Gonéri Le Cozannet

Jeremy Rohmer

Jean-Charles Manceau

Gaël Durand

Catherine Ritz

Angélique Melet

Benoit Meyssignac

David Salas

Aimée B A Mélia

Jochen Slangen

Hinkel

A unified approach to quantify uncertainties in sea level projections

des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

A unified approach to quantify uncertainties in sea level projections

, (1)BRGM, Orleans, France, (2)Institut des Géosciences de l'Environnement, CNRS/Univ. Grenoble Alpes/G-INP/IRD, Grenoble, France, (3)LGGE Laboratoire de Glaciologie et Géophysique de l'Environnement, Saint Martin d'Hères, France, (4)Mercator Ocean, Princeton, France, (5)Observatory Midi-Pyrenees, Toulouse, France, (6)Météo-France Toulouse, Toulouse, France, (7)NIOZ, Yerseke, Netherlands, (8)Global Change Forum, Berlin, Germany, (9)Utrecht University, Utrecht, Netherlands, (10)University of Hamburg, Hamburg, Germany Abstract Text: By 2100, between 0.2 and 4.6% of the global population is expected to be flooded annually. The uncertainties of this statement originate from climate change scenarios, coastal impact models as well as different sea level projections. In the most recent research, uncertainties in sea level projections have been provided in a probabilistic form, in resonance with the common practice in coastal engineering. However, because the physical processes affecting land-ice melting remain still incompletely understood today, different probabilistic projections can be provided. The co-existence of various credible physical mechanisms defines a higher level of uncertainty beyond probabilities, which is referred to as "ambiguity" in the literature. Here, we build on extra-probabilistic theories of uncertainties to provide a unified approach to quantify ambiguity in sea level projections. We show that the knowledge gained regarding ice sheets melting since the AR5 allows to quantify the relationship between ambiguity in sea level projections and greenhouse gas emissions scenarios, both globally and regionally: limiting climate change to RCP 4.5 instead of RCP 8.5 reduces ambiguity by 40% globally, and even 70% for RCP 2.6. Europe and Northern America benefit the most from a policy limiting climate change to RCP 2.6 instead of RCP 4.5. For adaptation planning, this means that mitigation of climate change strongly reduces the risks of high-impact high end scenarios along most of the coasts. Our results provide a baseline to select regional high end scenarios, whose probability is difficult to quantify, but which are associated with high risks of impacts and are therefore particularly relevant for adaptation planning.

Plain-Language Summary: Over the coming century, sea level will continue rising to an amount which remains highly uncertain. This is summarized by the AR5 IPCC report using a likely range between 30cm and 1m depending on future greenhouse gas emissions. Probability, though a powerful tool for uncertainty treatment, remains however a poor descriptor of this situation, which encompasses lack of knowledge and of consensus in the scientific community on numerous physical processes with different kinematics, and particularly its ice melting component. Consequently, a unique probability model can hardly and unambiguously be provided to represent the uncertainties of future sea level rise. In this contribution, we show how this level of uncertainties, which is termed ambiguity in the literature, can be understood, quantified, and communicated with extra-probabilistic theories of uncertainties. Primary Email: gael.durand@univ-grenoble-alpes.fr

Affiliation(s):

Institut des Géosciences de l'Environnement, CNRS/Univ. Grenoble Alpes/G-INP/IRD Grenoble (France)

Fifth Author Catherine Ritz

Primary Email: catherine.ritz@lgge.obs.ujf-grenoble.fr

Affiliation(s):

LGGE Laboratoire de Glaciologie et Géophysique de l 'Environnement Saint Martin d'Hères (France)

  For non-students only: I am interested in receiving information on the AGU mentoring program.

	Paid (agu-fm18-373793-0214-4799-1112-7902)
	First Presenting Author
	Presenting Author
	Goneri Le Cozannet
	Primary Email: G.LeCozannet@brgm.fr
	Phone: ARRAY(0xf428314)
	Affiliation(s):
	BRGM
	Orleans 45060 (France)
	Second Author
	Jeremy Rohmer
	Primary Email: j.rohmer@brgm.fr
	Affiliation(s):
	BRGM
	Orleans 45060 (France)
	Third Author
	Jean-Charles Manceau
	Primary Email: jc.manceau@brgm.fr
	Phone: ARRAY(0xf428314)
	Affiliation(s):
	BRGM
	Orleans 45060 (France)
	Fourth Author
	Gael Durand
	Session Selection:
	Quantifying and Decreasing Uncertainty in Projections of Future Sea Level Change
	Submitter's E-mail Address:
	g.lecozannet@brgm.fr
	Abstract Title:
	A unified approach to quantify uncertainties in sea level projections
	Requested Presentation Type:
	Assigned by Program Committee (oral or Poster)
	Previously Published?:
	No
	AGU On-Demand:
	Yes
	Abstract Payment:

Primary Email: angelique.melet@mercator-ocean.fr

Affiliation(s):

Mercator Ocean Princeton (France)


Elodie Brisset
email: elodie.brisset@gmail.com

Djamali Edouard Morteza

Bard

Borschneck Daniel

Gandouin Emmanuel

Garcia Marta

Stevens Lora

Kazuyo Tachikawa

Á M Djamali

Á E Gandouin

A ` Rea De Prehisto

E Bard

Á D Borschneck

Á M Garcia

Á K Tachikawa

L Stevens

Late Holocene hydrology of Lake Maharlou, southwest Iran, inferred from high-resolution sedimentological and geochemical analyses

Keywords: Paleohydrology, Saline lake, Evaporite, Detrital supply, Drought, Human disturbance

Sedimentological (dry density, micro-facies analysis on thin-slides, X-ray diffraction, layer counting) and elemental analyses (X-ray fluorescence) of a 3.5-m-long sediment core (MAH-B) from saline Lake Maharlou (SW Iran) were used to infer hydrological changes over the last * 3800 years. The sediment consists of thin, alternating beds of evaporites (halite, gypsum), carbonates (calcite, aragonite) and detrital minerals (quartz, muscovite, chlorite). We interpret the data with respect to three main hydrologic conditions: (1) nearly complete desiccation of the lake, marked by frequent halite layers, (2) hypersaline conditions marked by gypsum abundance, (3) wet conditions, characterized by high river-borne terrigenous sediment input with high potassium content. Distinct flood layers indicate fluvial activity. From about 3800-2000 cal year BP, terrigenous sediment supply was high, with peaks at 3700-3650, 3500-3450, and 3400-3250 cal year BP. Evaporative conditions were not common. From ca. 2000 cal year BP to present, detrital minerals are less abundant, and the increase in gypsum abundance suggests drier climate with enhanced evaporation. Frequent desiccation events occurred from 1100 to 700 cal year BP. The late Holocene hydrology of Lake Maharlou corresponds well with records of dune formation and phases of river alluviation in Iran and the Arabian Peninsula, and with regional speleothem records. In addition to the influence of climate change on the lake hydrology, ancient humans modified water drainage in the catchment. Periods of subterranean tunnel (qanats) use correspond to dramatic shrinkage of the water body. We propose that climate changes drove longterm water shortages that were enhanced by anthropogenic activities, leading to more frequent desiccation of the lake during the last millennium.

Introduction

Arid and semi-arid regions, which cover one quarter of the continental Earth surface, are particularly vulnerable to droughts because of the scarcity of water resources. In Iran, especially in the southeast and southwest regions, the severity of drought has increased during the last 30 years (Bari Abarghouei et al. 2011). Climate models predict that Iran's wet regions will receive more rainfall, while its dry regions will be generally drier, continuing this trend of protracted droughts [START_REF] Abbaspour | Assessing the impact of climate change on water resources in Iran[END_REF]. Droughts superimposed on the overall drying have significant economic and environmental consequences. The severe drought in AD 1999-2000 resulted in a 30% loss of productivity in the agricultural sector of Iran compared with previous years [START_REF] Salami | The economic impacts of drought on the economy of Iran: an integration of linear programming and macroeconometric modelling approaches. Participation and Evaluation for Sustainable River Basin Governance[END_REF]) and also badly affected livestock, fisheries, and forestry. The combination of drought, the rising demand for water for irrigation and domestic use and poor water management have critically affected all water resources of the country [START_REF] Motagh | Land subsidence in Iran caused by widespread water reservoir overexploitation[END_REF].

During the last decade, numerous lakes of the semiarid Iranian plateau (Urmia, Hamoun, Parishan, Maharlou) have reached critical water levels. Lake Urmia, one of most emblematic lakes in the Near East because of its large size, lost 70% of its surface area between 2002 and 2014, despite its environmentally protected status [START_REF] Wurtsbaugh | Decline of the world's saline lakes[END_REF]. The disappearance of lakes in several regions of Iran reveals the serious problem of long-term sustainability of surface water resources in the region, but also highlights the depleted state of the ground-water resources. The main cause of the recent drop in lake levels is anthropogenic alteration of the water system [START_REF] Tourian | A spaceborne multisensor approach to monitor the desiccation of Lake Urmia in Iran[END_REF], including dam construction, channel deviation, and groundwater pumping, all of which result in a water deficit.

Paleolimnological studies allow to better understand changes in a lake's hydrological regime over long timescales [START_REF] Dearing | Why Future Earth needs lake sediment studies[END_REF], providing boundary conditions that help establish sustainable management strategies of water resources [START_REF] Coops | The role of waterlevel fluctuations in shallow lake ecosystems-workshop conclusions[END_REF]. In arid and semi-arid regions of Iran, sediment archives from hydrologically closed lakes have demonstrated their high potential for deciphering paleohydrological changes [START_REF] Stevens | Hydroclimatic variations over the last two glacial/ interglacial cycles at Lake Urmia, Iran[END_REF][START_REF] Jones | Human impact on the hydroenvironment of Lake Parishan, SW Iran, through the late-Holocene[END_REF][START_REF] Aubert | Late glacial and early Holocene hydroclimate variability in northwest Iran (Talesh Mountains) inferred from chironomid and pollen analysis[END_REF]) through a range of biotic and abiotic indicators (ostracods, diatoms, chironomids, oxygen isotopes of endogenic carbonates). Fewer investigations have reconstructed lake paleohydrology in Iran with sedimentology and major element geochemistry, with the exception of Lake Urmia [START_REF] Kelts | Holocene sedimentology of hypersaline Lake Urmia, Northwestern Iran[END_REF] and the recent studies on Lake Neor [START_REF] Sharifi | Abrupt climate variability since the last deglaciation based on a high-resolution, multi-proxy peat record from NW Iran: the hand that rocked the Cradle of Civilization?[END_REF]. These proxies may provide valuable highresolution data from which lake desiccation and fluvial activity can be reconstructed [START_REF] Neugebauer | Hydroclimatic variability in the Levant during the early last glacial (* 117-75 ka) derived from micro-facies analyses of deep Dead Sea sediments[END_REF]. In this study, we present new high-resolution sedimentological (dry bulk density, micro-facies analysis, X-ray diffraction) and major element (X-ray fluorescence) analyses of MAH-B, a 3.5-m-long sediment core, to investigate centennial-scale variations in the hydrology of Lake Maharlou for the last 3800 years.

Site description

Lake Maharlou is located 10 km southeast of the city of Shiraz (29°29 0 N, 52°45 0 E), in an intermontane depression of the Zagros Fold-Thrust Belt. The lake, with an elevation of 1460 m a.s.l., lies in a vast, 3928-km 2 endorheic watershed surrounded by mountains that reach 2800 m a.s.l. Basement rocks mainly consist of Mesozoic/Cretaceous limestone-dolomites and marls. Several evaporitic outcrops, including gypsum, anhydrite, and halite beds, are exposed in the eastern part of the lake [START_REF] Faghih | Geomorphologic assessment of relative tectonic activity in the Maharlou Lake Basin, Zagros Mountains of Iran[END_REF]Fig. 1).

Iranian climate is characterised by hot and dry summers associated with northerly winds (i.e. Shamal) from the Mediterranean high to South Asian monsoon low [START_REF] Tyrlis | The summer circulation over the eastern Mediterranean and the Middle East: influence of the South Asian monsoon[END_REF]. Persistence of this synoptic pattern produces great dust storms along the Persian Gulf that do not affect the southern continental slope of the Zagros [START_REF] Nabavi | Climatology of dust distribution over West Asia from homogenized remote sensing data[END_REF]. Winters are dominated by cold dry air from the Siberian high. Penetration of the most intense depressions from the Atlantic and Mediterranean triggers winter and spring precipitation [START_REF] Alijani | Synoptic climatology of precipitation in Iran[END_REF], especially in the Zagros massif where snow is deposited at high altitude.

Lake Maharlou was a nearly permanent lake in the recent past, but since its near desiccation during summer 2002, seasonal drying of the lake has become a common phenomenon [START_REF] Dumas | Le fonctionnement hydroclimatique de la cuvette de Maharlou (Iran)[END_REF][START_REF] Fayazi | Hydrochemistry and brine evolution of Maharlou saline lake, Southwest of Iran[END_REF]. Today, the depth of the lake varies seasonally from a completely dried surface in summer months to about 3.5 m in early spring. The depth of the basin is greater to the northwest (Fig. 1). The area of the lake at a high stand of 3.5 m depth is 275 km 2 123 [START_REF] Dumas | Le fonctionnement hydroclimatique de la cuvette de Maharlou (Iran)[END_REF]. A detailed hydrologic study of the lake based on instrumental measurements from 1988 to 1992 and hydroclimate data provided by the Karstic Research Center of Teheran showed that inputs to the lake originate from catchment runoff (85%) and karstic springs (15%) that feed two rivers, Khoshk and Baba Adji (specific discharge of 3.59 and 1.85 L/ s/km 2 , respectively). These rivers form a delta in the northern part of the lake [START_REF] Dumas | Le fonctionnement hydroclimatique de la cuvette de Maharlou (Iran)[END_REF]. Karstic losses, a common phenomenon in Zagros [START_REF] Rezaei | Interaction of a fresh water lake and a karstic spring via a syncline fold[END_REF], are considered negligible since the basin floor is covered by a thick impermeable clay deposit. Precipitation is seasonal, occurring mainly from January to April. Annual mean precipitation is estimated at 350 mm/year (Shiraz station). During the monthlyinstrumented period of 1988, the negative balance between precipitation and evaporation was compensated for by karstic inputs, preventing complete drying of the lake [START_REF] Dumas | Le fonctionnement hydroclimatique de la cuvette de Maharlou (Iran)[END_REF]. Altogether, the hydrological regime of Lake Maharlou is driven by 123 karstic resurgence throughout the year, winter/spring rainfall, and summer evaporation. The watershed of Lake Maharlou is also occupied by a dense network of surface and underground tunnels (qanats) and small water pools that are partially abandoned today (Fig. 1b). These infrastructures, essentially located in foothills, provide a freshwater supply for agriculture and pastoral activities on the plain.

Materials and methods

Four contiguous drives (MAH-B-D1, D2, D3 and D4), each 1 m in length, were taken with a Russian Corer in the southwest quadrant of the northwestern depression of Lake Maharlou (29°27 0 40.5 00 N; 52°43 0 45.6 00 E) in September 2012. Main sedimentary facies were described using macroscopic visual features (colour, texture and structure, presence of macrofossils). The result is a master core, 355 cm in length, designated MAH-B.

Seven samples were radiocarbon dated at the Poznan Radiocarbon Laboratory. To avoid contamination by fossil organic carbon and the 'hard-water effect,' only botanical macroremains and charcoals were dated. Because of the paucity of terrestrial macroremains, sediment samples were wet sieved at 100 lm, avoiding the use of alcohol. Terrestrial organic particles were then picked one by one under a binocular microscope. Humic acid removal pretreatment (Poznan Radiocarbon Laboratory) was skipped because of the small weight of the sample for preparation of graphite. The age-depth model was developed using a smooth spline (type 4 argument) in the Clam R package [START_REF] Blaauw | Methods and code for ''classical'' age-modelling of radiocarbon sequences[END_REF], based on probability distributions of the 14 C ages, and the IntCal13 calibration curve [START_REF] Reimer | IntCal13 and Marine13 radiocarbon age calibration curves 0-50,000 years cal BP[END_REF]. Ten thousand iterations were run to calculate the best age probability and 2r envelope. Salt layers that represent rapid sedimentation were considered instantaneous deposits and were excluded from the age-depth model.

Two sediment segments (110 mm 9 20 mm) were sampled for thin sections at 110-120 cm and 279-291 cm. The segments were freeze-dried and impregnated with epoxy resin (MK Factory) under vacuum following the procedure of [START_REF] Brauer | Chronology and depositional processes of the laminated sediment record from Lac d'Annecy, French Alps[END_REF]. Polished slides were observed under a compound microscope at 109, 509, and 1009 magnification (IMBE laboratory). XRF elemental analysis was performed on a 1-m-long U-Channel with an ITRAX TM core scanner (Cox Analytical Systems) at the CEREGE laboratory. High-resolution visual scans were acquired with an optical camera before covering the sediment with polyethylene foil to prevent drying during analysis. The radiographic scan was done at 200-lm increments with parameters fixed at 45 kV, 40 mA and a dwell time of 700 ms. The relative abundances of Si, K, Fe, Ti, Ca, S, Sr, Cl were measured by X-ray excitation using a Mo-source tube set at 30 kV and 45 mA for 15 s, at a step of 500 lm. Significant changes in the geochemical composition were defined by cluster analysis, both stratigraphically constrained and unconstrained, using the CONISS algorithm of the Rioja R package [START_REF] Juggins | C2 v.1.5, User guide. Software for ecological and palaeoecological data analysis and visualisation[END_REF]. The number of significant zones was defined by comparison to the Broken-stick model [START_REF] Bennett | Determination of the number of zones in a biostratigraphical sequence[END_REF]. A visual layer counting was done with the support of a high-resolution optical scan, a radiographic scan, and XRF element variations. The minimal resolution of layer counting was 1 mm.

Contiguous sub-samples, 2-cm thick, were collected on the remaining core. Seventy samples of a constant volume of 7 cm 3 were taken at approximately 10-cm intervals, dried at 60 °C for 48 h, weighed to calculate dry bulk density, and then crushed using an agate mortar. Additionally, two surface sediment samples, one from the Khoshk riverbed, and one from soil on the west bank of the lake near the coring site (Fig. 1), were analysed to characterize detrital mineral species of the watershed. Mineral composition of 20 bulk samples was characterised by X-ray diffraction on powder deposited on zero-background silicon plates (CEREGE laboratory) with a PANalytical X'Pert Pro diffractometer. To verify that drying temperature did not modify mineralogical species, one air-dried sample (\ 25 °C) was measured. Samples were scanned from 5°to 70°(2h), with an increment step of 0.033°and an acquisition time per sample of 3 h. The X-ray emission source, cobalt (k = 1.79 A ˚), was set at 40 kV and 40 mA. Peak identification was performed using the automated peak-match software X'Pert High Score Plus [START_REF] Degen | The highscore suite[END_REF].

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Results

Chronology

Of the seven AMS 14 C ages (Table 1), six were used to create the chronological model. Given its very low carbon weight (0.03 mg C), Poz-83775 (269 cm) was very close to the detection limit of the instrument and was rejected. The remaining ages are stratigraphically coherent if either sample Poz-83773 or Poz-81500 is excluded (Fig. 2). These two samples have low but equivalent weights of carbon (0.1 mg C). Poz-83773 comprises a mixture of numerous half-mm-long particles of charcoal, seeds, and insects, whereas Poz-81500 consists solely of charcoal (* 3 mm long). The most common cause of age bias in dating terrestrial material from lake sediment is long-term retention in the lake catchment. It is more likely that Poz-83773 was reworked than that Poz-81500 was rejuvenated. Sample Poz-83775 was accepted a posteriori because the 2r calibration range fits the model uncertainty. Thus, the final age-depth model is based on six 14 C dates. The age-depth model (Fig. 2) indicates that MAH-B spans the last 3800 ± 370 years, with an average 2r uncertainty of 250 years. The highest sedimentation rates occurred from 3700 to 3250 cal year BP (mean = 1.5 mm/year). The sedimentation rate was lowest (0.5 mm/year) between 3250 and 1000 cal year BP, increased from 2000 to 400 cal year BP (1.1 mm/ year), and decreased again from 400 cal year BP to Present (0.4 mm/year).

Bulk sediment composition

MAH-B is composed of very thinly bedded (1-2-cm thick) to laminated (0.1-1 cm) sediments that display an alternation of sand-size crystals and beige to light brown, silt-clay layers (Fig. 3). Contacts between beds are generally sharp, mainly because of the abrupt changes in particle size. The dry bulk density varies between 1.2 and 2.0 g/cm 3 . The upper 30 cm of the core is exclusively halite, reflecting the presence of the decimetre-thick salt crust encountered during coring. XRD measurements indicate the presence of both chemical and clastic components in all 19 samples. The comparison between the samples dried at different temperatures (25 °C vs 60 °C) indicates that sample desiccation induced a partial dehydration of gypsum to bassanite. Thus, the presence of bassanite is a preparation artifact and is considered to have been gypsum. Ranking minerals from the most dominant to least, the sediment consists of a constant presence of gypsum (CaSO 4 Á2H 2 O), halite (NaCl), strontium in aragonite (CaCO 3 -Sr), calcite (CaCO 3 ), quartz (SiO 2 ), muscovite (KAl 2 (Si,Al)O 10 (OH) 2 ) and chlorite ((Mg,Fe) 3 (Si,Al) 4 O 10 ). Dolomite (CaMg(CO 3 ) 2 ) and celestine (SrSO 4 ) occur regularly, but XRD peak heights are lower. Occurrences of pyrite (FeS 2 ) at 92 and 337 cm, glauberite (Na 2 Ca(SO 4 ) 2 ) at 32 cm, and )) at 159, 281 and 349 cm were also noted. Mineralogical analysis of the surface sediment from the west bank of the lake near the coring site, as well as the sample from the Khoshk riverbed, the main tributary river of Lake Maharlou (Fig. 1), showed a similar composition of mostly quartz and calcite, with minor amounts of dolomite.

Lithofacies

Microscopic examination of thin sections and sieved fractions greater than 100 lm provided qualitative information on sediment texture and constituents, enabling the designation of three lithofacies (Table 2).

Coarse Crystal Beds (CCB) are characterised by the nearly exclusive presence of euhedral mm-size halite crystals free of finer matrix (Fig. 4b). CCBs are represented in dark grey on the radiograph (Fig. 4a).

Beige to grey Silt-Clay Beds (SCB) consist of nongraded silt particles of mainly palisade gypsum crystals (g1 in Fig. 4c), rounded gypsum crystal (g2 in Fig. 4c) and aragonite (Fig. 4d) with some halite crystals in association with a finer matrix of calcite (Fig. 4e) and clay. Dark SCB (D-SCB) are richer in clay compared to lighter SCB (L-SCB). These beds are represented in medium grey in radiographic images (Fig. 4a). Homogeneous Clay Beds (HCB) consist of non-graded fine-silt to clay with scattered amorphous The occurrence of the three lithofacies is repetitive down core. Most of the 26 CCBs (excluding the modern one) were deposited between 145 cm and the core top. CCB thickness ranges between 0.2 and 35.7 cm, with an average of 1.0 cm. L-SCB (224 beds) and D-SCB (196 beds) are relatively homogeneously distributed along the profile, with thicknesses ranging from 0.1 to 2.9 cm and average values of 0.42 and 0.48 cm, respectively. The 385 HCB have thicknesses ranging between 0.1 and 3.5 cm (mean 0.3 cm). HCBs are thicker between 285 and 260 cm ([ 1 cm).

Geochemical variations

Depth-constrained cluster analysis of the high-resolution XRF profiles revealed four geochemical groups: K-Ti-Fe, Sr, Ca-S, and Cl. K-Ti-Fe are mostly associated with Sr and to a lesser extent with Ca and S. Cl is an isolated unit (Fig. 3).

The Cl group

Cl intensity represents halite abundance in the bulk sediment. The larger Cl fluctuations correspond to CCB, although isolated crystals of halite sometimes occur in lithofacies L-SCB and D-SCB (Fig. 4A-1 andA-2). Cl intensities are minimum in HCB beds characterised by higher detrital minerogenic elements (Fe, Ti, K).

The group Ca, S

Ca can be associated with gypsum, aragonite, calcite, and dolomite, whereas S may originate from gypsum, pyrite, and celestine. Both elements, however, are more concentrated in light SCBs (Fig. 4a) that consist mainly of gypsum and aragonite. Low correlation 123 between S and Fe, the rare occurrence of pyrite in the entire sediment sequence (Fig. 3), and the low S intensities in the samples where pyrite was detected by XRD, indicate that S does not track pyrite. Poor correlation between S and Sr concentrations, along with the rare presence of celestine (Fig. 4a), also argues that S does not track celestine. The positive linear relationship between S and Ca likely reflects the dominance of gypsum in controlling the S concentration, but the modest correlation coefficient (r = 0.5; n = 6360) suggests that Ca values are also affected by other Ca-rich minerals (calcite, aragonite, and dolomite). Comparison between the ratio Ca/S (data not shown) and detrital elements presents a moderate positive correlation (e.g. with K, r = 0.33). This relationship suggests that some of the Ca may have a detrital origin. This supposition is supported by the presence of Mesozoic/Cenozoic carbonate rocks in the watershed and the presence of these minerals in riverbed sediments. Together, these results show that Ca probably has multiple mineral associations and origins (i.e. endogenic and allochthonous), whereas S is more securely driven by gypsum abundance only. As gypsum minerals occur mainly as palisade crystals, the main process of gypsum deposition in the lake sediment is as in situ, perpendicular growth relative to

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the sedimentation surface, in a hypersaline pool. In lesser abundance, abraded gypsum crystals suggest allochthonous processes that may be associated with mechanical erosion from evaporitic outcrops or reworking by wind on the exposed dry lake surface. Absence of gypsum in riverbed sediments, together with the lack of a relationship between S and detrital element (K, Fe, Ti), refutes the hypothesis of supply by rivers.

The group K, Ti, Fe

Intensities of these elements are highest in HCBs and relatively high in D-SCBs. This group is associated with the presence of muscovite, chlorite and palygorskite minerals. Muscovite and chlorite are products of weathering of Mesozoic/Cenozoic rocks and are incorporated into the lake sediments as terrigenous, silt-clay-sized particles that are transported by fluvial or eolian processes. Although origin of palygorskite mineral may be detrital or endogenic, its occurrence in Lake Maharlou is associated only with the HCB lithofacies, suggesting a strictly detrital origin. Moreover, if the Si XRF signal is low (data not shown), Si shows the same variability as K, Ti, and Fe, indicating the concordance of quartz together with phyllosilicates in HCB. Rare presence of diatoms confirms this interpretation. Two alternative interpretations can be proposed for the detrital element group. K, Ti, Fe may mostly track phyllosilicates that are deposited from turbid river discharge during heavy rainfall and thus be related to relatively high lake level, or phyllosilicates may be of eolian origin signalling arid conditions and thus be related to lake desiccation.

The Sr group

Peaks of Sr intensities are generally, but not exclusively, associated with L-SCBs and D-SCBs. Higher Sr intensities occur at depths where no celestine was recorded (e.g. 280-340 cm). Besides, Sr is often used to track Sr-rich aragonite (Bo ¨ning and Bard 2009) that possibly reflects the abundance of aragonite-rich fecal pellets of the brine shrimp, Artemia (Fig. 4c). The lack of correlation between Ca and Sr, however, cannot confirm this hypothesis. Dominance of gypsum likely overrides the less abundant aragonite and complicates the Ca/Sr relationship.

Discussion

Defining palaeoenvironmental proxies

Halite and gypsum as indicators of lake desiccation

The sedimentological and geochemical analyses of MAH-B revealed a large range of biochemical and evaporitic products that are characteristic of different stages of concentration of the water (brine), related to retraction of the lake. Along the gradient of brine ionic concentration, low-solubility minerals such as calcite, aragonite and dolomite, are precipitated first, followed by gypsum, and finally halite [START_REF] Hardie | The evolution of closed-basin brines[END_REF]. Based on the analysis of the ion concentration of Lake Maharlou brine in summer 2002 and spring 2005, [START_REF] Fayazi | Hydrochemistry and brine evolution of Maharlou saline lake, Southwest of Iran[END_REF] showed that during the driest conditions the salt crust comprises only halite, whereas under wetter conditions, several evaporite minerals, including mainly halite, gypsum, and calcium, are precipitated. In MAH-B, gypsum is mainly present in the form of elongated prismatic crystals and occurs in SCBs in association with carbonates and scattered halite grains. Gypsum formation requires a pool of water for the growth habit of the crystals.

In addition to variations in brine concentrations, other environmental factors can affect which minerals are deposited in a lake. Heterogeneities of basin morphology and proximity to freshwater inputs induce spatial variability with respect to the saturation point of different minerals [START_REF] Bowler | Spatial variability and hydrologic evolution of Australian lake basins: analogue for pleistocene hydrologic change and evaporite formation[END_REF], which are reached at different stages of water body contraction, depending on the location of the coring site (Rahimpour-Bonab and Abdi 2012). Distribution of cation concentrations in surface waters of Lake Maharlou indicates that the southeast of the lake has higher concentrations of Na ? and Cl - [START_REF] Fayazi | Hydrochemistry and brine evolution of Maharlou saline lake, Southwest of Iran[END_REF] than the northeast deep basin, which is fed by the main tributaries. The MAH-B core site was located in the latter deep basin, but relatively close to the lake margin (Fig. 1). This location is more prone to surface crust formation than the deepest part of the lake, but less so than the shallower southern plateau. Thus, MAH-B is sensitive to an intermediate stage of water body contraction, corresponding to half the maximum current lake surface. Post-depositional mineral dissolution caused by cyclic flooding-desiccation also affects the integrity of hydrologic reconstruction [START_REF] Last | Sedimentology and geochemistry of saline lakes of the Great Plains[END_REF]. Dissolution is a differential process, first affecting the most soluble salts. Thus, despite the fact that gypsum can represent the complete record of changes in lake sedimentation, more soluble halite layers probably underestimate the number and intensity of past extreme desiccation events. Thus, gypsum abundance, tracked by S XRF intensity, is interpreted as an indicator of hypersaline conditions in Lake Maharlou, with some water still present. The frequency of indurated halite beds (CCB lithofacies) is interpreted as the residue of summer salt crusts, which indicate desiccation of more than 50% of the lake surface, thus corresponding to very low lake levels (\ 1 m) even in the deepest part of the lake.

Detrital fraction as an indicator of river activity

Detrital minerals (phyllosilicates and quartz) have been identified in HCB and D-SCB lithofacies and characterised by high XRF intensities of K, Ti, and Fe.

123

These minerals have two possible origins, eolian or alluvial. Dust storms that carry high sediment loads originate from two main atmospheric patterns. Shamal summer winds, oriented northwest-southeast, come from the Mediterranean and produce large dust deposits along the Euphrates Valley to the Persian Gulf. Frontal winds, coming from Saudi Arabia, generate dust storms in the northern part of the Zagros to the Caspian Sea [START_REF] Nabavi | Climatology of dust distribution over West Asia from homogenized remote sensing data[END_REF]. A retrospective atmospheric analysis, covering the period 1980 to Present [START_REF] Nabavi | Climatology of dust distribution over West Asia from homogenized remote sensing data[END_REF], indicated that the Lake Maharlou Basin has not received substantial dust transport, in part because of the protected position of the basin with respect to the dominant summer winds [START_REF] Rezazadeh | Climatology of the Middle East dust events[END_REF]). The same situation was observed for a major dust storm in July 2009, which did not trigger dust deposition in the study region [START_REF] Hamidi | Numerical simulation of dust events the Middle East[END_REF]). In addition, mineralogical and elemental studies of dust deposited in sediment traps in the Persian Gulf, along the Iranian coast, indicated the dust was dominated by calcite (60%) and quartz (15%) minerals [START_REF] Ahmady-Birgani | Mineralogy and geochemistry of atmospheric particulates in western Iran[END_REF], with grain sizes of silt and clay. In Lake Maharlou sediments, although the grain size of dust is similar to the HCBs particles, these beds have low to no calcite content and are depleted in Ca (Fig. 4a). It is thus unlikely that detrital-rich HCBs correspond to dust-storm deposits. In contrast, the hypothesis of terrigenous input from rivers is supported by the occurrence of intense floods along the Khoshk River in the last few decades, which caused economic losses in the city of Shiraz (e.g. in December 1986 and February 1998) [START_REF] Kowsar | Envelope curves for extreme flood events in SW Iran[END_REF][START_REF] Mardaneh | Groundwater flood risk ''Khoshk'' river in Shiraz[END_REF][START_REF] Jamali | Spatial analysis of geomorphological hazards of urban development in the Banks of Khoshk River in Shiraz, Iran[END_REF]. Historical archives also mention major floods that devastated the town in AD 1630 and 1668. The hydrograph of the Khoshk River system indicates discharges of 200 and 350 m 3 /s with return periods of 25 and 100 years, respectively [START_REF] Rivaz | Effect of bridges on the river hydrograph characteristics along the ephemeral rivers system[END_REF]. Considering these two possible origins of the detrital material, i.e. dust storms and river supply, the latter is more likely to cause HCB layers and increases in K intensities.

HCB lithofacies are characterised by absence of graded microfabrics, suggesting that detrital sediment supply entered the lake and that the kinetics of deposition results from uniform suspension in the water column [START_REF] Siegenthaler | Slump induced surges and sediment transport in Lake Uri, Switzerland[END_REF]. The absence of internal, microscopic, graded bedding may also result from deposition distal from the river mouth [START_REF] Czymzik | Orbital and solar forcing of shifts in Mid-to Late Holocene flood intensity from varved sediments of pre-alpine Lake Ammersee (southern Germany)[END_REF]. MAH-B is located in the same northern basin as the river delta and in the path of the entering flow. The mouth of Khoshk River forms a vast (8.5-km-wide), relatively flat (3°slope), fluviolacustrine delta that encompasses the entire width of the lake. This complex deltaic environment consists of numerous wetlands in which divergent streams, both intermittent and perennial, flow. Taking into account the low potential velocity and relatively low stream discharge, two explanations for the absence of coarse detrital particles in MAH-B are (i) quasi-permanent presence of dense aquatic vegetation (Juncus, Phragmites) in wetlands developed in the Khoshk River Delta environment, which buffer and trap the coarse sediment fraction, and (ii) sediment supply feeding the lake system and the coring site consists of turbid waters, with only clays/silts in suspension.

Climate: a forcing mechanism for hydrologic changes in Lake Maharlou?

to 2000 cal year BP (period A): enhanced detrital supply during wetter climate conditions

The base of MAH-B, from 3800 to 2000 cal year BP, records peak abundance of terrigenous sediment (high K intensities, Fig. 5). High fluvial activity during this period corresponded with relatively low evaporative concentration of the lake. Rare phases of lake contraction (inferred from S intensities and CCB frequency, Fig. 5), however, did occur at 3700-3650, 3500-3450, and 3400-3250 cal year BP. Thus, this period is interpreted as having an overall positive hydrological balance, corresponding to higher river flow and lower water loss through evaporation. Superimposed on these general conditions are three K peaks and a peak in HCB frequency from 3800 to 3250 cal year BP. Enhanced detrital supply could be caused by rapid snow melt or large spring rains [START_REF] Masih | Streamflow trends and climate linkages in the Zagros Mountains, Iran[END_REF], possibly related to a highly unstable climate. Alternatively, it could be caused by the river adjusting course, moving its mouth closer to the coring location. From 3250 to 2000 cal year BP, flood frequency and K intensities decreased, suggesting more stable hydrological conditions and fewer pulses of fluvial sediment.

Higher river discharge in the Maharlou catchment fits well with other records that show a period of river alluviation in the Pulvar [START_REF] Rigot | Dynamique de la rivie `re Poulvar et morphogene `se de la plaine de Tang-i Bulaghi (Fars, Iran) a l'Holoce `ne[END_REF] and Kor (Kehl 123 Fig. 5 Palaeohydrology reconstructed from Lake Maharlou proxies compared to records in southwest Asia, as a function of age (cal year BP). a Qunf Cave, southern Oman [START_REF] Fleitmann | Holocene forcing of the Indian Monsoon recorded in a stalagmite from Southern Oman[END_REF][START_REF] Fleitmann | Holocene ITCZ and Indian monsoon dynamics recorded in stalagmites from Oman and Yemen (Socotra)[END_REF]. b Socotra Cave, Yemen [START_REF] Van Rampelbergh | Mid-to late Holocene Indian Ocean Monsoon variability recorded in four speleothems from Socotra Island, Yemen[END_REF]; Hoti Cave, northern Oman [START_REF] Fleitmann | Holocene ITCZ and Indian monsoon dynamics recorded in stalagmites from Oman and Yemen (Socotra)[END_REF]). c Level of the Caspian Sea [START_REF] Rychagov | Holocene oscillations of the Caspian Sea, and forecasts based on palaeogeographical reconstructions[END_REF][START_REF] Kroonenberg | Solarforced 2600 BP and Little Ice Age highstands of the Caspian Sea[END_REF]). d Lake Zeribar [START_REF] Stevens | Proposed changes in seasonality of climate during the Lateglacial and Holocene at Lake Zeribar, Iran[END_REF][START_REF] Snyder | Diatombased conductivity reconstruction and palaeoclimatic interpretation of a 40-ka record from Lake Zeribar, Iran[END_REF]). e Lake Mirabad [START_REF] Stevens | Timing of atmospheric precipitation in the Zagros Mountains inferred from a multi-proxy record from Lake Mirabad, Iran[END_REF]). f Lake Parishan, Iran [START_REF] Jones | Human impact on the hydroenvironment of Lake Parishan, SW Iran, through the late-Holocene[END_REF]. g Historical cultural periods in the Fars region (Iran) and attention paid to repair and construction of new qanats. h Historical archives citing drought or famine in Iran [START_REF] Frye | The history of ancient Iran[END_REF][START_REF] Melville | Meteorological hazards and disasters in Iran: a preliminary survey to[END_REF][START_REF] Daryaee | Sasanian Persia: the rise and fall of an empire[END_REF]. i Geomorphic record of the Pulvar fluvial valley of the Persepolis basin, Iran [START_REF] Rigot | Dynamique de la rivie `re Poulvar et morphogene `se de la plaine de Tang-i Bulaghi (Fars, Iran) a l'Holoce `ne[END_REF]. j Geomorphic record of the Central Iranian Plateau [START_REF] Schmidt | Holocene settlement shifts and palaeoenvironments on the Central Iranian Plateau: investigating linked[END_REF]. k Geomorphic record of the Wadi ad Dawasir in central Saudi Arabia [START_REF] Matter | Reactivation of the Pleistocene trans-Arabian Wadi ad Dawasir fluvial system (Saudi Arabia) during the Holocene humid phase[END_REF]. l Inter-dune lake Awafi [START_REF] Parker | A record of Holocene climate change from lake geochemical analyses in southeastern Arabia[END_REF] and Idhn in United Arab Emirates [START_REF] Goudie | Latest Pleistocene and Holocene dune construction at the north-eastern edge of the Rub Al Khali, United Arab Emirates[END_REF]. m northern Arabian Sea offshore marine record [START_REF] Lu ¨ckge | Monsoonal variability in the northeastern Arabian Sea during the past 5000 years: geochemical evidence from laminated sediments[END_REF] 123 et al. 2009) River Valleys, which are located 50 km north of Lake Maharlou in the Persepolis Basin (Fig. 5i), alluviation in the northern part of the Iranian Plateau (Schmidt et al. 2011, Fig. 5j) and in the Arabian Peninsula (Matter et al. 2016, Fig. 5k). River terrace formation probably indicates that sediment was available on slopes and that water discharge was sufficient to transport those sediments. More humid conditions, which would be associated with stable river input, also explain the reduction in evaporative concentration of the lake surface. A generally wetter climate with pulsed river activity is consistent with the presence of inter-dune wetlands that indicate short-lived wet phases in the Arabian Peninsula (Parker et al. 2006, Fig. 5l) and in a marine record from the Gulf of Oman (Lu ¨ckge et al. 2001, Fig. 5m). The interpretation of wetter conditions in Southwest Asia from 3800 to 2000 cal year BP is also consistent with proxies that are more sensitive to effective moisture (Fig. 5a,b,c) than are geomorphic records. Lower values of the d 18 O of speleothems from Qunf Cave in Oman [START_REF] Fleitmann | Holocene forcing of the Indian Monsoon recorded in a stalagmite from Southern Oman[END_REF], 2007, Fig. 5a) and in Gejkar Cave in Iraq [START_REF] Flohr | Late Holocene droughts in the Fertile Crescent recorded in a speleothem from northern Iraq[END_REF], and higher levels of the Caspian Sea (Rychagov 1997, Fig. 5c), all argue for a regional increase in moisture. In the Iranian Plateau, higher lake levels from 3700 to 1900 cal year BP are documented by dominance of aquatic plants in the pollen diagram from Lake Almalou, with a peak high stand between 3700 and 3400 cal year BP (Djamali et al. 2009a). In Lake Parishan, some 100 km to the west of Lake Maharlou, both geochemical and paleoecological proxies suggest that between 3800 and 2200 cal year BP the lake was higher than periods before and after this interval [START_REF] Jones | Human impact on the hydroenvironment of Lake Parishan, SW Iran, through the late-Holocene[END_REF].

to Present (period B): increasing aridification and more lake low stands

The main change in the catchment/lake hydrology occurred at ca. 2000 cal year BP, with an increase in gypsum abundance attesting to more evaporative conditions in the lake and decreased terrigenous input (Fig. 5). The timing of the transition is consistent with a major environmental change recorded in geomorphic records from the Iranian Plateau and the Arabian Peninsula (Fig. 5i-l): increased river incision and dune development at that time suggest drier climatic conditions. More arid conditions in this region are in phase with a lower Caspian Sea level [START_REF] Rychagov | Holocene oscillations of the Caspian Sea, and forecasts based on palaeogeographical reconstructions[END_REF]) and more positive d 18 O values from the Qunf Cave [START_REF] Fleitmann | Holocene forcing of the Indian Monsoon recorded in a stalagmite from Southern Oman[END_REF]. A transitory increase in the detrital supply in Lake Maharlou between 1300 and 1100 cal year BP is concomitant with increased alluvial sediment deposition in the Persepolis Basin (Fig. 5i) that may reflect a short phase of more humid conditions [START_REF] Rigot | Dynamique de la rivie `re Poulvar et morphogene `se de la plaine de Tang-i Bulaghi (Fars, Iran) a l'Holoce `ne[END_REF].

From 1100 to 700 cal year BP (period B2, Fig. 5), Lake Maharlou experienced maximum reduction of its water body and very frequent desiccation events, as revealed by high gypsum abundance and frequent deposition of halite beds (CCB frequency), respectively. Dune formation and dust events in the Arabian Peninsula [START_REF] Goudie | Latest Pleistocene and Holocene dune construction at the north-eastern edge of the Rub Al Khali, United Arab Emirates[END_REF][START_REF] Lu ¨ckge | Monsoonal variability in the northeastern Arabian Sea during the past 5000 years: geochemical evidence from laminated sediments[END_REF] suggest that a more arid climate might be responsible for the extreme evaporation of Lake Maharlou. In the Persepolis Basin, soils developed on previously deposited terraces [START_REF] Rigot | Dynamique de la rivie `re Poulvar et morphogene `se de la plaine de Tang-i Bulaghi (Fars, Iran) a l'Holoce `ne[END_REF], also suggesting very low fluvial activity. Speleothem records from northern and southern Oman seem to also indicate several short periods of drought [START_REF] Fleitmann | Holocene ITCZ and Indian monsoon dynamics recorded in stalagmites from Oman and Yemen (Socotra)[END_REF]). The most compelling argument, however, is the frequency of drought and famine recorded in historical archives from Iran during this interval [START_REF] Daryaee | Sasanian Persia: the rise and fall of an empire[END_REF][START_REF] Sharifi | Abrupt climate variability since the last deglaciation based on a high-resolution, multi-proxy peat record from NW Iran: the hand that rocked the Cradle of Civilization?[END_REF]Fig. 5h).

Lake Maharlou underwent few desiccation periods and was likely a perennial water body from 700 calyear BP to Present (period B3, Fig. 5), as indicated by a decrease in halite crust formation and gypsum abundance. Detrital input, however, remained low. These conditions correspond to fewer droughts and famines in Iran [START_REF] Daryaee | Sasanian Persia: the rise and fall of an empire[END_REF]. Hoti and Qunf Cave [START_REF] Fleitmann | Holocene forcing of the Indian Monsoon recorded in a stalagmite from Southern Oman[END_REF][START_REF] Fleitmann | Holocene ITCZ and Indian monsoon dynamics recorded in stalagmites from Oman and Yemen (Socotra)[END_REF] display modest decreases in d 18 O at that time, suggesting relatively wetter climatic conditions than in period B2. This interval corresponds roughly to the Little Ice Age (600-150 cal year BP), during which cooling associated with lower solar irradiance and higher frequency of stratospheric volcanic eruptions may have reduced evaporation stress (greater effective moisture), resulting in less halite crust formation at Lake Maharlou. Similar results are documented for Lake Almalou (Djamali et al. 2009a) and Caspian Sea level [START_REF] Beni | Caspian Sea-level changes at the end of Little Ice Age and its impacts on the avulsion of the Gorgan River: a multidisciplinary case study from the southeastern flank of the Caspian Sea[END_REF]. Contrasting dynamics, however, have been documented at other sites, suggesting a decrease in effective moisture [START_REF] Jones | A highresolution late Holocene lake isotope record from Turkey and links to North Atlantic and monsoon climate[END_REF][START_REF] Flohr | Late Holocene droughts in the Fertile Crescent recorded in a speleothem from northern Iraq[END_REF]) that may have induced lower lake level. Finally, coherence between many proxy records from 123 the Mediterranean and Southwest Asia, with respect to a general drying trend from the middle to late Holocene, may be explained by a weakening of the winter storm tracks that originate from the Mediterranean and North Atlantic, even if regional-scale experiments suggest a much more complex circulation pattern [START_REF] Brayshaw | Past climates of the Middle East[END_REF]) caused by the orography in this region [START_REF] Zarrin | The effect of the Zagros Mountains on the formation and maintenance of the Iran Anticyclone using RegCM4[END_REF].

Equivocal palaeohydrological interpretations of lake records in the Zagros Massif: how strong was the influence of humans?

Comparisons with geomorphic and speleothem archives suggest that hydrological changes at Lake Maharlou were driven by late Holocene climatic changes that were manifest over much of southwest Asia. Comparison of the record presented here with those from three other lakes in the Zagros Massif [Lake Zeribar (Fig. 5d), Lake Mirabad (Fig. 5e) and Lake Parishan (Fig. 5f)], however, reveals complexities. During the last 4000 years, the lowest d 18 O values measured on endogenic calcite at Mirabad and Zeribar occurred during periods of high terrigenous supply at Lake Maharlou (Fig. 5). Then at 2000 cal year BP, increasing d 18 O values corresponded to an increase of gypsum abundance in Lake Maharlou. These general trends suggest a common forcing factor affected lake-water balances of the Zagros region. It has been proposed, however, that d 18 O values are not controlled entirely by hydrologic balance [START_REF] Jones | Interpreting lake isotope records of Holocene environmental change in the Eastern Mediterranean[END_REF], and that the seasonality of precipitation should be considered [START_REF] Snyder | Diatombased conductivity reconstruction and palaeoclimatic interpretation of a 40-ka record from Lake Zeribar, Iran[END_REF][START_REF] Stevens | Proposed changes in seasonality of climate during the Lateglacial and Holocene at Lake Zeribar, Iran[END_REF][START_REF] Stevens | Timing of atmospheric precipitation in the Zagros Mountains inferred from a multi-proxy record from Lake Mirabad, Iran[END_REF]. In Lake Parishan, [START_REF] Jones | Human impact on the hydroenvironment of Lake Parishan, SW Iran, through the late-Holocene[END_REF] did not find any common climatic explanation for the increase of the d 18 O with changes in ostracod assemblages, and variations of other geochemical and biological indicators occurring at 2000 cal year BP. These authors invoked large-scale anthropogenic disturbances of the water cycle in the watershed to explain variations in the lake hydro-geochemistry.

With respect to Lake Maharlou, anthropogenic activities caused or simply amplified the decrease in both fluvial activity and lake volume. Notably, the HCB frequency and K intensities diverge after 2000 cal year BP, suggesting a modification of the relationship between the flood frequency and the sediment supply. This pattern could be explained by ecological and geomorphic factors in the face of climate variability, possibly influenced by anthropogenic activities [START_REF] Brisset | The overlooked human influence in historic and prehistoric floods in the European Alps[END_REF]. For example, lower detrital supply with relatively frequent flood events may suggest that the erosive effect of precipitation and runoff was buffered by vegetation cover in the lake catchment, a change in the ratio of discharge to sediment load [START_REF] Brisset | Sediment budget quantification of a sub-Alpine river catchment since the end of the last glaciation[END_REF], development of riparian vegetation along the river banks and the delta, or by sediment mining for urban development [START_REF] Rinaldi | Sediment mining in alluvial channels: physical effects and management perspectives[END_REF].

A 4800-year pollen diagram from another core taken in Lake Maharlou (Djamali et al. 2009b(Djamali et al. , 2010a, b) , b) shows that vegetation cover was generally dominated by Quercus and Pistacia, scrub species typical of the Zagros Mountains. A marked increase in Juglans, Platanus, and Olea in that core, however, attests to intensification of cultivation practices and urban development, both of which were favoured by advances in irrigation techniques. Temporal comparisons with this core are not possible because radiocarbon ages were obtained on bulk carbonate (Djamali et al. 2009b) and variable reservoir effect prevents reconciliation with dates on macrofossils. Effective management of water resources has been a common way to cope with arid conditions in Southwest Asia [START_REF] Magee | The chronology and environmental background of Iron Age settlement in Southeastern Iran and the question of the origin of the Qanat irrigation system[END_REF]. Archaeological findings indicate that subterranean tunnels (i.e. qanat or kariz systems) were used to drain groundwater from foothills to irrigate plains since the 1st and possibly 2nd millennium BCE [START_REF] Tikriti | The south-east Arabian origin of the falaj system[END_REF][START_REF] Magee | The chronology and environmental background of Iron Age settlement in Southeastern Iran and the question of the origin of the Qanat irrigation system[END_REF][START_REF] Fattahi | OSL dating of the Miam Qanat (Ka ¯riz) system in NE Iran[END_REF]). Because of the strong concentration of precipitation in winter/spring seasons throughout most of the Iranian Plateau, the introduction of qanat technology provided access to perennial water sources, modifying people's ability to subsist within this region [START_REF] Manuel | The sustainability of ancient water control techniques in Iran: an overview[END_REF]. Estimates of the number of functioning qanats in Iran range from 22,000 to 36,000 (Semsar [START_REF] Yazdi | A historical review on the Qanats and historic hydraulic structures of Iran since the first millennium BC[END_REF]. The length of some qanats may extend over several hundred km, with most ranging from 5 to 10 km [START_REF] Wilkinson | From human niche construction to imperial power: long-term trends in ancient Iranian water systems[END_REF]. The qanat irrigation network located in the watershed of Lake Maharlou is very dense (Fig. 1b). Even if a large number of those qanats are currently abandoned, their high abundance argues for strong disturbances in the drainage basin of the lake through changes in groundwater input to the lake, which in turn would accelerate lake drying. The importance given to the management of the water supply has not been the same throughout the different 123 empires that ruled in Persia ('Persis') (Fig.

According to [START_REF] Manuel | The sustainability of ancient water control techniques in Iran: an overview[END_REF], little attention was paid to water system sustainability during the Seleucid and Parthian Empires (2197-1726 cal year BP), whereas during the reign of the Sasanians (1726-1300 cal year BP), the state supported the development and maintenance of qanats, but also surface water networks. Thus, the turning points in Lake Maharlou hydrology coincide with these imperial periods: the first major reduction of the water body (gypsum abundance, period B1 in Fig. 5) occurred at 2160-1980 cal year BP (2r). Then, the period of more frequent, nearly complete drying of the lake (CCB bed frequency, period B2 in Fig. 5), occurred during the Islamic period, while qanats were still utilised [START_REF] Manuel | The sustainability of ancient water control techniques in Iran: an overview[END_REF]. The long-term utilisation of the water resources, over millennia, may thus have been an important factor in Lake Maharlou drying during the past, similar to the situation at neighbouring Lake Parishan [START_REF] Jones | Human impact on the hydroenvironment of Lake Parishan, SW Iran, through the late-Holocene[END_REF].

Finally, temporal synchronicity of climate proxies and intensity of human activities suggest that both climate and human drivers influenced Lake Maharlou hydrological changes over the last four millennia. Even if it remains difficult to decipher the relative role of each forcing factor on the lake's evolution, a probable and parsimonious interpretation might be that large-scale climate changes may have induced a water deficit that was further aggravated by alteration of the water cycle by anthropogenic activities. Thus, in the face of the global change and an increasing need for fresh water for agriculture and urban use, particular attention should be given to sustainable water resource management. Historical instrumental records, combined with secular to millennial-scale records of hydrological changes, provide helpful information to understand the function of water resources.

Conclusions

Analyses carried out on core MAH-B from Lake Maharlou reveal four past hydro-environmental states:

(1) near or total desiccation of the lake (frequency of halite beds), (2) an intermediate phase of lake water body retraction (gypsum abundance), (3) high terrigenous sediment supply from rivers (potassium abundance), and (4) river flood occurrence (frequency of the individual beds of homogeneous clays). Of these four states, two major periods were identified over the last 3800 years. From 3800 to 2000 cal year BP, the terrigenous supply was high (notably in the intervals 3700-3650, 3500-3450, and 3400-3250 cal year BP), and evaporative conditions of the lake surface were relatively low. From 2000 cal year BP to Present, an increase in gypsum attests to more evaporative conditions, concomitant with a decrease in fluvial activity. The contraction of the water body reached a maximum from 1100 to 700 cal year BP, during which the lake frequently dried.

The comparison of the Lake Maharlou records to geomorphic activity and to climatically driven regional records suggests that a common climate forcing controlled late Holocene hydrology in southwest Asia. Comparison with the lake records located in the Zagros Massif is more challenging because these records yielded equivocal conclusions about hydrological changes inferred from different climate proxies. Indeed, ancient human impact on local and regional hydrologic balance is likely to have impacted lake systems for millennia. Subterranean tunnels (qanats) are an important component of the Maharlou watershed. Periods of construction of new qanats and repair (Sassanid and Islamic periods) seem to have corresponded to the dramatic contraction of the water body, suggesting that human disturbances of the water cycle in the lake watershed played a role in the lake water deficit, along with climate change. As both periods of climatic change and human impact correspond to hydrological variability of Lake Maharlou, we suggest that weaker winter storm tracks originating from the Mediterranean may have induced water shortage that was aggravated by human activity, leading to more frequent drying of Lake Maharlou. In turn, scarcity of the water resource has had a severe impact on food security, as famines have coincided with exceptionally frequent lake drying during the last millennium.

Fig. 1 a

 1 Fig. 1 a Spatial distribution of annual precipitation in Iran and location of the study site near the city of Shiraz (white star). b Map of the Lake Maharlou watershed, including topography, geology, hydrology, and anthropogenic features. Note that map details differ between the northern and southern part of the watershed because several sources of information were integrated. The black star indicates the MAH-B coring location. The two black dots indicate the location of the surface sediment

Fig. 3

 3 Fig. 3 Lithostratigraphy, mineralogy, dry bulk density, XRF elemental profiles, and lithofacies deposition in core MAH-B. Mineralogical species are abbreviated: Hal Halite, Gyp Gypsum, Cel Celestine, Gla Glauberite, Pyr Pyrite, Ara Aragonite,

Fig. 4 a

 4 Fig. 4 a Macro-and microscopic characterisation of the lithofacies from two sediment segments corresponding to two thin sections A-1 (110-120 cm) and A-2 (279-291 cm). Lithofacies (L) distinction (white: Coarse Crystal Beds (CCB); light grey: Light Silt-Clay Beds (L-SCB); dark grey: Dark Silt-Clay Beds (D-SCB); and black: Homogeneous Clay Beds (HCB)), photographic image (P), radiographic scan image (R), and superposed thin-slide optical scans and high-resolution

Table 1

 1 Radiocarbon ages obtained on core MAH-B

	Core	Core section	Master core	Material	Laboratory	Age 14 C BP	Age cal year BP	Weight
	section	depth (cm)	depth (cm)		code		(± 2r)	(mg C)
	D1	43	43	Charcoals,	Poz-81502	390 ± 30 BP	320-509	0.2
				Coleoptera, seed
	D1	88	88	Plant fragment	Poz-81501	655 ± 35 BP	556-673	0.15
	D2	62-70	159	Charcoals,	Poz-83773 2450 ± 50 BP 2359-2707	0.12
				Coleoptera, seed
	D3	14	193	Charcoal	Poz-81500 1950 ± 50 BP	1741-2002	0.1
	D3	58-66	237	Charcoals,	Poz-83774 2820 ± 90 BP	2762-3162	0.07
				Coleoptera
	D3	90-96	269	Charcoals,	Poz-83775 3800 ± 180 BP 3717-4803	0.03
				Coleoptera, seed
	D4	66-74	321	Charcoals,	Poz-83776 3370 ± 35 BP	3496-3697	0.16
				Coleoptera, seed

The rejected age is in italics 123 palygorskite ((Mg,Al) 2 Si 4 O 10 (OH)Á4(H 2 O

Table 2

 2 Sedimentological and geochemical composition of the MAH-B lithofacies

	Lithofacies	Description	Main	XRF	Layer thickness	Interpretation
	(CODE)		minerals	element	(mm)
	Coarse Crystal	Transparent euhedral cubic	Halite	Cl	From 0.2 to	Residual indicator of a summer
	Bed (CCB)	crystal (mm-size)			3.4 cm (mean:	salt crust indicating a complete
					1.0 cm),	drying of the lake surface
					excluding the
					35.7 cm of top
					core
	Beige to grey	Non-graded silt-clay mud made	Gypsum	S, Ca	L-SCB (Light	Sediment accumulation
	Silt-Clay	of palisade gypsum crystal,			Silt-Clay Bed):	dominated by dilution between
	bed (SCB)	eroded gypsum, aragonite and of a finer matrix comprising slightly rounded rhombs to axially symmetric ellipsoids of calcite, with muscovite and	Celestine Calcite	S, Sr Ca	From 0.1 to 2.9 cm (mean: 0.4 cm)	three main chemical components (halite, calcium sulphate and calcium carbonate) and of a fourth clastic inorganic (quartz,
		chlorite	Aragonite	Sr, Ca	D-SCB (Dark	muscovite and chlorite).
					Silt-Clay Bed):	Presence of subangular gypsum
			Dolomite	Ca	From 0.1 to	crystals indicates eolian
					2.5 cm (mean:	deflation
					0.4 cm)
			Quartz	Si
		The fraction [ 100 lm (Fig. 3)	Muscovite	K, Fe,		Beds are lighter or darker
		is composed of few halite		Ti		depending on mineral
		crystals (h), gypsum needles (g), Artemia cysts (a), concretion of Artemia pellets	Chlorite Palygorskite			abundance in evaporate/calcium carbonates or in clay. Lighter beds indicate
		(p), charcoal particles,				mainly chemical precipitation,
		gastropods and ostracods				and darker ones a more
						important detrital supply in a
						context of sedimentation
						dominated by chemical
						precipitation
	Homogeneous	Non-graded clastic fine-silty to	Quartz	Si	From 0.1 to	Clastic detrital inputs
	Clay Bed (HCB)	clayey mud. Charcoals and amorphous particles are scattered within the bed	Muscovite Chlorite	K, Ti, Fe	3.5 cm (mean: 0.3 cm)	intercalating the biochemical lacustrine sedimentation, indicating phases of abundant
						river detrital supply

Acknowledgements This study was funded by the Franco-German ANR/DGF titled PALEO-PERSEPOLIS (ANR-14-CE35-0026-01). The authors thank M. Ko ¨hler (MK Factory) for thin-section preparation and T. Goslar (Poznan Radiocarbon Laboratory) for 14 C measurements and related details on sample preparation and blank correction. A. Naderi-Beni and M. Pourkerman from the Iranian National Institute for Oceanography and Atmospheric Sciences are thanked for their help with the coring operation. We are grateful to the reviewers and M. Brenner (Editor in Chief of JOPL) for their salient suggestions for improvement of the manuscript.