As you know, the Oleander program to scan upper ocean currents between Bermuda and New Jersey has been in operation since late 1992. This was about the same time modern altimetry made its start. We have many a time superimposed the velocity vectors on the surface temperature field but not so much on sea surface height. While the former offers resolution, the latter with its excellent spatial coverage at all times of the year gives us the dynamical framework for the Oleander velocity data.
Take a look at this fantastic archive of all earlier Oleander sections superimposed on SSH maps from Copernicus. It was prepared by Eric Firing and is publicly available:
https://currents.soest.hawaii.edu/oleander/vel_ssh_old/index.html
The eye is of course drawn to the Gulf Stream. The left panels show vectors on SSH maps. The panels to the right show the velocity components in the NE (normal to section, top) and NW (parallel to section, bottom) directions. For the most part they align rather well, but there is no reason this should be perfect for the velocity vectors are instantaneous whereas the maps are based on optimal interpolation of SSH measurements with a 10-day repeat rate. I still find it rather fascinating to realize that all water heading north in the Atlantic does so here in the Gulf Stream: not only is it the ‘classic’ western boundary current for the wind-driven circulation, it also includes the upper limb of the Atlantic meridional circulation.
The Oleander crosses cold core cyclonic rings every now and then. As they age maybe only one 0.25 m contour will identify the ring, but still be quite visible in the section plots, see Nov. 22 and 30, 1996. This case is also shown in Figure 6 in Luce and Rossby, 2008.
For a striking example of a cold-core ring formation, look at September 3, 2000, and following transects. And compare this to Figure 13 in Luce and Rossby, 2008. In the first crossing that looks like a ring, it is actually the trough of an extended meander. But it breaks off and rather quickly circularizes itself a full-blown CCR.
You can also see warm core rings passing by, consider the May 27 – June 9,1995 sequence. The 0.25 m contouring of the SSH misses the ring, but it shows up beautifully in the transects.
As you scroll through the files you’ll notice enormous variability in depth and along-track data returns. This is due to weather and sea-state. As winds increase the pitching of the ship will lead to increasing drawn-down of bubbles that block the ADCP acoustics. Load factor and ship heading also matters. The ship is less loaded on its Bermuda to New Jersey trips. It is also more likely to be heading into the wind, both factors that make for an easier draw-down of bubbles. You’ll also notice on average deeper returns north of the Gulf Stream in the Slope Sea than to the south – there are more scatterers there.
Enjoy!
Luce, D. L., and T. Rossby (2008). On the size and distribution of rings and coherent vortices in the Sargasso Sea, J. Geophys. Res., 113, C05011, doi:10.1029/2007JC004171.