C e l e b r at i N g 5 0 Y e a r s o f t h e i N t e r g o V e r N m e N ta l o C e a N o g r a p h i C C o m m i s s i

Evolutionary pressures have led humans to walk in a highly efficient manner that conserves energy, making it difficult for exoskeletons to reduce the metabolic cost of walking. Despite the challenge, some exoskeletons have managed to lessen the metabolic expenditure of walking, either by adding or storing and returning energy. We show that the use of an exoskeleton that strategically removes kinetic energy during the swing period of the gait cycle reduces the metabolic cost of walking by 2.5 ± 0.8% for healthy male users while converting the removed energy into 0.25 ± 0.02 watts of electrical power. By comparing two loading profiles, we demonstrate that the timing and magnitude of energy removal are vital for successful metabolic cost reduction.

EXECUTIVE SUMMARYCoastal environments are an important component of the global carbon cycle, and probably more vulnerable than the open ocean to anthropogenic forcings. Due to strong spatial heterogeneity and temporal variability, carbon flows in coastal environments are poorly constrained. Hence, an integrated, international, and interdisciplinary program of ship-based hydrography, Voluntary Observing Ship (VOS) lines, time-series moorings, floats, gliders, and autonomous surface vessels with sensors for pCO 2 and ancillary variables are recommended to better understand present day carbon cycle dynamics, quantify air-sea CO 2 fluxes, and determine future long-term trends of CO 2 in response to global change forcings (changes in river inputs, in the hydrological cycle, in circulation, sea-ice retreat, expanding oxygen minimum zones, ocean acidification, …) in the coastal oceans. Integration at the international level is also required for data archiving, management, and synthesis that will require multi-scale approaches including the development of biogeochemical models and use of remotely sensed parameters. The total cost of these observational efforts is estimated at about 50 million US dollars per year.

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The increase in atmospheric carbon dioxide (CO 2 ), originating largely from human fossil fuel combustion and deforestation since the beginning of the industrial era, is causing a decrease in ocean pH and changes to seawater carbonate chemistry. This process, termed ocean acidification, is now well established from modeling and field data, and the rate of change in ocean pH and carbon chemistry is expected to increase significantly over this century unless future CO 2 emissions are restricted dramatically. The rate of CO 2 increase is the fastest the Earth has experienced in 65 million years , and the current concentration is estimated to be the highest in, at least, the past 50 million years (Zachos et al., 2008). Central to predicting the atmospheric carbon inventory during the 21st century will be understanding and predicting the adjustments in the ocean uptake and exchange of both anthropogenic and natural CO 2 . To quantify these changes on a global scale, an international interdisciplinary program of ship-based hydrography, time-series moorings, floats and gliders with carbon, pH and oxygen sensors, and ecological surveys is already underway. This program together with implementations of molecular technology will help scientists determine the extent of the large-scale