Atmospheric Input of Lithogenic Elements to the Sargasso Sea: the Long and Short of Bermuda Observations Book uri icon

abstract

  • Atmospheric deposition of dust is a primary delivery route for lithogenic elements such as iron, an essential micronutrient, to remote surface ocean waters. Data collected in the Bermuda region includes time series measurements of atmospheric aerosols and precipitation, extending back over several decades. These records include both continuous and weekly samples over many yearly periods. This began with the pioneering work of Bob Duce during the 1970's prior to SEAREX, continuing into the 1980's with WATOX, into the 1990's under AEROCE, and even into the current millennium with NSF support. Simultaneous aerosol and precipitation collections allow, at times, estimates of the relative modes of dry and wet deposition to surface waters of the Sargasso Sea. These multi-decade records clearly demonstrate that the input of lithogenic elements to the Bermuda surface ocean is linked to synoptic meteorology. On intra-annual time scales, the records reveal the cyclic arrival of Saharan dust events that reoccur during the summer season. Included are those during 2004 that were remotely sampled using an autonomous aerosol sampler on the Bermuda Testbed Mooring, with faithful results. On inter-annual time scales, the North Atlantic Oscillation (NAO) index, appears to impact the positioning of the Bermuda-Azores high pressure system. The resulting effect is on the timing and magnitude of dust transport and deposition to the Bermuda region, as well as discriminating the regional dust source. Also affected is the relative proportion of dry versus wet deposition of iron, which at times appears to be equivalent, according to NAO intensity. More recent work in the Bermuda region indicates that the solubility of aerosol iron is strongly dependent on the source and/or transport history of mineral aerosols. Such long and short term information serves to improve our ability to predict how the ocean will respond to and modulate future climatic change; for example how changes in dust supply and transport might affect marine primary production and the associated abyssal fluxes of carbon and macronutrients.

publication date

  • October 2006