Thirteen thousand years of southeastern Mediterranean climate variability inferred from an integrative planktic foraminiferal‐based approach

Abstract

Over the past 13 ka, the hydrology for the southeastern Mediterranean was mainly regulated by Nile River runoff, which in turn was controlled by climate forcing. Being affected by orbital forcing, and the position of the Intertropical Convergence Zone (ITCZ), planktic foraminiferal data (assemblages, stable isotopes, and size properties) indicate three major periods. (1) From 13.0 to 11.5 ka, the upper water column was well-mixed, cold, and productive. (2) From 11.5 to 6.4 ka, hydrology and foraminifers were affected by intensified monsoonal circulation. The enhanced size of Globigerinoides ruber is interpreted as a response to environmental stress caused by low-saline waters. (3) After 6.4 ka, the southward retreat of the ITCZ caused a decrease in freshwater discharge and hence a return to ecological equilibrium. A drop in foraminifer diversity from 2.9 to 1.1 ka was related to more arid conditions, and limited supply of nutrients from the Nile River. We suggest a link to a negative North Atlantic Oscillation (NAO) marking the Roman Humid Period in the western Mediterranean, and in anti-phase with the southeastern Mediterranean aridity. Because Nile River runoff exerted major control on surface hydrology, a connection to Indian and Pacific climate systems partially controlling precipitation over the Nile catchment area is hypothesized. From 1.1 to 0.54 ka, high foraminifer diversity indicates humid conditions synchronous to the Medieval Climate Anomaly under a positive NAO state. Over the past 0.54 ka encompassing the Little Ice Age, another arid period is indicated by a drop in foraminifer diversity.Riverine mud belt deposits capture short-term climate variability, bearing continuous and expanded sedimentary successions and retaining both continental and marine environmental signals at high resolution through high sedimentation rates. The range of temporal variability in these archives spans from decadal to millennial scales, MOJTAHID ET AL.

Suborbital Hydrological Variability Inferred From Coupled Benthic and Planktic Foraminiferal‐Based Proxies in the Southeastern Mediterranean During the Last 19 ka

“…The reappearance of U. peregrina together with the freshwater‐intolerant planktic taxon G. sacculifer during S1b indicates less severe environmental conditions compared to S1a as previously suggested by Hennekam et al () and Mojtahid et al (). Both planktic and benthic data indicate high river runoff, enhanced input of terrestrial organic matter, and overall low bottom oxygen conditions with intermittent reoxygenation events (Figure ).…”

“…Foraminiferal accumulation rate and diversity of core PS009PC. Foraminiferal accumulation rate (FAR, ind/cm 2 /ka) and Shannon ( H ) diversity index for both planktic (Mojtahid et al, ) and benthic foraminifera (this study). The reconstructed relative sea‐level curve (Fleming et al, ; Lambeck et al, ) is represented.…”

“…The red arrows mark the main features of the δ 13 C. (b) Relative abundances of U. peregrina and B. marginata from core PS009PC (this study). (c) Relative abundance of G. ruber and G. sacculifer from core PS009PC (Mojtahid et al, ). The main events and climate phases are reported similarly to Figure , and the three shaded time periods underline the Holocene dry episodes as discussed in the text.…”

“…The second and third periods coincide with the onset and the end of the RWP (Figure b). While this event is recorded in the North Atlantic and western Mediterranean as a more humid period (Cullen, ; Mojtahid et al, ), dry conditions seem to have prevailed in the eastern Mediterranean region (e.g., Avnaim‐Katav et al, ; Giamali et al, ; Mojtahid et al, ; Schilman, Bar‐Matthews, et al, ; Revel et al, ). In this area, this time period is also linked to a decrease in the Nile River flood discharges starting between 3.1 and 2.8 ka (Nicholson & Flohn, ; Woodward et al, ).…”

Assessing the composition of fragmented agglutinated foraminiferal assemblages in ancient sediments: comparison of counting and area-based methods in Famennian samples (Late Devonian)

“…In recent planktic foraminifera, some species grow larger when close to the ecological optimum of the species (Schmidt et al, 2003). Some others grow larger in unfavorable conditions, delaying reproduction and prolonging the ontogenetic life span (Mojtahid et al, 2015;Schiebel and Hemleben, 2017). Such intra-morphotype size variation has been suggested for benthic foraminifera as well (Kaminski and Kuhnt, 1995;Holcova, 2004;Holcova and Slavik, 2013).…”