John Pohlman, PhD
John Pohlman is a Research Chemist with the Woods Hole Coastal and Marine Science Center Gas Hydrates Project.
Science and Products
Comparison of methane concentration and stable carbon isotope data for natural samples analyzed by discrete sample introduction module - cavity ring down spectroscopy (DSIM-CRDS) and traditional methods Comparison of methane concentration and stable carbon isotope data for natural samples analyzed by discrete sample introduction module - cavity ring down spectroscopy (DSIM-CRDS) and traditional methods
A discrete sample introduction module (DSIM) was developed and interfaced to a cavity ring-down spectrometer to enable measurements of methane and CO2 concentrations and 13C values with a commercially available cavity ring-down spectrometer (CRDS). The DSIM-CRDS system permits the analysis of limited volume (5 - 100-ml) samples ranging six orders-of-magnitude from 100% analyte to the...
Geochemical data supporting investigation of solute and particle cycling and fluxes from two tidal wetlands on the south shore of Cape Cod, Massachusetts, 2012-19 (ver. 3.0, January 2025) Geochemical data supporting investigation of solute and particle cycling and fluxes from two tidal wetlands on the south shore of Cape Cod, Massachusetts, 2012-19 (ver. 3.0, January 2025)
Assessment of geochemical cycling within tidal wetlands and measurement of fluxes of dissolved and particulate constituents between wetlands and coastal water bodies are critical to evaluating ecosystem function, service, and status. The U.S. Geological Survey and collaborators collected surface water and porewater geochemical data from a tidal wetland located on the eastern shore of...
Vertical chemical profiles collected across haloclines in the water column of the Ox Bel Ha cave network within the coastal aquifer of the Yucatan Peninsula in January 2015 and January 2016 Vertical chemical profiles collected across haloclines in the water column of the Ox Bel Ha cave network within the coastal aquifer of the Yucatan Peninsula in January 2015 and January 2016
Natural cave passages penetrating a coastal aquifer in the Yucatan Peninsula (Mexico) were accessed to test the hypothesis that chemoclines associated with salinity gradients (haloclines) within the flooded cave networks of the karst subterranean estuary are sites of methane oxidation. Two field trips were carried out to the fully-submerged cave system located 6.6 km inland from the...
Temporal hydrologic and chemical records from the Ox Bel Ha cave network within the coastal aquifer of the Yucatan Peninsula, from January 2015 to January 2016 Temporal hydrologic and chemical records from the Ox Bel Ha cave network within the coastal aquifer of the Yucatan Peninsula, from January 2015 to January 2016
Natural cave passages penetrating a coastal aquifer in the Yucatan Peninsula (Mexico) were accessed to investigate how regional meteorology and hydrology control methane dynamics in karst subterranean estuaries. Three field trips were carried out in January 2015, June 2015, and January 2016 to obtain year-long high-resolution temporal records of water chemistry and environmental...
Data and calculations to support the study of the sea-air flux of methane and carbon dioxide on the West Spitsbergen margin in June 2014 Data and calculations to support the study of the sea-air flux of methane and carbon dioxide on the West Spitsbergen margin in June 2014
A critical question for assessing global greenhouse gas budgets is how much of the methane that escapes from seafloor cold seep sites to the overlying water column eventually crosses the sea-air interface and reaches the atmosphere. The issue is particularly important in Arctic Ocean waters since rapid warming there increases the likelihood that gas hydrate--an ice-like form of methane...
Filter Total Items: 62
Barkley Canyon gas hydrates: A synthesis based on two decades of seafloor observation and remote sensing Barkley Canyon gas hydrates: A synthesis based on two decades of seafloor observation and remote sensing
Barkley Canyon is one of the few known sites worldwide with the occurrence of thermogenic gas seepage and formation of structure-II and structure-H gas hydrate mounds on the seafloor. This site is the location of continuous seafloor monitoring as part of the Ocean Networks Canada (ONC) cabled observatory off the west coast off Vancouver Island, British Columbia, Canada. We combine repeat...
Authors
M. Reidel, M. Scherwath, M. Romer, C. K. Paull, E. Lundsten, D. W. Caress, P. Brewer, John Pohlman, L. L. Lapham, N. R. Chapman, M. Whiticar, G. D. Spence, R. Enkin, K. Douglas
USGS tools perform gas source analysis in the field USGS tools perform gas source analysis in the field
Field studies of gas hydrate rely on gas sampling and analysis tools to determine the origins and alteration of methane and other hydrocarbons. The conventional strategy for deciphering gas origins has been to collect gas and other related samples in the field then pack, ship, store, and later analyze these discrete samples in a laboratory using instruments that require specialized...
Authors
John Pohlman, Michael Casso, Lee-Gray Boze, Emile Bergeron
Northern Cascadia Margin gas hydrates — Regional geophysical surveying, IODP drilling leg 311, and cabled observatory monitoring Northern Cascadia Margin gas hydrates — Regional geophysical surveying, IODP drilling leg 311, and cabled observatory monitoring
This article reviews extensive geophysical survey data, ocean drilling results and long-term seafloor monitoring that constrain the distribution and concentration of gas hydrates within the accretionary prism of the northern Cascadia subduction margin, located offshore Vancouver Island in Canada. Seismic surveys and geologic studies conducted since the 1980s have mapped the bottom...
Authors
Michael Riedel, Timothy S. Collett, Martin Scherwath, John W. Pohlman, Roy Hyndman, George Spence
Contribution of deep-sourced carbon from hydrocarbon seeps to sedimentary organic carbon: Evidence from radiocarbon and stable isotope geochemistry Contribution of deep-sourced carbon from hydrocarbon seeps to sedimentary organic carbon: Evidence from radiocarbon and stable isotope geochemistry
Sulfate-driven anaerobic oxidation of methane (AOM) limits the release of methane from marine sediments and promotes the formation of carbonates close to the seafloor in seepage areas along continental margins. It has been established that hydrocarbon seeps are a source of methane, dissolved inorganic carbon, and dissolved organic carbon to marine environments. However, questions remain...
Authors
Dong Feng, John Pohlman, Jorn Peckmann, Yuedong Sun, Yu Hu, Harry Roberts, Duofu Chen
Discrete sample introduction module for quantitative and isotopic analysis of methane and other gases by cavity ring-down spectroscopy Discrete sample introduction module for quantitative and isotopic analysis of methane and other gases by cavity ring-down spectroscopy
Carbon dioxide (CO2) and methane (CH4) are natural and anthropogenic products that play a central role in the global carbon cycle and regulating Earth’s climate. Applications utilizing laser absorption spectroscopy, which continuously measure concentrations and stable isotope ratios of these greenhouse gases, are routinely employed to measure the source and magnitude of atmospheric...
Authors
John Pohlman, Michael Casso, Cedric Magen, Emile M. Bergeron
Metabolic flexibility of aerobic methanotrophs under anoxic conditions in Arctic lake sediments Metabolic flexibility of aerobic methanotrophs under anoxic conditions in Arctic lake sediments
Methane (CH4) emissions from Arctic lakes are a large and growing source of greenhouse gas to the atmosphere with critical implications for global climate. Because Arctic lakes are ice covered for much of the year, understanding the metabolic flexibility of methanotrophs under anoxic conditions would aid in characterizing the mechanisms responsible for limiting CH4 emissions from high...
Authors
Ruoying He, Jing Wang, John Pohlman, Zhongjun Jia, Yi-Xuan Chu, Matthew J. Wooller, Mary Beth Leigh
Science and Products
Comparison of methane concentration and stable carbon isotope data for natural samples analyzed by discrete sample introduction module - cavity ring down spectroscopy (DSIM-CRDS) and traditional methods Comparison of methane concentration and stable carbon isotope data for natural samples analyzed by discrete sample introduction module - cavity ring down spectroscopy (DSIM-CRDS) and traditional methods
A discrete sample introduction module (DSIM) was developed and interfaced to a cavity ring-down spectrometer to enable measurements of methane and CO2 concentrations and 13C values with a commercially available cavity ring-down spectrometer (CRDS). The DSIM-CRDS system permits the analysis of limited volume (5 - 100-ml) samples ranging six orders-of-magnitude from 100% analyte to the...
Geochemical data supporting investigation of solute and particle cycling and fluxes from two tidal wetlands on the south shore of Cape Cod, Massachusetts, 2012-19 (ver. 3.0, January 2025) Geochemical data supporting investigation of solute and particle cycling and fluxes from two tidal wetlands on the south shore of Cape Cod, Massachusetts, 2012-19 (ver. 3.0, January 2025)
Assessment of geochemical cycling within tidal wetlands and measurement of fluxes of dissolved and particulate constituents between wetlands and coastal water bodies are critical to evaluating ecosystem function, service, and status. The U.S. Geological Survey and collaborators collected surface water and porewater geochemical data from a tidal wetland located on the eastern shore of...
Vertical chemical profiles collected across haloclines in the water column of the Ox Bel Ha cave network within the coastal aquifer of the Yucatan Peninsula in January 2015 and January 2016 Vertical chemical profiles collected across haloclines in the water column of the Ox Bel Ha cave network within the coastal aquifer of the Yucatan Peninsula in January 2015 and January 2016
Natural cave passages penetrating a coastal aquifer in the Yucatan Peninsula (Mexico) were accessed to test the hypothesis that chemoclines associated with salinity gradients (haloclines) within the flooded cave networks of the karst subterranean estuary are sites of methane oxidation. Two field trips were carried out to the fully-submerged cave system located 6.6 km inland from the...
Temporal hydrologic and chemical records from the Ox Bel Ha cave network within the coastal aquifer of the Yucatan Peninsula, from January 2015 to January 2016 Temporal hydrologic and chemical records from the Ox Bel Ha cave network within the coastal aquifer of the Yucatan Peninsula, from January 2015 to January 2016
Natural cave passages penetrating a coastal aquifer in the Yucatan Peninsula (Mexico) were accessed to investigate how regional meteorology and hydrology control methane dynamics in karst subterranean estuaries. Three field trips were carried out in January 2015, June 2015, and January 2016 to obtain year-long high-resolution temporal records of water chemistry and environmental...
Data and calculations to support the study of the sea-air flux of methane and carbon dioxide on the West Spitsbergen margin in June 2014 Data and calculations to support the study of the sea-air flux of methane and carbon dioxide on the West Spitsbergen margin in June 2014
A critical question for assessing global greenhouse gas budgets is how much of the methane that escapes from seafloor cold seep sites to the overlying water column eventually crosses the sea-air interface and reaches the atmosphere. The issue is particularly important in Arctic Ocean waters since rapid warming there increases the likelihood that gas hydrate--an ice-like form of methane...
Filter Total Items: 62
Barkley Canyon gas hydrates: A synthesis based on two decades of seafloor observation and remote sensing Barkley Canyon gas hydrates: A synthesis based on two decades of seafloor observation and remote sensing
Barkley Canyon is one of the few known sites worldwide with the occurrence of thermogenic gas seepage and formation of structure-II and structure-H gas hydrate mounds on the seafloor. This site is the location of continuous seafloor monitoring as part of the Ocean Networks Canada (ONC) cabled observatory off the west coast off Vancouver Island, British Columbia, Canada. We combine repeat...
Authors
M. Reidel, M. Scherwath, M. Romer, C. K. Paull, E. Lundsten, D. W. Caress, P. Brewer, John Pohlman, L. L. Lapham, N. R. Chapman, M. Whiticar, G. D. Spence, R. Enkin, K. Douglas
USGS tools perform gas source analysis in the field USGS tools perform gas source analysis in the field
Field studies of gas hydrate rely on gas sampling and analysis tools to determine the origins and alteration of methane and other hydrocarbons. The conventional strategy for deciphering gas origins has been to collect gas and other related samples in the field then pack, ship, store, and later analyze these discrete samples in a laboratory using instruments that require specialized...
Authors
John Pohlman, Michael Casso, Lee-Gray Boze, Emile Bergeron
Northern Cascadia Margin gas hydrates — Regional geophysical surveying, IODP drilling leg 311, and cabled observatory monitoring Northern Cascadia Margin gas hydrates — Regional geophysical surveying, IODP drilling leg 311, and cabled observatory monitoring
This article reviews extensive geophysical survey data, ocean drilling results and long-term seafloor monitoring that constrain the distribution and concentration of gas hydrates within the accretionary prism of the northern Cascadia subduction margin, located offshore Vancouver Island in Canada. Seismic surveys and geologic studies conducted since the 1980s have mapped the bottom...
Authors
Michael Riedel, Timothy S. Collett, Martin Scherwath, John W. Pohlman, Roy Hyndman, George Spence
Contribution of deep-sourced carbon from hydrocarbon seeps to sedimentary organic carbon: Evidence from radiocarbon and stable isotope geochemistry Contribution of deep-sourced carbon from hydrocarbon seeps to sedimentary organic carbon: Evidence from radiocarbon and stable isotope geochemistry
Sulfate-driven anaerobic oxidation of methane (AOM) limits the release of methane from marine sediments and promotes the formation of carbonates close to the seafloor in seepage areas along continental margins. It has been established that hydrocarbon seeps are a source of methane, dissolved inorganic carbon, and dissolved organic carbon to marine environments. However, questions remain...
Authors
Dong Feng, John Pohlman, Jorn Peckmann, Yuedong Sun, Yu Hu, Harry Roberts, Duofu Chen
Discrete sample introduction module for quantitative and isotopic analysis of methane and other gases by cavity ring-down spectroscopy Discrete sample introduction module for quantitative and isotopic analysis of methane and other gases by cavity ring-down spectroscopy
Carbon dioxide (CO2) and methane (CH4) are natural and anthropogenic products that play a central role in the global carbon cycle and regulating Earth’s climate. Applications utilizing laser absorption spectroscopy, which continuously measure concentrations and stable isotope ratios of these greenhouse gases, are routinely employed to measure the source and magnitude of atmospheric...
Authors
John Pohlman, Michael Casso, Cedric Magen, Emile M. Bergeron
Metabolic flexibility of aerobic methanotrophs under anoxic conditions in Arctic lake sediments Metabolic flexibility of aerobic methanotrophs under anoxic conditions in Arctic lake sediments
Methane (CH4) emissions from Arctic lakes are a large and growing source of greenhouse gas to the atmosphere with critical implications for global climate. Because Arctic lakes are ice covered for much of the year, understanding the metabolic flexibility of methanotrophs under anoxic conditions would aid in characterizing the mechanisms responsible for limiting CH4 emissions from high...
Authors
Ruoying He, Jing Wang, John Pohlman, Zhongjun Jia, Yi-Xuan Chu, Matthew J. Wooller, Mary Beth Leigh