Sea Level Rise
Sea level rise is the long-term increase in the average height of the global ocean surface, driven primarily by thermal expansion of warming seawater and the melting of glaciers and ice sheets. It poses significant threats to coastal communities, ecosystems, and infrastructure worldwide through increased flooding, erosion, and saltwater intrusion into freshwater systems. Monitoring sea level change is critical for climate adaptation planning and understanding the pace of anthropogenic climate change.
Key Formula
Total SL change = thermal expansion + meltwater contribution + dynamic effects
LaTeX: \Delta SL = \Delta SL_{\text{thermal}} + \Delta SL_{\text{melt}} + \Delta SL_{\text{dynamics}}
| Symbol | Meaning | Unit |
|---|---|---|
| \Delta SL | Total sea level change | mm |
| \Delta SL_{\text{thermal}} | Contribution from thermal expansion of ocean water | mm |
| \Delta SL_{\text{melt}} | Contribution from melting glaciers and ice sheets | mm |
| \Delta SL_{\text{dynamics}} | Contribution from ocean circulation dynamics | mm |
Worked Example
Problem
Between 1993 and 2023, satellite altimetry recorded a mean global sea level rise of approximately 101 mm. Thermal expansion contributed 42 mm, glacier melt contributed 32 mm, Greenland ice sheet loss contributed 15 mm, and Antarctic ice sheet loss contributed 8 mm. What percentage of the total rise is attributed to ice melt sources combined?
Solution
Step 1: Sum all ice melt contributions. Glacier melt + Greenland + Antarctica = 32 + 15 + 8 = 55 mm Step 2: Calculate percentage of total rise. Percentage = (55 / 101) × 100 Step 3: Evaluate. Percentage = 0.5446 × 100 ≈ 54.5%
Answer
Approximately 54.5% of the 101 mm total sea level rise is attributed to combined ice melt sources.
Observed Global Mean Sea Level Rise Rates by Era
| Time Period | Mean Rate (mm/yr) | Primary Driver | Data Source |
|---|---|---|---|
| 1901–1990 | 1.4 | Thermal expansion | Tide gauges |
| 1993–2010 | 3.1 | Thermal + glacier melt | Satellite altimetry |
| 2010–2020 | 4.5 | Ice sheet acceleration | Satellite altimetry |
| 2020–2030 (projected) | 5–7 | Ice sheet dynamics | IPCC AR6 projections |
| 2100 (high scenario) | 60–110 cm total | All sources | IPCC AR6 SSP5-8.5 |
Interactive Tools
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Related Terms
Ocean Acidification
Ocean acidification is the ongoing decrease in the pH of Earth's oceans caused by the absorption of atmospheric carbon dioxide (CO₂), which reacts with seawater to form carbonic acid. Since the Industrial Revolution, ocean surface pH has dropped from approximately 8.2 to 8.1, representing a 26% increase in hydrogen ion concentration. This process threatens marine organisms, especially those that build shells or skeletons from calcium carbonate, such as corals, mollusks, and certain plankton species.
Deforestation
Deforestation is the large-scale removal or clearing of forests, primarily by human activities such as agricultural expansion, logging, urbanisation, and infrastructure development, resulting in the permanent conversion of forested land to non-forest use. Global forests store approximately 861 billion tonnes of carbon, and their destruction releases vast quantities of CO₂, contributing around 10–15% of annual global greenhouse gas emissions. Beyond carbon emissions, deforestation drives soil erosion, loss of biodiversity, disruption of water cycles, and the degradation of ecosystem services that support billions of people globally.
Air Pollution
Air pollution is the presence of harmful substances in the atmosphere — including particulate matter (PM2.5, PM10), nitrogen oxides (NOₓ), sulfur dioxide (SO₂), carbon monoxide (CO), ozone (O₃), and volatile organic compounds (VOCs) — at concentrations that pose risks to human health, ecosystems, and climate. The World Health Organization (WHO) estimates that air pollution causes approximately 7 million premature deaths annually, making it the world's largest environmental health risk. Sources range from vehicle emissions, industrial combustion, and agricultural burning to natural events such as wildfires and volcanic eruptions.
From Old English "sæ" (sea, ocean) and Latin "nivellum" (level, from "libella", a small balance or level). The compound phrase entered scientific usage in the 19th century as tide gauge networks began systematic ocean height measurements.