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Hintergrund Auftrieb

An analysis of ocean plankton, so-called planktonic foraminifera, in a sediment core offshore southern Indonesia was performed to study the history of upwelling over the last 2,000 years. It is know that modern variability in upwelling off southern Indonesia is strongly controlled by the Australian-Indonesian monsoon and the El Niño-Southern Oscillation (ENSO), but its past variability beyond the instrumental record is not well understood.

Reconstructing climate variability of the past two millennia has become a primary interest to the palaeoclimate science community because this time scale is highly relevant to better understand the influence of changes in e.g. solar insolation and variations caused by the Earth itself as well as to distinguish between natural and human-induced changes on global climate. Our results suggest that around the time of the Little Ice Age (ca. CE 1400-1850), associated with cooler climate conditions in the northern hemisphere, upwelling was generally strong. Furthermore, two episodes of warmer climate conditions in the northern hemisphere, known as the Medieval Warm Period (ca. CE 950-1250) and the Roman Warm Period (ca. BCE 250- CE 400), were associated with a decrease in upwelling intensity off southern Indonesia.

The authors conclude that over the past 2,000 years stronger (weaker) upwelling off southern Indonesia was controlled by strengthened (weakened) Australian/Indonesian winter winds crossing the equator. In addition, it appears from their study that changes in the background state of the tropical Pacific, so-called “El Niño–like” or “La Niña–like” conditions may have substantially contributed to upwelling variations over hundreds of years as inferred from our records off southern Indonesia.

More Information:
http://onlinelibrary.wiley.com/doi/10.1002/2014GL061450/abstract