John Pohlman, PhD
John Pohlman is a Research Chemist with the Woods Hole Coastal and Marine Science Center Gas Hydrates Project.
Science and Products
Filter Total Items: 53
Hydrologic controls of methane dynamics in karst subterranean estuaries
Karst subterranean estuaries (KSEs) extend into carbonate platforms along 12% of all coastlines. A recent study has shown that microbial methane (CH4) consumption is an important component of the carbon cycle and food web dynamics within flooded caves that permeate KSEs. In this study, we obtained high‐resolution (~2.5‐day) temporal records of dissolved methane concentrations and its stable isotop
Authors
David Brankovits, John W. Pohlman, Neil K. Ganju, T.M. Iliffe, N. Lowell, E. Roth, S.P. Sylva, J.A. Emmert, L. L. Lapham
An intercomparison of oceanic methane and nitrous oxide measurements
Large-scale climatic forcing is impacting oceanic biogeochemical cycles and is expected to influence the water-column distribution of trace gases, including methane and nitrous oxide. Our ability as a scientific community to evaluate changes in the water-column inventories of methane and nitrous oxide depends largely on our capacity to obtain robust and accurate concentration measurements that can
Authors
Samuel Wilson, Hermann Bange, Damian Arevalo-Martinez, Jonathan Barnes, Alberto V. Borges, Ian Brown, John Bullister, Macarena Burgos, David Capelle, Michael Casso, Mercedes de la Paz, Laura Farias, Lindsay Fenwick, Sara Ferron, Gerardo Garcia, MIchael Glockzin, David Karl, Annette Kock, Sarah Laperriere, Cliff S. Law, Cara Manning, Andrew Marriner, Jukka-Pekka Myllykangas, John Pohlman, Andrew Rees, Allison Santoro, Philippe Tortll, Robert C. Upstill-Goddard, David Wisegarver, Gui-Ling Zhang, Gregor Rehder
Greenhouse gas emissions from diverse Arctic Alaskan lakes are dominated by young carbon
Climate-sensitive Arctic lakes have been identified as conduits for ancient permafrost-carbon (C) emissions and as such accelerate warming. However, the environmental factors that control emission pathways and their sources are unclear; this complicates upscaling, forecasting and climate-impact-assessment efforts. Here we show that current whole-lake CH4 and CO2 emissions from widespread lakes in
Authors
Clayton D. Elder, Xiaomei Xu, Jennifer Walker, Jordan L. Schnell, Kenneth M. Hinkel, Amy Townsend-Small, Christopher D. Arp, John W. Pohlman, Benjamin V. Gaglioti, Claudia I. Czimzik
Exudation rates and δ13C signatures of tree root soluble organic carbon in a riparian forest
Tree root exudation (TRE) of water soluble organic carbon (WSOC) is an important but under-assessed component of net primary production, and is thought to strongly influence rhizosphere biogeochemistry. Riparian systems in particular are often viewed as biogeochemical hot spots fueled partially by root exudate WSOC. However, TRE rates have not been previously reported for these systems. The δ13C s
Authors
S. W. Gougherty, J. E. Bauer, J. W. Pohlman
Methane- and dissolved organic carbon-fueled microbial loop supports a tropical subterranean estuary ecosystem
Subterranean estuaries extend inland into density-stratified coastal carbonate aquifers containing a surprising diversity of endemic animals (mostly crustaceans) within a highly oligotrophic habitat. How complex ecosystems (termed anchialine) thrive in this globally distributed, cryptic environment is poorly understood. Here, we demonstrate that a microbial loop shuttles methane and dissolved orga
Authors
D. Brankovits, John W. Pohlman, H. Niemann, M.B. Leigh, M.C. Leewis, K. W. Becker, T.M. Iliffe, Alvarez. F., M.F. Lehmann, B. Phillips
Enhanced CO2 uptake at a shallow Arctic Ocean seep field overwhelms the positive warming potential of emitted methane
Continued warming of the Arctic Ocean in coming decades is projected to trigger the release of teragrams (1 Tg = 106 tons) of methane from thawing subsea permafrost on shallow continental shelves and dissociation of methane hydrate on upper continental slopes. On the shallow shelves (<100 m water depth), methane released from the seafloor may reach the atmosphere and potentially amplify global war
Authors
John W. Pohlman, J. Greinert, Carolyn D. Ruppel, A Silyakova, L Vielstadte, Michael Casso, J Mienert, S Bunz
Methane turnover and environmental change from Holocene biomarker records in a thermokarst lake in Arctic Alaska
Arctic lakes and wetlands contribute a substantial amount of methane to the contemporary atmosphere, yet profound knowledge gaps remain regarding the intensity and climatic control of past methane emissions from this source. In this study, we reconstruct methane turnover and environmental conditions, including estimates of mean annual and summer temperature, from a thermokarst lake (Lake Qalluuraq
Authors
Marcus Elvert, John W. Pohlman, Kevin W. Becker, Benjamin V. Gaglioti, Kai-Uwe Hinrichs, Matthew J. Wooller
Colored dissolved organic matter in shallow estuaries: relationships between carbon sources and light attenuation
Light availability is of primary importance to the ecological function of shallow estuaries. For example, benthic primary production by submerged aquatic vegetation is contingent upon light penetration to the seabed. A major component that attenuates light in estuaries is colored dissolved organic matter (CDOM). CDOM is often measured via a proxy, fluorescing dissolved organic matter (fDOM), due t
Authors
W.K. Oestreich, Neil K. Ganju, John W. Pohlman, Steven E. Suttles
Slipstream: an early Holocene slump and turbidite record from the frontal ridge of the Cascadia accretionary wedge off western Canada and paleoseismic implications
Slipstream Slump, a well-preserved 3 km wide sedimentary failure from the frontal ridge of the Cascadia accretionary wedge 85 km off Vancouver Island, Canada, was sampled during Canadian Coast Guard Ship (CCGS) John P. Tully cruise 2008007PGC along a transect of five piston cores. Shipboard sediment analysis and physical property logging revealed 12 turbidites interbedded with thick hemipelagic se
Authors
T.S. Hamilton, Randolph J. Enkin, Michael Riedel, Gary C. Rogers, John W. Pohlman, Heather M. Benway
Nonequilibrium clumped isotope signals in microbial methane
Methane is a key component in the global carbon cycle with a wide range of anthropogenic and natural sources. Although isotopic compositions of methane have traditionally aided source identification, the abundance of its multiply-substituted “clumped” isotopologues, e.g., 13CH3D, has recently emerged as a proxy for determining methane-formation temperatures; however, the impact of biological proce
Authors
David T. Wang, Danielle S. Gruen, Barbara Sherwood Lollar, Kai-Uwe Hinrichs, Lucy C. Stewart, James F. Holden, Alexander N. Hristov, John W. Pohlman, Penny L. Morrill, Martin Könneke, Kyle B. Delwiche, Eoghan P. Reeves, Chelsea N. Sutcliffe, Daniel J. Ritter, Jeffrey S. Seewald, Jennifer C. McIntosh, Harold F. Hemond, Michael D. Kubo, Dawn Cardace, Tori M. Hoehler, Shuhei Ono
Radiocarbon age-offsets in an arctic lake reveal the long-term response of permafrost carbon to climate change
Continued warming of the Arctic may cause permafrost to thaw and speed the decomposition of large stores of soil organic carbon (OC), thereby accentuating global warming. However, it is unclear if recent warming has raised the current rates of permafrost OC release to anomalous levels or to what extent soil carbon release is sensitive to climate forcing. Here we use a time series of radiocarbon ag
Authors
Benjamin V. Gaglioti, Daniel H. Mann, Benjamin M. Jones, John W. Pohlman, Michael L. Kunz, Matthew J. Wooller
A simple headspace equilibration method for measuring dissolved methane
Dissolved methane concentrations in the ocean are close to equilibrium with the atmosphere. Because methane is only sparingly soluble in seawater, measuring it without contamination is challenging for samples collected and processed in the presence of air. Several methods for analyzing dissolved methane are described in the literature, yet none has conducted a thorough assessment of the method yie
Authors
C Magen, L. L. Lapham, John W. Pohlman, Kristin N. Marshall, S. Bosman, Michael Casso, J. P. Chanton
Science and Products
Filter Total Items: 53
Hydrologic controls of methane dynamics in karst subterranean estuaries
Karst subterranean estuaries (KSEs) extend into carbonate platforms along 12% of all coastlines. A recent study has shown that microbial methane (CH4) consumption is an important component of the carbon cycle and food web dynamics within flooded caves that permeate KSEs. In this study, we obtained high‐resolution (~2.5‐day) temporal records of dissolved methane concentrations and its stable isotop
Authors
David Brankovits, John W. Pohlman, Neil K. Ganju, T.M. Iliffe, N. Lowell, E. Roth, S.P. Sylva, J.A. Emmert, L. L. Lapham
An intercomparison of oceanic methane and nitrous oxide measurements
Large-scale climatic forcing is impacting oceanic biogeochemical cycles and is expected to influence the water-column distribution of trace gases, including methane and nitrous oxide. Our ability as a scientific community to evaluate changes in the water-column inventories of methane and nitrous oxide depends largely on our capacity to obtain robust and accurate concentration measurements that can
Authors
Samuel Wilson, Hermann Bange, Damian Arevalo-Martinez, Jonathan Barnes, Alberto V. Borges, Ian Brown, John Bullister, Macarena Burgos, David Capelle, Michael Casso, Mercedes de la Paz, Laura Farias, Lindsay Fenwick, Sara Ferron, Gerardo Garcia, MIchael Glockzin, David Karl, Annette Kock, Sarah Laperriere, Cliff S. Law, Cara Manning, Andrew Marriner, Jukka-Pekka Myllykangas, John Pohlman, Andrew Rees, Allison Santoro, Philippe Tortll, Robert C. Upstill-Goddard, David Wisegarver, Gui-Ling Zhang, Gregor Rehder
Greenhouse gas emissions from diverse Arctic Alaskan lakes are dominated by young carbon
Climate-sensitive Arctic lakes have been identified as conduits for ancient permafrost-carbon (C) emissions and as such accelerate warming. However, the environmental factors that control emission pathways and their sources are unclear; this complicates upscaling, forecasting and climate-impact-assessment efforts. Here we show that current whole-lake CH4 and CO2 emissions from widespread lakes in
Authors
Clayton D. Elder, Xiaomei Xu, Jennifer Walker, Jordan L. Schnell, Kenneth M. Hinkel, Amy Townsend-Small, Christopher D. Arp, John W. Pohlman, Benjamin V. Gaglioti, Claudia I. Czimzik
Exudation rates and δ13C signatures of tree root soluble organic carbon in a riparian forest
Tree root exudation (TRE) of water soluble organic carbon (WSOC) is an important but under-assessed component of net primary production, and is thought to strongly influence rhizosphere biogeochemistry. Riparian systems in particular are often viewed as biogeochemical hot spots fueled partially by root exudate WSOC. However, TRE rates have not been previously reported for these systems. The δ13C s
Authors
S. W. Gougherty, J. E. Bauer, J. W. Pohlman
Methane- and dissolved organic carbon-fueled microbial loop supports a tropical subterranean estuary ecosystem
Subterranean estuaries extend inland into density-stratified coastal carbonate aquifers containing a surprising diversity of endemic animals (mostly crustaceans) within a highly oligotrophic habitat. How complex ecosystems (termed anchialine) thrive in this globally distributed, cryptic environment is poorly understood. Here, we demonstrate that a microbial loop shuttles methane and dissolved orga
Authors
D. Brankovits, John W. Pohlman, H. Niemann, M.B. Leigh, M.C. Leewis, K. W. Becker, T.M. Iliffe, Alvarez. F., M.F. Lehmann, B. Phillips
Enhanced CO2 uptake at a shallow Arctic Ocean seep field overwhelms the positive warming potential of emitted methane
Continued warming of the Arctic Ocean in coming decades is projected to trigger the release of teragrams (1 Tg = 106 tons) of methane from thawing subsea permafrost on shallow continental shelves and dissociation of methane hydrate on upper continental slopes. On the shallow shelves (<100 m water depth), methane released from the seafloor may reach the atmosphere and potentially amplify global war
Authors
John W. Pohlman, J. Greinert, Carolyn D. Ruppel, A Silyakova, L Vielstadte, Michael Casso, J Mienert, S Bunz
Methane turnover and environmental change from Holocene biomarker records in a thermokarst lake in Arctic Alaska
Arctic lakes and wetlands contribute a substantial amount of methane to the contemporary atmosphere, yet profound knowledge gaps remain regarding the intensity and climatic control of past methane emissions from this source. In this study, we reconstruct methane turnover and environmental conditions, including estimates of mean annual and summer temperature, from a thermokarst lake (Lake Qalluuraq
Authors
Marcus Elvert, John W. Pohlman, Kevin W. Becker, Benjamin V. Gaglioti, Kai-Uwe Hinrichs, Matthew J. Wooller
Colored dissolved organic matter in shallow estuaries: relationships between carbon sources and light attenuation
Light availability is of primary importance to the ecological function of shallow estuaries. For example, benthic primary production by submerged aquatic vegetation is contingent upon light penetration to the seabed. A major component that attenuates light in estuaries is colored dissolved organic matter (CDOM). CDOM is often measured via a proxy, fluorescing dissolved organic matter (fDOM), due t
Authors
W.K. Oestreich, Neil K. Ganju, John W. Pohlman, Steven E. Suttles
Slipstream: an early Holocene slump and turbidite record from the frontal ridge of the Cascadia accretionary wedge off western Canada and paleoseismic implications
Slipstream Slump, a well-preserved 3 km wide sedimentary failure from the frontal ridge of the Cascadia accretionary wedge 85 km off Vancouver Island, Canada, was sampled during Canadian Coast Guard Ship (CCGS) John P. Tully cruise 2008007PGC along a transect of five piston cores. Shipboard sediment analysis and physical property logging revealed 12 turbidites interbedded with thick hemipelagic se
Authors
T.S. Hamilton, Randolph J. Enkin, Michael Riedel, Gary C. Rogers, John W. Pohlman, Heather M. Benway
Nonequilibrium clumped isotope signals in microbial methane
Methane is a key component in the global carbon cycle with a wide range of anthropogenic and natural sources. Although isotopic compositions of methane have traditionally aided source identification, the abundance of its multiply-substituted “clumped” isotopologues, e.g., 13CH3D, has recently emerged as a proxy for determining methane-formation temperatures; however, the impact of biological proce
Authors
David T. Wang, Danielle S. Gruen, Barbara Sherwood Lollar, Kai-Uwe Hinrichs, Lucy C. Stewart, James F. Holden, Alexander N. Hristov, John W. Pohlman, Penny L. Morrill, Martin Könneke, Kyle B. Delwiche, Eoghan P. Reeves, Chelsea N. Sutcliffe, Daniel J. Ritter, Jeffrey S. Seewald, Jennifer C. McIntosh, Harold F. Hemond, Michael D. Kubo, Dawn Cardace, Tori M. Hoehler, Shuhei Ono
Radiocarbon age-offsets in an arctic lake reveal the long-term response of permafrost carbon to climate change
Continued warming of the Arctic may cause permafrost to thaw and speed the decomposition of large stores of soil organic carbon (OC), thereby accentuating global warming. However, it is unclear if recent warming has raised the current rates of permafrost OC release to anomalous levels or to what extent soil carbon release is sensitive to climate forcing. Here we use a time series of radiocarbon ag
Authors
Benjamin V. Gaglioti, Daniel H. Mann, Benjamin M. Jones, John W. Pohlman, Michael L. Kunz, Matthew J. Wooller
A simple headspace equilibration method for measuring dissolved methane
Dissolved methane concentrations in the ocean are close to equilibrium with the atmosphere. Because methane is only sparingly soluble in seawater, measuring it without contamination is challenging for samples collected and processed in the presence of air. Several methods for analyzing dissolved methane are described in the literature, yet none has conducted a thorough assessment of the method yie
Authors
C Magen, L. L. Lapham, John W. Pohlman, Kristin N. Marshall, S. Bosman, Michael Casso, J. P. Chanton