Törnqvist Torbjörn E, Jankowski Krista L, Li Yong-Xiang, González Juan L
Department of Earth and Environmental Sciences, Tulane University, 6823 St. Charles Avenue, New Orleans, LA 70118-5698, USA.
Key Laboratory of Surficial Geochemistry (Ministry of Education), School of Earth Sciences and Engineering, Nanjing University, Nanjing 210046, China.
Sci Adv. 2020 May 22;6(21):eaaz5512. doi: 10.1126/sciadv.aaz5512. eCollection 2020 May.
Coastal marshes are threatened by relative sea-level (RSL) rise, yet recent studies predict marsh survival even under the high rates of RSL rise expected later in this century. However, because these studies are mostly based on short-term records, uncertainty persists about the longer-term vulnerability of coastal marshes. We present an 8500-year-long marsh record from the Mississippi Delta, showing that at rates of RSL rise exceeding 6 to 9 mm year, marsh conversion into open water occurs in about 50 years. At rates of RSL rise exceeding ~3 mm year, marsh drowning occurs within a few centuries. Because present-day rates of global sea-level rise already surpass this rate, submergence of the remaining ~15,000 km of marshland in coastal Louisiana is probably inevitable. RSL-driven tipping points for marsh drowning vary geographically, and those for the Mississippi Delta may be lower than elsewhere. Nevertheless, our findings highlight the need for consideration of longer time windows in determining the vulnerability of coastal marshes worldwide.
沿海湿地受到相对海平面（RSL）上升的威胁，然而最近的研究预测，即使在本世纪后期预计的高RSL上升速率下，湿地仍能存活。然而，由于这些研究大多基于短期记录，沿海湿地长期的脆弱性仍存在不确定性。我们展示了一份来自密西西比三角洲长达8500年的湿地记录，表明在RSL上升速率超过每年6至9毫米时，湿地在大约50年内会转变为开阔水域。在RSL上升速率超过每年约3毫米时，湿地会在几个世纪内被淹没。由于当前全球海平面上升速率已经超过这一速率，路易斯安那州沿海剩余约15000平方千米的湿地被淹没可能不可避免。RSL驱动的湿地淹没临界点在地理上有所不同，密西西比三角洲的临界点可能低于其他地方。尽管如此，我们的研究结果强调了在确定全球沿海湿地脆弱性时需要考虑更长时间范围的必要性。
