algae have adapted to various marine habitats, evolving diverse thallus morphologies and gamete types. However, the evolutionary processes behind these transitions remain unclear due to a lack of a robust phylogenetic framework and problems with time estimation. To address these issues, we employed plastid genome data from 138 species, including heterokont algae, red algae, and other red-derived algae. Based on a robust phylogeny and new interpretations of algal fossils, we estimated the geological times for brown algal origin and diversification. The results reveal that brown algae first evolved true multicellularity, with plasmodesmata and reproductive cell differentiation, during the late Ordovician Period (ca. 450 Ma), coinciding with a major diversification of marine fauna (the Great Ordovician Biodiversification Event) and a proliferation of multicellular green algae. Despite its early Paleozoic origin, the diversification of major orders within this brown algal clade accelerated only during the Mesozoic Era, coincident with both Pangea rifting and the diversification of other heterokont algae (e.g., diatoms), coccolithophores, and dinoflagellates, with their red algal-derived plastids. The transition from ancestral isogamy to oogamy was followed by three simultaneous reappearances of isogamy during the Cretaceous Period. These are concordant with a positive character correlation between parthenogenesis and isogamy. Our new brown algal timeline, combined with a knowledge of past environmental conditions, shed new light on brown algal diversification and the intertwined evolution of multicellularity and sexual reproduction.
  • Phylotranscriptomic insights into a Mesoproterozoic-Neoproterozoic origin and early radiation of green seaweeds (Ulvophyceae)
    Hou, Zheng; Ma, Xiaoya; Shi, Xuan; Li, Xi; Yang, Lingxiao; Xiao, Shuhai; De Clerck, Olivier; Leliaert, Frederik; Zhong, Bojian (Nature Portfolio, 2022-03-22)
    The Ulvophyceae, a major group of green algae, is of particular evolutionary interest because of its remarkable morphological and ecological diversity. Its phylogenetic relationships and diversification timeline, however, are still not fully resolved. In this study, using an extensive nuclear gene dataset, we apply coalescent- and concatenation-based approaches to reconstruct the phylogeny of the Ulvophyceae and to explore the sources of conflict in previous phylogenomic studies. The Ulvophyceae is recovered as a paraphyletic group, with the Bryopsidales being a sister group to the Chlorophyceae, and the remaining taxa forming a clade (Ulvophyceae sensu stricto). Molecular clock analyses with different calibration strategies emphasize the large impact of fossil calibrations, and indicate a Meso-Neoproterozoic origin of the Ulvophyceae (sensu stricto), earlier than previous estimates. The results imply that ulvophyceans may have had a profound influence on oceanic redox structures and global biogeochemical cycles at the Mesoproterozoic-Neoproterozoic transition.
  • A template for an improved rock-based subdivision of the pre-Cryogenian timescale
    Shields, Graham A.; Strachan, Robin A.; Porter, Susannah M.; Halverson, Galen P.; Macdonald, Francis A.; Plumb, Kenneth A.; de Alvarenga, Carlos J.; Banerjee, Dhiraj M.; Bekker, Andrey; Bleeker, Wouter; Brasier, Alexander; Chakraborty, Partha P.; Collins, Alan S.; Condie, Kent; Das, Kaushik; Evans, David AD D.; Ernst, Richard; Fallick, Anthony E.; Frimmel, Hartwig; Fuck, Reinhardt; Hoffman, Paul F.; Kamber, Balz S.; Kuznetsov, Anton B.; Mitchell, Ross N.; Poire, Daniel G.; Poulton, Simon W.; Riding, Robert; Sharma, Mukund; Storey, Craig; Stueeken, Eva; Tostevin, Rosalie; Turner, Elizabeth; Xiao, Shuhai; Zhang, Shuanhong; Zhou, Ying; Zhu, Maoyan (Geological Society of America, 2021-07-07)
    The geological timescale before 720 Ma uses rounded absolute ages rather than specific events recorded in rocks to subdivide time. This has led increasingly to mismatches between subdivisions and the features for which they were named. Here we review the formal processes that led to the current timescale, outline rock-based concepts that could be used to subdivide pre-Cryogenian time and propose revisions. An appraisal of the Precambrian rock record confirms that purely chronostratigraphic subdivision would require only modest deviation from current chronometric boundaries, removal of which could be expedited by establishing event-based concepts and provisional, approximate ages for eon-, era-and period-level subdivisions. Our review leads to the following conclusions: (1) the current informal four-fold Archean subdivision should be simplified to a tripartite scheme, pending more detailed analysis, and (2) an improved rock-based Proterozoic Eon might comprise a Paleoproterozoic Era with three periods (early Paleoproterozoic or Skourian, Rhyacian, Orosirian), Mesoproterozoic Era with four periods (Statherian, Calymmian, Ectasian, Stenian) and a Neoproterozoic Era with four periods ( pre-Tonian or Kleisian, Tonian, Cryogenian and Ediacaran). These proposals stem from a wide community and could be used to guide future development of the pre-Cryogenian timescale by international bodies.
  • Optimizing Satellite Mission Requirements to Measure Total Suspended Solids in Rivers
    Stroud, Molly K.; Allen, George H.; Simard, Marc; Jensen, Daniel; Gorr, Ben; Selva, Daniel (IEEE, 2023-11-29)
    Human modification of the landscape affects total suspended solid (TSS) concentrations in water. The quantitative extent of these changes remains poorly understood, partly because of the challenges associated with observing TSS dynamics in inland waters over large scales. While many current missions and sensors provide usable data to estimate inland water quality (e.g. Landsat series, VIIRS, and Sentinel-2), future missions present the opportunity to increase transferability and accuracy of TSS estimation. Here, we degrade assumed ideal spectral data to evaluate the optimal data quality for TSS retrieval using an optical sensor configuration. We also perform wavelet analysis and a river size distribution analysis to study temporal and spatial data quantity requirements, respectively. We find that while the highest resolution data always gives the best retrieval accuracy, some factors are more essential in TSS estimation than others and can simplify mission design. Specifically, fine hyperspectral resolution is key in improving retrieval accuracy and a finer spatial resolution allows exponentially more river surface area to be observed. A revisit period of approximately five days or less best captures TSS pulse events, such as floods. Understanding the optimal mission specifications for observing inland water quality, especially TSS, will assist in developing and proposing future optical satellite missions.
  • When does a stream become a river?
    Czuba, Jonathan A.; Allen, George H. (Wiley, 2023-07-13)
    The distinction between a “stream” and “river” is imprecise and vague despite the popular usage of the terms across disciplines for describing flowing waterbodies. Based on an analysis of named flowing waterbodies in the continental United States, we suggest a bank-to-bank channel width of 15 m as a working threshold in defining smaller “streams” from larger “rivers.”.
  • Monte Carlo Simulation of Barrier-Island Systems and Tsunami Hazards
    Irish, Jennifer L.; Weiss, Robert; Dura, Tina (Coastal Engineering Research Council, 2023-09-01)
    Robust characterization of the future tsunami hazard is critically important for resilient planning and engineering in coastal communities prone to tsunami inundation. The hazard from earthquake-generated tsunami waves is not only determined by the earthquake's characteristics and distance to the earthquake area, but also by the geomorphology of the nearshore and onshore areas, which can change over time. In coastal hazard assessments, a changing coastal environment is commonly taken into account by increasing the sea-level to projected values (static). However, sea-level changes and other climate-change impacts influence the entire coastal system causing morphological change (dynamic). Here, we present the modeling framework and results initially published in Weiss et al. (2022), which employs within a Monte Carlo framework the barrier island-marsh, lagoon- marsh evolution model of Lorenzo-Trueba and Mariotti (2017) and the tsunami model Geoclaw (e.g., LeVeque et al. 2011). We compare the runup of the same suite of earthquake-generated tsunamis to a barrier system for statically adjusted and dynamically adjusted sea level and bathymetry over the period from 2000 to 2100. We employ Representative Concentration Pathways 2.6 and 8.5 without and with treatment of Antarctic ice-sheet processes (e.g., Kopp et al. 2017) as different sea-level projections.
  • Real-Time Prediction of Alongshore Near-Field Tsunami Runup Distribution From Heterogeneous Earthquake Slip Distribution
    Lee, Jun-Whan; Irish, Jennifer L.; Weiss, Robert (American Geophysical Union, 2023-01-05)
    Real-time tsunami prediction is necessary for tsunami forecasting. Although tsunami forecasting based on a precomputed tsunami simulation database is fast, it is difficult to respond to earthquakes that are not in the database. As the computation speed increases, various alternatives based on physics-based models have been proposed. However, physics-based models still require several minutes to simulate tsunamis and can have numerical stability issues that potentially make them unreliable for use in forecasting—particularly in the case of near-field tsunamis. This paper presents a data-driven model called the tsunami runup response function for finite faults (TRRF-FF) model that can predict alongshore near-field tsunami runup distribution from heterogeneous earthquake slip distribution in less than a second. Once the TRRF-FF model is trained and calibrated based on a discrete set of tsunami simulations, the TRRF-FF model can predict alongshore tsunami runup distribution from any combination of finite fault parameters. The TRRF-FF model treats the leading-order contribution and the residual part of the alongshore tsunami runup distribution separately. The interaction between finite faults is modeled based on the leading-order alongshore tsunami runup distribution. We validated the TRRF-FF modeling approach with more than 200 synthetic tsunami scenarios in eastern Japan. We further explored the performance of the TRRF-FF model by applying it to the 2011 Tohoku (Japan) tsunami event. The results show that the TRRF-FF model is more flexible, occupies much less storage space than a precomputed tsunami simulation database, and is more rapid and reliable than real-time physics-based numerical simulation.
  • Seismic Sources in the Aleutian Cradle of Tsunamis
    Witter, Rob; Briggs, Rich; Dura, Tina; Engelhart, Simon; Nelson, Alan (2022-10-01)