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 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.
Highlights
Iron (Fe) is one of the nutrient elements needed by phytoplankton to carry out photosynthesis
Patagonian dust plumes have been suggested to travel at low altitudes over the South Atlantic Ocean (SAO) and are accompanied by large amounts of cloud cover (Gassoand Stein, 2007; Li et al, 2008; Krinner et al, 2010), making it difficult to be detected by satellites
On 23 January 2009 and 17 February 2009 clear images of mineral dust transport were captured by Aqua MODIS allowing for the rare opportunity to carry out model analysis of dust transport for episodes with visual confirmation of mineral dust advection from the South American continent
Summary
Iron (Fe) is one of the nutrient elements needed by phytoplankton to carry out photosynthesis. Despite being the fourth most abundant element in the Earth’s crust, Fe is in a short supply in most near-surface remote oceanic waters. There are three main HNLC regions (subarctic north Pacific, east equatorial Pacific, and the Southern Ocean), with the Southern Ocean (SO) suggested to be the most biogeochemically significant due to its large spatial extent and considerable influence on the global carbon cycle (Martin, 1990; Watson et al, 2000; Boyd et al, 2000; Sarmiento et al, 2004). S. Johnson et al.: Understanding the transport of Patagonian dust and its influence on marine biological activity on the dynamics of plankton blooms, which in turn affect the biogeochemical cycles of carbon, nitrogen, silicon, sulfur, and influences the Earth’s climate system (e.g., Boyd et al, 2007)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
