The seminar has been organized for the Ph.D. Program in Science and Management of Climate Change.

Lecturer
Dr. Thorsten Kiefer
(Past Global Changes (PAGES) International Project Office, Bern, Switzerland)

The nitrogen cycle, ocean acidification, surface temperature trends, sea level, and sea ice are major topics in oceanography and in the general global change debate. The topics are associated with questions about how current trends of eutrophication, acidification, warming, sea level rise and sea ice retreat need to be assessed in the context of natural dynamics in the Earth system. Here, paleoceanography – and only paleocanography – can provide the long-term information about times that reach back beyond the limited observations from at best a century of measurements and a few decades of satellite observations.

The Past Global Changes project (PAGES) and other international organizations coordinate crowdsourcing of data and knowledge towards global-scale synthesis of paleoceanographic changes over centuries and millennia, and sometimes up to millions of years. I will present examples how global data were compiled and synthesized to show an acceleration of the marine nitrogen cycle in the transition to the Holocene, how geologic events can help us constrain possible impacts of ongoing ocean acidification, and how proxy data demonstrate that the surface oceans cooled over two millennia and possibly longer before the trend was reversed in some regions. In addition, I will also touch on issues of sea level and sea ice change and introduce a brand new working group on ocean overturning circulation and one on Holocene climate that might follow soon.