Hydroclimate Reconstructions Research Articles

Hydroclimate reconstruction during the last 1000 years inferred from the mineralogical and geochemical composition of a sediment core from Lake-Azuei (Haiti)

This study aims to reconstruct the hydro-climatic variations over the last 1000 years in Haiti using mineralogical and geochemical composition of well dated lacustrine sediment core retrieved from Lake Azuei. The results show changes in sedimentological processes linked to environmental and climatic variations. The general pattern suggests a wetter Medieval Climate Anomaly (MCA), drier Little Ice Age (LIA), high climate variability during the MCA-LIA transition and more anthropogenic impacts that dominate natural climate during the Current Warm Period (CWP). The MCA period (~1000–1100 CE) thus appears marked by increase sedimentation rate supported by higher terrigenous input linked to erosive events particularly increases in precipitation. During the LIA, particularly from ~1450 to 1600 CE, there is a great variation toward a decrease of terrigenous input, which is related to a decrease on sedimentation rate and increase Mg-calcite precipitation, suggesting less precipitation and high evaporation respectively during dry climate conditions. The MCA-LIA transition (~1200–1400 CE) is characterized by variations between terrigenous input, Mg-calcite formation and organic matter deposition, which indicate succession of dry and humid conditions. The CWP (1800–2000 CE) shows a progressive increase on sedimentation rate and decrease of gray level, which indicate more organic matter sedimentation as consequence of anthropogenic activities in the surrounding basin of the lake. High-resolution gray level analysis, which reflects principally variations in terrigenous input, carbonate mineral formation and organic matter deposition, shows that the AMO, NAO, PDO and ENSO are the principal modes affecting the hydro-climatic changes in Haiti during the last millennium. In addition, temporal correlation of other Caribbean paleoclimate records with our geochemical and mineralogical data, suggests that trends observed in Lake Azuei were controlled by regional climate, likely associated with shifts in the position of the ITCZ.

A 2.5° × 2.5° gridded drought/flood grades dataset for eastern China during the last millennium

Hydroclimate reconstruction for the last millennium is essential to understand the differences in hydroclimate extremes and their causes under cold/warm conditions. In this study, the first gridded drought/flood grades (D/F grades) dataset in eastern China (EC) during the last millennium was generated. This D/F grades dataset mainly consisted of two components. The first section was created by interpolating drought/flood grades from 1500 to 2000 using the angular distance weight method. Sampling error estimates were employed to assess the effects of the interpolated dataset. The second section for the D/F grades dataset during 960–1500 was generated by constructing best subset regression models using selected tree-ring chronologies in the United States through atmospheric teleconnection. The validation parameters of the calibration equations were also derived, including the adjusted R2, predicted R2, RE, and CE. This dataset provides critical support for investigating the characteristics and causes of hydroclimate extremes in EC at various spatiotemporal scales, as well as the relationship with climate modes, such as El Niño-Southern Oscillation, Pacific Decadal Oscillation, and East Asia Summer Monsoon.

Drought increase since the mid-20th century in the northern South American Altiplano revealed by a 389-year precipitation record

Abstract. Given the short span of instrumental precipitation records in the South American Altiplano, longer-term hydroclimatic records are needed to understand the nature of climate variability and to improve the predictability of precipitation, a key natural resource for the socioeconomic development in the Altiplano and adjacent arid lowlands. In this region grows Polylepis tarapacana, a long-lived tree species that is very sensitive to hydroclimatic changes and has been widely used for tree-ring studies in the central and southern Altiplano. However, in the northern sector of the Peruvian and Chilean Altiplano (16–19∘ S) still exists a gap of high-resolution hydroclimatic data based on tree-ring records. Our study provides an overview of the temporal evolution of the late-spring–mid-summer precipitation for the period 1625–2013 CE at the northern South American Altiplano, allowing for the identification of wet or dry periods based on a regional reconstruction from three P. tarapacana chronologies. An increase in the occurrence of extreme dry events, together with a decreasing trend in the reconstructed precipitation, has been recorded since the 1970s in the northern Altiplano within the context of the last ∼4 centuries. The average precipitation over the last 17 years stands out as the driest in our 389-year reconstruction. We reveal a temporal and spatial synchrony across the Altiplano region of dry conditions since the mid-1970s. Independent tree-ring-based hydroclimate reconstructions and several paleoclimatic records based on other proxies available for the tropical Andes record this synchrony. The influence of El Niño–Southern Oscillation (ENSO) on the northern Altiplano precipitation was detected by our rainfall reconstruction that showed past drier conditions in our study region associated with ENSO warm events. The spectral properties of the rainfall reconstruction showed strong imprints of ENSO variability at decadal, sub-decadal, and inter-annual timescales, in particular from the Pacific NIÑO 3 sector. Overall, the recent reduction in precipitation in comparison with previous centuries, the increase in extreme dry events and the coupling between precipitation and ENSO variability reported by this work is essential information in the context of the growing demand for water resources in the Altiplano. This study will contribute to a better understanding of the vulnerability and resilience of the region to the projected evapotranspiration increase for the 21st century associated with global warming.

European tree-ring isotopes indicate unusual recent hydroclimate

In recent decades, Europe has experienced more frequent flood and drought events. However, little is known about the long-term, spatiotemporal hydroclimatic changes across Europe. Here we present a climate field reconstruction spanning the entire European continent based on tree-ring stable isotopes. A pronounced seasonal consistency in climate response across Europe leads to a unique, well-verified spatial field reconstruction of European summer hydroclimate back to AD 1600. We find three distinct phases of European hydroclimate variability as possible fingerprints of solar activity (coinciding with the Maunder Minimum and the end of the Little Ice Age) and pronounced decadal variability superimposed by a long-term drying trend from the mid-20th century. We show that the recent European summer drought (2015–2018) is highly unusual in a multi-century context and unprecedented for large parts of central and western Europe. The reconstruction provides further evidence of European summer droughts potentially being influenced by anthropogenic warming and draws attention to regional differences.

Climate change during the last deglaciation at central equatorial African mountains

The “inverse modelling through iterative forward modelling” (IMIFM) approach is used to reconstruct the last deglaciation climates from central equatorial African mountains. Unlike other approaches that use statistical models, it directly incorporates the effects of changes in atmospheric CO2 concentrations on vegetation through a process-based vegetation model, but the results strongly depend on the model used. Therefore, two generally related but different equilibrium vegetation models are used for evaluating the dependence of the results on the choice of vegetation model. Our climate reconstructions show that long-term temperature increases during the last deglaciation, as seen in Greenland, were absent from many of the target sites. Moreover, there are few common long-term trends of climatic responses during the last deglaciation among central equatorial African mountains’ sites despite the relatively close of those sites. No systematic climate responses were also found between the eastern and western sides of the Congo basin. While there is consistency in the long-term trends and their amplitudes regarding temperature reconstructions with both models, there are large differences between the sites in the long-term hydroclimatic reconstructions, particularly during arid periods. This difference may be attributed to the carbon-water use efficiency in the vegetation models. This study implies that the IMIFM approach is effective for climate reconstructions in equatorial African mountains, where modern pollen samples are not plentiful. Although low atmospheric CO2 concentrations do not largely influence temperature reconstructions for the last deglaciation, they significantly affect the hydroclimate reconstructions, especially when drought-tolerant biomes are dominant.

An 1800-year oxygen-isotope record of short- and long-term hydroclimate variability in the northern neotropics from a Jamaican marl lake

Hydroclimate variability on multi-decadal timescales has been a prominent feature of the circum-Caribbean region over the common era, with marked dry intervals noted in particular for the period 800–950 CE coinciding with the Terminal Classic Period (the so-called Terminal Classic Drought: TCD) in Mesoamerica, and with the Little Ice Age from about 1500 to 1800 CE, linked to complex ocean-atmosphere interactions. Previous compilations of palaeoclimate reconstructions have revealed a clear precipitation dipole between northern and southern Mesoamerica over the common era, which is consistent with meteorological data and modelling experiments. However, patterns of variability elsewhere within the region are less well understood, although palaeoclimate records do point to spatial complexity. Here, we present a ∼sub-decadal-scale lake-sediment hydroclimate reconstruction based on ostracod-shell stable isotopes from Wallywash Great Pond, Jamaica, covering the past ∼1800 years, which fills a spatial gap in records for the region. Variations in δ18O values at this site are a proxy for changes in effective moisture and they reveal a marked wet phase over the Terminal Classic Period (TCP), suggesting that the precipitation dipole over northern and southern Mesoamerica may have an east to west component. This is supported by some previous studies, although additional sites are required from strategic localities within the region to confirm this. The Little Ice Age interval at Wallywash is drier than the TCP, although the signal is less clear than at some sites within the wider region, suggesting that regional complexity in hydroclimate has characterised this interval as well.

A Bayesian time series model for reconstructing hydroclimate from multiple proxies

AbstractWe propose a Bayesian model which produces probabilistic reconstructions of hydroclimatic variability in Queensland Australia. The model provides a standardized approach to hydroclimate reconstruction using multiple palaeoclimate proxy records derived from natural archives such as speleothems, ice cores and tree rings. The method combines time‐series modeling with inverse prediction to quantify the relationships between a given hydroclimate index and relevant proxies over an instrumental period and subsequently reconstruct the hydroclimate back through time. We present case studies for Brisbane and Fitzroy catchments focusing on two hydroclimate indices, the Rainfall Index (RFI) and the Standardized Precipitation‐Evapotranspiration Index (SPEI). The probabilistic nature of the reconstructions allows us to estimate the probability that a hydroclimate index in any reconstruction year was lower (higher) than the minimum (maximum) value observed over the instrumental period. In Brisbane, the RFI is unlikely (probabilities < 5%) to have exhibited extremes beyond the minimum/maximum values observed between 1889 and 2019. However, in Fitzroy there are several years during the reconstruction period where the RFI is likely (>50% probability) to have exhibited behavior beyond the minimum/maximum of what has been observed, during the instrumental period. For SPEI, the probability of observing such extremes prior to the beginning of the instrumental period in 1889 doesn't exceed 30% in any reconstruction year in Brisbane, but exceeds 50% in multiple years in Fitzroy.

Baldcypress false ring formation linked to summer hydroclimatic extremes in the southeastern United States

We describe the utility of false rings in Taxodium distichum (i.e. baldcypress) as a proxy for hydroclimatic extreme events in three different river basins (Pascagoula, Mobile, and Choctawhatchee) that discharge into the northern Gulf of Mexico. False rings occur as a result of a change in the environmental limiting resource for tree stem growth, and in T. distichum, false ring production is usually a result of increases in mid-growing season water availability. Our results show that false ring occurrence (from 1931 to 2018) is similar across sites but occur in different years, suggesting that false ring production is indicative of tree response to its local environment. False ring production in T. distichum has previously been correlated with summer streamflow, the season when tropical cyclone precipitation (TCP) is highest. To assess a stand-wide response, we define high false ring (HFR) years as all years when 20% of trees produced a false ring. We show total TCP in July is the best predictor for HFR years in T. distichum, and false ring production in smaller river basins captures local TCP better than larger river basins. Additionally, HFR years coincide with summers of anomalously high precipitation, anomalously low temperatures, and a positive phase of the North Atlantic Oscillation. 77% of HFR years occur in seasons when there is heavy tropical cyclone activity near sample sites, building a foundation to use false ring records as robust TCP proxies with hydroclimate reconstruction potential.

Hydroclimate reconstruction through MIS 3 in the Middle Paleolithic site of Crvena Stijena (Montenegro) based on hydrogen-isotopic composition of sedimentary n-alkanes

This study presents a hydroclimatic reconstruction from Crvena Stijena (Montenegro, Balkan Peninsula), a rock shelter that has yielded evidence for Middle Paleolithic human occupation. The integration of lipid biomarkers, hydrogen (δD) isotopic compositions of n-alkanes, and organic elemental geochemistry in the 7-m deep vertical sedimentary sequence enables reconstruction of the main hydrological and environmental changes during the MIS 3 and their correlation with the presence at the site. We apply agglomerative hierarchical clustering and principal component analysis to the geochemical, molecular, and stable isotopic data to obtain a robust hydrological record. We find evidence of three aridity trends from the studied period, one of them correlated with the Heinrich Event 5, and humid and cold-temperate conditions in archaeology-rich layers. Our dataset also contributes to the knowledge of past hydrological variability in the Balkan Peninsula, a sensitive area to short-lived climatic shifts, and overall, in the Mediterranean region during the last glacial/interglacial cycle.

Drought and water management in ancient Maya society

Paleoclimate research in the Maya region of Mesoamerica provides compelling evidence of drought during key periods of cultural transition in Maya society. These include the transition from the Preclassic to the Classic, and from Classic to the Postclassic. Previous research emphasized a causal relationship between drought and cultural change, or so-called “collapse” in the Maya region. Recent advances in the range and precision of climate-sensitive proxies and the development of new archives have enabled quantitative reconstructions of past hydroclimate, as well as providing evidence of high impact, short-duration events, such as tropical cyclones. Simultaneously, archaeological research has unearthed widespread evidence of technologies used by the Maya to exert control over water resources in urban, rural, and agricultural settings. Evidence suggests that many of these water features were in use for multiple generations, possibly centuries, and many were constructed during the Terminal Preclassic and Terminal Classic periods. We suggest that, given the availability of new archaeological and paleoclimate records, these data can be combined to identify the full complexity of Maya adaptation to hydroclimate variability to emphasize adaptation and resilience to both water scarcity and over-abundance (e.g., flooding). Such syntheses, which can offer lessons for present-day efforts to grapple with regional climate change, will benefit from additional studies in data-poor zones of the Maya region, as well as public archiving of paleoclimate and archaeological data.

Insight into spatial-temporal patterns of hydroclimate change on the Chinese Loess Plateau over the past 250 years, using new evidence from tree rings

The climate aridity since the mid-20th century has raised concerns about water resources on the Chinese Loess Plateau (CLP). A lack of extended observation-like precipitation records for the eastern CLP (ECLP) means that it remains unclear whether or not the current arid state of the CLP is unprecedented, and the spatial-temporal characteristics of hydroclimatic variability across the CLP over past centuries are not well understood. Here we present a regional hydrological-year precipitation reconstruction for the Heichashan Mountains, which successfully captures hydroclimate changes on the ECLP since 1773 CE. The reconstruction explains 48.72 % of the observed variance for 1957–2019 CE and reveals a wetting trend since the early 2000s and shows 2014–2020 CE to have been the second wettest period over the past 248 years. 1910–1932 CE was the longest and driest period over the past centuries. Furthermore, the 19th century was relatively wet, whereas the 20th century was dry. We demonstrate that droughts tend to occur in warm periods. Combining our new reconstruction with previously published hydroclimatic reconstructions, we find that hydroclimate has changed synchronously on the ECLP and the western CLP (WCLP) for most of the past two centuries. Some regional differences do exist, for example in the 1890s–1920s, when aridity gradually intensified across the ECLP, no similar drying is evident in records for the WCLP, although the 1920s megadrought occurred in both the ECLP and WCLP. Another difference is in the onset of the 20th-century aridity, which began in the 1950s on the ECLP, around 20 years later than it began on the WCLP. In addition to the known influences of the Asian Summer Monsoon and related large-scale circulations, this work highlights a major finding that the 1920s megadrought may be related to a regime shift in Northern Hemisphere temperature.

The feasibility of reconstructing hydroclimate over West Africa using tree-ring chronologies in the Mediterranean region

Dendrochronology in West Africa has not yet been developed despite encouraging reports suggesting the potential for long tree-ring reconstructions of hydroclimate in the tropics. This paper shows that even in the absence of local tree chronologies, it is possible to reconstruct the hydroclimate of a region using remote tree rings. We present the West Sub-Saharan Drought Atlas (WSDA), a new paleoclimatic reconstruction of West African hydroclimate based on tree-ring chronologies from the Mediterranean Region, made possible by the teleconnected climate relationship between the West African Monsoon and Mediterranean Sea surface temperatures. The WSDA is a one-half degree gridded reconstruction of summer Palmer Drought Severity indices from 1500 to 2018 CE, produced using ensemble point-by-point regression. Calibration and verification statistics of the WSDA indicate that it has significant skill over most of its domain. The three leading modes of hydroclimate variability in West Africa are accurately reproduced by the WSDA, demonstrating strong skill compared to regional instrumental precipitation and drought indices. The WSDA can be used to study the hydroclimate of West Africa outside the limit of the longest observed record and for integration and comparison with other proxy and archaeological data. It is also an essential first step toward developing and using local tree-ring chronologies to reconstruct West Africa’s hydroclimate.

Past 200 kyr hydroclimate variability in the western Mediterranean and its connection to the African Humid Periods

The Iberian Peninsula is located at the intersection between the subtropical and temperate climate zones and the paleoclimate records from this region are key to elucidate the varying humidity and changing dominance of atmospheric circulation patterns in the Mediterranean-North African region in the past. Here we present a quantitative hydroclimate reconstruction for the last ca. 200 kyr from southern Iberian Peninsula based on pollen data from the Padul lake sediment record. We use the newly developed Scale-normalized Significant Zero crossing (SnSiZer) method to detect not only the statistically significant precipitation changes but also to estimate the relative magnitude of these oscillations in our reconstruction. We identify six statistically significant main humid phases, termed West Mediterranean Humid Periods (WMHP 1–6). These humid periods correlate with other West/Central Mediterranean paleohydrological records, suggesting that similar climatic factors affected different areas of the Mediterranean. In addition, the WMPHs are roughly coeval with the African Humid Periods (AHPs) during high seasonality, suggesting the same North Atlantic ocean-atmospheric dynamics and orbital forcing as main drivers of both areas. In contrast, during low seasonality periods, the West Mediterranean still appears to be affected by the westerlies and the local Mediterranean rainfall systems with moderate-to-high precipitation, whereas West Africa was characterized by droughts.

Highly resolved δ13C and trace element ratios of precisely dated stalagmite from northwestern China: Hydroclimate reconstruction during the last two millennia

Compared with the widely used stable oxygen isotope (δ18O), the climate response of the stable carbon isotope (δ13C) of speleothems in monsoonal China has received less attention, mainly because of its relatively complex controlling factors. Nevertheless, an increasing number of studies are suggesting that δ13C can represent hydroclimatic changes. Here, we present highly resolved continuous δ13C and trace element ratio records of a speleothem from Wanxiang Cave, northwestern China, spanning the last two millennia. Our results show that δ13C values oscillated around the mean value on centennial scales, indicating that the overlying vegetation types and soil humidity did not change significantly. High consistency was found between detrended δ13C and δ18O (δ13Cd and δ18Od) records, suggesting that soil moisture balance and vegetation density related to the regional hydrological cycle is an important factor controlling δ13C variations on multidecadal-centennial scales. The regional hydrological cycle is mainly controlled by summer precipitation induced by the Asian summer monsoon (ASM) and the stable prior calcite precipitation (PCP), which was inferred from trace element ratio (Mg/Ca, Sr/Ca, Ba/Ca) records. The δ13C and trace element ratio records, consistent with δ18O throughout the considered periods, are not only closely coupled with the intensity of the El Niño-Southern Oscillation and north-south shift of the Intertropical Convergence Zone but also respond to solar activity and temperature variations in the Northern Hemisphere. However, both δ13C and trace element ratios exhibited a persistent significantly decreasing trend in the last 150 years. Furthermore, the variation of δ18O during the Current Warm Period (AD. 1850–2000) suggests that anthropogenic emissions of atmospheric CO2 and aerosols rather than ASM caused an unusual increase of regional precipitation and depletion of atmospheric δ13C, which induced increased infiltration of atmospheric CO2 and available water into soil pores and caves without any obvious PCP effect. The abnormal changes in our speleothem δ13C are analogous to the oceanic 13C Suess effect, suggesting that stalagmite δ13C record is greatly affected by atmospheric CO2 concentration under global warming.

A tree ring-based hydroclimate reconstruction for eastern Europe reveals large-scale teleconnection patterns

We present a new beech (Fagus sylvatica L.) tree-ring width composite chronology from five natural low-elevation forests in eastern Romania, which represent the species’ continental distribution limit. Our regional beech chronology reflects April–June hydroclimate variability in form of the Standardized Precipitation Evapotranspiration Index over large parts of Romania, Ukraine, and the Republic of Moldova, for which high-resolution paleoclimatic evidence is broadly missing. Most of the reconstructed hydroclimatic extremes back to 1768 CE are confirmed by documentary evidences, and a robust association is found with large-scale atmospheric circulation patterns in the Northern Hemisphere and sea surface temperatures over the North Atlantic. Reconstructed pluvials coincide with a high-pressure system over the North Atlantic Ocean and north-western Europe, and with a low-pressure system over south-western, central and eastern Europe, whereas historical droughts coincide with a high-pressure system over Europe and a low-pressure system over the central part of the Atlantic Ocean. Our study demonstrates the potential to produce well-replicated, multi-centennial beech chronologies for eastern Europe to reconstruct regional hydroclimate variation and better understand the causes and consequences of large-scale teleconnection patterns.

Regional Drought Conditions Control Quercus brantii Lindl. Growth within Contrasting Forest Stands in the Central Zagros Mountains, Iran

The magnitude and duration of ongoing global warming affects tree growth, especially in semi-arid forest landscapes, which are typically dominated by a few adapted tree species. We investigated the effect of climatic control on the tree growth of Persian oak (Quercus brantii Lindl.), which is a dominant species in the Central Zagros Mountains of western Iran. A total of 48 stem discs was analyzed from trees at three sites, differing in local site and stand conditions (1326 to 1704 m a.s.l.), as well as the level and type of human impact (high human intervention for the silvopastoral site, moderate for the agroforestry site, and low for the forest site). We used principal component analysis (PCA) to investigate the common climatic signals of precipitation, air temperature, and drought (represented by SPEI 1 to 48 months) across the site chronologies. PC1 explains 83% of the total variance, indicating a dominant common growth response to regional climatic conditions that is independent of the local environmental conditions (i.e., forest stand density and land-use type). Growth–climate response analyses revealed that the radial growth of Q. brantii is positively affected by water availability during the growing season (r = 0.39, p < 0.01). Precipitation during April and May has played an ever-important role in oak growth in recent decades. Our study provides evidence that hydroclimatic conditions control tree-ring formation in this region, dominating the effects of topography and human impact. This finding highlights the great potential for combining historical oak samples and living trees from different forest stands in order to generate multi-centennial tree-ring-based hydroclimate reconstructions.

Carbon and hydrogen isotopes of taraxerol in mangrove leaves and sediment cores: Implications for paleo-reconstructions

Reconstructing past climate change in mangrove swamps contextualizes ongoing and future developments in these globally important ecosystems. Taraxerol, a well-recognized lipid biomarker for mangroves, is a promising target compound for calibration since it is relatively refractory and well preserved in sediments and since mangrove lipid δ2H and δ13C values have been shown to respond to salinity changes. Here we investigate the δ2H and δ13C values of taraxerol in leaves of two mangrove species (Rhizophora mangle and Laguncularia racemosa) and three dated mangrove cores along a spatial transect from the Shark River Estuary of South Florida, USA, to constrain its applicability for hydroclimate reconstructions. The net 2H discrimination between surface water and taraxerol increased by 1.0‰ ppt−1 over a salinity range of 0.7–32 ppt for both R. mangle and L. racemosa. Although the δ13C values of taraxerol showed a significant positive correlation with salinity in L. racemosa, the inverse trend was observed in R. mangle. The isotopic signature and spatial trends of taraxerol observed in mangrove leaves were well imprinted in mangrove surface sediments.In addition, we further tested if the isotopic signal of taraxerol from mangrove leaves could be preserved in sediment cores on a time scale of ca. 300 yrs. No strong evidence of significant diagenetic alteration was observed for δ2H values of taraxerol. In contrast, an increase up to ∼1.1‰ was observed for δ13C, excluding the Suess effect. Considering the consistent salinity-dependent discrimination of 2H to salinity, and no significant diagenetic alteration of taraxerol δ2H values on centennial time scales, taraxerol H isotopes are a promising proxy for hydroclimate reconstruction in mangrove and mangrove-adjacent systems. However, the interpretation of δ13C values of taraxerol should be treated with caution since its correlation with salinity may be species-specific and a slight diagenetic enrichment in 13C may occur.

Assessing the robustness of geochronological records from the Arabian Peninsula: A new synthesis of the last 20 ka

The timing and extent of Late Quaternary climate and environmental changes in the Arabian Peninsula were critical for human demographic changes. High resolution palaeoclimate archives suggest that monsoon variability was a key driver of change, but these records obscure environmental heterogeneity at finer spatial scales. Recent decades have seen the production of new, chronometrically controlled records from a range of new sites, with a greater spatial coverage. However, records often appear contradictory vis a vis the hydro-climatic state of the environment and so synthesising them can be challenging. To enhance collation and interpretation of records we have compiled a new database of terrestrial and coastal environmental chronologies for the Arabian Peninsula over the last 20 ka, a key period of marked hydrological change. The SCAPE (Synthesising Chronologies for Arabian PalaeoEnvironments) database contains records that include >700 luminescence and radiocarbon ages. Robustness criteria are applied to identify the utility of each data source in regional hydroclimate reconstruction. The most robust data provide a unique synthesis of 20 ka of palaeoenvironmental change at sub-regional scales. We find that Arabian environmental change does not necessarily follow broad narratives of ‘wet’ or ‘dry’ states but rather the climatic signal is a mosaic of substantial landscape heterogeneity. SCAPE also highlights regions in which more high-quality geochronological investigation is warranted to refine both temporal and spatial records, signifying important avenues for future research.

Last glacial maximum hydro-climate and cyclone characteristics in the Levant: a regional modelling perspective

Proxy-based hydro-climate reconstructions in the Levant suggest enhanced water availability during the last glacial maximum (LGM) compared to present-day conditions. To date, the governing hypothesis is that additional water availability may be directly linked to increased Cyprus Low frequency and intensity in the region. However, this paradigm has not been tested in a modelling framework. With this aim, we analysed results from a weather type classification algorithm and regional climate simulations. The weather type classification is applied to ERA5 reanalysis data for present-day (1979–2018) and two Paleoclimate Modelling Inter-comparison Project PMIP3/PMIP4 pre-industrial and LGM model runs. Dynamical downscaling of the two models with the regional Weather Research and Forecast model shows that the present hydro-climate can largely be reproduced. Our simulations suggest that both evaporation and precipitation were lower in the LGM compared to pre-industrial conditions, and that their relative changes can thus most likely explain the additional water availability during that time. Indeed, evaporation in the eastern Mediterranean is reduced to a higher degree (∼−33%) as compared to precipitation (∼−20%) during the LGM. Particularly, lower evaporation during LGM summer may have sustained the year-round wetter conditions in the Levant. In addition, we find significant changes in Cyprus Low characteristics for the LGM. The simulated daily precipitation associated with Cyprus Lows is significantly lower than pre-industrial values (reduction of 26%–29%), whereas the wind intensity is stronger (increase of 7%–8%). Finally, a significant increase in Cyprus Low frequency during LGM winter is likely (+22%). Indeed, our findings are in line with a plethora of proxy-based reconstructions, and provide a reinterpretation of the driving mechanism of water availability, i.e. strong changes in evaporation rather than precipitation. This study places projected hydro-climatic drying of the Levant in a long timescale perspective. As such, it improves our understanding of the physical processes influencing the hydrological cycle in this vulnerable region, situated on the border between sub-tropical and mid-latitude climate zones.

Past millennium hydroclimate variability from Corsican pine tree‐ring chronologies

Palaeoclimatic evidence is necessary to place the current warming and drying trends of the Mediterranean region in a long‐term perspective of pre‐industrial variability. Annually resolved and absolutely dated climate proxies that extend back into medieval times are, however, limited to a few sites only. Here we present a network of long ring width chronologies from Pinus nigra tree‐line sites in northern Corsica (France) that cohere exceptionally well over centuries and support the development of a single high‐elevation pine chronology extending back to 974 CE. We apply various detrending methods to these data to retain high‐to‐low frequency ring width variability and scale the resulting chronologies against instrumental precipitation and drought observations to produce hydroclimate reconstructions for the last millennium. Proxy calibration and transfer are challenged by a lack of high‐elevation meteorological data, however, limiting our understanding of precipitation changes in sub‐alpine tree‐line environments. Our new reconstructions extend beyond existing records and provide evidence for low‐frequency precipitation variability in the central‐western Mediterranean from 974–2016 CE. Comparison with a European scale drought reconstruction network shows that regional predictor chronologies are needed to accurately estimate long‐term hydroclimate variability on Corsica.