Late Holocene temperature reconstruction from Hawes Water northwest England using chironomid analysis

这项拟议中的研究将使用来自Hawes Water（英格兰西北部一个小型硬水湖）沉积物的摇蚊来重建过去5000年的夏季温度。Chironomids是最广泛使用的温度重建代理之一，因为它们对夏季气温的微小变化反应迅速。它们是古生物研究的理想选择，因为幼虫头部在沉积物中保存得很好，而且许多chironomid分类群对特定的温度范围很敏感。该记录将提供大约30年的分辨率温度，这将是英国这一时期气候变化的第一个高分辨率定量记录，也是英国唯一的高分辨率记录。过去对Hawes Water的研究表明，该地点对气候变化的敏感性，特别是北大西洋环流变化引起的气候变化（Marshall et al., 2007）。从Hawes Water可获得2000年前约14500至5000年的温度记录（b2k）。直到最近，人们一直认为，在全新世晚期（距今5000年至2000年），人类引起的湖水变化（特别是pH值、营养物质和氧气状态）对蠓群的影响越来越大，可能会掩盖和混淆温度效应，从而影响重建并使其不准确（见Velle等人，2010年的讨论）。然而，将利物浦Speke Hall湖（一个富集污染的低氧湖）的chironomid推断温度与过去80年的当地仪器记录进行比较表明，基于chironomid的温度推断模型可以对7月平均气温产生可靠的估计，即使是在重金属和硫污染以及营养状况发生巨大变化的湖泊中也是如此（Lang等人，即将提交）。因此，该项目将把Hawes Water的记录延伸到全新世后期，从英国过去14500年的单一档案中获得第一个完整的高分辨率夏季温度记录。然后，研究将利用重建的温度和现场现有的稳定氧同位素记录来重建过去5000年来古湖泊水的氧同位素值（Marshall et al.， 2007的ISOCHIRO方法）。古湖泊水的同位素值与降水和蒸发源水（即东北大西洋）的同位素值直接相关，Marshall等人（2007）表明，霍伊斯水域全新世早期湖泊水氧同位素值的变化是对北美和芬诺-斯堪的纳维亚前冰川湖泊融水流入北大西洋环流变化的直接下游响应。这项研究的结果将表明在全新世晚期，东北大西洋表层水可能发生的任何变化。对这两个新记录的详细研究将有助于深入了解全新世晚期气候变化的驱动因素。将同位素大气水记录与温度记录进行比较，将表明海洋变化对陆地气候的影响程度，以及气候变化可归因于其他气候驱动因素（如太阳辐照的变化）的程度。Hawes Water完整的全新世温度记录的完成将使时间序列分析成为可能，这将表明在某些海洋记录中确定的全新世气候中固有的周期性是否也可以在陆地气候中看到（Bond等人，1997）。请参阅案例支持以获得完整的参考详细信息。

The proposed research would use chironomid midges from the sediments of Hawes Water, a small hard water lake in northwest England, to reconstruct summer temperatures for the past 5,000 years. Chironomids are one of the most widely used proxies for temperature reconstruction as they rapidly respond to even small changes in summer air temperatures. They are ideal for palaeo studies as the larval heads preserve well in sediments and many chironomid taxa are sensitive to a particular temperature range The record would provide temperatures at a resolution of approximately 30 years and would be the first high resolution quantitative record of climate change during this period from England and the only high resolution record in the UK. Past research at Hawes Water has shown the sensitivity of the site to climate changes, particularly those induced by changes in North Atlantic circulation (Marshall et al., 2007). Temperature records are available from Hawes Water for the period from ca. 14,500 to 5,000 years before 2000 (b2k). Until recently it had been thought that during the later Holocene (5,000 b2k to present) the increasing influence on the midge assemblage of human induced changes in lake water (particularly pH, nutrient and oxygen status) may override and confuse the temperature effect, thus affecting the reconstructions and making them inaccurate (see Velle et al., 2010 for discussions). However, comparisons of chironomid inferred temperature from Speke Hall Lake in Liverpool (an enriched polluted low oxygen lake) with local instrumental records for the last 80 years demonstrate that a chironomid-based temperature inference model can produce reliable estimates of mean July air temperatures, even from a lake experiencing large changes in heavy metal and sulphur pollution and nutrient status (Lang et al., imminent submission). The project will therefore extend the Hawes Water record into this Later Holocene period to produce the first complete high resolution summer temperature record from a single archive for the UK for the last 14500 years.The research would then use the reconstructed temperatures together with an existing stable oxygen isotope record from the site to reconstruct the oxygen isotope values of the paleao lake water (ISOCHIRO method of Marshall et al., 2007) for the last 5,000 years. The isotopic value of palaeo lake water directly links to that of precipitation and that of the source water from which it was evaporated (ie the north east Atlantic) and Marshall et al (2007) have shown that changes in the oxygen isotope values of early Holocene lake waters at Hawes Water were a direct downstream response to changes in North Atlantic circulation due to meltwater influxes from pro glacial lakes in America and Fenno-scandianavia. Results from this research will indicate any changes which may have taken place in the north eastern Atlantic surface waters during the later Holocene. Detailed examination of the two new records will give insight into the drivers of late Holocene climate change. Comparison of the isotopic meteoric water record and the temperature record will indicate the extent of the influence of oceanic changes on terrestrial climate and the extent to which climate change may be attributed to other climate drivers e.g. variations in solar irradiation. Completion of the full Holocene temperature record at Hawes Water will enable time series analysis which will indicate as to whether the inherent cyclicity which has been identified within the Holocene climate in some oceanic records (Bond et al., 1997) is also visible in terrestrial climate.Please see Case for Support for full reference details.