The middle Holocene climatic records from Arabia: Reassessing lacustrine environments, shift of ITCZ in Arabian Sea, and impacts of the southwest Indian and African monsoons

Abstract

A dramatic increase in regional summer rainfall amount has been proposed for the Arabian Peninsula during the middle Holocene (ca. 9-5 ka BP) based on lacustrine sediments, inferred lake levels, speleothems, and pollen. This rainfall increase is considered primarily the result of an intensified Indian summer monsoon as part of the insolation-driven, northward shift of the boreal summer position of the Inter-Tropical Convergence Zone (ITCZ) to over the deserts of North Africa, Arabia, and northwest India.We examine the basis for the proposed drastic climate change in Arabia and the shifts in the summer monsoon rains, by reviewing paleohydrologic lacustrine records from Arabia. We evaluate and reinterpret individual lake-basin status regarding their lacustrine-like deposits, physiography, shorelines, fauna and flora, and conclude that these basins were not occupied by lakes, but by shallow marsh environments.Rainfall increase required to support such restricted wetlands is much smaller than needed to form and maintain highly evaporating lakes and we suggest that rainfall changes occurred primarily at the elevated edges of southwestern, southern, and southeastern Arabian Peninsula.These relatively small changes in rainfall amounts and local are also supported by pollen and speleothems from the region. The changes do not require a northward shift of the Northern Hemisphere summer ITCZ and intensification of the Indian monsoon rainfall. We propose that (a) latitudinal and slight inland impact expansion of the North African summer monsoon rains across the Red Sea, and (b) uplifted moist air of this monsoon to southwestern Arabia highlands, rather than rains associated with intensification of Indian summer monsoon, as proposed before, increased rains in that region; these African monsoon rains produced the modest paleo-wetlands in downstream hyperarid basins. Furthermore, we postulate that as in present-day, the ITCZ in A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT3Enzel, Kushnir, and Quade P.3 the Indian Ocean remained at or near the equator all year round, and the Indian summer monsoon, through dynamically induced air subsidence, can reduce rather than enhance summer rainfall in the Levant and neighboring deserts, including Arabia. Our summary suggests a widening to the north of the latitudinal range of the rainfall associated with the North African summer monsoon moisture crossing the Red Sea to the east. We discuss other mechanism that could have potentially contributed to the formation and maintaining of the modest paleowetlands.

Speleothems from the Middle East: An Example of Water Limited Environments in the SISAL Database

“…Achieving these goals will allow SISAL based studies could better constrain teleconnections amongst the hydroclimate of remote regions such as Northern Africa, the Levant and the FC, which should all be influenced by Mediterranean cyclones and ITCZ migration, as the spatial scale of the ITCZ migration and the overall effect it might have had on rainfall amount in the Southern AP is still debated [173] and a regional compilation incorporating crucial missing records to the SISAL database will enable us to shed light on this topic. Furthermore, considering the location of the Levant at the border between the tropical Hadley cell and the mid-latitude Ferrel cell, hydroclimate change in this region is supposed to be very sensitive to shifts in the Hadley-Ferrel-cell border, which should be ultimately imprinted in the speleothem palaeoclimate record.…”

A humid early Holocene in Yemen interpreted from palaeoecology and taxonomy of freshwater ostracods

“…The uppermost part of the sections reflects a period of strong aridity. Enzel et al (2015) regarded the sediment successions of as being wetland deposits.…”

“…Several studies such as de Menocal et al (2000), Mischke (2001), Engel et al (2012) and Enzel et al (2015) reported the wet period of the Holocene in a wider area including Arabia, Africa and Asia and discussed the solar cycle effects on Indian monsoon climate. Our record fits a moist period documented for the early to mid-Holocene (Fleitmann and Matter, 2009).…”

“…Some of these studies reported the distribution and development of Holocene palaeolakes in the Arabian Peninsula, where water availability is a challenge for the future (e.g. Acres, 1982;Wilkinson, 1997;Lézine et al, 1998;Fleitmann et al, 2003;Parker et al, 2006;Rosenberg et al, 2011;Engel et al, 2012;Enzel et al, 2015). Understanding changes in the moisture availability of the past is a prerequisite for a sustainable management of water resources.…”

Sediment-filled karst depressions and <i>riyad</i> – key archaeological environments of south Qatar

“…2). In order to reach the highest possible sensitivity, to realize a time-efficient prospection and to receive additional information on the enrichment of magnetic minerals in lateral sediment layers, we used the Cs total field magnetometer (Scintrex SM4G-Special) using the "duo-sensor" configuration (see examples in Fassbinder, 2015Fassbinder, , 2017. Five adjacent grids of 40 m × 40 m were prospected.…”