Abstract
Abstract. We report a new fluid inclusion dataset from northeastern Libyan speleothem SC-06-01, which is the largest speleothem fluid inclusion dataset for North Africa to date. The stalagmite was sampled in Susah Cave, a low-altitude coastal site, in Cyrenaica, on the northern slope of the Jebel Al-Akhdar. Speleothem fluid inclusions from the latest Marine Isotope Stage (MIS) 4 and throughout MIS 3 (∼67 to ∼30 kyr BP) confirm the hypothesis that past humid periods in this region reflect westerly rainfall advected through the Atlantic storm track. However, most of this moisture was sourced from the western Mediterranean, with little direct admixture of water evaporated from the Atlantic. Moreover, we identify a second moisture source likely associated with enhanced convective rainfall within the eastern Mediterranean. The relative importance of the western and eastern moisture sources seems to differ between the humid phases recorded in SC-06-01. During humid phases forced by precession, fluid inclusions record compositions consistent with both sources, but the 52.5–50.5 kyr interval forced by obliquity reveals only a western source. This is a key result, showing that although the amount of atmospheric moisture advections changes, the structure of the atmospheric circulation over the Mediterranean does not fundamentally change during orbital cycles. Consequently, an arid belt must have been retained between the Intertropical Convergence Zone and the midlatitude winter storm corridor during MIS 3 pluvials.
Highlights
Atmospheric latent heat is a major component of global and regional climate energy budgets, and changes in its amount and distribution are key aspects of the climate system (Pascale et al, 2011)
We report a new fluid inclusion dataset from northeastern Libyan speleothem SC-06-01, which is the largest speleothem fluid inclusion dataset for North Africa to date
Petrographic analysis of the thick sections indicates that the distribution of fluid inclusions is highly variable, with macroscopically opaque “milky” calcite typical of rapidly growing intervals containing sometimes very abundant inclusions and the discoloured, translucent calcite of the slowly growing intervals being almost inclusion-free (Fig. 2)
Summary
Atmospheric latent heat is a major component of global and regional climate energy budgets, and changes in its amount and distribution are key aspects of the climate system (Pascale et al, 2011). Rainfall in semiarid regions is one of the key climate parameters that understanding future impact on human societies depends upon (IPCC, 2014), making constraining of midlatitude hydrology a globally significant research priority. These regions, have a sparse record of palaeoclimate due to typically poor preservation of surface sedimentary archives (Swezey, 2001). North Africa is a region that fully exhibits these limitations, and large areas present either no pre-Holocene record or else they present highly discontinuous deposits indicating major reorganisation of the hydroclimate, which are challenging to date (Armitage et al, 2007). North Africa fully exhibits the progress palaeoclimatologists have made in understanding continental hydrological change from its impact on the marine system; our understanding of past North African hydroclimate is disproportionately drawn from records from the Mediterranean Sea (Rohling et al, 2015) and the eastern central Atlantic (deMenocal et al, 2000; Adkins et al, 2006; Goldsmith et al, 2017)
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