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- Title
Quantifying amount and distribution of rainfall based on the Dead Sea sediments geochemistry.
- Authors
Kiro, Yael; Goldstein, Steven L; Kushnir, Yochanan; Stein, Mordechai; Lazar, Boaz
- Abstract
The Dead Sea ICDP Deep Drilling Project recovered a high temporal-resolution record ofchanges in the East Mediterranean-Levant hydroclimate over the past 220,000 years, reflectedin the core’s lithology and geochemistry. The greatest changes occur on glacial to interglacialtime-scales, where during glacials lake levels were high and aragonite precipitated, andduring interglacials, lake levels were low and halite precipitated. However, the lithology andgeochemistry of the sediments record much higher frequency variations. Based on aragonite,gypsum and halite abundance along with the XRF (chemical) record, and calibrating theseto the known lake level curve, we have generated a modeled lake level curve andestimates of the fresh water runoff with a time-scale resolution reaching decades. Inaddition to the significant changes in the amount and temporal variability of rainfallbased on the lithology and major element chemistry, radiogenic isotopes (U, Pb, Sr)provide information on the spatial distribution of rainfall, which can be quantified bythe budgets of these elements in the lake. The lithology around the lake varies,including carbonate rocks in the western and northern catchments and sandstone andcrystalline rocks in the southern and eastern catchments, which affects the watersources flowing through each of these lithologies. 234U/238U ratios were foundto be an excellent proxy for these water sources, where water from the east andsouthern catchment have low activity ratio of ∼1.1 and water from the northern andwestern catchment have an activity ratio of ∼1.6. These different water sources reflectthe effects of Mediterranean storms vs. southern climate systems related to thetropics. The U budget of the Dead Sea today (234U/238U∼1.45) is consistent withthe composition of water sources and their fluxes. The fraction and the amount ofsouthern sources contributing to the total runoff over the past 220,000 years can becalculated using the U budget, the 234U/238U ratios through time (from authigenicminerals), and the total modeled runoff. Our results show that during glacials the totalrunoff was 1.2-to-3 times the present-day runoff, while during interglacials it was20-to-100% of the present-day. The fraction of southern runoff varies most of thetime between ∼10% in glacials and ∼20% in interglacials but can reach 50-90%during peak Northern Hemisphere summer insolation periods during interglacials.
- Subjects
GEOCHEMISTRY; UNDERWATER drilling; COMPOSITION of water; FRESH water; CARBONATE rocks; RUNOFF; ENERGY budget (Geophysics)
- Publication
Geophysical Research Abstracts, 2019, Vol 21, p1
- ISSN
1029-7006
- Publication type
Article