Understanding the transport of Patagonian dust and its influence on marine biological activity in the South Atlantic Ocean

Abstract

Abstract. The supply of bioavailable iron to the high-nitrate low-chlorophyll (HNLC) waters of the Southern Ocean through atmospheric pathways could stimulate phytoplankton blooms and have major implications for the global carbon cycle. In this study, model results and remotely-sensed data are analyzed to examine the horizontal and vertical transport pathways of Patagonian dust and quantify the effect of iron-laden mineral dust deposition on marine biological productivity in the surface waters of the South Atlantic Ocean (SAO). Model simulations for the atmospheric transport and deposition of mineral dust and bioavailable iron are carried out for two large dust outbreaks originated at the source regions of northern Patagonia during the austral summer of 2009. Model-simulated horizontal and vertical transport pathways of Patagonian dust plumes are in reasonable agreement with remotely-sensed data. Simulations indicate that the synoptic meteorological patterns of high and low pressure systems are largely accountable for dust transport trajectories over the SAO. According to model results and retrievals from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), synoptic flows caused by opposing pressure systems (a high pressure system located to the east or north-east of a low pressure system) elevate the South American dust plumes well above the marine boundary layer. Under such conditions, the bulk concentration of mineral dust can quickly be transported around the low pressure system in a clockwise manner, follow the southeasterly advection pathway, and reach the HNLC waters of the SAO and Antarctica in ∼3-4 days after emission from the source regions of northern Patagonia. Two different mechanisms for dust-iron mobilization into a bioavailable form are considered in this study. A global 3-D chemical transport model (GEOS-Chem), implemented with an iron dissolution Correspondence to: N. Meskhidze (nmeskhidze@ncsu.edu) scheme, is employed to estimate the atmospheric fluxes of soluble iron, while a dust/biota assessment tool (Boyd et al., 2010) is applied to evaluate the amount of bioavailable iron formed through the slow and sustained leaching of dust in the ocean mixed layer. The effect of iron-laden mineral dust supply on surface ocean biomass is investigated by comparing predicted surface chlorophyll-a concentration ([Chl-a]) to remotely-sensed data. As the dust transport episodes examined here represent large summertime outflows of mineral dust from South American continental sources, this study suggests that (1) atmospheric fluxes of mineral dust from Patagonia are not likely to be the major source of bioavailable iron to ocean regions characterized by high primary productivity; (2) even if Patagonian dust plumes may not cause visible algae blooms, they could still influence background [Chl-a] in the South Atlantic sector of the Southern Ocean.

Mercury presence and speciation in the South Atlantic Ocean along the 40°S transect

“…At the time of GA10 cruise the Copahue volcano was active at the Chile‐Argentinean border in the Andes and was emitting soot and dust particles, which were transported eastward over the South Atlantic Ocean together with the Patagonian dust plume [ Johnson et al , ]. Sea surface THg distribution, however, did not show elevated values neither in the eastern or western basin, where the particles are thought to have deposited (Figure ).…”

Modeling a typical winter-time dust event over the Arabian Peninsula and the Red Sea

“…It directly affects the earth's energy budget (Ackermann and Chung, 1992;Seinfeld et al, 2004;Ge et al, 2010;Zhao et al, 2011) by scattering and absorbing radiation; it indirectly affects the energy budget by modifying the microphysics of the clouds (Satheesh and Moorthy, 2005;Haywood and Boucher, 2000). Mineral dust makes important contributions to the fertilization of phytoplankton through ocean deposition and thus to carbon dioxide levels in the atmosphere (Watson et al, 2000;Johnson et al, 2011). Additionally, dust has substantial impacts on the hydrological cycle Zhao et al, 2011Zhao et al, , 2012 and many biogeochemical cycles by providing reaction sites and carrying many condensed and absorbed species (Dentener et al, 1996;Huebert et al, 2003).…”

Contemporary glacigenic inputs to the dust cycle

“…To date, the vast majority of aeolian research has focused on these prominent global dust sources in the tropics and mid-latitudes. Notably, modern dust emissions in high latitudes are not confined to arid regions and can occur in relatively humid areas of Alaska ), New Zealand (McGowan et al, 1996McGowan and Sturman, 1997), Patagonia (Gassó et al, 2010;Johnson et al, 2011), Iceland (Arnalds, 2010;Prospero et al, 2012) and Greenland (Bullard and Austin, 2011). Contemporary glacigenic dust sources are typically associated with cold climates and are primarily, but not exclusively, located at high latitudes.…”