Collaborative Research: Dynamics of the 41-Ka Climate Cycle: Ice Volume and Insolation Forcing

合作研究：41-Ka 气候周期的动态：冰量和日照强迫

• 批准号: 0455470
• 负责人: Eli Tziperman
• 金额: $ 24.49万
• 依托单位: Harvard University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-05-15 至 2009-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0455470&HistoricalAwards=false
• 关键词: Collaborative; Research; Dynamics; 41; Ka

This project will investigate physical mechanisms responsible for the 41,000-year (41-Ka) cycle in late Pliocene and early Pleistocene climate records. Previously, the researchers showed that the observed 41-Ka cycle in ice volume was forced by the equator to pole gradient in solar insolation, which controlled the meridional atmospheric heat and moisture fluxes which ultimately influenced the growth and decay of ice sheets. However, when investigating this hypothesis further using a simple coupled climate-ice model, they found that the model still fails to produce reasonable amplitude 41-Ka oscillations, and exhibits far more precessional power than do benthic foraminifera oxygen isotope signals or ice rafted debris (IRD) records (presumably due to the strong influence of summer insolation on ablation). When these data were combined with other data from other areas of the world, the analysis prompted the researchers to consider the following science questions. * Why is modeled Northern hemisphere ice volume so small when glacial tillite deposits show ice reaching as far south as 35 degrees North latitude? Do we have problems with the models or with the interpretation of the data? * If there was a large (aerially-expansive), low elevation ice sheet on North America, ice sheet-climate models suggest it would have a large ablation zone. Why then do we not see a stronger precession signal in benthic foraminfera oxygen isotope records as ice sheet models suggest? * Could it be that the 41-Ka oscillations are due to a mechanism internal to the climate system, rather than exist only due to Milankovitch forcing? To determine whether there is a precessional component to ice sheet variation on North America, the researchers will generate a benthic isotope stratigraphy for site 625 (Gulf of Mexico) which records meltwater pulses in planktonic foraminfera oxygen isotope records to provide a constraint on the frequency history of North American glaciation in the late Pliocene and early Pleistocene and, by extension, a constraint for ice sheet modeling. The researchers aim to develop a new coupled climate-ice sheet model and use it to investigate different scenarios for the 41-Ka oscillations, and use the model results to reanalyze the proxy records with the objective to determine if the 41-Ka oscillations exist due to Milankovitch forcing, or are internal (self-sustained) oscillations only influenced (phase locked) by Milankovitch forcing. The researchers also will investigate the possible contribution by the Antarctic ice sheet to changes in global ice volume in the late Pliocene and early Pleistocene.This project involves highly interdisciplinary research and enlists the fields of paleoclimate, atmospheric dynamics, physical oceanography, and climate modeling in pursuing a fundamental line of inquiry in natural climate variability. The project will support a graduate student and post-doctoral scholars working collaboratively across disciplinary boundaries and with colleagues in Norway, thus fostering a scientific collaboration between research communities in the U.S. and Norway.

该项目将调查导致上新世和早期更新世气候记录的41，000年（41 ka）周期的物理机制。 以前，研究人员表明，赤道在冰容量中观察到的41 ka循环在太阳日光下迫使极梯度，这控制了子午大气热和水分通量，最终影响了冰盖的生长和衰变。 但是，当使用简单的耦合气候冰模型进一步研究这一假设时，他们发现该模型仍然无法产生合理的幅度41 ka振荡，并且表现出比底栖有孔虫氧同位素或冰筏碎屑（ ird）记录（大概是由于夏季日光浴对消融的强烈影响）。 当这些数据与世界其他领域的其他数据结合在一起时，该分析促使研究人员考虑以下科学问题。 *当冰川植物沉积物显示冰的北纬至35度时，为什么建模的北半球冰量这么小？ 我们对模型有问题或数据解释吗？ *如果北美有一个较大的（空气表达），低海拔冰盖，则冰盖气候模型表明它将具有较大的消融区。 那么，为什么我们看不到像冰盖模型所建议的底栖有孔虫氧同位素记录中更强烈的进动信号？ *可能是41 ka振荡是由于气候系统内部机制引起的，而不是仅由于米兰科维奇强迫而存在？ 为了确定北美的冰盖变化是否存在前期成分，研究人员将为625（墨西哥湾）生成底栖同位素地层，该地层记录了浮游生物有孔虫氧气中的融合水脉冲，以提供对频率历史记录的约束北美晚期和早期更新世的北美冰川化以及冰盖建模的限制。研究人员的目的是开发新的耦合气候冰纸模型，并使用它来研究41 ka振荡的不同情况，并使用模型结果将代理记录重新分析以目的为目的，以确定是否存在41 ka振荡强迫米兰科维奇，或者是内部（自我维持的）振荡，仅受米兰科维奇强迫影响（相位锁定）。 研究人员还将调查南极冰盖对上新世和早期更新世晚期全球冰量变化的可能贡献。该项目涉及高度跨学科的研究，并招募了古气候，大气动力学，物理海洋学和气候建模领域追求自然气候变化中的基本询问线。 该项目将支持研究生和博士后学者在学科边界以及挪威的同事之间合作，从而促进了美国和挪威研究社区之间的科学合作。