Why in news?
NASA recently released a high‑resolution map of the global ocean floor derived from data collected by the Surface Water and Ocean Topography (SWOT) satellite. The map reveals thousands of previously unknown seamounts and undersea features by measuring subtle changes in the height of the sea surface. The findings improve navigation, undersea cable planning and our understanding of ocean circulation and plate tectonics.
Background
SWOT is a joint mission of NASA and the French space agency CNES, with contributions from the United Kingdom and Canada. Launched on 16 December 2022, it is the first satellite designed to survey nearly all of Earth’s surface water — including rivers, lakes and the oceans — with unprecedented precision. The satellite orbits Earth every 21 days and employs a Ka‑band Radar Interferometer (KaRIn) to measure water heights.
The KaRIn instrument uses two antennas mounted on a 10‑metre boom to send and receive microwave pulses at the Ka‑band frequency (around 35.75 GHz). By comparing the phase difference between signals returning to each antenna, it can determine the height of the water surface with centimetre‑level accuracy over swaths up to 50 kilometres wide. SWOT revisits every point on Earth roughly once every two weeks, delivering ten‑times better spatial resolution than previous altimeters.
How does SWOT map the seafloor?
- Sea‑surface height anomalies: Ocean water flows over submerged mountains and trenches, creating small bumps and dips on the sea surface due to variations in Earth’s gravity. By measuring these deviations, scientists can infer the shape of the seafloor far below.
- Improved sensitivity: SWOT’s high resolution enables it to detect seamounts just a few hundred metres tall that were previously invisible to satellites. The new map has identified several thousand such features, increasing the known global seamount count significantly.
- Freshwater monitoring: Beyond oceans, SWOT tracks river widths, lake levels and stream flows across the globe, helping researchers better estimate freshwater availability and flood risk.
Benefits
- Safer navigation and engineering: Accurate seafloor data assist in charting shipping routes, laying submarine cables and avoiding undersea hazards.
- Climate and ocean science: Understanding how seafloor topography influences ocean currents improves climate models and helps predict phenomena like El Niño.
- Hydrology and water management: SWOT’s ability to measure river flow and lake volume changes contributes to water resource planning and flood forecasting.
Conclusion
The SWOT satellite marks a leap forward in observing Earth’s water systems. By linking minute surface‑height variations to hidden undersea landscapes and inland water dynamics, it provides scientists and policymakers with tools to improve maritime safety, understand climate processes and manage scarce freshwater resources.
Source: The Indian Express
