SEARCH · Search USGS

Results for “JGR Atmospheres”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

22 records · Page 2Linked to original sources

USGS2021

Predicted vulnerability of carbon in permafrost peatlands With future climate change and permafrost thaw in western Canada

Climate warming in high-latitude regions is thawing carbon-rich permafrost soils, which can release carbon to the atmosphere and enhance climate warming. Using a coupled model of long-term peatland dynamics (Holocene Peat Model, HPM-Arctic), we quantify the potential loss of carbon with future climate warming for six sites with differing climates and permafrost histories in Northwestern Canada. We compared the net carbon balance at 2100 CE resulting from new productivity and the decomposition of active layer and newly thawed permafrost peats under RCP8.5 as a high-end constraint. Modeled net carbon losses ranged from −3.0 kg C m −2 (net loss) to +0.1 kg C m −2 (net gain) between 2015 and 2100. Losses of newly thawed permafrost peat comprised 0.2%–25% (median: 1.6%) of “old” C loss, which were related to the residence time of peat in the active layer before being incorporated into the permafrost, peat temperature, and presence of permafrost. The largest C loss was from the permafrost-free site, not from permafrost sites. C losses were greatest from depths of 0.2–1.0 m. New C added to the profile through net primary productivity between 2015 and 2100 offset ∼40% to >100% of old C losses across the sites. Differences between modeled active layer deepening and flooding following permafrost thaw resulted in very small differences in net C loss by 2100, illustrating the important role of present-day conditions and permafrost aggradation history in controlling net C loss.

western Canada↗

USGS2025

Exploring the use of non-invasive drone-based Ground Penetrating Radar (GPR) to characterize biogenic gas dynamics in subtropical peat soils

Peat soils are a critical component of the global carbon cycle as natural producers of biogenic greenhouse gases (e.g., methane and carbon dioxide) that accumulate within the soil matrix and are episodically released to the atmosphere. Previous studies have showed the unique ability of ground-based minimally-invasive geophysical methods like ground-penetrating radar (GPR) to characterize carbon dynamics in peat soils. However, the GPR methods are still limited by the scale of measurements and soil disturbance potentially altering biogenic gas releases during deployment. Here we explore the potential of drone-based GPR for identification of hot spots and hot moments of gas accumulation and release in subtropical peat soils. We collected drone-based GPR datasets across two grids (~ 17,500 m2) in the Florida Everglades during January, September, and November of 2023 to characterize peat thickness and seasonal variability of gas content. Results show that drone-based GPR is effective and efficient for: 1) capturing the temporal variation of in-situ biogenic gas content in peat soils with changes between 1-25% volumetric gas content over repeatable grids; 2) inferring peat thickness from discrete measurements ranging between 0.8-1.2 m; and 3) estimating methane flux releases of 63 and 135 mg CH4 m-2 day-1 for specific locations and time periods that are strikingly consistent with our coincident gas trap measurements. This work also indicates that (1) spatial distribution of gas content in the Everglades is strongly controlled by landscape morphology such as ridges and sloughs and (2) the temporal variation of gas content is seasonal with increased gas production during the wet season.

Florida↗

USGS2023

A one-dimensional volcanic plume model for predicting ash aggregation

During explosive volcanic eruptions, volcanic ash is ejected into the atmosphere, impacting aircraft safety and downwind communities. These volcanic clouds tend to be dominated by fine ash (<63 μm in diameter), permitting transport over hundreds to thousands of kilometers. However, field observations show that much of this fine ash aggregates into clusters or pellets with faster settling velocities than individual particles. Models of ash transport and deposition require an understanding of aggregation processes, which depend on factors like moisture content and local particle collision rates. In this study, we develop a Plume Model for Aggregate Prediction, a one-dimensional (1D) volcanic plume model that predicts the plume rise height, concentration of water phases, and size distribution of resulting ash aggregates from a set of eruption source parameters. The plume model uses a control volume approach to solve mass, momentum, and energy equations along the direction of the plume axis. The aggregation equation is solved using a fixed pivot technique and incorporates a sticking efficiency model developed from analog laboratory experiments of particle aggregation within a novel turbulence tower. When applied to the 2009 eruption of Redoubt Volcano, Alaska, the 1D model predicts that the majority of the plume is over-saturated with water, leading to a high rate of aggregation. Although the mean grain size of the computed Redoubt aggregates is larger than the measured deposits, with a peak at 1 mm rather than 500 μm, the present results provide a quantitative estimate for the magnitude of aggregation in an eruption.

JGR Solid Earth↗

USGS2025

The δ13C signature of dissolved organic and inorganic carbon reveals complex carbon transformations within a salt marsh

Coastal wetlands have high rates of atmospheric CO 2 uptake, which is subsequently respired back to the atmosphere, stored as organic matter within flooded, anoxic soils, or exported to the coastal ocean. Transformation of fixed carbon occurs through a variety of subsurface aerobic and anaerobic microbial processes, and results in a large inventory of dissolved carbon. Carbon source and the roles of aerobic respiration, sulfate reduction, and methane cycling were evaluated within salt marsh peat and the underlying sandy subterranean estuary. There is a large increase in dissolved inorganic carbon (DIC, 7,350 ± 3,900 μmol L −1 ), dissolved organic carbon (DOC, 1,040 ± 1,480 μmol L −1 ) and CH 4 (14.5 ± 33.3 μmol L −1 ) within the marsh porewaters compared to creek waters. Alkalinity production (5,730 ± 2,170 μeq L −1 ) and sulfate removal (1,810 ± 1,970 μmol L −1 ) indicate anaerobic respiration, however, relative contributions from the various decomposition pathways cannot be identified due to overlapping geochemical signatures. The δ 13 C of the DOC (−29.0 ± 3.7‰) and DIC (−11.2 ± 1.1‰) produced within the marsh differed from the bulk soil organic matter δ 13 C (−14.5 ± 0.2‰). We explore a variety of mechanisms that could result in co-occurring depleted δ 13 C-DOC and enriched δ 13 C-DIC compared to the bulk soil organic carbon pool and salt marsh vegetation, including selective mineralization, production of δ 13 C-depleted bacterial biomass, and methane-derived DOC. While important questions remain about carbon cycling pathways, we found evidence of a cryptic methane cycle. Alteration of the δ 13 C of carbon species complicates source attribution in solid and dissolved phases and careful consideration should be used when carbon is partitioned between in situ salt marsh production and external marine and terrestrial sources.

Massachusetts↗