Climate of the Past Discussions www.clim-past-discuss.net 1814-9340 1814-9359 2 3 2006 10.5194/cpd-2-233-2006 http://www.clim-past-discuss.net/2/233/2006/ http://www.clim-past-discuss.net/2/233/2006/cpd-2-233-2006.html http://www.clim-past-discuss.net/2/233/2006/cpd-2-233-2006.pdf 233 265 2006-06-08 Biogeochemical records of past global iron connections Z. S. An J. J. Cao K. K. Anderson H. Kawahata R. Arimoto State Key Lab of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, P.O. Box 17, Xi’an 710075, China Niels Bohr Institute for Astronomy, Physics and Geophysics, University of Copenhagen, Denmark DK-2100 Copenhagen Denmark Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST) Tsukuba-higashi 1-1-1, Ibaraki 305–8567, Japan Carlsbad Environmental Monitoring and Research Center, New Mexico State University, 1400 University Drive, Carlsbad, NM 88220, USA Paleorecords of dust deposition can be used to evaluate global iron connections under conditions different from those today. Dust production and deposition has co-varied with ocean paleoproductivity, <i>p</i>CO₂, and climate over glacial-interglacial cycles, and in this paper we review the current understanding and highlight research needs with respect to paleorecords of global iron connections. These records, which include data from terrestrial (loess) deposits, marine sediments, and ice cores, suggest that average eolian deposition rates were approximately 2&ndash;20 times higher during glacial periods than during interglacials. Enhanced dust fluxes to the oceans during glacial times, particularly to the main high-nutrient/low-chlorophyll (HNLC) areas of the open ocean (i.e., the Pacific subarctic, the equatorial Pacific, and the Southern Ocean), may have "fertilized" marine biota, thereby enhancing ocean productivity (1&ndash;2 fold) and driving atmospheric CO₂ lower. Current models yield variable results, however, with glacial-interglacial changes in dust fluxes changing atmospheric <i>p</i>CO₂ by the equivalent of 5 to &gt;50% of the total glacial-interglacial change of 80&ndash;100 ppm. Positive correlations among Asian dust, ocean productivity and atmospheric CO₂ in last 130 kyr, 1200 yr and 50 yr indicate that eolian iron has played an important role in global biogeochemical cycles of the past. A simple calculation suggests that one-tenth to one-third of the global change in CO₂ due to dust-supplied Fe could be ascribed to variations in the dust supply flux from Asia and its associated effects on productivity in the Pacific Ocean.