Detecting the anthropogenic footprints on sea level over the Southeast Asia region

• Main Author: Sachin, Vairagi Vedant
• Other Authors: Liu Shukui
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Science; Engineering::Mechanical engineering
• Online Access: https://hdl.handle.net/10356/158980
• Institution: Nanyang Technological University

Anthropogenic climate change induced sea level rise exerts significant stress on coastal communities and low-lying islands, particularly in Southeast Asia (SEA). SEA is already exposed to a wide range of natural hazards; sea level rise poses an additional threat to it. It is therefore critical to understand the past sea level changes in SEA, thereby enabling a better understanding of future sea-level projections. However, changes in sea level at the local scale vary from the global scale and are subject to a wide range of driving factors. These driving factors include natural, as well as anthropogenic forcings caused by human influence. However, separating the effects of natural climate variability from anthropogenic forcing on the sea-level rise over the SEA region is not well understood, and still remains a challenge. In this project, I focus on: (1) examining the sea level trend from satellite observations and tide gauge records, and (2) attributing the anthropogenic factors on sea level changes during the historical period (1950-2014) using the Detection and Attribution Model Intercomparison Project (DAMIP) of Coupled Model Intercomparison Project Phase 6 (CMIP6). Based on the availability of at least ten ensemble members across different DAMIP simulations, I selected CanESM5, CNRM-CM6, and IPSL-CM6A models. Using the ensemble mean simulations from these models I studied the attribution of different anthropogenic forcings (e.g., greenhouse gas, aerosol) and natural forcings to address the total historical changes in sea level. I examined the relative changes in thermosteric sea level. Further, I estimated the changes (1985-2014 minus 1950-1979) and trends in the spatial patterns of the dynamic component of sea level. I found that overall greenhouse gas forcing increases the thermosteric and dynamic sea level. Further analysis of surface wind pattern changes suggests the dominance of easterly winds in the eastern Indian Ocean to reduce the dynamic sea level near the Indonesian coast in recent decades. My results provide a comprehensive spatio-temporal understanding of the attribution of anthropogenic factors in sea-level rise over the SEA region. Despite interannual-to-decadal variability, results suggest the dominance of anthropogenic factors and underlying mechanisms in sea-level rise that has occurred in recent decades.