Search

Your search keyword '"Seewald, Jeffrey S."' showing total 403 results
Start Over Author "Seewald, Jeffrey S."
403 results on '"Seewald, Jeffrey S."'

4. OCEAN SYSTEM SCIENCE TO INFORM THE EXPLORATION OF OCEAN WORLDS

Author

German, Christopher R., Blackman, Donna K., Fisher, Andrew T., Girguis, Peter R., Hand, Kevin P., Hoehler, Tori M., Huber, Julie A., Marshall, John C., Pietro, Kathryn R., Seewald, Jeffrey S., Shock, Everett L., Sotin, Christophe, Thurnherr, Andreas M., and Toner, Brandy M.

Published
2022

12. Geochemical insights into conditions of vent fluid origin and water-rock interaction over two eruptive cycles at 9° 50´N East Pacific Rise

Author

McDermott, Jill M., primary, Downing, Connor C., additional, Siverand, Jada M., additional, Bibaj, Esmira, additional, Barreyre, Thibaut, additional, Fornari, Daniel J., additional, Parnell-Turner, Ross, additional, Seewald, Jeffrey S., additional, Reeves, Eoghan P., additional, Syverson, Drew D., additional, Hardisty, Dalton S., additional, and Cox, Alysia D., additional

Published
2024
Full Text
View/download PDF

15. Nautilus Field Season Overview

Author

Raineault, Nicole A., Gee, Lindsay, Mayer, Larry, Heffron, Erin, Turchik, Alan, Mittelstaedt, Eric, Hourigan, Thomas, Cormier, Marie-Helene, Baumberger, Tamara, Merle, Susan, Wilkinson, Camilla, Roe, Kevin, Buck, Nathan, Embley, Robert, Seabrook, Sarah, Crawford, Rebecca, Norgard, Tammy, Du Preez, Cherisse, Yakgujanaas, Jaasaljuus, Clarkson, Molly, Chaves, Lais, Rangeley, Robert, Ciraolo, Alessia, Gale, Katie S.P., Haggarty, Dana, Pegg, James, McNicoll, Caroline, Du Preez, Shelton, Jameson, Brett, Leith, Mandy, Juniper, S. Kim, Elliot, Leslie, St Germain, Candice, Whyte, Jennifer, Fundis, Allison, Kane, Renato, Round, Adrian, De Leo, Fabio, Scherwath, Martin, Douglas, Karen, Lacy, Samantha, Soule, Adam, German, Christopher R., Lim, Darlene S.S., Zoeller, Michael, Parcheta, Carolyn, Alanis, Briana, Brier, John A., Chan, Eric, Emerson, David, Garcia, Angela, Huber, Julie A., Nawotniak, Shannon Kobs, Milesi, Vincent, Shields, Ashley, Shock, Everett, Smith, Amy, Seewald, Jeffrey S., Trembath-Reichert, Elizabeth, Mirmalek, Zara, Miller, Matthew J., Cohen, Tamar, Lees, David, Deans, Matthew, Kelley, Christopher, Balbas, Andrea, Wanless, Dorsey, Marsh, Leigh, Wipfler, Rebecca, Bellucci, Lila Ardor, King, Chad, Brown, Jennifer, Ballard, Robert D., Broad, Kenneth, Coleman, Dwight F., and Schmidt, Val

Published
2019

27. Chemical data quantify Deepwater Horizon hydrocarbon flow rate and environmental distribution

Author

Ryerson, Thomas B, Camilli, Richard, Kessler, John D, Kujawinski, Elizabeth B, Reddy, Christopher M, Valentine, David L, Atlas, Elliot, Blake, Donald R, de Gouw, Joost, Meinardi, Simone, Parrish, David D, Peischl, Jeff, Seewald, Jeffrey S, and Warneke, Carsten

Subjects
Earth Sciences, Geochemistry, Gulf of Mexico, deepwater blowout, marine hydrocarbon partitioning, oil spill flow rate
Abstract

Detailed airborne, surface, and subsurface chemical measurements, primarily obtained in May and June 2010, are used to quantify initial hydrocarbon compositions along different transport pathways (i.e., in deep subsurface plumes, in the initial surface slick, and in the atmosphere) during the Deepwater Horizon oil spill. Atmospheric measurements are consistent with a limited area of surfacing oil, with implications for leaked hydrocarbon mass transport and oil drop size distributions. The chemical data further suggest relatively little variation in leaking hydrocarbon composition over time. Although readily soluble hydrocarbons made up ∼25% of the leaking mixture by mass, subsurface chemical data show these compounds made up ∼69% of the deep plume mass; only ∼31% of the deep plume mass was initially transported in the form of trapped oil droplets. Mass flows along individual transport pathways are also derived from atmospheric and subsurface chemical data. Subsurface hydrocarbon composition, dissolved oxygen, and dispersant data are used to assess release of hydrocarbons from the leaking well. We use the chemical measurements to estimate that (7.8 ± 1.9) × 10(6) kg of hydrocarbons leaked on June 10, 2010, directly accounting for roughly three-quarters of the total leaked mass on that day. The average environmental release rate of (10.1 ± 2.0) × 10(6) kg/d derived using atmospheric and subsurface chemical data agrees within uncertainties with the official average leak rate of (10.2 ± 1.0) × 10(6) kg/d derived using physical and optical methods.

Published
2012

33. Evaluation of AUV Search Strategies for the Localization of Hydrothermal Venting

Author

Seewald, Jeffrey S, Hand, Kevin P, Bowen, Andrew D, Chien, Steve, German, Christopher R, Jakuba, Michael V, Xu, Guangyu, Branch, Andrew, and Mason, James C

Abstract

Ocean Worlds represent one of the best chances for the dis- covery of extra-terrestrial life within our own solar system, particularly near sources of hydrothermal venting. To study the oceans on Ocean Worlds will require a new type of mis- sion to penetrate the icy shell, deploy an autonomous under- water vehicle (AUV), and travel potentially hundreds of kilo- both inspired by (Burian et al. 1996). We have improved a meters with minimal contact to Earth based operations teams. previously-developed nested search strategy (Branch et al. To maximize the science return, the AUV would need to be capable of fully autonomously locating and studying scien- tific features of interest. We have developed two strategies to locate sources of hydrothermal venting: a gradient ascent strategy and a greedy transect search strategy. We have im- proved a previously-implemented nested search strategy by adding a vertical search component. Each strategy is tested in a hydrothermal plume dispersion simulation. We compare the effectiveness of each method in this environment.

Published
2020

34. Demonstration of Autonomous Nested Search for Local Maxima using an Unmanned Underwater Vehicle, ICRA Submission

Author

Branch, Andrew, McMahon, James, Xu, Guangyu, Jakuba, Michael V, German, Christopher R, Chien, Steve, Kinsey, James C, Bowen, Andrew D, Hand, Kevin P, and Seewald, Jeffrey S

Abstract

Ocean Worlds represent one of the best chances for extra-terrestrial life in our solar system. A new mission concept must be developed to explore these oceans. This mission would require traversing the 10s of km thick icy shell and releasing a submersible into the ocean below. During the transit of the icy shell and the exploration of the ocean, the vehicle(s) would be out of contact with Earth for weeks or potentially months at a time. During this time the vehicle must have sufficient autonomy to locate and study scientific targets of interest. One such target of interest is hydrothermal venting. We have previously developed an autonomous nested search method to locate and investigate sources of hydrothermal venting by locating local maxima in hydrothermal vent emissions. In this work we demonstrate this approach on board an OceanServer Iver2 AUV in Chesapeake Bay, MD using simulated sensor data from a hydrothermal plume model. This represents the first step towards the deployment of this approach in conditions analogous to those that we might expect on an Ocean World.

Published
2020

37. The influence of near-surface sediment hydrothermalism on the TEX86 tetraether-lipid-based proxy and a new correction for ocean bottom lipid overprinting

Author

Bentley, Jeremy N., Ventura, Gregory T., Walters, Clifford C., Sievert, Stefan M., and Seewald, Jeffrey S.

Subjects
Ecology, Evolution, Behavior and Systematics, Earth-Surface Processes
Abstract

The diversity and relative abundances of tetraether lipids produced by archaea and bacteria in soils and sediments are increasingly used to assess environmental change. For instance, the TetraEther indeX of 86 carbon atoms (TEX86), based on archaeal isoprenoidal glycerol dialkyl glycerol tetraether (iGDGT) lipids, is frequently applied to reconstruct past sea-surface temperatures (SSTs). Yet, it is unknown how the ratio fully responds to environmental and/or geochemical variations and if the produced signals are largely the adaptive response by Thaumarchaeota to oceanographic effects associated with climate or seasonal temperature changes in the upper water column. We present the results of a four push-core transect study of surface sediments collected along an environmental gradient at the Cathedral Hill hydrothermal-vent system in Guaymas Basin, Gulf of California. The transect crosses a region where advecting hydrothermal fluids reach 155 ∘C within the upper 21 cm below the seafloor (cm b.s.f.) close to the vent center to near-ambient conditions at the vent periphery. The recovered iGDGTs closest to the vent center experienced high rates of turnover with up to 94 % of the lipid pool being lost within the upper 21 cm b.s.f. Here, we show that the turnover is non-selective across TEX86 GDGT lipids and does not affect the ratio independently. However, as evident by TEX86 ratios being highly correlated to the Cathedral Hill vent sediment porewater temperatures (R2=0.84), the ratio can be strongly impacted by the combination of severe lipid loss coupled with the addition of in situ iGDGT production from archaeal communities living in the vent sediments. The resulting overprint produces absolute temperature offsets of up to 4 ∘C based on the TEX86H calibration relative to modern climate records of the region. The overprint is also striking given the flux of iGDGTs from the upper water column is estimated to be ∼ 93 % of the combined intact polar lipid (IPL) and core GDGT lipid pool initially deposited on the seafloor. A model to correct the overprint signal using IPLs is therefore presented that can similarly be applied to all near-surface marine sediment systems where calibration models or climate reconstructions are made based on the TEX86 measure.

Published
2022
Full Text
View/download PDF

40. The influence of near-surface sediment hydrothermalism on the TEX86 tetraether-lipid-based proxy and a new correction for ocean bottom lipid overprinting

Author

Bentley, Jeremy N., Ventura, Gregory T., Walters, Clifford C., Sievert, Stefan M., Seewald, Jeffrey S., Bentley, Jeremy N., Ventura, Gregory T., Walters, Clifford C., Sievert, Stefan M., and Seewald, Jeffrey S.

Abstract

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Bentley, J. N., Ventura, G. T., Walters, C. C., Sievert, S. M., & Seewald, J. S. The influence of near-surface sediment hydrothermalism on the TEX86 tetraether-lipid-based proxy and a new correction for ocean bottom lipid overprinting. Biogeosciences, 19(18), (2022): 4459–4477, https://doi.org/10.5194/bg-19-4459-2022., The diversity and relative abundances of tetraether lipids produced by archaea and bacteria in soils and sediments are increasingly used to assess environmental change. For instance, the TetraEther indeX of 86 carbon atoms (TEX86), based on archaeal isoprenoidal glycerol dialkyl glycerol tetraether (iGDGT) lipids, is frequently applied to reconstruct past sea-surface temperatures (SSTs). Yet, it is unknown how the ratio fully responds to environmental and/or geochemical variations and if the produced signals are largely the adaptive response by Thaumarchaeota to oceanographic effects associated with climate or seasonal temperature changes in the upper water column. We present the results of a four push-core transect study of surface sediments collected along an environmental gradient at the Cathedral Hill hydrothermal-vent system in Guaymas Basin, Gulf of California. The transect crosses a region where advecting hydrothermal fluids reach 155 ∘C within the upper 21 cm below the seafloor (cm b.s.f.) close to the vent center to near-ambient conditions at the vent periphery. The recovered iGDGTs closest to the vent center experienced high rates of turnover with up to 94 % of the lipid pool being lost within the upper 21 cm b.s.f. Here, we show that the turnover is non-selective across TEX86 GDGT lipids and does not affect the ratio independently. However, as evident by TEX86 ratios being highly correlated to the Cathedral Hill vent sediment porewater temperatures (R2=0.84), the ratio can be strongly impacted by the combination of severe lipid loss coupled with the addition of in situ iGDGT production from archaeal communities living in the vent sediments. The resulting overprint produces absolute temperature offsets of up to 4 ∘C based on the TEX calibration relative to modern climate records of the region. The overprint is also striking given the flux of iGDGTs from the upper water column is estimated to be ∼ 93 % of the combined intact polar lipid (IPL) and core GDGT, This research has been supported by the Natural Sciences and Engineering Research Council of Canada (grant no. RGPIN-2018-06147; NSERC), NSERC Canada Research Chairs (CRC) program, Canada Foundation for Innovation (CFI; JELF–CRC, John R. Evans Leaders Fund), NSERC Discovery Grants program (application no. RGPIN-2017-05822), Woods Hole Oceanographic Institution (WHOI) Deep Ocean Exploration Initiative 2008, and Natural Science Foundation (grant no. MCB-0702677 to Jeffrey S. Seewald and Stefan M. Sievert; NSF).

Published
2023

41. Mineral carbonation of peridotite fueled by magmatic degassing and melt impregnation in an oceanic transform fault.

Author

Klein, Frieder, Schroeder, Timothy, John, Cédric M., Davis, Simon, Humphris, Susan E., Seewald, Jeffrey S., Sichel, Susanna, Wolfgang Bach, and Brunelli, Daniele

Subjects
PERIDOTITE, CARBONATION (Chemistry), MINERALS, FAULT zones, CARBON cycle, MELT spinning
Abstract

Most of the geologic CO2 entering Earth's atmosphere and oceans is emitted along plate margins. While C-cycling at mid-ocean ridges and subduction zones has been studied for decades, little attention has been paid to degassing of magmatic CO2 and mineral carbonation of mantle rocks in oceanic transform faults. We studied the formation of soapstone (magnesite-talc rock) and other magnesite-bearing assemblages during mineral carbonation of mantle peridotite in the St. Paul's transform fault, equatorial Atlantic. Clumped carbonate thermometry of soapstone yields a formation (or equilibration) temperature of 147 ± 13 °C which, based on thermodynamic constraints, suggests that CO2(aq) concentrations of the hydrothermal fluid were at least an order of magnitude higher than in seawater. The association of magnesite with apatite in veins, magnesite with a d13C of -3.40 ± 0.04°, and the enrichment of CO2 in hydrothermal fluids point to magmatic degassing and melt-impregnation as the main source of CO2. Melt-rock interaction related to gas-rich alkali olivine basalt volcanism near the St. Paul's Rocks archipelago is manifested in systematic changes in peridotite compositions, notably a strong enrichment in incompatible elements with decreasing MgO/SiO2. These findings reveal a previously undocumented aspect of the geologic carbon cycle in one of the largest oceanic transform faults: Fueled by magmatism in or below the root zone of the transform fault and subsequent degassing, the fault constitutes a conduit for CO2-rich hydrothermal fluids, while carbonation of peridotite represents a vast sink for the emitted CO2. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

42. Globally‐distributed microbial eukaryotes exhibit endemism at deep‐sea hydrothermal vents.

Author

Hu, Sarah K., Smith, Amy R., Anderson, Rika E., Sylva, Sean P., Setzer, Michaela, Steadmon, Maria, Frank, Kiana L., Chan, Eric W., Lim, Darlene S. S., German, Christopher R., Breier, John A., Lang, Susan Q., Butterfield, David A., Fortunato, Caroline S., Seewald, Jeffrey S., and Huber, Julie A.

Subjects
HYDROTHERMAL vents, DEEP-sea animals, FOOD chains, EUKARYOTES, MICROBIAL diversity, SPECIES diversity, FOSSIL microorganisms
Abstract

Single‐celled microbial eukaryotes inhabit deep‐sea hydrothermal vent environments and play critical ecological roles in the vent‐associated microbial food web. 18S rRNA amplicon sequencing of diffuse venting fluids from four geographically‐ and geochemically‐distinct hydrothermal vent fields was applied to investigate community diversity patterns among protistan assemblages. The four vent fields include Axial Seamount at the Juan de Fuca Ridge, Sea Cliff and Apollo at the Gorda Ridge, all in the NE Pacific Ocean, and Piccard and Von Damm at the Mid‐Cayman Rise in the Caribbean Sea. We describe species diversity patterns with respect to hydrothermal vent field and sample type, identify putative vent endemic microbial eukaryotes, and test how vent fluid geochemistry may influence microbial community diversity. At a semi‐global scale, microbial eukaryotic communities at deep‐sea vents were composed of similar proportions of dinoflagellates, ciliates, Rhizaria, and stramenopiles. Individual vent fields supported distinct and highly diverse assemblages of protists that included potentially endemic or novel vent‐associated strains. These findings represent a census of deep‐sea hydrothermal vent protistan communities. Protistan diversity, which is shaped by the hydrothermal vent environment at a local scale, ultimately influences the vent‐associated microbial food web and the broader deep‐sea carbon cycle. [ABSTRACT FROM AUTHOR]

Published
2023
Full Text
View/download PDF

48. Nonequilibrium clumped isotope signals in microbial methane

Author

Wang, David T., Gruen, Danielle S., Lollar, Barbara Sherwood, Hinrichs, Kai-Uwe, Stewart, Lucy C., Holden, James F., Hristov, Alexander N., Pohlman, John W., Morrill, Penny L., Könneke, Martin, Delwiche, Kyle B., Reeves, Eoghan P., Sutcliffe, Chelsea N., Ritter, Daniel J., Seewald, Jeffrey S., McIntosh, Jennifer C., Hemond, Harold F., Kubo, Michael D., Cardace, Dawn, Hoehler, Tori M., and Ono, Shuhei

Published
2015

49. 2014 FIELD SEASON SUMMARY

Author

Mayer, Larry, Eberli, Gregor, Kane, Renato, Fuller, Sarah, Fisher, Charles R., Baums, Iliana B., Demopoulos, Amanda W.J., Dubilier, Nicole, Girard, Fanny, Kovacs, Kaitlin, Kurman, Melissa, Mentch, Jeff, Petersen, Jillian M., Saunders, Miles, Sayavedra, Lizbeth, Sibert, Ryan J., Vohsen, Sam, Brennan, Michael L., Bell, Katherine L.C., Smart, Clara, Vaughn, J. Ian, Ballard, Robert D., Socolofsky, Scott A., Breier, John A., Seewald, Jeffrey S., Wang, Binbin, Maness, Samantha, Nygren, Christian, Etnoyer, Peter J., Finamore, Daniel, Hammond, Stephen, Vargas, Marsha, Janson, Xavier, Tüzün, Suna, Wagner, Jamie, Ferraro, Danielle, Snyder, Will, Cormier, Marie-Helene, Blake, Ruth, Coleman, Dwight, Guerrier, Kelly, Saintilus, Nixon, Auscavitch, Steven, Carey, Steven, Roman, Chris, Dondin, Frederic, Roberston, Richard, Gobin, Judith, Wankel, Scott, Michel, Anna P.M., Amon, Diva, Marsh, Leigh, Ball, Bernard, Rodrigue, Katherine, Haldeman, Morgan, George, Adrienne, German, Christopher R., Mirmalek, Zara, Pallant, Amy, Davis, Dan, Raineault, Nicole A., Delgado, James P., and Petruncio, Emil

Published
2015

Catalog

Books, media, physical & digital resources
See catalog results