ORCID Profile
0000-0001-5787-5682
Current Organisation
Southern Cross University
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Geochemistry | Greenhouse gas inventories and fluxes | Inorganic geochemistry | Isotope geochemistry | Environmental Monitoring | Inorganic Geochemistry | Geochemistry | Isotope Geochemistry |
Effects of Climate Change and Variability on Australia (excl. Social Impacts) | Physical and Chemical Conditions of Water in Fresh, Ground and Surface Water Environments (excl. Urban and Industrial Use) |
Publisher: Wiley
Date: 23-07-2020
DOI: 10.1111/GCB.15201
Publisher: Wiley
Date: 02-12-2016
DOI: 10.1002/LNO.10444
Publisher: Elsevier
Date: 2022
Publisher: Bulletin of Marine Science
Date: 04-2019
Publisher: Elsevier BV
Date: 02-2015
Publisher: Springer Science and Business Media LLC
Date: 22-05-2023
Publisher: Wiley
Date: 25-12-2019
DOI: 10.1002/HYP.13679
Publisher: Elsevier BV
Date: 12-2022
Publisher: Copernicus GmbH
Date: 27-09-2023
Publisher: Elsevier BV
Date: 12-2023
Publisher: Elsevier BV
Date: 02-2018
Publisher: Copernicus GmbH
Date: 15-07-2020
DOI: 10.5194/ESSD-12-1561-2020
Abstract: Abstract. Understanding and quantifying the global methane (CH4) budget is important for assessing realistic pathways to mitigate climate change. Atmospheric emissions and concentrations of CH4 continue to increase, making CH4 the second most important human-influenced greenhouse gas in terms of climate forcing, after carbon dioxide (CO2). The relative importance of CH4 compared to CO2 depends on its shorter atmospheric lifetime, stronger warming potential, and variations in atmospheric growth rate over the past decade, the causes of which are still debated. Two major challenges in reducing uncertainties in the atmospheric growth rate arise from the variety of geographically overlapping CH4 sources and from the destruction of CH4 by short-lived hydroxyl radicals (OH). To address these challenges, we have established a consortium of multidisciplinary scientists under the umbrella of the Global Carbon Project to synthesize and stimulate new research aimed at improving and regularly updating the global methane budget. Following Saunois et al. (2016), we present here the second version of the living review paper dedicated to the decadal methane budget, integrating results of top-down studies (atmospheric observations within an atmospheric inverse-modelling framework) and bottom-up estimates (including process-based models for estimating land surface emissions and atmospheric chemistry, inventories of anthropogenic emissions, and data-driven extrapolations). For the 2008–2017 decade, global methane emissions are estimated by atmospheric inversions (a top-down approach) to be 576 Tg CH4 yr−1 (range 550–594, corresponding to the minimum and maximum estimates of the model ensemble). Of this total, 359 Tg CH4 yr−1 or ∼ 60 % is attributed to anthropogenic sources, that is emissions caused by direct human activity (i.e. anthropogenic emissions range 336–376 Tg CH4 yr−1 or 50 %–65 %). The mean annual total emission for the new decade (2008–2017) is 29 Tg CH4 yr−1 larger than our estimate for the previous decade (2000–2009), and 24 Tg CH4 yr−1 larger than the one reported in the previous budget for 2003–2012 (Saunois et al., 2016). Since 2012, global CH4 emissions have been tracking the warmest scenarios assessed by the Intergovernmental Panel on Climate Change. Bottom-up methods suggest almost 30 % larger global emissions (737 Tg CH4 yr−1, range 594–881) than top-down inversion methods. Indeed, bottom-up estimates for natural sources such as natural wetlands, other inland water systems, and geological sources are higher than top-down estimates. The atmospheric constraints on the top-down budget suggest that at least some of these bottom-up emissions are overestimated. The latitudinal distribution of atmospheric observation-based emissions indicates a predominance of tropical emissions (∼ 65 % of the global budget, 30∘ N) compared to mid-latitudes (∼ 30 %, 30–60∘ N) and high northern latitudes (∼ 4 %, 60–90∘ N). The most important source of uncertainty in the methane budget is attributable to natural emissions, especially those from wetlands and other inland waters. Some of our global source estimates are smaller than those in previously published budgets (Saunois et al., 2016 Kirschke et al., 2013). In particular wetland emissions are about 35 Tg CH4 yr−1 lower due to improved partition wetlands and other inland waters. Emissions from geological sources and wild animals are also found to be smaller by 7 Tg CH4 yr−1 by 8 Tg CH4 yr−1, respectively. However, the overall discrepancy between bottom-up and top-down estimates has been reduced by only 5 % compared to Saunois et al. (2016), due to a higher estimate of emissions from inland waters, highlighting the need for more detailed research on emissions factors. Priorities for improving the methane budget include (i) a global, high-resolution map of water-saturated soils and inundated areas emitting methane based on a robust classification of different types of emitting habitats (ii) further development of process-based models for inland-water emissions (iii) intensification of methane observations at local scales (e.g., FLUXNET-CH4 measurements) and urban-scale monitoring to constrain bottom-up land surface models, and at regional scales (surface networks and satellites) to constrain atmospheric inversions (iv) improvements of transport models and the representation of photochemical sinks in top-down inversions and (v) development of a 3D variational inversion system using isotopic and/or co-emitted species such as ethane to improve source partitioning. The data presented here can be downloaded from 0.18160/GCP-CH4-2019 (Saunois et al., 2020) and from the Global Carbon Project.
Publisher: Springer Science and Business Media LLC
Date: 18-01-2023
Publisher: Elsevier BV
Date: 11-2021
Publisher: American Association for the Advancement of Science (AAAS)
Date: 06-2018
Abstract: Water and sediment methane emissions have the potential to offset “blue carbon” burial in mangrove coastal ecosystems.
Publisher: Elsevier BV
Date: 12-2018
Publisher: Elsevier
Date: 2021
Publisher: Elsevier BV
Date: 10-2018
Publisher: American Geophysical Union (AGU)
Date: 10-2021
DOI: 10.1029/2021JG006270
Abstract: High global uncertainties remain in water‐air CO 2 , CH 4 , and N 2 O fluxes from estuaries due to spatial and temporal variability and the poor predictability of the gas transfer velocity ( k 600 ). This is the first study that directly compares k 600 of CO 2 , CH 4 , and N 2 O in an estuary with the aim to evaluate the accuracy of using a uniform k 600 value for estimating water‐air fluxes. We calculated 155 k 600 values from CO 2 , CH 4 , and N 2 O fluxes over spatial (across, along) and temporal (tidal cycle) surveys in the subtropical Maroochy estuary using the floating chamber method. Combined k 600 values showed a large range over the entire estuary (0.1–198.6 cm h −1 ) with slightly lower k 600 in the lower compared to the upper estuary. Overall, temporal variability was greater than spatial variability of k 600 . We found the highest variability of k 600 between gas species in the lower estuary, whereas the variability was less distinct in the upper estuary. In the Maroochy estuary, k 600 CO 2 (mean 26.4 ± 37.3 cm h −1 ) was mostly higher than k 600 CH 4 (mean 10.9 ± 10.6 cm h −1 ) and k 600 N 2 O (mean 9.9 ± 12.3 cm h −1 ), likely due to chemical and enzymatic enhancements and/or microbial activity in the surface microlayer. We demonstrate that empirical k 600 models intended for CO 2 may not accurately predict CH 4 and N 2 O fluxes in estuaries. Our tested k 600 models predicted the measured fluxes within an uncertainty range of 5%–40% (over or underestimation), but precise flux estimates should be based on in situ k 600 of all three gases.
Publisher: Springer Science and Business Media LLC
Date: 04-2021
Publisher: Springer Science and Business Media LLC
Date: 13-10-2023
Publisher: Elsevier BV
Date: 04-2020
Publisher: Wiley
Date: 15-10-2021
Publisher: Cold Spring Harbor Laboratory
Date: 26-05-2019
DOI: 10.1101/650705
Abstract: Estuarine N 2 O emissions contribute to the atmospheric N 2 O budget, but little is known about estuary N 2 O fluxes under low dissolved inorganic nitrogen (DIN) conditions. We present high-resolution spatial surveys of N 2 O concentrations and water-air fluxes in three low-DIN (NO 3 − 30 µ mol L −1 ) tropical estuaries in Queensland, Australia (Johnstone River, Fitzroy River, Constant Creek) during consecutive wet and dry seasons. Constant Creek had the lowest concentrations of dissolved inorganic nitrogen (DIN 0.01 to 5.4 µ mol L −1 of NO 3 − and 0.09 to 13.6 µ mol L −1 of NH 4 + ) and N 2 O (93–132% saturation), and associated lowest N 2 O emissions (– 1.4 to 8.4 µ mol m −2 d −1 ) in both seasons. The other two estuaries exhibited higher DIN inputs and higher N 2 O emissions. The Johnstone River Estuary had the highest N 2 O concentrations (97–245% saturation) and emissions (– 0.03 to 25.7 µ mol m −2 d −1 ), driven by groundwater inputs from upstream sources, with increased N 2 O input in the wet season. In the Fitzroy River Estuary, N 2 O concentrations (100–204% saturation) and emissions (0.03–19.5 µ mol m −2 d −1 ) were associated with wastewater inputs, which had a larger effect during the dry season and were diluted during the wet season. Overall N 2 O emissions from the three tropical estuaries were low compared to previous studies, and at times water-air N 2 O fluxes were actually negative, indicating that N 2 O consumption occurred. Low water column NO 3 − concentration (i.e. 5 µ mol L −1 ) appears to promote negative water-air N 2 O fluxes in estuary environments considering the number of estuaries and mangrove creeks where DIN falls below this threshold, negative water-air N 2 O fluxes are likely common.
Publisher: American Geophysical Union (AGU)
Date: 05-2018
DOI: 10.1029/2017GB005826
Publisher: American Geophysical Union (AGU)
Date: 02-2021
DOI: 10.1029/2020GB006858
Abstract: The role of coastal wetlands as natural ‘blue carbon’ sinks may be counter‐acted by emissions of methane (CH 4 ) and nitrous oxide (N 2 O). Site‐specific fluxes of these two potent greenhouse gases from coastal wetlands show high spatial and temporal variability , making global estimates sensitive to statistical assumptions and uncertainties. Here, we review the magnitude of CH 4 and N 2 O fluxes from mangroves, saltmarshes and seagrasses and identify direct and indirect drivers that can control production and consumption pathways. Significant research is required to better quantify fluxes and to understand factors causing flux variability from different transport pathways before restoration of coastal blue carbon ecosystems can be reliably used for climate mitigation.
Publisher: IOP Publishing
Date: 07-2023
Abstract: The BlueFlux field c aign, supported by NASA’s Carbon Monitoring System, will develop prototype blue carbon products to inform coastal carbon management. While blue carbon has been suggested as a nature-based climate solution (NBS) to remove carbon dioxide (CO 2 ) from the atmosphere, these ecosystems also release additional greenhouse gases (GHGs) such as methane (CH 4 ) and are sensitive to disturbances including hurricanes and sea-level rise. To understand blue carbon as an NBS, BlueFlux is conducting multi-scale measurements of CO 2 and CH 4 fluxes across coastal landscapes, combined with long-term carbon burial, in Southern Florida using chambers, flux towers, and aircraft combined with remote-sensing observations for regional upscaling. During the first deployment in April 2022, CO 2 uptake and CH 4 emissions across the Everglades National Park averaged −4.9 ± 4.7 μ mol CO 2 m −2 s −1 and 19.8 ± 41.1 nmol CH 4 m −2 s −1 , respectively. When scaled to the region, mangrove CH 4 emissions offset the mangrove CO 2 uptake by about 5% (assuming a 100 year CH 4 global warming potential of 28), leading to total net uptake of 31.8 Tg CO 2 -eq y −1 . Subsequent field c aigns will measure diurnal and seasonal changes in emissions and integrate measurements of long-term carbon burial to develop comprehensive annual and long-term GHG budgets to inform blue carbon as a climate solution.
Publisher: American Geophysical Union (AGU)
Date: 09-2021
DOI: 10.1029/2021JG006418
Abstract: Isoprene is an important biogenic volatile organic compound with atmospheric emissions contributing to climate regulation. Because isoprene is predominantly sourced terrestrially, there is limited knowledge on the role it might play in marine systems. Here, we report for the first time isoprene concentrations and tidal fluxes from two subtropical mangrove creeks in Moreton Bay, Queensland, Australia: Jacob's Creek and Turkey Boat Creek in 2017 and 2019. Isoprene concentrations tracked the tide height with higher concentrations at high tide and lower concentrations at low tide in both creek systems, showing that isoprene was imported into the creeks on the flood tide. Mangrove creeks in Moreton Bay were a sink (−9.53 ± 9.10 nmol m −2 h −1 ) for isoprene. Isoprene was most likely produced in the open water by either phytoplankton or nearby seagrass beds and then consumed by bacterial communities as a carbon source within the mangrove creek sediments. Mangrove creeks in Moreton Bay are estimated to uptake isoprene at a rate of −6 mg m −2 y −1 , leading to a total global isoprene sink of −0.69 Gg C y −1 . While only a small component of the global marine atmospheric flux of 11,600 Gg C y −1 , isoprene constitutes an important functional link between marine ecosystems.
Publisher: Authorea, Inc.
Date: 30-10-2023
Start Date: 06-2020
End Date: 12-2025
Amount: $354,935.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2024
End Date: 12-2026
Amount: $434,042.00
Funder: Australian Research Council
View Funded Activity