Time-Lapse Seismic Imaging of Oceanic Fronts and Transient Lenses within South Atlantic Ocean

Gunn, Kathryn L. and White, Nicholas J. and Caulfield, Colm-cille P. (2020) Time-Lapse Seismic Imaging of Oceanic Fronts and Transient Lenses within South Atlantic Ocean. Journal of Geophysical Research: Oceans. ISSN 2169-9291 (In Press)

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Oceanic fronts play a pivotal role in controlling water mass transfer, although little is known about deep frontal structure on appropriate temporal and spatial scales. Here, we present a sequence of calibrated time-lapse images from a three-dimensional seismic survey that straddles the Brazil-Malvinas Confluence— a significant feature of the merid- ional overturning circulation. Eight vertical transects reveal the evolution of a major front. It is manifest as a discrete planar surface that dips at less than 2 ◦ and is traceable to 1.5–2 km depth. Its shape and surface expression are consistent with sloping isopycnal surfaces of the calculated potential density field and with coeval sea surface tempera- ture measurements, respectively. Within the top ∼1 km, where cold fresh water subducts beneath warm salty water, a series of tilted lenses are banked up against the sharply de- fined front. The largest of these structures is centered at 700 m depth and is cored by cold fresh water. Time-lapse imagery demonstrates that this tilted lens grows and de- cays over nine days. It has a maximum diameter of < 34 ± 0.13 km and a maximum height of < 750±10 m. Beneath 1 km, where horizontal density gradients are negligi- ble, numerous deforming lenses and filaments on length scales of 10–100 km are being swept toward the advecting front.

Item Type: Article
Uncontrolled Keywords: 2020AREP; IA76
Subjects: 02 - Geodynamics, Geophysics and Tectonics
Divisions: 02 - Geodynamics, Geophysics and Tectonics
08 - Green Open Access
12 - PhD
Journal or Publication Title: Journal of Geophysical Research: Oceans
Depositing User: Sarah Humbert
Date Deposited: 15 Jun 2020 00:49
Last Modified: 15 Dec 2020 01:00
URI: http://eprints.esc.cam.ac.uk/id/eprint/4765

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