Before the advent of modern observational and modeling techniques, understanding how the ocean behaved required piecing together disparate data -- often separated by decades in time -- from a handful of sources around the world. In the 1980s, that started to change when technological advancements, such as satellites, floats, drifters, and chemical tracers, made continuous, mass measurements possible. Still, the resulting new datasets often existed independently of each other, obscuring the big picture of how the ocean circulates, transfers heat, affects climate, stores carbon, and more. That's why Carl Wunsch, professor emeritus of physical oceanography in MIT's Department of Earth, Atmospheric and Planetary Sciences (EAPS) and member of the EAPS Program in Atmospheres, Oceans and Climate (PAOC), started spearheading an endeavor to reveal that big picture nearly 20 years ago. Following on the heels of the World Ocean Circulation Experiment (WOCE), Wunsch founded a consortium that sought to combine global ocean datasets with state-of-the-art circulation models.
Raffaele Ferrari, the Cecil and Ida Green Professor in Earth and Planetary Sciences and Director of the MIT Program in Atmospheres, Oceans and Climate, has been selected to receive the 2016 Robert L. and Bettie P. Cody Award in Ocean Sciences. While several individuals were considered for the prestigious prize, Ferrari's "pioneering efforts toward understanding the nature and rates of oceanic mixing and their consequences for the general circulation," were among several reasons for his selection. MIT professor emeritus of physical cceanography Carl Wunsch's seasoned insight and justification helped to settle the matter. "Raffaele Ferrari is awarded the 2016 Cody Prize for his stimulating and collaborative work directed at mechanisms of oceanic mixing and their interesting and sometimes unexpected consequences. With colleagues he has worked to greatly improve the rendering of mixing processes in numerical models directed at climate change and along the way has illuminated mixing processes with special attention to the submesoscale near the ocean surface, the mixed-layer generally, and the internal tide/internal wave field in its interactions with topography.
Since Captain James Cook's discovery in the 1770s that water encompassed the Earth's southern latitudes, oceanographers have been studying the Southern Ocean, its physics, and how it interacts with global water circulation and the climate. Through observations and modeling, scientists have long known that large, deep currents in the Pacific, Atlantic and Indian oceans flow southward, converging on Antarctica. After entering the Southern Ocean they overturn -- bringing water up from the deeper ocean -- before moving back northward at the surface. This overturning completes the global circulation loop, which is important for the oceanic uptake of carbon and heat, the resupply of nutrients for use in biological production, as well as the understanding of how ice shelves melt. Yet the three-dimensional structure of the pathways that these water particles take to reach the Southern Ocean's surface mixed layer and their associated timescales was poorly understood until recently.
At high latitudes, such as near Antarctica and the Arctic Circle, the ocean's surface waters are cooled by frigid temperatures and become so dense that they sink a few thousand meters into the ocean's abyss. Ocean waters are thought to flow along a sort of conveyor belt that transports them between the surface and the deep in a never-ending loop. However, it remains unclear where the deep waters rise to the surface, as they ultimately must. This information would help researchers estimate how long the ocean may store carbon in its deepest regions before returning it to the surface. Now scientists from MIT, Woods Hole Oceanographic Institution (WHOI), and the University of Southampton in the U.K. have identified a mechanism by which waters may rise from the ocean's depths to its uppermost layers.
In fact, over 90 percent of the planet's rising warmth -- specifically trapped by human-created greenhouse gas emissions -- is absorbed by the deep, salty waters. For the last half-century, scientists have worked to put a more precise number on just how much heat the oceans take up each year, and for good reason: More heat absorption might provide evidence that our pale blue dot is increasingly sensitive to the heat-trapping carbon amassing in our atmosphere -- which is likely at its highest levels in 15 million years. And now, new research published in the scientific journal Nature supports the highest -- or most problematic -- of those ocean heat estimates. "We found it's really in the top range of the estimates," Laure Resplandy, a Princeton University geoscientist who led the novel study, said in an interview. The Earth is warming, and most heat ends up in the ocean.