Natural versus human control on subsurface salt dissolution and development of thousands of sinkholes along the Dead Sea coast

Abstract

One of the most hazardous results of the human‐induced Dead Sea (DS) shrinkage is the formation of more than 6000 sinkholes over the last 25 years. The DS shrinkage caused eastward retreat of underground brine replaced by fresh groundwater, which in turn dissolved a subsurface salt layer, to generate cavities and collapse sinkholes. The areal growth rate of sinkhole clusters is considered the most pertinent proxy for sinkholes development. Analysis of light detection and ranging, digital elevation models, and interferometric synthetic aperture radar allows translation of the areal growth rate to a salt dissolution rate of the salt layer, revealing two peaks in the history of the salt dissolution rate. These peaks cannot be attributed to the decline of the DS level. Instead, we show that they are related to long‐term variations of precipitation in the groundwater source region, the Judea Mountains, and the delayed response of the aquifer system between the mountains and the DS rift. This response is documented by groundwater levels and salinity variations. We thus conclude that while the DS level decline is the major trigger for sinkholes formation, the rainfall variations more than 30 km to the west dominate their evolution rate. The influence of increasing rainfall in the Judea Mountains reaches the DS at a typical time lag of 4 years, and the resulting increase in the salt dissolution rate lags by a total time of 5–6 years.

Answers to interactive comments Rev. 1

“…(2) the alluvium sinkhole shape is remarkably similar to the late-stage (evolved) modelled sinkholes both laterally and vertically; (3) the salt sinkhole is comparable to the respective simulation result for an early-stage salt sinkhole. These findings are essentially confirmed by knowledge about the rather recent development of the sinkholes selected in the mud and salt flats and the older, more evolved sinkholes in the alluvial fan of Ghor Al-Haditha (Al-Halbouni et al, 2017). Our models, which are based on realistic material parameter estimation, hence reproduce the topographic features of the sinkholes successfully in the field site.…”

Reply to Interactive Comment 1

“…The width of the array also increases slightly from ∼ 110 m in the shallow part to ∼ 150 m in the deep part. This progressive initiation of newer and deeper sets of cavities represents a vertical evolution of a dissolution front during base-level fall, the main hydrogeological boundary condition at the shrinking Dead Sea (Abelson et al, 2017;Bartov, 2002;Watson et al, 2019). The bonded particle assembly's bulk material properties, which emerge from the properties defined on the particle scale, were constrained by simulated geomechanical tests on material samples (Schöpfer et al, 2007;.…”

“…We analysed data from repeated photogrammetry of 3 consecutive years of the sinkhole area of Ghor Al-Haditha, at the eastern side of the Dead Sea ( Fig. 1a and Al-Halbouni et al, 2017). The datasets have been used to derive DSM difference maps between the consecutive years via GIS software.…”

“…An opportunity to shed new light on such relationships has arisen in an evaporite karst setting at the margins of the shrinking Dead Sea (Yechieli et al, 2016). There, clusters of tens to over a hundred sinkholes (1-75 m diameter) that are surrounded by larger-scale (100-800 m diameter) depressions have rapidly developed over the last 40 years (Al-Halbouni et al, 2017;Atzori et al, 2015;Filin et al, 2011). In particular, recent studies by (Al-Halbouni et al, 2017;Watson et al, 2019) involving field work, remote sensing and photogrammetric surveying enabled the detailed documentation of spatiotemporal relationships between sinkhole and depression development at Ghor Al-Haditha, on the eastern shore of the Dead Sea (Fig.…”

InSAR Measurements and Viscoelastic Modeling of Sinkhole Precursory Subsidence: Implications for Sinkhole Formation, Early Warning, and Sediment Properties

“…Sinkhole formation in the DS began in the early 1980s (Arkin & Gilat, ) and accelerated significantly after 2000. With an annual formation rate of ~400 new sinkholes, more than 6,000 sinkholes were identified as of mid‐2017 (M. Abelson, personal communication, ). The DS sinkholes are formed by groundwater dissolution of a 5–20 m thick, 5–65 m deep, ~10,000‐year‐old salt layer which lies at the base of the Quaternary Ze'elim Formation (Yechieli et al, ).…”