Extreme Sea Level Rise off the Northwest Coast of

J. Ocean Univ. China(Oceanic and Coastal Sea Research)

https://https://www.360docs.net/doc/0017321651.html,/10.1007/s11802-018-3681-9

ISSN 1672-5182, 2018 17 (5): 991-999

https://www.360docs.net/doc/0017321651.html,/xbywb/

E-mail:xbywb@https://www.360docs.net/doc/0017321651.html,

Extreme Sea Level Rise off the Northwest Coast of

the South China Sea in 2012

LIU Lin1), 2), *, LI Juan1), 2), *, TAN Wei3), WU Yue1), LIU Yanliang1), 2),

and WANG Huiwu1), 2)

1) Center for Ocean and Climate Research, First Institute of Oceanography, State Oceanic Administration,

Qingdao 266061, China

2) Laboratory for Regional Oceanography and Numerical Modeling, Qingdao National Laboratory for Marine Science

and Technology, Qingdao 266061, China

3) Laboratory of Marine Science and Numerical Modeling, First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China

(Received September 26, 2017; revised October 10, 2017; accepted October 27, 2017)

? Ocean University of China, Science Press and Springer-Verlag GmbH Germany 2018

Abstract Tide gauge data are used to investigate sea level variability off the northwest coast of the South China Sea (SCS) in 2012, and a significant sea level elevation with a magnitude approaching 79mm is observed. Analysis suggests that an abnormal sea sur-face heat flux and freshwater flux may have contributed to this abnormal rise in sea level, together with the remote influence of an ENSO event. Further investigation shows that the event was dominated by the positive freshwater flux, where large volumes of water entered the ocean, and a maximum is centered to the south of Guangdong province, China. Simultaneously, a positive anomalous heat flux occurred in the northwestern part of the SCS, which is considered to have made a positive contribution to the high local sea level elevation. In addition to the heat flux, the ENSO event also had a significant effect on the event, where the La Ni?a-induced northwest Pacific cyclone contributed to sea level rise over the northwestern SCS through dynamic and thermodynamic interactions. Key words sea level rise; South China Sea; interannual variability; extreme

1 Introduction

The South China Sea (SCS) is the largest marginal sea in the western Pacific region. It connects with the Sulu and Java Seas in the south through shallow passages and with the Pacific Ocean through the Luzon Strait in the north (Fig.1). The SCS is located in a dominant East Asian monsoon region, and local sea level variability is affected by seasonal monsoon wind forcing, which is northeasterly in winter and southwesterly in summer. Previous studies have used satellite observations to analyze the different time-scale features operating in the SCS (Ho et al., 2000a, b; Hu et al., 2001; Liu et al., 2001; Li et al., 2003; Rong et al., 2007).

The rate of sea level rise in the SCS has been faster than the global averaged value, and many studies have been conducted on sea level trend estimations in the SCS using satellite data, gravity data, tide gauge data, and ocean general circulation models (Cheng and Qi, 2007; Rong et al., 2009; Cheng and Qi, 2010; Qiu and Chen, 2012; Cheng et al., 2014). The Pearl River Delta is a highly * Corresponding authors. E-mail: liul@https://www.360docs.net/doc/0017321651.html,

E-mail: twlj0419@https://www.360docs.net/doc/0017321651.html, developed region of China located at the north west of the SCS. It is situated adjacent to Hong Kong and Macau, the two important Chinese administrative regions; it has a high gross national product and has been an economic hotspot for decades. As such, it is a key global megacity region, while its geography makes it highly vulnerable to sea level rise. The China Meteorological Administration (2009) had identified the Pearl River Delta as one of the areas in the country most at risk from rising sea levels due

to the low mean land level. Previous studies concur that sea levels in this area are rising and will continue to do so

in the foreseeable future (Xia et al., 2015); such an oc-currence will cause heavy waterlogging (Xia et al., 2017) and salt water intrusion (Qiu and Zhu, 2015).

On seasonal to interannual time scales, extreme sea level events are usually associated with large-scale ocean dynamics and climate extremes; nevertheless, extreme sea level rise has received little attention to date (Goddard et al., 2015). However, the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) focused on extreme sea level variability under climate change (IPCC, 2013, 2014); extreme sea level rises are predicted to occur more frequently with global warming, and when combined with alterations in high frequency processes, such as eddies and tides, will cause widespread