30 April 2015

Ocean Currents Alone Cannot Explain the Zapiola Rise


Sediments and their transport by ocean currents play an important role in the World’s Oceans. Their impact on bathymetry can modify the ocean circulation, and they can fertilize pelagic ecosystems by releasing biogeochemical agents. A fascinating feature is the Zapiola Rise, a sedimentary complex that stands more than a kilometer tall in the Argentine Basin. It is responsible for the Zapiola Anticyclone, a standing ocean eddy that is possibly the strongest circulation feature in the ocean; and it strongly controls the ocean turbulence in the basin. Located in a basin where the most important water masses are exchanged between the Atlantic and Southern Oceans, it is likely to have a significant impact on mixing and water mass transformations. Understanding the complex interplay between the turbulent ocean circulation, sediments, and bathymetry in this unique part of the World Ocean is therefore a timely undertaking.

In this study we address whether the turbulent ocean circulation alone can explain the presence of the Zapiola Rise. We perform experiments with Los Alamos National Laboratory’s Parallel Ocean Program (POP) in high resolution, eddy-resolving configuration. We release sediments in La Plata estuary and study their distribution through the Argentine Basin. We find no evidence for sediment convergence over the Zapiola Rise. Instead, the Zapiola Anticyclone appears to be a barrier for transport of sediments onto the Zapiola Rise. We conclude that details of sediment dynamics are important to explain the Zapiola Rise as a region of preferred sedimentation, and point to processes like resuspension as possible key mechanisms.

Wilbert Weijer
Los Alamos National Laboratory (LANL)
Weijer, W, ME Maltrud, WB Homoky, KL Polzin, and LR Maas.  2015.  "Eddy-Driven Sediment Transport in the Argentine Basin: Is the height of the Zapiola Rise hydrodynamically controlled?"  Journal of Geophysical Research 120, doi:10.1002/2014JC010573.

This research was supported by the Regional and Global Climate Modeling Program of the US Department of Energy Office of Science (WW). Los Alamos National Laboratory is operated by the Los Alamos National Security, LLC for the National Nuclear Security Administration of the U.S. Department of Energy under contract DE-AC52-06NA25396.