Onset and modifications in intensity and pathways of water mass exchange between the Southeast Pacific and the South Atlantic


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Gabriele.Uenzelmann-Neben [ at ] awi.de

Abstract

The opening of Drake Passage and the Scotia Sea enabled the exchange of water masses between the southern Pacific and the South Atlantic. In this way heat and energy could be transferred between the two oceans. Together with the opening of the Tasman Gateway this allowed the establishment of the Antarctic Circumpolar Current (ACC) thermally isolating Antarctica, which has been considered a one of the major causes for the onset of widespread glaciation. Both tectonic movements within Drake Passage and the Scotia Sea as well as modifications in climate have led to changes in intensity and pathway of the ACC and the water masses flowing within it. The onset of the ACC and those changes have been documented in sedimentary structures deposited on the Falkland Plateau. A study of the sediment drifts shaped by Circumpolar Deepwater, Weddell Sea Deepwater and Antarctic Bottomwater using high-resolution seismic reflection data will provide information on modifications of the circulation resulting from tectonic movements and changes in climate. Additionally, we will collect site survey data for an IODP proposal set on studying the earliest phase of water mass exchange via Drake Passage. The deep and bottom water masses flowing within the ACC (Antarctic Bottom Water (AABW), WSDW, SPDW, LCDW, UCDW) are steered by the complex topography of the Drake Passage and the Scotia Sea. Rounding topographic highs the water masses reduce their speed and hence deposit sediment while their speed is increased in gaps and passages rather leading to erosion and non-deposition. In this way the aforementioned water masses shape sediment drifts, which in their structure (geometry, internal unconformities, reflection characteristics) document the modifications in the flow paths and intensities of the water masses. The tectonic development of both the Drake Passage and the Scotia Sea during the Cenozoic have led to strong modifications in the flow paths, which, when studying sediment drifts, can be deciphered. Additionally, the ACC fronts are assumed to have been subject to relocations during glacial-interglacial cycles. This again has led to relocations in depocentres, which can be identified via seismic profiles. The questions we intend to answer are the following: • Can we add to the knowledge regarding the onset of the ACC and the deep and bottom water masses flowing within the ACC? • When can we recognise the first overspill of the Falkland Plateau indicating transport of cold water masses into the South Atlantic? • What are the variations of the pathways and intensity of overspill and the location of the ACC fronts in relation to a) tectonic movements, and b) modifications in climate (e.g. Mid-Miocene Climatic Optimum and Transition, Pliocene warming, onset of widespread glaciation on the Northern Hemisphere)? To answer those questions we will collect a grid of seismic profiles on the Falkland Ridge between a) the Falkland Islands and MEB, and b) MEB, the NEGR and South Georgia. This data set will further be used as preside survey data for IODP proposal 862-pre.



Item Type
Conference (Invited talk)
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Not peer-reviewed
Publication Status
Published
Event Details
Bilateral workshop on Cooperation in Marine Sciences between Argentina and Germany, 29 Nov 2016 - 01 Dec 2016, Buenos Aires, Argentina.
Eprint ID
42341
Cite as
Uenzelmann-Neben, G. (2016): Onset and modifications in intensity and pathways of water mass exchange between the Southeast Pacific and the South Atlantic , Bilateral workshop on Cooperation in Marine Sciences between Argentina and Germany, Buenos Aires, Argentina, 29 November 2016 - 1 December 2016 .


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