Late Little Ice Age palaeoenvironmental records from the Anzali and Amirkola Lagoons (south Caspian Sea): Vegetation and sea level changes

This is a postprint version of the article. The official published article can be found from the link below - Copyright @ 2011 Elsevier Ltd.Two internationally important Ramsar lagoons on the south coast of the Caspian Sea (CS) have been studied by palynology on short sediment cores for palaeoenvironmental and palaeoclimatic investigations. The sites lie within a small area of very high precipitation in a region that is otherwise dry. Vegetation surveys and geomorphological investigations have been used to provide a background to a multidisciplinary interpretation of the two sequences covering the last four centuries. In the small lagoon of Amirkola, the dense alder forested wetland has been briefly disturbed by fire, followed by the expansion of rice paddies from AD1720 to 1800. On the contrary, the terrestrial vegetation reflecting the diversity of the Hyrcanian vegetation around the lagoon of Anzali remained fairly complacent over time. The dinocyst and non-pollen palynomorph assemblages, revealing changes that have occurred in water salinity and water levels, indicate a high stand during the late Little Ice Age (LIA), from AD < 1620 to 1800–1830. In Amirkola, the lagoon spit remained intact over time, whereas in Anzali it broke into barrier islands during the late LIA, which merged into a spit during the subsequent sea level drop. A high population density and infrastructure prevented renewed breaking up of the spit when sea level reached its maximum (AD1995). Similar to other sites in the region around the southern CS, these two lagoonal investigations indicate that the LIA had a higher sea level as a result of more rainfall in the drainage basin of the CS.The coring and the sedimentological analyses were funded by the Iranian National Institute for Oceanography in the framework of a research project entitled “Investigation of the Holocene sediment along the Iranian coast of Caspian Sea: central Guilan”. The radiocarbon date of core HCGL02 was funded by V. Andrieu (Europôle Méditerranéen de l'Arbois, France) and that of core HCGA04 by Brunel University

Indian summer monsoon variations could have affected the early Holocene woodland expansion in the Near East

Postglacial expansion of deciduous oak woodlands of the Zagros—Anti-Taurus Mountains, a major biome of the Near East, was delayed until the middle Holocene at ~6300 cal. yr BP. The current hypotheses explain this delay as a consequence of a regional aridity during the early Holocene, slow migration rates of forest trees, and/or a long history of land use and agro-pastoralism in this region. In the present paper, support is given to a hypothesis that suggests different precipitation seasonalities during the early Holocene compared with the late Holocene. The oak species of the Zagros—Anti-Taurus Mts, particularly Quercus brantii Lindl., are strongly dependent on spring precipitation for regeneration and are sensitive to a long dry season. Detailed analysis of modern atmospheric circulation patterns in SW Asia during the late spring suggests that the Indian Summer Monsoon (ISM) intensification can modify the amount of late spring and/or early summer rainfall in western/northwestern Iran and eastern Anatolia, which could in turn have controlled the development of the Zagros—Anti-Taurus deciduous oak woodlands. During the early Holocene, the northwestward shift of the Inter-Tropical Convergence Zone (ITCZ) could have displaced the subtropical anticyclonic belt or associated high pressure ridges to the northwest. The latter could, in turn, have prevented the southeastward penetration of low pressure systems originating from the North Atlantic and Black Sea regions. Such atmospheric configuration could have reduced or eliminated the spring precipitation creating a typical Mediterranean continental climate characterized by winter-dominated precipitation. This scenario highlights the complexity of biome response to climate system interactions in transitional climatic and biogeographical regions