Dust fertilization of biological productivity in the Subarctic North Pacific during the last 150 kyr
Abstract
The Subarctic North Pacific (SNP) is one of three principal High Nutrient Low Chlorophyll regions of the modern ocean characterized by an excess pool of macronutrients not completely consumed during the annual biogeochemical cycle. In the last 25 years, a number of studies from the SNP have proposed that eolian dust input of iron from East Asian arid regions is the major limiting factor for primary and export production. In recent years, additional iron sources have been suggested for regulating phytoplankton growth in the SNP, including mobilized continental margin material, ice-rafted debris, volcanic material, turbulent mixing and upwelling. We will present results of a multi-proxy approach from INOPEX core SO202-7-6 and ODP site 882 from the Detroit Seamount in the northwest SNP covering the last 30 and 150 kyr, respectively. We will compare 230Th-normalized dust flux records based on 4He, 232Th and REE, grain size distributions and 230Th-normalized fluxes of opal, total organic carbon, carbonate and biogenic barium and Pa/Th ratios as productivity proxies for INOPEX core SO202-7-6. A new high resolution record of dust fluxes based on 4He will be compared with published productivity proxy records from ODP site 882. A spatial survey of core-top sediments covering the whole SNP indicates that the efficiency of diatom export out of the euphotic zone, as defined by the ratio of opal flux in the core-top sediments to the maximum annual surface water silicate concentration during the winter months, is positively correlated with dust fluxes, possibly as a result of either dust fertilization of primary production or a diatom ballasting effect by dust particles. Preliminary results from INOPEX core SO202-7-6, on the other hand, indicate no correlation between dust flux and biological productivity during the last deglaciation. We will discuss possible explanations for these observations to answer the question if the dust fertilization hypothesis proposed by John Martin and colleagues [1] holds true for the present as well as the past in the SNP. [1] J.H. Martin, S.E. Fitzwater, Nature 331, 341-343 (1988); J.H. Martin, R.M. Gordon, DSR 35(2), 177-196 (1988); J.H. Martin et al., DSR 36(5), 649-680 (1989).
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMPP13A2066S
- Keywords:
-
- 4901 PALEOCEANOGRAPHY / Abrupt/rapid climate change;
- 4912 PALEOCEANOGRAPHY / Biogeochemical cycles;
- processes;
- and modeling;
- 4924 PALEOCEANOGRAPHY / Geochemical tracers;
- 9355 GEOGRAPHIC LOCATION / Pacific Ocean