Collaborative Research: Provenance of Alkenones & Holocene Temperature Evolution of the NW Atlantic

合作研究：烯酮的来源

• 批准号: 2018134
• 负责人: Julian Sachs
• 金额: $ 56.59万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-12-01 至 2024-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2018134&HistoricalAwards=false
• 关键词: Collaborative; Research; Provenance; Alkenones; &amp

This project will produce a set of 12 new sea-surface temperature reconstructions along the western North Atlantic to examine the accuracy of alkenone-based ocean temperature records. Temperature data over the past several thousand years show a mismatch between land-, sea-, and climate model-based estimates. Climate models suggest that temperature remained relatively unchanged, while land-based records shows slight warming. Oddly, sea surface temperatures show 4-6°C cooling over the same period of time. But concerns exist about how well these records reflect temperature conditions in the region. Alkenones are produced by algae which may be biased by the temperature of the season when algae are most abundant. They can also be carried to the North Atlantic from elsewhere by ocean currents and reflect temperature conditions of those regions. This study will attempt to resolve these issues by examination of alkenones collected directly in the water column throughout the year and comparing these to alkenones deposited on the seafloor nearby. Hydrogen isotope ratios and radiocarbon data will provide a test of how much material is transported from different sources. Alkenone temperature data will be compared to other temperature proxies (e.g. Mg/Ca of foraminifera) in the region. The project creates significant learning opportunities for middle and high school teachers who will team with scientists in the classroom to develop climate-based curricular instruction and participate in shipboard research during sediment coring operations. It will also provide significant support for undergraduate students and an early career postdoctoral student.The global composite of Holocene temperature proxy records indicates 0.5-1°C of cooling over the last 8,000 years, driven largely by a 2°C cooling in northern hemisphere marine records. Transient climate simulations, however, show no such cooling, and continental temperature records in eastern North America and Europe indicate slight warming. This “Holocene Conundrum” is one of the most prominent unmet challenges facing the climate science community. The northern hemisphere trend is largely driven by 4-6°C cooling in three alkenone SST records from the NW Atlantic. To determine whether this data-model mismatch indicates a gap in understanding of the climate system, these anomalous proxy records must be examined in the context of the factors influencing alkenone deposition in NW Atlantic slopewaters and compared to other SST proxies in the same locations for which samples are not available and analyses are presently lacking. Both deficiencies will be addressed in this research by measuring hydrogen isotope values and radiocarbon ages of alkenones, along with Mg/Ca ratios in planktonic foraminifera, from sediment cores and archived sediment trap samples collected in 2004-2007 in the NW Atlantic slopewater region. Alkenone SST records can be biased by lateral transport of slow-sinking alkenones via surface and abyssal currents, or by seasonal production, both potential causes for the data-model mismatch. This project will take advantage of the large hydrogen isotope gradient in NW Atlantic surface waters to ascertain alkenone synthetic provenance by measuring 2H/1H ratios in alkenones. Provenance will be further assessed by measuring alkenone 14C ages to determine the extent of pre-aging during advection. Comparison of alkenone temperatures and 14C ages to fast-sinking, foraminiferal Mg/Ca temperatures and calcite 14C ages, across a series of locations and depths, with seasonal resolution, will allow for the full characterization of advective or seasonal biasing in either proxy relative to in situ and satellite SSTs. Having established the impact of these potential biases, a robust re-assessment of NW Atlantic Holocene SSTs will be made via 12 new reconstructions (6 each from the two independent proxies) from 6 planned coring sites on depth transects east of New Jersey and Nova Scotia, allowing a possible solution to the “Holocene conundrum”.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

该项目将产生沿北大西洋西部的12个新的海面温度重建，以检查基于烷基的海洋温度记录的准确性。在过去的几千年中，温度数据显示了基于陆地，海上和攀登模型的估计值之间的不匹配。气候模型表明，温度保持相对不变，而陆基记录显示略有变暖。奇怪的是，海面温度在同一时期显示4-6°C冷却。但是对这些记录反映该地区温度条件的良好状况存在担忧。烷烃是由藻类产生的，藻类可能会因藻类最丰富的季节温度而产生。它们也可以通过洋流将它们从其他地方带到北大西洋，并反映这些地区的温度条件。这项研究将试图通过检查全年直接在水柱上收集的烯酮，并将其与沉积在海底附近的海底上的烯烃进行比较来解决这些问题。氢同位素比和放射性碳数据将对从不同来源传输多少材料进行测试。将将烯酮温度数据与该区域的其他温度代理（例如有孔虫的mg/ca）进行比较。该项目为中学和高中教师创造了重要的学习机会，他们将与课堂上的科学家合作，以开发基于气候的现代教学，并在沉积物加油过程中参与船上研究。它还将为本科生和早期职业博士后学生提供重大支持。全新世温度代理记录的全球复合材料表明，在过去的8，000年中，冷却0.5-1°C，主要由北半球海洋中2°C冷却的驱动。但是，瞬态气候模拟在北美和欧洲的瞬时冷却和大陆温度记录表明略有变暖。这个“全新世”难题是气候科学界面临的最突出的未满足挑战之一。北半球趋势在很大程度上是由西北大西洋的三个烷烃SST记录中的4-6°C驱动的。为了确定这种数据模型不匹配是否表明对气候系统的理解存在差距，必须在影响NW大西洋slotewaters中烷酮沉积的因素的背景下检查这些异常的代理记录，并与其他位置的其他SST代理进行比较，而这些样品没有可用和缺乏分析。这两种缺陷将在这项研究中通过测量来自沉积物核心的浮游有孔虫和浮游物有孔虫中的Mg/ca比来解决烯烃的氢同位素值和放射性碳年龄，并从2004-2007在NW Atlantic Slopewater地区收集的木质有孔虫中的Mg/Ca比率。烷酮SST记录可能会因通过表面和深渊电流的缓慢链接烯酮的横向运输或季节性产生而偏向，这都是数据模型不匹配的潜在原因。该项目将利用西北大西洋地表水中的大型氢同位素梯度，以确定烯酮合成来源，通过测量烷烃中的2h/1h比率。将通过测量烷酮14C年龄来进一步评估出处，以确定广告期间的预期范围。将烷酮温度和14C年龄的比较与快速链接，有孔虫Mg/ca温度和钙14C年龄的比较，跨一系列位置和深度以及季节性分辨率的比较，可以使任何与现场和卫星SSTS相对的高级或季节性偏见的全面表征。在确定了这些潜在偏见的影响之后，将通过12个新的重建（来自两个独立的代理来自两个独立的代理人）对新泽西州和新泽西州以东的6个计划的加油地点进行强有力的重新评估，并通过12个新的加油地点（来自两个独立的代理人）进行，从而获得了“统计”，从而获得了“统计”的解决方案，并赢得了统计的范围。通过基金会的智力优点和更广泛的影响评估标准通过评估来支持。