Korea’s sea surface rose by 11.5cm since 1989: study

Waters around the Korean Peninsula have crept higher by 11.5 centimeters over the past 35 years, according to a national assessment of sea-level records. The long-term rise is consistent with a warming climate and the expanding, freshening oceans it drives.

The analysis draws on measurements from 21 tide and sea-level stations distributed along Korea’s coasts. On average, sea level climbed about 3.2 millimeters per year between 1989 and 2024, the review found. That rate masks clear regional fingerprints: the East Sea (Sea of Japan) and the Yellow Sea posted faster gains than many parts of the south coast.

Uneven rise along the coasts

Trend lines differ by shoreline. The East and West seas generally rose between 3.0 and 3.6 mm per year, while the southern coast saw a comparatively slower rise ranging from 2.6 to 3.4 mm per year. These variations matter because they shape where flooding, erosion and saltwater intrusion will intensify first.

The timeline also reveals bursts of acceleration. From 1995 to 2004, gauges across all coasts recorded a steep climb—roughly 5 to 8 mm per year. Elevated rates persisted on the east coast through 2005–2014, and then a renewed quickening emerged along the west coast and around Jeju Island from 2015 to 2024. Officials emphasized that sea-level behavior is not uniform and that planning has to reflect local dynamics rather than a single national average.

What’s pushing the water higher?

Multiple climate and ocean processes are at play, combining to lift coastal waters and shape the regional pattern:

• Thermal expansion: As the ocean warms, seawater expands, raising sea level even without adding new water.
• Land ice melt: Glaciers and ice sheets have been losing mass, adding freshwater to the global ocean and nudging levels upward.
• Salinity and circulation shifts: Changes in rainfall, evaporation, river discharge, and large-scale ocean–atmosphere circulation can redistribute water masses and influence regional sea-level trends.

Shorter-term climate variability—such as decadal oscillations in the Pacific—can temporarily speed up or slow down the background rise, helping explain the periods of acceleration found in the Korean record.

Implications for coasts, cities and fisheries

Even a few centimeters of additional water can magnify coastal hazards. Higher baselines mean storm surges and typhoon-driven waves ride in on an already elevated sea, pushing floodwaters farther inland. Low-lying ports, industrial facilities, and wastewater systems face rising maintenance demands, while beaches, tidal flats and salt marshes are squeezed unless they can shift landward.

The new findings are expected to inform flood-risk mapping, design standards for sea walls and harbor structures, and the upkeep of transportation and energy corridors along the coast. Jeju’s exposed shorelines and west-coast mudflats, for instance, may require tailored strategies that reflect their recent rates of rise and local geomorphology. Where land subsidence coincides with rising seas, the combined effect can be especially acute, warranting more conservative safety margins.

Adaptation priorities

• Update elevation and flood maps to reflect recent sea-level trends and acceleration hotspots.
• Revise design heights and lifespans for critical infrastructure, including ports, dikes and drainage systems.
• Preserve and restore natural buffers—dunes, wetlands and tidal flats—that absorb wave energy and store floodwaters.
• Plan for managed retreat or elevation in the most exposed zones, paired with stricter coastal building codes.
• Strengthen early warning and emergency response for compound events where heavy rain, surge and high tides intersect.

The numbers at a glance

• Total rise since 1989: approximately 11.5 cm.
• National mean rate: about 3.2 mm per year (1989–2024).
• East and West seas: roughly 3.0–3.6 mm per year.
• South coast: roughly 2.6–3.4 mm per year.
• Acceleration periods: around 5–8 mm per year across coasts in 1995–2004; continued acceleration on the east coast in 2005–2014; renewed acceleration on the west coast and Jeju in 2015–2024.

The overarching message is clear: sea levels around Korea are rising and, in some places, speeding up. With careful attention to regional differences, the country can translate these measurements into practical protections for communities, ecosystems and the blue economy that depends on them.