Estimating Mineral Dust Deposition to the Surface Ocean, a Comparison of Approaches
Abstract
The SEAREX network generated the first large scale spatial and temporal picture of aerosol characteristics in the Pacific Ocean. The detailed record from that sampling network and other stations in the Atlantic and Indian Oceans provided the data underpinnings for the first global view of mineral deposition to the ocean produced by Duce et al., in 1991. However, since the aerosol network required land-based sampling, oceanic depositions were, by necessity, extrapolations from the closest nearby land mass. In some regions of the open ocean lack of available sampling sites resulted in extensive regions with no direct data. The geochemical consequences of mineral dust deposition to the ocean are of interest to oceanographers for a variety of reasons ranging from pollutant transfer to geochemical inputs. The biogeochemical consequences of dust input have come increasingly to the fore through the realization that atmospheric transport of mineral dust to the remote ocean is a vector for the delivery of the biologically essential micronutrient Fe. Coupled biogeochemical models that attempt to address global C budgets now need to incorporate the systematics of Fe availability in ocean surface waters, because of its effect on the biological C pump. Fe bioavailability is a complex problem involving many phenomena that are currently poorly understood, such as aerosol solubility, ligand complexation and bioavailability of different Fe species. Fe bioavailability is a complex problem involving many phenomena that are currently poorly understood, such as aerosol solubility, ligand complexation and bioavailability of different Fe species. A key tractable parameter is the magnitude of mineral dust deposition to particular regions of the ocean. An alternative approach to estimating dust deposition has been to use dissolved Al concentrations in surface waters and the MADCOW model. Surface water dissolved Al data from 4 CLIVAR cruises and other projects now provide an opportunity to compare estimates of mineral deposition to large regions of the N. Atlantic and the Pacific oceans from this approach with those from the GESAMP model. Over most of the regions there is extremely good agreement within the mutual errors of the two approaches. Three regions however show poor agreement. In the NW Pacific, dissolved Al implies much lower deposition of Asian dust than the GESAMP model. In two other regions of the Pacific (completely devoid of sampling sites) the dissolved Al predicts regions of enhanced mineral deposition, that are presently not captured by existing models. The synergy of ground-truthed dissolved trace elements in concert with the island-based data sets will provide a global data set that will challenge modelers and improve global climate models.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFM.A42C..04M
- Keywords:
-
- 0312 Air/sea constituent fluxes (3339;
- 4504);
- 0330 Geochemical cycles (1030);
- 1615 Biogeochemical cycles;
- processes;
- and modeling (0412;
- 0414;
- 0793;
- 4805;
- 4805 Biogeochemical cycles;
- processes;
- and modeling (0412;
- 0414;
- 0793;
- 1615