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

为调查造成上新世晚期和更新世早期41000年冰川周期的物理机制提供了资金。这项研究的前提是，与现有的气候理论相比，这一时期的冰川周期是一个谜。标准Milankovitch模式的实际应用预测，在倾角(41,000年)和进动(21,000年)周期内，北半球(NH)的冰量应该与NH夏季太阳辐射(即，6月65°N)线性且一致地变化。然而，数据表明，在晚上新世冰量记录的一小部分中，进动频率几乎看不出来。同样，大多数用于研究晚上新世和早更新世气候历史的计算机模型也预测了模型冰量中的强烈进动信号。研究人员提出了这样的问题：“数值气候模型是否遗漏了一些基本的气候或冰盖物理信息？或者是我们对冰量指标的假设存在缺陷？”具体地说，研究人员将评估来自墨西哥湾密西西比流域的融水外流信号，以检验两个相互竞争的假设，以解释41000年的米兰科维奇循环世界的谜题。第一个假说是Huybers的综合日照假说，该假说预测了Laurentide冰盖南缘的消融/融水事件的时间应以倾角为步调。另一种是Raymo的反位相进动冰假说，该假说认为Laurentide烧蚀/融水事件应该受到进动的强烈控制。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，这可能有助于在理解冰盖和海平面动态方面取得变革性的进展。

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.