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  • 1
    Publication Date: 2022-05-25
    Description: © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Geophysical Research: Oceans 120 (2015): 5932–5944, doi:10.1002/2015JC010914.
    Description: The observed changes in physical properties of sea ice such as decreased thickness and increased melt pond cover severely impact the energy budget of Arctic sea ice. Increased light transmission leads to increased deposition of solar energy in the upper ocean and thus plays a crucial role for amount and timing of sea-ice-melt and under-ice primary production. Recent developments in underwater technology provide new opportunities to study light transmission below the largely inaccessible underside of sea ice. We measured spectral under-ice radiance and irradiance using the new Nereid Under-Ice (NUI) underwater robotic vehicle, during a cruise of the R/V Polarstern to 83°N 6°W in the Arctic Ocean in July 2014. NUI is a next generation hybrid remotely operated vehicle (H-ROV) designed for both remotely piloted and autonomous surveys underneath land-fast and moving sea ice. Here we present results from one of the first comprehensive scientific dives of NUI employing its interdisciplinary sensor suite. We combine under-ice optical measurements with three dimensional under-ice topography (multibeam sonar) and aerial images of the surface conditions. We investigate the influence of spatially varying ice-thickness and surface properties on the spatial variability of light transmittance during summer. Our results show that surface properties such as melt ponds dominate the spatial distribution of the under-ice light field on small scales (〈1000 m2), while sea ice-thickness is the most important predictor for light transmission on larger scales. In addition, we propose the use of an algorithm to obtain histograms of light transmission from distributions of sea ice thickness and surface albedo.
    Description: U.S. National Science Foundation Office of Polar Programs NSF OPP ANT-1126311, National Oceanic and Atmospheric Administration Office of Exploration and Research NOAA OER NA14OAR4320158, European Research Council Advanced Investigator Grant Number: 294757
    Keywords: Melt ponds ; Light transmittance ; Albedo ; ROV ; Spatial variability ; Shortwave radiation
    Repository Name: Woods Hole Open Access Server
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  • 2
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 21 (2006): PA3012, doi:10.1029/2006PA001273.
    Description: Geochemical compositions and Sr and Nd isotopes were measured in two cores collected ~2 and 5 km from the Rainbow hydrothermal vent site on the Mid-Atlantic Ridge. Overall, the cores record enrichments in Fe and other metals from hydrothermal fallout, but sequential dissolution of the sediments allows discrimination between a leach phase (easily leachable) and a residue phase (refractory). The oxy-anion and transition metal distribution combined with rare earth element (REE) patterns suggest that 1) the leach fraction is a mixture of biogenic carbonate and hydrothermal Fe-Mn oxy-hydroxide with no significant contribution from detrital material, and 2) 〉99.5% of the REE content of the leach fraction is of seawater origin. In addition, the leach fraction has an average 87Sr/86Sr ratio indistinguishable from modern seawater at 0.70916. Although we lack the εNd value of present day deep water at the Rainbow vent site, we believe that the REE budget of the leach fraction is predominantly of seawater origin. We suggest, therefore, that the leach fraction provides a record of local seawater εNd values. Nd isotope data from these cores span the period of 4-14 ka (14C ages) and yield εNd values for North East Atlantic Deep Water (NEADW) that are higher (-9.3 to -11.1) than those observed in the nearby Madeira Abyssal Plain from the same depth (-12.4 ± 0.9). This observation suggests that either the Iceland-Scotland Overflow Water (ISOW) and Lower Deep Water (LDW) contributions to the formation of NEADW are higher along the Mid-Atlantic Ridge than in the surrounding basins, or that the relative proportion of ISOW was higher during this period than is observed today. This study indicates that hydrothermal sediments have the potential to provide a higher resolution record of deep water εNd values, and hence deep-water circulation patterns in the oceans, than is possible from other types of sediments.
    Description: VC is funded by the 2000 National Oceanography Centre, Southampton fellowship. Hydrothermal research at NOCS is funded through NERC core strategic science.
    Keywords: Nd isotope ; Hydrothermal ; Seawater
    Repository Name: Woods Hole Open Access Server
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  • 3
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 7 (2006): Q11022, doi:10.1029/2006GC001324.
    Description: We report evidence for active hydrothermal venting along two back-arc spreading centers of the NE Lau Basin: the Fonualei Rift and Spreading Center (FRSC) and the Northeast Lau Spreading Center (NELSC). The ridge segments investigated here are of particular interest as the potential source of a mid-water hydrothermal plume (1500–2000 m depth) which extends more than 2000 km across the SW Pacific Ocean dispersing away from an apparent origin close to the most northeastern limits of the Lau Basin. Our results indicate the presence of at least four new hydrothermal plume sources, three along the FRSC and one on the NELSC, the latter situated within 150 km of the maximum for the previously identified SW Pacific regional-scale plume. However, TDFe and TDMn concentrations in the southernmost FRSC plume that we have identified only reach values of 19 and 13 nmol/L and dissolved 3He anomalies in the same plume are also small, both in relation to the SW Pacific plume and to local background, which shows evidence for extensive 3He enrichment throughout the entire Lau Basin water column. Our results reveal no evidence for a single major point hydrothermal source anywhere in the NE Lau Basin. Instead, we conclude that the regional-scale SW Pacific hydrothermal plume most probably results from the cumulative hydrothermal output of the entire topographically restricted Lau Basin, discharging via its NE-most corner.
    Description: This research was funded jointly by NSF's Ridge 2000 Program (OCE-0242002 and OCE-0242618), by the NOAA Vents Program, and by core strategic funding from the Natural Environment Research Council to the National Oceanography Centre, Southampton (UK).
    Keywords: Hydrothermal ; Exploration ; Lau Basin ; SW Pacific
    Repository Name: Woods Hole Open Access Server
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  • 4
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 8 (2007): Q08013, doi:10.1029/2007GC001652.
    Description: We report first evidence for hydrothermal activity from the southern Knipovich Ridge, an ultra-slow spreading ridge segment in the Norwegian-Greenland Sea. Evidence comes from optical backscatter anomalies collected during a systematic side-scan sonar survey of the ridge axis, augmented by the identification of biogeochemical tracers in the overlying water column that are diagnostic of hydrothermal plume discharge (Mn, CH4, ATP). Analysis of coregistered geologic and oceanographic data reveals that the signals we have identified are consistent with a single high-temperature hydrothermal source, located distant from any of the axial volcanic centers that define second-order segmentation along this oblique ridge system. Rather, our data indicate a hydrothermal source associated with highly tectonized seafloor that may be indicative of serpentinizing ultramafic outcrops. Consistent with this hypothesis, the hydrothermal plume signals we have detected exhibit a high methane to manganese ratio of 2–3:1. This is higher than that typical of volcanically hosted vent sites and provides further evidence that the source of the plume signals reported here is most probably a high-temperature hydrothermal field that experiences some ultramafic influence (compare to Rainbow and Logachev sites, Mid-Atlantic Ridge). While such sites have previously been invoked to be common on the SW Indian Ridge, this may be the first such site to be located along the Arctic ultra-slow spreading ridge system.
    Description: Connelly and German were funded by NERC grant NER/B/S/ 2000/00755, NERC Core Strategic Funding at NOC, and the ChEss project of the Census of Marine Life.
    Keywords: Hydrothermal ; Arctic ; Serpentinization ; Knipovich Ridge
    Repository Name: Woods Hole Open Access Server
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  • 5
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2009. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 10 (2009): Q05T05, doi:10.1029/2008GC002314.
    Description: This paper demonstrates that a Raman spectroscopy, point-counting technique can be used for phase analysis of minerals commonly found in deep-sea hydrothermal plumes, even for minerals with similar chemical compositions. It also presents our robust autonomous identification algorithm and spectral database, both of which were developed specifically for deep-sea hydrothermal studies. The Raman spectroscopy expert algorithm was developed and tested against multicomponent mixtures of minerals relevant to the deep-sea hydrothermal environment. It is intended for autonomous classification where many spectra must be examined with little or no human involvement to increase analytic precision, accuracy, and data volume or to enable in situ measurements and experimentation.
    Description: Support for J.A.B. was provided through a RIDGE 2000 Postdoctoral Fellowship (NSF OCE-0550331).
    Keywords: Hydrothermal ; Mineralogy ; Optical instruments ; Raman spectroscopy ; Analytic techniques ; Chemical sensor
    Repository Name: Woods Hole Open Access Server
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  • 6
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 14 (2013): 317–327, doi:10.1002/ggge.20063.
    Description: Deep-sea ultramafic-hosted vent systems have the potential to provide large amounts of metabolic energy to both autotrophic and heterotrophic microorganisms in their dispersing hydrothermal plumes. Such vent-systems release large quantities of hydrogen and methane to the water column, both of which can be exploited by autotrophic microorganisms. Carbon cycling in these hydrothermal plumes may, therefore, have an important influence on open-ocean biogeochemistry. In this study, we investigated an ultramafic-hosted system on the Mid-Cayman Rise, emitting metal-poor and hydrogen sulfide-, methane-, and hydrogen-rich hydrothermal fluids. Total organic carbon concentrations in the plume ranged between 42.1 and 51.1 μM (background = 43.2 ± 0.7 μM (n = 5)) and near-field plume samples with elevated methane concentrations imply the presence of chemoautotrophic primary production and in particular methanotrophy. In parts of the plume characterized by persistent potential temperature anomalies but lacking elevated methane concentrations, we found elevated organic carbon concentrations of up to 51.1 μM, most likely resulting from the presence of heterotrophic communities, their extracellular products and vent larvae. Elevated carbon concentrations up to 47.4 μM were detected even in far-field plume samples. Within the Von Damm hydrothermal plume, we have used our data to hypothesize a microbial food web in which chemoautotrophy supports a heterotrophic community of microorganisms. Such an active microbial food web would provide a source of labile organic carbon to the deep ocean that should be considered in any future studies evaluating sources and sinks of carbon from hydrothermal venting to the deep ocean.
    Description: The research reported in this paper was supported by ship time and support provided by NOAA’s Office of Ocean Exploration and Research and the Office of Marine and Aviation Operations and NSF’s Division of Ocean Sciences (Grant OCE-1061863) and by further shore-based research from both the National Science Foundation (NSF OCE-1061863) and NASA’s ASTEP Program (Grant # NNX09AB75G). The contributions of SB and MC were carried out at the Jet Propulsion Laboratory (JPL), California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA), with support from the NASA ASTEP Program.
    Description: 2013-08-22
    Keywords: Hydrothermal ; Food web ; Microorganisms ; Plume ; Carbon ; Ultramafic
    Repository Name: Woods Hole Open Access Server
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  • 7
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2006. 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 33 (2006): L10608, doi:10.1029/2006GL026048.
    Description: About 90% of Earth's volcanism occurs along the global mid-ocean ridge system. Here, sporadic volcanic and tectonic activity is thought to cause cataclysmic release of hydrothermal fluids, forming event plumes. Each plume often contains as much hydrothermal effluent and heat as chronic hydrothermal venting from a typical vent site discharges during a year. To date, only a few event plumes have been detected, and only above intermediate-rate spreading ridges in the Pacific. Here, we report the first evidence for an unusually large event plume that originated from the slow-spreading (3 cm/yr full-rate) Carlsberg Ridge in the NW Indian Ocean. At 70 km long, up to 4540 km3 in volume and with up to 24 × 1016 J of excess heat, this event plume was substantially larger than previous ones and demonstrates that dispersion of hydrothermal heat and biological products from slow spreading ridges may be more significant and effective than hitherto imagined.
    Description: This work was supported by the Natural Environment Research Council, UK; the National Oceanography Centre, Southampton (NOCS); the NOAA Vents Program.
    Repository Name: Woods Hole Open Access Server
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  • 8
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 14 (2013): 4892–4905, doi:10.1002/2013GC004998.
    Description: The InterRidge Vents Database is available online as the authoritative reference for locations of active submarine hydrothermal vent fields. Here we describe the revision of the database to an open source content management system and conduct a meta-analysis of the global distribution of known active vent fields. The number of known active vent fields has almost doubled in the past decade (521 as of year 2009), with about half visually confirmed and others inferred active from physical and chemical clues. Although previously known mainly from mid-ocean ridges (MORs), active vent fields at MORs now comprise only half of the total known, with about a quarter each now known at volcanic arcs and back-arc spreading centers. Discoveries in arc and back-arc settings resulted in an increase in known vent fields within exclusive economic zones, consequently reducing the proportion known in high seas to one third. The increase in known vent fields reflects a number of factors, including increased national and commercial interests in seafloor hydrothermal deposits as mineral resources. The purpose of the database now extends beyond academic research and education and into marine policy and management, with at least 18% of known vent fields in areas granted or pending applications for mineral prospecting and 8% in marine protected areas.
    Description: For support to prepare this manuscript, we thank the National Science Foundation (OCE08-38923, GeoEd12-02977), the NOAA Vents (now Earth-Ocean Interactions) Program and the Joint Institute for the Study of the Atmosphere and Ocean (JISAO) under NOAA Cooperative Agreement NA10OAR4320148, and WHOI.
    Description: 2014-05-19
    Keywords: Hydrothermal vent ; Deep-sea vent ; Hydrothermal activity ; Drupal
    Repository Name: Woods Hole Open Access Server
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  • 9
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 16 (2015): 2762–2774, doi:10.1002/2015GC005831.
    Description: Processes active in rising hydrothermal plumes, such as precipitation, particle aggregation, and biological growth, affect particle size distributions and can exert important influences on the biogeochemical impact of submarine venting of iron to the oceans and their sediments. However, observations to date of particle size distribution within these systems are both limited and conflicting. In a novel buoyant hydrothermal plume study at the recently discovered high-temperature (398°C) Piccard Hydrothermal Field, Mid-Cayman Rise, we report optical measurements of particle size distributions (PSDs). We describe the plume PSD in terms of a simple, power-law model commonly used in studies of upper and coastal ocean particle dynamics. Observed PSD slopes, derived from spectral beam attenuation and laser diffraction measurements, are among the highest found to date anywhere in the ocean and ranged from 2.9 to 8.5. Beam attenuation at 650 nm ranged from near zero to a rarely observed maximum of 192 m−1 at 3.5 m above the vent. We did not find large (〉100 μm) particles that would settle rapidly to the sediments. Instead, beam attenuation was well-correlated to total iron, suggesting the first-order importance of particle dilution, rather than precipitation or dissolution, in the rising plume at Piccard. Our observations at Piccard caution against the assumption of rapid deposition of hydrothermal, particulate metal fluxes, and illustrate the need for more particle size and composition measurements across a broader range of sites, globally.
    Description: This work was funded by the National Science Foundation (OCE-1029223; OCE-1061863), NASA (NNX09AB75G) and Woods Hole Oceanographic Institution's Deep Ocean Exploration Institute and Ocean Ridge Initiative. Ship time (R/V Falkor cruise FK008) was funded by the Schmidt Ocean Institute and M.L.E. was supported by a WHOI Postdoctoral Scholar fellowship.
    Description: 2016-02-25
    Keywords: Hydrothermal particulate iron fluxes ; Particle size distribution ; Particle inherent optical properties ; In situ optical sensors ; Mid-Cayman Rise ; Piccard Hydrothermal Field
    Repository Name: Woods Hole Open Access Server
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  • 10
    Publication Date: 2022-10-26
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in German, C., Baumberger, T., Lilley, M., Lupton, J., Noble, A., Saito, M., Thurber, A., & Blackman, D. Hydrothermal exploration of the southern Chile Rise: sediment‐hosted venting at the Chile Triple Junction. Geochemistry Geophysics Geosystems, 23(3), (2022): e2021GC010317, https://doi.org/10.1029/2021gc010317.
    Description: We report results from a hydrothermal plume survey along the southernmost Chile Rise from the Guamblin Fracture Zone to the Chile Triple Junction (CTJ) encompassing two segments (93 km cumulative length) of intermediate spreading-rate mid-ocean ridge axis. Our approach used in situ water column sensing (CTD, optical clarity, redox disequilibrium) coupled with sampling for shipboard and shore based geochemical analyses (δ3He, CH4, total dissolvable iron (TDFe) and manganese, (TDMn)) to explore for evidence of seafloor hydrothermal venting. Across the entire survey, the only location at which evidence for submarine venting was detected was at the southernmost limit to the survey. There, the source of a dispersing hydrothermal plume was located at 46°16.5’S, 75°47.9’W, coincident with the CTJ itself. The plume exhibits anomalies in both δ3He and dissolved CH4 but no enrichments in TDFe or TDMn beyond what can be attributed to resuspension of sediments covering the seafloor where the ridge intersects the Chile margin. These results are indicative of sediment-hosted venting at the CTJ.
    Description: We acknowledge University of California Ship Funds for their support of that shiptime and the NOAA Ocean Exploration and Research Grant NA08OAR4600757 which supported the research presented here. Finally, we thank two anonymous reviewers whose important contributions helped to improve the final version of this paper. This is PMEL contribution number 5341.
    Keywords: Hydrothermal ; Geochemistry ; Chile Rise ; Chile Triple Junction ; Sediment hosted
    Repository Name: Woods Hole Open Access Server
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