Description: Due to the intrinsic side-looking geometry of synthetic aperture radar (SAR), time series interferometric SAR is only able to monitor displacements in line-of-sight (LOS) direction, which limits the accuracy of displacement measurement in landslide monitoring. This is because the LOS displacement is only a three dimensional projection of real displacement of a certain ground object. Targeting at this problem, a precise digital elevation model (DEM) assisted slope displacement retrieval method is proposed and applied to a case study over the high and steep slope of the Dagushan open pit mine. In the case study, the precise DEM generated by laser scanning is first used to minimize topographic residuals in small baseline subsets analysis. Then, the LOS displacements are converted to slope direction with assistance of the precise DEM. By comparing with ground measurements, relative root mean square errors (RMSE) of the estimated slope displacements reach approximately 12-13% for the ascending orbit, and 5.4-9.2% for the descending orbit in our study area. In order to validate the experimental results, comparison with microseism monitoring results is also conducted. Moreover, both results have found that the largest slope displacements occur on the slope part, with elevations varying from -138 m to -210 m, which corresponds to the landslide area. Moreover, there is a certain correlation with precipitation, as revealed by the displacement time series. The outcome of this article shows that rock mass structure, lithology, and precipitation are main factors affecting the stability of high and steep mining slopes.

Description: Published

Description: 6674

Description: 7SR AMBIENTE – Servizi e ricerca per la società

Description: JCR Journal

Description: Geological disasters are responsible for the loss of human lives and for significant economic and financial damage every year. Considering that these disasters may occur anywhere—both in remote and/or in highly populated areas—and anytime, continuously monitoring areas known to be more prone to geohazards can help to determine preventive or alert actions to safeguard human life, property and businesses. Remote sensing technology—especially satellite-based—can be of help due to its high spatial and temporal coverage. Indeed, data acquired from the most recent satellite missions is considered suitable for a detailed reconstruction of past events but also to continuously monitor sensitive areas on the lookout for potential geohazards. This work aims to apply different techniques and methods for extensive exploitation and analysis of remote sensing data, with special emphasis given to landslide hazard, risk management and disaster prevention. Multi-temporal SAR (Synthetic Aperture Radar) interferometry, SAR tomography, high-resolution image matching and data modelling are used to map out landslides and other geohazards and to also monitor possible hazardous geological activity, addressing different study areas: (i) surface deformation of mountain slopes and glaciers; (ii) land surface displacement; and (iii) subsidence, landslides and ground fissure. Results from both the processing and analysis of a dataset of earth observation (EO) multi-source data support the conclusion that geohazards can be identified, studied and monitored in an effective way using new techniques applied to multi-source EO data. As future work, the aim is threefold: extend this study to sensitive areas located in different countries; monitor structures that have strategic, cultural and/or economical relevance; and resort to artificial intelligence (AI) techniques to be able to analyse the huge amount of data generated by satellite missions and extract useful information in due course

Description: Published

Description: 4269

Description: 2T. Deformazione crostale attiva

Description: JCR Journal

Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Gu, S., Liu, Z., Oppo, D. W., Lynch-Stieglitz, J., Jahn, A., Zhang, J., & Wu, L. Assessing the potential capability of reconstructing glacial Atlantic water masses and AMOC using multiple proxies in CESM. Earth and Planetary Science Letters, 541, (2020): 11629, doi:10.1016/j.epsl.2020.116294.

Description: Reconstructing the Atlantic Meridional Overturning Circulation (AMOC) during the Last Glacial Maximum (LGM) is essential for understanding glacial-interglacial climate change and the carbon cycle. However, despite many previous studies, uncertainties remain regarding the glacial water mass distributions in the Atlantic and the AMOC intensity. Here we use an isotope enabled ocean model with multiple geotracers (δ 13 C,E Νd,231 Pa/ 230Th,δ 18 Ο and Δ 14 C) and idealized water tracers to study the potential constraints on LGM ocean circulation from multiple proxies. Our model suggests that the glacial Atlantic water mass distribution can be accurately constrained by the air-sea gas exchange signature of water masses (δ13 C AS), but E Nd might overestimate the North Atlantic Deep Water (NADW) percentage in the deep Atlantic probably because of the boundary source of Nd. A sensitivity experiment with an AMOC of similar geometry but much weaker strength suggests that the correct AMOC geometry is more important than the AMOC strength for simulating the observed glacial δ13 C AS and E Nd and distributions. The kinematic tracer 231Pa/230Th is sensitive to AMOC intensity, but the interpretation might be complicated by the AMOC geometry and AABW transport changes during the LGM. δ 18 Ο in the benthic foraminifera (δ 18 Οc) from the Florida Straits provides a consistent measure of the upper ocean boundary current in the model, which potentially provides an unambiguous method to reconstruct glacial AMOC intensity. Finally, we propose that the moderate difference between AMOC intensity at LGM and PD, if any, is caused by the competition of the responses to CO2 forcing and continental ice sheet forcing.

Description: We thank two anonymous reviewers for their useful and constructive comments. We also thank Editor Dr Laura F. Robinson for handling the manuscript. This work is supported by National Science Foundation of China No. 41630527, US National Science Foundation (NSF) P2C2 projects (1401778, 1401802, and 1566432). We would like to acknowledge the high-performance computing support from Yellowstone (ark:/85065/d7wd3xhc) and Cheyenne (doi:10.5065/D6RX99HX) provided by NCAR's Computational and Information Systems Laboratory, sponsored by the National Science Foundation and from Center for High Performance Computing and System Simulation, Pilot National Laboratory for Marine Science and Technology (Qingdao). Data used to produce the results in this study can be obtained from HPSS at CISL: /home/sgu28/CTRACE_decadal or by contacting the authors.

Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Centurioni, L. R., Turton, J., Lumpkin, R., Braasch, L., Brassington, G., Chao, Y., Charpentier, E., Chen, Z., Corlett, G., Dohan, K., Donlon, C., Gallage, C., Hormann, V., Ignatov, A., Ingleby, B., Jensen, R., Kelly-Gerreyn, B. A., Koszalka, I. M., Lin, X., Lindstrom, E., Maximenko, N., Merchant, C. J., Minnett, P., O'Carroll, A., Paluszkiewicz, T., Poli, P., Poulain, P., Reverdin, G., Sun, X., Swail, V., Thurston, S., Wu, L., Yu, L., Wang, B., & Zhang, D. Global in situ observations of essential climate and ocean variables at the air-sea interface. Frontiers in Marine Science, 6, (2019): 419, doi: 10.3389/fmars.2019.00419.

Description: The air–sea interface is a key gateway in the Earth system. It is where the atmosphere sets the ocean in motion, climate/weather-relevant air–sea processes occur, and pollutants (i.e., plastic, anthropogenic carbon dioxide, radioactive/chemical waste) enter the sea. Hence, accurate estimates and forecasts of physical and biogeochemical processes at this interface are critical for sustainable blue economy planning, growth, and disaster mitigation. Such estimates and forecasts rely on accurate and integrated in situ and satellite surface observations. High-impact uses of ocean surface observations of essential ocean/climate variables (EOVs/ECVs) include (1) assimilation into/validation of weather, ocean, and climate forecast models to improve their skill, impact, and value; (2) ocean physics studies (i.e., heat, momentum, freshwater, and biogeochemical air–sea fluxes) to further our understanding and parameterization of air–sea processes; and (3) calibration and validation of satellite ocean products (i.e., currents, temperature, salinity, sea level, ocean color, wind, and waves). We review strengths and limitations, impacts, and sustainability of in situ ocean surface observations of several ECVs and EOVs. We draw a 10-year vision of the global ocean surface observing network for improved synergy and integration with other observing systems (e.g., satellites), for modeling/forecast efforts, and for a better ocean observing governance. The context is both the applications listed above and the guidelines of frameworks such as the Global Ocean Observing System (GOOS) and Global Climate Observing System (GCOS) (both co-sponsored by the Intergovernmental Oceanographic Commission of UNESCO, IOC–UNESCO; the World Meteorological Organization, WMO; the United Nations Environment Programme, UNEP; and the International Science Council, ISC). Networks of multiparametric platforms, such as the global drifter array, offer opportunities for new and improved in situ observations. Advances in sensor technology (e.g., low-cost wave sensors), high-throughput communications, evolving cyberinfrastructures, and data information systems with potential to improve the scope, efficiency, integration, and sustainability of the ocean surface observing system are explored.

Description: LC, LB, and VH were supported by NOAA grant NA15OAR4320071 and ONR grant N00014-17-1-2517. RL was supported by NOAA/AOML and NOAA’s Ocean Observation and Monitoring Division. NM was partly supported by NASA grant NNX17AH43G. IK was supported by the Nordic Seas Eddy Exchanges (NorSEE) funded by the Norwegian Research Council (Grant 221780). DZ was partly funded by the Joint Institute for the Study of the Atmosphere and Ocean (JISAO) under NOAA Cooperative Agreement NA15OAR4320063. RJ was supported by the USACE’s Civil Works 096×3123.

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Gu, S., Liu, Z., Oppo, D. W., Lynch-Stieglitz, J., Jahn, A., Zhang, J., Lindsay, K., & Wu, L. Remineralization dominating the δ13 C decrease in the mid-depth Atlantic during the last deglaciation. Earth and Planetary Science Letters, 571, (2021): 117106, https://doi.org/10.1016/j.epsl.2021.117106.

Description: δ 13 C records from the mid-depth Atlantic show a pronounced decrease during the Heinrich Stadial 1 (HS1), a deglacial episode of dramatically weakened Atlantic Meridional Ocean Circulation (AMOC). Proposed explanations for this mid-depth decrease include a greater fraction of δ 13 C -depleted southern sourced water (SSW), a δ 13 C decrease in the North Atlantic Deep Water (NADW) end-member, and accumulation of the respired organic carbon. However, the relative importance of these proposed mechanisms cannot be quantitatively constrained from current available observations alone. Here we diagnose the individual contributions to the deglacial Atlantic mid-depth δ 13 C change from these mechanisms using a transient simulation with carbon isotopes and idealized tracers. We find that although the fraction of the low- δ 13 C SSW increases in response to a weaker AMOC during HS1, the water mass mixture change only plays a minor role in the mid-depth Atlantic δ 13 C decrease. Instead, increased remineralization due to the AMOC-induced mid-depth ocean ventilation decrease is the dominant cause. In this study, we differentiate between the deep end-members, which are assigned to deep water regions used in previous paleoceanography studies, and the surface end-members, which are from the near-surface water defined from the physical origin of deep water masses. We find that the deep NADW end-member includes additional remineralized material accumulated when sinking from the surface (surface NADW end-member). Therefore, the surface end-members should be used in diagnosing mechanisms of changes. Furthermore, our results suggest that remineralization in the surface end-member is more critical than the remineralization along the transport pathway from the near-surface formation region to the deep ocean, especially during the early deglaciation.

Description: This work is supported by US National Science Foundation (NSF) P2C2 projects (1401778, 1401802, and 1566432), and the National Science Foundation of China No. 41630527. S.G. is supported by Shanghai Pujiang program.

Description: Current climate models systematically underestimate the strength of oceanic fronts associated with strong western boundary currents, such as the Kuroshio and Gulf Stream Extensions, and have difficulty simulating their positions at the mid-latitude ocean’s western boundaries1. Even with an enhanced grid resolution to resolve ocean mesoscale eddies—energetic circulations with horizontal scales of about a hundred kilometres that strongly interact with the fronts and currents—the bias problem can still persist2; to improve climate models we need a better understanding of the dynamics governing these oceanic frontal regimes. Yet prevailing theories about the western boundary fronts are based on ocean internal dynamics without taking into consideration the intense air–sea feedbacks in these oceanic frontal regions. Here, by focusing on the Kuroshio Extension Jet east of Japan as the direct continuation of the Kuroshio, we show that feedback between ocean mesoscale eddies and the atmosphere (OME-A) is fundamental to the dynamics and control of these energetic currents. Suppressing OME-A feedback in eddy-resolving coupled climate model simulations results in a 20–40 per cent weakening in the Kuroshio Extension Jet. This is because OME-A feedback dominates eddy potential energy destruction, which dissipates more than 70 per cent of the eddy potential energy extracted from the Kuroshio Extension Jet. The absence of OME-A feedback inevitably leads to a reduction in eddy potential energy production in order to balance the energy budget, which results in a weakened mean current. The finding has important implications for improving climate models’ representation of major oceanic fronts, which are essential components in the simulation and prediction of extratropical storms and other extreme events3, 4, 5, 6, as well as in the projection of the effect on these events of climate change.

Description: Originating in the equatorial Pacific, the El Niño–Southern Oscillation (ENSO) has highly consequential global impacts, motivating the need to understand its responses to anthropogenic warming. In this Review, we synthesize advances in observed and projected changes of multiple aspects of ENSO, including the processes behind such changes. As in previous syntheses, there is an inter-model consensus of an increase in future ENSO rainfall variability. Now, however, it is apparent that models that best capture key ENSO dynamics also tend to project an increase in future ENSO sea surface temperature variability and, thereby, ENSO magnitude under greenhouse warming, as well as an eastward shift and intensification of ENSO-related atmospheric teleconnections — the Pacific–North American and Pacific–South American patterns. Such projected changes are consistent with palaeoclimate evidence of stronger ENSO variability since the 1950s compared with past centuries. The increase in ENSO variability, though underpinned by increased equatorial Pacific upper-ocean stratification, is strongly influenced by internal variability, raising issues about its quantifiability and detectability. Yet, ongoing coordinated community efforts and computational advances are enabling long-simulation, large-ensemble experiments and high-resolution modelling, offering encouraging prospects for alleviating model biases, incorporating fundamental dynamical processes and reducing uncertainties in projections. Key points Under anthropogenic warming, the majority of climate models project faster background warming in the eastern equatorial Pacific compared with the west. The observed equatorial Pacific surface warming pattern since 1980, though opposite to the projected faster warming in the equatorial eastern Pacific, is within the inter-model range in terms of sea surface temperature (SST) gradients and is subject to influence from internal variability. El Niño–Southern Oscillation (ENSO) rainfall responses in the equatorial Pacific are projected to intensify and shift eastward, leading to an eastward intensification of extratropical teleconnections. ENSO SST variability and extreme ENSO events are projected to increase under greenhouse warming, with a stronger inter-model consensus in CMIP6 compared with CMIP5. However, the time of emergence for ENSO SST variability is later than that for ENSO rainfall variability, opposite to that for mean SST versus mean rainfall. Future ENSO change is likely influenced by past variability, such that quantification of future ENSO in the only realization of the real world is challenging. Although there is no definitive relationship of ENSO variability with the mean zonal SST gradient or seasonal cycle, palaeoclimate records suggest a causal connection between vertical temperature stratification and ENSO strength, and a greater ENSO strength since the 1950s than in past centuries, supporting an emerging increase in ENSO variability under greenhouse warming.