Palaeo-seasonality of the last two millennia reconstructed from the oxygen isotope composition of carbonates and diatom silica from Nar Gölü, central Turkey

Abstract

a b s t r a c tCarbonates and diatoms are rarely deposited together in lake sediments in sufficient quantities for the oxygen isotope composition (d 18 O) to be investigated simultaneously from both hosts. Here, d 18 O carbonate are compared to d 18 O diatom data from the varved sediments of Nar Gölü, a closed lake in central Turkey, over the last 1710 years. Lake monitoring suggests carbonate is probably precipitated during MayeJune and d 18 O carbonate is a proxy for regional water balance. Diatom activity is mainly weighted towards the spring. At times between w301 and 561 AD, while d 18 O carbonate values are the highest for the entire 1710 year period, suggesting summer drought, d 18 O corrected-diatom values are among the lowest. d 18 O lakewatervalues estimated for the times of diatom growth and carbonate precipitation show large differences. We suggest this could be explained by increased snowmelt that formed a freshwater lid on the lake at the time of peak diatom growth. Increased snowmelt is also inferred w561e801 AD. From 801 AD to the present, precipitation is less winter-dominated, although increased snowmelt is inferred 921e1071 AD and in the latter part of the Little Ice Age (i.e. the mid to late 1800s AD). By combining oxygen isotope data from hosts that form in lakes at different times of the year, we show that such analyses can provide insights into palaeo-seasonality.

Northern Mediterranean climate since the Middle Pleistocene: a 637 ka stable isotope record from Lake Ohrid (Albania/Macedonia)

“…Stable isotope ratios preserved in sedimentary lacustrine carbonates are a proxy for past climate and hydrological change (Leng and Marshall, 2004), and combinations of lake records can be used to assess the spatial coherence of isotope variations (Roberts et al, 2008). Although there are numerous stable isotope records from the Mediterranean, for example from marine sediment cores (Piva et al, 2008;Maiorano et al, 2013;Regattieri et al, 2014) and speleothems (Bar-Matthews et al, 2003;Antonioli et al, 2004), those from lacustrine carbonate typically are Late Glacial-Holocene in age (Dean et al, 2013;Francke et al, 2013) and only a limited number of extend beyond the Last Glacial (Frogley et al, 1999;Kwiecien et al, 2014;Giaccio et al, 2015;Regattieri et al, 2016).…”

“…If lower temperatures persisted throughout much of the year, a higher proportion of annual precipitation may have fallen in winter as snow. Snow is typically characterised as having much lower δ 18 O than rainfall, which reflects in-cloud equilibrium conditions and cooler condensation temperatures (Darling et al, 2006), and so would provide a further potential source for low δ 18 O (Dean et al, 2013).…”

Spring temperature variability over Turkey since 1800 CE reconstructed from a broad network of tree-ring data

“…The box (dashed line) represents the area for which the temperature reconstruction was performed. (Wick et al, 2003;Jones et al, 2006;Roberts et al, , 2012Kuzucuoglu et al, 2011;Woodbridge and Roberts, 2011;Ülgen et al, 2012;Dean et al, 2013) and tree rings, have been used to reconstruct long-term hydroclimate conditions over Turkey. Tree rings in particular have shown to provide useful information about the past climate of Turkey and were used intensively during the last decade to reconstruct precipitation in the Aegean (Griggs et al, 2007), Black Sea (Akkemik et al, , 2008Martin-Benitto et al, 2016), Mediterranean regions (Touchan et al, 2005a), as well as the Sivas (D'Arrigo and Cullen, 2001), southwestern (Touchan et al, 2003(Touchan et al, , 2007Köse et al, 2013), south-central and western Anatolian regions of Turkey.…”

Modeling Resilience and Sustainability in Ancient Agricultural Systems

“…Available data indicate relative aridity during the Iron Age and Hellenistic periods across the eastern Mediterranean, albeit with substantial local climatic variation in the intensity and timing of climatic shifts (Allcock 2013;Kuzucuog lu et al 2011;Wick et al 2003). Humid conditions began in the Roman period and appear to have continued through roughly 1400 CE, after occupation had ended at Gordion (Bakker et al 2012;Dean et al 2013;Jones et al 2006;Kuzucuog lu et al 2011;Woodbridge and Roberts 2011).…”