Aquarius
Illustration of Aquarius/SAC-D above Earth
Aquarius is a focused satellite mission to measure global Sea Surface Salinity. After its 2011 launch, it will provide the global view of salinity variability needed for climate studies. The Aquarius / SAC-D mission being developed by NASA and the Space Agency of Argentina (Comisión Nacional de Actividades Espaciales, CONAE).
Overview
As seen from space, Earth has been described as a "blue marble," dominated by sapphire oceans and swirls of white clouds. Continents appear as widely spread outposts, covering less than one-third of the planet's surface. Earth is dominated by water in all its forms: liquid seas, vaporous clouds, and solid ice. The interplay among these forms is depicted as a "water cycle": a water molecule in today's ocean may be found in tomorrow's cloud, then in a glacier during the next Ice Age, and then in the ocean again as climate warms.
The cycling of water and energy through the atmosphere and oceans is crucial to life on Earth. Yet the ties among the water cycle, ocean circulation, and climate are poorly understood. Interestingly, global measurement of Sea Surface Salinity (SSS) over time provides a clear way resolve these relationships. By tracking SSS we can directly monitor variations in the water cycle: land runoff , sea ice freezing and melting, evaporation and precipitation over the oceans. Global SSS data will allow us to create unprecedented computer models that bridge ocean-atmosphere-land-ice systems, with the goal of predicting future climate conditions.
Science
The Aquarius science goals are to observe and model the processes that relate salinity variations to climatic changes in the global cycling of water and to understand how these variations influence the general ocean circulation. By measuring salinity globally and synoptically every month for 3 years, Aquarius will provide an unprecedented new view of the ocean's role in climate. The Aquarius investigation will address these processes on the seasonal cycle as a basis for understanding interannual climate variations.
Sea surface salinity (SSS) is a critical missing parameter that scientists need to meet climate research goals. Measuring global SSS over time will contribute to two of NASA's earth science research priorities:
How is the global Earth system changing?
SSS will tell us how global precipitation, evaporation, and the water cycle is changing. SSS variability is the key tracer for fresh water input to -- and output from -- the ocean associated with precipitation, evaporation, ice melting, and river runoff.
How does the earth system respond to natural and human-induced change?
SSS will help us discover how climate variation induces changes in global ocean circulation. SSS and sea surface temperature -- which together determine seawater density -- regulate ocean circulation and the formation of water masses.
Answering these questions has been difficult because SSS sampling by ships, buoys, drifters, and moorings has been extremely limited. Beginning in 2011, the Aquarius satellite mission will provide monthly maps of global SSS over a three-year period. Thus Aquarius will resolve key physical processes that link the water cycle, climate, and the ocean.
Another important mission objective is demonstrating how monitoring salinity-driven ocean circulation -- and its subsequent feedback on climate and events such as El Niño and La Niña -- can benefit society as whole