Displays

Water level fluctuations affect many ecosystem processes in tropical peatlands, and have important practical implications because low water tables cause decomposition and flammability.  In recent work, we showed that a simplified model driven by precipitation and evapotranspiration can work surprisingly well at predicting water table fluctuations in the interior of ombrotrophic tropical peatlands.  However, a model driven only by precipitation and evaporation cannot give accurate predictions of water table dynamics at the dome edge, where important fire and flood processes occur. Further, changing boundary conditions from tides and seasonal changes in river stage can drive fluctuations that propagate towards the dome interior.  Classic studies of how such fluctuations at edges propagate into the interior of a domain provide solid theory for simple aquifers with constant and uniform transmissivity or conductivity, but tropical peatlands are not described well by these models because of the much higher conductivity of peat near the surface. We explore how precipitation, evapotranspiration, and changes in river or channel stage interact to drive water table fluctuations in tropical peat domes using an exponential transmissivity model previously validated for a tropical peatland.  We discuss these "edge effects" and their frequency-dependent range of influence from fluctuations on diurnal, monthly, annual, and superannual time scales.

How to cite: Cobb, A., Thamilselvam, S. K., Zulkiflee, R., Incham, J. M., Ideris, K., Metali, F., Sukri, R. S., and Harvey, C.: Edge effects on water table dynamics in tropical peatlands, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20759, https://doi.org/10.5194/egusphere-egu2020-20759, 2020.

Hydrology plays a pivotal role in the geomorphology and carbon balance of tropical peatlands. The alteration of the hydrological processes due to climate and/or land cover change might result in significant impacts to this ecosystem. Therefore, improved understanding of tropical peatland hydrology is critical in order to evaluate their fate under current and future climate and ultimately to develop sustainable peatland management practices. However, due to its complexity related to various flow interactions and anthropogenic interferences, comprehensive hydrological studies based on measured field data on tropical peatlands are still limited. Alternatively, hydrological models have been used to simulate the major components of the hydrological processes and to answer “what-if” questions.

In this context, a fully distributed and physically-based MIKE SHE model was used to simulate the water balance within Padang Island in the eastern coast of Sumatra, Indonesia. The island is characterized as a mosaic landscape of natural forest, forest plantation and smallholder agriculture. Comprehensive data set from field measurements including high resolution digital terrain model derived from airborne LiDAR were used for the model development. The model was calibrated and validated against observed groundwater level and stream flow data distributed across the island. The simulation was performed using current climate data that cover a distinct dry and wet year. The subsidence impacts were investigated by simulating the future projection up to 50 years. Further, additional scenario was developed to represent the pre-existing condition without agriculture and forestry practices to evaluate the land cover change impacts.

The results show that the water balance is predominantly controlled by climatic variables. The evapotranspiration accounts for the main water loss representing 50 – 80 % of the total annual rainfall. The amount of evapotranspiration remains relatively constant in the temporal basis irrespective to the rainfall, which means that the magnitude and direction of the remaining hydrological flow paths are driven by the balance between rainfall and evapotranspiration. In the dry period with a rainfall deficit, the water storage is depleted in order to meet the evapotranspiration demand. In the wet period, the excess rainfall is transformed into overland flow, base flow and positive storage change which contributes to increased inundation frequency.

The future projection indicates that there is a shift in the hydrological flow path, as the overland flow increases and the groundwater flow decreases due to the changing topography from peat subsidence. However, the hydrological flow path of the natural forest in the central part of the island remains relatively intact. The agriculture and forestry practice doesn’t significantly alter the hydrological flow path compared to the pre-existing condition. In addition, the boundary impact to the natural forest is not apparent under the wet period, while it gets more prominent in the dry period (~300 meter under current condition).

Our results, which are among the first comprehensive hydrological studies for the tropical peatlands, should help to improve the understanding of landscape scale hydrological processes in tropical peatland, which is relevant for scientists and policymakers to develop science-based peatland management practices.

How to cite: Asyhari, A., Tanjungsari, R. J., Suardiwerianto, Y., Hidayat, M. F., Marpaung, S. M., Harahap, M. I. F., Risky, T. M., and Esprey, L. J.: Understanding Spatial and Temporal Variability of Water Balance from Tropical Peatland Landscape, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12136, https://doi.org/10.5194/egusphere-egu2020-12136, 2020.

Peatlands are integral to sustaining landscape eco-hydrological function in water-limited boreal landscapes and serve as important water sources for headwater streams and surrounding forests, and recently for mega-scale watershed construction associated with resource extraction. Despite the regional moisture deficit of the Boreal plains, peatlands and margin swamps exist on topographic highs where low permeability (clogging) layers occur proximal to the surface and are apparently isolated from surface water and local and regional groundwater inputs. The water generating mechanisms (external water sources, internal feedback mechanisms) that enable peatland formation with such delicate water balances in these unique hydrogeologic settings are not well known, and have large implications for understanding the eco-hydrologic role of natural peatlands as well as direct peatland construction in drier boreal landscapes.

A multi-year sampling campaign was conducted to collect hydrometric, geochemical (DOC, pH, major cations and anions), and isotopic (D/H, ¹⁸O/¹⁶O) data from a small isolated peatland-margin swamp complex. We explored the relative roles of margin swamps in buffering water loss and generating perched groundwater, shading and wind protection from adjacent forests, snow redistribution in and around the peatland, and wetland feedbacks on maintenance of peatland moisture and ecosystem function. Long-term (18 year) records of water table gradients between the peatland and an adjacent forest combined with 3 year high intensity water balance calculations show the peatland to be a source of water to adjacent forests during this period and illustrate the dominance of autogenic wetland feedbacks over allogenic controls (external sources) in peatland development at this location. Contrasts in water storage due to the morphometry of the clogging layer appear to the dominant determinants of peatland and swamp form and function. Layers of decomposed peat and fine textured mineral soils in margin swamps with low water storage potential promoted frequent soil saturation and anoxia, limiting forest vegetation growth and water uptake, further enhancing wetland vegetation, water conservation and generation within the wetland complex. Shading and wind protection from adjacent forests appear to influence soil frost duration and atmospheric demand to further reduce evapotranspiration losses contributing to a slight moisture surplus in the wetland complex relative to the adjacent forest. Understanding the water balance and moisture surplus controls in isolated peatlands sheds light on the relative role of allogenic and autogenic controls on peatlands with implications for: 1) assessing regional eco-hydrological roles of peatland and forestland covers, 2) predicting landscape-scale response to environmental change and land use, and 3) directing landscape scale reclamation or large reconstruction projects over a range of geologic settings in water-limited boreal regions.

How to cite: Devito, K. J., James, L. M., Alessi, D. S., Hokanson, K., Kettridge, N., Little-Devito, M., and Mendoza, C. A.: Perched Peatlands: insights into eco-hydrologic roles of peatlands in water limited boreal environments, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22254, https://doi.org/10.5194/egusphere-egu2020-22254, 2020.

Alkaline fens are listed under Annex 1 of the European Union (EU) Habitats Directive (Council Directive 92/43/EEC, habitat code 7230) as habitats requiring special conservation measures, including the designation of suitable sites as Special Areas of Conservation (SACs). These fens are peat-forming wetlands predominantly fed by groundwater containing significant concentrations of calcium, magnesium and bicarbonate. The hydrogeological dynamics and hydrochemical signature supports small sedge and brown moss communities in a mosaic of different habitats. Despite fens being an important part of the natural landscape in Ireland as well as one of the most threatened wetland habitats in Europe, there is little information on the hydrology and hydrochemistry that support these habitats. As part of a three year research project (Ecometrics) on GWDTE’s (Groundwater Dependent Terrestrial Ecosystems) an intensive hydrochemical monitoring programme was established on four Irish fen sites, designated as SACs, covering an eco-hydrological gradient from intact to highly degraded conditions. Ground and surface waters monitoring started in July 2018 with spot measurements supplemented by a continuous water table time series collected every two months. Simultaneously ground and surface water samples were taken and analysed for nutrients, mayor ions and metals. Topographical surveys as well as vegetation surveys were carried out in 2019. The hydrological and hydro-chemical evidence from each fen were then collated to build conceptual eco-hydrological models to represent both temporal and spatial variability in each geological setting. In addition, remote sensing was used in order to investigate the relationship between vegetation and water levels. Utilising ground surveyed habitat map and Sentinel-2 (S2) imagery in a Random Forest model a remotely sensed vegetation map was created. This information was then correlated with water level data as follows: hydrological data were interpolated over the entire area of the fen, giving seasonal information for both surface and groundwater levels. Using K-means clustering, the data were divided into clusters which were then matched and correlated with the vegetation map produced through S2 imagery. The strength of the correlation between water level and fen vegetation can further aid the construction of conceptual models for the four research sites. These models will then be used to define appropriate metrics that characterise the environmental supporting conditions in fens, as required for the EU Water Framework Directive. Here, the preliminary conceptual models for fen functioning will be presented as they are continuously updated by the ongoing data collection.

How to cite: Bijkerk, E., Bhatnagar, S., Coxon, C., Johnston, P., Regan, S., Waldren, S., and Gill, L.: Investigating hydrological and biogeochemical controls on Irish alkaline fen habitats , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19765, https://doi.org/10.5194/egusphere-egu2020-19765, 2020.

Ombrotrophic blanket mires are significant components of the upland hydrological and biogeochemical cycles, but are scarce in the North York Moors, one of the driest uplands in the British Isles. Our research focuses on a rewilding project centred on May Moss (SSSI), which includes the largest (71 ha) intact, ombrotrophic blanket mire in the North York Moors National Park. The peatland is located on the watershed between the flood-prone River Derwent and Eller Beck (River Esk) catchments. East of the intact mire is a 70.6 ha area managed by the Forestry Commission and planted with Pinus contorta and Picea sitchensis forestry 1975-1983. In 2009, funds received from the SITA Trust (Enriching Nature Programme), facilitated the large-scale removal of forestry and a programme of peatland rewetting.

Since August 2010, adjacent intact and restoring sites on May Moss have been monitored, to assess the hydroclimate controls over intact blanket bog hydrology and the extent of hydrological recovery of a deforested blanket bog. Hourly hydroclimate monitoring includes assessment of the evaporative fluxes and recorded changes in the bog water table. Monitored differences between the sites since 2017 have highlighted their responses to drought, summer water table drawdown and winter recharge, and suggest an incomplete recovery of the deforested site a decade later.

Water samples collected from the intact (Eller Beck) and restoring (Long Grain) catchments every two days since summer 2017, parallel to hourly discharge data, have been analysed for water biochemistry. Parameters include colour (UV-vis spectroscopy), dissolved and particulate organic carbon, dry mass chemistry and organic components (e.g. quantifying fulvic and humic acid proportions by near-infrared spectroscopy). The data show differences in water quality between the intact and recovering catchments, but similarities in temporal patterns and seasonal behaviour. For example, both catchments experienced a significant shift from humic to fulvic acid-dominated that accompanied the water table rise ending the 2018 drought. Sudden changes in the water table appear to produce flushing or changes in water sources within the peatland.

Monthly and replicated campaign-based measurements of net CO₂ exchange rates (NCER) on the intact and restoring sites accompany the biogeochemical time series developed for waters draining May Moss. In addition, we have built and are evaluating prototype low-cost replicated automated Arduino gas flux chambers for measuring CO₂ and CH₄ fluxes as a viable alternative to expensive conventional chamber-based flux systems. Together, the coupled monitoring of aqueous and gaseous C fluxes from both intact and recovering sectors of May Moss parallels hydroclimate analyses that quantify and close the net hydrological budget, and provide a robust basis for assessing the controls over the carbon budget of intact and recovering peatlands.

How to cite: Lehnhart-Barnett, H. and Chiverrell, R.: Rewilding blanket bog from former conifer plantations: hydrological processes, aquatic biogeochemistry and carbon fluxes., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9819, https://doi.org/10.5194/egusphere-egu2020-9819, 2020.

About 30% (0.4 Mha) of German peatlands are located in Lower Saxony and about 65% of these peatlands are used for agriculture, mainly grassland. These peatlands are drained for agricultural use, which creates huge GHG emissions. Grasslands on carbon rich soils are responsible for seven percent of the GHG budget of Lower Saxony. Raising the annual water level to 30 cm below surface or higher should substantially reduce peat oxidation and GHG emissions from such sites, while allowing grassland management or other ways of peatland utilization under wet conditions. Such water levels, however, may be difficult to achieve by high ditch water levels alone, because the low hydraulic conductivity of the degraded peat does not allow sufficient water movement to compensate for evapotranspiration in summer. We hypothesize that subsurface water regulation may allow constant high peatland water levels, because the applied submerged drains form conduits from ditches into the peat that should improve the water exchange.

We tested subsurface water regulation at 1 ha plots on a fen and bog grassland in NW-Germany. Both sites included three treatments: (1) blocked ditches with subsurface water regulation, (2) blocked ditches without subsurface water regulation, and (3) conventional drainage (control). Ditches in treatments (1) and (2) were filled with surface water up to 15 cm below land surface during the growing season using a solar pump. Over a period of three years, we monitored ditch and peatland water levels along transects. We analyzed effects of treatments, ditch water levels, climatic water balance, and saturated water conductivity (kf) on peatland water levels and changes of surface elevation.

Our results show that subsurface water regulation allowed for a better control of peatland water levels as compared to ditch blocking and conventional drainage. In the winter, subsurface water regulation improved drainage, so that water levels within the site were not much higher than the ditch water levels. In the summer, subsurface water regulation allowed to maintain peatland water levels of 30 to 40 cm below surface, more than 20 cm higher compared to both other treatments. Furthermore, subsurface water regulation reduced subsidence. However, despite a narrow drain spacing of four to five meters, it was difficult to maintain the target peatland water levels during very dry summer months albeit the tested years were atypically dry and hot. The differences between ditch water levels and peatland water levels were closely related to the climatic water balance, and the slope of the linear function depended on saturated water conductivity (kf) of the peat. Based on climatic water balances, weir adjustment can be optimized to achieve high and stable peatland water levels. The results help in understanding and analyzing the hydrology of degraded peatlands. This information will prove extremely useful for planning water management measures, which are necessary to reduce the GHG emissions from drained peatlands.

How to cite: Minke, M., Sieber, A. C., Tegge, A., and Höper, H.: Maintenance of high peatland water levels by subsurface water regulation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13704, https://doi.org/10.5194/egusphere-egu2020-13704, 2020.

Peatlands have been intensively used for centuries either for peat extraction, agricultural usage or forestry. The related drainage has led to falling water levels, altered microbial activity and the associated greenhouse gas emissions, the shrinkage of the peat layer and an overall degradation of peatland areas causing the disruption of these ecosystems. Lately, some areas have been restored and brought back to a semi-natural state by prohibiting their use and lifting the water table.

To monitor shrinkage and swelling processes of the peat layer, we applied the Persistent Scatterer Interferometry (PSI, Ferretti et al. 2001) to several upland peatlands south of the city of Munich, Germany, for the period 2015-2018. This technique uses time-series of Synthetic Aperture Radar (SAR) satellite images from the Sentinel 1A and 1B platforms, to monitor potential surface deformation caused by swelling and shrinkage of the peat layer due to water content.

The presentation will show the captured seasonal height fluctuations peatland areas are naturally subject to. The overall trend for the observation period shows a subsidence for most investigated peatlands. Furthermore, we could observe a strong negative trend over most study areas throughout the year 2018. This is expectedly related to the extremely dry conditions in 2018 in this part of Europe which caused the peat layer to dry out and to shrink.

The results illustrate how peatlands react to dry periods. The question remains how resilient peatlands are to droughts, particularly when considering that dry periods may occur more often in the future. In consequence, the findings will also be instrumental to assess the climate mitigation potential of rewetted peatlands. By means of PSI it is possible to monitor surface changes over long time frames and assess the long-term vulnerability of natural and restored peatlands to climate change.

The work presented here is part of the KliMoBay project, funded by the Bavarian State Ministry for the Environment and Consumer Protection through the European Regional Development Fund (ERDF).

Ferretti, A.; Prati, C.; Rocca, F. (2001): Permanent scatterers in SAR interferometry. IEEE Trans. Geosci. Remote Sensing 39 (1), S. 8–20.

How to cite: Huber García, V., Marzahn, P., and Ludwig, R.: Monitoring the drought resilience of near-natural peatlands by means of SAR remote sensing, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2323, https://doi.org/10.5194/egusphere-egu2020-2323, 2020.

This study proposed that due to their high standing water tables that peatlands would be cold humid islands within their landscape relative to farmland on mineral soils. Long term satellite observation of across England’s largest raised bog (t km² former raised bog - Thorne Moors, northern England) showed that as the bog was restored the air temperature over the bog decreased by 1.7 ^oC relative to the surrounding farmland. So this study set out to test this hypothesis with real field observations.

We measured air temperature and humidity at 17 locations along a 7.8 km transect across the Thorne Moors site. Air temperature and humidity were measured hourly for 1 year and supported with spot albedo measurements. The study represented a factorial experiment with respect to sites of measurement; the type of land use (peat vs arable land); and time of sampling over both the seasonal and diurnal cycles. We could show:

• That although mean annual temperature was not significantly different between arable and peatlands the arable land showed a decreased amplitude to its seasonal cycle – this is the reverse of the expected pattern.
• The peatland was colder at night and warmer during the day than the surrounding land.
• The albedo of the peatland was significantly lower than that of arable land showing that vegetated peatland still absorbed more solar radiation.
• The specific humidity was lower on the peatland than on the surrounding arable land.

The study therefore could show that whilst shrubby vegetation exists over a peatland then energy budgets are more likely to be dominated by the greater surface roughness and lower albedo of the vegetated peatland relative to arable land. Thus, shrub-dominated peatlands will not be a cold humid island in their landscape.

How to cite: Worrall, F., Boothroyd, I., Howden, N., Burt, T., Kohler, T., and Gregg, R.: Are peatlands cool humid islands in a landscape?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2556, https://doi.org/10.5194/egusphere-egu2020-2556, 2020.

Europe - especially the northern and middle latitudes - is one of Earth’s mire-rich regions. Among the main distribution areas for mires in Central Europe the coastal region along the southeastern corner of the North Sea (Frisia) shows the highest density of mires. Despite of the important role of mires acting as a carbon sink and modifying the Bowen ratio with influence on screen level meteorological parameters their adequate representation in land-surface schemes used in numerical weather prediction and climate models is still insufficient.

With the recent version 5.06 the COSMO model (Baldauf et al., 2017) offers a parameterization of mires based on Yurova et al. (2014). In this approach the heat diffusion in the vertical domain of the soil multilayer model TERRA is considered with modified equations describing the thermal conductivity for peat with given water/ice contents. The mire hydrology is parameterized by the solution of the Richard's equation in the vertical domain extended by the formulation of a lower boundary condition as a climatological layer of permanent saturation used to simulate the water table position, in conjunction with a mire‐specific evapotranspiration and runoff parameterization.

The impact of the mire parameterization on screen level meteorological parameters and mesoscale processes was investigated in two numerical experiments with COSMO-D2 in a convection permitting limited-area numerical weather prediction (NWP) framework for summer 2018 and winter 2018/2019.

We will present results from the objective verification system and discuss the impact of geospatial physiographic data for an improved representation of mires in the NWP framework.

How to cite: Helmert, J., Yurova, A., Blinov, D., Rozinkina, I., Baldauf, M., Schättler, U., Bettems, J.-M., and Mironov, D.: Numerical experiments with a parameterization of mires in the COSMO-D2 convection permitting limited-area numerical weather prediction framework, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17891, https://doi.org/10.5194/egusphere-egu2020-17891, 2020.

Groundwater table depth and peat moisture content are of crucial importance for many peatland processes, like for example their greenhouse gas budget. Thus, there is a strong need for remote sensing techniques that allow to spatially monitor these critical moisture conditions to quantify the hydrological responses to climate change and other anthropogenic disturbances. Previous studies have demonstrated the usefulness but also limitations of microwave observations for peatland moisture monitoring at the large scale. Here, we explore the potential of techniques based on optical and thermal imagery for smaller scale applications.

Satellite-derived land surface temperature (LST) as well as shortwave infrared transformed reflectance (STR) are sensitive to soil moisture conditions in mineral soils. Both data form, together with remotely sensed vegetation indices (VIs), trapezoids in the LST-VI and STR-VI space with the highest range of possible LST and STR for bare soil conditions. The lowest and highest LST and STR along the vegetation cover gradient define the wet and dry edge, respectively. In this study, we used Landsat 7 and Landsat 8 satellite data for the vegetation periods from 2008 through 2019 to calculate various VIs, LST and STR for hemiboreal raised bogs in Estonia. Two common approaches for the determination of wet and dry edges for the LST-based method were applied and compared. The first approach estimates the edges directly from the observed values of VIs and LST for each scene; while the second one relies on modelled theoretical edges for each scene. In contrast, the STR-VI trapezoid is derived from observed values from all scenes as proposed in literature. The trapezoids are used to calculate the dryness index of each Landsat pixel by linearly scaling between the wet and dry edge. These indices are evaluated with measured groundwater table depth time series. Preliminary results indicate that, for our study area, suitable LST-based trapezoids cannot be derived from satellite observations alone, indicated by the low dependency of the resulting dryness index on groundwater table depth. Evaluation of the theoretically-derived trapezoids and the STR-VI is ongoing and will be discussed.

How to cite: Burdun, I., Sagris, V., Bechtold, M., Komisarenko, V., Mander, Ü., and De Lannoy, G.: Evaluation of Satellite-Based Optical and Thermal Trapezoid Methods for Groundwater Table Depth Monitoring in Estonian Bogs, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10544, https://doi.org/10.5194/egusphere-egu2020-10544, 2020.

Tropical peatlands have a specific hydrology that regulates their internal processes and functioning. External disturbances such as drainage, land cover and land use changes, and climate change could disrupt the peat-specific hydrology and convert the immense peatland carbon stocks into strong greenhouse gas (GHG) emitting sources. The need for (more) accurate monitoring of GHG emissions has led to the development of complex biogeochemical models, which highly depend on proper representation of peat-specific land surface hydrology. However, the latter is often inadequately accounted for in global Earth system modeling frameworks.

In this research, we leverage the PEATCLSM modules recently developed for the Catchment land surface model (CLSM) of the NASA Goddard Earth Observing System framework (Bechtold et al., 2019). These modules were evaluated for northern peatlands, hereafter referred to as PEATCLSM_N. Here, we present an extended version of PEATCLSM for tropical peatlands with literature-based parameter sets for natural (PEATCLSM_T,Natural) and drained (PEATCLSM_T,Drained) tropical peatlands. A suite of modeling experiments was conducted to compare the performance of PEATCLSM_T,Natural, PEATCLSM_T,Drained, PEATCLSM_N, and the currently operational CLSM version that includes peat parameters but no peat-specific model structure (CLSM_O). Simulations over major tropical peatland regions in Southeast Asia, the Congo Basin, and South and Central America were evaluated with a comprehensive and self-compiled dataset of groundwater table depth (WTD) and evapotranspiration (ET). Preliminary results show that the simulated WTD from CLSM_O exhibits too much temporal variability and large biases, either positive or negative. The temporal correlation coefficient between simulated and observed WTD for both PEATCLSM_T,Natural (over undeveloped peatlands only) and PEATCLSM_T,Drained (over drained peatlands only) is similar to that of PEATCLSM_N. However, both tropical versions reduce the average absolute bias to a few centimeters. Performance differences across the major tropical peatland regions are discussed.

Reference: Bechtold, M., De Lannoy, G. J. M., Koster, R. D., Reichle, R. H., Mahanama, S. P., Bleuten, W., et al. (2019). PEAT‐CLSM: A specific treatment of peatland hydrology in the NASA Catchment Land Surface Model. Journal of Advances in Modeling Earth Systems, 11(7), 2130-2162. doi: 10.1029/2018MS001574

How to cite: Apers, S., Bechtold, M., Baird, A. J., Cobb, A. R., Dargie, G., Katimon, A., Koster, R. D., Lampela, M., Mahanama, S. P., Page, S., Reichle, R. H., Vanderborght, J., and De Lannoy, G. J. M. and the collaborators: Integrating tropical peatland hydrology into a global land surface model (PEATCLSM), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17576, https://doi.org/10.5194/egusphere-egu2020-17576, 2020.

The peatlands of the Cuvette Centrale depression in the Congo Basin store between 6.3 and 46.8 petagrams of carbon. To improve our understanding of the genesis, development and functioning of these peatlands, we need to know if their surface is domed. Past work using satellite-based instruments has established that if the peatland surface is domed, it is very shallow, below 2‑3 m over a distance of 26km. We used a laser altimeter mounted on an unmanned airborne vehicle (UAV) to measure peat surface elevation along two transects at the edges of a peatland  to centimetre accuracy, and combined the results with an analysis of local ICESat and ICESat-2 returns. The LiDAR elevations show an upward slope inwards from both edges, and the ICESat and ICESat-2 returns suggest a peak around 1.8 m  above the edges. This matches our expectations of a rainfed peatland and, combined with prior measurements of peat depth, indicates that this peatland formed in a 3 m-deep basin.

How to cite: Davenport, I., McNicol, I., Mitchard, E., Lewis, S., Hawthorne, D., Dargie, G., Bocko, Y., Lawson, I., Baird, A., Page, S., Suspense, I., and Milongo, B.: UAV and Spaceborne LiDAR Gives First Evidence of Peat Domes in the Congo Basin, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9909, https://doi.org/10.5194/egusphere-egu2020-9909, 2020.

Patterned fens (aapa mires) are important part of boreal landscape. Their distribution is controlled by climate and local hydrological conditions. In order to assess the changes and stresses climate change and land use may cause in these ecosystems, we modelled the past and future hydrology of twelve aapa mires in different parts of Finland. The study area extends from the southern to northern boreal zone.

Mire catchments were delineated with the help of a digital elevation model. Wet minerotrophic areas (flarks) in the centers of aapa mires were traced from aerial images with numerical methods. Runoff modelling was done for the period 1962–2099 with a conceptual model ‘CPI snow’ using gridded temperature and precipitation data from historical weather records as well as predicted values based on climate scenarios.

The results clearly indicate changes in hydrological conditions of aapa mires. In particular, timing and volume of spring peak runoff after snowmelt are affected. It is probable that the changes influence aapa mire wetness, vegetation, and eventually survival and distribution. We search for evidence of these changes from remote sensing time series (Landsat) from 1980s to present. Possible implications of changes in northern peatlands include loss of biodiversity and changes in carbon cycle.

How to cite: Sallinen, A., Akanegbu, J., Marttila, H., Kumpula, T., and Tahvanainen, T.: Recent changes in boreal aapa mires indicated by CPIsnow model and Landsat time series, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21161, https://doi.org/10.5194/egusphere-egu2020-21161, 2020.

The biogeographic limit of the peatlands in the central-north Quebec region (53°80’-53°85’N) corresponds to the ecotone between the open boreal forest and the forest-tundra.  At this latitude, peatlands are mainly represented by patterned fens that developed in topographic depressions of the Precambrian Shield. They are characterized by mildly minerotrophic conditions with  surface patterning similar to that observed in western Labrador, central Sweden and the aapa mires of northern Finland.  In eastern Canada,  patterned peatlands have shown  ecohydrologic disequilibrium during the last centuries expressed by a general water table rise with degradation of strings and expansion and coalescence of pools. It has been shown that peatlands in this region present a similar pattern of ecohydrological disequilibrium to those documented in the northeast section of the La Grande River watershed, subarctic Quebec (54°00’N-54°05’N) and this confirms the importance of investigating their ecohydrological vulnerability to natural and anthropogenic pressures in terms of hydrology and carbon balance. A multidisciplinary project was initiated to quantify the hydroclimatic changes that may have influenced the ecohydrologic disequilibrium phenomenon using two peatlands control sites. The results presented here focus on the current water budget of the peatlands and aim at identifying the parameters that influence most significantly peatland hydrology and its connection to the surrounding aquifer. The two peatlands were instrumented with 15 piezometers (in the peat and in the aquifer) where groundwater levels were measured during two growing seasons. Peatland characterization included peat depths, peat hydraulic conductivities (six cores, Modified Cube Method), hydraulic gradients and surface outflow rates. Preliminary results from time series analyses and water budgets show indications of groundwater inflows at each site. If confirmed, these results would comfort the hypothesis that the peatlands are sensitive to hydro-climatic variations with more precipitation inducing higher groundwater levels and thus increased groundwater inflow to the peatlands. Using quantitative paleoclimate reconstructions (pollen, macrofossils and testate amoeba), it has been shown that the two peatlands have registered hydroclimatic periods with potential groundwater input sufficient to induce a shift from bog to fen in these ecosystems. Inversely, a recent shift from fen to bog during  the 20th century suggest that enhanced plant productivity with the lengthening of the growing season duration might influence a decrease of groundwater input in the peatlands The warmer climate shift under way is expected to induce even more of these changes, thus increasing further the large-scale phenomenon as observed in peatlands of northeastern Canada.

How to cite: Garneau, M., Larocque, M., Lambert, C., Robitaille, M., Baird, A. J., and Morris, P. J.: Using current hydrological conditions to better understand holocene ecohydrological dynamics in oligotrophic peatlands of north-central Quebec, Canada, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12278, https://doi.org/10.5194/egusphere-egu2020-12278, 2020.

Peatland ecosystems are complex mosaics and located often in low-lying transitional zones between terrestrial and aquatic ecosystems. Peatlands in its pristine state play a significant role in regulating the hydrological, biogeochemical and ecological functions and act as long-term storage for carbon. However, up to 20% of the global peatland resources have been disturbed for a variety of human land uses (e.g., forestry and agriculture) and lost their natural functions. In this research, we tested the effectiveness and applicability of a physically-based three-dimensional fully integrated surface-subsurface numerical model (HydroGeosphere, HGS) to study hydrological disturbances in peatlands. The model was specifically implemented to assess the impact of artificial drainage and subsequent restoration on the hydrological responses (runoff and water table) of a previously disturbed, now restored (ditches-blocked) peatland catchment (about 11.4 ha) located in Western Finland. The hydrological data included two years before restoration (drained condition) and one year after restoration (ditches-blocked) collected during frost-free periods. The model domain was discretized with seven vertical finite element layers of 146744 nodes and 255206 elements to represent the ditch networks (drained condition) and blocked ditches (restored condition) in the model realistically. The HGS model was run for the two disturbed conditions (drained and restored) using forcing weather data collected in 2016, 2017 and 2018. In all the years, simulated runoff in drained conditions was significantly higher than simulated at restored conditions. The simulated water table level in restored conditions was significantly closer to the ground surface than in drained conditions, which agreed with the observed water table data. The results indicated that three-dimensional models, such as the HGS can be implemented to evaluate the effect of restoration measures on the hydrological response of peatland catchments. Thus, high-resolution physically-based models have the potential to improve our understanding of the complex hydrology of disturbed habitats spatially. Understating the spatial dependence of peatlands to inputs from groundwater and surrounding upland areas could further help us improve restoration measures.

How to cite: Menberu, M., Ronkanen, A.-K., Marttila, H., Haghighi, A. T., and Kløve, B.: Hydrological Responses to Anthropogenic Disturbance in Peatlands: a Numerical Approach, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8897, https://doi.org/10.5194/egusphere-egu2020-8897, 2020.

Hydro-physical properties of peat influence the partitioning of rainfall into infiltration versus runoff, determine water flow and solute transport patterns, and regulate the carbon and nitrogen cycles in peatlands. Although soil hydro-physical properties of peat soils are well documented, little is known about the temporal dynamics of soil properties, especially at a century-scale. A data set of peat subsidence as well as bulk density (BD) increase rate following artificial drainage was assembled from the literature. The collected data cover a time period of up to 215 years of land drainage for different land use types (forest and agriculture). The results show that the subsidence rate and soil BD increase rate generally depend on land drainage duration and land use. The most severe shift in soil pore structure of peat used for forest and agricultural occurs within the first 10 and 40 years of land drainage, respectively. Peatland drainage reduces the number of macropores (>50 μm) but increases ultramicro- and cryptoporosity (<5 μm). In the long term, peat subsidence is responsible for more than 85% of soil water storage loss. In conclusion, the derived functions between subsidence rate as well as BD increase rate and drainage duration provide a new method to estimate hydro-physical properties (pore structure and saturated hydraulic conductivity, specific yield, soil water storage) of peat at a century-scale. The derived hydro-physical parameter values can be used for long-term hydrological modelling (back- and forward), especially if measured hydraulic parameters of peat are not available. However, additional research is required to reduce uncertainty.

How to cite: Liu, H., Rezanezhad, F., and Lennartz, B.: Century-Scale Shifts in Peat Hydro-Physical Properties as Induced by Drainage , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13720, https://doi.org/10.5194/egusphere-egu2020-13720, 2020.

Spatial variability of soil properties is important for hydrological studies. However, little information is available on the spatial variability of hydro-physical properties of peat soils. Three study sites: natural, degraded and extremely degraded peatland were selected for this study. At each site, 72 undisturbed soil cores were collected from 5m by 5m grid cells in an area of 40m by 45m. The saturated hydraulic conductivity (Ks), soil water retention curves, total porosity, macroporosity, bulk density and soil organic matter (OM) content were determined for all sampling locations. The van Genuchten model parameters (θs, α, n) were optimized using the RETC software package. A strong positive correlation between macroporosity and Ks was observed irrespective of the degradation stage of the peat. However, the relationships between macroporosity and Ks differed for the different sites. The soil physical properties (e.g. OM content and bulk density) exhibited different levels of spatial autocorrelation depending on the soil degradation stage. The cross-semivariograms showed a strong or moderate spatial dependency between soil physical properties and van Genuchten model parameters. The more a peat soil is degraded, the more likely it is that soil physical properties are spatially dependent. In conclusion, degradation stage plays an important role and should be considered more often in spatial analysis. The obtained cross-semivariogram may serve as a basis for 2D and 3D hydrological modelling. 

How to cite: Wang, M., Liu, H., and Lennartz, B.: Small-scale Spatial Variability of Hydro-physical Properties of Differently Degraded Peat , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18534, https://doi.org/10.5194/egusphere-egu2020-18534, 2020.

The restoration of damaged UK peatlands is a major conservation concern, and landscape-scale restoration is extensive in areas of upland Britain. Peatland headwater catchments are important areas of hillslope runoff production, and over the last decade there has been increasing focus on how restoration schemes can reduce downstream flood risk through natural flood management (NFM). Stormflow in degraded catchments can be incredibly flashy, as water is quickly evacuated from hillslopes across bare peat surfaces and through erosional gullies, but there is increasing evidence that restoration by revegetation and damming of channels can significantly slow the flow of water.

Recent major peatland wildfires in the UK have focused attention on the effects of wildfire and post-wildfire restoration on the hydrology of peatland catchments, but to date, relatively little is known about the effects of wildfire on peatland flood hydrology. Current understanding is largely drawn from process studies, with evidence suggesting that severely burnt peatlands will have flashier hydrograph responses to rainfall events, with higher peak flows relative to unburnt peatlands. This assumption is based on three key factors which promote rapid overland flow: (i) the development of hydrophobic crusts due to high intensity fires, (ii) the clogging of peat pores by ash, and (iii) removal of vegetation cover reducing surface roughness. Further influences on runoff production could result from changes in water table or post-fire peat shrinkage and cracking.

This paper details stormflow characteristics from nine gullies in an area of peatland affected by the high-severity Saddleworth wildfire which burned over 1000 hectares of UK peatland in June and July 2018. This field area is upstream of the community of Stalybridge, which the Environment Agency had highlighted as a priority community at risk of flooding. We compare this behaviour to catchments that were unaffected by the fire. Preliminary findings suggest that the fire affected gullies produce highly variable stormflow behaviour, with some sites producing discharges similar to bare peat sites, while others are more similar to relatively intact catchments. The planned restoration of this area has great potential to provide NFM benefits.

How to cite: Shuttleworth, E., Evans, M., Allott, T., Kay, M., Johnston, A., Alderson, D., Edokpa, D., Holden, J., Milledge, D., Goudarzi, S., Chandler, D., and Brown, D.: Stormflow behaviour in blanket peat catchments affected by severe wildfire: implications for natural flood management, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19754, https://doi.org/10.5194/egusphere-egu2020-19754, 2020.

Peatlands are globally threatened by the increasing exploitation. Majority of peatlands in Finland are severely degraded by land use and drainage activities. Peatland restoration is an effective way to increase biodiversity, return natural function of peatlands in catchment hydrology and reduce negative impacts of drainage.

Restoration activities recover the wet and open habitats crucial for many valuable species and peatlands ability to store water and nutrients. Restoration activates peat forming processes, and thus reduces greenhouse gas (GHG) emissions and returns peatlands to act as carbon sinks.

Restored sites are monitored to determine whether the restoration has succeeded and to gather the experiences to further develop restoration methods. The traditional restoration monitoring demands intensive field work with high labor costs and special ecological expertise. Evaluation is mainly based on visual assessment at present. In addition, monitoring typically cannot cover the entire restored site.

There is strong need to develop unbiased indicators and new cost-effective methods producing spatially representative high-quality information on restoration success. We will study new technical possibilities for evaluation of peatland restoration success with unmanned aerial systems (UAS).

The latest image processing techniques and their use in mapping and analyzing peatland areas are to be studied. UAS provides prospects not only to ease the demanding restoration field work but also to transform the discrete nature of conventional single data points into a spatial continuum over the whole restored peatland.

How to cite: Ikkala, L., Marttila, H., Ronkanen, A.-K., Ilmonen, J., Similä, M., Haapalehto, T., Rehell, S., Kumpula, T., and Klöve, B.: UAS Imaging Applications to Monitor Restored Peatlands, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8350, https://doi.org/10.5194/egusphere-egu2020-8350, 2020.

Water quality forms an essential abiotic factor underpinning the functioning and status of aquatic ecosystems. Despite dominating uplands across of much of North western Europe, the inter relationship between water draining Atlantic blanket bog ecosystems and aquatic ecological receptors remains poorly defined. In Ireland many blanket bog covered catchments have hosted high status streams which, over the past decade, experienced significant degradation and are now in need of programmes of measures to comply with Water Framework Directive Legislation. Defining restoration goals requires an improved understanding of stream hydrology and the water quality regime draining intact peatlands if realistic targets are to be established. 
In an attempt to address this shortcoming, the EPA study “Quantification of Blanket Bog Ecosystem Services to Water (QUBBES)” aimed to evaluate abiotic conditions supporting aquatic ecosystems in relatively undisturbed blanket peat-covered catchments. Following a survey of 341 the most intact catchments across the island of Ireland, of which all were discovered to display some physical damage from anthropogenic activity, QUBBES researchers selected three sites, considered among the least damaged, to characterise the flow regime and water quality of their draining streams. The sites lie along a climatic gradient, locally containing significant thicknesses of peat (0m to >5m) with similar (peat) groundwater quality, yet are underlain by geochemically distinct inorganic subsoil and bedrock substrates. 
Runoff monitoring over a two-year period revealed flashy flow regimes in all three catchments, while high frequency water quality monitoring showed the streams contained acidic, nutrient-poor acidic waters, comparable to those encountered in bog groundwater, during energetic high flow hydrological events. This contrasted with water quality observed in samples collected during lower (base) flow. Under these conditions water quality in each catchment differed strongly from peak flow, as well as from one catchment to another. Quality in the catchment underlain by limestone bedrock (, overlain by a glacial till containing erratic crystalline rock,) was dominated by alkaline, calcium carbonate rich waters, while relative abundances in water samples collected from a stream draining an area underlain by sandstone and shale, overlain by locally derived till, were more acidic and dominated by silica; samples from the stream draining a catchment underlain by basalt bedrock and basalt-rich till were dominated by calcium and silica-rich alkaline waters. 
Study findings revealed the dominance of peat substrate-derived groundwater inputs to base flow and can help explain the biological variability of upland streams in areas covered by blanket peats, containing similar groundwater. Furthermore, findings suggest that aquatic biological metrics for peat covered catchments should give greater consideration to the significance of substrate composition.    

How to cite: Flynn, R., McVeigh, C., Mackin, F., Cahill, S., and Renou Wilson, F.: Beneath the Blanket: Towards a better understanding of stream ecology in blanket peat covered catchments., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2336, https://doi.org/10.5194/egusphere-egu2020-2336, 2020.

The Netherlands plans to cut greenhouse gas emissions by 1 megaton CO₂-equivalents in 2030 by implementing measures reducing peat decomposition. In order to achieve this, a national research program on peatland pasture greenhouse gas emissions has been set up. In the program, five peatland sites with each two fields, with and without submerged tube drainage systems, are continuously monitored. Here, we present our research with the objective to understand the rate of biochemical peat decomposition by assessing electron acceptor availability from a hydrological perspective. Soil (< 100 cm depth) redox conditions are continuously measured at five depths. Preliminary data on soil electron acceptor availability distribution suggest counterintuitive behavior of the peat soils. We find reducing conditions in the topsoil (0-20 cm) and oxidative conditions in the subsoil (40-80 cm) for the sites without tube drainage. For sites with tube drainage, we find oxidative conditions in the topsoil (0-20 cm) and reducing conditions starting at 60 cm depth at the drain location and at 80 cm depth between the drains. A novel 2D groundwater model is being set up, enabling to capture saturation dynamics, water origin and solute transport in the peat soil. We will present our modelling setup and initial simulation results for water origin and travel paths. These results will indicate how electron acceptors are distributed through the soil, helping to interpret redox measurements in the field at different depths. In a later stage of the research, the effects of redox conditions on microbial soil respiration will be evaluated with greenhouse gas chamber and eddy covariance measurements.

How to cite: Boonman, J., van Huissteden, K., Dolman, H., and van der Velde, Y.: Hydrology, electron acceptor availability and organic matter decomposition in Dutch peatland pastures, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7314, https://doi.org/10.5194/egusphere-egu2020-7314, 2020.

Approximately 70% of drinking water in Scotland is sourced from peat-dominated headwater catchments. Healthy peatlands provide high-quality water which requires minimal processing. However, many of Scotland’s upland peatlands show extensive evidence of gully erosion.  The consequences of peatland erosion include: the release of dissolved organic carbon (DOC) and particulate organic carbon (POC) in water supplies, increased risk of flooding, reduced biodiversity and carbon release into the atmosphere.

The 1992 European Community Habitats Directive led to legislative protection for several UK peatlands, and peatland catchment planning is a requirement of the EU Water Framework Directive. Peatland restoration is an important aspect of Scottish Government’s Climate Change planning, with a target of restoring 250 000 ha (41%) of degraded Scottish peatlands by 2030.  Although there has been an increase in UK peatland restoration projects (and associated funding) relatively few studies have sought to understand and evaluate the effectiveness of restoring the underlying hydrology, including water table depth, runoff, flow patterns and water quality.

Here we propose an experimental design to monitor and record data from restored, unrestored and near-natural peatland micro-catchments, with a view to analysing and integrating the empirical data with that from modelling studies, so as to synthesise new understanding of the relationship between restoration measures and hydrological functioning and assess potential hydrological trajectories.

How to cite: Donaldson-Selby, G., Quinn, N., and Artz, R.: Design of an experimental hydrological network to record and evaluate the differences in hydrological functioning across restored, unrestored and near-natural peatland, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11098, https://doi.org/10.5194/egusphere-egu2020-11098, 2020.

There has been increasing interest in peatlands over the last two decades after their recognition as a primary worldwide carbon store and potential to mitigate climate change. Afforestation is a significant global source of peatland degradation, and concentrated efforts to restore affected peatlands are ongoing. Our study monitored the pore-water quality, with respect to the water table depth (WTD), over 18 months from a raised bog and a blanket bog study site where the first forest-bog restoration work started in 2002. We collected pore-water samples from 4 small, hydrologically disconnected catchments which included intact forestry, a near-natural bog and two restored catchments of differing ages and restoration techniques, at each of the study sites.

The WTD was significantly different between the afforested catchments (deepest) and near-natural bog (shallowest), increasing with time since restoration for the restored catchments at both study sites. In periods of low rainfall, the WTD receded faster at the raised bog site, which may be because of the increased water demand from more mature tree stands. There were significant spatial and temporal variations in pore-water chemistry. However, dissolved organic carbon (DOC) and soluble reactive phosphate (PO₄-P) concentrations were significantly higher than the near-natural bog (difference in means of 30.37 mg L^-1 and 412 µg L^-1, respectively), 5-6 years after restoration. DOC and PO₄-P concentrations reduced with time since restoration, and, at the blanket bog site, there was no significant difference between the near-natural bog and a catchment that had been restored 17 years earlier. Principal component analysis (PCA) showed that DOC, PO₄-P and nitrite (NO₂-N) concentrations are controlled by similar processes and primarily a component of the restoration work; dissolved ammonium (NH₄-N), water table depth and electrical conductivity were more closely associated with afforestation. Higher NH₄-N concentrations within the forest pore-water are likely because of increased mineralisation rates within the peat after a lowering of the WTD through drainage and the water demands from the trees; increased electrical conductivity is likely connected to atmospheric scavenging from forest canopies.

The lowland raised bog site had significantly higher mean DOC concentrations which we hypothesise could be a result of increased plant production or the hydrological differences between lowland raised bog and blanket bogs. The humic fractions of the DOC, measured by the E4:E6 ratio of absorption, were significantly higher in the restored sites of the raised bog and negatively correlated with the depth to the water below the surface. We found significant differences between the afforested microforms (furrows, original surface and ploughed ridges) for many of the pore-water variables measured, and we believe newly developed ground smoothing techniques could help restore the natural balance. Dominant vegetation cover was also a significant factor, and other methods such as plug planting of bog species could be beneficial.

How to cite: Howson, T., Chapman, P., Holden, J., Shah, N., and Anderson, R.: Afforestation and subsequent restoration of raised and blanket bogs: impacts on water table depth and pore-water quality, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20961, https://doi.org/10.5194/egusphere-egu2020-20961, 2020.

Globally, peatlands experience water storage fluctuations. Seasonality was once the sole contributor of this natural water table variation, however, for many years, freshwater drainage of peatlands for agriculture, afforestation, and energy production has been prevalent. With constant changes in storage, there exists a measurable connection between subsurface water levels and solute transport in the deep layers of peatland material. Traditionally, water level modelling has benefitted environmental protection schemes with the identification of critically important areas and by implementing relevant hydraulic structures for optimal protection. Restoration and rehabilitation efforts occurring in the last several decades have occasionally highlighted results of miscalculation, whereby a peatland’s capacity to alleviate water flux effects was overestimated in degraded regions. Once a peat layer becomes dry and aerated, it decomposes, releasing nitrogen and other nutrients into the environment. Conversely, if a peatland is inundated beyond its storage capacity, aggregates of peat and vegetation become suspended within the excess water, signifying the potential for an increased methane flux.

In spite of an ideal water level, one that satisfies a degraded condition while preventing excess flooding, research must continue to expand upon land use and management activities and how they affect hydrology and water quality parameters across a given peatland. To quantify geochemical and hydrological properties given the scale of highly variable peat parameters, many studies have relied on single point data to represent peatlands. Since water chemistry has a strong control on geophysics in peatland environments, a remote sensing technique was used in this study to qualitatively describe the surface of a cutaway peatland. Qualitative analysis of the study site describes soil moisture and peat depth through a geophysical interpretation and an ability to detect gamma radiation.

Remote sensing data, acquired by the Geological Survey Ireland, was used to capture radiometric variation at the study site. The airborne survey data was used to identify suitable locations on the study site in which to collect representative soil cores, which were then brought to the laboratory for analysis. The results from laboratory-based hydrological testing of these cores will be used to quantify the impacts of various water management regimes on site. By combining geophysical analysis with laboratory measurements of soil and water chemistry, there is an opportunity for improving upon the development of suitable mitigation measures.

How to cite: Monteverde, S., Healy, M., and Callery, O.: Developing land use strategies in landscapes with changing priority, the case of peatland management, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22648, https://doi.org/10.5194/egusphere-egu2020-22648, 2020.