What Happens When Ocean Eddies Hit a Wall?
Editors’ Highlight—Observing subsurface changes of two anticyclonic eddies passing over the Izu-Ogasawara Ridge
This study examines how submarine ridges create subsurface changes to ocean eddies. Looking specifically at two anticyclonic eddies in the North Pacific that migrate westward and encounter the Izu-Ogasawara Ridge, the authors analyze daily temperature and salinity data collected from Iridium Argo floats. Their analysis identifies changes in eddy vertical structure and diapycnal mixing as the eddies pass over the ridge. Mesoscale eddies play an important role in the mixing and redistribution of heat, salt and carbon, and also effect large-scale circulation and climate, so a better understanding of subsurface eddy-bathymetry interactions is valuable for climate research and forecasting.
A new study tracks two ocean eddies passing over the Pacific Ocean’s Izu-Ogasawara Ridge.
Spanning tens to hundreds of kilometers, mesoscale eddies spiral and swirl across the ocean, transporting just as much water as wind or deeper currents. Although scientists have long studied them from above by satellite, their 3-D motion is more difficult to track as they move over the seafloor and encounter undersea mountains and ravines.
To observe these hidden dynamics, scientists deploy buoyant bobbers called Argo floats, which trail sensors at different depths. Now, by dropping 17 Argo floats into a clockwise eddy east of Japan, Xu et al. have captured what happens when such an eddy hits the Izu-Ogasawara Ridge, a stretch of undersea mountains roughly north of the Marianas Trench.
The authors dropped the floats in the southwest moving eddy in March 2014. Several of the floats remained caught in the eddy for months, until the vortex reached the Izu-Ogasawara Ridge in late September and finally dissipated. Several other floats escaped the first eddy and got trapped in a second one, farther east. When this eddy encountered the ridge, it passed over it, and the floats became entrained in the current for nearly a year, until the current diminished in May 2015.
In total, the team collected more than 5000 data points on the two eddies, monitoring their structure and movement down to more than 1000 meters deep. As both eddies hit the ridge, they “domed up,” increasing in diameter, the team reports.
The eddies formed underwater structures known as Taylor columns, a phenomenon in fluid dynamics that occurs when rotating fluids encounter an obstacle and form a column of stagnant water above it. Despite all the turbulence happening deep underwater, the upper 200 meters of ocean remained largely unperturbed as the eddies hit the ridge, the team found.
-- Emily Underwood, Freelance Writer,
- Article Category
- Research Letters
Observing subsurface changes of two anticyclonic eddies passing over the Izu‐Ogasawara Ridge
- First Published:
- | Vol:
- | DOI:
Eos.org: Earth & Space Science News
Download the App
New Android App Available!
iOS App for iPad or iPhone
AGU Career Center
Featured Special Collection
The Magnetospheric Multiscale (MMS) mission has been performing particle and electromagnetic field measurements in the near-Earth environment since its launch in March 2015. Thanks to data with unprecedented time resolution on four identical spacecraft in a close tetrahedron configuration (down to 10 km), MMS science goals are to probe and understand the electron-scale physics involved in the magnetic reconnection process. This collection provides a selection of key results obtained during the first phase of the mission at the dayside magnetopause. It includes new observations of the geometry and variability of the reconnection process, the detailed dynamics of particles, fields and waves in the vicinity of the reconnection region, the observation of small-scale signatures at current sheets formed in the magnetosheath, in Kevlin-Helmholtz vortices, or flux transfer events, as well as other small-scale features which are by-products of magnetic reconnection or not. These results open a new window for our understanding of magnetic reconnection in space, with direct and numerous implications for astrophysical and laboratory plasmas.