Biomarker Proxy Records of Arctic Climate Change During the Mid-Pleistocene Transition from Lake El’gygytgyn (Far East Russia)

Abstract

Abstract. The Mid-Pleistocene Transition (MPT) is a widely recognized global climate shift occurring between approximately 1,250 to 700 ka. At this time, Earth's climate underwent a major transition from dominant 40 kyr glacial-interglacial cycles to quasi-100 kyr cycles. The cause of the MPT remains a puzzling aspect of Pleistocene climate. Presently, there are few, if any, continuous MPT records from the Arctic yet understanding the role and response of the high latitudes to the MPT is required to better evaluate the causes of this climatic shift. Here, we present new continental biomarker records of temperature and vegetation spanning 1,142 to 752 ka from Lake El'gygytgyn (Far East Russia). We reconstruct warm-season temperature variations across the MPT based on branched glycerol dialkyl glycerol tetraethers (brGDGTs) using the MBTʹ5ME proxy. The new Arctic temperature record does not display an overall cooling trend during the MPT but does exhibit strong glacial-interglacial cyclicity. Spectral analysis demonstrates persistent obliquity and precession pacing over the study interval and reveals substantial sub-orbital temperature variations at ~900 kyr during the first “skipped” interglacial. Interestingly, Marine Isotope Stage (MIS) 31, which is widely recognized as a particularly warm interglacial, does not exhibit exceptional warmth at Lake El'gygytgyn. Instead, we find that MIS 29, 27 and 21 were as warm or warmer than MIS 31. In particular, MIS 21 (~870 to 820 ka) stands out as an especially warm and long interglacial in the continental Arctic while MIS 25 is a notably cold interglacial. Throughout the MPT, Lake El'gygytgyn pollen data exhibits a long-term drying trend, with a shift to an increasingly open landscape noted after around 900 ka (Zhao et al., 2018), which is also reflected in our higher plant leaf wax (n-alkane) distributions. Although the mechanisms driving the MPT remain a matter of debate, our new climate records from the continental Arctic exhibit some similarities to changes noted around the North Pacific region. Overall, the new organic geochemical data from Lake El'gygytgyn contribute to expanding our knowledge of the high-latitude response to the MPT.

Expanded North Pacific Subtropical Gyre and Heterodyne Expression During the Mid‐Pleistocene

“…While changes in linear sedimentation rates between age tie points represent an average rate of deposition that likely fluctuates between glacial and interglacial periods, Hole 1207A exhibits a baseline increase in linear sedimentation rates during and after the MPT (Figure 4). This increased sedimentation rate is consistent with subarctic North Pacific Ocean records indicating an overall increase in eolian dust flux and grain size during and after the MPT due to increasing aridity across Asia and westerly wind strength over the Pacific (e.g., Heslop et al, 2002;Jia et al, 2018;Lindberg et al, 2022;Machalett et al, 2008;Sun & An, 2005;Wang et al, 2016;Yang et al, 2006;Zhao et al, 2018). Similarly, such evidence for strengthening of the North Pacific westerlies has been recently documented at sites just to the north of Hole 1207A (i.e., ODP Sites 885/886) across major episodes of Northern Hemisphere cooling (i.e., iNHG at 2.7 Ma; Abell et al, 2021).…”

“…Changes in the position of the KCE over the last 2 million years has been significantly influenced by orbital forcing mechanisms with discrete intervals spanning MISs 29‐25 and 15, 11‐9, which demonstrate potential sustained warmth and expansion of the North Pacific Subtropical Gyre. Some of these unusual warm and persistent interglacials coincide with documented intervals of exceptional warmth in the Pacific Arctic region (Brigham‐Grette et al., 2013; de Wet et al., 2016; Jaccard et al., 2009; Lindberg et al., 2022; Melles et al., 2012). Notably, these two intervals are identified by higher magnitude of glacial‐interglacial variability in cluster lithologies (higher cluster 2 to cluster 1) and XRF elemental ratios ( ln Zr/Sr and ln Ca/Ti).…”

“…This period of subtropical gyre expansion during MIS 15 and 11‐9 and excess precipitation over parts of the Northeastern Siberia may demonstrate the tight coupling between expansion of the subtropical high and displacement of the low‐pressure system (Aleutian Low) delivering precipitation to the terrestrial biosphere in the high northern latitudes rather than over the Pacific Ocean. We propose that expansion of the subtropical gyre may have contributed to the unusual and enhanced warmth experienced in high‐latitude regions that has been documented for at least MIS 29, 27, 21, 11, and 9 (e.g., De Wet et al., 2016; Lindberg et al., 2022; Melles et al., 2012). Our data further highlights not only the role that the KCE plays in heat transport to the North Pacific (e.g., Nishikawa et al., 2020; Sakamoto et al., 2005; Zhang et al., 2017), but also the role of the subtropical high system in regulating moisture across North High Latitudes in the Pacific sector.…”

“…The reversed‐polarity interval stratigraphically above the Jaramillo contains two more decimeter to meter‐scale beds of the carbonate‐rich cluster 2 lithology and corresponds to MIS 27‐25. Recently, warm‐season temperature variations across the MPT have been reconstructed for the Lake El'gygytgyn record recovered from far east Russia and imply MIS 29, 27, and 21 were possibly warmer than MIS 31 (Lindberg et al., 2022). Thus, the timing of these warmer land‐derived interglacial temperatures in the northern high‐latitudes, coincides stratigraphically with the timing of subtropical gyre expansion as hypothesized from the new Hole 1207A inorganic geochemical record.…”

“…Over the past two million years of Earth's history, the climate system underwent dramatic transitions in both the pacing (during the Mid‐Pleistocene Climate Transition [MPT] 1.25‐0.80 Ma) and amplitude (during the Mid‐Brunhes Event [MBE] at ∼0.43 Ma) variability of glacial to interglacial periods (e.g., Ahn et al., 2017). Additionally, the eastern terrestrial Arctic experienced episodes of extreme warming referred to as super‐interglacials (i.e., Marine Isotope Stages [MIS] 11, 21, 27, 29; Lindberg et al., 2022; Melles et al., 2012). These past periods of transition and warming provide partial analogs to investigate how the KCE may respond to times of climate reorganization and elevated global mean temperatures that are projected for the coming decades (IPCC, 2021).…”