The link between marine sediment records and changes in Holocene Saharan landscape: simulating the dust cycle

Abstract

Abstract. Marine sediment records reveal an abrupt and strong increase in dust deposition in the North Atlantic at the end of the African Humid Period about 4.9 to 5.5 ka ago. The change in dust flux has been attributed to varying Saharan land surface cover. Alternatively, the enhanced dust accumulation is linked to enhanced surface winds and a consequent intensification of coastal upwelling. Here we demonstrate for the first time the direct link between dust accumulation in marine cores and changes in Saharan land surface. We simulate the mid-Holocene (6 ka BP) and preindustrial (1850 AD) dust cycle as a function of Saharan land surface cover and atmosphere-ocean conditions using the coupled atmosphere-aerosol model ECHAM6.1-HAM2.1. Mid-Holocene surface characteristics, including vegetation cover and lake surface area, are derived from proxy data and simulations. In agreement with data from marine sediment cores, our simulations show that mid-Holocene dust deposition fluxes in the North Atlantic were two to three times lower compared with pre-industrial fluxes. We identify Saharan land surface characteristics to be the main control on dust transport from North Africa to the North Atlantic. We conclude that the increase in dust accumulation in marine cores is directly linked to a transition of the Saharan landscape during the Holocene and not due to changes in atmospheric or ocean conditions alone.

Periodic input of dust over the Eastern Carpathians during the Holocene linked with Saharan desertification and human impact

“…3). This period is the first indication of the impact the Mediterranean climate and movement of the ITCZ has had on the Carpathian-Balkan region (as simulated by Egerer et al, 2016, andBoos andKorty, 2016). Indeed, intermittent intrusions of Saharan dust over the Carpathian area have been well documented both through direct observations (Labzovskii et al, 2014;Varga et al, 2013) and through provenance studies of past Saharan dust contribution within interglacial soils in the region (Varga et al, 2016).…”

Glacial to Holocene changes in trans-Atlantic Saharan dust transport and dust-climate feedbacks

“…As one example of such an interaction, insolation-related decreases in cloud cover over the TNA would increase the impact of changes in dust loading on SSTs. Of particular importance will be simulations with prognostic dust emissions, allowing inclusion of dust’s emission, transport, deposition, and radiative impacts in a self-consistent framework ( 23 , 71 , 72 ). These simulations have the potential to capture feedbacks of SSTs on dust emissions suggested by our results but will require additional work to improve representations of North African source areas ( 52 , 73 ) and depositional processes ( 36 ).…”

Modulation of Mid‐Holocene African Rainfall by Dust Aerosol Direct and Indirect Effects

“…During the AHP, vegetation in the Sahara resulted in dust aerosol emissions two to three times lower than today (deMenocal et al, 2000;Egerer et al, 2016;McGee et al, 2013). During the AHP, vegetation in the Sahara resulted in dust aerosol emissions two to three times lower than today (deMenocal et al, 2000;Egerer et al, 2016;McGee et al, 2013).…”

“…Vegetation also indirectly impacts northern African climate through its control on dust mobilization. During the AHP, vegetation in the Sahara resulted in dust aerosol emissions two to three times lower than today (deMenocal et al, 2000;Egerer et al, 2016;McGee et al, 2013). This decrease in dust is postulated to have impacted AHP precipitation through direct, indirect, and semidirect dust aerosol effects (Pausata et al, 2016;Perlwitz & Miller, 2010;Williams et al, 2016).…”