Projecting Relative Sea Level Rise under Climate Change at the Phrachula Chomklao Fort Tide Gauge in the Upper Gulf of Thailand

Abstract

This study aims to project future sea-level rise (SLR) at the Phrachula Chomklao Fort (PCF) tide gauge station in the Upper Gulf of Thailand (UGoT) using the outputs of 35 climate models under two greenhouse gas concentration scenarios: representative concentration pathway 4.5 (RCP4.5) and RCP8.5. The Linear Scaling method was found to be better than Variance Scaling and Quantile Mapping methods for removing biases in raw Global Circulation Models (GCMs) sea level data. Land subsidence, induced by excessive groundwater abstraction, was found to contribute significantly to SLR during the observed period the PCF gauging station; hence, the effects of land subsidence had to be removed from relative sea level before bias correction. The overall increase in SLR is projected to be 0.94–1.05 mm/year under RCP4.5 and 1.07–1.18 mm/year under RCP8.5 for the twenty-first century in the UGoT. The results suggest that future SLR due to climate change will not be as severe in the study region compared to average global projections. However, land subsidence can amplify future SLR. It is therefore important to regulate groundwater abstraction in the future so that SLR can be restricted. It is even more relevant in the UGoT as the raw water intake from the Chao Phraya River for municipal water supply to Bangkok is close to the estuary, and SLR in the future can pose additional challenges for the water utility.

Changes in slow-onset climate events in Thailand

“…These results are consistent well with previous studies based on tidal gauge and satellite altimetry data demonstrated that the sea level in the Gulf of Thailand and the Andaman Sea has been rising significantly faster than other parts of the Indian and Pacific oceans [51][52][53][54][55][56]. Land subsidence due to excessive groundwater extraction and earthquakes was found to be the main contributor to such a high rise [52][53]57]. By comparison, the average rate of sea level rise in the Andaman Sea was higher than that in the Gulf of Thailand (Fig.…”

“…Salinity at the Samlae pumping station of water supply for Bangkok and its surrounding provinces, which is approximately 96 km upstream of the mouth of the Chao Phraya River, exhibits an increasing trend with statistical significance at a 95% confidence level. Our results are consistent with the observed situation in early 2020 when salt water climbed up the Chao Phraya River and reached the city's main municipal water intake, threatening the quality of the raw water supply [57,[66][67]. Seawater intrusions have frequently occurred in the Gulf of Thailand due to the low-lying area's proximity to the sea and the combined effects of sea level rise, deep well pumping and land subsidence [57,[66][67].…”

“…Moreover, the sea level in the upper Gulf of Thailand, recently projected based on the outputs of 35 climate models under the RCP4.5 and RCP8.5 scenarios, has shown a continuous rise in the 21 st century at comparable rates with the prior work [57]. Further, land subsidence significantly contributes to the sea level increase for the near-future period (2021-2050) [57]. Available studies suggest that long-term sea level rise will cause shoreline recessions and could even result in the flooding of low-lying coastal areas [59][60].…”

“…Future sea level rise under the RCP4.5 and RCP8.5 scenarios compared to today's level for Thailand's coasts was projected to be 35-38 cm for the mid-century and 80-99 cm for the end of the century [58]. Moreover, the sea level in the upper Gulf of Thailand, recently projected based on the outputs of 35 climate models under the RCP4.5 and RCP8.5 scenarios, has shown a continuous rise in the 21 st century at comparable rates with the prior work [57]. Further, land subsidence significantly contributes to the sea level increase for the near-future period (2021-2050) [57].…”

Late Holocene coastal dynamics south of the Chanthaburi estuary, eastern Gulf of Thailand

“…1). In this region, sea level may rise as much as 60 cm until the end of the twenty-first century (Oppenheimer et al, 2019), depending on the global warming scenario used for simulations (Jaroenongard et al, 2021). Such predictions are supported by tide gauge data (Sojisuporn et al, 2013) revealing a sea-level increase of about 5 mm/yr for the period AD 1985–AD 2009, in a similar range as altimetry measurements (Trisirisatayawong et al, 2011).…”