Hydroclimatic Controls on Salt Fluxes and Halite Deposition in the Dead Sea and the Shaping of "Salt Giants". Issue 22 (16th November 2020)

• Record Type: Journal Article
• Authors: Sirota, Ido; Ouillon, Raphael; Mor, Ziv; Meiburg, Eckart; Enzel, Yehouda; Arnon, Ali; Lensky, Nadav G.
• Is Part Of: Geophysical research letters. Volume 47:Issue 22(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-11-16
• Subjects: halite -- Dead Sea -- double diffusion -- thermohaline staircases -- salt giants -- hydroclimate; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2020GL090836
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: As the only deep hypersaline, halite‐precipitating lake on Earth today, the Dead Sea is the single modern analog for investigating the mechanisms by which large‐scale and thick salt deposits, known as "salt giants", have accreted in the geological record. We directly measure the hydroclimatic forcing and the physical limnologic processes leading to halite sedimentation, the vertical thermohaline structure, and salt fluxes in the Dead Sea. We demonstrate that changes in these forcing lead to strong seasonal and regional variations in the stratification stability ratio, triggering corresponding spatiotemporal variations in thermohaline staircase formation and diapycnal salt flux, and finally control the thickness of the halite layer deposited. The observed staircase formation is consistent with the mean‐field γ instability, causing layering in double‐diffusive convection. We show that double diffusion and thermohaline staircase formation drive the spatial variability of halite deposition in hypersaline water bodies, underlying and shaping "salt giants" basin architecture. Plain Language Summary: Kilometers‐thick halite sequences in the geological record represent some of the extreme environmental events during Earth's history. The present‐day Dead Sea serves as an analog for halite deposition and the unique limnology/oceanography of those past hypersaline environments. We observe differential downward salt flux in the lake and halite deposition at the deep lakefloor, corresponding to theoretical requirements of water column stability and the evolution of a step‐like thermohaline structure of the water column. These variations are spatiotemporally controlled by regional hydroclimatology, as the salt flux and halite deposition enhanced during the dry summer and farther from the freshwater inflows into the lake, along an increasing salinity gradient. Our findings explain thick halite accretion in global basin depocenters. Key Points: We resolve the mechanisms driving thick salt layers accretion in deep saline waterbodies by direct field measurements in the Dead Sea Hydroclimatic variations impact stratification stability, thermohaline staircases, double diffusion salt fluxes, and halite deposition Regional and seasonal drying trends dictate stronger salt flux in the drier and deeper zones and explain the architecture of "salt giants"