Earth’s oceans cover over 70% of the planet, making them challenging to study comprehensively using traditional methods like ships and buoys. Ocean satellites offer a unique perspective, providing global observations otherwise unattainable. Their ability to gather data across entire oceans in a relatively short time allows for a more complete understanding of ocean dynamics and processes. This global monitoring from space enhances oceanographic research and our understanding of the ocean’s influence on Earth’s systems.
What Ocean Satellites Are and How They Work
Ocean satellites are specialized instruments that orbit Earth to collect information about the ocean without direct physical contact, a technique known as remote sensing. These satellites use various sensors to detect and measure different types of electromagnetic radiation, including visible light, infrared, and microwave wavelengths. By analyzing signals from the ocean surface, these sensors can infer various ocean properties.
Satellites employ both passive and active sensors. Passive sensors measure natural radiation emitted or reflected from the sea surface, such as sunlight or infrared radiation for temperature. Active sensors transmit their own signals, like radar pulses or laser beams, then measure the return signal that bounces back. While visible and infrared sensors are limited by cloud cover, microwave sensors can often “see” through clouds, though sometimes with lower spatial resolution.
Many ocean-observing satellites utilize polar orbits, circling Earth from pole to pole at altitudes between 700 to 1000 kilometers (approximately 435 to 620 miles). These orbits provide global coverage as Earth rotates underneath, allowing the satellite to scan different longitudes with each pass. Some satellites also use geostationary orbits, positioned about 35,786 kilometers (22,236 miles) above the equator, appearing stationary over a fixed point and providing continuous monitoring of a specific region.
Key Ocean Measurements from Space
Ocean satellites measure various parameters of the ocean surface. Sea Surface Temperature (SST) is measured using infrared or passive microwave radiometers. Infrared sensors offer higher spatial resolution, around 1 kilometer, while passive microwave sensors have a resolution of about 25 kilometers. SST is important for understanding climate patterns, marine life distribution, and influencing coastal weather.
Sea Surface Height (SSH), also known as sea level, is measured with radar altimeters. These determine the precise distance from the satellite to the ocean surface by timing the travel of a transmitted signal. These measurements are used for monitoring tides, tracking ocean currents, and assessing global sea level rise, which indicates climate change.
Ocean color, observed by visible light sensors, reveals the presence of phytoplankton. These microscopic algae contain chlorophyll and influence the water’s hue from blue to green. This measurement helps scientists assess ocean productivity and identify areas with high biological activity. Changes in ocean color can also indicate water quality issues, such as river plumes or harmful algal blooms.
Ocean currents, while not directly measured, are inferred from combinations of sea surface height and temperature data. Satellite scatterometers, a type of radar sensor, can also measure ocean near-surface wind speed and direction, which drive ocean currents. Salinity, the saltiness of the water, is measured using microwave radiometers and is a factor in ocean circulation and water density.
Sea ice extent and thickness are also monitored by satellites for climate studies and safe navigation in polar regions. Microwave sensors are effective for this purpose, as they can penetrate clouds, offering consistent observations of ice conditions.
How Satellite Data Benefits Humanity
Data collected by ocean satellites benefits human society, from daily weather forecasts to long-term climate monitoring. Satellite-derived sea surface temperature (SST) and sea level data improve weather forecasting, allowing for better prediction of extreme events like hurricanes. This information also helps track large-scale climate phenomena such as El Niño and La Niña, which influence global weather patterns.
Ocean color data helps monitor phytoplankton blooms, the base of the marine food web. This assists scientists in tracking ocean productivity and detecting harmful algal blooms, which can contaminate shellfish and endanger marine life. Such monitoring supports the management of marine ecosystems and understanding environmental changes.
Satellite data also contributes to disaster preparedness and response. Sea level measurements are used in tsunami warning systems, enabling timely alerts to coastal communities. Satellites can detect and track oil spills, providing information that aids in containment and cleanup efforts. This rapid, wide-area coverage is difficult to achieve with other observation methods.
For shipping and navigation, satellite data on currents, wave heights, and sea ice conditions allows for planning safer and more efficient maritime routes. Knowing these conditions helps vessels avoid hazardous areas and optimize fuel consumption. In fisheries management, ocean temperature and chlorophyll concentrations, derived from satellite observations, help identify productive fishing grounds, supporting sustainable practices.
Coastal management also benefits from satellite insights. Satellites monitor coastal erosion, track storm surges, and assess the impacts of sea level rise on vulnerable coastal communities and infrastructure. This allows for informed decision-making regarding coastal protection and adaptation strategies.