Filling and drainage of a subglacial lake beneath the Flade Isblink ice cap, northeast Greenland

The generation, transport, storage and drainage of meltwater beneath the ice sheet play important roles in the Greenland ice sheet (GrIS) system. Active subglacial lakes, common features in Antarctica, have recently been detected beneath GrIS and may impact ice sheet hydrology. Despite their potential importance, few repeat subglacial lake filling and drainage events have been identified under Greenland Ice Sheet. Here we examine the surface elevation change of a collapse basin at the Flade Isblink ice cap, northeast Greenland, which formed due to sudden subglacial lake drainage in 2011. We estimate the subglacial lake volume evolution using multi-temporal ArcticDEM data and ICESat-2 altimetry data acquired between 2012 and 2021. Our long-term observations show that the subglacial lake was continuously filled by surface meltwater, with basin surface rising by up to 55 m during 2012–2021 and we estimate 138.2 × 106 m3 of meltwater was transported into the subglacial lake between 2012 and 2017. A second rapid drainage event occurred in late August 2019, which induced an abrupt ice dynamic response. Comparison between the two drainage events shows that the 2019 drainage released much less water than the 2011 event. We conclude that multiple factors, e.g., the volume of water stored in the subglacial lake and bedrock relief, regulate the episodic filling and drainage of the lake. By comparing the surface meltwater production and the subglacial lake volume change, we find only ~64 % of the surface meltwater successfully descended to the bed, suggesting potential processes such as meltwater refreezing and firn aquifer storage, need to be further quantified.

Research and application of parameter estimation method in hydrological model based on dual ensemble Kalman filter

Although field measurements and using long hydrological datasets provide a reliable method for parameters' calibration, changes in the underlying basin surface and lack of hydrometeorological data may affect parameter accuracy in streamflow simulation. The ensemble Kalman filter (EnKF) can be used as a real-time parameter correction method to solve this problem. In this study, five representative Xin'anjiang model parameters are selected to study the effects of the initial parameter ensemble distribution and the specific function form of the parameter on EnKF parameter estimation process for both single and multiple parameters. Results indicate: (1) the method of parameter calibration to determine the initial distribution mean can improve the assimilation efficiency; (2) there is mutual interference among the parameters during multiple parameters' estimation which invalidates some conclusions of single-parameter estimation. We applied and evaluated the EnKF method in Jinjiang River Basin, China. Compared to traditional approaches, our method showed a better performance in both basins with long hydrometeorological dataset (an increase of Kling–Gupta efficiency (KGE) from 0.810 to 0.887 and a decrease of bias from −1.08% to −0.74%); and in basins with a lack of hydrometeorological data (an increase of KGE from 0.536 to 0.849 and a decrease of bias from −15.55% to −11.42%).

Soil Denitrification, the Missing Piece in the Puzzle of Nitrogen Budget in Lowland Agricultural Basins

Denitrification is a key process buffering the environmental impacts of agricultural nitrate loads but, at present, remains the least understood and poorly quantified sink in nitrogen budgets at the watershed scale. The present work deals with a comprehensive and detailed analysis of nitrogen sources and sinks in the Burana–Volano–Navigabile basin, the southernmost portion of the Po River valley (Northern Italy), an intensively cultivated (> 85% of basin surface) low-lying landscape. Agricultural census data, extensive monitoring of surface–groundwater interactions, and laboratory experiments targeting N fluxes and pools were combined to provide reliable estimates of soil denitrification at the basin scale. In the agricultural soils of the basin, nitrogen inputs exceeded outputs by nearly 40% (~ 80 kg N ha−1 year−1), but this condition of potential N excess did not translate into widespread nitrate pollution. The general scarcity of inorganic nitrogen species in groundwater and soils indicated limited leakage and storage. Multiple pieces of evidence supported that soil denitrification was the process that needed to be introduced in the budget to explain the fate of the missing nitrogen. Denitrification was likely boosted in the soils of the studied basin, prone to waterlogged conditions and consequently oxygen-limited, owing to peculiar features such as fine texture, low hydraulic conductivity, and shallow water table. The present study highlighted the substantial contribution of soil denitrification to balancing nitrogen inputs and outputs in agricultural lowland basins, a paramount ecosystem function preventing eutrophication phenomena.

Geographical Information System Approach to Delineate the Watershed’s Morphometric Parameters for Sustainable Hydrological Modeling of Barind Region, Bangladesh

Water is an important resource of the earth’s surface and it is integral for all on this planet. The availability or the scarcity of water depends on the watershed characterizes that consider the basic, linear, and shape parameters of any waterbody. The objective of the study was to delineate 14 morphometric parameters in the Barind region (Dinajpur district, Bangladesh) for sustainable hydrological modeling. An ASTER-DEM of 30-meter resolution data, geographical information system (GIS), and Remote sensing technique were used for extracting drainage components of interest region. The whole study region was covered by the flow of the Purnovoba river, Jamuna river, Atrai river (part-1 and part-2). Research results found that the Purnovoba river had a high bifurcation ratio (0.9982) that defined hydrologically more disturbed than the other three watershed areas and it had a high stream frequency (0.8332) that denoted rocky having low infiltration capacity. Jamuna river had a low drainage density (0.7322) that defined more vegetation having higher permeability. Besides, the Jamuna river had the lowest no. of stream order that was insignificant in the steady runoff process and less prone to cause a flash flood. The research predicted that the availability of groundwater might decrease to Jamuna river in the future as it had the lowest basin area (217.42 sqr. km ) and perimeter (114.90 km) and the basin surface slope would become gentle to Atrai river part-1 for the lowest length of overland flow (0.6072). Purnovoba river experienced the lowest form factor (0.2351) which indicated the most possibility for erosion. The elongated ratio of all basins was greater than 0.5 which considered all the shapes were more elongated. These findings will help for further modeling of an integrated watershed for sustainable hydrological models in the Barind region.

Evidence for high-elevation salar recharge and interbasin groundwater flow in the Western Cordillera of the Peruvian Andes

Improving our understanding of hydrogeological processes on the western flank of the central Andes is critical to communities living in this arid region. Groundwater emerging as springs at low elevations provides water for drinking, agriculture, and baseflow. Some springs also have recreation or religious significance. However, the high elevation sources of recharge and specific groundwater flowpaths that support these springs and convey groundwater to lower elevations in southern Peru remain poorly quantified in this geologically complex environment. The objectives of this study were to identify recharge zones and groundwater flowpaths supporting natural springs east of the city of Arequipa in the volcanic mountain terrain, particularly, the potential for recharge within the high-elevation closed-basin Lagunas Salinas salar. We used geochemical and isotopic tracers in springs, surface waters (rivers and lakes), and precipitation (rain and snow) sampled from March 2019 through February 2020. We obtained monthly samples from six springs, bimonthly samples from four rivers, and various samples from high-elevation springs during the dry season. We analyzed stable water isotopes (δ18O and δ2H) and general chemistry of springs, rivers, local rainfall, and snow from Pichu Pichu volcano. The monthly isotopic composition of spring water was invariable over time, suggesting that the springs receive a stable source of groundwater recharge and are not supported by relatively short groundwater flowpaths. The chemistry of springs in the low- and mid-elevations (2500 to 2900 masl) point towards a mix of recharge from the salar (4300 masl) and mountain-block recharge (MBR) in or above a queñuales forest ecosystem at ~4000 masl on the adjacent Pichu Pichu volcano. Springs at higher elevation closer to the salar and in a region with a high degree of faulting had higher chloride concentrations indicating higher proportions of interbasin groundwater flow from the salar. We conclude that while the salar is a closed basin, surface water from the salar recharges through the lacustrine sediments, mixes with mountain-block groundwater, and is incorporated into the regional groundwater flow system. Groundwater flow in the mountain block and the subsequent interbasin groundwater flow is accommodated through extensive faulting and fracturing. Our findings provide valuable information on the flowpaths and zones of recharge that support low-elevation springs in this arid region. In this study, high-elevation forests and a closed-basin salar are important sources of recharge. These features should be carefully managed to prevent impacts to the down-valley springs and streams.

Dirty sea ice drives higher Mn concentrations in the Canada Basin

<p>The rapidly changing conditions of the Arctic sea ice system have cascading impacts on the biogeochemical cycles of the ocean. Sea ice transports sediments, nutrients, trace metals, pollutants, and gases from the extensive continental shelves into the more isolated central basins. However, it is difficult to assess the net contribution of this supply mechanism on nutrients in the surface ocean. In this study, we used Manganese (Mn), a micronutrient and tracer which can integrate source fluctuations in space and time, to understand the net impact of the long range transport of sea ice for Mn.</p><p>We developed a three-dimensional dissolved Mn model within a subdomain of the 1/12 degree Arctic and Northern Hemispheric Atlantic (ANHA12) configuration of NEMO centred on the Canadian Arctic Archipelago, and evaluated this model with in situ observations from the 2015 Canadian GEOTRACES cruises. The Mn model incorporates parameterizations for the contributions from river discharge, sediment resuspension, atmospheric deposition of aerosols directly to the ocean and via melt from sea ice, release of sediment from sea ice, and reversible scavenging, while the NEMO-TOP engine takes care of the advection and diffusion of the tracers. </p><p>Simulations with this model from 2002 to 2019 indicate that the majority of external Mn contributed annually to the Canada Basin surface is released by sediment from sea ice, much of which originates from the Siberian shelves. Reduced sea ice longevity in the Siberian shelf regions has been postulated to result in the disruption of the long range transport of sea ice by the transpolar drift. This reduced sea ice supply has the potential to decrease the Canada Basin Mn surface maximum and downstream Mn supply, with implications for other nutrients (such as Fe) contained in ice-rafted sediments as well. These results demonstrate some of the many changes to the biogeochemical supply mechanisms expected in the near-future in the Arctic Ocean and the subpolar seas.</p>

Former humid phases in the southwestern Arabian peninsula: climatic and environmental implications of the tufa record over the last 250 ka from the Harrat Al Birk, Saudi Arabia.

<p>Little is known about the tufa deposits within the volcanic Harrats of western Saudi Arabia. This research aims to characterise the fossil tufa system and examine its utility as a palaeoenvironmental archive. This requires us to understand the conditions under which the tufa was deposited. In particular, to ascertain whether they are cool, freshwater tufa, or geothermal travertine. In this presentation we show the extent of the tufa within the basin, describe the stratigraphy and settings, as well as their composition and petrology, alongside U-Th chronological control for a selection of suitable subsamples</p><p>The samples are composed of low-Mg calcium-carbonate<strong> </strong>and their <sup>87</sup>Sr/<sup>86</sup>Sr composition shows there has been water-rock interaction with the mafic metavolcanic Neoproterzoic bedrock as well as metamorphosed marine carbonates from the Arabian Escarpment at the head of the Wadi Dabsa catchment. Their δ<sup>13</sup>C composition (-6.3 to -12.9 ‰) is indicative of a meteoric water and soil signature, rather than a geothermal source.</p><p>The tufa deposits are widespread within the Wadi Dabsa Basin, with at least three phases of deposition, recorded at the basin surface, within incised wadi channels and in a downstream fan region. In some locations, the size of tufa-cemented fluvial bedload represents very high magnitude events, whilst the lacustrine to paludal facies indicate more quiescent phases of increased moisture availability. The U-Th dating indicates that the basin was wet during interglacial stages (Marine Oxygen Isotope Stags [MIS] 7 and 5) with some indication, given the error ranges on dates from multiple-subsamples, that deposition occurred primarily during interstadials (e.g. MIS 5e, 5c and 5a). The MIS 7 age is from a vug-fill tufa deposits within an extensive tufa cascade, which indicates the cascade itself pre-dates MIS 7.</p><p>The major concentration of artefacts (> 3000) in this basin make it one of the richest Palaeolithic assemblages so far recorded in southwest Saudi Arabia (Foulds et al., 2015; Inglis et al., 2019). This site is ~ 6 km from the current coastline, which is inland from the MIS 5e shorelines in this region (Inglis, pers comm), and these sites with freshwater mean it is important to continue to consider coastal sites as corridors with habitable landscapes for hominins.</p><p><strong>References</strong></p><p>Foulds, F., A. Shuttleworth, A. Sinclair, A. M. Alsharekh, S. Al Ghamdi, R. H. Inglis, G.N. Bailey (2017) A large handaxe from Wadi Dabsa and early hominin adaptations within the Arabian Peninsula. Antiquity. 91:1421–1434.</p><p>Inglis, R. H., Fanning, P. C., Stone, A., Barford, D. N., Sinclair, A., Hsing-Chung, C., Alsharekh, A., Bailey, G. (2019). Palaeolithic artefact deposits at Wadi Dabsa, Saudi Arabia: A multi-scalar geoarchaeological approach to building an interpretive framework.  Geoarchaeology 34(3), 272-294.   </p>

DYNAMICS OF TURBIDITY OF RIVER WATER ON THE LEFT-BANK TRIBUTARIES OF THE DNIEPER (ON THE EXAMPLE OF THE SUMY REGION)

The article is devoted to the study of sediment runoff, especially one of the characteristics that reflects erosion processes in the catchment area, water turbidity using the example of the rivers of the Sumy region. The main purpose of the article is the spatial and temporal analysis of the turbidity indicators of the rivers of the Sumy region (left-bank tributaries of the Dnieper). The article highlights information on the sediment runoff of the rivers in the region for the entire period of observations, describes modern own studies of the turbidity of river water and establishes the features of the formation of sediment runoff in the rivers of the region. It was found that the indicators of turbidity of river water grow in the direction from north to south of the study area, in the zone of mixed forests are minimal, and in the forest-steppe – maximum; high values of the average turbidity index characteristic of small rivers in the region, аmong the average rivers, the maximum values were recorded for the Sula and Vorskla rivers; during floods, turbidity values are maximum, and during low water periods, they are minimal; there is a tendency to an increase in the indicators of maximum and average turbidity of river water. Particular attention is paid to the influence of river regulation on turbidity indicators. It was found that the deceleration of water exchange is facilitated by the accumulation of sediments in the channel above the dam (high indicators of the thickness of the silt layer), and also below the dam (the creation of a channel island, probably due to the uneven throughput of the dam’s gate valves, which creates a different flow rate from the right and left banks). Decreased flow velocity, increased water turbidity and, as a consequence, siltation, deterioration of river water quality (appearance of swamp odor, decrease in transparency, color change) leads to changes in the species composition of aquatic organisms, extinction of river species and the appearance of atypical river species, overgrowth. In their conclusions, the authors argue that sediment runoff is formed mainly due to washout from the surface of the catchment area, high turbidity indicators in rivers whose basin is more prone to erosion, where the indicators of plowing of the basin surface are maximum, water protection zones and coastal protective belts are destroyed, but when studying the turbidity of river water it is necessary take into account additional factors.

Numerical simulation of surface flow through the lattice boltzmann method using sub-basin junction

The watershed surface runoff was investigated through the one-dimensional numerical simulation using the Lattice Boltzmann Method (LBM). A computational model was developed where the watershed is represented by the junction of nine sub-basins. For this, two equilibrium distribution functions were established through the Chapman-Enskog Expansion on a D1Q5 lattice, one suitable for flow on the basin surface and another for the main channel, obtaining the water depth on the basin surface and the channels cross-sectional area. In addition, the boundary condition was established in the flow passage from one sub-basin to another, taking into account the mass conservation and, in order to obtain a simulation closer to reality, it was considered an initial river flow (baseflow) of each channel stretch. The numerical results obtained by the LBM were compared with data measured in field.