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

[摘要] Trace element deposition from desert dust has importantimpacts on ocean primary productivity, the quantification of which could beuseful in determining the magnitude and sign of the biogeochemical feedbackon radiative forcing. However, the impact of elemental deposition to remoteocean regions is not well understood and is not currently included in globalclimate models. In this study, emission inventories for eight elementsprimarily of soil origin, Mg, P, Ca, Mn, Fe, K, Al, and Si are determinedbased on a global mineral data set and a soil data set. The resultingelemental fractions are used to drive the desert dust model in the CommunityEarth System Model (CESM) in order to simulate the elemental concentrationsof atmospheric dust. Spatial variability of mineral dust elemental fractionsis evident on a global scale, particularly for Ca. Simulations of globalvariations in the Ca / Al ratio, which typically range from around 0.1 to 5.0in soils, are consistent with observations, suggesting that this ratio is agood signature for dust source regions. The simulated variable fractions ofchemical elements are sufficiently different; estimates of deposition shouldinclude elemental variations, especially for Ca, Al and Fe. The modelresults have been evaluated with observations of elemental aerosolconcentrations from desert regions and dust events in non-dust regions,providing insights into uncertainties in the modeling approach. The ratiosbetween modeled and observed elemental fractions range from 0.7 to 1.6,except for Mg and Mn (3.4 and 3.5, respectively). Using the soil databaseimproves the correspondence of the spatial heterogeneity in the modeling ofseveral elements (Ca, Al and Fe) compared to observations. Total and solubledust element fluxes to different ocean basins and ice sheet regions havebeen estimated, based on the model results. The annual inputs of soluble Mg, P,Ca, Mn, Fe and K associated with dust using the mineral data set are 0.30 Tg,16.89 Gg, 1.32 Tg, 22.84 Gg, 0.068 Tg, and 0.15 Tg to global oceans and icesheets.

[学科分类] 地球化学与岩石