Journal of Coastal Research 00 0 000–000 Coconut Creek, Florida Month 0000 Influence of Potential Future Sea-Level Rise on Tides in the China Sea Cuiping Kuang†*, Huidi Liang†, Xiaodan Mao†, Bryan Karney‡, Jie Gu§, Hongcheng Huang†, Wei Chen†, and Honglin Song† †College of Civil Engineering ‡College of Civil Engineering §College of Marine Sciences Tongji University University of Toronto Shanghai Ocean University Shanghai 200092, China Toronto M5S 1A4, Canada Shanghai 201306, China ABSTRACT Kuang, C.; Liang, H.; Mao, X.; Karney, B.; Gu, J.; Huang, H.; Chen, W., and Song, H., 0000. Influence of potential future sea-level rise on tides in the China Sea. Journal of Coastal Research, 00(0), 000–000. Coconut Creek (Florida), ISSN 0749-0208. This study investigates the diurnal and semidiurnal tidal responses of the entire China Sea to a potential rise in sea level of 0.5–2 m. A modified two-dimensional tidal model based on MIKE21 is primarily configured and validated for the present situation; then, three (0.5, 1, 2 m) sea-level rise (SLR) scenarios are simulated with this model. The predicted results show that the principal lunar semidiurnal (M2) and diurnal (K1) tidal constituents respond to SLR in a spatially nonuniform manner. Generally, changes of M2 and K1 amplitudes in shallow waters are larger than those in the deep sea, and significant tidal alterations mainly occur in the Bohai and Yellow seas, Jianghua Bay, Hangzhou Bay, Taiwan Strait, Yangtze River estuary, Pearl River estuary, and Beibu Bay. Possible mechanisms further discussed for these changes mainly relate to bottom friction decreasing, amphidromic point migration, and resonant effect change. Additionally, simulated changes in M2 and K1 amplitudes in response to three SLR scenarios imply that M2 amplitude changes are proportional to the magnitude of SLR, whereas this proportionality does not hold for K1 amplitudes. Identifying the response of tides in the China Sea to SLR not only increases our knowledge of tidal systems, but also assists in setting conservation requirements and management plans in coastal areas. ADDTIONAL INDEX WORDS: Tidal regime change, migration of amphidromes, numerical simulation. INTRODUCTION m global rise in sea level as a pragmatic range for a A rising sea level related to climate change is likely to temperature rise of 48C. redistribute tidal energy and to influence coastal areas SLR has been identified as a major threat to coastal habits strongly. Ocean thermal expansion and glacier mass loss are and communities worldwide. On one hand, SLR itself could the two dominant contributors to global mean sea-level rise greatly increase flood risk and erosion of beaches by elevating (SLR) (Church et al., 2013). The observed average rate of global water levels (Bacopoulos and Hagen, 2014; Brunel and SLR was 1.8 mm/y from 1961 to 2003, but accelerated to 3.1 Sabatier, 2009; Kont, Jaagus, and Aunap, 2003; Snoussi et mm/y from 1993 to 2003 according to the Fifth Assessment al., 2009; Testut et al., 2016) in coastal areas, affecting Report (AR5) of the Intergovernmental Panel on Climate ecosystems, destroying coastal habitats (Kuang et al., 2014; Change (IPCC; Church et al., 2013). Although there has been McInnes et al., 2003; Xie et al., 2015), and endangering the life almost 2000 years of moderate fluctuation in sea level, the and property of coastal dwellers. On the other hand, SLR could expected global SLR is unprecedented (Ward, Green, and interact with tides and storm surges, which are expected to Pelling, 2012). Specifically for the China Sea, an average rate of alter tidal regimes (Passeri et al., 2015; Pelling and Green, 2014; Pickering et al., 2012), contribute to extreme water levels þ3 mm/y was observed from 1980 to 2014 (State Oceanic (Arns et al., 2015; Smith et al., 2010; Warner and Tissot, 2012), Administration, 2015), and sea level in 2012 reached its and have other effects related to saline water intrusion (Chen et maximum at 122 mm higher than the average. This SLR is al., 2016) and coastal structures (Cheon and Suh, 2016; Xie et expected to continue to rise through the 21st century, but its al., 2015). Moreover, morphological changes in barrier islands, value varies with spatial scale and climate change scenario. estuaries, and beaches (Biria et al., 2015; Kuiry, Ding, and Without considering the contributions of ice sheets and glacier Wang, 2014; Nicholls and Cazenave, 2010; van der Wegen, melting, the sea level in the Bohai Sea (BS), Yellow Sea (YS), 2013) may be strongly affected by SLR. and East China Sea (ECS) will rise about 0.12 to 0.2 m (Chen et In practice, the influence of SLR interacting with tides, which al., 2014; Cheng, Xu, and Zhang, 2015). Although global SLR changes tidal dynamics and energy, is more profound than that projections to the late 21st century by the IPCC AR5 range from of SLR itself. A number of modeling studies have been 0.52 to 0.98 m, Nicholls et al. (2010) advocated using a 0.5–2.0- conducted into how past or future SLR interacts with the global tides. On the European Shelf, principal lunar semidiur- DOI: 10.2112/JCOASTRES-D-16-00057.1 received 2 April 2016; nal (M2) tidal amplitude responds to SLR in a spatially accepted in revision 31 May, 2016; corrected proofs received 21 July 2016; published pre-print online 1 September 2016. nonuniform manner with substantial amplitude increases *Corresponding author: [email protected] and decreases as SLR (Pickering et al., 2012), and permanent ÓCoastal Education and Research Foundation, Inc. 2016 flooding of new land significantly alters the response of the 0 Kuang et al. Figure 1. Study domain of the entire China Sea and positions of 39 tide gauges used for model validation. tides to SLR (Pelling and Green, 2014; Ward, Green, and induced circulation and complex bottom topography (Zu, Gan, Pelling, 2012). Specifically, significant increases in extreme and Erofeeva, 2008). For these reasons, researchers have often water levels and frequency of extreme coastal storm surge divided the China Sea into ECS and SCS for numerical analysis events are relative to SLR in both the United Kingdom and of the corresponding tides (Pelling, Uehara, and Green, 2013; Germany (Arns et al., 2015; Lowe, Gregory, and Flather, 2001). Zu, Gan, and Erofeeva, 2008) and have generally agreed on the In SE Louisiana, the increase of surge is as much as double and ECS tidal regime (Cheng, Xu, and Zhang, 2015; Fang, 1986; triple the SLR over broad areas and as much as five times the Lin et al., 1997; Shen, 1980; Wang, Fang, and Feng, 1999; Ye SLR in isolated areas (Smith et al., 2010). Dynamic flooding and Mei, 1995; Ye and Robinson, 1983; Yu and Zhang, 1987; (considered the interaction between tides and SLR) outweighs Zhang, 2005). However, the spatial characteristics of the static flooding (only SLR) by a factor of 4/3–5/3 in Apalachicola amplitude, phase, and amphidromic points in the SCS are still Bay, Florida (Bacopoulos and Hagen, 2014), and the occur- disputed (Fang et al., 1999; Li et al., 2002; Shen et al., 1985; Ye rences of tidal flooding also increase with SLR in Boston (Kruel, and Robinson, 1983; Yu, 1984), particularly the number and 2015). In the China Sea, the effect of SLR on tides has been distribution of amphidromic points associated with the Gulf of investigated in BS (Pelling, Uehara, and Green, 2013) and ECS Thailand. The domains in those studies didn’t cover the entire (Gao, 2008; Yan, Zuo, and Chen, 2010). However, little China Sea, and because their open boundaries are relatively systematic work has been done on the entire China Sea (Figure close to the study area, there is a risk that the boundary 1), which is the goal of the current study. conditions may have unduly influenced the simulation. The entire China Sea (Figure 1) comprises the BS, YS, ECS, Recently, Zhang et al. (2013) developed a numerical model of and South China Sea (SCS). The SCS links with the Java Sea in the NW Pacific, including the entire China Sea, to study both the south, with the Sulu Sea through several narrow channels the tidal system and the tidal changes due to a 0.9-m SLR in the between the Philippine Islands, and directly with the Pacific marginal seas near China. Because only one SLR scenario was through the highly energetic Luzon Strait in the south of considered, the effects of continually changing sea level were Taiwan (Green and David, 2013). The BS has special not considered. Although considerable published work sug- characteristics, being semienclosed by the Shandong, Liao- gests that tidal changes are often proportional to SLR, neither dong, and Korean peninsulas and exchanging energy with YS this assumption nor that of spatial uniformity can be clarified through the Bohai Strait. The regional tidal dynamics in those with a single SLR scenario. Because morphological adjust- areas are complicated because of the different local wind- ments were rarely simulated (Pelling, Uehara, and Green, Journal of Coastal Research, Vol. 00, No. 0, 0000 Influence of Sea-Level Rise on Tides in China Sea 0 2013) and the bottom friction coefficient was usually assumed to be constant (Pelling and Green, 2014; Ward, Green, and Pelling, 2012), other uncertainties were not addressed. This study assesses the potential effect of future SLR on the China Sea, in the first instance by assessing the effect of SLR on the semidiurnal M2 tidal constituent and its diurnal (K1) counterpart. The second objective is to capture the tidal responses along the coastline around Chinese mainland and to evaluate the linearity of the response. To address these objectives, a high-resolution two-dimensional (2D) tidal model based on MIKE 21 Flow Model is developed.