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Triple oxygen and hydrogen isotopes of gypsum hydration water for quantitative paleo-humidity reconstruction

Accepted version
Peer-reviewed

Type

Article

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Authors

Bauska, T 
Herwartz, D 
Surma, J 

Abstract

© 2017 Elsevier B.V. Atmospheric relative humidity is an important parameter affecting vegetation yet paleo-humidity proxies are scarce and difficult to calibrate. Here we use triple oxygen (δ17O and δ18O) and hydrogen (δD) isotopes of structurally-bound gypsum hydration water (GHW) extracted from lacustrine gypsum to quantify past changes in atmospheric relative humidity. An evaporation isotope-mass-balance model is used together with Monte Carlo simulations to determine the range of climatological conditions that simultaneously satisfy the stable isotope results of GHW, and with statistically robust estimates of uncertainty. We apply this method to reconstruct the isotopic composition of paleo-waters of Lake Estanya (NE Spain) and changes in normalized atmospheric relative humidity (RHn) over the last glacial termination and Holocene (from ∼15 to 0.6 cal. kyrs BP). The isotopic record indicates the driest conditions occurred during the Younger Dryas (YD; ∼12–13 cal. kyrs BP). We estimate a RHnof ∼40–45% during the YD, which is ∼30–35% lower than today. Because of the southward displacement of the Polar Front to ∼42°N, it was both windier and drier during the YD than the Bølling–Allerød period and Holocene. Mean atmospheric moisture gradually increased from the Preboreal to Early Holocene (∼11 to 8 cal. kyrs BP, 50–60%), reaching 70–75% RHnfrom ∼7.5 cal. kyrs BP until present-day. We demonstrate that combining hydrogen and triple oxygen isotopes in GHW provides a powerful tool for quantitative estimates of past changes in relative humidity.

Description

Keywords

triple oxygen isotopes, gypsum hydration water, relative humidity, lake sediments, Younger Dryas, Late Glacial-Holocene transition

Journal Title

Earth and Planetary Science Letters

Conference Name

Journal ISSN

0012-821X
1385-013X

Volume Title

481

Publisher

Elsevier BV
Sponsorship
European Research Council (339694)
Natural Environment Research Council (NE/I016716/1)