• A personal note on IGBP and the social sciences


    Humans are an integral component of the Earth system as conceptualised by IGBP. João Morais recalls key milestones in IGBP’s engagement with the social sciences and offers some words of advice for Future Earth.
  • IGBP and Earth observation:
    a co-evolution


    The iconic images of Earth beamed back by the earliest spacecraft helped to galvanise interest in our planet’s environment. The subsequent evolution and development of satellites for Earth observation has been intricately linked with that of IGBP and other global-change research programmes, write Jack Kaye and Cat Downy .

Synthesis of iron fertilization experiments: From the iron age in the age of enlightenment

Journal of Geophysical Research (2005)
de Baar H J W, Boyd P W, Coale K H, Landry M R, Tsuda A, Assmy P, Bakker D C E, Bozec Y, Barber R T, Brzezinski M A, Buesseler K O, Boyé M, Croot P L, Gervais F, Gorbunov M Y, Harrison P J, Hiscock W T, Laan P, Lancelot C, Law C S, Levasseur M, Marchetti A, Millero F J, Nishioka J, Nojiri Y, van Oijen T, Riebesell U, Rijkenberg M J A, Saito H, Takeda S, Timmermans K R, Veldhuis M J W, Waite A M and Wong C-S (eds)
Doi: 10.1029/2004JC002601
Vol 110; Issue C9; pp. 1-24
Abstract

Comparison of eight iron experiments shows that maximum Chl a, the maximum DIC removal, and the overall DIC/ Fe efficiency all scale inversely with depth of the wind mixed layer (WML) defining the light environment. Moreover, lateral patch dilution, sea surface irradiance, temperature, and grazing play additional roles. The Southern Ocean experiments were most influenced by very deep WMLs. In contrast, light conditions were most favorable during SEEDS and SERIES as well as during IronEx-2. The two extreme experiments, EisenEx and SEEDS, can be linked via EisenEx bottle incubations with shallower simulated WML depth. Large diatoms always benefit the most from Fe addition, where a remarkably small group of thriving diatom species is dominated by universal response of Pseudo-nitzschia spp. Significant response of these moderate 10 - 30 mu m), medium 30 - 60 mu m), and large 60 mu m) diatoms is consistent with growth physiology determined for single species in natural seawater. The minimum level of "dissolved'' Fe filtrate < 0.2 mu m) maintained during an experiment determines the dominant diatom size class. However, this is further complicated by continuous transfer of original truly dissolved reduced Fe(II) into the colloidal pool, which may constitute some 75% of the "dissolved'' pool. Depth integration of carbon inventory changes partly compensates the adverse effects of a deep WML due to its greater integration depths, decreasing the differences in responses between the eight experiments. About half of depth-integrated overall primary productivity is reflected in a decrease of DIC. The overall C/Fe efficiency of DIC uptake is DIC/Fe similar to 5600 for all eight experiments. The increase of particulate organic carbon is about a quarter of the primary production, suggesting food web losses for the other three quarters. Replenishment of DIC by air/sea exchange tends to be a minor few percent of primary CO2 fixation but will continue well after observations have stopped. Export of carbon into deeper waters is difficult to assess and is until now firmly proven and quite modest in only two experiments.

Share this page
Tell a friend (opens in new window)
Follow us

Please note!

IGBP closed at the end of 2015. This website is no longer updated.

No events available

  • Global Change Magazine No. 84


    This final issue of the magazine takes stock of IGBP’s scientific and institutional accomplishments as well as its contributions to policy and capacity building. It features interviews of several past...

  • Global Change Magazine No. 83


    This issue features a special section on carbon. You can read about peak greenhouse-gas emissions in China, the mitigation of black carbon emissions and the effect of the 2010-2011 La Niña event on gl...
RECOMMENDED