Revised fractional abundances and warm-season temperatures substantially improve brGDGT calibrations in lake sediments

Raberg, Jonathan H.; Harning, David J.; Crump, Sarah E.; Wet, G. de; Blumm, Aria; Kopf, Sebastian; Geirsdóttir, Áslaug; Miller, Gifford H.; Sepúlveda, Julio

doi:10.5194/bg-2021-16

Cited by 7 publications

(20 citation statements)

References 34 publications

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“…S2). Like other Arctic lake sediment records (Zhao et al, 2021;Thomas et al, 2018;Raberg et al, 2021;Peterse et al, 2014) hexamethyl brGDGTs (IIIa, IIIb, IIIc) dominate the brGDGT assemblages (46%), followed by pentamethyl brGDGTs (IIa, IIb, IIc, 30%), then tetramethyl brGDGTs (Ia, Ib, Ic, 23%) (Fig. S2).…”

Section: Gdgtssupporting

confidence: 71%

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

Lindberg

Daniels

Castañeda

et al. 2021

Preprint

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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.

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Section: Gdgtssupporting

confidence: 71%

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

Lindberg

Daniels

Castañeda

et al. 2021

Preprint

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“…A possible explanation for the success of the MAF temperature index is that the activity of brGDGTproducing microbes may be heavily depressed under lake ice and/or in frozen soils (Pearson et al, 2011;Shanahan et al, 2013;Peterse et al, 2014;Cao et al, 2020). However, studies employing sub-seasonal sampling of sediment traps and suspended particulate matter in two mid-latitude lakes have shown that brGDGTs are produced within the water column throughout the year, despite the presence of ice cover (Woltering et al, 2012;Loomis et al, 2014b).…”

Section: Warm-season Temperatures Outperform Matmentioning

confidence: 99%

“…There is increasing evidence that oxygen availability strongly affects lacustrine brGDGT distributions (Colcord et al, 2017;Weber et al, 2018;van Bree et al, 2020;Yao et al, 2020). We therefore tested for calibrations within our dataset with mean and minimum dissolved oxygen concentration (DOmean and DOmin).…”

Section: Dissolved Oxygen and Lake Geometry Calibrationsmentioning

confidence: 99%

“…Tierney et al, 2010;Loomis et al, 2012). However, it was recognized early on that brGDGTderived temperatures in cold regions may more accurately reflect warm-season temperatures (Pearson et al, 2011;Sun et al, 2011), an hypothesis that was strongly supported in high-latitude lake sediments (Shanahan et al, 2013;Peterse et al, 2014;Foster et al, 2016). Since the methodological advances that allowed for the separation of 5-and 6-methyl isomers (De Jonge et al, 2014a) and the development of new calibrations, both modern (Hanna et al, 2016;Dang et al, 2018;Cao et al, 2020) and paleo (Super et al, 2018;Thomas et al, 2018;Crump et al, 2019;Harning et al, 2020) studies have continued to support a warm-season bias.…”

Section: Introductionmentioning

confidence: 99%

“…However, numerous other variables including conductivity (Tierney et al, 2010;Shanahan et al, 2013), dissolved oxygen (DO; Colcord et al, 2017;Weber et al, 2018;van Bree et al, 2020;Yao et al, 2020), nutrient availability (Loomis et al, 2014a), and lake mixing regime (Loomis et al, 2014b;van Bree et al, 2020) have been shown to be potentially important controls on brGDGT distributions. Modern calibrations do not currently exist for these environmental variables, largely due to the complexity of the relationships and data limitations.…”

Section: Introductionmentioning

confidence: 99%

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Naeher¹,

Raberg²,

Harning³

et al. 2021

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Distributions of branched glycerol dialkyl glycerol tetraethers (brGDGTs) are frequently employed for reconstructing terrestrial paleotemperatures from lake sediment archives. Although brGDGTs are globally ubiquitous, the microbial producers of these membrane lipids remain unknown, precluding a full understanding of the ways in which environmental parameters control their production and distribution. Here, we advance this understanding in three ways. First, we present 43 new high-latitude lake sites characterized by low mean annual air temperatures (MATs) and high seasonality, filling an important gap in the global dataset. Second, we introduce a new approach for analyzing brGDGT data in which compound fractional abundances (FAs) are calculated within structural groups based on methylation number, methylation position, and cyclization number. Finally, we perform linear and nonlinear regressions of the resulting FAs against a suite of environmental parameters in a compiled global lake sediment dataset (n = 182). We find that our approach deconvolves temperature, conductivity, and pH trends in brGDGTs without increasing calibration errors from the standard approach. We also find that it reveals novel patterns in brGDGT distributions and provides a methodology for investigating the biological underpinnings of their structural diversity.Warm-season temperature indices outperformed MAT in our regressions, with Months Above Freezing yielding the highest-performing model (adjusted R 2 = 0.91, RMSE = 1.97°C, n = 182). The natural logarithm of conductivity had the second-strongest relationship to brGDGT distributions (adjusted R 2 = 0.83, RMSE = 0.66, n = 143), notably outperforming pH in our dataset (adjusted R 2 = 0.73, RMSE = 0.57, n = 154) and providing a potential new proxy for paleohydrology applications. We recommend these calibrations for use in lake sediments globally, including at high latitudes, and detail the advantages and disadvantages of each.

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A brGDGT‐Based Reconstruction of Terrestrial Temperature From the Maritime Continent Spanning the Last Glacial Maximum

Parish

Bijaksana

et al. 2023

Paleoceanog and Paleoclimatol

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The tropics exert enormous influence on global climate. Despite the importance of tropical regions, the terrestrial temperature history in the Indo‐Pacific Warm Pool (IPWP) region during the last deglaciation is poorly constrained. Although numerous sea surface temperature (SST) reconstructions provide estimates of SST warming from the Last Glacial Maximum to the Holocene, the timing of the onset of deglacial warming varies between records and inhibits determining the forcings driving deglacial warming in the IPWP. We present a 60,000‐year long temperature reconstruction based on branched glycerol dialkyl glycerol tetraethers (brGDGTs) in a sediment core from Lake Towuti, located in Sulawesi, Indonesia. BrGDGTs are bacterial membrane‐spanning lipids that, globally, become more methylated with decreasing temperature and more cyclized with decreasing pH. Although changes in temperature are the dominant control on brGDGTs in regional and global calibrations, we find that the cyclization of the brGDGTs is a major mode of variation at Lake Towuti that records important changes in the lacustrine biogeochemical environment. We separate the influence of lake chemistry changes from temperature changes on the brGDGT records, and develop a temperature record spanning the last 60,000 years. The timing of the deglacial warming in our record occurs after the onset of the deglacial increase in CO2 concentrations, which suggests rising greenhouse gas concentrations and the associated radiative forcing may have forced deglacial warming in the IPWP. Peaks in temperature around 55 and 34 ka indicate that Northern Hemisphere summer insolation may also influence land surface temperature in the IPWP region.

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Revised fractional abundances and warm-season temperatures substantially improve brGDGT calibrations in lake sediments

Cited by 7 publications

References 34 publications

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

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

Comment on bg-2021-16

A brGDGT‐Based Reconstruction of Terrestrial Temperature From the Maritime Continent Spanning the Last Glacial Maximum

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