Variabilities in intermediate- to deep-water ventilation of the South Pacific

Thomas.Ronge [ at ]


Recent publications on the ventilation-history of the SW-Pacific indicate very high ventilation-ages for the last glacial. This stands in contrast to benthic δ13C-data from this area which show that the ventilation difference for the last glacial, indicated by a pronounced chemocline in a depth of 3000 m, diminishes from the Atlantic, over the Australian Sector to the SW-Pacific. Our investigation will shed new light on this paleoceanographic problem, using a unique transect of sediment records through the Bounty Trough off New Zealand. This transect comprises all water masses between 5000 and 500 mbsl. We will reconstruct the ventilation history for the LCDW, UCDW, AAIW and SAW, using 14C-radiocarbon dating’s as well as δ13C-reconstructions on planktonic and benthic foraminifera. With our data we will be able to assess if the ventilation-gradient of the Southern Ocean diminishes from West to East or if it is still pronounced in the New Zealand Sector. All cores were tuned to the existing age-model of the sediment-core MD97-2120, using high resolution XRF-scans. These correlations enabled us to define different but isochronous climatic intervals for each core, which correspond to Northern and Southern Hemisphere climatic events, known as the Holocene, the Younger Dryas, the Antarctic Cold Reversal, Heinrich 1, the Last Glacial Maximum as well as Heinrich 2. The advantage of our core-locations, besides their coverage of several water masses, is also their relative close proximity to each other. Due to that, all cores should record changes in the frontal systems over time in a similar way, so that their reservoir-ages should differ only slightly if at all. To get a better understanding of the reservoir-ages two different assessment methods are applied. On the one hand we will use tephra layers, contained in our sediment cores, to compare their known ages with the 14C-ages of planktonic foraminifera, embedded within the ash layers, like G. bulloides or N. pachyderma. On the other hand paleomagnetic analyses will provide reliable ages for certain intervals that we can compare to our microfossil ages as well. Especially the Kawakawa tephra with an age of 26.17 ky falls in the crucial time interval for our analyses and provides an important time marker. The temporal resolution of all sediment cores chosen is so high that not only all climatic intervals mentioned above are found within each core, but in case a sample is lacking a sufficient amount of foraminifers, we are able to skip to the neighboring sample without missing the aimed climatic interval. This enables us to determine and reconstruct the water mass ventilation variability of the Southern Ocean in great detail.

Item Type
Conference (Poster)
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Publication Status
Event Details
2012 AGU Fall Meeting, 03 Dec 2012 - 07 Dec 2012, San Francisco.
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Cite as
Ronge, T. , Tiedemann, R. , Lamy, F. and Sturm, A. (2012): Variabilities in intermediate- to deep-water ventilation of the South Pacific , 2012 AGU Fall Meeting, San Francisco, 3 December 2012 - 7 December 2012 .

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ANT > XXVI > 2

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