Water level changes, subsidence, and sea level rise in the Ganges-Brahmaputra-Meghna delta
Water level changes, subsidence, and sea level rise in the Ganges-Brahmaputra-Meghna delta
复制标题
恒河-雅鲁藏布江-梅格纳三角洲的水位变化、沉降和海平面上升
DOI：
10.1073/pnas.1912921117
复制
发表时间：
2020-01-28
影响因子：
11.1
通讯作者：
Shum, C. K.
中科院分区：
文献类型：
--
作者：
Becker, Melanie;Papa, Fabrice;Shum, C. K.
作为世界上最脆弱的地区之一，恒河-布拉马普特拉河-梅克纳河三角洲对近2亿居民的气候变化适应提出了重大挑战。它通常被认为是一个主要受海平面上升和地面沉降影响的三角洲，即使当地的垂直陆地移动速度仍然不确定。在这里，我们重建了1968年至2012年的水位（WL）变化，使用了一套前所未有的横跨三角洲的101个水位计。在过去的45年里，三角洲的WL增长略快于全球平均海平面（约为2毫米/年）（约为3毫米/年）。然而，从2005年开始，我们观察到三角洲西部的WL上升加速。厄尔尼诺-南方涛动（ENSO）和印度洋偶极子（IOD）变率强烈调节了WL的年际波动，在厄尔尼诺和印度洋偶极子正事件期间WL比平均水平低30 ~ 60 cm，而在拉尼娜年期间WL比平均水平高16 ~ 35 cm。利用卫星测高和WL重建，我们估计1993 - 2012年三角洲沉降的最大预期速率在1 - 7mm /年之间。到2100年，即使在温室气体排放减缓情景（代表性浓度路径[RCP] 4.5）下，沉降也可能使预计的海平面上升翻倍，使整个三角洲的海平面上升幅度达到85至140厘米。该研究提供了由大陆淡水动力、垂直陆地运动和海平面上升引起的三角洲当代相对WL变化的可靠区域估计，为制定气候减缓策略提供了基础。
Being one of the most vulnerable regions in the world, the Ganges-Brahmaputra-Meghna delta presents a major challenge for climate change adaptation of nearly 200 million inhabitants. It is often considered as a delta mostly exposed to sea-level rise and exacerbated by land subsidence, even if the local vertical land movement rates remain uncertain. Here, we reconstruct the water-level (WL) changes over 1968 to 2012, using an unprecedented set of 101 water-level gauges across the delta. Over the last 45 y, WL in the delta increased slightly faster (similar to 3 mm/y), than global mean sea level (similar to 2 mm/y). However, from 2005 onward, we observe an acceleration in the WL rise in the west of the delta. The interannual WL fluctuations are strongly modulated by El Nino Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) variability, with WL lower than average by 30 to 60 cm during co-occurrent El Nino and positive IOD events and higher-than-average WL, by 16 to 35 cm, during La Nina years. Using satellite altimetry and WL reconstructions, we estimate that the maximum expected rates of delta subsidence during 1993 to 2012 range from 1 to 7 mm/y. By 2100, even under a greenhouse gas emission mitigation scenario (Representative Concentration Pathway [RCP] 4.5), the subsidence could double the projected sea-level rise, making it reach 85 to 140 cm across the delta. This study provides a robust regional estimate of contemporary relative WL changes in the delta induced by continental freshwater dynamics, vertical land motion, and sea-level rise, giving a basis for developing climate mitigation strategies.