Reviews of Geophysics最新文献

{"title":"Amazon Hydrology From Space: Scientific Advances and Future Challenges","authors":"A. Fassoni-Andrade, A. Fleischmann, F. Papa, R. Paiva, Sly C. Wongchuig, J. Melack, Adriana Aparecida Moreira, A. Paris, A. Ruhoff, C. Barbosa, D. Maciel, E. Novo, F. Durand, F. Frappart, F. Aires, G. Abrahão, Jefferson Ferreira-Ferreira, J. Espinoza, L. Laipelt, M. H. Costa, R. Espinoza-Villar, S. Calmant, V. Pellet","doi":"10.1002/essoar.10506527.1","DOIUrl":"https://doi.org/10.1002/essoar.10506527.1","url":null,"abstract":"As the largest river basin on Earth, the Amazon is of major importance to the world's climate and water resources. Over the past decades, advances in satellite‐based remote sensing (RS) have brought our understanding of its terrestrial water cycle and the associated hydrological processes to a new era. Here, we review major studies and the various techniques using satellite RS in the Amazon. We show how RS played a major role in supporting new research and key findings regarding the Amazon water cycle, and how the region became a laboratory for groundbreaking investigations of new satellite retrievals and analyses. At the basin‐scale, the understanding of several hydrological processes was only possible with the advent of RS observations, such as the characterization of \"rainfall hotspots\" in the Andes‐Amazon transition, evapotranspiration rates, and variations of surface waters and groundwater storage. These results strongly contribute to the recent advances of hydrological models and to our new understanding of the Amazon water budget and aquatic environments. In the context of upcoming hydrology‐oriented satellite missions, which will offer the opportunity for new synergies and new observations with finer space‐time resolution, this review aims to guide future research agenda toward integrated monitoring and understanding of the Amazon water from space. Integrated multidisciplinary studies, fostered by international collaborations, set up future directions to tackle the great challenges the Amazon is currently facing, from climate change to increased anthropogenic pressure.","PeriodicalId":21177,"journal":{"name":"Reviews of Geophysics","volume":"30 1","pages":""},"PeriodicalIF":25.2,"publicationDate":"2021-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81371744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Amazon Hydrology From Space: Scientific Advances and Future Challenges","authors":"Alice César Fassoni-Andrade,&nbsp;Ayan Santos Fleischmann,&nbsp;Fabrice Papa,&nbsp;Rodrigo Cauduro Dias de Paiva,&nbsp;Sly Wongchuig,&nbsp;John M. Melack,&nbsp;Adriana Aparecida Moreira,&nbsp;Adrien Paris,&nbsp;Anderson Ruhoff,&nbsp;Claudio Barbosa,&nbsp;Daniel Andrade Maciel,&nbsp;Evlyn Novo,&nbsp;Fabien Durand,&nbsp;Frédéric Frappart,&nbsp;Filipe Aires,&nbsp;Gabriel Medeiros Abrah?o,&nbsp;Jefferson Ferreira-Ferreira,&nbsp;Jhan Carlo Espinoza,&nbsp;Leonardo Laipelt,&nbsp;Marcos Heil Costa,&nbsp;Raul Espinoza-Villar,&nbsp;Stéphane Calmant,&nbsp;Victor Pellet","doi":"10.1029/2020RG000728","DOIUrl":"https://doi.org/10.1029/2020RG000728","url":null,"abstract":"<p>As the largest river basin on Earth, the Amazon is of major importance to the world's climate and water resources. Over the past decades, advances in satellite-based remote sensing (RS) have brought our understanding of its terrestrial water cycle and the associated hydrological processes to a new era. Here, we review major studies and the various techniques using satellite RS in the Amazon. We show how RS played a major role in supporting new research and key findings regarding the Amazon water cycle, and how the region became a laboratory for groundbreaking investigations of new satellite retrievals and analyses. At the basin-scale, the understanding of several hydrological processes was only possible with the advent of RS observations, such as the characterization of \"rainfall hotspots\" in the Andes-Amazon transition, evapotranspiration rates, and variations of surface waters and groundwater storage. These results strongly contribute to the recent advances of hydrological models and to our new understanding of the Amazon water budget and aquatic environments. In the context of upcoming hydrology-oriented satellite missions, which will offer the opportunity for new synergies and new observations with finer space-time resolution, this review aims to guide future research agenda toward integrated monitoring and understanding of the Amazon water from space. Integrated multidisciplinary studies, fostered by international collaborations, set up future directions to tackle the great challenges the Amazon is currently facing, from climate change to increased anthropogenic pressure.</p>","PeriodicalId":21177,"journal":{"name":"Reviews of Geophysics","volume":"59 4","pages":""},"PeriodicalIF":25.2,"publicationDate":"2021-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2020RG000728","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"6202859","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Late Quaternary Abrupt Climate Change in the Tropics and Sub-Tropics: The Continental Signal of Tropical Hydroclimatic Events (THEs)","authors":"Raymond S. Bradley,&nbsp;Henry F. Diaz","doi":"10.1029/2020RG000732","DOIUrl":"https://doi.org/10.1029/2020RG000732","url":null,"abstract":"<p><b>Tropical hydroclimatic events</b>, characterized by extreme regional rainfall anomalies, were a recurrent feature of marine isotope stages 2–4 and involved some of the most abrupt and dramatic climatic changes in the late Quaternary. These anomalies were pervasive throughout the tropics and resulted from the southward displacement of the Hadley circulation and the Intertropical Convergence Zone (ITCZ) and its associated convective rainfall, modulated by regional factors. Lake sediments, stalagmites, and offshore marine sediments that integrate inland continental conditions provide a comprehensive record of these changes over the past ∼70,000 yr. Vast areas experienced severe drought while other areas recorded greatly increased rainfall. Within the uncertainties of dating, these tropical rainfall anomalies occurred very close in time (±10²–10³ yr) to the deposition of North Atlantic ice-rafted debris (IRD) that defines Heinrich events (HEs). The IRD record is a good proxy for the amount and distribution of additional freshwater forcing which was necessary to bring about a drastic reduction in the Atlantic Meridional Overturning Circulation (AMOC) strength during each HE. As a consequence of this reduction in AMOC and an abrupt expansion in the area of sea-ice, cooling of the North Atlantic and adjacent continents took place, with a rapid atmospheric response involving the southward displacement of the ITCZ and associated rainfall belts. The climatic consequences of this large-scale change in the Hadley circulation, modulated by regional factors, is clearly recorded throughout the tropics as a series of abrupt and extreme hydroclimatic events. Some of the physical mechanisms that may have played a role in those changes are discussed.</p>","PeriodicalId":21177,"journal":{"name":"Reviews of Geophysics","volume":"59 4","pages":""},"PeriodicalIF":25.2,"publicationDate":"2021-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2020RG000732","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"6072902","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Origin, Accretion, and Reworking of Continents","authors":"Rixiang Zhu,&nbsp;Guochun Zhao,&nbsp;Wenjiao Xiao,&nbsp;Ling Chen,&nbsp;Yanjie Tang","doi":"10.1029/2019RG000689","DOIUrl":"https://doi.org/10.1029/2019RG000689","url":null,"abstract":"<p>The continental crust is unique to the Earth in the solar system, and controversies remain regarding its origin, accretion and reworking of continents. The plate tectonics theory has been significantly challenged in explaining the origin of Archean (especially pre-3.0 Ga) continents as they rarely preserve hallmarks of plate tectonics. In contrast, growing evidence emerges to support oceanic plateau models that better explain characteristics of Archean continents, including the bimodal volcanics and nearly coeval emplacement of tonalite-trondjhemite-granodiorite (TTG) rocks, presence of ∼1600°C komatiites and dominant dome structures, and lack of ultra-high-pressure rocks, paired metamorphic belts and ophiolites. On the other hand, the theory of plate tectonics has been successfully applied to interpret the accretion of continents along subduction zones since the late Archean (3.0–2.5 Ga). During subduction processes, the new mafic crust is generated at the base of continents through partial melting of mantle wedge with the addition of H₂O-dominant fluids from subducted oceanic slabs and partial melting of the juvenile mafic crust results in the generation of new felsic crusts. This eventually leads to the outgrowth of continents. Subduction processes also cause softening, thinning, and recycling of continental lithosphere due to the vigorous infiltration of volatile-rich fluids and melts, especially along weak belts/layers, leading to widespread continental reworking and even craton destruction. Reworking of continents also occurs in continental interiors due to either plate boundary processes or plume-lithosphere interactions. The effects of plumes have proven to be less significant and cause lower degrees of lithospheric modification than subduction-induced craton destruction.</p>","PeriodicalId":21177,"journal":{"name":"Reviews of Geophysics","volume":"59 3","pages":""},"PeriodicalIF":25.2,"publicationDate":"2021-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2019RG000689","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5677212","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Reanalysis in Earth System Science: Toward Terrestrial Ecosystem Reanalysis","authors":"R. Baatz,&nbsp;H. J. Hendricks Franssen,&nbsp;E. Euskirchen,&nbsp;D. Sihi,&nbsp;M. Dietze,&nbsp;S. Ciavatta,&nbsp;K. Fennel,&nbsp;H. Beck,&nbsp;G. De Lannoy,&nbsp;V. R. N. Pauwels,&nbsp;A. Raiho,&nbsp;C. Montzka,&nbsp;M. Williams,&nbsp;U. Mishra,&nbsp;C. Poppe,&nbsp;S. Zacharias,&nbsp;A. Lausch,&nbsp;L. Samaniego,&nbsp;K. Van Looy,&nbsp;H. Bogena,&nbsp;M. Adamescu,&nbsp;M. Mirtl,&nbsp;A. Fox,&nbsp;K. Goergen,&nbsp;B. S. Naz,&nbsp;Y. Zeng,&nbsp;H. Vereecken","doi":"10.1029/2020RG000715","DOIUrl":"https://doi.org/10.1029/2020RG000715","url":null,"abstract":"<p>A reanalysis is a physically consistent set of optimally merged simulated model states and historical observational data, using data assimilation. High computational costs for modeled processes and assimilation algorithms has led to Earth system specific reanalysis products for the atmosphere, the ocean and the land separately. Recent developments include the advanced uncertainty quantification and the generation of biogeochemical reanalysis for land and ocean. Here, we review atmospheric and oceanic reanalyzes, and more in detail biogeochemical ocean and terrestrial reanalyzes. In particular, we identify land surface, hydrologic and carbon cycle reanalyzes which are nowadays produced in targeted projects for very specific purposes. Although a future joint reanalysis of land surface, hydrologic, and carbon processes represents an analysis of important ecosystem variables, biotic ecosystem variables are assimilated only to a very limited extent. Continuous data sets of ecosystem variables are needed to explore biotic-abiotic interactions and the response of ecosystems to global change. Based on the review of existing achievements, we identify five major steps required to develop terrestrial ecosystem reanalysis to deliver continuous data streams on ecosystem dynamics.</p>","PeriodicalId":21177,"journal":{"name":"Reviews of Geophysics","volume":"59 3","pages":""},"PeriodicalIF":25.2,"publicationDate":"2021-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2020RG000715","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"6109191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Structures and Deformation in Glaciers and Ice Sheets","authors":"Stephen J. A. Jennings,&nbsp;Michael J. Hambrey","doi":"10.1029/2021RG000743","DOIUrl":"https://doi.org/10.1029/2021RG000743","url":null,"abstract":"<p>The aims of this review are to: (a) describe and interpret structures in valley glaciers in relation to strain history; and (b) to explore how these structures inform our understanding of the kinematics of large ice masses, and a wide range of other aspects of glaciology. Structures in glaciers give insight as to how ice deforms at the macroscopic and larger scale. Structures also provide information concerning the deformation history of ice masses over centuries and millennia. From a geological perspective, glaciers can be considered to be models of rock deformation, but with rates of change that are measurable on a human time-scale. However, structural assemblages in glaciers are commonly complex, and unraveling them to determine the deformation history is challenging; it thus requires the approach of the structural geologist. A wide range of structures are present in valley glaciers: (a) primary structures include sedimentary stratification and various veins; (b) secondary structures that are the result of brittle and ductile deformation include crevasses, faults, crevasse traces, foliation, folds, and boudinage structures. Some of these structures, notably crevasses, relate well to measured strain-rates, but to explain ductile structures analysis of cumulative strain is required. Some structures occur in all glaciers irrespective of size, and they are therefore recognizable in ice streams and ice shelves. Structural approaches have wide (but as yet under-developed potential) application to other sub-disciplines of glaciology, notably glacier hydrology, debris entrainment and transfer, landform development, microbiological investigations, and in the interpretation of glacier-like features on Mars.</p>","PeriodicalId":21177,"journal":{"name":"Reviews of Geophysics","volume":"59 3","pages":""},"PeriodicalIF":25.2,"publicationDate":"2021-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2021RG000743","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5822648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Deep Learning for Geophysics: Current and Future Trends","authors":"Siwei Yu,&nbsp;Jianwei Ma","doi":"10.1029/2021RG000742","DOIUrl":"https://doi.org/10.1029/2021RG000742","url":null,"abstract":"<p>Recently deep learning (DL), as a new data-driven technique compared to conventional approaches, has attracted increasing attention in geophysical community, resulting in many opportunities and challenges. DL was proven to have the potential to predict complex system states accurately and relieve the “curse of dimensionality” in large temporal and spatial geophysical applications. We address the basic concepts, state-of-the-art literature, and future trends by reviewing DL approaches in various geosciences scenarios. Exploration geophysics, earthquakes, and remote sensing are the main focuses. More applications, including Earth structure, water resources, atmospheric science, and space science, are also reviewed. Additionally, the difficulties of applying DL in the geophysical community are discussed. The trends of DL in geophysics in recent years are analyzed. Several promising directions are provided for future research involving DL in geophysics, such as unsupervised learning, transfer learning, multimodal DL, federated learning, uncertainty estimation, and active learning. A coding tutorial and a summary of tips for rapidly exploring DL are presented for beginners and interested readers of geophysics.</p>","PeriodicalId":21177,"journal":{"name":"Reviews of Geophysics","volume":"59 3","pages":""},"PeriodicalIF":25.2,"publicationDate":"2021-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2021RG000742","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5683520","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Impacts of Ionospheric Ions on Magnetic Reconnection and Earth's Magnetosphere Dynamics","authors":"S. Toledo-Redondo,&nbsp;M. André,&nbsp;N. Aunai,&nbsp;C. R. Chappell,&nbsp;J. Dargent,&nbsp;S. A. Fuselier,&nbsp;A. Glocer,&nbsp;D. B. Graham,&nbsp;S. Haaland,&nbsp;M. Hesse,&nbsp;L. M. Kistler,&nbsp;B. Lavraud,&nbsp;W. Li,&nbsp;T. E. Moore,&nbsp;P. Tenfjord,&nbsp;S. K. Vines","doi":"10.1029/2020RG000707","DOIUrl":"https://doi.org/10.1029/2020RG000707","url":null,"abstract":"<p>Ionospheric ions (mainly H⁺, He⁺, and O⁺) escape from the ionosphere and populate the Earth's magnetosphere. Their thermal energies are usually low when they first escape the ionosphere, typically a few electron volt to tens of electron volt, but they are energized in their journey through the magnetosphere. The ionospheric population is variable, and it makes significant contributions to the magnetospheric mass density in key regions where magnetic reconnection is at work. Solar wind—magnetosphere coupling occurs primarily via magnetic reconnection, a key plasma process that enables transfer of mass and energy into the near-Earth space environment. Reconnection leads to the triggering of magnetospheric storms, auroras, energetic particle precipitation and a host of other magnetospheric phenomena. Several works in the last decades have attempted to statistically quantify the amount of ionospheric plasma supplied to the magnetosphere, including the two key regions where magnetic reconnection occurs: the dayside magnetopause and the magnetotail. Recent in situ observations by the Magnetospheric Multiscale spacecraft and associated modeling have advanced our current understanding of how ionospheric ions alter the magnetic reconnection process, including its onset and efficiency. This article compiles the current understanding of the ionospheric plasma supply to the magnetosphere. It reviews both the quantification of these sources and their effects on the process of magnetic reconnection. It also provides a global description of how the ionospheric ion contribution modifies the way the solar wind couples to the Earth's magnetosphere and how these ions modify the global dynamics of the near-Earth space environment.</p>","PeriodicalId":21177,"journal":{"name":"Reviews of Geophysics","volume":"59 3","pages":""},"PeriodicalIF":25.2,"publicationDate":"2021-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2020RG000707","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"6059199","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"On the Cause of the Mid-Pleistocene Transition","authors":"C. J. Berends,&nbsp;P. K?hler,&nbsp;L. J. Lourens,&nbsp;R. S. W. van de Wal","doi":"10.1029/2020RG000727","DOIUrl":"https://doi.org/10.1029/2020RG000727","url":null,"abstract":"<p>The Mid-Pleistocene Transition (MPT), where the Pleistocene glacial cycles changed from 41 to ∼100 kyr periodicity, is one of the most intriguing unsolved issues in the field of paleoclimatology. Over the course of over four decades of research, several different physical mechanisms have been proposed to explain the MPT, involving non-linear feedbacks between ice sheets and the global climate, the solid Earth, ocean circulation, and the carbon cycle. Here, we review these different mechanisms, comparing how each of them relates to the others, and to the currently available observational evidence. Based on this discussion, we identify the most important gaps in our current understanding of the MPT. We discuss how new model experiments, which focus on the quantitative differences between the different physical mechanisms, could help fill these gaps. The results of those experiments could help interpret available proxy evidence, as well as new evidence that is expected to become available.</p>","PeriodicalId":21177,"journal":{"name":"Reviews of Geophysics","volume":"59 2","pages":""},"PeriodicalIF":25.2,"publicationDate":"2021-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2020RG000727","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5760815","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"The Scientific Legacy of NASA’s Operation IceBridge","authors":"Joseph A. MacGregor,&nbsp;Linette N. Boisvert,&nbsp;Brooke Medley,&nbsp;Alek A. Petty,&nbsp;Jeremy P. Harbeck,&nbsp;Robin E. Bell,&nbsp;J. Bryan Blair,&nbsp;Edward Blanchard-Wrigglesworth,&nbsp;Ellen M. Buckley,&nbsp;Michael S. Christoffersen,&nbsp;James R. Cochran,&nbsp;Beáta M. Csathó,&nbsp;Eugenia L. De Marco,&nbsp;RoseAnne T. Dominguez,&nbsp;Mark A. Fahnestock,&nbsp;Sinéad L. Farrell,&nbsp;S. Prasad Gogineni,&nbsp;Jamin S. Greenbaum,&nbsp;Christy M. Hansen,&nbsp;Michelle A. Hofton,&nbsp;John W. Holt,&nbsp;Kenneth C. Jezek,&nbsp;Lora S. Koenig,&nbsp;Nathan T. Kurtz,&nbsp;Ronald Kwok,&nbsp;Christopher F. Larsen,&nbsp;Carlton J. Leuschen,&nbsp;Caitlin D. Locke,&nbsp;Serdar S. Manizade,&nbsp;Seelye Martin,&nbsp;Thomas A. Neumann,&nbsp;Sophie M.J. Nowicki,&nbsp;John D. Paden,&nbsp;Jacqueline A. Richter-Menge,&nbsp;Eric J. Rignot,&nbsp;Fernando Rodríguez-Morales,&nbsp;Matthew R. Siegfried,&nbsp;Benjamin E. Smith,&nbsp;John G. Sonntag,&nbsp;Michael Studinger,&nbsp;Kirsty J. Tinto,&nbsp;Martin Truffer,&nbsp;Thomas P. Wagner,&nbsp;John E. Woods,&nbsp;Duncan A. Young,&nbsp;James K. Yungel","doi":"10.1029/2020RG000712","DOIUrl":"https://doi.org/10.1029/2020RG000712","url":null,"abstract":"<p>The National Aeronautics and Space Administration (NASA)’s Operation IceBridge (OIB) was a 13-year (2009–2021) airborne mission to survey land and sea ice across the Arctic, Antarctic, and Alaska. Here, we review OIB’s goals, instruments, campaigns, key scientific results, and implications for future investigations of the cryosphere. OIB’s primary goal was to use airborne laser altimetry to bridge the gap in fine-resolution elevation measurements of ice from space between the conclusion of NASA’s Ice, Cloud, and land Elevation Satellite (ICESat; 2003–2009) and its follow-on, ICESat-2 (launched 2018). Additional scientific requirements were intended to contextualize observed elevation changes using a multisensor suite of radar sounders, gravimeters, magnetometers, and cameras. Using 15 different aircraft, OIB conducted 968 science flights, of which 42% were repeat surveys of land ice, 42% were surveys of previously unmapped terrain across the Greenland and Antarctic ice sheets, Arctic ice caps, and Alaskan glaciers, and 16% were surveys of sea ice. The combination of an expansive instrument suite and breadth of surveys enabled numerous fundamental advances in our understanding of the Earth’s cryosphere. For land ice, OIB dramatically improved knowledge of interannual outlet-glacier variability, ice-sheet, and outlet-glacier thicknesses, snowfall rates on ice sheets, fjord and sub-ice-shelf bathymetry, and ice-sheet hydrology. Unanticipated discoveries included a reliable method for constraining the thickness within difficult-to-sound incised troughs beneath ice sheets, the extent of the firn aquifer within the Greenland Ice Sheet, the vulnerability of many Greenland and Antarctic outlet glaciers to ocean-driven melting at their grounding zones, and the dominance of surface-melt-driven mass loss of Alaskan glaciers. For sea ice, OIB significantly advanced our understanding of spatiotemporal variability in sea ice freeboard and its snow cover, especially through combined analysis of fine-resolution altimetry, visible imagery, and snow radar measurements of the overlying snow thickness. Such analyses led to the unanticipated discovery of an interdecadal decrease in snow thickness on Arctic sea ice and numerous opportunities to validate sea ice freeboards from satellite radar altimetry. While many of its data sets have yet to be fully explored, OIB’s scientific legacy has already demonstrated the value of sustained investment in reliable airborne platforms, airborne instrument development, interagency and international collaboration, and open and rapid data access to advance our understanding of Earth’s remote polar regions and their role in the Earth system.</p>","PeriodicalId":21177,"journal":{"name":"Reviews of Geophysics","volume":"59 2","pages":""},"PeriodicalIF":25.2,"publicationDate":"2021-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2020RG000712","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5687515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}