Connection between South Mediterranean climate and North African atmospheric circulation during the last 50,000yrBP North Atlantic cold events

Abstract

High-resolution clay mineralogical analyses were performed on sediment deposited during the last 50,000 yr in the Alboran sea (ODP Site 976). The clay mineral record is compared with pollen assemblages and with annual precipitation (Pann) and mean temperatures of the coldest month (MTCO) reconstructed with the modern analog technique (MAT). Enhanced contribution of palygorskite, a typical wind-blown clay mineral, characterizes the North Atlantic cold climatic events. Coeval development of the semi-arid vegetation (Artemisia rich) associated with a drastic fall of reconstructed precipitations and temperatures, suggest cold and arid continental conditions in the West Mediterranean area during North Atlantic cold events. The clay mineral association, especially the palygorskite content and the illite-to-kaolinite ratio, indicate western Morocco as one of the major source of the clay-size fraction during the North Atlantic cold events. The maximum abundance of Artemisia associated with the presence of Argania pollen both indicate Morocco as the main origin for pollen during these cold periods. The comparison of these pollen and clay mineralspecific features allows us to pinpoint western Morocco as the dominant source of wind-blown particles during North Atlantic cold events. These specific mineralogical composition and palynological assemblages reveal enhanced aridity over North Africa and intensification of winds favouring dust erosion and transport from North Africa toward the Alboran Sea during the North Atlantic cold events. According to atmospheric models, such a meridian transport (1) likely results from the development of strong and stable anticyclonic conditions over the tropical Atlantic and North Africa, similar to today's summer meteorological configuration and (2) implies a northward position of the westerly winds during North Atlantic cold events. Finally the synoptic situation over the West Mediterranean during the North Atlantic cold events is compared with the North Atlantic Oscillation (NAO), suggesting that during the cold Atlantic events, weather regimes over Europe and North Africa may have been systematically shifted towards a positive NAO situation.

Potential for a New Multimillennial Tree-Ring Chronology from Subfossil Balkan River Oaks

“…The approximate dates provided for the groups so far, in particular the two largest groups, 1 and 3, correlate broadly with some significant time periods in terms of human and environmental interactions in the wider region, which in turn are argued by many researchers to link with a range of increasingly recognized periods of abrupt climatic change (e.g. Bond et al 1997;Bianchi and McCave 1999;Hu et al 1999;Magny et al 2003;Mayewski et al 2004;Bout-Roumazeilles et al 2007) on a global to hemispheric scale.…”

Climate and cave control on Pleistocene/Holocene calcite-to-aragonite transitions in speleothems from Morocco: Elemental and isotopic evidence

“…The age model of the Lake Ifrah record does not allow for a comparison of the age of aragonite layers with the marine isotope stage 2 and 3 climate reconstruction in Morocco. Heinrich event 2 (H2) was recorded by several marine cores surrounding the Iberian Peninsula and Morocco (Turon et al, 2003;Bout-Roumazeilles et al, 2007;Fletcher and Goni, 2008;Nebout et al, 2009;Penaud et al, 2010). Fletcher and Goni (2008) and Nebout et al (2009) suggested that H2 was characterized by overall dry conditions in the Western Mediterranean.…”

The meridional temperature gradient in the eastern North Atlantic during MIS 11 and its link to the ocean–atmosphere system

“…Although meteorological observational data allow investigation of NAO regularities only for the last 150 years, computer simulations have already indicated the existance of changes of NAO indices at least on multi-centennial time scales (Semenov et al, 2008). Moreover, paleoceanographical studies postulated a significant influence of the NAO on regional climate conditions for longer, suborbital to orbital timescales maintaining the analogy to the present-day conditions (Keigwin and Pickart, 1999;Rimbu et al, 2003;Felis et al, 2004;Kim et al, 2004;Bout-Roumazeilles et al, 2007). Following these ideas, we also refer to the modern general scheme of North Atlantic atmospheric circulation, assuming an existence of NAO-like oscillations during MIS 11c and using the modern scheme as a template in order to make some assumptions about ocean-atmospheric interaction during this period.…”