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Theme 2

Theme 2

Surface seawater pHT (from measured DIC and alkalinity) values and atmospheric CO2 concentrations. (Blue: typical values for glacial times; green: pre-industrial times, orange: present; red: predicted future values) (Schlitzer, 2000).

Sensitivity to Global Change

What are the responses of key marine biogeochemical cycles, ecosystems and their interactions to global change?

Summary

Theme 2 is the core of IMBER research. This includes investigations of how large-scale climate phenomena that alter the physical forcing on seasonal to inter-decadal time scales affect the ocean, and how these oceanic changes alter the temperature and light environment and distribution of carbon and nutrients in the upper ocean. It also considers how changes in pH and carbon system parameters alter biogeochemical cycles and ecosystems. Another challenge is to understand how global change affects the controls on biological growth (distributions of macro- and micronutrients, iron and other nutrients from continental sources). Investigation of the impact of fishing pressure on marine food webs and biogeochemical cycles will also be conducted. 

IMBER focuses on observation and analysis of current marine biogeochemical cycles and ecosystems and on understanding and predicting how these respond to the complex forcings associated with global change.

Key issues

Issue 2.1 Impacts of Climate-Induced Changes Through Physical Forcing and Variability

  • What are the impacts of changes in circulation, ventilation and stratification?
  • What are the direct effects of changes in ocean temperature and light environment?
  • What are the impacts of changes in the frequency and intensity of extreme and episodic events?

Issue 2.2 Effects of Increasing Anthropogenic CO2 and Changing pH on Marine Biogeochemical Cycles, Ecosystems and their Interactions

  • What are the effects of CO2-driven changes in carbonate chemistry?
  • What are the effects of pH-driven changes in nutrient and trace metal speciation?
  • Which organisms and biologial processes are most sensitive to pH and CO2 changes, what are the consequences and to what extent can organisms adapt in reponse to these changes?

Issue 2.3 Effects of Changing Supplies of Macro- and Micronutrients

  • How will changes in macro- and micronutrient inputs to the ocean affect the cycles of these elements?
  • How will changes in the abundance, distribution and stoichiometry of nutrient elements affect food web structure and function?
  • How will increases in hypoxia and anoxia affect food webs and cycles of key macro- and micronutrients?

Issue 2.4 Impacts of Harvesting on End-to-End Food Webs and Biogeochemical Cycles

  • How do harvesting-induced changes in food web structure impact biogeochemical cycles?
  • What are the impacts of harvesting living marine reources on end-to-end food webs?