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- Title
Dynamics of Deep Ocean Eastern Boundary Currents.
- Authors
Yang, Xiaoting; Tziperman, Eli; Speer, Kevin
- Abstract
The long‐standing paradigm for the large‐scale time‐averaged ocean circulation in the world oceans includes intensified currents at the western boundary, and a much slower interior flow elsewhere. However, poleward deep boundary currents in the eastern limits of the deep South Pacific, Atlantic, and Indian Oceans have been observed repeatedly at 2‐ to 4‐km depth. They carry up to a third of the total deep ocean transports, implying a significant role in climate, yet their dynamics are still not well understood. Here we develop a theoretical understanding for these currents, using a hierarchy of realistic and idealized models, focusing on the South Pacific Ocean. The deep eastern boundary current there is shown to be driven by a traditional interior balance together with a narrow boundary layer scale near the eastern boundary, which exists only when stratification and topography are both included. A simplified semianalytical vorticity model is developed for the deep eastern boundary current. Plain Language Summary: Intense ocean currents tend to be found on the western side of ocean basins, including, for example, the Gulf Stream in the North Atlantic Ocean, the Kuroshio current in the North Pacific Ocean, and the Somali and Agulhas Currents in the Indian Ocean. However, observations show that there are also significant currents along the eastern boundaries of the Atlantic, Pacific, and Indian Oceans in the Southern Hemisphere. These are found at a depth of 2–4 km, where currents are typically expected to be weak. These currents carry a significant amount of mass, heat, and carbon and therefore are a significant factor of the climate system, yet the reason for their presence is still not understood. Here we study these currents using realistic and theoretical models and provide an explanation for their dynamics. We show that these currents exist due to the ocean bottom topography and that they are inherently different from ocean currents found on the western side of the oceans, and from upper‐ocean eastern boundary currents. Key Points: Southeast Pacific Ocean deep eastern boundary current, not well understood, is successfully simulated and explainedA simple vorticity model, including the effects of bottom topography and heat diffusion is used to explain the dynamics of this currentIt is driven mostly by vortex stretching, with strong trapped vorticity trends due to eddy mixing only near the eastern boundary
- Subjects
PACIFIC Ocean currents; OCEAN currents; AGULHAS Current; OCEAN dynamics; OCEAN circulation; OCEAN bottom
- Publication
Geophysical Research Letters, 2020, Vol 47, Issue 1, pN.PAG
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2019GL085396