The spatial extent of the Deep Western Boundary Current into the Bounty Trough: new evidence from parasound sub-bottom profiling
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Deep currents such as the Pacific Deep Western Boundary Current (DWBC) are strengthened periodically in Milankovitch cycles. We studied periodic fluctuations in seismic reflection pattern and reflection amplitude in order to detect cycles in the sedimentary layers of Bounty Trough and bounty fan, east of New Zealand. There, the occurrence of the obliquity frequency is caused only by the DWBC. Therefore, it provides direct evidence for the spatial extent of the DWBC. We can confirm the extent of the DWBC west of the outer sill, previously only inferred via erosional features at the outer sill. Further, our data allow an estimation of the extent of the DWBC into the Bounty Trough, limiting the DWBC presence to east of 178.15°E. Using the presented method a larger dataset will allow a chronological and areal mapping of sedimentation processes and hence provide information on glacial/interglacial cycles.
KeywordsParasound sub-bottom profiler Milankovitch cycles Deep Western Boundary Current (DWBC) Bounty Trough
We are grateful for the support of Captain H. Andresen and his crew during RV Sonne cruise 169 and Captain O. Meyer and his crew during RV Sonne cruise 213/2 as well as the Parasound watch keepers during both cruises. Additionally, we would like to thank Dr. Robert Larter and Dr. Neil Mitchell for their helpful comments and suggestions on an earlier version of this manuscript. We are further grateful for the helpful comments of two anonymous reviewers and the editor R. Urgeles. The cruises and this research were funded by the Bundesministerium für Bildung und Forschung under contract number 03G0169A and 03G0213A. The Parasound data this paper is based on can be found in the PAGAEA (www.pangaea.de) Database.
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