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Principal Investigators: Aline Govin (MARUM, University of Bremen), Matthias Prange (University of Bremen), André Paul (University of Bremen)

Project Scientists: Ben Blazey (Post-doc, University of Bremen)


What ends an Interglacial?

Top: Sea level curve (Waelbroeck et al. 2002) for the last 150 thousand years. The red rectangle highlights the Last Interglacial period, while the blue arrow indicates the sea level decrease at the end of the Last Interglacial (last glacial inception).

Bottom left: Mean annual precipitation Change simulated by the Community Climate System Model CCSM3.0 between 115 and 125 ka (figure courtesy of R. Rachmayani, M. Prange). It shows wetter conditions in southern Brazil at 115 ka than 125 ka, in agreement with available data (Cruz et al. 2005).

Bottom right: Mean annual (1950-1999) terrestrial precipitation (mm/y, University of Delaware) and annual Sea Surface Salinity (World Ocean Atlas 2009). The black dots refer to the GeoB marine sediment cores investigated in this study. Blue letters highlight the mouth of the Orinoco (Or), Amazon (Am), São Francisco (SF) and La Plata (LP) rivers.

When and how the present interglacial will end remains an open question. With a relatively well-known climate, the Last Interglacial (LIG) and following glacial inception can shed some light on the climate mechanisms leading to the establishment of a new ice age. Two key questions arise from the chain of climate events known to end the LIG: (1) Did the interglacial North Atlantic warmth, prolonged by an active thermohaline circulation (THC), favour or delay the growth of northern ice sheets? (2) Did reorganizations in South American moisture contribute to prolong the North Atlantic warmth by maintaining a salty North Atlantic and active THC at the end of the LIG, as suggested by tropical moisture feedbacks observed during glacial times? To address these questions, we propose here to combine new paleoclimate reconstructions with climate model experiments. First, we will reconstruct the detailed evolution of the South American rainbelt during the last glacial inception, by applying complementary proxies on a transect of marine sediment cores. Second, we will assess the impact of tropical hydrologic changes on tropical Atlantic sea surface salinities (SSS) and the Atlantic THC, by comparing tropical Atlantic SSS and deep-water properties with model sensitivity experiments where we will vary the tropical freshwater forcing. Finally, we will perform a transient climate/ice-sheet model run for the last glacial inception, and a sensitivity study, in which different ocean heat fluxes will be imposed to investigate the effect of prolonged North Atlantic warmth on ice sheet growth.


Semi-quantitative paleo-hydrology reconstructions (bulk sediment major element concentrations, compound-specific carbon and hydrogen isotopes), quantitative paleo-temperature reconstructions (Mg/Ca ratio of planktic foraminifera), stable isotopes of planktic and benthic foraminifera, asynchronously coupled climate-ice sheet modelling


Marine records (eastern margin of South America)



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