國立成功大學 近海水文中心
Coastal Ocean Monitoring Center, National Cheng Kung University (COMC, NCKU)
Coastal Ocean Monitoring Center, National Cheng Kung University (COMC, NCKU)
Sea-Level Rise
The 2006 documentary An Inconvenient Truth transformed former U.S. Vice President Al Gore into a globally recognized climate advocate. The film won the Academy Award for Best Documentary Feature, and Gore was subsequently awarded the Nobel Peace Prize. After a year of global climate lecture tours, 89% of viewers reported increased climate awareness, and 66% indicated that their perspectives on climate change had changed.
In the context of increasing global attention to climate change, sea level rise (SLR) has gradually emerged as a critical issue affecting coastal cities worldwide, with impacts comparable to other major environmental changes. The Intergovernmental Panel on Climate Change (IPCC) [1] reported in its 2007 assessment that the primary driver of global sea level rise is the melting of ice sheets and glaciers, largely attributed to global warming.
ξ Key concept: The melting of floating sea ice has a negligible impact on sea level due to density differences, whereas the thermal expansion of seawater and the loss of land-based ice sheets are major contributors to global sea level rise.
Schematic diagram of the processes contributing to global sea level change (Source: IPCC, 2007, Sea Level Change).
The IPCC Fourth Assessment Report indicates that global mean sea level rose at an average rate of approximately 3.1 millimeters per year during the period 1993–2003. The IPCC Sixth Assessment Report[2] further indicates that global sea level increased by about 0.2 meters between 1901 and 2018. Since around 2006, the rate of sea level rise has accelerated to approximately 3.7 mm per year, an increase of roughly 0.6 mm relative to the preceding period. The U.S. National Oceanic and Atmospheric Administration (NOAA) projected in 2022 that global mean sea level could rise by 0.4 to 3.7 meters by the year 2150.(Global and Regional Sea Level Rise Scenarios for the United States)[3] Based on IPCC AR6 scenarios, Taiwan’s surrounding seas are projected to experience a sea level rise of approximately 0.5 meters under a 2°C warming scenario, with further exacerbation of land subsidence impacts in coastal regions. Under a 4°C warming scenario, sea level rise may reach approximately 1.2 meters, potentially affecting low-lying areas in Taipei, Yilan, Yunlin, Changhua, Chiayi, Tainan, and Kaohsiung.
Studies on Taiwan’s sea level trends include Doong et al. (2008)[4], who analyzed long-term tide gauge records from Keelung and Kaohsiung and found a decreasing trend before 1975, followed by a significant increasing trend afterward. Huang et al. (2010)[5] combined tide gauge observations and satellite altimetry data and estimated that Taiwan’s sea level rise in 2020 ranged between 3.1 and 4.5 centimeters.
Sea level rise has substantial impacts on human society. In the Pacific Island nation of Fiji (Serua Island), during high tide, seawater can overtop coastal defenses and inundate villages, with floodwaters reaching knee height. Saltwater intrusion into agricultural land prevents residents from cultivating crops, placing both ecosystems and food security at serious risk. As a result, communities have been forced to relocate since 2014. In Taiwan, Taizi Village in Kouhu Township, Yunlin County, has been affected by both land subsidence and sea level rise. In 2022, seawalls were raised to prevent inundation during spring tides. Similar challenges are faced along Taiwan’s western coastal regions, including Changhua, Yunlin, Chiayi, Tainan, and Pingtung.
Sea level rise leads to increased coastal water depth and rising groundwater tables in low-lying areas, affecting agriculture, wastewater systems, and freshwater resources. Extreme high water levels also intensify coastal flooding, alter wetland hydrology and geomorphology, and increase storm surge hazards, thereby impacting flood protection design and coastal resilience, and constraining future coastal development.
Reference
- IPCC, 2007: Sea Level Change.
- IPCC, 2021: Summary for Policymakers, AR6 WGII.
- Global and Regional Sea Level Rise Scenarios for the United States.
- 董東璟、曾國禎、楊益昇，「高雄與基隆長期海水位變動分析」，第 30 屆海洋工程研討會論文集，第 625~630頁 (2008)。
- 黃清哲、許泰文、吳立中，「運用潮位與衛星資料推估海平面變遷量技術之研發(2/2)」，MOEAWRA0990248，經濟部水利署，共 302 頁 (2010)。