德国赫姆霍兹中心Blanchet, Cecile L.及其团队成员在研究北非湿润期极端尼罗河洪水的气候步调中取得新进展。这一研究成果于2024年7月3日发表在国际顶尖学术期刊《自然—地球科学》上。

团队人员展示了一份长达1500年的年度层压(varved)近海沉积物记录，该记录追踪了北非湿润期尼罗河的季节性流量。记录显示，在夏季洪水期间大量沉积物被移动起来，这可能使尼罗流域不在适于居住。在9200至8600年的极端强洪水和弱洪水之间更加频繁和快速的转变表明，河流动力学高度不稳定。

气候模拟表明，在年际时间尺度上，洪水变化受厄尔尼诺/南方涛动现象的影响，多年代际振荡模式驱动了极端洪水事件的变化。这些起步点也在同等时代的尼罗河流量记录中被发现，这意味着它们在不同的水文气候条件下是稳定的。

据介绍，了解在全球气温升高的情况下，大型河流系统将如何对活跃的水文循环做出反应是一个紧迫的问题。通过研究过去比现在更湿润的时间间隔，例如全新世早期(约11-6万年前)的北非湿润期，可以获得更多的见解。

附：英文原文

Title: Climatic pacing of extreme Nile floods during the North African Humid Period

Author: Blanchet, Cecile L., Ramisch, Arne, Tjallingii, Rik, Ionita, Monica, Laruelle, Louison, Bagge, Meike, Klemann, Volker, Brauer, Achim

Issue&Volume: 2024-07-03

Abstract: Understanding how large river systems will respond to an invigorated hydrological cycle as simulated under higher global temperatures is a pressing issue. Insights can be gained from studying past wetter-than-present intervals, such as the North African Humid Period during the early Holocene Epoch (~11–6 thousand years ago). Here we present a 1,500-year-long annually laminated (varved) offshore sediment record that tracks the seasonal discharge of the Nile River during the North African Humid Period. The record reveals mobilization of large amounts of sediments during strong summer floods that may have rendered the Nile valley uninhabitable. More frequent and rapid transitions between extremely strong and weak floods between 9.2 and 8.6 thousand years ago indicate highly instable fluvial dynamics. Climate simulations suggest flood variability was paced by El Nino/Southern Oscillation on interannual timescales, while multi-decadal oscillatory modes drove changes in extreme flood events. These pacemakers have also been identified in the Nile flow records from the Common Era, which implies their stationarity under contrasting hydroclimatic conditions.

DOI: 10.1038/s41561-024-01471-9

Source: https://www.nature.com/articles/s41561-024-01471-9