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  • Institute of Physics  (47,869)
  • American Geophysical Union  (13,575)
  • American Association for the Advancement of Science (AAAS)  (10,831)
  • International Union of Crystallography (IUCr)
  • 2020-2024  (491)
  • 1980-1984  (68,509)
  • 1955-1959  (8,776)
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  • 1
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    Skillful long-lead prediction of summertime heavy rainfall in the US Midwest from sea surface salinity (2022)
    American Geophysical Union
    Details
    Publication Date: 2023-01-07
    Description: Author Posting. © American Geophysical Union, 2022. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 49(13), (2022): e2022GL098554, https://doi.org/10.1029/2022GL098554.
    Description: Summertime heavy rainfall and its resultant floods are among the most harmful natural hazards in the US Midwest, one of the world's primary crop production areas. However, seasonal forecasts of heavy rain, currently based on preseason sea surface temperature anomalies (SSTAs), remain unsatisfactory. Here, we present evidence that sea surface salinity anomalies (SSSAs) over the tropical western Pacific and subtropical North Atlantic are skillful predictors of summer time heavy rainfall one season ahead. A one standard deviation change in tropical western Pacific SSSA is associated with a 1.8 mm day−1 increase in local precipitation, which excites a teleconnection pattern to extratropical North Pacific. Via extratropical air-sea interaction and long memory of midlatitude SSTA, a wave train favorable for US Midwest heavy rain is induced. Combined with soil moisture feedbacks bridging the springtime North Atlantic salinity, the SSSA-based statistical prediction model improves Midwest heavy rainfall forecasts by 92%, complementing existing SSTA-based frameworks.
    Description: This study is supported by the NSF PREEVENTS program under ICER-1663138 (LL) and ICER-1663704 (RWS and CCU).
    Description: 2023-01-07
    Keywords: Sea surface salinity ; Midwest precipitation ; Heavy rainfall ; Long-lead prediction
    Repository Name: Woods Hole Open Access Server
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  • 2
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    Contributions of different sea-level processes to high-tide flooding along the US coastline (2022)
    American Geophysical Union
    Details
    Publication Date: 2023-01-14
    Description: Author Posting. © American Geophysical Union, 2022. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 127(7), (2022): e2021JC018276, https://doi.org/10.1029/2021JC018276.
    Description: Coastal communities across the United States (U.S.) are experiencing an increase in the frequency of high-tide flooding (HTF). This increase is mainly due to sea-level rise (SLR), but other factors such as intra- to inter-annual mean sea level variability, tidal anomalies, and non-tidal residuals also contribute to HTF events. Here we introduce a novel decomposition approach to develop and then analyze a new database of different sea-level components. Those components represent processes that act on various timescales to contribute to HTF along the U.S. coastline. We find that the relative importance of components to HTF events strongly varies in space and time. Tidal anomalies contribute the most along the west and northeast coasts, where HTF events mostly occur in winter. Non-tidal residuals are most important along the Gulf of Mexico and mid-Atlantic coasts, where HTF events mostly occur in fall. We also quantify the minimum number of components that were required to cause HTF events in the past and how this number changed over time. The results highlight that at present, due to SLR, fewer components are needed to combine to push water levels above HTF thresholds, but tidal anomalies alone are still not sufficient to reach HTF thresholds in most locations. Finally, we explore how co-variability between different components leads to compounding effects. In some places, positive correlation between sea-level components leads to significantly more HTF events than would be expected if sea-level components were uncorrelated, whereas in other places negative correlation leads to fewer HTF events.
    Description: his work was supported by NASA's Sea Level Change Team award number 80NSSC20K1241. S.L. also acknowledges support by the China Scholarship Council (no. 201904910413) and the Ministry of Science and Technology of the People's Republic of China (grant no. 2011YQ120045).
    Description: 2023-01-14
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  • 3
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    Driving forces of Antarctic krill abundance (2023)
    American Association for the Advancement of Science (AAAS)
    In:  EPIC3Science Advances, American Association for the Advancement of Science (AAAS), 9(50), ISSN: 2375-2548
    Details
    Publication Date: 2023-12-18
    Description: Antarctic krill, crucial to the Southern Ocean ecosystem and a vital fisheries resource, is endangered by climate change. Identifying drivers of krill biomass is therefore essential for determining catch limits and designating protection zones. We present a modeling approach to pinpointing effects of sea surface temperature, ice cover, chlorophyll levels, climate indices, and intraspecific competition. Our study reveals that larval recruitment is driven by both competition among age classes and chlorophyll levels. In addition, while milder ice and temperature in spring and summer favor reproduction and early larval survival, both larvae and juveniles strongly benefit from heavier ice and colder temperatures in winter. We conclude that omitting top-down control of resources by krill is only acceptable for retrospective or single-year prognostic models that use field chlorophyll data but that incorporating intraspecific competition is essential for longer-term forecasts. Our findings can guide future krill modeling strategies, reinforcing the sustainability of this keystone species.
    Repository Name: EPIC Alfred Wegener Institut
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  • 4
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    Seismic imaging of Dante’s Domes oceanic core complex from streamer waveform inversion and reverse time migration (2023)
    American Geophysical Union
    Details
    Publication Date: 2023-02-25
    Description: Author Posting. © American Geophysical Union, 2022. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 127(8), (2022): e2021JB023814, https://doi.org/10.1029/2021jb023814.
    Description: Early arrival traveltime tomography and full waveform inversion were conducted on downward continued streamer seismic data at Dante's Domes oceanic core complex (OCC), providing unprecedented details of shallow P wave velocity structure. Together with reverse time migration images, seafloor morphology, in situ geological samples, magnetic and gravity data, the seismic constraints are used to infer the lithological distribution along the seismic profiles. Based on the striking similarity in velocity structure beneath the corrugated domes with other OCCs and drilling results from Atlantis Massif, we confidently reconfirmed the Southern Dome as dominantly gabbroic rocks, and the Northern Dome as serpentinized peridotites. A series of isolated gabbroic bodies embedded in the diabase and basaltic layers is observed in the breakaway zone, suggesting that the initiation of Dante's Domes OCC occurred over a long period during which there were several failed attempts to form a long-lived detachment fault. This early development of the OCC probably occurred under a regime of alternating magma starvation and magma replenishment. The predominantly gabbroic section, beneath the Southern Dome and extending to termination, indicates the OCC has been created with relatively high magma flux. We also imaged distinct shallow subseafloor reflections which are also termed as D reflectors underneath the corrugated domes. The location of the D reflectors is similar to those in the Atlantis Massif, with depths well correlated with the top of exhumed gabbroic bodies and the discontinuities in the D reflectors between gabbroic bodies. Our findings contribute to the understanding of processes controlling the OCCs initiation and evolution at slow spreading ridges.
    Description: This research was supported by the National Natural Science Foundation of China (91858207), Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (GML2019ZD0205), and Guangdong Basic and Applied Basic Research Foundation (2021B1515020023). M. X. acknowledges support from Special Foundation for National Science and Technology Basic Research Program of China (2018FY100505), Guangdong NSF research team project (2017A030312002), K. C. Wong Education Foundation (GJTD-2018-13), and the Chinese Academy of Sciences (Y4SL021001, QYZDY-SSWDQC005, 133244KYSB20180029, 131551KYSB20200021, and ISEE2021PY03). J. P. C. acknowledges support from the Independent Research and Development Program at WHOI.
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  • 5
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    Spatial variability of movement, structure, and formation of Warm Core Rings in the Northwest Atlantic Slope Sea (2023)
    American Geophysical Union
    Details
    Publication Date: 2023-02-25
    Description: Author Posting. © American Geophysical Union, 2022. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 127(8),(2022): e2022JC018737, https://doi.org/10.1029/2022jc018737.
    Description: Gulf Stream Warm Core Rings (WCRs) have important influences on the New England Shelf and marine ecosystems. A 10-year (2011–2020) WCR dataset that tracks weekly WCR locations and surface areas is used here to identify the rings' path and characterize their movement between 55 and 75°W. The WCR dataset reveals a very narrow band between 66 and 71°W along which rings travel almost due west along ∼39°N across isobaths – the “Ring Corridor.” Then, west of the corridor, the mean path turns southwestward, paralleling the shelfbreak. The average ring translation speed along the mean path is 5.9 cm s−1. Long-lived rings (lifespan 〉150 days) tend to occupy the region west of the New England Seamount Chain (NESC) whereas short-lived rings (lifespan 〈150 days) tend to be more broadly distributed. WCR vertical structures, analyzed using available Argo float profiles indicate that rings that are formed to the west of the NESC have shallower thermoclines than those formed to the east. This tendency may be due to different WCR formation processes that are observed to occur along different sections of the Gulf Stream. WCRs formed to the east of the NESC tend to form from a pinch-off mechanism incorporating cores of Sargasso Sea water and a perimeter of Gulf Stream water. WCRs that form to the west of the NESC, form from a process called an aneurysm. WCRs formed through aneurysms comprise water mostly from the northern half of the Gulf Stream and are smaller than the classic pinch-off rings.
    Description: AS and AG are grateful for financial support from NOAA (NA11NOS0120038), NSF (OCE-1851242 and OCE-2123283), SMAST, and UMass Dartmouth. GG was supported by NSF under grant OCE-1657853. MA was supported by NSF under grant OCE-2122726 and by ONR under grant N00014-22-1-2112.
    Keywords: Gulf Stream ; Warm core rings ; Trajectories ; Eddies ; Aneurysm ; Ring formation
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  • 6
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    Eruption rates, tempo, and stratigraphy of Paleocene flood basalts on Baffin Island, Canada (2023)
    American Geophysical Union
    Details
    Publication Date: 2023-02-25
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Biasi, J., Asimow, P., Horton, F., & Boyes, X. Eruption rates, tempo, and stratigraphy of Paleocene flood basalts on Baffin Island, Canada. Geochemistry, Geophysics, Geosystems, 23(9), (2022): e2021GC010172, https://doi.org/10.1029/2021gc010172.
    Description: High-temperature melting in mantle plumes produces voluminous eruptions that are often temporally coincident with mass extinctions. Paleocene Baffin Island lavas—products of early Iceland mantle plume activity—are exceptionally well characterized geochemically but have poorly constrained stratigraphy, geochronology, and eruptive tempos. To provide better geologic context, we measured seven stratigraphic sections of the volcanic deposits and collected paleomagnetic data from 38 sites in the lavas and underlying Cretaceous sediments (Quqaluit Fm.). The average paleomagnetic pole from this study does not overlap with the expected pole for a stable North American locality at 60 Ma, yet the data have sufficient dispersion to average out secular variation. After ruling out other possibilities, we find that the picrites were probably erupted during a polarity transition, over less than 5 kyr. If so, the average eruption interval was ∼67 years per flow for the thickest sequence of exposed lavas. We also calculate that the flood basalts had a minimum total volume of ∼176 km3 (excluding submerged lavas in Baffin Bay). This implies a minimum eruption rate of ∼0.035 km3 yr−1, which is similar to rates found in West Greenland lavas but less than rates found in larger flood basalts. Despite this, the Baffin and West Greenland lavas temporally correlate with the “End C27n event” (a period of ∼2°C global warming) and may be its underlying cause.
    Description: his work was supported by the National Science Foundation (award #1911699 to F. Horton and award #2052963 to J. Biasi), Woods Hole Oceanographic Institution (WHOI) Andrew W. Mellon Foundation Endowed Fund for Innovative Research, a National Geographic Society grant (#CP4-144R-18), and internal funding from the Caltech Geological and Planetary Sciences Division.
    Keywords: Baffin island ; North Atlantic ; Flood basalt ; Paleomagnetism ; Volcanology ; Secular variation
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  • 7
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    Carbonation of serpentinite in creeping faults of California (2023)
    American Geophysical Union
    Details
    Publication Date: 2023-02-21
    Description: Author Posting. © American Geophysical Union, 2022. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 49(15), (2022): e2022GL099185, https://doi.org/10.1029/2022gl099185.
    Description: Several large strike slip faults in central and northern California accommodate plate motions through aseismic creep. Although there is no consensus regarding the underlying cause of aseismic creep, aqueous fluids and mechanically weak, velocity-strengthening minerals appear to play a central role. This study integrates field observations and thermodynamic modeling to examine possible relationships between the occurrence of serpentinite, silica-carbonate rock, and CO2-rich aqueous fluids in creeping faults of California. Our models predict that carbonation of serpentinite leads to the formation of talc and magnesite, followed by silica-carbonate rock. While abundant exposures of silica-carbonate rock indicate complete carbonation, serpentinite-hosted CO2-rich spring fluids are strongly supersaturated with talc at elevated temperatures. Hence, carbonation of serpentinite is likely ongoing in parts of the San Andres Fault system and operates in conjunction with other modes of talc formation that may further enhance the potential for aseismic creep, thereby limiting the potential for large earthquakes.
    Description: This work was supported by National Science Foundation (NSF) grants NSF-EAR-1220280 to F. K. and J. L., NSF-EAR-1219908 to D. G., and NSF-OCE-2001728 to J. L.
    Keywords: Mineral carbonation ; Serpentinite ; Talc ; CO2 ; Aseismic creep ; San Andreas Fault
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  • 8
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    Does sea spray aerosol contribute significantly to aerosol trace element loading? a case study from the US GEOTRACES Pacific Meridional Transect (GP15) (2023)
    American Geophysical Union
    Details
    Publication Date: 2023-02-21
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Marsay, C. M., Landing, W. M., Umstead, D., Till, C. P., Freiberger, R., Fitzsimmons, J. N., Lanning, N. T., Shiller, A. M., Hatta, M., Chmiel, R., Saito, M., & Buck, C. S. Does sea spray aerosol contribute significantly to aerosol trace element loading? a case study from the US GEOTRACES Pacific Meridional Transect (GP15). Global Biogeochemical Cycles, 36(8), (2022): e2022GB007416. https://doi.org/10.1029/2022GB007416.
    Description: Atmospheric deposition represents a major input for micronutrient trace elements (TEs) to the surface ocean and is often quantified indirectly through measurements of aerosol TE concentrations. Sea spray aerosol (SSA) dominates aerosol mass concentration over much of the global ocean, but few studies have assessed its contribution to aerosol TE loading, which could result in overestimates of “new” TE inputs. Low-mineral aerosol concentrations measured during the U.S. GEOTRACES Pacific Meridional Transect (GP15; 152°W, 56°N to 20°S), along with concurrent towfish sampling of surface seawater, provided an opportunity to investigate this aspect of TE biogeochemical cycling. Central Pacific Ocean surface seawater Al, V, Mn, Fe, Co, Ni, Cu, Zn, and Pb concentrations were combined with aerosol Na data to calculate a “recycled” SSA contribution to aerosol TE loading. Only vanadium was calculated to have a SSA contribution averaging 〉1% along the transect (mean of 1.5%). We derive scaling factors from previous studies on TE enrichments in the sea surface microlayer and in freshly produced SSA to assess the broader potential for SSA contributions to aerosol TE loading. Maximum applied scaling factors suggest that SSA could contribute significantly to the aerosol loading of some elements (notably V, Cu, and Pb), while for others (e.g., Fe and Al), SSA contributions largely remained 〈1%. Our study highlights that a lack of focused measurements of TEs in SSA limits our ability to quantify this component of marine aerosol loading and the associated potential for overestimating new TE inputs from atmospheric deposition.
    Description: This research was supported by the National Science Foundation (NSF) grants OCE-1756103 to C. S. Buck, OCE-1756104 to W. M. Landing, OCE-1737024 to A.M. Shiller, OCE-1736906 to M. Hatta, OCE-1736875 to C. P. Till, OCE-1737167 to J. N. Fitzsimmons, and OCE-1736599 to M. Saito. In addition, N. T. Lanning was supported by the NSF Graduate Research Fellowship Program award 1746932.
    Keywords: Aerosols ; Trace elements ; GEOTRACES ; Sea spray aerosol ; Pacific Ocean
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  • 9
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    Using misorientation and weighted burgers vector statistics to understand intragranular boundary development and grain boundary formation at high temperatures (2023)
    American Geophysical Union
    Details
    Publication Date: 2023-02-21
    Description: Author Posting. © American Geophysical Union, 2022. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 127(8), (2022): e2022JB024497, https://doi.org/10.1029/2022JB024497.
    Description: During plastic deformation, strain weakening can be achieved, in part, via strain energy reduction associated with intragranular boundary development and grain boundary formation. Grain boundaries (in 2D) are segments between triple junctions, that connect to encircle grains; every boundary segment in the encircling loop has a high (〉10°) misorientation angle. Intragranular boundaries terminate within grains or dissect grains, usually containing boundary segments with a low (〈10°) misorientation angle. We analyze electron backscatter diffraction (EBSD) data from ice deformed at −30°C (Th≈ 0.9). Misorientation and weighted Burgers vector (WBV) statistics are calculated along planar intragranular boundaries. Misorientation angles change markedly along each intragranular boundary, linking low- (〈10°) and high-angle (10–38°) segments that exhibit distinct misorientation axes and WBV directions. We suggest that these boundaries might be produced by the growth and intersection of individual intragranular boundary segments comprising dislocations with distinct slip systems. There is a fundamental difference between misorientation axis distributions of intragranular boundaries (misorientation axes mostly confined to ice basal plane) and grain boundaries (no preferred misorientation axis). These observations suggest during progressive subgrain rotation, intragranular boundaries remain crystallographically controlled up to large misorientation angles (〉〉10°). In contrast, the apparent lack of crystallographic control for grain boundaries suggests misorientation axes become randomized, likely due to the activation of additional mechanisms (such as grain boundary sliding) after grain boundary formation, linking boundary segments to encircle a grain. Our findings on ice intragranular boundary development and grain boundary formation may apply more broadly to other rock-forming minerals (e.g., olivine, quartz).
    Description: This work was supported by a NASA fund (Grant No. NNX15AM69G) to David L. Goldsby and two Marsden Funds of the Royal Society of New Zealand (Grant Nos. UOO1116, UOO052) to David J. Prior. Sheng Fan was supported by the University of Otago doctoral scholarship, the Antarctica New Zealand doctoral scholarship, a research grant from New Zealand Ministry of Business, Innovation and Employment through the Antarctic Science Platform (ANTA1801) (Grant No. ASP-023-03), and a New Zealand Antarctic Research Institute (NZARI) Early Career Researcher Seed Grant (Grant No. NZARI 2020-1-5). Open access publishing facilitated by University of Otago, as part of the Wiley – University of Otago agreement via the Council of Australian University Librarians.
    Keywords: High temperature deformation ; Misorientation ; Weighted Burgers vector ; Intragranular boundary ; Grain boundary ; Boundary geometry
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  • 10
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    A Review of Arctic–Subarctic Ocean Linkages: Past Changes, Mechanisms, and Future Projections (2023)
    American Association for the Advancement of Science (AAAS)
    In:  EPIC3Ocean-Land-Atmosphere Research, American Association for the Advancement of Science (AAAS), 2, ISSN: 2771-0378
    Details
    Publication Date: 2023-08-08
    Description: 〈jats:p〉Arctic Ocean gateway fluxes play a crucial role in linking the Arctic with the global ocean and affecting climate and marine ecosystems. We reviewed past studies on Arctic–Subarctic ocean linkages and examined their changes and driving mechanisms. Our review highlights that radical changes occurred in the inflows and outflows of the Arctic Ocean during the 2010s. Specifically, the Pacific inflow temperature in the Bering Strait and Atlantic inflow temperature in the Fram Strait hit record highs, while the Pacific inflow salinity in the Bering Strait and Arctic outflow salinity in the Davis and Fram straits hit record lows. Both the ocean heat convergence from lower latitudes to the Arctic and the hydrological cycle connecting the Arctic with Subarctic seas were stronger in 2000–2020 than in 1980–2000. CMIP6 models project a continuing increase in poleward ocean heat convergence in the 21st century, mainly due to warming of inflow waters. They also predict an increase in freshwater input to the Arctic Ocean, with the largest increase in freshwater export expected to occur in the Fram Strait due to both increased ocean volume export and decreased salinity. Fram Strait sea ice volume export hit a record low in the 2010s and is projected to continue to decrease along with Arctic sea ice decline. We quantitatively attribute the variability of the volume, heat, and freshwater transports in the Arctic gateways to forcing within and outside the Arctic based on dedicated numerical simulations and emphasize the importance of both origins in driving the variability.〈/jats:p〉
    Repository Name: EPIC Alfred Wegener Institut
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  • 11
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    Antarctic marine life under pressure (2022)
    American Association for the Advancement of Science (AAAS)
    In:  EPIC3Science, American Association for the Advancement of Science (AAAS), 378(6617), pp. 230-230, ISSN: 0036-8075
    Details
    Publication Date: 2023-05-10
    Description: 〈jats:p〉 Next week, the Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR) convenes in Hobart, Tasmania, to examine the state of marine life in the Southern Ocean. As part of the Antarctic Treaty System, this convention entered into force in 1982, and its focus on the region’s environmental integrity has never been more important, given the increasing effects of climate change and commercial fishing. An important focus over the past 40 years has been Antarctic krill, 〈jats:italic〉Euphausia superba〈/jats:italic〉 (hereafter krill), a keystone species that helps to hold this marine ecosystem together. Climate and fishing stresses should prompt the CCAMLR to address whether management of krill fishing is at a level that protects the Southern Ocean from losing its overall balance of marine life and the oceanic processes that regulate global climate. 〈/jats:p〉
    Repository Name: EPIC Alfred Wegener Institut
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  • 12
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    Monitoring volcanic activity through combined measurements of CO2 efflux and (222Rn) and (220Rn) in soil gas: an application to Mt. Etna (Italy) (2023)
    American Geophysical Union
    Details
    Publication Date: 2023-02-07
    Description: We present measurements of soil CO2 effluxes combined with soil (222Rn) and (220Rn) from two high-degassing areas on the lower flanks of Mt. Etna volcano (ZE-SV on the E flank and PAT on the SW flank). Measurements were conducted periodically from June 2006 to January 2009 in the ZE-SV area and January 2007 to January 2009 in the PAT area. The results showed significant variations in discharge activity and style. Log values of (220Rn)/(222Rn) and CO2 efflux generally follow a negative correlation, herein parameterized as the Soil Gas Disequilibrium Index (SGDI). Deviations of the SGDI from this negative correlation provide insight into variance of localized and shallow system conditions, namely rock fracturing, residual magma degassing, and near surface interactions between magmatic gases and groundwater. Statistical analysis highlighted signal anomalies, both negative and positive, that were modeled according to the physical properties and the modes of transport for each of the SGDI gas components. The revealed anomalies show correspondence with episodes of magma ascent and eruption, thereby demonstrating the potential of using the SGDI as another instrument for forecasting volcanic activity. An important strength of the SGDI, compared to other magma gas proxies like CO2 or SO2, is that the very short and very different half-lives of 222Rn (t1/2 = 3.85 days) and 220Rn (t1/2 = 55 seconds) provide unique information on the timescales of soil gas transport. Coupling the SGDI with other pre-eruptive proxies enhances the volcanological community’s response capabilities, which is critical for effective hazard mitigation.
    Description: Published
    Description: 167-202
    Description: 4V. Processi pre-eruttivi
    Keywords: Soil gases ; radon ; carbon dioxide ; volcano monitoring ; 04.08. Volcanology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 13
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    Relative timing of off‐axis volcanism from sediment thickness estimates on the 8°20’N seamount chain, East Pacific Rise (2023)
    American Geophysical Union
    Details
    Publication Date: 2023-02-16
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Fabbrizzi, A., Parnell‐Turner, R., Gregg, P., Fornari, D., Perfit, M., Wanless, V., & Anderson, M. Relative timing of off‐axis volcanism from sediment thickness estimates on the 8°20’N seamount chain, East Pacific Rise. Geochemistry, Geophysics, Geosystems, 23(9), (2022): e2022GC010335, https://doi.org/10.1029/2022gc010335.
    Description: Volcanic seamount chains on the flanks of mid-ocean ridges record variability in magmatic processes associated with mantle melting over several millions of years. However, the relative timing of magmatism on individual seamounts along a chain can be difficult to estimate without in situ sampling and is further hampered by Ar40/Ar39 dating limitations. The 8°20’N seamount chain extends ∼170 km west from the fast-spreading East Pacific Rise (EPR), north of and parallel to the western Siqueiros fracture zone. Here, we use multibeam bathymetric data to investigate relationships between abyssal hill formation and seamount volcanism, transform fault slip, and tectonic rotation. Near-bottom compressed high-intensity radiated pulse, bathymetric, and sidescan sonar data collected with the autonomous underwater vehicle Sentry are used to test the hypothesis that seamount volcanism is age-progressive along the seamount chain. Although sediment on seamount flanks is likely to be reworked by gravitational mass-wasting and current activity, bathymetric relief and Sentry vehicle heading analysis suggest that sedimentary accumulations on seamount summits are likely to be relatively pristine. Sediment thickness on the seamounts' summits does not increase linearly with nominal crustal age, as would be predicted if seamounts were constructed proximal to the EPR axis and then aged as the lithosphere cooled and subsided away from the ridge. The thickest sediments are found at the center of the chain, implying the most ancient volcanism there, rather than on seamounts furthest from the EPR. The nonlinear sediment thickness along the 8°20’N seamounts suggests that volcanism can persist off-axis for several million years.
    Description: This work was supported by National Science Foundation awards OCE-1356610, OCE-1356822, OCE-1357150, OCE-1754419, OCE-1834797, OCE-2001314, and OCE-2001331.
    Keywords: Off-axis seamounts ; East Pacific Rise ; Sediment thickness ; Seafloor morphology ; Autonomous underwater vehicle ; Eruption history
    Repository Name: Woods Hole Open Access Server
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  • 14
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    Size-differentiated export flux in different dynamical regimes in the ocean (2021)
    American Geophysical Union
    Details
    Publication Date: 2023-02-17
    Description: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 35(3), (2021): e2020GB006764, https://doi.org/10.1029/2020GB006764
    Description: Export of Particulate Organic Carbon (POC) is mainly driven by gravitational sinking. Thus, traditionally, it is thought that larger, faster-sinking particles make up most of the POC export flux. However, this need not be the case for particles whose sinking speeds are comparable to the vertical velocities of a dynamic flow field that can influence the descent rate of particles. Particles with different settling speeds are released in two process-oriented model simulations of an upper ocean eddying flow in the Northeast Pacific to evaluate the impact of (1) ocean dynamics on the respective contribution of the different sinking-velocity classes to POC export, and (2) the particle number size-spectrum slope. The analysis reveals that the leading export mechanism changes from gravitationally driven to advectively driven as submesoscale dynamics become more active in the region. The vertical velocity associated with submesoscale dynamics enhances the contribution of slower-sinking particles to POC export flux by a factor ranging from 3 to 10, especially where the relative abundance of small particles is large (i.e., steep particle size-spectrum slope). Remineralization generally decreases the total amount of biomass exported, but its impact is weaker in dynamical regimes where submesoscale dynamics are present and export is advectively driven. In an advectively driven export regime, remineralization processes counter-intuitively enhance the role of slower-sinking particles to the point where these slower-sinking velocity classes dominate the export, therefore challenging the traditional paradigm for POC export. This study demonstrates that slow-sinking particles can be a significant contribution, and at times, even dominate the export flux.
    Description: The work was funded by NASA grant NNX16AR48 G, to complement the EXport Processes in the global Ocean from RemoTe Sensing (EXPORTS) program.
    Description: 2021-08-17
    Keywords: Export ; Flux ; Particulate organic carbon ; Sinking rates ; Submeso-scales ; Vertical velocities
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  • 15
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    The influence of ocean topography on the upwelling of carbon in the Southern Ocean (2023)
    American Geophysical Union
    Details
    Publication Date: 2023-02-17
    Description: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 48(19), (2021): e2021GL095088, https://doi.org/10.1029/2021GL095088.
    Description: The physical circulation of the Southern Ocean sets the surface concentration and thus air-sea exchange of CO2. However, we have a limited understanding of the three-dimensional circulation that brings deep carbon-rich waters to the surface. Here, we introduce and analyze a novel high-resolution ocean model simulation with active biogeochemistry and online Lagrangian particle tracking. We focus our attention on a subset of particles with high dissolved inorganic carbon (DIC) that originate below 1,000 m and eventually upwell into the near-surface layer (upper 200 m). We find that 71% of the DIC-enriched water upwelling across 1,000 m is concentrated near topographic features, which occupy just 33% of the Antarctic Circumpolar Current. Once particles upwell to the near-surface layer, they exhibit relatively uniform pCO2 levels and DIC decorrelation timescales, regardless of their origin. Our results show that Southern Ocean bathymetry plays a key role in delivering carbon-rich waters to the surface.
    Description: Riley X. Brady was supported by the Department of Energy's Computational Science Graduate Fellowship (DE-FG02-97ER25308), and particularly benefited from the fellowship's summer practicum at Los Alamos National Lab. Nicole S. Lovenduski and Riley X. Brady were further supported by the U.S. Department of Energy Biological and Environmental Research program (DE-SC0022243) and by the National Science Foundation (NSF-PLR 1543457; NSF-OCE 1924636; NSF-OCE 1752724; NSF-OCE 1558225). Mathew E. Maltrud and Phillip J. Wolfram were supported as part of the Energy Exascale Earth System Model (E3SM) project, funded by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research. This research used resources provided by the Los Alamos National Laboratory Institutional Computing Program, which is supported by the U.S. Department of Energy National Nuclear Security Administration under Contract No. 89233218CNA000001.
    Keywords: Southern Ocean ; Carbon cycle ; Upwelling ; Lagrangian modeling ; Ocean biogeochemistry ; Climate modeling
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  • 16
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    Submarine groundwater discharge in the northern Bohai Sea, China: Implications for coastal carbon budgets and buffering capacity (2022)
    American Geophysical Union
    Details
    Publication Date: 2023-01-20
    Description: Author Posting. © American Geophysical Union, 2022. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Biogeosciences 127(8), (2022): e2022JG006810, https://doi.org/10.1029/2022jg006810.
    Description: Submarine groundwater discharge (SGD) has been widely recognized as an important source of dissolved nutrients in coastal waters and affects nutrient biogeochemistry. In contrast, little information is available on SGD impacts on coastal carbon budgets. Here, we assessed the SGD and associated carbon (dissolved inorganic carbon [DIC] and total alkalinity [TA]) fluxes in Liaodong Bay (the largest bay of the Bohai Sea, China) and discussed their border implications for coastal DIC budget and buffering capacity. Based on 223Ra and 228Ra mass balance models, the SGD flux was estimated to be (0.92–1.43) × 109 m3 d−1. SGD was the largest contributor of DIC, accounting for 55%–77% of the total DIC sources. The low ratio (〈1) of SGD-derived TA to DIC fluxes and negative correlation between radium isotopes and pH in seawater implied that SGD would potentially reduce seawater pH in Liaodong Bay. Combining the groundwater carbon data in Liaodong Bay with literature data, we found that the SGD-derived DIC flux off China was 4–9 times greater than those from rivers. By analyzing the TA/DIC ratios in groundwater along the Chinese coast and related carbon fluxes, SGD was thought to partially reduce the CO2 buffer capacity in receiving seawater. These results obtained at the bay scale and national scale suggest that SGD is a significant component of carbon budget and may play a critical role in modulating coastal buffering capacity and atmospheric CO2 sequestration.
    Description: his research was supported by National Natural Science Foundation of China (Grant Nos. 42130703, 42007170) and the Science, Technology and Innovation Commission of Shenzhen (Grant No. 20200925174525002.
    Description: 2023-01-20
    Keywords: Submarine groundwater discharge ; Radium isotopes ; Dissolved inorganic carbon ; Total alkalinity ; Carbon budgets ; Buffering capacity
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  • 17
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    Retrieving a “Weather Balloon” from the last Ice Age (2023)
    American Geophysical Union
    Details
    Publication Date: 2023-02-28
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Seltzer, A. M., & Tyne, R. L. Retrieving a “Weather Balloon” from the last Ice Age. AGU Advances, 3(4), (2022): e2022AV000747, https://doi.org/10.1029/2022AV000747.
    Description: “How cold was the last ice age?” is a question that paleoclimate scientists have been trying to answer for decades. Constraining the magnitude of climate change since the Last Glacial Maximum (∼20,000 years ago) can help improve our understanding of Earth's climate sensitivity and, therefore enhance our ability to predict future change (Tierney et al., 2020). Of course, there is no single answer to this question: there is spatial structure to LGM temperature change that is linked to fundamental climate system properties and processes. Consequently, paleoclimate scientists have focused on variations of this question, like “What was the latitudinal gradient of LGM temperature change?” (Chiang et al., 2003), “What was the land-sea contrast?” (Rind & Peteet, 1985) or “What was the change in ocean heat content?” (Bereiter et al., 2018). These questions inform large-scale atmospheric and oceanic circulation, the intensity of the water cycle, and planetary energy balance; the answers to these questions come from proxies like planktic and benthic foraminifera, speleothems, ice cores, pollen records, ancient groundwater, lake sediments, and glacial moraines, to name a few. In short, the paleoclimate community has developed a proxy “tool kit” equipped to map changes across the Earth's surface and into the ocean interior; but, until now, no “tool” existed for the upper atmosphere.
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    Sediments in sea ice drive the Canada Basin surface Mn maximum: insights from an Arctic Mn Ocean model (2023)
    American Geophysical Union
    Details
    Publication Date: 2023-02-28
    Description: Author Posting. © American Geophysical Union, 2022. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 36(8), (2022): e2022GB007320, https://doi.org/10.1029/2022GB007320.
    Description: Biogeochemical cycles in the Arctic Ocean are sensitive to the transport of materials from continental shelves into central basins by sea ice. However, it is difficult to assess the net effect of this supply mechanism due to the spatial heterogeneity of sea ice content. Manganese (Mn) is a micronutrient and tracer which integrates source fluctuations in space and time while retaining seasonal variability. The Arctic Ocean surface Mn maximum is attributed to freshwater, but studies struggle to distinguish sea ice and river contributions. Informed by observations from 2009 IPY and 2015 Canadian GEOTRACES cruises, we developed a three-dimensional dissolved Mn model within a 1/12° coupled ocean-ice model centered on the Canada Basin and the Canadian Arctic Archipelago (CAA). Simulations from 2002 to 2019 indicate that annually, 87%–93% of Mn contributed to the Canada Basin upper ocean is released by sea ice, while rivers, although locally significant, contribute only 2.2%–8.5%. Downstream, sea ice provides 34% of Mn transported from Parry Channel into Baffin Bay. While rivers are often considered the main source of Mn, our findings suggest that in the Canada Basin they are less important than sea ice. However, within the shelf-dominated CAA, both rivers and sediment resuspension are important. Climate-induced disruption of the transpolar drift may reduce the Canada Basin Mn maximum and supply downstream. Other micronutrients found in sediments, such as Fe, may be similarly affected. These results highlight the vulnerability of the biogeochemical supply mechanisms in the Arctic Ocean and the subpolar seas to climatic changes.
    Description: This work was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC) Climate Change and Atmospheric Research Grant: GEOTRACES (RGPCC 433848-12) and VITALS (RGPCC 433898), an NSERC Discovery Grant (RGPIN-2016-03865) to SEA, and by the University of British Columbia through a four year fellowship to BR. Computing resources were provided by Compute Canada (RRG 2648 RAC 2019, RRG 2969 RAC 2020, and RRG 1541 RAC 2021).
    Keywords: GEOTRACES ; Arctic Ocean ; Trace elements ; Canadian Arctic Archipelago ; Ocean modeling ; Micronutrients
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  • 19
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    WISTFUL: whole‐rock interpretative seismic toolbox for ultramafic lithologies (2023)
    American Geophysical Union
    Details
    Publication Date: 2023-02-28
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Shinevar, W., Jagoutz, O., & Behn, M. WISTFUL: whole‐rock interpretative seismic toolbox for ultramafic lithologies. Geochemistry, Geophysics, Geosystems, 23(8), (2022): e2022GC010329, https://doi.org/10.1029/2022gc010329.
    Description: To quantitatively convert upper mantle seismic wave speeds measured into temperature, density, composition, and corresponding and uncertainty, we introduce the Whole-rock Interpretative Seismic Toolbox For Ultramafic Lithologies (WISTFUL). WISTFUL is underpinned by a database of 4,485 ultramafic whole-rock compositions, their calculated mineral modes, elastic moduli, and seismic wave speeds over a range of pressure (P) and temperature (T) (P = 0.5–6 GPa, T = 200–1,600°C) using the Gibbs free energy minimization routine Perple_X. These data are interpreted with a toolbox of MATLAB® functions, scripts, and three general user interfaces: WISTFUL_relations, which plots relationships between calculated parameters and/or composition; WISTFUL_geotherms, which calculates seismic wave speeds along geotherms; and WISTFUL_inversion, which inverts seismic wave speeds for best-fit temperature, composition, and density. To evaluate our methodology and quantify the forward calculation error, we estimate two dominant sources of uncertainty: (a) the predicted mineral modes and compositions, and (b) the elastic properties and mixing equations. To constrain the first source of uncertainty, we compiled 122 well-studied ultramafic xenoliths with known whole-rock compositions, mineral modes, and estimated P-T conditions. We compared the observed mineral modes with modes predicted using five different thermodynamic solid solution models. The Holland et al. (2018, https://doi.org/10.1093/petrology/egy048) solution models best reproduce phase assemblages (∼12 vol. % phase root-mean-square error [RMSE]) and estimated wave speeds. To assess the second source of uncertainty, we compared wave speed measurements of 40 ultramafic rocks with calculated wave speeds, finding excellent agreement (Vp RMSE = 0.11 km/s). WISTFUL easily analyzes seismic datasets, integrates into modeling, and acts as an educational tool.
    Description: Funding for this study was provided by NSF Grants EAR-17-22935 (OJ) and EAR-18-44340 (MB).
    Keywords: Seismic velocity ; Seismic wave speed ; Thermodynamic modeling ; Density ; Composition ; Elastic moduli
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  • 20
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    Can we estimate air‐sea flux of biological O2 from total dissolved oxygen? (2023)
    American Geophysical Union
    Details
    Publication Date: 2023-03-02
    Description: Author Posting. © American Geophysical Union, 2022. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 36(9), (2022): e2021GB007145, https://doi.org/10.1029/2021gb007145.
    Description: In this study, we compare mechanistic and empirical approaches to reconstruct the air-sea flux of biological oxygen (F[O2]bio-as) by parameterizing the physical oxygen saturation anomaly (ΔO2[phy]) in order to separate the biological contribution from total oxygen. The first approach matches ΔO2[phy] to the monthly climatology of the argon saturation anomaly from a global ocean circulation model's output. The second approach derives ΔO2[phy] from an iterative mass balance model forced by satellite-based physical drivers of ΔO2[phy] prior to the sampling day by assuming that air-sea interactions are the dominant factors driving the surface ΔO2[phy]. The final approach leverages the machine-learning technique of Genetic Programming (GP) to search for the functional relationship between ΔO2[phy] and biophysicochemical parameters. We compile simultaneous measurements of O2/Ar and O2 concentration from 14 cruises to train the GP algorithm and test the validity and applicability of our modeled ΔO2[phy] and F[O2]bio-as. Among the approaches, the GP approach, which incorporates ship-based measurements and historical records of physical parameters from the reanalysis products, provides the most robust predictions (R2 = 0.74 for ΔO2[phy] and 0.72 for F[O2]bio-as; RMSE = 1.4% for ΔO2[phy] and 7.1 mmol O2 m−2 d−1 for F[O2]bio-as). We use the empirical formulation derived from GP approach to reconstruct regional, inter-annual, and decadal variability of F[O2]bio-as based on historical oxygen records. Overall, our study represents a first attempt at deriving F[O2]bio-as from snapshot measurements of oxygen, thereby paving the way toward using historical O2 data and a rapidly growing number of O2 measurements on autonomous platforms for independent insight into the biological pump.
    Description: N. Cassar was supported by the “Laboratoire d'Excellence” LabexMER (ANR-10-LABX-19) and co-funded by a grant from the French government under the program “Investissements d'Avenir.” Y. Huang was supported by grants from the China NSF (Nos. 42130401 and 42141002). Y. Huang was also partly supported by Chinese State Scholarship Fund to study at Duke University as a joint PhD student (No. 201806310052). R. Eveleth was supported by the NSF GRFP under grant (No. 1106401). D. Nicholson was supported by the NSF OCE-1129973 and OCE-1923915.
    Keywords: Air-sea gas biological oxygen flux ; Physical oxygen saturation anomaly ; Total dissolved oxygen ; Mechanistic and empirical models
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  • 21
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    Accuracy and reproducibility of coral Sr/Ca SIMS timeseries in modern and fossil corals (2023)
    American Geophysical Union
    Details
    Publication Date: 2023-03-08
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Sayani, H., Cobb, K., Monteleone, B., & Bridges, H. Accuracy and reproducibility of coral Sr/Ca SIMS timeseries in modern and fossil corals. Geochemistry, Geophysics, Geosystems, 23(9), (2022): e2021GC010068, https://doi.org/10.1029/2021gc010068.
    Description: Coral strontium-to-calcium ratios (Sr/Ca) provide quantitative estimates of past sea surface temperatures (SST) that allow for the reconstruction of changes in the mean state and climate variations, such as the El Nino-Southern Oscillation, through time. However, coral Sr/Ca ratios are highly susceptible to diagenesis, which can impart artifacts of 1–2°C that are typically on par with the tropical climate signals of interest. Microscale sampling via Secondary Ion Mass Spectrometry (SIMS) for the sampling of primary skeletal material in altered fossil corals, providing much-needed checks on fossil coral Sr/Ca-based paleotemperature estimates. In this study, we employ a set modern and fossil corals from Palmyra Atoll, in the central tropical Pacific, to quantify the accuracy and reproducibility of SIMS Sr/Ca analyses relative to bulk Sr/Ca analyses. In three overlapping modern coral samples, we reproduce bulk Sr/Ca estimates within ±0.3% (1σ). We demonstrate high fidelity between 3-month smoothed SIMS coral Sr/Ca timeseries and SST (R = −0.5 to −0.8; p 〈 0.5). For lightly-altered sections of a young fossil coral from the early-20th century, SIMS Sr/Ca timeseries reproduce bulk Sr/Ca timeseries, in line with our results from modern corals. Across a moderately-altered section of the same fossil coral, where diagenesis yields bulk Sr/Ca estimates that are 0.6 mmol too high (roughly equivalent to −6°C artifacts in SST), SIMS Sr/Ca timeseries track instrumental SST timeseries. We conclude that 3–4 SIMS analyses per month of coral growth can provide a much-needed quantitative check on the accuracy of fossil coral Sr/Ca-derived estimates of paleotemperature, even in moderately altered samples.
    Description: We'd also like to thank Yolande Berta and Georgia Tech's Center for Nanostructure Characterization for providing access to their SEM facilities, and the Khaled bin Sultan Living Ocean Foundation and The Nature Conservancy for financial and logistical support for field excursions to Palmyra. Funding for this work was provided by the National Science Foundation (Award Numbers 1502832 and 2002458 to K.M.C) and the National Oceanic and Atmospheric Administration (Award Number: NA11OAR4310165 to K.M.C).
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    Observational and modeling evidence of seasonal trends in sediment-derived material inputs to the Chukchi Sea (2020)
    American Geophysical Union
    Details
    Publication Date: 2023-03-08
    Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 125(5), (2020): e2019JC016007, doi:10.1029/2019JC016007.
    Description: Benthic inputs of nutrients help support primary production in the Chukchi Sea and produce nutrient‐rich water masses that ventilate the halocline of the western Arctic Ocean. However, the complex biological and redox cycling of nutrients and trace metals make it difficult to directly monitor their benthic fluxes. In this study, we use radium‐228, which is a soluble radionuclide produced in sediments, and a numerical model of an inert, generic sediment‐derived tracer to study variability in sediment inputs to the Chukchi Sea. The 228Ra observations and modeling results are in general agreement and provide evidence of strong benthic inputs to the southern Chukchi Sea during the winter, while the northern shelf receives higher concentrations of sediment‐sourced materials in the spring and summer due to continued sediment‐water exchange as the water mass traverses the shelf. The highest tracer concentrations are observed near the shelfbreak and southeast of Hanna Shoal, a region known for high biological productivity and enhanced benthic biomass.
    Description: This study presents data from multiple Arctic expeditions over the past two decades, and we are indebted to the captains, crews, and scientific parties that made this data collection possible. This work was funded by NSF awards OCE‐1458305 to M. Charette, OCE‐1458424 to W. Moore, OCE‐1434085 to D. Kadko, PLR‐1504333 to R. Pickart, and OPP‐1822334 to M. Spall. Funding was also provided by National Oceanic and Atmospheric Administration Grant NA14‐OAR4320158 to R. Pickart. L. Kipp was supported by an Ocean Frontier Institute Postdoctoral Fellowship. Radium data used in this manuscript are available in Table S1.
    Description: 2020-10-27
    Keywords: Chukchi Sea ; Benthic flux ; Radium‐228 ; GEOTRACES
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    Drifter observations reveal intense vertical velocity in a surface ocean front (2023)
    American Geophysical Union
    Details
    Publication Date: 2023-03-11
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Tarry, D., Ruiz, S., Johnston, T., Poulain, P., Özgökmen, T., Centurioni, L., Berta, M., Esposito, G., Farrar, J., Mahadevan, A., & Pascual, A. Drifter observations reveal intense vertical velocity in a surface ocean front. Geophysical Research Letters, 49(18), (2022): e2022GL098969, https://doi.org/10.1029/2022gl098969.
    Description: Measuring vertical motions represent a challenge as they are typically 3–4 orders of magnitude smaller than the horizontal velocities. Here, we show that surface vertical velocities are intensified at submesoscales and are dominated by high frequency variability. We use drifter observations to calculate divergence and vertical velocities in the upper 15 m of the water column at two different horizontal scales. The drifters, deployed at the edge of a mesoscale eddy in the Alboran Sea, show an area of strong convergence (urn:x-wiley:00948276:media:grl64766:grl64766-math-0001(f)) associated with vertical velocities of −100 m day−1. This study shows that a multilayered-drifter array can be an effective tool for estimating vertical velocity near the ocean surface.
    Description: This research was supported by the Office of Naval Research (ONR) Departmental Research Initiative CALYPSO under program officers Terri Paluszkiewicz and Scott Harper. The authors' ONR Grant No. are as follows: DT, SR, AM, and AP N000141613130, TMSJ N000146101612470, PP N000141812418, TO N000141812138, LRC N000141712517, and N00014191269, MB and GE N000141812782 and N000141812039, and JTF N000141812431.
    Keywords: Drifters ; Vertical velocity ; Submesoscale ; Kinematic properties ; Fronts ; Alboran Sea
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  • 24
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    Volcano monitoring with magnetic measurements: a simulation of eruptions at axial seamount, Kilauea, Baroarbunga, and Mount Saint Helens (2023)
    American Geophysical Union
    Details
    Publication Date: 2023-03-11
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Biasi, J., Tivey, M., & Fluegel, B. Volcano monitoring with magnetic measurements: a simulation of eruptions at axial seamount, Kilauea, Baroarbunga, and Mount Saint Helens. Geophysical Research Letters, 49(17), (2022): e2022GL100006, https://doi.org/10.1029/2022GL100006.
    Description: Monitoring of active volcanic systems is a challenging task due in part to the trade-offs between collection of high-quality data from multiple techniques and the high costs of acquiring such data. Here we show that magnetic data can be used to monitor volcanoes by producing similar data to gravimetric techniques at significantly lower cost. The premise of this technique is that magma and wall rock above the Curie temperature are magnetically “transparent,” but not stationary within the crust. Subsurface movements of magma can affect the crustal magnetic field measured at the surface. We construct highly simplified magnetic models of four volcanic systems: Mount Saint Helens (1980), Axial Seamount (2015–2020), Kīlauea (2018), and Bárðarbunga (2014). In all cases, observed or inferred changes to the magmatic system would have been detectable by modern magnetometers. Magnetic monitoring could become common practice at many volcanoes, particularly in developing nations with high volcanic risk.
    Description: This work was supported by the NSF Grant No 2052963 to J. Biasi and an internal Woods Hole Oceanographic Institution grant to M. Tivey.
    Keywords: Magnetism ; Volcanic hazards ; Hawaii ; Iceland ; Volcanology ; Monitoring
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  • 25
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    Radium inputs into the Arctic Ocean from rivers a basin‐wide estimate (2023)
    American Geophysical Union
    Details
    Publication Date: 2023-03-11
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Bullock, E., Kipp, L., Moore, W., Brown, K., Mann, P., Vonk, J., Zimov, N., & Charette, M. Radium inputs into the Arctic Ocean from rivers a basin‐wide estimate. Journal of Geophysical Research: Oceans, 127(9), (2022): e2022JC018964, https://doi.org/10.1029/2022jc018964.
    Description: Radium isotopes have been used to trace nutrient, carbon, and trace metal fluxes inputs from ocean margins. However, these approaches require a full accounting of radium sources to the coastal ocean including rivers. Here, we aim to quantify river radium inputs into the Arctic Ocean for the first time for 226Ra and to refine the estimates for 228Ra. Using new and existing data, we find that the estimated combined (dissolved plus desorbed) annual 226Ra and 228Ra fluxes to the Arctic Ocean are [7.0–9.4] × 1014 dpm y−1 and [15–18] × 1014 dpm y−1, respectively. Of these totals, 44% and 60% of the river 226Ra and 228Ra, respectively are from suspended sediment desorption, which were estimated from laboratory incubation experiments. Using Ra isotope data from 20 major rivers around the world, we derived global annual 226Ra and 228Ra fluxes of [7.4–17] × 1015 and [15–27] × 1015 dpm y−1, respectively. As climate change spurs rapid Arctic warming, hydrological cycles are intensifying and coastal ice cover and permafrost are diminishing. These river radium inputs to the Arctic Ocean will serve as a valuable baseline as we attempt to understand the changes that warming temperatures are having on fluxes of biogeochemically important elements to the Arctic coastal zone.
    Description: This study was a broad, collaborative effort that would not have been possible without contributions from numerous funding sources, including the National Science Foundation (NSF-0751525, NSF-1736277, NSF-1458305, NSF-1938873, NSF-2048067, NSF-2134865), the NERC-BMBF project CACOON [NE/R012806/1] (UKRI NERC) and BMBF-03F0806A, and an EU Starting Grant (THAWSOME-676982).
    Keywords: Radium isotopes ; Arctic Ocean ; River fluxes
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  • 26
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    Chasing iron bioavailability in the Southern Ocean: Insights from Phaeocystis antarctica and iron speciation (2023)
    American Association for the Advancement of Science (AAAS)
    In:  EPIC3Science Advances, American Association for the Advancement of Science (AAAS), 9(26), pp. eadf9696-eadf9696, ISSN: 2375-2548
    Details
    Publication Date: 2024-03-01
    Description: Dissolved iron (dFe) availability limits the uptake of atmospheric CO2 by the Southern Ocean (SO) biological pump. Hence, any change in bioavailable dFe in this region can directly influence climate. On the basis of Fe uptake experiments with Phaeocystis antarctica, we show that the range of dFe bioavailability in natural samples is wider (〈1 to ~200% compared to free inorganic Fe′) than previously thought, with higher bioavailability found near glacial sources. The degree of bioavailability varied regardless of in situ dFe concentration and depth, challenging the consensus that sole dFe concentrations can be used to predict Fe uptake in modeling studies. Further, our data suggest a disproportionately major role of biologically mediated ligands and encourage revisiting the role of humic substances in influencing marine Fe biogeochemical cycling in the SO. Last, we describe a linkage between in situ dFe bioavailability and isotopic signatures that, we anticipate, will stimulate future research.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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    Improving Arctic sea-ice thickness estimates with the assimilation of CryoSat-2 summer observations (2023)
    American Association for the Advancement of Science (AAAS)
    In:  EPIC3Ocean-Land-Atmosphere Research, American Association for the Advancement of Science (AAAS), 2, ISSN: 2771-0378
    Details
    Publication Date: 2024-02-13
    Description: 〈jats:p〉Rapidly shrinking Arctic sea ice has had substantial impacts on the Earth system. Therefore, reliably estimating the Arctic sea-ice thickness (SIT) using a combination of available observations and numerical modeling is urgently needed. Here, for the first time, we assimilate the latest CryoSat-2 summer SIT data into a coupled ice-ocean model. In particular, an incremental analysis update scheme is implemented to overcome the discontinuity resulting from the combined assimilation of biweekly SIT and daily sea-ice concentration (SIC) data. Along with improved estimates of sea-ice volume, our SIT estimates corrected the overestimation of SIT produced by the reanalysis that assimilates only SIC in summer in areas where the sea ice is roughest and experiences strong deformation, e.g., around the Fram Strait and Greenland. This study suggests that the newly developed CryoSat-2 SIT product, when assimilated properly using our approach, has great potential for Arctic sea-ice simulation and prediction.〈/jats:p〉
    Repository Name: EPIC Alfred Wegener Institut
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    Genomic evidence for West Antarctic Ice Sheet collapse during the Last Interglacial (2023)
    American Association for the Advancement of Science (AAAS)
    In:  EPIC3Science, American Association for the Advancement of Science (AAAS), 382(6677), pp. 1384-1389, ISSN: 0036-8075
    Details
    Publication Date: 2024-02-22
    Description: The marine-based West Antarctic Ice Sheet (WAIS) is considered vulnerable to irreversible collapse under future climate trajectories, and its tipping point may lie within the mitigated warming scenarios of 1.5° to 2°C of the United Nations Paris Agreement. Knowledge of ice loss during similarly warm past climates could resolve this uncertainty, including the Last Interglacial when global sea levels were 5 to 10 meters higher than today and global average temperatures were 0.5° to 1.5°C warmer than preindustrial levels. Using a panel of genome-wide, single-nucleotide polymorphisms of a circum-Antarctic octopus, we show persistent, historic signals of gene flow only possible with complete WAIS collapse. Our results provide the first empirical evidence that the tipping point of WAIS loss could be reached even under stringent climate mitigation scenarios.
    Repository Name: EPIC Alfred Wegener Institut
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  • 29
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    Caribbean salinity anomalies contributed to variable North Atlantic circulation and climate during the Common Era (2023)
    American Association for the Advancement of Science (AAAS)
    In:  EPIC3Science Advances, American Association for the Advancement of Science (AAAS), 9(44), pp. eadg2639-eadg2639, ISSN: 2375-2548
    Details
    Publication Date: 2024-04-24
    Description: Paleoceanographic reconstructions show that the strength of North Atlantic currents decreased during the Little Ice Age. In contrast, the role of ocean circulation in climate regulation during earlier historical epochs of the Common Era (C.E.) remains unclear. Here, we reconstruct sea surface temperature (SST) and salinity in the Caribbean Basin for the past 1700 years using the isotopic and elemental composition of planktic foraminifera tests. Centennial-scale SST and salinity variations in the Caribbean co-occur with (hydro)climate changes in the Northern Hemisphere and are linked to a North Atlantic SST forcing. Cold phases around 600, 800, and 1400 to 1600 C.E. are characterized by Caribbean salinification and Gulf of Mexico freshening that implies reductions in the strength of North Atlantic surface circulation. We suggest that the associated changes in the meridional salt advection contributed to the historical climate variability of the C.E.
    Repository Name: EPIC Alfred Wegener Institut
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  • 30
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    Structure-informed microbial population genetics elucidate selective pressures that shape protein evolution (2023)
    American Association for the Advancement of Science (AAAS)
    In:  EPIC3Science Advances, American Association for the Advancement of Science (AAAS), 9(8), pp. eabq4632-eabq4632, ISSN: 2375-2548
    Details
    Publication Date: 2024-04-03
    Description: 〈jats:p〉Comprehensive sampling of natural genetic diversity with metagenomics enables highly resolved insights into the interplay between ecology and evolution. However, resolving adaptive, neutral, or purifying processes of evolution from intrapopulation genomic variation remains a challenge, partly due to the sole reliance on gene sequences to interpret variants. Here, we describe an approach to analyze genetic variation in the context of predicted protein structures and apply it to a marine microbial population within the SAR11 subclade 1a.3.V, which dominates low-latitude surface oceans. Our analyses reveal a tight association between genetic variation and protein structure. In a central gene in nitrogen metabolism, we observe decreased occurrence of nonsynonymous variants from ligand-binding sites as a function of nitrate concentrations, revealing genetic targets of distinct evolutionary pressures maintained by nutrient availability. Our work yields insights into the governing principles of evolution and enables structure-aware investigations of microbial population genetics.〈/jats:p〉
    Repository Name: EPIC Alfred Wegener Institut
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  • 31
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    Spatial heterogeneity and environmental predictors of permafrost region soil organic carbon stocks (2021)
    American Association for the Advancement of Science (AAAS)
    In:  EPIC3Science Advances, American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2024-04-22
    Description: Large stocks of soil organic carbon (SOC) have accumulated in the northern hemisphere permafrost region, but their current mounts and future fate remain uncertain. By analyzing an unprecedented dataset combining 〉2,700 soil profiles with environmental variables in a geospatial framework, we generated spatially explicit estimates of permafrost-region SOC stocks, quantified spatial heterogeneity, and identified key environmental predictors. We estimated 1014−175+194 Pg C are stored in the top 3 m of permafrost region soils. The greatest uncertainties occurred in circumpolar toe-slope positions and in flat areas of the Tibetan region. We found that soil wetness index and elevation are the dominant topographic controllers and surface air temperature (circumpolar region) and precipitation (Tibetan region) are significant climatic controllers of SOC stocks. Our results provide the first high-resolution geospatial assessment of permafrost region SOC stocks and their relationships with environmental factors, which are crucial for modeling the response of permafrost affected soils to changing climate.
    Repository Name: EPIC Alfred Wegener Institut
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  • 32
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    Erratum to “A Review of Arctic–Subarctic Ocean Linkages: Past Changes, Mechanisms, and Future Projections” (2023)
    American Association for the Advancement of Science (AAAS)
    In:  EPIC3Ocean-Land-Atmosphere Research, American Association for the Advancement of Science (AAAS), 2, ISSN: 2771-0378
    Details
    Publication Date: 2024-01-20
    Repository Name: EPIC Alfred Wegener Institut
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  • 33
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    Global and regional temperature change over the past 4.5 million years (2024)
    American Association for the Advancement of Science (AAAS)
    In:  EPIC3Science, American Association for the Advancement of Science (AAAS), 383(6685), pp. 884-890, ISSN: 0036-8075
    Details
    Publication Date: 2024-03-21
    Description: Much of our understanding of Cenozoic climate is based on the record of δ18O measured in benthic foraminifera. However, this measurement reflects a combined signal of global temperature and sea level, thus preventing a clear understanding of the interactions and feedbacks of the climate system in causing global temperature change. Our new reconstruction of temperature change over the past 4.5 million years includes two phases of long-term cooling, with the second phase of accelerated cooling during the Middle Pleistocene Transition (1.5 to 0.9 million years ago) being accompanied by a transition from dominant 41,000-year low-amplitude periodicity to dominant 100,000-year high-amplitude periodicity. Changes in the rates of long-term cooling and variability are consistent with changes in the carbon cycle driven initially by geologic processes, followed by additional changes in the Southern Ocean carbon cycle. 〈/jats:p〉
    Repository Name: EPIC Alfred Wegener Institut
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  • 34
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    Constraints on the Cryohydrological Warming of Firn and Ice in Greenland From Rayleigh Wave Ellipticity Data (2024)
    American Geophysical Union
    Details
    Publication Date: 2024-04-05
    Description: Rayleigh wave ellipticity measurements from seismic ambient noise recorded on the Greenland Ice Sheet (GrIS) show complex and anomalous behavior at wave periods sensitive to ice (T 〈 3–4 s). To understand these complex observations, we compare them with synthetic ellipticity measurements obtained from synthetic ambient noise computed for various seismic velocity and attenuation models, including surface wave overtone effects. We find that in dry snow conditions within the interior of the GrIS, to first order the anomalous ellipticity observations can be explained by ice models associated with the accumulation and densification of snow into firn. We also show that the distribution of ellipticity measurements is strongly sensitive to seismic attenuation and the thermal structure of the ice. Our results suggest that Rayleigh wave ellipticity is well suited for monitoring changes in firn properties and thermal composition of the Greenland and Antarctic ice sheets in a changing climate.
    Description: Published
    Description: e2023GL103673
    Description: OST1 Alla ricerca dei Motori Geodinamici
    Description: JCR Journal
    Keywords: 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 35
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    Carbon Stocks and Potential Greenhouse Gas Production of Permafrost-Affected Active Floodplains in the Lena River Delta (2024)
    American Geophysical Union
    In:  EPIC3Journal of Geophysical Research (JGR): Biogeosciences, American Geophysical Union, 129, ISSN: 2169-8953
    Details
    Publication Date: 2024-04-19
    Description: Arctic warming increases the degradation of permafrost soils but little is known about floodplain soils in the permafrost region. This study quantifies soil organic carbon (SOC) and soil nitrogen stocks, and the potential CH4 and CO2 production from seven cores in the active floodplains in the Lena River Delta, Russia. The soils were sandy but highly heterogeneous, containing deep, organic rich deposits with 〉60% SOC stored below 30 cm. The mean SOC stocks in the top 1 m were 12.9 ± 6.0 kg C m−2. Grain size analysis and radiocarbon ages indicated highly dynamic environments with sediment re-working. Potential CH4 and CO2 production from active floodplains was assessed using a 1-year incubation at 20°C under aerobic and anaerobic conditions. Cumulative aerobic CO2 production mineralized a mean 4.6 ± 2.8% of initial SOC. The mean cumulative aerobic:anaerobic C production ratio was 2.3 ± 0.9. Anaerobic CH4 production comprised 50 ± 9% of anaerobic C mineralization; rates were comparable or exceeded those for permafrost region organic soils. Potential C production from the incubations was correlated with total organic carbon and varied strongly over space (among cores) and depth (active layer vs. permafrost). This study provides valuable information on the carbon cycle dynamics from active floodplains in the Lena River Delta and highlights the key spatial variability, both among sites and with depth, and the need to include these dynamic permafrost environments in future estimates of the permafrost carbon-climate feedback.
    Repository Name: EPIC Alfred Wegener Institut
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  • 36
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    Heatwave responses of Arctic phytoplankton communities are driven by combined impacts of warming and cooling. (2024)
    American Association for the Advancement of Science (AAAS)
    In:  EPIC3Sci Adv, American Association for the Advancement of Science (AAAS), 10(20), pp. eadl5904-eadl5904, ISSN: 2375-2548
    Details
    Publication Date: 2024-05-22
    Description: Marine heatwaves are increasing in frequency and intensity as climate change progresses, especially in the highly productive Arctic regions. Although their effects on primary producers will largely determine the impacts on ecosystem services, mechanistic understanding on phytoplankton responses to these extreme events is still very limited. We experimentally exposed Arctic phytoplankton assemblages to stable warming, as well as to repeated heatwaves, and measured temporally resolved productivity, physiology, and composition. Our results show that even extreme stable warming increases productivity, while the response to heatwaves depends on the specific scenario applied and is not predictable from stable warming responses. This appears to be largely due to the underestimated impact of the cool phase following a heatwave, which can be at least as important as the warm phase for the overall response. We show that physiological and compositional adjustments to both warm and cool phases drive overall phytoplankton productivity and need to be considered mechanistically to predict overall ecosystem impacts.
    Repository Name: EPIC Alfred Wegener Institut
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  • 37
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    Phases, lattice parameters and thermal expansion of (GaxIn1−x)2Se3, 1≥x≥0, between room temperature and melting point (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 24-30 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The phases, their lattice parameters and the linear coefficient of the lattice thermal expansion were determined by high-temperature X-ray diffraction between room temperature and the melting point for the system (GaxIn1 − x)2Se3 (1 ≥ x ≥ 0). A wide homogeneity range of zinc blende structure was found in the Ga-rich region when a certain critical temperature was reached. In the In-rich region the alloys were isostructural with γ-In2Se3 at all temperatures, and the linear thermal-expansion coefficient was composition dependent.
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    URL: http://dx.doi.org/10.1107/S0021889880011454
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  • 38
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    X-ray Bragg reflexion and strain compensation in silicon crystals (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 31-33 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Crystal-lattice strain induced by impurity doping may be compensated for by diffusion of another kind of impurity. This was tried with successive diffusion of germanium and boron into (111) silicon wafers and was confirmed in a nondestructive way from the intensity profiles of the 333 Bragg reflection of Cu Kα X-rays. The intensity profile is related to the strain distribution along the depth through numerical computations, the programme for which has been developed and utilized previously [Fukuhara & Takano (1977). Acta Cryst. A33, 137–142] in quantitative discussions on strain and impurity concentration in silicon.
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  • 39
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    Electronic Resource
    The determination of diffuse-boundary thicknesses of polymers by small-angle X-ray scattering (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 34-45 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Thermal density fluctuations within phases and finite interphase widths lead to systematic deviations from Porod's law. The validity of present methods used to analyze these deviations and determine diffuse-boundary widths is determined. In view of the inadequacies found in these methods, a simple yet accurate method is proposed to determine the diffuse-boundary width from direct graphical analysis of slit-smeared intensity data. The diffuse interface is modelled by a sigmoidal-gradient model which is justified on thermodynamic grounds, with the interphase thickness as a function of the Flory–Huggins interaction parameter.
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    URL: http://dx.doi.org/10.1107/S0021889880011478
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  • 40
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    A miniature piston-cylinder apparatus for high-pressure X-ray diffraction in conjunction with energy dispersion (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 46-49 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A miniature piston-cylinder high-pressure cell has been constructed for experiments with energy-dispersive X-ray diffraction. The maximum pressure achieved was 37 × 108 Pa. Examples are given for KCl and MgO, both measured with NaCl as an internal standard. The phase transition in KCl has been observed and the CsCl structure type verified.
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  • 41
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    Electronic Resource
    Etude des défauts des croissance dans des monocristaux naturels de quartz (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 50-57 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Defects are studied in natural quartz crystals by X-ray diffraction topography with a Lang camera. Dislocations, precipitates and band growths revealed by X-ray studies are also characterized by other methods such as optical microscopy and thermoluminescence. Finally, a model of growth is proposed.
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    URL: http://dx.doi.org/10.1107/S0021889880011491
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  • 42
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    Electronic Resource
    Theoretical considerations of extra equal-thickness fringes around a dislocation outcrop observed with an X-ray plane wave (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 58-64 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: An analytical interpretation is presented of extra half-line equal-thickness fringes observed at a dislocation outcrop in X-ray and electron micrographs of wedge-shaped crystals taken at off-Bragg conditions. Extra fringes arc well explained as the interference of two wavefields deduced from Takagi's equations for dynamical diffraction in distorted crystals. Theoretical discussions given in the present paper confirm the experimentally obtained rule of Δn = h. b (h is the diffracting vector and b the Burgers vector of a dislocation), which determines the extra number of fringes, Δn, at the dislocation outcrop. When h. b ≠ integer, it is predicted that a discontinuous shift will occur in the position of equal-thickness fringes along the topographic image of a dislocation.
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  • 43
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    Electronic Resource
    Preparation and X-ray powder diffraction studies of triple orthovanadates having langbeinite structure (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 450-451 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Triple orthovanadates MIBaCr2(VO4)3 (where MI = Li, Na or Ag) are synthesised by solid-state reaction. These compounds are found to have orthorhombically distorted langbeinite structure. The crystallographic parameters of these compounds for an orthorhombic cell with P212121 as the space group and containing four formulae per unit cell are reported.
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  • 44
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    Electronic Resource
    Données cristallographiques sur les thiocyanates de tris(éthylènediamine)rhodium(III) actif, racémique et racémique actif (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 452-453 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: (±)Rh(en)3(SCN)3 and (+)Rh(en)3(SCN)3, Rh(C2H8N2)3.(SCN)3, C6H24N6Rh.C3N3S3, crystallize in orthorhombic cells. The lattice constants are respectively a = 14.652 (5), b = 14.268 (6), c = 17.480 (6) Å and a = 14.711 (4), b = 13.481 (3), c = 9.166 (2) Å. They are isomorphic with their homologues (±)Co(en)3(SCN)3 and (−)Cr(en)3(SCN)3. The active racemate [(+)Rh(en)3(+)Cr(en)3](SCN)6 is isomorphic with the monoclinic form of [(+)Co(en)3(−)Cr(en)3](SCN)6. Its lattice constants are a = 15.707 (5), b = 17.739 (4), c = 9.426 (3) Å and γ = 131.04 (2)°.
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  • 45
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    An X-ray diffraction study of the system Al2Se3In2Se3 in the In-rich region (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 454-458 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A series of samples in the system Al2Se3–In2Se3 in the In-rich region have been synthesized and studied by X-ray diffraction. In the interval of the Al/In (molar) ratio r from r≳ 1/50 to r≲ 1/20 the system has a two-phase region, α + γ1, where α is isostructural with the room-temperature modification of In2Se3, and γ1 is isostructural with the second high-temperature modification, γ, of In2Se3. For r ≳ 1/20, ternary γ1 alloys (AlxIn1−x)2Se3 are present alone and their unit-cell parameters decrease continuously as the Al content increases. These results are analogous with those obtained for the system Ga2Se3–In2Se3 in the In-rich region. The samples have also been studied by differential thermal analysis and electron-probe microanalysis.
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  • 46
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    Advances in X-ray analysis. Vol. 22 edited by G. J. McCarthy, C. S. Barrett, D. E. Leyden, J. B. Newkirk and C. O. Ruud (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 462-463 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
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  • 47
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    Industrial crystallization 78 edited by E. J. De Jong and S. J. Jancic (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 463-463 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889880012599
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  • 48
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    Calcul du Profil des bandes de diffraction produites par des empilements de feuillets de nature différente (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 148-153 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Until now, the calculation of intensities diffracted by layer structures has only been treated in the two extreme cases, namely (i) the layers interfere completely and (ii) the layers do not interfere (turbostratic structures). The present paper develops the mathematical treatment which allows the calculation in the intermediate case, namely when layers are only partially interfering.
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  • 49
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    Crystal data for new rare-earth thallates MIIITiIIIO3(M=La,Nd) (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 613-613 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Powder X-ray diffraction data for two new rare-earth thallates, MIIITlIIIO3 (M = La, Nd), have been reported. These thallates have been prepared using two chemical routes by heating homogeneous 1:1 molar reaction mixtures of (a) rare-earth carbonates, MIII2 (CO3)3.nH2O, and thallous carbonate, Tl2CO3, and (b) rare-earth oxides, MIII2O3, and thallous carbonate, in air at 823±10 K for 7 h.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889880012897
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  • 50
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    Crystal data for three new ammonium potassium pyrophosphates (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 614-615 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Unit-cell parameters and space groups have been determined for three ammonium potassium pyrophosphates. The compound (NH4, K)2H2P2O7 is triclinic with space group P1 or \overline P1, and a = 7.950 (3), b = 7.270 (3), c = 7.184 (3) Å, α = 90.89 (4), β = 117.61 (3), γ = 81.56 (4)°, Z = 2. The hydrated salt (NH4, K)2H2P2O7.0.5H2O is orthorhombic with space group Pnma or Pna21, and a = 19.22 (2), b = 7.64 (1), c = 10.39 (1) Å, Z = 8. The tribasic salt (NH4, K)3HP2O7.H2O is monoclinic with space group Cc or C2/c. The X-ray data show that a = 19.41 (2), b = 6.158 (6), c = 16.90 (2) Å, β = 107.5 (1)°, Z = 8. The indexed powder diffraction patterns are given for the three salts.
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    URL: http://dx.doi.org/10.1107/S0021889880012903
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    Small-angle X-ray scattering from solutions of flow-oriented colloidal particles (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 154-162 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The amount of information which can be obtained from a small-angle X-ray experiment can be considerably increased by orienting the solute particles with external forces during the scattering experiment. In this paper it is shown that orientation by flow, for instance through a capillary tube, gives additional information about size, shape, flexibility and rotational diffusion of the particles. The only requirement, in order to obtain flow-oriented samples, is that the solute particles must be relatively large and asymmetric. On the other hand, if the scattering curve is dependent on the flow rate through the capillary, it can immediately be concluded that the solute particles are asymmetric (or they are deformed in the hydrodynamic field). Equations describing the relationship between flow rate, molecular shape and scattered intensity are given, and theoretical intensity patterns for some representative cases are presented. It follows that there is a fundamental difference in scattering patterns for oblate and prolate ellipsoids of revolution. This difference can be used to differentiate between these two cases. Some experimental results obtained using inorganic model colloids are presented.
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    A device for accurate single-crystal X-ray diffraction investigations at non-ambient temperatures: 83–1120 K (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 43-50 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A device is described which uses liquid nitrogen to generate a cold or hot gas stream which is blown directly onto the crystal mounted on an X-ray diffractometer. With a specially constructed high-vacuum (〈 1.3 × 10–5 Pa) jacketed silica Dewar tube, it can operate between 83 and 1120 K with a stability over long time periods of ± ¼ K below and ± 1 K above ambient temperature. In the latter case the short-time stability is ± ¼ K for hours. It gives an inert atmosphere at elevated temperatures and allows extensive data collection for the accurate determination of crystal structures. The evaporator, the automatic refilling system and the silica Dewar tube are described.
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    A fitting method for X-ray diffraction profiles (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 60-61 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A fitting method is proposed for X-ray diffraction profiles which requires only a small number of parameters.
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    Crystal data for two series of solid solutions: (RbxK1−x)MgCr2(VO4)3 and (TlxK1−x)MgCr2(VO4)3 (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 61-62 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Complete solid solution is observed amongst the compounds of the type M1MgCr2(VO4)3 (where M1 = K, Rb or Tl). The solid-solution series obtained show linear changes in peak positions and peak intensities in their X-ray diffraction patterns. The crystallographic behaviour with respect to the value of x for (RbxK1−xMgCr2(VO4)3 and (TlxK1−x)MgCr2(VO4)3 solid solutions is discussed.
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    Crystal data for ferric molybdate: Fe2(MoO4)3 (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 64-65 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Indexed powder patterns of the monoclinic phase, stable at room temperature, and of the orthorhombic phase, stable for T 〉 786 K, are given. The cell dimensions are: a = 15.737 (8), b = 9.231 (5), c = 18.224 (9) Å, β = 125.46 (2)° at 295 K; a = 9.330 (3), b = 12.868 (5), c = 9.242 (3) Å at 818.6 K. Linear equations describing the thermal expansion of the two phases of ferric molybdate are reported. To verify if ferric molybdate can incorporate excess MoO3, measurements on non-stoichiometric samples were also made: no evidence of the presence of excess MoO3 was found.
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    Crystal data for high-temperature As2O5 (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 68-68 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: High-temperature As2O5 at 768 ± 5 K is tetragonal with a = 8.577 (1), c = 4.637 (1) Å, V = 341.2 Å3, Z = 4, Dc = 4.475 Mg m−3. Indexed powder data are given.
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    BLOKJE, a computer program to calculate the domain of an atom in a structure (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 151-153 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A computer program has been written with the aim of calculating the domain of an atom in a structure. The domain may be limited by planes situated half-way between the atoms, or at a distance that takes into account the relative radii of the atoms. Data concerning this domain and the corresponding coordination polyhedron are computed and printed. Punched cards, to be used in a special plotting program, can also be produced. Three types of weighted coordination number are calculated.
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    Optical transforms of disordered molecular crystals (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 244-251 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: An Optronics P-1700 film-writing device is used to produce simulations of disordered organic molecular crystals. The simulations may be used directly to obtain optical diffraction patterns for comparison with X-ray diffuse scattering photographs of real crystals. Examples of some substituted anthracenes are given to demonstrate the diversity of disorder effects which may be included and the level of precision achieved.
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    URL: http://dx.doi.org/10.1107/S0021889880012009
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    The asymmetrically cut Bonse–Hart X-ray diffractometer. II. Comparison with the Kratky camera (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 256-258 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The asymmetrically cut, optimized BH diffractometer for small-angle X-ray scattering experiments is compared with the Kratky camera. It is shown that a crossover point exists in the resolution so that at a lower resolution the Kratky camera is superior and at a higher resolution the BH system is preferable. The crossover point depends on the number of reflections used. Methods of reducing the spurious signal and increasing the S/N ratio of the BH system are also discussed.
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    An estimate of the surface roughness effect (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 219-222 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A method for the computation of the effect of rough sample surfaces on diffraction intensities is described. Though the model used for the calculation is a special simple one, it is exact. The method is illustrated by its application to a surface whose boundary is a saw-tooth. Possible generalizations of the character of the surface roughness effect and how it depends on the dimensions of the surface irregularities are inferred from the calculation.
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    Preliminary investigation of a new X-ray film (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 256-260 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A new X-ray film, produced by CEAVERKEN in Sweden, has recently become available. Some properties of this film have been compared to three other films commonly used in the recording of X-ray diffraction intensities (Agfa T4, Kodak No-screen, Ilford Industrial G). The linearity of CEA film has been found to be similar to that for Agfa and Ilford. The speed of the new film is about 10% lower than Agfa or Kodak, and the film factor was measured to be 2.9 for Cu Kα radiation. The background level is significantly lower than on the other three films investigated. This combination of properties makes CEA film suitable for routine collection of X-ray diffraction data.
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    Precipitation and ordering in calcia- and yttria-stabilized zirconia (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 375-379 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Single crystals of ZrO2–15 mol % CaO and ZrO2–9 mol % Y2O3, annealed for either 400 h at 1273 K or 2.5 h at 1673 K and then quenched, were examined by electron diffraction and dark-field transmission electron microscopy. The thermal treatments duplicated those of Faber, Mueller & Cooper [Phys. Rev. B (1978), 17, 4884–4888], who used elastic neutron scattering to investigate fluorite-forbidden reflections which arise from what previous authors have called the `ordered' structure. The present results show that the extra reflections are due to precipitation of tetragonal ZrO2 in both systems. Imaging with the diffuse-scattered intensity also present reveals small domains, presumably associated with oxygen-vacancy ordering, in the cubic solid-solution matrix. The diffuse intensity is observed whether or not tetragonal ZrO2 precipitates are present.
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    Multiple twinning in Co(C15H11OS)3 (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 397-398 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Crystals of tris(3-mercapto-1,3-diphenyl-2-propen-1-onato)cobalt(III), Co(C15H11OS)3, C45H33CoO3S3, are monoclinic, P21/a, a = 19.33, b = 11.02, c = 18.13 Å, all ±0.3%, β = 93°0′±15′; Dobs = 1.346 (5) Mg m−3 at 293 K giving Z = 4 and Dx = 1.338 Mg m−3. Multiple twinning results from fortuitous pseudo-orthorhombic and pseudo-hexagonal (a/b ∼√3) twin-lattice symmetry around c[001].
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    Crystal data for Lu2Si2O7 (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 349-350 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Lutetium pyrosilicate single crystals Lu2Si2O7 were grown by a floating-zone technique associated with an arc image furnace. The compound is monoclinic, space group C2/m, Z = 2, a = 6.7665 (14), b = 8.8407 (18), c = 4.7195 (27) Å and β = 101.95 (3)°. Indexed X-ray powder data at 294 K are given.
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    Crystallographers (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 353-354 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
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    Revised crystal data of BaZnGeO4 (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 400-401 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: Transparent and colourless single crystals of BaZnGeO4 were grown by the Czochralski pulling method. Chemical analysis showed that the crystal composition was very close to stoichiometry. The unit cell is hexagonal with a = 9.297 (1) and c = 35.284 (2) Å. These are √3 and 4 times larger for a and c, respectively, than the already reported ones. D293 is 5.144 and Dx is 5.140 Mg m−3 for Z = 24. The most probable space group is P63. Indexed powder data and some physical properties are given.
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    The measurement of the X-ray scattering factors of silicon from the fine structure of Laue-case rocking curves (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 410-416 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Laue-case rocking curves of a pair of crystals with nearly equal thickness display a detailed fine structure which is shown to be very suited to the determination of precise values of the atomic scattering factor fg. Preliminary data thus obtained are f440 (AgKα) = 5.377 (15) and f440 (Mo Kα) = 5.402 (18) for silicon at 293 K. They agree well with the more precise data obtained in the past with the Pendellösung method using wedge-shaped crystals [Aldred & Hart (1973). Proc. R. Soc. London Ser. A, 332, 223–238]. The strength and the advantages of the new method are discussed. With proper optimization the rocking-curve method is assumed to measure fg values with errors less than 0.1%.
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    A study of the ordered structures of the Au–Mn system by high-voltage–high-resolution electron microscopy. II. Two-dimensional antiphase structures based on the DO22 structure (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 392-400 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: Two-dimensional antiphase domain structures existing in the composition range 20–23 at.% Mn were investigated by a high-resolution structure-imaging technique with a 1 MV electron microscope. The structures are based on the DO22 structure and consist of parallelogram-shaped domains containing 4 × 3 columns of Mn atoms and lozenge-shaped domains with 4 × 4 and 3 × 3 columns, and the domains are separated by two-dimensional antiphase boundaries parallel to the ({\bar 2}40) and (240) planes of the fundamental face-centred structure. The configuration of the domains changes delicately with a slight change of composition or annealing temperature, and the symmetry of the structure is lowered below about 670 K. The ideal structure models have compositions of about 22.7 at.% Mn. The images of about half of the specimen area of the 22.6 at.% Mn alloy annealed at 570 K do not correspond to these new structures, but bear a resemblance to the image expected from the two-dimensional antiphase structure proposed by Watanabe [J. Phys. Soc. Jpn (1960), 15, 1030–1040] for Au3Mn, which is based on the L12 structure and has boundaries parallel to the (100) and (010) planes.
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    Crystallographers (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 462-462 
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    Scanning electron microscopy/1979. Parts I and II edited by O. Johari (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 463-464 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Optimization of quantitative X-ray diffraction analysis (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 479-485 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: Very little emphasis is generally given to the reliability of the concentrations obtained by the methods of X-ray diffraction phase analysis. Thus the statistical accuracy of the results is not or only vaguely known. The related optimization problem of choosing the precision of measurement of the diffraction peaks in such a manner that the concentrations of required accuracy be obtained in a minimum time is unsolved in the literature. Owing to the lack of this optimization, the time spent on the diffraction measurements is usually much larger than the accuracy of the results would substantiate. The optimization is elaborated in the present paper. The resulting procedure to be followed is conceptually simple and of general applicability. A computer program has been developed for carrying out all calculations.
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    Détermination précise de la composition de couches epitaxiées Ga1−xInxP (0≤x≤0,10) (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 513-515 
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    Notes: The chemical composition of Ga1−xInxP (0 ≤ x ≤ 0.10) alloys epitaxically grown on GaP substrates has been determined by electron microprobe analysis and by lattice-parameter measurement (a). The a(x) calibration curve follows Vegard's law which confirms the regular character of the solid solution and the existence of strain relaxation in the epitaxic layers.
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    Report of the Executive Committee for 1979 (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 635-635 
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    Current topics in materials science. Vol. 3 edited by E. Kaldis (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 636-637 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Polymorphism of malononitrile. Crystallographic characterization of the L–F phase transition (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 1-2 
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    Notes: The L-F phase transition of malononitrile, CH2(CN)2, has been characterized by powder X-ray diffraction analysis. The powder data of L and F phases are given. Crystallographic results are consistent with spectroscopic and calorimetric ones which indicate that this transition is of first order and corresponds to a reconstructive mechanism.
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    Precise lattice parameter determination of PtHg4 (1982)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 15 (1982), S. 100-101 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: The lattice parameter of cubic PtHg4 at 298 K is 6.2001 Å and it is accurate to better than 1 part in 10000.
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    HELP: a Fortran V computer program for obtaining the Cartesian coordinates of a single molecule from its chemical formula (1982)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 15 (1982), S. 129-132 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
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    Notes: A Fortran V computer program for obtaining the atomic coordinates of a single molecule from its chemical formula is presented. The program has been tested in a UNIVAC 1100 computer. The program assigns a Cartesian system to each skeletal bond and assigns each atom to its proper Cartesian system. The program lists the various types of bonds of each atom and, given the torsion angles, computes the conformation of the whole molecule. Torsion angle and atom numbering is automated by the program. Cyclic structures can also be represented. At present molecules containing hydrogen, carbon, oxygen, phosphorus, nitrogen, sulfur, silicon and halogen atoms can be represented.
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    Asbestos. Vol. 1. Final report of the Advisory Committee; Vol. 2. Papers prepared for the Advisory Committee (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 77-78 
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    A cell model for X-ray scattering from random systems (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 309-314 
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    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A model, belonging to the class of cell models previously introduced, is developed to calculate the small-angle X-ray scattering of random multiphase systems. This model, which is applied to supported metal catalysts, involves two cell sizes, one for the support and one for the metal. Interphase surface areas and the correlation function, related to the X-ray scattering intensity by a Fourier transform, are given in terms of these two parameters. By fitting the measured intensity I(h) to that predicted by the model, values for the metal and support surface areas are obtained.
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    Use of a single-stage, closed-cycle cryorefrigerator for routine measurements at moderately low temperatures on a four-circle neutron diffractometer (1981)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 14 (1981), S. 326-328 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A single-stage closed-cycle helium cryorefrigerator has been installed on a conventional four-circle neutron diffractometer. The cold head together with a specially designed support and alignment unit are sufficiently compact to enable it to be mounted directly onto the φ rotation table within the χ circle in place of the normal goniometer head used for room-temperature experiments. The device has a temperature range of 50 to 300 K, is extremely simple to use, and has a low operation cost as no cryogenic liquids are consumed. There are additional restrictions on the diffractometer angles but, with care, it is possible to measure at least half the reciprocal sphere.
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    URL: http://dx.doi.org/10.1107/S0021889881009473
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  • 81
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    Interactive dynamic molecular display (1982)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 15 (1982), S. 467-468 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A program is described to allow the dynamic graphic manipulation of molecules on a Tektronix 4054 graphics system. The program is useful for structure examination during X-ray crystal structure solution and for visualizing the results of structure determinations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889882012394
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  • 82
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    The forward scattering of cold neutrons by mixtures of light and heavy water (1982)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 15 (1982), S. 15-19 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The forward scattering of cold neutrons in small-angle scattering experiments on macromolecules dissolved in mixtures of light and heavy water is predominantly determined by the large incoherent cross section of the hydrogen atoms leading to an isotropic background level. The probability per unit solid angle for forward scattering by samples rich in H2O is approximately equal to the fraction of the primary beam which has not been transmitted through the sample, divided by the full solid angle 4π. When using the camera D11 at the high flux reactor in Grenoble [Ibel (1976). J. Appl. Cryst. 9, 296–309] this simple relation is fulfilled within ±5% by a 1 mm thick sample of H2O at 281.8 K using neutrons of 1.0 nm wavelength. In D2O, the coherent cross section is of the same order as the incoherent one, and about one half of all those neutrons which had been removed from the primary beam are scattered into large angles. Our experimental results and the derived graphs allow us to determine the effective forward scattering per unit solid angle for any volume fraction of D2O in H2O/D2O mixtures around room temperature by a simple and accurate transmission experiment in conjunction with the measurement of the scattering of one single sample of H2O of 1 mm thickness, for neutrons of wavelengths from 0.45 to 1.0 nm.
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    A new CeO2 form obtained as oxidation product of CeO2+SiO2-doped hot-pressed silicon nitride (1982)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 15 (1982), S. 55-59 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: By using data from the Wallace & Ward [J. Appl. Cryst. (1975), 8, 255–260] cylindrical texture camera integrated with other traditional X-ray powder film techniques for very low and very high diffraction angles, a new high-temperature modification of CeO2 was identified and indexed resulting in a trigonal or hexagonal unit cell with a = 8.36(2) and c = 10.42(2) Å, (axial ratio 1.264) and Z = 16. The new phase is an oxidation product of CeO2-doped hot-pressed silicon nitride. It can be quenched to room temperature under appropriate conditions. Its stability on reheating is strictly related to its interaction with the silicate phase.
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    A simple method for the determination of structure-factor phase relationships and crystal polarity using electron diffraction (1982)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 15 (1982), S. 60-64 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Multiple electron scattering between weak beams has been used as the basis for a simple method to determine the absolute polarity of some non-centrosymmetric crystals. For crystals with the sphalerite structure many orientations have been found in which small departures from centrosymmetry produce large effects on the convergent-beam diffraction patterns (microdiffraction). The effects are reasonably independent of thickness and so can be analyzed qualitatively without the use of computers.
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  • 85
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    Refinement of the crystal orientation matrix for the flat-cone diffractometer (1982)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 15 (1982), S. 79-81 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A procedure for refining a crystal orientation matrix for the flat-cone diffractometer is discussed. The positions of the centers of gravity of refections obtained during routine data collection are transformed in such a way that they can be used as input to the least-squares procedures of Busing & Levy [Acta Cryst. (1967), 22, 457–464] or Shoemaker & Bassi [Acta Cryst. (1970), A26, 97–101]. The orientation matrix can be refined on the basis of the positions of all observed reflections, and not only of a selected sample, thus increasing its reliability. The procedure is particularly suited for protein crystallographic studies, as it makes it possible to compensate for crystal movements encountered during data collection.
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  • 86
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    The resolving capability of the NaI(Tl) scintillation detector (1982)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 15 (1982), S. 98-99 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Attention is drawn to the influence of high quantal flux on the resolving capability of the scintillation detector.
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  • 87
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    A comment on attenuator factors and the dead time of counter systems (1982)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 15 (1982), S. 99-100 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Attenuator factors are functionally dependent on X-ray flux when dead time is ignored. The combination of this effect with counting losses downgrades diffracted intensity progressively with increasing intensity and is therefore liable to be confused with the effect of extinction. It can have a significant influence on the accuracy of the resultant structure factors. Estimation and elimination of this error source is straightforward.
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  • 88
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    Paramètres, groupe d'espace et diagramme de poudre de l'amino-2 thiazole-1,3 (1982)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 15 (1982), S. 106-107 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The title compound, C3H4N2S, crystallizes in the orthorhombic system, space group Pbca. The cell constants are determined from a single crystal: a = 9,62 ± 0,02, b = 5,90 ± 0,01 and c = 15,59 ± 0,03 Å. X-ray powder diffraction data are given.
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  • 89
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    An X-ray diffraction study of the system Al2S3–In2S3 in the In-rich region (1982)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 15 (1982), S. 107-111 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A series of samples in the system Al2S3–In2S3 in the In-rich region have been synthesized and studied by X-ray diffraction. At the lowest values of the Al/In (molar) ratio, r, the existing phase, β, is isostructural with the room-temperature, ordered, tetragonal phase of In2S3. As the Al content increases a progressive disorder of cations takes place. For r≳l/10 this disorder is completed and β is replaced with a phase, denoted as α, which is isostructural with the first high-temperature, cubic, phase of In2S3. The unit-cell parameters of the ternary β and α alloys, (AlxIn1 − x)2S3, decrease linearly as the Al content increases. From r≳1/3 to r ̃2/3 there is a two-phase region, α + γ1. The hexagonal phase γ1 is isostructural with AlInS3, appearing at r = 1, and with the second high-temperature, γ, modification of In2Se3. The phase γ1 also exists in the systems Ga2Se3–In2Se3 and Al2Se3–In2Se3 in the In-rich region for the (Ga, Al)/In (molar) ratio greater than ̃1/50.
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    Notes and News (1982)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 15 (1982), S. 577-578 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
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    Mössbauer spectroscopy and its chemical applications edited by J. G. Stevens and G. K. Shenoy (1982)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 15 (1982), S. 579-579 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
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    Neutron transmutation doped silicon edited by J. Guldberg (1982)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 15 (1982), S. 579-580 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
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    URL: http://dx.doi.org/10.1107/S0021889882012709
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    Rietveld refinement with spallation neutron powder diffraction data (1982)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 15 (1982), S. 581-589 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The mathematical functions necessary for Rietveld refinement of time-of-flight neutron powder diffraction patterns from spallation sources are developed and a computer program for least-squares analysis is described. The results of Rietveld refinements of nickel and a low-carbon steel are described and discussed. The method fully exploits the high resolution (Δd/d ̃0.3 ̃0.5%) available with powder diffractometers currently in operation on these sources and examples are given of precise determination of atom coordinates, thermal parameters, lattice parameters and the detection of small strains.
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    Notes and News (1982)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 15 (1982), S. 639-639 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
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    Current Crystallographic Books 1970 through 1981 (1982)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 15 (1982), S. 640-676 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
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    Etude microstructurale de carbures M7C3 (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 1-10 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Three cells with trigonal, orthorhombic or hexagonal symmetry have been proposed to describe M7C3 carbides. Examinations of heavily faulted chromium, iron, vanadium mixed carbides present in white cast irons and in chromium steels have been performed by means of electron microscopy and diffraction. Electron diffraction patterns of the first-order Laue zone have been obtained with crystals having their c axis nearly parallel to the electron beam. They contain reflections which are typical of the symmetry and streaks which are typical of the faults. This original method of examination has systematically been applied to numerous carbides and comparisons of these experimental patterns with theoretical patterns expected from models which view the three structures of M7C3 carbides as three different superlattices of a hypothetical disordered lattice lead to the following two main results: the structure of these carbides is well described with the orthorhombic cell previously given by Fruchart, Senateur, Bouchard & Michel [C.R. Acad. Sci. (1965), 260, 913]; the planar faults, which are often periodic, are antiphase boundaries or twins with fault planes {10{\bar 1}0} and fault vectors R = a, b or a + b.
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  • 97
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    Kα2 elimination algorithm for Cu, Co and Cr radiations (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 24-27 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: It is well known that the extraneous Kα2 line complicates the interpretation of X-ray diffraction spectra. Experience has shown that the arms and weights calculated by Ladell's method [Laddell, Parrish & Taylor (1959). Acta Cryst. 12, 561–567] have to be determined for each user's X-ray diffractometer, rather than using the published coefficients, for an accurate Kα2 elimination. When different materials are analyzed, the signal/noise ratio can be optimized by choosing a suitable target material. Kα2 correction coefficients have been calculated for Cu, Co and Cr radiations using a fast Fourier calculation method.
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  • 98
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    X-ray topography of natural beryl using synchrotron and conventional sources (1983)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 47-56 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Continuous-spectrum synchrotron-radiation Laue transmission topographs of natural beryl have been compared with the corresponding projection topographs taken with conventional apparatus and Cu Kα1 and Mo Kα1 radiations in an analysis of configurations of grown-in lattice defects and of the diffraction contrast they produce. The natural defects studied included grown-in dislocations, impurity zoning and fault surfaces. A growth-sector map was constructed for the (0001) specimen slice examined. Differences of contrast among the various reflections appearing on the synchrotron-radiation topographs are discussed and it is demonstrated that the contrast characteristics of the synchrotron-radiation images which consist of a superimposition of 3{\bar 2\bar 1}1 and 6{\bar 4 \bar 2}2 reflections can be satisfactorily synthesized by a weighted superimposition of the 3{\bar 21}1 image recorded with Cu Kα1 and the 6{\bar 4\bar 2}2 with Mo Kα1. Synchrotron-radiation damage to the crystal manifested itself on the X-ray topographs both as area contrast and as contrast at the periphery of the irradiated area, yet no visual absorption or birefringence due to this damage was detected. Annealing at 770 K for 3 h completely removed the contrast due to radiation damage.
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    Molecular Structures and Dimensions (1982)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 15 (1982), S. 250-250 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
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    URL: http://dx.doi.org/10.1107/S0021889882011911
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    The derivation of the axes of the conventional unit cell from the dimensions of the Buerger-reduced cell (1982)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 15 (1982), S. 255-259 
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    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The identification of twofold axes is straightforward if the cell is based on three of the shortest lattice translations. The distribution of twofold axes in space fixes the lattice symmetry and most conventional cell edges. A program based on this approach has been written. It works for the seven cases with minimum branching of the algorithm.
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