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Thoughts on Oceanography in 2025

Daniel Rudnick*

OBSERVATIONS, MODELING, AND SCALES

Oceanography has tended to be an observational science in the sense that phenomena have been observed before they were predicted theoretically. An open question is whether this view will have to evolve as numerical models become more realistic, and predict features in greater detail than can be easily observed. A growing emphasis on prediction will continue until 2025. Observations will have at least two fundamental roles as prediction becomes better. First, observations will continue to be needed to validate models, and to provide ground truth for initialization and assimilation. Second, observations will be essential to develop parameterizations for mixing, where mixing is used as a general term for all processes of smaller scale than can be simulated directly by the model. What we call “mixing” should be understood as purely operational: as computers get faster and spatial grids get finer, the unresolved processes are themselves of finer scale. The observational focus should then be what is now commonly called the submesoscale or finescale, smaller than mesoscale eddies of order tens of kilometers, and larger than the microscale of centimeters. Many autonomous platforms are well suited to such observations, and their use will certainly expand.

*

Scripps Institution of Oceanography, University of California, San Diego



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Thoughts on Oceanography in 2025 Daniel Rudnick* OBSERvATIONS, MODELING, AND SCALES Oceanography has tended to be an observational science in the sense that phenomena have been observed before they were predicted theo- retically. An open question is whether this view will have to evolve as numerical models become more realistic, and predict features in greater detail than can be easily observed. A growing emphasis on prediction will continue until 2025. Observations will have at least two fundamental roles as prediction becomes better. First, observations will continue to be needed to validate models, and to provide ground truth for initializa- tion and assimilation. Second, observations will be essential to develop parameterizations for mixing, where mixing is used as a general term for all processes of smaller scale than can be simulated directly by the model. What we call “mixing” should be understood as purely operational: as computers get faster and spatial grids get finer, the unresolved processes are themselves of finer scale. The observational focus should then be what is now commonly called the submesoscale or finescale, smaller than mesoscale eddies of order tens of kilometers, and larger than the microscale of centimeters. Many autonomous platforms are well suited to such observations, and their use will certainly expand. * Scripps Institution of Oceanography, University of California, San Diego 9

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50 OCEANOGRAPHY IN 2025 CLIMATE CHANGE A major focus of the next twenty years must be the study of the ocean’s role in climate. Climate change has entered the public conscious- ness to an extent unparalleled by any scientific issue in recent times. How we respond to climate change is the scientific challenge of our generation. How can oceanographers respond to this challenge? We will certainly be called upon to document change as it occurs, and to evaluate attempts at remediation. Research on alternative energy sources will intensify, but energy derived from the ocean is likely to be significant only in certain locations, not as a global solution. Global observations of the ocean will continue to improve, with moorings, floats, and gliders forming the back- bone of the system. A fundamental challenge to improved understand- ing is the long time scales involved: time series long enough to achieve definitive answers may be too far in the future to help us solve problems in time. PHYSICAL/BIOLOGICAL INTERACTIONS The next two decades will see the solution of many problems strad- dling the boundary of physics and biology. A driving force will be the development of new and better biological sensors. Increasing numbers of biological variables will be measured at the same resolution as physical variables. The physical processes that supply nutrients to the eupho- tic zone will be quantified to the extent that reliable predictions of pri- mary production will be possible. Distributions of zooplankton will be observed and modeled better than ever before, so predictions of biomass will be at the same stage that predictions of salinity and temperature are today. The ultimate result of these advances will be better stewardship of fisheries, as ecosystem observation, modeling and prediction reaches maturity in 2025. THOUGHTS ON EDUCATION In the past, most graduate students had a bachelor’s degree in a basic science, engineering or mathematics before beginning study in oceanog- raphy. As programs in environmental sciences sprout across the country, students who would have followed the traditional path by taking a basic science will receive more interdisciplinary training. As the number of courses taken by an undergraduate is necessarily finite, this increased breadth must come at a cost of depth of knowledge in a particular dis- cipline. We are already seeing this effect in physical oceanography, as incoming students with interdisciplinary undergraduate degrees are nota- bly less capable at math than typical graduate students of the past. As

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51 DANIEL RUDNICK educators, we must change how we teach, and even what we teach, to achieve the best results with the new generation of students. A positive outcome will be future oceanographers who are better at crossing disci- plinary boundaries, and explaining scientific results to non-specialists. A potential problem may be scientists without a core expertise. How will the next generation gain the depth of knowledge to design the next great oceanographic instrument, or make a fundamental breakthrough in theory? HOW SCIENCE GETS DONE An approach to achieving the breadth of expertise needed to solve outstanding scientific problems is to form teams of scientists from dif- ferent disciplines. Teams like these can be intellectually rewarding for participants, and can lead to products unrealizable by individuals. How- ever, in the future as now, scientists working long solitary hours in offices and labs will make the most fundamental advances. While inspiration can be drawn from a variety of sources, originality comes from within. A graduate student working in obscurity now will be the emerging leader of 2025. UNSOLvED PROBLEMS The most exciting unsolved problems of 2025 are likely, as always, to be the problems uncovered by solving today’s problems. I will not attempt to divine these, which is a prediction an order of magnitude more diffi- cult than the guesses I have made so far. There will be, however, current problems that will remain unsolved in 2025. The fundamental limitation on the durability of oceanographic instrumentation will continue to be corrosion and biofouling. Whatever advances will be made in improved sensors and energy sources for ocean observations, electrons will always move and life will find a way. In this sense the ocean is an observational frontier unlike land, atmosphere, or space.