The Motion of the Ocean
Posted by sogasex on March 20, 2008
By Alejandro Cifuentes, University of Connecticut
“It’s not about the size of the wave Ale, it’s the motion of the Ocean!” My friend Mike said this to me a couple of years ago while in the midst of a challenging climbing adventure in the Andes. I have since found comfort in the metaphorical meaning of that phrase, but as I sit in the main lab of the Ronald H. Brown, it acquires a new, more literal meaning for me. These days I am actually feeling the motion of the ocean in the Southern Ocean. My goal here is to acquire data to further understand air-sea interaction, specifically mass, momentum and energy exchange at high wind regimes and turbulent seas. Not in the least, this data will provide the foundation for my doctoral dissertation.
So to me these days, the motion of the ocean translates to Pitch, Roll and Yaw. Pitch is the instantaneous tilt of the bow of the ship, Yaw is the change in its Heading and Roll describes the side-to-side movement of the ship over its own horizontal axis. From the motion packages mounted high up on the ship’s mast we can read these angles and the associated accelerations in the X, Y and Z directions. Armed with these data we can supply a motion correction for the wind velocities and for other measurements that need filtering of the motion attribute to the ship. At the end of this process, off comes the motion of the ocean (unfortunately it loses some romanticism in this step as you can imagine). You can be sure however, that this motion is preserved in me. Unfortunately there is no motion correction for me, rather I am forced to try to get along with the Pitch, Roll and Yaw during this cruise, my very first cruise as a graduate student in Oceanography. I must say, Pitch is definitely the most annoying, or as my mother would suggest the least pleasant of all.
So with the motion of the ocean lost, the issue might be after all about the size of the waves. Or maybe it’s not the size of the waves so much as the wave’s age, steepness, the energy state of the wave field at the surface, the wind friction velocity, bubbles due to wave breaking or perhaps a nice combination that generates the turbulence in which we are interested. One thing is for certain, I have millions of questions, the answer to one always leading to another. After my first semester in the Oceanography program I still stand in ignorance as I look to the sea, watch the waves brake and hear the winds roar. I know that the answers can be found out there in nature, the enhanced exchange by turbulence, the nature of air-sea interaction, energy distribution and much, much more all that I need to do is focus in asking the right questions. Perhaps in life and science, Mike is right. The answer will not be in the waves itself, but in how the whole ocean system works and evolves. But, no matter the answer, I am sure that in one way or another we will always be captivated by the motion of the ocean.
PS: Mike lives in England and continues to make remarkable observations, especially when he is inspired by the mountains.
Sergio Pezoa from NOAA rigging up the Mast. The Sonic Anemometers stand first in line to get undistorted flow. The motion packages are attached to the Sonic units.
Whitecaps in the Southern Ocean, view from 0-2 Deck. Picture taken by Byron Bloomquist, University of Hawaii.
Morning has broken in the Southern Ocean.