Fingerprinting 'El Nino Costero': a unique opportunity to document the signature of an extreme flood event in northern Peru

秘鲁的北方海岸一直在经历非常温暖（4- 5摄氏度）的海面温度（SST）。2017年3月26日，秘鲁北方的里约皮乌拉河决堤，造成人员死亡、流离失所和基础设施受损。秘鲁与厄尔尼诺-南方涛动（ENSO）密切相关：渔民在19世纪末首次在秘鲁北海岸发现厄尔尼诺现象。驱动当前急性降雨事件的现象被称为“厄尔尼诺Costero”或沿海厄尔尼诺，但不是厄尔尼诺本身，因为它不是由太平洋中部的异常SST（厄尔尼诺3.4）驱动的，这通常定义了厄尔尼诺的开始。相反，它代表了更多的地方性（厄尔尼诺1 +2）厄尔尼诺现象，最后一次出现在1925年，这被认为是20世纪世纪最强烈的洪水。尽管秘鲁为2016年的全球厄尔尼诺做好了准备，但该国似乎被突然从拉尼娜干旱转变为厄尔尼诺Costero的强降雨所淹没，这表明这种类型的本地驱动的厄尔尼诺事件迄今为止一直被忽视。必须在厄尔尼诺/南方涛动的同时建立厄尔尼诺/科斯特罗的记录，特别是因为1925年的事件是有记录以来最极端的事件。如果当地的SST导致厄尔尼诺现象，并在北方秘鲁的气候动态中发挥重要作用，但到目前为止一直被忽视，那么我们对热带太平洋气候变化没有充分的了解。了解赤道太平洋气候变化的关键是反映厄尔尼诺型行为的极端洪水事件的记录，特别是厄尔尼诺Costero如何适应更广泛的气候状况。这一提议是基于一个独特的机会，可以量化和确定大规模洪水的动态和演变，并利用其沉积特征，加上过去120年的气候数据，明确识别和校准最近湖泊沉积物中过去的厄尔尼诺事件。我们将（a）对里约皮乌拉集水区内作为洪水和沉积物储存库的湖泊进行地球物理调查，我们将查明现代洪水沉积物并确定其深度和范围;（B）恢复和调查与洪水有关的表层沉积物，利用粒度、地球化学和矿物磁性来确定其洪水特征;（c）从我们的调查湖泊中恢复短沉积物岩心并测定其日期，并将2017年厄尔尼诺Costero的洪水特征与1925年事件直接进行比较，并将其置于20世纪ENSO变化的背景下。我们的研究将提供一个框架，重建厄尔尼诺有关的洪水事件，从湖泊沉积物在最近的过去在北方秘鲁，但有可能建立一个更长期的（全新世和更老）的历史，所有厄尔尼诺在该地区的变化。

The northern coast of Peru has been experiencing anomalously warm (4-5C) sea surface temperatures (SST). These high SSTs have produced intense and prolonged rainfall that has resulted in extensive flooding, and on the 26th March 2017, the Rio Piura in northern Peru burst its banks leading to loss of life, displacement of people and damaged infrastructure. Peru is intimately linked to the El Niño-Southern Oscillation (ENSO): fishermen first identified El Niño in the late 19th Century off the north coast of Peru. The phenomenon driving this current acute rainfall event has been dubbed 'El Niño Costero' or Coastal El Niño, but is not El Niño per se as it is not being driven by anomalous SSTs in the central Pacific (Niño 3.4), which generally defines the onset of El Niño. Rather it represents more local (Niño1+2) El Niño-like conditions last known to have occurred in 1925, which is considered the most intense flooding of the 20th Century. Despite Peru's preparedness for the global El Niño in 2016, the country appears to be overwhelmed by the sudden shift from La Niña drought to the intense rainfall of El Niño Costero, suggesting this type of locally driven El Niño event has hitherto been overlooked. It is essential to establish a record of El Niño Costero alongside ENSO, especially as the 1925 event was the most extreme on record. If local SSTs cause El Niño-like conditions and play an important part in climate dynamics in northern Peru, but have so far been overlooked, then we don't have a full understanding of tropical Pacific climate change. Critical to understanding equatorial Pacific climate change are records of extreme flood events that reflect El Niño-type behavior, and in particular how El Niño Costero fits within the wider climate picture. This proposal is based on a unique opportunity to quantify and determine the dynamics and evolution of a large magnitude flood, and to use its sedimentary signature, coupled to climatological data over the last 120 years, to unequivocally fingerprint and calibrate past El Niño-type events in recent lake sediments. We will (a) undertake a geophysical survey of lakes in the Rio Piura catchment that act as repositories of flood-waters and sediments, and we will identify modern flood sediments and determine their depth and extent; (b) recover and survey surface sediments related to flooding to characterize their flood signature using grain size, geochemistry and mineral magnetics; (c) recover and date short sediment cores from our survey lakes and directly compare the flood signature of the 2017 El Niño Costero to the 1925 event, as well as putting it in the context of 20th Century ENSO variability. Our study will provide a framework for reconstructing El Niño-related flood events from lake sediments over the recent past in northern Peru, but has the potential to establish a much longer-term (Holocene and older) history of all El Niño variability in the region.