Late Holocene Hydro-Climate Variability in the Eastern Mediterranean: A Spatial Multi-Proxy Approach

A total of thirteen (13) paleoclimatic coastal and hinterland archives of the broader eastern Mediterranean region were collected and examined statistically in search of underlying trends for the period 2800 to 200 BP. For each archive, a proxy record representative of hydro-climatic changes was selected, normalized using z-factors to facilitate intercomparison, and analyzed statistically. Multivariate statistical analysis was performed using a clustering analysis (HCA) and dimension reduction (PCA), which led to groupings of similar records temporally, and allowed the identification of spatially underlying modes of variability. Two main modes of variability were identified, further supporting complex trajectories of paleoclimatic evolution in the region. The first mode was identified for sites presenting a trend from a wetter to an overall drier phase, with respective changes at major phase shifts at 1400 BP and 1100 BP. All sites were from the southern and northern Balkan region, as well as southwestern Turkey. A contrasting dry to wet trend was identified for a site in the Peloponnese (Greece) and the Levant, with a major phase shift at around 750 BP. The inclusion of different proxies from very different environmental settings and the 200-year window has complicated the connection of established short-term climatic events to the study’s findings.

A 18,000 yr record of tropical land temperature, convective activity and rainfall seasonality from the maritime continent

The maritime continent exports an enormous amount of (latent) heat and moisture to the rest of the globe via deep atmospheric convection. How this export has changed through time under evolving boundary conditions, including the inundation of former Sundaland, is critical for the understanding of global climate dynamics. Given its size, relatively few high-resolution and continuous records exist of past hydroclimate, while terrestrial paleotemperature records are still completely absent from the region. In this study we present a 18,000-year multi-proxy record obtained from a lake sediment at the NW corner of former Sundaland. We found that rainfall seasonality was very important over the entire deglacial period, evidenced by biomass burning and C4 vegetation, despite rising atmospheric CO2 levels and increasing humidity that normally promotes C3 rainforests. The strong seasonality was reduced only upon ongoing inundation of Sundaland, with a clear inflection point around the Older Dryas event (13.8 ka BP), indicating a distinct system change. Land temperatures during the last stadial periods were 5°C colder than today’s 27°C. Temperatures rose gradually during the early Holocene to reach 29°C between 7-2 ka BP, accompanied by increasing convection, both driven by insolation power during the wet season. Convection decreased with lowering wet-season (autumn) insolation during the Meghalayan period, concurrent with the known increase of ENSO variability and Northern Hemisphere climate cooling and drying. Our results provide further insight in the role of Sundaland - turned maritime continent for the global climate system in response to sea level rise and orbital forcing.

Neogene hyperaridity in Arabia drove the directions of mammalian dispersal between Africa and Eurasia

The evolution of the present-day African savannah fauna has been substantially influenced by the dispersal of Eurasian ancestors into Africa. The ancestors evolved endemically, together with the autochthonous taxa, into extant Afrotropical clades during the last 5 million years. However, it is unclear why Eurasian ancestors moved into Africa. Here we use sedimentological observations and soluble salt geochemical analyses of samples from a sedimentary sequence in Western Iran to develop a 10-million-year long proxy record of Arabian climate. We identify transient periods of Arabian hyperaridity centred 8.75, 7.78, 7.50 and 6.25 million years ago, out-of-phase with Northern African aridity. We propose that this relationship promoted unidirectional mammalian dispersals into Africa. This was followed by a sustained hyperarid period between 5.6 and 3.3 million years ago which impeded dispersals and allowed African mammalian faunas to endemically diversify into present-day clades. After this, the mid-Piacenzian warmth enabled bi-directional fauna exchange between Africa and Eurasia, which continued during the Pleistocene.