Alfred Wegener Institute for Polar Marine Research, Germany

The response of the northern extension of the Atacama Desert and the Peruvian upwelling system to climate conditions during the Last Interglacial ([LIG]; approximately 125 kyr ago) was tracked using molecular fossils of marine and terrestrial organisms preserved in Peruvian shelf sediments. High resolution records of ODP Site 1229 (past 145 kyr) indicated that warmer and wetter conditions (rainfall and river runoff) along the coast occurred during the LIG, when global temperatures were comparable or even higher than today. A approximately 3 degrees C warming of surface waters, enhanced water column stratification, rainfall and river runoff were associated with low primary productivity and a approximately 1.5 degrees C decrease in the temperature gradient across the Equatorial Pacific (i.e., weak Walker circulation), suggesting a prolonged El Nino-like response of the tropical Pacific during the LIG. In contrast, the late Holocene ([LH] last 3 kyr) was characterized by colder surface waters, higher export and primary productivity, and a drier climate.