Towards a Comprehensive Understanding of Changes in the Amazon Hydrological Cycle

在过去十年中，亚马逊盆地经历了洪水（2009年，2012-2014年）和干旱（2005年，2010年）的极端事件。这些事件不仅对亚马逊森林，而且对其人民和经济产生了强烈影响。然而，亚马逊地区未来的气候将如何发展仍然不确定，因为亚马逊地区未来气候模型预测的准确性很低，而且过去自然气候/水文变化的数据只涵盖很短的时期。拟议的研究伙伴关系将用于更好地了解过去旱季长度和降水强度的长期变化及其气候控制。这将通过分析来自亚马逊河漫滩树木的现有和新木材样本的年轮宽度和氧同位素比率来完成。洪泛区树木的年轮宽度将用于重建非洪水期的长度，而我们将使用树木年轮中的氧同位素（d18 O）作为旱季降水d18 O的替代。我们将在位于两个子流域的两个地点进行采样，即中部地区（Solimièes河）和北方子流域（Negro河），通过揭示洪泛平原物种Macrolobium acaciifolium的长时间氧同位素序列，提供对最近变化的长期视角，可追溯到150-300多年前。这将使我们能够从人为影响中解开自然周期，从而使我们能够预测未来的预期。这些预测对巴西人民和经济至关重要。如果自然周期可以解释最近的极端事件，那么在不久的将来，这些极端事件可能会再次减少。如果说最近的极端事件是由于气候系统的大规模变化造成的，如果全球海洋表面温度上升，那么我们可能会在不久的将来看到更多的极端事件。通过回顾300多年来，我们将能够从人为变暖中解开自然循环。在目前的活动NERC赠款（NE/K 01353 X/1），我们正在使用地球系统模型，以帮助解释最近的变化。这一拟议的伙伴关系的一个组成部分是在巴西国家自然保护局联合组织一次“国际树木年轮和同位素讲习班”。本次研讨会的目的是：a）聚集国际研究人员和学生在这个和类似的主题工作，B）确定研究领域的需求和头脑风暴的想法，拿出具体的研究方向，为未来几年，c）（主要是）巴西研究人员和学生在现有的和新的技术和发展领域的能力。

Over the last decade the Amazon Basin has experienced extreme events of flooding (2009, 2012-2014) and droughts (2005, 2010). These events have had strong impacts not only on the Amazon forest, but also on its people and economy. How the climate of the Amazon will develop in the future remains uncertain however, as the accuracy of future climate model predictions for the Amazon is low, and as data on past natural climate/hydrology variability cover only a short period. The proposed research partnership will be used to obtain a better understanding of long-term variability of past dry season length and precipitation intensity, and its climatic controls. This will be done by analyzing ring widths and oxygen isotopic ratios in tree rings from existing and new wood samples from floodplain trees in the Amazon. Ring width from floodplain trees will be used to reconstruct the length of the non-flooded phase, while we will use oxygen isotopes in tree rings (d18O) as a proxy for dry season precipitation d18O. We will carry out sampling at two sites located in two sub-basins, the central region (Solimões River) and the northern sub-basin (Negro River) to provide a long-term perspective on the recent changes by revealing long time series of oxygen isotopes in the floodplain species Macrolobium acaciifolium, extending back more than 150-300 years. This will allow unraveling natural cycles from anthropogenic influences and thus allow us to predict what to expect for the future. Such predictions are of paramount importance to the people and economy of Brazil. If natural cycles explain the recent extreme events, one could expect a decrease again of these extremes in the near future. If the recent extremes are rather due to large-scale shifts in the climate system due to eg. warming of the sea surface temperatures globally, then we may expect more extreme event in the immediate future. By looking back for over 300 years, we will be able to unravel natural cycles from man-made warming. Within the current active NERC grant (NE/K01353X/1) we are using Earth system models to help in the interpretation of the recent changes. An integral component of this proposed partnership is the joint organisation of an "international tree ring and isotope workshop" in Brazil at INPA. The objective of this workshop is to: a) Gather international researchers and students working on this and similar topics, b) Identify research needs in the field and brainstorm ideas to come up with concrete research directions for the next years, c) Capacitate (mainly) Brazilian researchers and students in existing and new techniques and developments in the field.