Periodic Reporting for period 2 - RIV-ESCAPE (RIVEr emissions of greenhouse gases from warming landSCAPEs)
Reporting period: 2023-12-01 to 2025-05-31
Summary of the context and overall objectives of the project
Large amounts of carbon dioxide (CO2) and methane (CH4) are released from the surface of rivers each year, with global estimates that total over 2 PgC yr-1. The fluxes are larger than the net removal of anthropogenic CO2 to the land surface of 1.6 ± 0.5 PgC yr-1, meaning that river CO2 and CH4 release could act as a leak of carbon (C) back to the atmosphere over the coming decades. However, we have been unable to assess how much these fluxes could change, and if C may be emitted from old, seemingly stable stores on land from the surface of rivers to the atmosphere.
To move beyond the current state-of-the-art, the ultimate aim of RIV-ESCAPE is to determine how greenhouse gas emissions from rivers will impact the future trajectory of atmospheric CO2 and CH4 concentrations. There are three key questions: i) how does C supply from landscapes combine with river flow to drive CO2 and CH4 release from rivers and link C emissions to climate? ii) do high latitude rivers in peatland and permafrost regions release old C as CO2 and CH4? and iii) how will the age, source and fluxes of CO2 and CH4 from rivers respond to ongoing and future warming?
To deliver on these research gaps with a step change in our understanding of this major C flux, the RIV-ESCAPE team are currently working on three Objectives:
Objective 1 (O1): Quantify the release of CO2 and CH4 from rivers at high spatial and temporal resolution at nested scales, tracking gases into streams and larger rivers. This will establish, for the first time, the detail of how C inputs, catchment characteristics and river dynamics combine to govern the fluxes.
Objective 2 (O2): Measure the 14C activity of river CO2 and CH4 over space and time, in combination with novel isotope geochemical methods, to quantify the C age and sources of C to reveal the key processes and their controls.
Objective 3 (O3): Combine the new empirical data to provide transferable understanding of how and why river CO2 and CH4 age, source and flux change with land use and hydro-climate. These will allow us to better predict the magnitude of change and uncertainty in this carbon flux over the coming century.
RIV-ESCAPE will transform our understanding with novel field campaigns to challenging environments that measure CO2 and CH4 concentration and flux, while quantifying river flow and collecting samples for geochemical fingerprinting. We are focused on CO2 and CH4 release from high latitude rivers, which drain old C stocks that are warming rapidly. These include quantifying CO2 and CH4 fluxes and biogeochemical pathways in streams Northern Hemisphere peatlands of the Isle of Lewis, UK, alongside streams and rivers in permafrost zones of the Canadian Arctic. We are also focused on mountainous Arctic rivers where chemical weathering and carbon transfers are impacting river greenhouse source and flux.
The RIV-ESCAPE team have continued to develop, refine and apply cutting-edge methods to sample CO2 and CH4 for stable and radioactive isotope measurements to constrain C source and age, alongside a full suite of complementary approaches to track carbon across the land to ocean conveyor. The new empirical data across gradients in climate, land use and disturbances will be combined to assess for the first time how river CO2 and CH4 emissions will increase under a warming climate. These outputs help to better constrain the fate of anthropogenic C emissions, while reducing uncertainties on carbon cycle – climate feedbacks (e.g. via permafrost thaw), both issues of societal relevance.
To move beyond the current state-of-the-art, the ultimate aim of RIV-ESCAPE is to determine how greenhouse gas emissions from rivers will impact the future trajectory of atmospheric CO2 and CH4 concentrations. There are three key questions: i) how does C supply from landscapes combine with river flow to drive CO2 and CH4 release from rivers and link C emissions to climate? ii) do high latitude rivers in peatland and permafrost regions release old C as CO2 and CH4? and iii) how will the age, source and fluxes of CO2 and CH4 from rivers respond to ongoing and future warming?
To deliver on these research gaps with a step change in our understanding of this major C flux, the RIV-ESCAPE team are currently working on three Objectives:
Objective 1 (O1): Quantify the release of CO2 and CH4 from rivers at high spatial and temporal resolution at nested scales, tracking gases into streams and larger rivers. This will establish, for the first time, the detail of how C inputs, catchment characteristics and river dynamics combine to govern the fluxes.
Objective 2 (O2): Measure the 14C activity of river CO2 and CH4 over space and time, in combination with novel isotope geochemical methods, to quantify the C age and sources of C to reveal the key processes and their controls.
Objective 3 (O3): Combine the new empirical data to provide transferable understanding of how and why river CO2 and CH4 age, source and flux change with land use and hydro-climate. These will allow us to better predict the magnitude of change and uncertainty in this carbon flux over the coming century.
RIV-ESCAPE will transform our understanding with novel field campaigns to challenging environments that measure CO2 and CH4 concentration and flux, while quantifying river flow and collecting samples for geochemical fingerprinting. We are focused on CO2 and CH4 release from high latitude rivers, which drain old C stocks that are warming rapidly. These include quantifying CO2 and CH4 fluxes and biogeochemical pathways in streams Northern Hemisphere peatlands of the Isle of Lewis, UK, alongside streams and rivers in permafrost zones of the Canadian Arctic. We are also focused on mountainous Arctic rivers where chemical weathering and carbon transfers are impacting river greenhouse source and flux.
The RIV-ESCAPE team have continued to develop, refine and apply cutting-edge methods to sample CO2 and CH4 for stable and radioactive isotope measurements to constrain C source and age, alongside a full suite of complementary approaches to track carbon across the land to ocean conveyor. The new empirical data across gradients in climate, land use and disturbances will be combined to assess for the first time how river CO2 and CH4 emissions will increase under a warming climate. These outputs help to better constrain the fate of anthropogenic C emissions, while reducing uncertainties on carbon cycle – climate feedbacks (e.g. via permafrost thaw), both issues of societal relevance.
Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far
The first 18 months of RIV-ESCAPE have focused on Objectives 1 and 2, while also starting to contribute to upscaling across landscapes using new and complied datasets in Objective 3.
We have designed and delivered four major field campaigns in the Mackenzie River system, focusing on a major Arctic river delta, large river tributaries and mountainous rivers. These trips map directly onto the proposed research plans in Objectives 1 and 2. In 2023, logistical challenges associated with unprecedented wildfires lead to the provincial capital of the Northwest Territories being evacuated and all research activities in our field region halted. Working closely with our collaborators in Canada, we re-designed a safe trip in October 2023 which captured the “shoulder season”. During this period, the river cools and starts to freeze, and it has never been sampled before for river greenhouse gases.
The field campaign in October 2023 visited key sites in the Mackenzie River delta and upstream. Deploying RIV-ESCAPEs novel field equipment and modified sampling methods, we achieved the first measurements of CH4 flux from systems like these (Objective 1), while also delivering the first ever river CH4 samples for radiocarbon dating (Objective 2). We collected samples that will be used to quantify the thermal stability and age of river organic carbon sources for the first time.
To provide crucial insight on seasonal variability in greenhouse gas production and export, we planned and delivered three distinct field campaigns across June and July 2024. First, we sampled sites from October 2023 to provide this necessary temporal context, while also running a short research cruise from upstream to downstream transect into the river delta. The second campaign focused on catchments draining discontinuous permafrost, while the final campaign visited mountain rivers where weathering reactions are changing dramatically. The resulting data and samples are the backbone of complementary research strands led by PI Hilton, PDRA Dasari, PDRA Mena Rivera, and PhD Sulikova.
Alongside the Arctic River fieldwork, we have designed and delivered comprehensive and regular sampling of streams and rivers draining one of the largest peatlands in Europe on the Isle of Lewis, UK (feeding into Balwin’s PhD). The key research themes include capturing the spatial and temporal variability of river greenhouse gases in northern hemisphere peatland environments, while also tracking land use change (gradients in peat cutting and peat extraction) and wildfire impacts.
We have deployed novel instrumentation to test methods and gather first of a kind data at a local field site on the River Thames. There, we are currently testing how Eddy Covariance methods can provide temporal constraint on river greenhouse gas emissions, while also assessing CO2 and CH4 production and riverine release in an urbanised catchment.
Compiling published and new river greenhouse gas measurements has started to deliver on Objectives 3. PI Hilton has co-led a global data analysis of river CO2 source using radiocarbon with project partner (Dean). This work is currently a paper under review, and suggests that old carbon is a larger contributor to river CO2 emissions than previously recognised, with implications for how we model the storage of anthropogenic C on land.
The major results so far can be linked to the published outputs and dissemination include:
- Quantifying the temperature sensitivity of mineral permafrost feedback at the continental scale using river data and weathering models (Walsh, Hilton et al., 2024, Science Advances).
- The first published measurements of the radiocarbon age of dissolved inorganic carbon from a major Arctic River, finding a coupled role for weathering and organic matter degradation (Dasari, Hilton, Garnett, 2024, PNAS Nexus).
- Preliminary measurements from RIV-ESCAPE, across space and time using multiple methods, have been presented by all research team members (Hilton, Dasari, Baldwin, Sulikova, Mena Rivera) at national and international scientific conferences, including invited talks (EGU 2023 and Goldschmidt 2023).
- Invited research seminars in UK and international Universities (Hilton, Dasari).
- Chairing of a session at Goldschmidt 2025 (Hilton, Dasari) on “River greenhouse gases: Tracking fluxes, sources, processes and vectors of change”.
- An invited perspective article on the hydrological and climate controls on weathering carbon emissions and pathways (Hilton, 2024, Nature Water)
- Re-assessment of global soil radiocarbon composition, showing an important role for rock organic carbon in deep soils (e.g. Grant et al., 2023, Geochemical Perspective Letters).
- An invited perspective article on how climate controls weathering and the impacts on atmospheric CO2 (Hilton, 2023, Science).
- A review of organic carbon transfers in global rivers and updated compilation of radiocarbon measurements from rivers (Hilton et al., 2024, Treatise of Geochemistry)
We have designed and delivered four major field campaigns in the Mackenzie River system, focusing on a major Arctic river delta, large river tributaries and mountainous rivers. These trips map directly onto the proposed research plans in Objectives 1 and 2. In 2023, logistical challenges associated with unprecedented wildfires lead to the provincial capital of the Northwest Territories being evacuated and all research activities in our field region halted. Working closely with our collaborators in Canada, we re-designed a safe trip in October 2023 which captured the “shoulder season”. During this period, the river cools and starts to freeze, and it has never been sampled before for river greenhouse gases.
The field campaign in October 2023 visited key sites in the Mackenzie River delta and upstream. Deploying RIV-ESCAPEs novel field equipment and modified sampling methods, we achieved the first measurements of CH4 flux from systems like these (Objective 1), while also delivering the first ever river CH4 samples for radiocarbon dating (Objective 2). We collected samples that will be used to quantify the thermal stability and age of river organic carbon sources for the first time.
To provide crucial insight on seasonal variability in greenhouse gas production and export, we planned and delivered three distinct field campaigns across June and July 2024. First, we sampled sites from October 2023 to provide this necessary temporal context, while also running a short research cruise from upstream to downstream transect into the river delta. The second campaign focused on catchments draining discontinuous permafrost, while the final campaign visited mountain rivers where weathering reactions are changing dramatically. The resulting data and samples are the backbone of complementary research strands led by PI Hilton, PDRA Dasari, PDRA Mena Rivera, and PhD Sulikova.
Alongside the Arctic River fieldwork, we have designed and delivered comprehensive and regular sampling of streams and rivers draining one of the largest peatlands in Europe on the Isle of Lewis, UK (feeding into Balwin’s PhD). The key research themes include capturing the spatial and temporal variability of river greenhouse gases in northern hemisphere peatland environments, while also tracking land use change (gradients in peat cutting and peat extraction) and wildfire impacts.
We have deployed novel instrumentation to test methods and gather first of a kind data at a local field site on the River Thames. There, we are currently testing how Eddy Covariance methods can provide temporal constraint on river greenhouse gas emissions, while also assessing CO2 and CH4 production and riverine release in an urbanised catchment.
Compiling published and new river greenhouse gas measurements has started to deliver on Objectives 3. PI Hilton has co-led a global data analysis of river CO2 source using radiocarbon with project partner (Dean). This work is currently a paper under review, and suggests that old carbon is a larger contributor to river CO2 emissions than previously recognised, with implications for how we model the storage of anthropogenic C on land.
The major results so far can be linked to the published outputs and dissemination include:
- Quantifying the temperature sensitivity of mineral permafrost feedback at the continental scale using river data and weathering models (Walsh, Hilton et al., 2024, Science Advances).
- The first published measurements of the radiocarbon age of dissolved inorganic carbon from a major Arctic River, finding a coupled role for weathering and organic matter degradation (Dasari, Hilton, Garnett, 2024, PNAS Nexus).
- Preliminary measurements from RIV-ESCAPE, across space and time using multiple methods, have been presented by all research team members (Hilton, Dasari, Baldwin, Sulikova, Mena Rivera) at national and international scientific conferences, including invited talks (EGU 2023 and Goldschmidt 2023).
- Invited research seminars in UK and international Universities (Hilton, Dasari).
- Chairing of a session at Goldschmidt 2025 (Hilton, Dasari) on “River greenhouse gases: Tracking fluxes, sources, processes and vectors of change”.
- An invited perspective article on the hydrological and climate controls on weathering carbon emissions and pathways (Hilton, 2024, Nature Water)
- Re-assessment of global soil radiocarbon composition, showing an important role for rock organic carbon in deep soils (e.g. Grant et al., 2023, Geochemical Perspective Letters).
- An invited perspective article on how climate controls weathering and the impacts on atmospheric CO2 (Hilton, 2023, Science).
- A review of organic carbon transfers in global rivers and updated compilation of radiocarbon measurements from rivers (Hilton et al., 2024, Treatise of Geochemistry)
Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)
RIV-ESCAPE research so far has led to several novel developments which provide the grounding for outputs that can go beyond the state of the art.
We have modified and applied novel sample collection methods for CH4 radiocarbon samples. This has allowed us to collect the first paired measurement of river CO2 and CH4 flux and sample collection from Arctic Rivers in Canada, and on the Isle of Lewis, sampling across gradients in peatland characteristics. In total, this has produced ~45 samples for CH4 radiocarbon analyses and ~60 samples for CO2 radiocarbon analyses. To put these efforts in context, there are <70 published measurements of CH4 from rivers at present. These radiocarbon measurements, coupled to stable isotope geochemistry, will provide the first clear picture of how CO2 and CH4 are routed from peatlands and permafrost landscapes into river systems. It is the only way to track if old, previously stable carbon stores are contributing to river greenhouse gas emissions. We are the only project to combine these measurements will stable isotopes, water geochemistry and direct flux measurements, allowing us to move forward on the controls on greenhouse gas release, providing much needed insight on how these fluxes might change in the future.
Our synthesis of large river geochemical datasets have provided the first assessment of the temperature sensitivity of the mineral permafrost carbon cycle feedback at the continental scale. We used a 60-year sulfate concentration dataset from catchments across the Mackenzie River Basin and found sulfate fluxes increased by 45% in the mainstem with 2.3°C of warming. The temperature sensitivity suggests that continental-scale CO2 fluxes could double by 2100. We completed a geospatial analysis and found that the largest increases occur in catchments with geomorphic settings which act to rapidly expose rocks through physical weathering and thermokarst processes. A weathering model was used to explore the underlying drivers, and suggested that warming can increase reaction rates, but changes in the exposure of minerals by physical weathering processes with warming are also required. Future warming across vast Arctic landscapes could further increase sulfide oxidation rates and affect regional carbon cycle budgets. We continue to develop this research theme by tracking the fate of carbon in mountain streams and rivers.
We have built, tested and deployed a range of novel field and laboratory-based instrumentation. First, we have used mobile CO2 and CH4 analysers to measure coupled greenhouse gas fluxes across spatial and temporal gradients in northern peatlands and permafrost landscapes. We have collected this data alongside water geochemistry (major and trace element geochemistry) and carbon isotopes to provide data on the biogeochemical processes responsible for the CO2 and CH4 production and export. We have made detailed measurements of hydrology alongside river greenhouse gas fluxes. We have built and tested novel laboratory instruments to quantify thermal stability and age of organic matter in landscapes, and link them to greenhouse gas production.
The expected results until the end of the project are closely linked to the proposed outputs from the Description of Action, and can be broadly summarised as follows:
Research that is completed or underway, with some results presented at conferences and/or published in scientific papers:
- Quantifying the temperature control on increasing sulfide oxidation and CO2 release across the Mackenzie River Basin (Walsh et al., 2024)
- Age of dissolved inorganic carbon in a major Arctic River (Dasari et al., 2024)
- A global river radiocarbon CO2 and DIC database, used to assess the role of old C in the global release from rivers (Dean et al., in review)
- The impact of wildfire on river carbon species and greenhouse gases (Isle of Lewis) (Mena Rivera et al., in prep.)
- The first coupled CH4 flux and composition (radiocarbon, stable isotopes) from a major Arctic river system and its delta. (Dasari et al., in prep.)
- CO2 emissions and sources across an Andean to Amazon transect (Hilton et al., in prep.)
Research that has recently started:
- Quantifying the thermal stability and age of organic carbon across Arctic landscapes using Ramped oxidation methods.
- The rates and drivers of CO2 emissions from Arctic mountain rivers.
- Novel instrumentation to continuously measure CO2 and CH4 release from river surfaces, with installation on the River Thames, UK (Eddy Covariance).
- River methane release from an urbanised river watershed (River Thames UK).
- Export of greenhouse gases by rivers from across an entire northern peatland (Isle of Lewis).
Research that has gathered samples/ data but is yet to start, or is still in planning stages:
- Metagenomic approaches to understanding greenhouse gas production in Arctic Rivers
- Isotopic tracers of mineral weathering and coupled CO2 release from rivers in permafrost environments
- Mackenzie River fluvial carbon fluxes and spatial and temporal patterns of greenhouse gas release
- Establishing how land use change in peatlands impacts river greenhouse gas fluxes
- CO2 and CH4 release from deglaciating permafrost environments (Svalbard)
- Geospatial data analysis and numerical modelling of CH4 and CO2 source and fluxes from high latitude rivers, with implications for atmospheric composition.
We have modified and applied novel sample collection methods for CH4 radiocarbon samples. This has allowed us to collect the first paired measurement of river CO2 and CH4 flux and sample collection from Arctic Rivers in Canada, and on the Isle of Lewis, sampling across gradients in peatland characteristics. In total, this has produced ~45 samples for CH4 radiocarbon analyses and ~60 samples for CO2 radiocarbon analyses. To put these efforts in context, there are <70 published measurements of CH4 from rivers at present. These radiocarbon measurements, coupled to stable isotope geochemistry, will provide the first clear picture of how CO2 and CH4 are routed from peatlands and permafrost landscapes into river systems. It is the only way to track if old, previously stable carbon stores are contributing to river greenhouse gas emissions. We are the only project to combine these measurements will stable isotopes, water geochemistry and direct flux measurements, allowing us to move forward on the controls on greenhouse gas release, providing much needed insight on how these fluxes might change in the future.
Our synthesis of large river geochemical datasets have provided the first assessment of the temperature sensitivity of the mineral permafrost carbon cycle feedback at the continental scale. We used a 60-year sulfate concentration dataset from catchments across the Mackenzie River Basin and found sulfate fluxes increased by 45% in the mainstem with 2.3°C of warming. The temperature sensitivity suggests that continental-scale CO2 fluxes could double by 2100. We completed a geospatial analysis and found that the largest increases occur in catchments with geomorphic settings which act to rapidly expose rocks through physical weathering and thermokarst processes. A weathering model was used to explore the underlying drivers, and suggested that warming can increase reaction rates, but changes in the exposure of minerals by physical weathering processes with warming are also required. Future warming across vast Arctic landscapes could further increase sulfide oxidation rates and affect regional carbon cycle budgets. We continue to develop this research theme by tracking the fate of carbon in mountain streams and rivers.
We have built, tested and deployed a range of novel field and laboratory-based instrumentation. First, we have used mobile CO2 and CH4 analysers to measure coupled greenhouse gas fluxes across spatial and temporal gradients in northern peatlands and permafrost landscapes. We have collected this data alongside water geochemistry (major and trace element geochemistry) and carbon isotopes to provide data on the biogeochemical processes responsible for the CO2 and CH4 production and export. We have made detailed measurements of hydrology alongside river greenhouse gas fluxes. We have built and tested novel laboratory instruments to quantify thermal stability and age of organic matter in landscapes, and link them to greenhouse gas production.
The expected results until the end of the project are closely linked to the proposed outputs from the Description of Action, and can be broadly summarised as follows:
Research that is completed or underway, with some results presented at conferences and/or published in scientific papers:
- Quantifying the temperature control on increasing sulfide oxidation and CO2 release across the Mackenzie River Basin (Walsh et al., 2024)
- Age of dissolved inorganic carbon in a major Arctic River (Dasari et al., 2024)
- A global river radiocarbon CO2 and DIC database, used to assess the role of old C in the global release from rivers (Dean et al., in review)
- The impact of wildfire on river carbon species and greenhouse gases (Isle of Lewis) (Mena Rivera et al., in prep.)
- The first coupled CH4 flux and composition (radiocarbon, stable isotopes) from a major Arctic river system and its delta. (Dasari et al., in prep.)
- CO2 emissions and sources across an Andean to Amazon transect (Hilton et al., in prep.)
Research that has recently started:
- Quantifying the thermal stability and age of organic carbon across Arctic landscapes using Ramped oxidation methods.
- The rates and drivers of CO2 emissions from Arctic mountain rivers.
- Novel instrumentation to continuously measure CO2 and CH4 release from river surfaces, with installation on the River Thames, UK (Eddy Covariance).
- River methane release from an urbanised river watershed (River Thames UK).
- Export of greenhouse gases by rivers from across an entire northern peatland (Isle of Lewis).
Research that has gathered samples/ data but is yet to start, or is still in planning stages:
- Metagenomic approaches to understanding greenhouse gas production in Arctic Rivers
- Isotopic tracers of mineral weathering and coupled CO2 release from rivers in permafrost environments
- Mackenzie River fluvial carbon fluxes and spatial and temporal patterns of greenhouse gas release
- Establishing how land use change in peatlands impacts river greenhouse gas fluxes
- CO2 and CH4 release from deglaciating permafrost environments (Svalbard)
- Geospatial data analysis and numerical modelling of CH4 and CO2 source and fluxes from high latitude rivers, with implications for atmospheric composition.