P2C2: Insolation Control on Ice Sheet Mass Balance in the 41-Kyr World: A Test of Multiple Hypotheses

为研究上新世晚期和更新世早期41,000年冰川循环的物理机制提供了资金。这项研究的前提是，就现有的气候理论而言，这一时期的冰期旋回是一个谜。标准Milankovitch模式的实际应用预测，北半球冰量在倾角（41,000年）和岁差（21,000年）周期中应与北半球夏季日照（即6月65°N）呈线性和相干性变化。然而，这些数据表明，岁差频率仅在一小部分晚上新世冰体积记录中几乎无法识别。同样，大多数用于研究上新世晚期和更新世早期气候历史的计算机模型也在模拟的冰体积中预测了一个强烈的岁差信号。研究者提出问题；“数值气候模型是否遗漏了一些气候或冰盖物理的基本要素？”还是我们对冰量代理的假设有缺陷？具体来说，研究人员将评估墨西哥湾密西西比河流域融水流出的信号，以测试两种相互竞争的假设，以解释41,000年米兰科维奇循环世界的难题。第一个假设是Huybers的综合日照假设，该假设预测劳伦泰德冰盖南缘消融/融水事件的时间应该以倾角来定。另一个是Raymo的反相位进动冰假说，该假说预测Laurentide消融/融水事件应该强烈地以进动为节奏。更广泛的影响包括强大的教育指导部分和同样强大的智力部分，这可能有助于在了解冰盖和海平面动态方面取得变革性进展。

Funding is provided to investigate physical mechanisms responsible for the 41,000 year glacial cycles of the Late Pliocene and Early Pleistocene. The premise of the research is that the glacial cycles of this time are an enigma with respect to existing theories of climate. The de facto application of the standard Milankovitch model predicts that Northern Hemisphere (NH) ice volume should vary linearly and coherently with NH summer insolation (i.e., June 65°N) at the obliquity (41,000 year) and precession (21,000 year) cycles. Yet, the data indicates that the precession frequency is only barely discernable in a small section of Late Pliocene ice volume records. Similarly, most computer models that have been used to study the climate history of the Late Pliocene and Early Pleistocene interval also predict a strong precession signal in the modeled ice volume. The researcher poses the questions; "Are numerical climate models missing some fundamental piece of climate or ice sheet physics? Or is it our assumptions about ice volume proxies that are flawed?"Specifically, the researcher will evaluate the signal of meltwater outflow from the Mississippi Drainage Basin in the Gulf of Mexico to test two competing hypotheses to explain the conundrum of the 41,000 year Milankovitch cycle world. The first hypothesis is the integrated insolation hypothesis of Huybers that predicts the timing of ablation/meltwater events on the southern margin of the Laurentide ice sheet should be paced by obliquity. The other is the anti-phase precession ice hypothesis of Raymo which predicts that Laurentide ablation/meltwater events should be paced strongly by precession. The broader impacts involve a strong educational mentoring portion and an equally strong intellectual portion that may help lead to transformative advances in understanding ice sheet and sea level dynamics.