Most oceanographers try to think of the world's oceans as one giant system, collectively known as the global ocean. But before space travel and the inventio of satellites, it was very hard to actually observe the oceans on such a large scale. Pictures of the global ocean from space have given oceanographers important information about ocean currents, temperatures, and other properties. Satellites collect information around the clock and feed it back to earth -- and individual laboratories and classrooms -- in real time. This innovation has revolutionized oceanography and given researchers important information about weather and climate, circulation, and environmental problems, such as global warming, global circulation, the world's fisheries decline, and harmful algal blooms.

Perhaps more than any other group of oceanographers, physical oceanographers have benefited from satellite technology. Because they study the movement of the oceans and the forces that cause motion, such as winds, waves, and tides, they must look at the ocean from a "big picture" perspective. Shipboard measurements and the development of instruments such as computer programmable buoys that can be left at sea for long periods of time were huge advances for the field of physical oceanography and continue to be important tools, but satellites offer perspectives that early oceanographers may never have dreamed of. Imagine the discoveries Benjamin Franklin, the first person to plot the course of the Gulf Stream, could have made if he'd had access to satellite data!

Physical oceanographers study the interaction between the ocean and its boundaries -- land, seafloor, and atmosphere -- and the relationship between the sea, weather, and climate. Questions about how the oceans work in a physical sense include investigations into water qualities such as temperature, salinity, density, and influential factors such as wind speed, air temperature, tides, and interaction with nearby land and underwater formations.

Physical oceanographers seek to understand why, where, and how water moves, on all space and time scales. They are interested, too, in the consequences of these movements. Some physical oceanographers are theoreticians and use computer models to answer questions and form hypotheses about oceanographic processes. Others use observations and, increasingly, satellite observations. Understanding the global ocean requires a close partnership between theory, observations, and experiments.

Often, physical oceanographers work with their biological, chemical, and geological colleagues. Understanding the way the ocean works, physically, supplies oceanographers in the biological, geological, chemical, or engineering disciplines with important details they need to answer questions. The physical properties of the ocean are intimately linked to the biology and chemistry of the ocean, and vice-versa.

For example, physical oceanographers are currently working with biological oceanographers and ocean engineers in a multi-institution, multi-agency research initiative knows as ECOHAB (short for ecology of harmful algal blooms). The Gulf of Maine portion of the ECOHAB project is seeking to determine the source and distribution of Alexandrium cells (Alexandrium is the organism that causes paralytic shellfish poisoning, PSP, and is considered one of several harmful algal blooms, once referred to as "red tide."), and the role of ocean currents and plumes in transporting the cells to nearshore areas where they "bloom" and become toxic, poisoning shellfish. The role of physical oceanographers is to assist with oceanographic and satellite measurements, computer modeling, and instrument design, deployment, and recovery. The collaboration continues, with the ultimate goal of, one day, being able to predict toxic bloom events.

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