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.

南极冰盖稳定性在预测未来的海平面仍然是一个很大的不确定性。目前，在相对温水与冰川和冰架接触的地方观察到最大的冰量损失，从下方融化它们。这导致研究人员假设海洋与冰之间发生的相互作用对于确定冰盖稳定性至关重要，并且增加温水的存在将加速南极冰质量损失，并导致下个世纪的海平面上升。为了更好地预测未来的冰盖行为，重要的是要了解南极围绕的过去的冰山相互作用，尤其是在温暖的时期，有时候地球气候正在发生重大变化。可以使用沉积物重建过去的南极冰块和海洋温度（例如海洋温度），它们在堆积在海底时捕获了环境记录。通过查看沉积物成分并分析沉积物中的地球化学签名，可以将气候变化的记录汇总在数百万到百万年的时间表上。该项目将重建上海温度和南极冰撤退/前进周期从2.6万年前重建，涵盖了中期过渡，这是地球历史上的时代，标志着从41千年的冰川周期转变为100千年的冰川周期。国际海洋发现计划探险期间从斯科舍省（Scotia Sea）收集的现有沉积物核心将产生记录382。中期过渡（MPT; 〜1.25–0.7 mA）标志着从斜斜率（通过倾斜）（〜41 Kyr Cycles）转移到那些eccecenticity（〜41 Kyr Cycles）的转变（〜41 Kyr Cycles）的转变（尽管地球轨道参数变化很小，但这种过渡还是发生了，这表明内部气候反馈的作用。 MPT伴随着降低大气PCO2，增加了深海碳的储存，以及深水形成和分布的变化，所有这些都与南极边缘大气 - 冰冰球相互作用有关。但是，更新世记录，由于反复的南极冰盖（AIS）的前进，很少保留这种相互作用在架子上。取而代之的是，它们被保存在南部的深海低音中。该项目充分利用了国际海洋发现计划探险计划中从斯科舍省海上收集的连续更新世沉积物序列的出色保存和恢复382来测试以下假设：1）南部海洋上海上温度在轨道上的时间尺度上在轨道上早期早期到中期早熟时（2.6-0.7 MA）（2.6-0.7 MA），以及2.6-0.7 MA），以及2.6-0.7 MA），以及2.6-0.7 MA）的范围（2.6-0.7 MA），以及2.6-0.7 MA）的高度均可替代。古植物将使用86个碳（TEX86）的三脑指数重建，该指数是使用海洋古细菌生物标志物的代理。将基于斯科舍省Tex86的古温率记录与AIS变异性的记录进行比较，包括冰筏碎片。 Expedition 382记录将与轨道节奏节奏的气候时间序列以及全球冰量和底部水温的底栖氧同位素记录进行比较，以确定在海洋温度，AIS撤退/前进和轨道气候强迫之间是否存在相关性。这项奖项反映了NSF的法定任务，反映了通过评估范围的cr Infectia crotial and Foundical croitial and Funditial的支持。