지구온난화에 따른 한반도 주변의 해수면 변화와 그 영향에 관한 연구 Ⅰ

Abstract

The Third Assessment Report(2001) of the Intergovernmental Panel on Climate Change(IPCC) concluded that the global warming will be accelerated during the 21st century due to the human activities. The projected warming will increase the steric sea level rise which have large adverse effects on the natural and human systems in the coastal zone. This study intends to assess the sea level change and potential impacts of the future sea level rise on the coastal zone of the Korean Peninsula in which much socioeconomic activities have been already occurred. The contents of the present study include reviews on climate change and its impact, assessments of the current and future sea level change in the global scale and seas near Korea, and impact assessment methodology. The second year study(2002) will be focused on the impact assessment on the coastal zone of the Korea, especially on the inundation problem on human dimension due to the steric sea level rise, storm surge, and tide. Based on the tide gauge data, IPCC(2001) assessed the global average sea level rise during the 20th century is in the range of 10∼20cm, which is higher than that of 19th century. The contributing elements to the sea level rise are in the order of ocean thermal expansion, melting of glacier, mass balance change of the Greenland and Antarctic ice sheets, and surface and ground water storage and permafrost change. The satellite altimeter data during 1990s shows higher trend than the mean trend of tide gauge data during 20th century. The recent high trend of the sea level rise by the altimetry is not clear whether it represents the recent acceleration of the global sea level, the differences of the two observation methods, or short observation period of altimetry. In the 21st century, the global mean sea level is projected to increase much due to the acceleration of the warming. Based on the 35 IPCC emission scenarios, the sea level rise in the 21st century will be in the range of 9∼88cm with a median value of 48cm. The projected range of the sea level rise is 2.2∼4.4 times higher than that of 20th century. The ocean thermal expansion leads the 21st century sea level rise. The melting of glacier also gives considerable contribution to the 21st sea level rise. The regional distribution of future sea level change will be quite complex because of the regional distribution of thermal expansion, heat transport into ocean interiors, ocean circulation changes by the change of density structure with temperature and salinity changes, horizontal heat transport changes due to the ocean circulation changes, wind field changes to climate change, etc. It is projected that the regional variation will be large compared to the global mean value. The state-of-the-art climate model predictions on the regional distribution of the 21st sea level change show little similarity between models except the Arctic Ocean and Antarctic Ocean. This implies the confidence of current climate model is low in the prediction of the regional distribution of sea level change. In order to investigate the sea level change on the neighboring seas of Korea, the sea level trends of the 65 PSMSL(Permanent Service for Mean Sea Level) tide-station data located at the Korea, Japan, and China are calculated by a simple linear regression after a post-glacial rebound correction(Peltier, 2001). The mean sea level change is 1.63 mm/yr ±2.15 mm/yr, which is in the rage of the IPCC assessment. The analysis of the 23 station at Korea reveals that the East Sea is in the low trend of 0.57 mm/yr than those of the South Sea(3.13mm/yr) and the West Sea(2.64 mm/yr) with an overall mean value of 2.31 mm/yr. However, it is quite questionable that the sea level trends with the tide gauge data on the neighboring seas of Korea relate to global warming because of the relatively short observation period and large spatial variability. In the satellite altimeter data (Topex/Poseidon and ERS), the sea level trend on the East Sea, 4.6mm/yr, is larger than that of the global average value in the 1990s. The region influenced by the warm current in the East Sea shows larger sea level rise. It is not clear whether the high trend with altimeter data on the East Sea is related with the acceleration of sea level rise in the Sea, short response time of the Sea, decadal variability, short duration of the altimeter. Further studies are required to clarify the mechanism on the long-term sea level change in the East Sea. The sea level rise have effects on the inundation and displacement of lowlands and wetlands, coastal erosion, intensification of coastal storm flooding, increase in salinity of estuaries, and salt water intrusion into freshwater aquifers. These physical impacts will spread through the coastal system having a wide range of socio-economic impacts such as crop production loss, declines in land values, changes in human health, deterioration of water and habitat qualities, etc. For the vulnerability assessment on the coastal zone of Korea with high tide and storm surge such as Korea, the sea level scenario should include the sea level change due to tide and storm surge as well as steric sea level rise due to the global warming which is commonly adopted scenario in the vulnerability assessment to future sea level rise. The global mean sea level projection by the climate model seems to be the only alternative in the sea level scenario due to the global warming for the Korean coast because of the low confidence of the regional prediction in sea level change of the current climate model and the difficulty of downscaling based on the observation data. The sea level scenario due to storm surge can be calculated with a numerical model or empirical formula based on the historical data of the typhoon.