Proposed changes in seasonality of climate during the Lateglacial and Holocene at Lake Zeribar, Iran

Abstract

Calcareous sediments spanning the last 13 ka fromn I,ake Zeribar, western Iran, were sampled for stable-isotope analysis as a means of augmenting earlier climatic interpretations based on polleni and macrofossils. The Lateglacial period was cold and dry, suLpporting semi-desert vegetation and highly concentrated lake water. Low evaporation rates due to the cold resulted in long residenice times and high lake stands. Durinig the earlv Holocene, the upland vegetation changed to a pistachio-oak savanna as low temperatures and ariditv J ameliorated. Lake level dropped in response to increased evapotranspiration. The low oxygen-isotope values of lacustiine calcite during this period are interpi-eted as a relative increase in the contributioni of winiter moisture rather than overall changes in effective moistuLre. A gradual increase in oak pollen at 7 ka BP signalled the inicrease in effective moisture to levels simiiilar to those of today. At the same tinme the 5`1O values increased.A reflecting a greater percentage of "0-enriched spring rains. Modern values and seasonal distribution of precipi-HOLOCENE tation were established by 6 ka BP. A short-lived return to winter-only precipitation occuiTed at 4.5 ka BP SPECIAL ISSUE and resulted in a temporary increase in anrdity. The covariance among 6'3C, carbonate deposition and 6S'O values suggests that lake productivity is linked to these seasonal climiiatic changes.

Interpreting lake isotope records of Holocene environmental change in the Eastern Mediterranean

“…These values are significantly higher than the range of precipitation values specified by Stevens et al (2001) i.e. -10 to -14‰ for Zeribar.…”

“…Periods of net water loss , 1997) showed that relative humidity was an important driver of P:E (specifically E) and suggested that the  18 O c record could be used to quantitatively reconstruct relative humidity through time. Stevens et al (2001) interpreted changes through the Holocene part of the Zeribar  18 O c record as due to changes in the predominant seasonality of rainfall at the site. They showed that increases in the percentage of precipitation falling in the winter months would lead to more negative isotope values of the annual weighted precipitation.…”

Hydrological variability in the Northern Levant: a 250 ka multi-proxy record from the Yammoûneh (Lebanon) sedimentary sequence

“…During interglacial peaks, maximum tree pollen percentages reflect warm conditions and higher precipitation from the mid-latitude westerly system. Changes in seasonality were proposed by several authors to explain Holocene climate in the region (Stevens et al, 2001(Stevens et al, , 2006Magny, 2007;Tzedakis, 2007;Peyron et al, 2010;Djamali et al, 2010). At Yammoûneh, sharp δ c increases in phase with arboreal pollen peaks, attributed to enhanced seasonal thermal and hydrological contrasts, suggest that the hypothesis of seasonal changes is valid for older interglacial stages (e.g., MIS 5.5 and MIS 5.1).…”

“…1; Eastwood et al, 2007), or changes in precipitation seasonality (at Lakes Zeribar and Mirabad, NW Iran, Fig. 1; Stevens et al, 2001Stevens et al, , 2006). As discussed above from both pollen and isotope data, we favour the hypothesis of seasonal increased hydrological and thermal contrasts with wet cool winters, possibly a longer rainy season, and very dry warm summers generating strong evaporative effects in both the drainage area and the waterbody.…”

Testate amoebae as palaeohydrological proxies in sürmene ağaçbaşi yaylasi peatland (northeast Turkey)

“…However, longer-term reconstructions of climate change in the Holocene are of limited number and are spatially and temporally restricted (Bar-Matthews et al 1998, Goodfriend 1999, Schilman et al 2001, Stevens et al 2001, Roberts et al 2001, Kashima 2002, Wick et al 2003, Jones et al 2005, Eastwood et al 2007). Due to generally unfavourable climatic conditions for peat formation and human destruction of mires, Turkish peatlands are rare, covering perhaps 30 Km 2 (Çayci et al 1988(Çayci et al , Őz 1996(Çayci et al , Byfield and Őzhatay 1997.…”