Modeling the global emission, transport and deposition of trace elements associated with mineral dust

Abstract

Abstract. Trace element deposition from desert dust has important impacts on ocean primary productivity. In this study, emission inventories for 8 elements, which are primarily of soil origin, Mg, P, Ca, Mn, Fe, K, Al, and Si were determined based on a global mineral dataset and a soils dataset. Datasets of elemental fractions were used to drive the desert dust model in the Community Earth System Model (CESM) in order to simulate the elemental concentrations of atmospheric dust. Spatial variability of mineral dust elemental fractions was evident on a global scale, particularly for Ca. Simulations of global variations in the Ca / Al ratio, which typically ranged from around 0.1 to 5.0 in soil sources, were consistent with observations, suggesting this ratio to be a good signature for dust source regions. The simulated variable fractions of chemical elements are sufficiently different that estimates of deposition should include elemental variations, especially for Ca, Al and Fe. The model results have been evaluated with observational elemental aerosol concentration data from desert regions and dust events in non-dust regions, providing insights into uncertainties in the modeling approach. The ratios between modeled and observed elemental fractions ranged from 0.7 to 1.6 except for 3.4 and 3.5 for Mg and Mn, respectivly. Using the soil data base improved the correspondence of the spatial hetereogeneity in the modeling of several elements (Ca, Al and Fe) compared to observations. Total and soluble dust associated element fluxes into different ocean basins and ice sheets regions have been estimated, based on the model results. Annual inputs of soluble Mg, P, Ca, Mn, Fe and K associated with dust using mineral dataset were 0.28 Tg, 16.89 Gg, 1.32 Tg, 22.84 Gg, 0.068 Tg, and 0.15 Tg to global oceans and ice sheets.

Spatial variability of ocean fertilizing nutrients in the dust‐emitting ephemeral river catchments of Namibia

“…Similarly, the bioavailable fractions of P (Mehlich P) and N (nitrate (NO 3 À ) and ammonium (NH 4 + )) were determined with the addition of total P (TP) and total N (TN) to consider relationships between the bioavailable and total portions of the P and N cycles. It is important to note that bioavailable nutrient concentrations measured in source sediments are considered conservative in comparison to deposition-captured sediment that has undergone atmospheric processing during aeolian transport, known to increase nutrient bioavailability (Nenes et al, 2011;Zhang et al, 2015).…”

Aerosol Deposition Impacts on Land and Ocean Carbon Cycles

“…The spatial distribution of different minerals and elements can be deduced from soil maps, limited soil elemental data, and from size distribution assumptions [95][96][97][98][99][100], and provide some increased ability in the simulation of fractional Fe, Al, and Ca in dust [101]. Previously, most studies assumed 3.5% of dust was iron with a mean dust solubility of 2% [5]; however, recent studies have highlighted the importance of the various chemical states of iron in dust minerals on the solubilization rate of iron [102][103][104][105]106••].…”

Enhancing weak transient signals in SEVIRI false color imagery: Application to dust source detection in southern Africa

“…This effort is part of a wider research program, the ongoing Dust Observations for Models project (DO4Models), aimed at improving dust emission schemes in regional climate models and comprising scientists from the UK and South Africa [e.g., Haustein et al, 2015]. Sources in southern Africa are potentially important in terms of their effects on regional terrestrial, oceanic, and polar biogeochemical cycles as well as in the context of regional weather and climate prediction [e.g., Tummon et al, 2010;Zhang et al, 2015]. Indeed, recent research suggests that the region may emit substantially more dust in the future under specific climate change scenarios [e.g., Bhattachan et al, 2012Bhattachan et al, , 2015.…”