OPP-PRF Investigating the influence of ocean temperature on Antarctic Ice Sheet evolution during the early to middle Pleistocene

OPP-PRF 研究早更新世至中更新世期间海洋温度对南极冰盖演化的影响

• 批准号: 2139051
• 负责人: Michelle Guitard
• 金额: $ 30.24万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-10-01 至 2023-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2139051&HistoricalAwards=false
• 关键词: OPP; PRF; Investigating; influence; ocean

Antarctic Ice Sheet stability remains a large uncertainty in predicting future sea level. Presently, the greatest ice mass loss is observed in locations where relatively warm water comes into contact with glaciers and ice shelves, melting them from below. This has led researchers to hypothesize that the interactions that occur between the ocean and the ice are important for determining ice sheet stability and that increased warm water presence will accelerate Antarctic ice mass loss and lead to greater sea level rise in the coming century. To better predict future ice sheet behavior, it is critical to understand past ice-ocean interactions around Antarctica, especially during warm periods and at times when Earth’s climate was undergoing major changes. Past Antarctic ice mass and environmental conditions like ocean temperature can be reconstructed using sediments, which capture an environmental record as they accumulate on the ocean floor. By looking at sediment composition and by analyzing geochemical signatures within the sediment, it is possible to piece together a record of climate change on hundred- to million-year timescales. This project will reconstruct upper ocean temperatures and Antarctic ice retreat/advance cycles from 2.6 to 0.7 million years ago, which encompasses the Mid-Pleistocene Transition, a time in Earth’s history that marks the shift from 41-thousand year glacial cycles to 100-thousand year glacial cycles. A record will be generated from existing sediment cores collected from the Scotia Sea during International Ocean Discovery Program Expedition 382. The Mid-Pleistocene Transition (MPT; ~1.25–0.7 Ma) marks the shift from glacial-interglacial cycles paced by obliquity (~41 kyr cycles) to those paced by eccentricity (~100-kyr cycles). This transition occurred despite little variation in Earth’s orbital parameters, suggesting a role for internal climate feedbacks. The MPT was accompanied by decreasing atmospheric pCO2, increasing deep ocean carbon storage, and changes in deep water formation and distribution, all of which are linked to Antarctic margin atmosphere-ice-ocean interactions. However, Pleistocene records that document such interactions are rarely preserved on the shelf due to repeated Antarctic Ice Sheet (AIS) advance; instead, they are preserved in deep Southern Ocean basins. This project takes advantage of the excellent preservation and recovery of continuous Pleistocene sediment sequences collected from the Scotia Sea during International Ocean Discovery Program Expedition 382 to test the following hypotheses: 1) Southern Ocean upper ocean temperatures vary on orbital timescales during the early to middle Pleistocene (2.6–0.7 Ma), and 2) Southern Ocean temperatures co-vary with AIS advance/retreat cycles. Paleotemperatures will be reconstructed using the TetraEther indeX of 86 carbons (TEX86), a proxy that utilizes marine archaeal biomarkers. The Scotia Sea TEX86-based paleotemperature record will be compared to records of AIS variability, including ice rafted debris. Expedition 382 records will be compared to orbitally paced climatic time series and the benthic oxygen isotope record of global ice volume and bottom water temperature to determine if a correlation exists between upper ocean temperature, AIS retreat/advance, and orbital climate forcing.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.

南极冰盖的稳定性仍然是预测未来海平面的一个很大的不确定性。目前，在相对温暖的水与冰川和冰架接触的地方，观察到最大的冰量损失，从下面融化它们。这使得研究人员假设，海洋和冰之间发生的相互作用对确定冰盖稳定性很重要，而增加的温水存在将加速南极冰的质量损失，并导致未来世纪海平面上升。为了更好地预测未来的冰盖行为，了解南极洲周围过去的冰-海洋相互作用至关重要，特别是在温暖时期和地球气候发生重大变化的时候。过去的南极冰量和海洋温度等环境条件可以通过沉积物来重建，沉积物在海底积累时捕获了环境记录。通过观察沉积物的成分和分析沉积物中的地球化学特征，有可能拼凑出数百至数百万年时间尺度上的气候变化记录。该项目将重建260万年至70万年前的上层海洋温度和南极冰退缩/前进周期，其中包括中更新世过渡期，这是地球历史上标志着从41，000年冰川周期转变为10万年冰川周期的时期。将从国际海洋发现计划382考察期间从斯科舍海收集的现有沉积物岩心中生成记录。中更新世过渡期（MPT; ~1.25-0.7 Ma）标志着从由离心率（~41 kyr cycle）决定的冰期-间冰期旋回向由离心率（~100 kyr cycle）决定的冰期-间冰期旋回的转变。尽管地球轨道参数变化不大，但这种转变还是发生了，这表明内部气候反馈的作用。MPT伴随着大气pCO 2降低，深海碳储存增加，以及深水形成和分布的变化，所有这些都与南极边缘大气-冰-海洋相互作用有关。然而，记录这种相互作用的更新世记录很少保存在大陆架上，因为南极冰盖（AIS）的反复推进;相反，它们保存在南大洋盆地深处。该项目利用国际海洋发现计划第382次考察期间从斯科舍海收集的连续更新世沉积物序列的良好保存和恢复，以测试以下假设：1）早更新世至中更新世期间，南大洋上层海洋温度在轨道时间尺度上变化（2.6-0.7 Ma），（2）南大洋温度与AIS进退周期相关。将使用86个碳的四醚指数（TEX 86）重建古温度，这是一种利用海洋古细菌生物标志物的代表。将把斯科舍海TEX 86的古温度记录与AIS变化记录（包括冰筏碎片）进行比较。考察382记录将与轨道节奏气候时间序列和全球冰量和底层水温的底栖氧同位素记录进行比较，以确定上层海洋温度、AIS后退/前进，该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查进行评估，被认为值得支持的搜索.