Influence of global teleconnections on Holocene climate in Kamchatka

对过去气候变化的研究，特别是自大约11,000年前最后一个冰河时代(被称为全新世)结束以来发生的气候变化，为未来气候可能如何变化以及海洋环流和气团变化的影响提供了重要的见解。它还提高了气候科学家预测未来气候变化的规模和速度并认识到应对的紧迫性的能力。气象站收集的气候记录没有追溯到足够长的时间，无法捕捉到能够预测未来气候变化所需的自然气候变异性的全部范围。然而，通过研究保存在湖底堆积的泥土中的动植物遗骸，有可能重建数千年来的过去气候。硅藻、淡水微型藻类和不咬人的幼虫(摇蚊)以独特的方式做出反应，这取决于夏季温度或湖水中的相对酸度(PH)或营养物的数量。通过找出今天特定种类的硅藻或摇蚊更有利于哪些温度、pH或营养浓度，我们可以从保存在湖泊沉积物中的这些生物的半化石遗骸中定量地重建过去的环境条件。因此，从湖泊采集的几米长的沉积物岩芯的分析可以每隔1厘米或更小的距离进行切片，并使用放射性碳来确定年代，以提供数千年来过去气候变化的非常详细的记录。在这个项目中，我们建议对以前从俄罗斯远东堪察加半岛采集的三个岩芯中的蚊虫和硅藻进行分析。堪察加是了解北大西洋和北太平洋区域之间气候联系程度的关键区域，因此是推动全球气候变化的一些最重要的方式。然而，由于只完成了几项研究，人们对该地区全新世期间的气候变化知之甚少。我们将以40-80年的时间间隔对全新世大部分时间内的三个沉积岩芯中的蚊虫进行分析。我们将使用从整个俄罗斯北部的蚊子的现代分布记录中开发出来的‘蚊子温度计’来重建全新世夏季的气温。我们还将使用这些蚊虫记录来重建过去大陆或海洋性的变化。大陆性气候受横扫欧亚大陆北部的西风的相对影响，西风带来寒冷的冬季、短暂的温暖夏季和较少的降雨，而更具海洋性的气候则受到太平洋风的影响，太平洋风带来了更温和的冬季、更凉爽的夏季和更多的降雨。同样，我们将使用来自相同岩心的硅藻来量化夏季长度的变化，以及pH值或营养物质的任何变化。该项目的一个创新方面将是分析稳定的氧同位素，这些氧同位素被结合到蚊头的几丁质角质层中。氧气是甲壳素分子的一部分，来自蚊子生活的水。我们预计，结合在蚊头中的稳定氧同位素的比率将反映蚊子活着时的水源。在非蒸发湖泊中，这将告诉我们哪些气团推动了当时的主流气候(即，要么来自欧亚大陆，要么来自北太平洋)。通过将我们的记录与北大西洋地区、欧亚大陆、阿拉斯加和北太平洋其他地点提供的全新世气候记录进行比较，我们将能够确定不同气候制度时期全球气候联系的范围，例如全新世最高温度和小冰期的规模和时间。

The study of past climate change, especially that which has occurred since the end of the last ice age about 11,000 years ago (the period known as The Holocene), provides important insights into how climate may change in the future and the influence of changes in ocean circulation and air masses. It also improves the ability of climate scientists to predict the scale and rapidity of future climate change and recognise the urgency to respond. Climate records collected at weather stations do not extend back long enough in time to capture the full extent of natural climate variability needed to be able to predict future climate change. However, it is possible to reconstruct past climate over thousands of years by studying the remains of plants and animals preserved in the mud that accumulates at the bottom of lakes. Diatoms, freshwater microscopic algae, and the larvae of non-biting midges (chironomids) respond in characteristic ways depending on summer temperatures or the relative acidity (pH) or amount of nutrients in the lake water. By finding out which temperatures, pH or nutrient concentrations are favoured by particular species of diatoms or chironomids today we can reconstruct quantitatively past environmental conditions from the semi-fossilised remains of these creatures, which are preserved in lake sediments. Thus analysis of a sediment core several metres long taken from a lake can be sliced at intervals of 1 cm or less and dated using radiocarbon to provide a highly detailed record of past climate change over thousands of years. In this project we propose to analyse midges and diatoms from three cores previously collected from Kamchatka in the far east of Russia. Kamchatka is a key region for understanding the extent of climate linkages between the North Atlantic and North Pacific regions, and hence some of the most important ways in which global climate change is driven. However, climate variability during the Holocene in this region is poorly understood as only a few studies have been completed. We will analyse midges from our three sediment cores over most of the Holocene at intervals of 40-80 years. We will use a 'midge thermometer' developed from modern distribution records of midges from throughout northern Russia, to reconstruct Holocene summer air temperatures. We will also use these midge records to reconstruct past changes in continentality or conversely oceanicity. A continental climate is governed by the relative influence of westerly winds blowing across northern Eurasia, which brings cold winters, short warm summers and less rainfall, whereas a more oceanic climate is influenced by Pacific winds which bring milder winters, cooler summers and more rain. Similarly, we will use diatoms from the same cores to quantify changes in the length of the summer and also any changes in pH or nutrients. An innovative aspect of this project will be to analyse the stable oxygen isotopes that are incorporated into the chitinous cuticle of the midge heads. Oxygen forms part of the chitin molecule and is derived from the water in which the midges are living. We expect that the ratio of stable oxygen isotopes incorporated into the midge heads will reflect the source of the water when the midge was alive. In non evaporative lakes this will tell us which air masses were driving the prevailing climate at that time (i.e. either from Eurasia or the North Pacific). By comparing our records with Holocene climate records available from other sites in the North Atlantic region, Eurasia, Alaska and the North Pacific we will be able to establish the extent of global climate links at times of different climatic regimes, for example the magnitude and timing of the Holocene Thermal Maximum and the Little Ice Age.