Three-dimensional modeling of earth's ocean climate

Science Daily: Earth scientists are reaping huge benefits from research performed on NASA's advanced supercomputers. New cube-based simulations are helping to improve estimates of ocean circulation and climate.

Researchers from NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif. and Massachusetts Institute of Technology (MIT), Cambridge, Mass., are using a new gridding method that projects the faces of a cube onto the surface of a sphere. They found that this method covers the sphere more uniformly than a latitude-longitude grid, and that it produces more accurate results near Earth's poles.

…Scientists believe the ocean and its interactions with the atmosphere are key to studying climate change. To better understand these interactions, they identified three important areas in climate research. They look at the 'states' of the ocean and sea-ice, which includes their temperature, salinity, current speeds, and sea-surface elevation, and study their changes at and below the surface. They also look at the 'state' of the atmosphere, which includes its temperature, humidity, and wind patterns, and study how it was affected by the changes in the ocean. These interactions between the atmosphere and ocean directly affect the weather, according to Hill. Finally, the scientists study the biological activity in the ocean and its responses to the changing 'state' of the ocean.

"The day-to-day weather comes from the atmosphere state, but it is strongly modulated by the ocean state. Other less apparent processes, such as the carbon dioxide extracted from the atmosphere by the ocean, depend on the oceans' physical and biological state," said Hill.

Following work begun by Carl Wunsch and colleagues at MIT as part of the World Ocean Circulation Experiment, a NASA-sponsored project called Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2), is modeling the global ocean currents and their fluctuations, the changes in temperature and salinity, and the growth and melting of sea-ice in the polar regions.

The project's goal is to produce quantitative images of the state of the ocean globally, including its evolution. These images use data from all available NASA satellites and from on-site instruments, and are the result of combining and assimilating these data into global full-ocean-depth and sea-ice configurations built by the MIT general circulation model (MITgcm). These data combinations, called data syntheses, help quantify the role of the ocean in the global carbon cycle, explain the recent evolution of the polar oceans, and monitor time-evolving balances within and between different components of the Earth system….

The NAS facilities have been critical to the initial cube computation, which was carried out on the NAS SGI Altix system, Columbia. More recently it has been moved to the NAS Pleiades cluster facility. Photo Credit: NASA