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Science News
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Dr. Gary Lagerloef, island researcher leads study of salinity's effect on cliimate. + View PDF (opens in a new window) |
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.
← Scientist collects seawater for analysis.
Answering these questions has been difficult because SSS sampling by ships, buoys, drifters, and moorings has been extremely limited. Beginning in 2010, however, 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.
Can Sea Surface Salinity monitoring improve ENSO forecasts?
Earth System Science Interdisciplinary Center (ESSIC) : University of Maryland
Glossary Words
atmosphere: Gaseous layer surrounding a planet; the whole mass of air surrounding the earth.
climate: The prevailing or normal pattern of weather at a place, or in a region, averaged over a long period of time; in contrast to weather, which is the state of the atmosphere at a particular time.
conductivity: A measure of the ability of a material to conduct or transmit an electric charge.
density: Mass per unit volume of a substance. Usually expressed as grams per cubic centimeter. For ocean water with a salinity of 35 at 0°C, the density is 1.028 grams per cubic centimeter.
evaporation: The physical process of converting a liquid to a gas. Commonly considered to occur at a temperature below the boiling point of the liquid.
fresh water: Non-saline water.
practical salinity unit (psu): Used to describe the concentration of dissolved salts in water, the UNESCO Practical Salinity Scale of 1978 (PSS78) defines salinity in terms of a conductivity ratio, so it is dimensionless. Salinity was formerly expressed in terms of parts per thousand (ppt) or by weight (parts per thousand or 0/00). That is, a salinity of 35 ppt meant 35 pounds of salt per 1,000 pounds of seawater. Open ocean salinities are generally in the range between 32 and 37.
precipitation: Water released from the atmosphere in the form of rain, snow, hail, or sleet from the atmosphere onto Earth's surface.
runoff: The downward movement of surface water under gravity in channels ranging from small rills to large rivers.
salinity: A measure of the quantity of dissolved solids in ocean water. In general, salinity reflects the total amount of dissolved solids in ocean water in parts per thousand by weight after all carbonate has been converted to oxide, the bromide and iodide to chloride, and all the organic matter oxidized. Salinity is now measured as pratical salinity units (psu).
system: 1) A regularly interacting or interdependent group of items forming a unified whole. 2) A manner of classifying. 3) A group of interacting bodies under the influence of related forces.
tracer: An identifiable substance that can be followed through the course of a physical or biological process providing information on the pattern of events in the process or on the redistribution of the parts or elements involved.
variability: The quality of being subject to change or deviation from a norm or standard.
water mass: A body of water identifiable by its temperature, salinity, or chemical content.
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