Radiokrypton unveils dual moisture sources of a deep desert aquifer

Yokochi, Reika; Ram, Roi; Zappala, J. C.; Jiang, Wei; Adar, Eilon; Bernier, Ryan; Burg, Avihu; Dayan, Uri; Lu, Zheng‐Tian; Mueller, Peter; Purtschert, Roland; Yechieli, Yoseph

doi:10.1073/pnas.1904260116

Cited by 39 publications

(23 citation statements)

References 47 publications

(52 reference statements)

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“…(). Some hints for an increase in TP frequencies over the study area, which could have triggered significant hydro‐geomorphic effect do exist (Armon et al, ; Yokochi et al, ), however, the question of past frequencies of geomorphic‐efficient events in the region is still open.…”

Section: Discussionmentioning

confidence: 99%

Linking frequency of rainstorms, runoff generation and sediment transport across hyperarid talus‐pediment slopes

Shmilovitz

Morin

Rinat

et al. 2020

Earth Surf Processes Landf

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Documenting hillslope response to hydroclimatic forcing is crucial to our understanding of landscape evolution. The evolution of talus‐pediment sequences (talus flatirons) in arid areas was often linked to climatic cycles, although the physical processes that may account for such a link remain obscure. Our approach is to integrate field measurements, remote sensing of rainfall and modeling to link between storm frequency, runoff, erosion and sediment transport. We present a quantitative hydrometeorological analysis of rainstorms, their geomorphic impact and their potential role in the evolution of hyperarid talus‐pediment slopes in the Negev desert, Israel. Rainstorm properties were defined based on intensity–duration–frequency curves and using a rainfall simulator, artificial rainstorms were executed in the field. Then, the obtained measured experimental results were up‐scaled to the entire slope length using a fully distributed hydrological model. In addition, natural storms and their hydro‐geomorphic impacts were monitored using X‐band radar and time‐lapse cameras. These integrated analyses constrain the rainfall threshold for local runoff generation at rain intensity of 14 to 22 mm h‐1 for a duration of five minutes and provide a high‐resolution characterization of small‐scale runoff‐generating rain cells. The current frequency of such runoff‐producing rainstorms is ~1–3 per year. However, extending this local value into the full extent of hillslope runoff indicates that it occurs only under rainstorms with ≥ 100‐years return interval, or 1% annual exceedance probability. Sheetwash efficiency rises with downslope distance; beyond a threshold distance of ~100 m, runoff during rainstorms with such annual exceedance probability are capable of transporting surface clasts. The erosion efficiency of these discrete rare events highlights their potential importance in shaping the landscape of arid regions. Our results support the hypothesis that a shift in the properties and frequency of extreme events can trigger significant geomorphic transitions in areas that remained hyperarid during the entire Quaternary. © 2020 John Wiley & Sons, Ltd.

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Section: Discussionmentioning

confidence: 99%

Linking frequency of rainstorms, runoff generation and sediment transport across hyperarid talus‐pediment slopes

Shmilovitz

Morin

Rinat

et al. 2020

Earth Surf Processes Landf

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“…Water locked deep in Earth's major ice sheets or stored in its aquifers is water that fell from the atmosphere as rain and snow over time and as long ago as hundreds of thousands to millions of years ago. Radioactive isotopes analysed from groundwater samples have been used to characterize the age of Earth's ground water as illustrated in the studies of Yokochi et al [8] and Gleeson et al [9]. Yokochi et al [8] used radiokrypton 81 Kr, a radioactive cosmogenic isotope, to determine the paleo-climatic sources of recharge of the subsurface water in the Nubian Sandstone Aquifer in the Negev Desert, Israel.…”

Section: Introductionmentioning

confidence: 99%

“…Radioactive isotopes analysed from groundwater samples have been used to characterize the age of Earth's ground water as illustrated in the studies of Yokochi et al [8] and Gleeson et al [9]. Yokochi et al [8] used radiokrypton 81 Kr, a radioactive cosmogenic isotope, to determine the paleo-climatic sources of recharge of the subsurface water in the Nubian Sandstone Aquifer in the Negev Desert, Israel. They could identify two distinct moisture sources of the recharge: one less than 38 ka from the Mediterranean and the other approximately 361 ka from the tropical Atlantic.…”

Section: Introductionmentioning

confidence: 99%

Earth's water reservoirs in a changing climate

et al. 2020

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Progress towards achieving a quantitative understanding of the exchanges of water between Earth's main water reservoirs is reviewed with emphasis on advances accrued from the latest advances in Earth Observation from space. These exchanges of water between the reservoirs are a result of processes that are at the core of important physical Earth-system feedbacks, which fundamentally control the response of Earth's climate to the greenhouse gas forcing it is now experiencing, and are therefore vital to understanding the future evolution of Earth's climate. The changing nature of global mean sea level (GMSL) is the context for discussion of these exchanges. Different sources of satellite observations that are used to quantify ice mass loss and water storage over continents, how water can be tracked to its source using water isotope information and how the waters in different reservoirs influence the fluxes of water between reservoirs are described. The profound influence of Earth's hydrological cycle, including human influences on it, on the rate of GMSL rise is emphasized. The many intricate ways water cycle processes influence water exchanges between reservoirs and thus sea-level rise, including disproportionate influences by the tiniest water reservoirs, are emphasized.

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“…This is demonstrated by radiokrypton dating of NAS groundwater in Sinai and the Negev Desert, which distinguished two moisture sources of recharge under cooler conditions compared to the present: a recent one with elevated d-excess from the Mediterranean cyclones during the last 38 ky and an older source, 361 ± 30 ky ago, with low d-excess from the tropical Atlantic (Yokochi et al, 2019;Table S7). The recent high d-excess groundwater component was locally recharged from the Nubian sandstone outcrops in Sinai and the Negev Desert (Abouelmagd et al, 2014;Yokochi et al, 2019) S8) showed that the mean values of dexcess for Rafah and Al-Arish stations were 18‰ and 16.9‰, respectively compared to a lower mean value of Cairo station which was 7.3‰.…”

Section: Oxygen and Hydrogen Isotopic Composition (δ 18 O And δD)mentioning

confidence: 93%

Fault zone hydrogeology in arid environments: The origin of cold springs in the Wadi Araba Basin, Egypt

Khalil

Hamer

Pichler

et al. 2021

Hydrological Processes

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The role of faults in controlling groundwater flow in the Sahara and most of the hyper-arid deserts is poorly understood due to scarcity of hydrological data. The Wadi Araba Basin (WAB), in the Eastern Sahara, is highly affected by folds and faults associated with Senonian tectonics and Paleogene rifting. Using the WAB as a test site, satellite imagery, aeromagnetic maps, field observations, isotopic and geochemical data were examined to unravel the structural control on groundwater flow dynamics in the Sahara. Analysis of satellite imagery indicated that springs occur along structurally controlled scarps. Isotopic data suggested that cold springs in the WAB showed a striking similarity with the Sinai Nubian aquifer system (NAS) water and the thermal springs along the Gulf of Suez (e.g., δ 18 O = À8.01‰ to À5.24‰ and δD = À53.09‰ to À31.12‰) demonstrating similar recharge sources. The findings advocated that cold springs in the WAB represent a natural discharge from a previously undefined aquifer in the Eastern Desert of Egypt rather than infiltrated precipitation over the plateaus surrounding the WAB or through hydrologic windows from deep crystalline basement flow. A complex role of the geological structures was inferred including: (1) channelling of the groundwater flow along low-angle faults,(2) compartmentalization of the groundwater flow upslope from high-angle faults, and (3) reduction of the depth to the main aquifer in a breached anticline setting, which resulted in cold spring discharge temperatures (13-22 C). Our findings emphasize on the complex role of faults and folds in controlling groundwater flow, which should be taken into consideration in future examination of aquifer response to climate variability in the Sahara and similar deserts worldwide.

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Radiokrypton unveils dual moisture sources of a deep desert aquifer

Cited by 39 publications

References 47 publications

Linking frequency of rainstorms, runoff generation and sediment transport across hyperarid talus‐pediment slopes

Linking frequency of rainstorms, runoff generation and sediment transport across hyperarid talus‐pediment slopes

Earth's water reservoirs in a changing climate

Fault zone hydrogeology in arid environments: The origin of cold springs in the Wadi Araba Basin, Egypt

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