Currents and Ocean Circulation
- To develop a comprehensive theory of ocean structure and dynamics,
a wide variety of measurements--including water temperature,
sea level, wind speed, and ocean current speed--must be made in many
places at many times.
- Quantitative measurements form the foundation of modern science.
- Monitoring the dynamics of the oceans helps us to discover how they
interact with and affect landmasses and the atmosphere.
Sea Surface Measurements
- Earth-orbiting satellites--such as TOPEX/Poseidon (and soon to be launched
JASON)--have revolutionized our ability to collect ocean surface data
over large areas of Earth's surface at one time.
- TOPEX/Poseidon measures the height of the sea surface almost everywhere every 10 days.
- Slopes of sea level are used to compute ocean currents.
- Satellites measure sea surface temperature by monitoring
wavelengths emitted by the oceans.
- Satellites can measure the amount of phytoplankton (a significant
link to the ocean food chair) in our oceans by observing the color
of the water.
- Satellites can measure wind speed and direction using a scatterometer,
which measures the roughness of the sea. The stronger the wind, the
rougher the surface.
- Surface measurements made from ships and buoys are extremely important
for ocean science, but are very limited in space and time.
Within the Ocean Measurements
- Science research ships and buoys continue to play an important role
in understanding oceans because they can observe what is happening below
the sea surface.
- New drifting buoys sink to a depth of 1 km, float for a month (collecting
data on currents at that depth), pop up to report their position (via
satellite), then sink again. They last for several years.
Below the Ocean Floor
- The Glomar Challenger, a global-ranging vessel managed by the Scripps
Oceanographic Institute and part of the Deep Sea Drilling Project, explored
what lay beneath the ocean's floor. It featured a deep-sea drilling
rig for obtaining core samples from beneath the ocean floor at depths
up to six kilometers.
- The Ocean Drilling Program (ODP) is currently the largest and most
successful multinational Earth science project.
- The JOIDES Resolution took over the ocean drilling activities of the
retired Glomar Challenger.
- Deep-sea cores have shown changes in climate over the last few million
years, including changes in the thermohaline circulation and its relationship
to ice ages.
- Deep-sea cores have measured the places where old turbidity currents flowed.
- ODP scientists have recovered from cores, fragments of the oldest remaining
seafloor. The sample is about 175 million years old, a relic of the
Middle Jurassic period when the continents were still one large landmass.