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Engle, Diana L.; Mélack, John M.

doi:10.1023/a:1006389124823

Cited by 78 publications

(30 citation statements)

References 32 publications

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“…Lowering atmospheric pressure and gas release are linked in freshwater lake environments (Mattson and Likens, 1990;Casper et al, 2000;Engle and Melack, 2000) and in peatlands (Rosenberry et al, 2003;Glaser et al, 2004;Strack et al, 2005;Tokida et al, 2007b;Comas et al, 2008). A relationship between lowering atmospheric pressure and gas release in the vicinity of data loggers was also seen in this study.…”

Section: Hydrologic Datasupporting

confidence: 73%

Using hydrologic measurements to investigate free-phase gas ebullition in a Maine peatland, USA

Bon

Reeve

Slater

et al. 2014

Hydrol. Earth Syst. Sci.

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Abstract. Northern peatlands cover more than 350 million ha and are an important source of methane (CH 4 ) and other biogenic gases contributing to climate change. Free-phase gas (FPG) accumulation and episodic release has recently been recognized as an important mechanism for biogenic gas flux from peatlands. It is likely that gas production and groundwater flow are interconnected in peatlands: groundwater flow influences gas production by regulating geochemical conditions and nutrient supply available for methanogenesis, while FPG influences groundwater flow through a reduction in peat permeability and by creating excess pore water pressures. Water samples collected from three well sites at Caribou Bog, Maine, show substantial dissolved CH 4 (5-16 mg L −1 ) in peat waters below 2 m depth and an increase in concentrations with depth. This suggests production and storage of CH 4 in deep peat that may be episodically released as FPG. Two min increment pressure transducer data reveal approximately 5 cm fluctuations in hydraulic head from both deep and shallow peat that are believed to be indicative of FPG release. FPG release persists up to 24 h during decreasing atmospheric pressure and a rising water table. Preferential flow is seen towards an area of relatively lower hydraulic head associated with the esker and pool system. Increased CH 4 concentrations are also found at the depth of the esker crest, suggesting that the high permeability esker is acting as a conduit for groundwater flow, driving a downward transport of labile carbon, resulting in higher rates of CH 4 production.

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Section: Hydrologic Datasupporting

confidence: 73%

Using hydrologic measurements to investigate free-phase gas ebullition in a Maine peatland, USA

Bon

Reeve

Slater

et al. 2014

Hydrol. Earth Syst. Sci.

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“…At the headwaters, CH 4 evasion from emerging groundwater is found to be significant [Neu et al, 2011]. In the floodplains, CH 4 flux depends on surface inundation and falling of floodwater, which triggers ebullition from shallow sediments [Engle and Melack, 2000;Melack et al, 2004;Belger et al, 2011]. Methane is also emitted in wetlands that are never flooded [e.g., Whalen, 2005;Lafleur, 2008] but with a shallow water table within tens of centimeters of surface.…”

Section: Summary Conclusion and Implications To The Amazon Carbon Cmentioning

confidence: 99%

The role of groundwater in the Amazon water cycle: 1. Influence on seasonal streamflow, flooding and wetlands

Míguez-Macho¹,

Fan²

2012

J. Geophys. Res.

174

235

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[1] Observational studies across the Amazon report a common occurrence of shallow water table in lowland valleys and groundwater-surface water exchange from small headwater catchments to large floodplains. In this study, we assess groundwater's role in the Amazon surface water dynamics using a continental-scale coupled groundwater-surface water model (LEAF-Hydro-Flood) forced by ERA-Interim reanalysis, at 2 km and 4 min resolution over 11 years (2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010). The simulation is validated with observed streamflow, water table depth and flooding extent. A parallel simulation without groundwater is conducted to isolate its effect. Our findings support the following hypotheses. First, in the headwater catchments, groundwater dominates streamflow; the observed variations in its dominance across the Amazon can be explained by the varying water table depth. Second, over large floodplains, there are two-way exchanges between floodwater and groundwater as infiltration in the wet season and seepage in the dry season, and the direction and magnitude are controlled by the water table depth. Third, the Amazon harbors large areas of wetlands that are rarely under floodwater and difficult to observe by remote sensing, but are maintained by a persistently shallow water table. Fourth, due to its delayed and muted response to rainfall, groundwater seepage persists in the dry season, buffering surface waters through seasonal droughts. Our simulations shed new lights on the spatial-temporal structures of the hidden subsurface hydrologic pathways across the Amazon and suggest possible mechanisms whereby groundwater actively participates in the Amazon water-carbon cycle such as CO 2 outgassing from groundwater seeps and CH 4 emission from groundwater-supported wetlands.Citation: Miguez-Macho, G., and Y. Fan (2012), The role of groundwater in the Amazon water cycle: 1. Influence on seasonal streamflow, flooding and wetlands,

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“…Concentrations of CO 2 within lakes are affected by biological and physical processes (Huotari et al, 2009). Processes that affect transport of dissolved gases in the water column include wind-induced upwelling and vertical mixing associated with breaking internal waves (MacIntyre et al, 1999;Polsenaere et al, 2013), nocturnal cooling (Crill et al, 1988;Engle & Melack, 2000;Podgrajsek et al, 2014), current shear (Pernica et al, 2014), stream inflows (Rueda & MacIntyre, 2010), and differential cooling (Monismith et al, 1990). Read et al (2012) suggested that near-surface mixing in small lakes would be dominated by cooling and that wind would make a larger contribution in larger lakes.…”

Section: Introductionmentioning

confidence: 99%

Effects of Wind and Buoyancy on Carbon Dioxide Distribution and Air‐Water Flux of a Stratified Temperate Lake

et al. 2018

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Improved calculations of emissions of greenhouse gases from stratified lakes require understanding the physical processes controlling transport of dissolved gases to the air‐water interface on diel, synoptic, and seasonal time scales. We address this issue during the transition from late summer to autumn cooling in a small temperate lake by combining micrometeorology, physical limnology, and carbon dioxide (CO2) measurements throughout the water column. Over the 26‐day campaign, the lake cooled and emitted CO2 with daily average loss of 23 mmol CO2 m−2 d−1. Over diel cycles, lake surface pCO2 decreased during daytime heating and increased during nighttime cooling, while daytime CO2 fluxes exceeded nighttime fluxes by 35% due to higher daytime wind speeds. We compared the effects of diel and synoptic weather patterns on the CO2 distribution within the lake and lake‐atmosphere CO2 flux. Increases in near‐surface pCO2 scaled with stratification and heat loss which moderated transport of dissolved gases into the mixed layer. When winds were above ~4 m s−1, lake‐scale circulations drove upwelling and downwelling that redistributed heat and carbon dioxide between the northeast and southwest basins. Short‐burst peak CO2 fluxes exceeded 50 mmol m−2 d−1 during windy periods associated with storms. However, the seasonal cooling‐induced transition to persistent deep mixing led to the highest CO2 concentrations in the mixed layer and at the surface and the highest sustained CO2 fluxes (approaching 100 mmol m−2 d−1).

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Cited by 78 publications

References 32 publications

Using hydrologic measurements to investigate free-phase gas ebullition in a Maine peatland, USA

Using hydrologic measurements to investigate free-phase gas ebullition in a Maine peatland, USA

The role of groundwater in the Amazon water cycle: 1. Influence on seasonal streamflow, flooding and wetlands

Effects of Wind and Buoyancy on Carbon Dioxide Distribution and Air‐Water Flux of a Stratified Temperate Lake

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