Past Project: Collaborative Research Center 754 

“Climate-Biogeochemistry Interactions in the Tropical Ocean”

The Collaborative Research Center (SFB 754) addresses the relatively newly recognized threat of ocean deoxygenation, its possible impact on tropical oxygen minimum zones and implications for the global climate-biogeochemistry system. The overall goal of the SFB 754 is to improve understanding of the coupling of tropical climate variability and circulation with the ocean’s oxygen and nutrient balance, to quantitatively evaluate the nature of oxygen-sensitive tipping points, as well as to assess consequences for the Ocean’s future.

The key questions of the SFB 754 are:

  • How does subsurface dissolved oxygen in the tropical ocean respond to variability in ocean circulation and ventilation?
  • What are the sensitivities and feedbacks linking low or variable oxygen levels and key nutrient source and sink mechanisms? In the benthos? In the water column?
  • What are the magnitudes and time scales of past, present and likely future variations in oceanic oxygen and nutrient levels? On the regional scale? On the global scale?

The Collaborative Research Centre 754 (SFB 754) “Climate-Biogeochemistry Interactions in the Tropical Ocean” is funded by the German Research Foundation (DFG) since 2008. This project involves scientists from the Christian-Albrechts University Kiel (CAU), GEOMAR Helmholtz Center for Ocean Research Kiel and the Max-Planck-Institute Bremen.


My Project Involvement

in Thematic Area A: “circulation & oxygen
A6 Influence of centennial to millennial scale climate change on low-latitude oxygen minimum conditions
We study how the Oxygen Minimum Zone (OMZ) in the Eastern Tropical South Pacific functioned under significantly different climatic conditions from the last Glacial to the pre-anthropogenic Late Holocene in order to evaluate human-induced perturbations. The main goal is to decipher continent–ocean–atmosphere interactions that have controlled the OMZ. Therefore the natural variability in upper and subsurface ocean circulation and its impact on biogeochemical cycling are reconstructed at centennial to millennial resolution by using established and new proxies.

my research question:

Phase II 2012-2015:

The main goal of the DFG funded Collaborative Research Centre SFB 754 is to investigate changes in supply and consumption of oxygen in the oxygen-depleted tropical oceanic areas in past, present and future climates. Oxygen distribution in the global ocean is controlled by a close interplay of climate dynamics (e.g. atmospheric exchanges, oceanic ventilation) and oceanic biochemistry (e.g. PP and organic matter degradation due to bacterial activity). Along the Peruvian margin, changes in the surface hydrology originate from either local wind-driven upwelling or from the Pacific basin-scale circulation changes. The PP at the sea surface is directly linked to the upwelling-driven nutrient input.

            The aim of this thesis is to improve the understanding of present and past d30Sicompositions of diatoms by the measurements of d30Si of different size fractions of diatoms. Additionally, the influence of the recent observations of species-dependent isotope fractionation on present and past d30Sisignatures off Peru is investigated by determination of the associated diatom assemblages. The main goal is to apply d30Sias means of Si(OH)4 utilization reconstructions for sediments along the Peruvian margin in order to improve our understanding of the coupling of the local silicon cycle to larger scale variations in the biogeochemical properties of the Eastern Equatorial South Pacific since the Last Glacial Maximum.      Furthermore, diatom-bound nitrogen isotope compositions are measured to verify the fidelity of bulk sediment nitrogen isotope records at the Peruvian margin. Given that d30Si and d15Ndb measurements can be conducted on the same sample material, the latter is also applied to provide a better a better understanding of the coupling of the silicon and nitrogen cycling within the Peruvian coastal upwelling area of the past 20,000 years

Phase III 2017-18:

press release:

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