中国东海海平面变化时空分异、影响机理及风险评估

【作者】 王国栋；

【导师】 康建成；

【作者基本信息】 上海师范大学 ， 环境科学， 2013， 博士

【摘要】 海平面变化的研究主要集中在海平面变化趋势研究、空间分异研究、影响机理研究以及风险评估研究等方面，本文以中国东海作为主要研究区域，对中国东海海平面时空分异规律进行研究，讨论了东海黑潮主轴变异对东海海平面变化的影响，并以上海地区为例，分析中国东海极限海平面变化对沿海城市的淹没风险。基于卫星高度计、验潮站等海面高度数据，讨论中国东海海平面变化多尺度周期、空间分布规律、峰值变化规律等，并对未来变化趋势及未来峰值年进行预测。研究认为，东海海平面具有显著的季节和年际变化趋势，同时也具有30个月，134个月，230个月的周期，其中30个月的周期可能与大气准2年周期振荡（QBO）有关；134个月的周期与太阳黑子的周期相一致；230个月的周期，则与月球赤纬角周期（18.6年）变化相对应。对东海海平面进行空间分析后得出，中国东海长江口附近海域海平面长期处于高位，其增长速度为5.45mm/a，每年夏秋季节该处海平面达到全年高值，若叠加风暴潮和天文大潮的影响，可能对长江三角洲及毗邻地区的生态环境及生命财产安全带来威胁。提取中国东海海平面逐月峰值和平均值数据发现，中国东海海平面逐月峰值变化率均高于平均值变化率。东海峰值在逐年增加，主要表现为海平面的剧烈振荡，全球气候变暖导致的海水热膨胀是造成该振荡的主要原因。通过Winters指数平滑模型进行趋势预测可得，未来海平面变化将保持上升趋势，预计到2015年，海平面将比2006年上升40-50mm左右，到2030年，海平面将比2006年上升140-150mm。从中、大尺度考虑，海平面变化受到PDO、ENSO、太阳黑子等因素的影响，考虑到主周期及上述因素周期的叠加影响，可以推测中国东海海平面变化下一次峰值年为2025年左右。东海黑潮是中国东海海平面变化重要的影响因素，本文基于中国东海温、盐、流速资料等，划定东海黑潮边界，提取东海黑潮主轴，研究海平面变化对东海黑潮主轴变异的响应。研究显示，东海黑潮主轴随季节变化具有明显的摆动特征，其南、北部及中部主轴偏离方向有所不同。夏秋季节，长江冲淡水由于流量、流速的加大，对东海黑潮主轴中间部分的偏离有所贡献，影响深度为100m以浅。随主轴流速的增加，东海黑潮入口处，其左右侧海平面皆出现上升的趋势，而黑潮中部，主轴左侧海平面表现出下降的趋势，而右侧海平面抬升。由于高流速的黑潮水往北输运的过程中，不断与东海陆架水进行能量、质量等的交换，其流速到黑潮中部以后开始出现下降的趋势。随主轴流速下降，左右侧海平面皆出现缓慢下降或不变的特征。基于地面沉降数据、验潮站潮位数据和台风风暴潮相关数据，本文将2025年（峰值年）海平面预测上升值、地面沉降预测值、台风风暴潮最大增水值、天文大潮高潮值的累加作为中国东海海平面极限水位的值，基于前述海平面变化趋势相关预测结果，设置一般台风过境和强台风过境两种情景对上海地区进行淹没风险评估。结果显示，当一般台风过境时，海平面极限水位值未达到上海海堤的高度，如不发生溃堤，不会对上海地区造成较大的淹没风险。当强台风过境时，上海地区将出现漫堤的情况，几乎100%的地区将会被淹没。更多还原

【Abstract】 Research on sea-level change focuses on the studies of the trend, spatialvariation, mechanism of impact and risk assessment of sea-level change, etc. Thepaper defines the East China Sea as a major research area to study the spatial andtemporal variation of sea level in the East China Sea, and discusses the impact ofsea-level change caused by spindle variability Kuroshio on the East China Sea. Then,taking Shanghai as an example, it analyzes the inundation risk of the coastal cityinfluenced by extreme sea-level change on the East China Sea.Based on the sea surface height data from satellite altimeter, tide gauge stations,the paper discusses the sea-level change multiscale cycle, the spatial distribution,and the peak variation in China Sea. It also predicts the future trends and future peakyears of the sea-level change. It is suggested that sea level change on the East ChinaSea has noticeablly seasonal and interannual trends. What’s more, it also has theperiod of30months,134months,230months, in which the30-month period maybe related to quasi two-year cycle atmospheric oscillation (QBO); the134-monthperiod is consistent with the period of sunspot; the230-month period iscorresponding to the declination angle change of the moon cycle (18.6years).After the spatial analysis of the sea level in the East China Sea, the sea level nearthe Yangtze River in the East China Sea waters has remained high for long, whosegrowth rate is5.45mm/a, reaching the maximum in summer and declining year afteryear. Coupled with the impact of superimpose storm surges and astronomical tide, itmay pose a threat to the safety of life and property and the ecological environmentin Yangtze River Delta and its adjacent areas.Based on the monthly and average sea level data of China Sea peak, the studyindicates that the rate of change in the monthly peak level is higher than the averagein the East China Sea. The sea level peak increases every year, which is mainlyembodied by the violent oscillations of sea level. Yet the main reason of theoscillation is thermal expansion of seawater caused by global warming.Based on Winters exponential smoothing model for trend forecasting available, future sea-level change will maintain a rising trend, and it is expected that comparedwith2006, by2015, the sea level will rise by about40to50mm, and by2030, thesea level will rise by140to150mm. From the angel of the medium and large scale,considering the sea-level change influenced by PDO, ENSO, sunspots and otherfactors, and the primary cycle and the impact of the above superimposed cycles, thesea-level change in the East China Sea can be predicted to have the next peak inaround2025.The East China Sea Kuroshio is an important influencing contributor to sea levelchange in the East China Sea. The paper is based on temperature, salinity, velocitydata, etc., boundary delimitation Kuroshio, extract Kuroshio axis, and research onsea-level change in response to variability Kuroshio axis. The study has suggestedthat with different seasons, the Kuroshio axis wobble has obvious and differentcharacteristics of the southern, the northern and central spindle. In summer andautumn, as the flow velocity increases, the middle part of the East China SeaKuroshio axis deviation contributes to and affects the depth of100m. As the spindlevelocity increases, the Kuroshio entrance to both the left and right side of theupward tends to rise in sea level, while sea level at the left side of the Kuroshiocentral spindle is on a declining trend, and the right side of the sea level is on the rise.As the Kuroshio with high speed flows to the north, it continuously exchanges energyand mass with the shelf water in the East China Sea, thus causing a declining speed inthe middle of the Kuroshio. With the declining speed in the main axis, the sea levelsat both sides tend to decline slowly or remain unchanged.Based on the ground-subsidence data, tide gauge data and tidal storm surgedata, with the paper accumulates the predicted rise of the sea level value, the groundsubsidence predictive value, the maximum surge storm values and the astronomicalhigh tide in2025(peak year) as the value of the extreme sea level in the East Chinasea. According to the previous sea-level predictions on the sea level trends, the papersets two scenarios which are the general and the strong typhoons in order to doinundated risk assessment in the Shanghai region. The results show that if a generaltyphoon hits Shanghai and the extreme sea level doesn’t reach the seawall’s height in Shanghai, it will not cause greater inundation risk to Shanghai if it doesn’t dike. If astrong typhoon sweeps Shanghai and overflowing embankment emerges, almost100%of the area will be flooded.更多还原