Mid-Pleistocene paleoceanography during a low-eccentricity climate cycle

低偏心率气候周期期间更新世中期的古海洋学

• 批准号: RGPIN-2022-05456
• 负责人: Head, Martin
• 金额: $ 2.66万
• 依托单位: Brock University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=751144
• 关键词: Mid; Pleistocene; paleoceanography; during; low

Our climate has always been paced by complex but mathematically determinable changes in Earth's orbit around the Sun. These changes explain a geological record of glacial-interglacial oscillations during the past 2.7 million years, each representing a slightly different orbital configuration. The oscillations are labelled marine isotope stages: 28 are recognized in the past 1 million years. Marine Isotope Stage (MIS) 19, occurring 770,000 years ago, is significant for two reasons. Firstly, the orbital configuration of its warmest interval was almost identical to that of today's interglacial -- both feature low eccentricity orbits. The study of MIS 19 therefore provides a baseline to understand how humans have affected our modern climate and to predict its natural duration. Secondly, the most significant reversal of Earth's magnetic field in the past 2.6 million years occurred within MIS 19. This reversal is the primary guide to the Early-Middle Pleistocene boundary, and both the reversal and the climatic signals associated with MIS 19 allow precise global recognition of this boundary. Five sites have been selected to elucidate MIS 19, two in Japan, and one in the northern North Atlantic, eastern North Atlantic, and Italy. Each site is highly time-resolved and contains numerous paleoclimatic signals. Moreover, the Japanese site is the global reference section for the Early-Middle Pleistocene boundary and the Italian site is potentially its auxiliary stratotype. However, none of the proposed sections has been studied for dinoflagellate cysts even though this largely planktonic microfossil group is used commonly for quantitative paleoenvironmental reconstructions across a wide range of past oceanographic conditions. MIS 19 has a distinctive global climate signature beginning with an interruption of deglaciation, an early rise to full interglacial conditions, the inception of glaciation, and finally three or four warm and cold oscillations marked by rapid shifts in the climate state. Subtle oscillations during full interglacial conditions were driven by low-latitude orbital harmonics. Glacial inception represents a threshold crossed as global ice volume increased, and the subsequent high-amplitude oscillations reflect disruptions to the Atlantic meridional overturning circulation by meltwater at high latitudes, thereby activating the thermal bipolar seesaw. The coherence of signals between Pacific and Atlantic-Mediterranean sites suggests the influence of the Intertropical Convergence Zone, perhaps amplified regionally by low-latitude monsoon dynamics. A refined understanding of MIS 19 and the mechanisms then operating, facilitated by the application of dinoflagellate cysts as a powerful climate proxy, will help assess generally which features of the climate system are sensitive to low-eccentricity orbital configurations. This research will also sharpen MIS 19 as an instrument for locating the Early-Middle Pleistocene boundary globally.

我们的气候一直以复杂但数学上可确定的地球轨道围绕太阳的变化为节奏。这些变化解释了在过去的270万年中冰川间 - 冰川振荡的地质记录，每种都​​代表略有不同的轨道构型。振荡被标记为海洋同位素阶段：在过去的100万年中，有28个被认可。 770，000年前发生的海洋同位素阶段（MIS）19很重要，原因有两个。首先，其最温暖间隔的轨道构型几乎与当今的冰川间相同 - 两者都具有低偏心轨道。因此，对MIS 19的研究提供了一个基线，以了解人类如何影响我们的现代气候并预测其自然持续时间。其次，在过去的260万年中，地球磁场上最重要的逆转发生在MIS 19中。这种逆转是早期中世纪早期更新世边界的主要指南，并且与MIS 19相关的逆转和气候信号都可以精确地识别该边界。已经选择了五个地点来阐明MIS 19，两个在日本，一个在北大西洋北部，北大西洋和意大利的北部。每个站点都有很高的时间分辨，并包含许多古气候信号。此外，日本站点是早期更新世边界的全球参考部分，意大利地点可能是其辅助层。然而，尽管这种大部分浮游生物的微化石组通常用于在过去的一系列海洋学条件上，但尚未研究所提出的部分用于鞭毛藻囊肿。 MIS 19具有独特的全球气候签名，从中断脱落，早期到完全冰间条件，冰川的诞生以及最终以气候状态快速变化为标志的三，四个温暖和冷振荡开始。在完整的冰间条件下，微妙的振荡是由低纬度轨道谐波驱动的。冰川的成立代表了随着整体冰的增加而越过的阈值，随后的高振幅振荡反映了融合在高纬度处的大西洋子午线倒流循环的破坏，从而激活了热双极透镜。太平洋和大西洋 - 中间地点之间信号的一致性表明，受热带收敛带的影响，也许是通过低纬度季风动力学在区域扩增的。对MIS 19的精致理解以及当时的机制，通过将鞭毛藻囊肿应用为强大的气候代理来促进，将有助于评估气候系统的哪些特征对低年度轨道轨道构型敏感。这项研究还将使MIS 19作为一个在全球范围内定位早期更新世边界的工具。