EGU2020-11616
https://doi.org/10.5194/egusphere-egu2020-11616
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Water Mixing and Circulation within the South Atlantic Basin Constrained by Seismic Reflection Images

Jingxuan Wei1, Robert Reece1, Will Fortin2, and Tanner Acquisto2
Jingxuan Wei et al.
  • 1Texas A&M University, College of Geosciences, Geology and Geophysics, United States of America (jingxuan.wei@tamu.edu)
  • 2Lamont Doherty Earth Observatory, Columbia University, United States of America

South Atlantic water masses and circulation significantly influence the dynamics and water mass structure of the Atlantic Meridional Overturning Circulation (AMOC). Previous research in the South Atlantic has mostly focused on energetic regions such as the Brazil/Malvinas Confluence Zone along the western boundary and the Agulhas retroflection to the east. However, it is also important to understand water circulation and diapycnal mixing within the South Atlantic Basin (SAB). Previous studies have observed low salinity patches of the Antarctic Intermediate Water within the western side of the SAB at 30o S, but the temporal variability of the scales, locations and structures of these low salinity patches are still uncertain. Former studies also show an increased level of mixing within the SAB above the Mid-Atlantic Ridge, but did not evaluate mixing on smaller scales such as mesoscale and sub-mesoscale.

Here we present a water mass structure analysis at 30o S from Rio Grande Rise to the Mid-Atlantic Ridge by using Seismic Oceanography (SO). SO is being applied around the world to image mesoscale water mass structures using the seismic reflection method. Reflections in the seismic images are essentially temperature gradients that are proxies for isopycnal surfaces. We paid particular attention in seismic processing to imaging of structures that characterize the boundary between water masses. We imaged the upper South Atlantic Central Water, and identified discontinuous water boundaries (about 150 km long) between the Antarctic Intermediate Water and the North Atlantic Deep Water that could correspond to the intermittent appearance of low salinity patches. We combine seismic images with previous hydrographic measurements to investigate the temporal change of these low salinity patches. We use a horizontal slope spectra to quantify mixing rate from tracked seismic horizons to evaluate mesoscale and sub-mesoscale mixing events such as internal waves and eddies. Through SO, we hope to better constrain South Atlantic circulation and contribute to the understanding of AMOC as a whole.

How to cite: Wei, J., Reece, R., Fortin, W., and Acquisto, T.: Water Mixing and Circulation within the South Atlantic Basin Constrained by Seismic Reflection Images, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11616, https://doi.org/10.5194/egusphere-egu2020-11616, 2020

This abstract will not be presented.