Ocean research fundamental to study of life on earth

COURTESY URI/MICHAEL SALERNO
SEA O2: Thomas Rossby, professor emeritus of oceanography at the University of Rhode Island, says a good percentage of the carbon dioxide increase is being taken up by oceans.
COURTESY URI/MICHAEL SALERNO SEA O2: Thomas Rossby, professor emeritus of oceanography at the University of Rhode Island, says a good percentage of the carbon dioxide increase is being taken up by oceans.

When Thomas Rossby retired from teaching last fall after 36 years at the University of Rhode Island’s Graduate School of Oceanography, he was not only one of the university’s longest-serving professors, but one of the most distinguished in his field. Since first studying oceanography at the Massachusetts Institute of Technology in the late 1960s, Rossby used his engineering background to develop new techniques for measuring ocean currents, including through individual floats and on instruments attached to ocean-going ships.
At a recent URI “Rossby Symposium,” former students and colleagues gathered to discuss his research and contributions to the understanding of the world’s oceans.

PBN: For years scientists have wondered whether rising global temperatures and melting polar ice could result in significant changes to the Gulf Stream. From your research, what is going on in the Gulf Stream and is it in any danger?
ROSSBY: From the measurements we have taken over 20 years now, we can say with considerable confidence how the Gulf Stream varies seasonally and from one year to the next. The good news is that the Gulf Stream is not changing – it is quite stable. It is fluctuating from year to year thanks to wind systems that vary, winters are never the same, so it fluctuates, but there is no evidence whatsoever that it is slowing down or speeding up.

PBN: Are there any major changes that you do see in the Atlantic water currents?
ROSSBY: We are seeing quite large changes in the northern Atlantic, east of Labrador and west of the United Kingdom. There are large expansions and contractions of the pool of cold water, what is called the polar gyre east of Greenland. Those are probably mostly related to changes in heating and cooling but the winds are also playing an important role. There is a lot we don’t understand there and that is an area we must instrument better. There is much interest in being able to do a better job in measuring the North Atlantic. The ocean plays a whopping, big role [in the climate] because it stores so much heat and fresh water. It is after all the source of our precipitation. It stores water and heat in enormous quantities, so it is very important that way. The atmosphere picks these things up and redistributes them and re-deposits them in the ocean. So you can’t look at the ocean in isolation but as a partner in the global transport of heat.
PBN: What are some of the things that you have learned over the course of your career that surprised you about the ocean?
ROSSBY: One example certainly is the discovery of these huge lenses of water in the ocean-bodies of water that are spinning either clockwise or [counter]-clockwise. They are not detectable at the surface, they float and are spinning at some depth in the ocean. They may be 20-30 miles in diameter and 1,000 feet thick. They could be floating at 1,000 meters depth.
The specific discovery was in 1977 when we found northeast of the Bahamas such a lens that was spinning 1,000 meters over a period of six days for one revolution. It was actually quite thin, only a few hundred meters thick. But it was very warm and very saline. … Just discovering this lens was quite an eye-opener. We knew of surface ones before, we were not really aware of these things at depth. Where this was particularly exciting was that it was so warm and saline. This told us that the lens must have come from the Mediterranean, which was the only source of warm salt water in the North Atlantic. A former student and I wrote a paper on this and this kind of lens became known as a Mediterranean eddy, or meddy, and that’s really stuck with us in the literature. Another is the Gulf Stream as it crosses the North Atlantic, it does so in very specific places and the reason is they are guided by the openings in the mid-Atlantic ridge.

PBN: How have attitudes toward oceanography changed in the scientific community?
ROSSBY: From an academic or scientific point of view there has been a huge change in the last half century. … Back in the 1960s, oceanography was still to a considerable extent an academic activity. Intellectually people knew that the ocean played a big role in climate. But my sense is that oceanography was still more of an intellectual endeavor than it was something of fundamental importance to the health of our climate. Yes, people knew it was the case, but I don’t think it had become a visceral feeling.
Today, oceanography holds absolutely center stage as a full partner in discussions of global change. It is a huge sink for heat and fresh water. It’s also a whopping big reservoir for carbon dioxide, which we are pumping into the atmosphere.
A good percentage of the carbon dioxide increase is being taken up by oceans. That is good news. The flip side is we are increasing the acidity and that is having impacts on the life cycle. That could be more serious than anything because it affects the ocean as a giver of life.

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PBN: Is there more interest in oceanography now than there used to be?
ROSSBY: There is definitely more interest now as a societally important part of the planet. Before, 50 years ago I don’t think that was the case. It was exciting, people were thrilled to enter the field and intellectually we knew it was important, but … it had not become center stage about our concerns of the health of the world. •

INTERVIEW
Thomas Rossby
POSITION: Professor emeritus of oceanography at the University of Rhode Island
BACKGROUND: Born in Boston and raised in Sweden from age 10, Rossby returned to the United States in 1966 with a background in applied physics to study oceanography at the Massachusetts Institute of Technology. From there he moved to Yale University and later URI, where he helped develop new equipment and techniques to measure ocean currents.
EDUCATION: Master’s degree in applied physics from Royal Institute of Technology in Stockholm, Sweden, 1962; Ph.D. in oceanography from MIT, 1966
FIRST JOB: Researcher during post-doctorate work
RESIDENCE: North Kingstown
AGE: 74

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