Ring Index: A new strategy to evaluate the integrity of TEX<sub>86</sub> paleothermometry

Zhang, Yige; Pagani, Mark; Wang, Zhengrong

doi:10.1002/2015pa002848

Cited by 139 publications

(186 citation statements)

References 71 publications

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“…Regression analysis between TEX 86 and RI on the remaining 103 SPM data points showed that by sequentially removing nine outliers, defined as the RI values that exceed the 95% prediction band, RI and TEX 86 become highly correlated when fitted with a quadratic regression (Figure a). The quadratic regression between RI and TEX 86 in surface water is clearly different from the one relating sedimentary RI and TEX 86 in the global data set (Figure a) [ Zhang et al ., ], although both are similar in shape. This implies that the thermal response of isoGDGTs in surface water archaea is likely quantitatively different from global sedimentary isoGDGTs.…”

Section: Discussionmentioning

confidence: 99%

Seasonal distribution of archaeal lipids in surface water and its constraint on their sources and the TEX₈₆ temperature proxy in sediments of the South China Sea

et al. 2017

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The applicability of the temperature proxy based on a tetraether index of 86 carbon atoms (TEX86) from isoprenoidal glycerol dialkyl glycerol tetraethers (isoGDGTs) has increasingly been examined in the South China Sea (SCS). Views on the proxy differ on whether it is biased to a particular season or to depth in this sea. Here we studied isoGDGTs in a large number of suspended particulate matters (SPM) in surface water during summer and winter as well as several surface sediments of the northern SCS. The integration of these novel data with already published data demonstrated that isoGDGTs were similar in distribution between surface water SPM and shallow shelf sediments. They can be characterized by low ratio (<4) of [GDGT‐2]/[GDGT‐3] and low‐percentage abundance (<4%) of the crenarchaeol regioisomer; however, those in deep basin sediments showed higher values for both parameters, suggesting a substantial contribution of “deep‐water” Thaumarchaeota. The relationship between TEX86 in SPM and in situ measured sea surface temperature differed from a global calibration and showed distinct trends between summer and winter, reflecting archaeal seasonality in surface waters. By assuming the TEX86 temperature signal in shallow sediments as the weighted mean of summer and winter signals, we revealed spatial changes in the relative contribution of summer and winter archaeal isoGDGTs to sediments, with a likely higher winter contribution further offshore. This occurrence may complicate the interpretation of the shallow sedimentary TEX86 record, and further investigation is required to fully understand seasonal archaeal lipid production and sedimentation.

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Section: Discussionmentioning

confidence: 99%

Seasonal distribution of archaeal lipids in surface water and its constraint on their sources and the TEX₈₆ temperature proxy in sediments of the South China Sea

et al. 2017

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“…As an alternative to the relatively poor preservation of the foraminifera and issues with the calibration of organic-based proxies (1,5,17), this study exploits the coccoliths as a source of paleoclimatic information. Coccolithophores, single-celled phytoplankton algae, are a key component of the carbon cycle and the ocean biological pump, and their calcite biominerals, the coccoliths, are a major component of pelagic sediments.…”

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confidence: 99%

“…So far, only a handful of sites serve as a reference for climate history at low latitudes during the Eocene and the Eocene−Oligocene Transition (EOT): the nearshore Tanzania in the Indian Ocean [Tanzania Drilling Project (TDP)] (1,2) and open ocean sites in the equatorial Atlantic [Ocean Drilling Program sites ODP 925 and 929] (3)(4)(5). These records exhibit rather conflicting proxy data for the TDP and overall long-term cooling for the Atlantic sites 925 and 929.…”

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confidence: 99%

Equatorial heat accumulation as a long-term trigger of permanent Antarctic ice sheets during the Cenozoic

Tremblin

Hermoso

Minoletti

2016

Proc. Natl. Acad. Sci. U.S.A.

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Growth of the first permanent Antarctic ice sheets at the Eocene−Oligocene Transition (EOT), ∼33.7 million years ago, indicates a major climate shift within long-term Cenozoic cooling. The driving mechanisms that set the stage for this glaciation event are not well constrained, however, owing to large uncertainties in temperature reconstructions during the Eocene, especially at lower latitudes. To address this deficiency, we used recent developments in coccolith biogeochemistry to reconstruct equatorial Atlantic sea surface temperature (SST) and atmospheric pCO 2 values from pelagic sequences preceding and spanning the EOT. We found significantly more variability in equatorial SSTs than previously reported, with pronounced cooling from the Early to Middle Eocene and subsequent warming during the Late Eocene. Thus, we show that the Antarctic glaciation at the Eocene−Oligocene boundary was preceded by a period of heat accumulation in the low latitudes, likely focused in a progressively contracting South Atlantic gyre, which contributed to cooling high-latitude austral regions. This prominent redistribution of heat corresponds to the emplacement of a strong meridional temperature gradient that typifies icehouse climate conditions. Our equatorial coccolith-derived geochemical record thus highlights an important period of global climatic and oceanic upheaval, which began 4 million years before the EOT and, superimposed on a longterm pCO 2 decline, drove the Earth system toward a glacial tipping point in the Cenozoic. . These records exhibit rather conflicting proxy data for the TDP and overall long-term cooling for the Atlantic sites 925 and 929. There is, however, no clear and significant cooling trend from the Early to Middle Eocene that indicates the termination of the Early Eocene Climatic Optimum (Fig. 1A). Furthermore, recent quality-checked SSTs for ODP 925 and 929 sites using the Ring Index indicate relatively similar temperatures between the Late Eocene and the Early Oligocene (5). In contrast, high-latitude sites are consistent in demonstrating appreciable cooling of austral subpolar regions during much of the Eocene (3,4,(6)(7)(8). This apparent lack of substantial temperature change in the intertropical belt during the Eocene and across the EOT remains an enigmatic feature that complicates our understanding of the interplay between seawater temperatures at a global scale, pCO 2 , and changes in global ocean circulations in the context of new Southern Ocean gateways (9-14). The paucity of low-latitude data, especially in the Pacific Ocean, prevents the reconstruction of the latitudinal temperature gradient, much needed for the successful modeling of processes that drove the greenhouse to icehouse transition (10, 15, 16).As an alternative to the relatively poor preservation of the foraminifera and issues with the calibration of organic-based proxies (1, 5, 17), this study exploits the coccoliths as a source of paleoclimatic information. Coccolithophores, single-celled phytoplankton algae, are a key componen...

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“…No samples had GDGT-2/crenarchaeol ratios > 0.4, indicating no GDGT input from methanotrophs (Weijers et al, 2011). As a final 285 exercise, the Ring Index (|ΔRI|) has been calculated for our dataset to identify all other non-temperature related influences on TEX 86 (Zhang et al, 2016). Using |ΔRI|>0.6 as a cutoff, two more samples were discarded.…”

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confidence: 99%

“…We have applied this index on samples analyzed by UHPLC/MS to see if TEX 86 values are reliable despite high BIT index values. In addition, we calculated the Methane Index (MI) (Zhang et al, 2011), GDGT-0/crenarchaeol (Blaga et al, 2009;Sinninghe Damste et al, 2009), GDGT-2/crenarchaeol ratios (Weijers et al, 2011), and Ring Index (Zhang et al, 2016) to check for input of methanogenic or methanotrophic 205 archaea, or any other non-temperature related biases to TEX 86 .…”

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confidence: 99%

Oligocene TEX<sub>86</sub>-derived seawater temperatures from offshore Wilkes Land (East Antarctica)

Hartman

Sangiorgi

Salabarnada

et al. 2017

Preprint

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Abstract. Today, the temperature of the surface waters near the Antarctic coast is a determining factor in the formation of Antarctic Bottom Water (AABW) through sea-ice production, sea-ice extent, and the extent of the ice shelf. O variability is due to large glacial-interglacial bottom-water temperature shifts, the Oligocene Antarctic ice volume was less sensitive to climate change than previously assumed. 45Clim. Past Discuss., https://doi

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Ring Index: A new strategy to evaluate the integrity of TEX₈₆ paleothermometry

Cited by 139 publications

References 71 publications

Seasonal distribution of archaeal lipids in surface water and its constraint on their sources and the TEX₈₆ temperature proxy in sediments of the South China Sea

Seasonal distribution of archaeal lipids in surface water and its constraint on their sources and the TEX₈₆ temperature proxy in sediments of the South China Sea

Equatorial heat accumulation as a long-term trigger of permanent Antarctic ice sheets during the Cenozoic

Oligocene TEX<sub>86</sub>-derived seawater temperatures from offshore Wilkes Land (East Antarctica)

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Ring Index: A new strategy to evaluate the integrity of TEX86 paleothermometry

Cited by 139 publications

References 71 publications

Seasonal distribution of archaeal lipids in surface water and its constraint on their sources and the TEX86 temperature proxy in sediments of the South China Sea

Seasonal distribution of archaeal lipids in surface water and its constraint on their sources and the TEX86 temperature proxy in sediments of the South China Sea

Equatorial heat accumulation as a long-term trigger of permanent Antarctic ice sheets during the Cenozoic

Oligocene TEX&lt;sub&gt;86&lt;/sub&gt;-derived seawater temperatures from offshore Wilkes Land (East Antarctica)

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Ring Index: A new strategy to evaluate the integrity of TEX₈₆ paleothermometry

Seasonal distribution of archaeal lipids in surface water and its constraint on their sources and the TEX₈₆ temperature proxy in sediments of the South China Sea

Seasonal distribution of archaeal lipids in surface water and its constraint on their sources and the TEX₈₆ temperature proxy in sediments of the South China Sea

Oligocene TEX<sub>86</sub>-derived seawater temperatures from offshore Wilkes Land (East Antarctica)