Maastrichtian-Rupelian paleoclimates in the southwest Pacific realm – a critical evaluation of biomarker paleothermometry and dinoflagellate cyst paleoecology at Ocean Drilling Program Site 1172

Abstract. Sea surface temperature (SST) reconstructions based on isoprenoid glycerol dialkyl glycerol tetraether (isoGDGT) distributions from the Eocene southwest (sw) Pacific Ocean are unequivocally warmer than can be reconciled with state-of-the-art fully coupled climate models. However, the SST signal preserved in sedimentary archives can be affected by contributions of additional isoGDGT sources. Methods now exist to identify and possibly correct for overprinting effects on the isoGDGT distribution in marine sediments. We here use the current proxy insights to assess the reliability of the isoGDGT-based SST signal in 69 newly analysed and 242 re-analysed sediments ODP Site 1172 (East Tasman Plateau, Australia) following state-of-the-art chromatographic techniques, in context of paleo-environmental and paleoclimatologic reconstructions based on dinoflagellate cysts. The resulting ~130 kyr-resolution Maastrichtian-Oligocene TEX86-based SST record confirms previous conclusions of anomalous warmth in the early Eocene sw Pacific and remarkably cool conditions during the mid-Paleocene. Dinocyst diversity and assemblages show a strong response to the local SST evolution, supporting the robustness of the TEX86 record. Soil-derived branched GDGTs stored in the same sediments are used to reconstruct mean annual air temperature (MAAT) of the nearby land using the MBT'5me proxy. MAAT is consistently lower than SST during the early Eocene, independent of the calibration chosen. General trends in SST and MAAT are similar, except for: 1) an enigmatic absence of MAAT rise during the Paleocene-Eocene Thermal Maximum and Middle Eocene Climatic Optimum, and 2) a subdued middle–late Eocene MAAT cooling relative to SST. Both dinocysts and GDGT signals suggest a mid-shelf depositional environment with strong river-runoff during the Paleocene-early Eocene, progressively becoming more marine thereafter. This trend reflects gradual drying and more pronounced wet/dry seasons in the northward drifting Australian hinterland, which may also explain the subdued middle Eocene MAAT cooling relative to that of SST. The overall correlation between dinocyst assemblages, marine biodiversity and SST changes suggests that temperature exerted a strong influence on the surface-water ecosystem, probably in part through sea level changes caused by steric effects. Finally, we find support for a potential temperature control on compositional changes of branched glycerol monoalkyl glycerol tetraethers (brGMGTs) in marine sediments. It is encouraging that a critical evaluation of the GDGT signals confirms the vast majority of the generated data is reliable. However, this also implies the high TEX86-based SSTs for the Eocene sw Pacific, and the systematic offset between absolute TEX86-based SST and MBT'5me-based MAAT estimates remain unexplained.

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Maastrichtian–Rupelian paleoclimates in the southwest Pacific – a critical re-evaluation of biomarker paleothermometry and dinoflagellate cyst paleoecology at Ocean Drilling Program Site 1172

Climate of the Past ◽

10.5194/cp-17-2393-2021 ◽

2021 ◽

Vol 17 (6) ◽

pp. 2393-2425

Author(s):

Peter K. Bijl ◽

Joost Frieling ◽

Margot J. Cramwinckel ◽

Christine Boschman ◽

Appy Sluijs ◽

...

Keyword(s):

Marine Sediments ◽

State Of The Art ◽

Middle Eocene ◽

Potential Temperature ◽

Critical Evaluation ◽

Marine Biodiversity ◽

Early Eocene ◽

Ocean Drilling Program ◽

Ocean Drilling ◽

Sw Pacific

Abstract. Sea surface temperature (SST) reconstructions based on isoprenoid glycerol dialkyl glycerol tetraether (isoGDGT) distributions from the Eocene southwest (SW) Pacific Ocean are unequivocally warmer than can be reconciled with state-of-the-art fully coupled climate models. However, the SST signal preserved in sedimentary archives can be affected by contributions of additional isoGDGT sources. Methods now exist to identify and possibly correct for overprinting effects on the isoGDGT distribution in marine sediments. Here, we use the current proxy insights to (re-)assess the reliability of the isoGDGT-based SST signal in 69 newly analyzed and 242 reanalyzed sediments at Ocean Drilling Program (ODP) Site 1172 (East Tasman Plateau, Australia) following state-of-the-art chromatographic techniques. We compare our results with paleoenvironmental and paleoclimatologic reconstructions based on dinoflagellate cysts. The resulting ∼ 130 kyr resolution Maastrichtian–Oligocene SST record based on the TetraEther indeX of tetraethers with 86 carbon atoms (TEX86) confirms previous conclusions of anomalous warmth in the early Eocene SW Pacific and remarkably cool conditions during the mid-Paleocene. Dinocyst diversity and assemblages show a strong response to the local SST evolution, supporting the robustness of the TEX86 record. Soil-derived branched GDGTs stored in the same sediments are used to reconstruct mean annual air temperature (MAAT) of the nearby land using the Methylation index of Branched Tetraethers with 5-methyl bonds (MBT'5me) proxy. MAAT is consistently lower than SST during the early Eocene, independent of the calibration chosen. General trends in SST and MAAT are similar, except for (1) an enigmatic absence of MAAT rise during the Paleocene–Eocene Thermal Maximum and Middle Eocene Climatic Optimum, and (2) a subdued middle–late Eocene MAAT cooling relative to SST. Both dinocysts and GDGT signals suggest a mid-shelf depositional environment with strong river runoff during the Paleocene–early Eocene progressively becoming more marine thereafter. This trend reflects gradual subsidence and more pronounced wet/dry seasons in the northward-drifting Australian hinterland, which may also explain the subdued middle Eocene MAAT cooling relative to that of SST. The overall correlation between dinocyst assemblages, marine biodiversity and SST changes suggests that temperature exerted a strong influence on the surface-water ecosystem. Finally, we find support for a potential temperature control on compositional changes of branched glycerol monoalkyl glycerol tetraethers (brGMGTs) in marine sediments. It is encouraging that a critical evaluation of the GDGT signals confirms that most of the generated data are reliable. However, this also implies that the high TEX86-based SSTs for the Eocene SW Pacific and the systematic offset between absolute TEX86-based SST and MBT'5me-based MAAT estimates remain without definitive explanation.

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Late Paleocene–early Eocene Arctic Ocean sea surface temperatures: reassessing biomarker paleothermometry at Lomonosov Ridge

Climate of the Past ◽

10.5194/cp-16-2381-2020 ◽

2020 ◽

Vol 16 (6) ◽

pp. 2381-2400 ◽

Cited By ~ 1

Author(s):

Appy Sluijs ◽

Joost Frieling ◽

Gordon N. Inglis ◽

Klaas G. J. Nierop ◽

Francien Peterse ◽

...

Keyword(s):

Climate Models ◽

Sea Surface ◽

Temperature Sensitive ◽

Lomonosov Ridge ◽

Early Eocene ◽

Sea Surface Temperatures ◽

Surface Temperatures ◽

Late Paleocene ◽

Air Temperatures ◽

Thermal Maximum

Abstract. A series of papers published shortly after the Integrated Ocean Drilling Program Arctic Coring Expedition (ACEX, 2004) on Lomonosov Ridge indicated remarkably high early Eocene sea surface temperatures (SSTs; ca. 23 to 27 ∘C) and land air temperatures (ca. 17 to 25 ∘C) based on the distribution of isoprenoid and branched glycerol dialkyl glycerol tetraether (isoGDGT and brGDGT) lipids, respectively. Here, we revisit these results using recent analytical developments – which have led to improved temperature calibrations and the discovery of new temperature-sensitive glycerol monoalkyl glycerol tetraethers (GMGTs) – and currently available proxy constraints. The isoGDGT assemblages support temperature as the dominant variable controlling TEX86 values for most samples. However, contributions of isoGDGTs from land, which we characterize in detail, complicate TEX86 paleothermometry in the late Paleocene and part of the interval between the Paleocene–Eocene Thermal Maximum (PETM; ∼ 56 Ma) and the Eocene Thermal Maximum 2 (ETM2; ∼ 54 Ma). Background early Eocene SSTs generally exceeded 20 ∘C, with peak warmth during the PETM (∼ 26 ∘C) and ETM2 (∼ 27 ∘C). We find abundant branched GMGTs, likely dominantly marine in origin, and their distribution responds to environmental change. Further modern work is required to test to what extent temperature and other environmental factors determine their distribution. Published Arctic vegetation reconstructions indicate coldest-month mean continental air temperatures of 6–13 ∘C, which reinforces the question of whether TEX86-derived SSTs in the Paleogene Arctic are skewed towards the summer season. The exact meaning of TEX86 in the Paleogene Arctic thus remains a fundamental issue, and it is one that limits our assessment of the performance of fully coupled climate models under greenhouse conditions.

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Late Paleocene – early Eocene Arctic Ocean Sea Surface Temperatures; reassessing biomarker paleothermometry at Lomonosov Ridge

10.5194/cp-2020-13 ◽

2020 ◽

Author(s):

Appy Sluijs ◽

Joost Frieling ◽

Gordon N. Inglis ◽

Klaas G. J. Nierop ◽

Francien Peterse ◽

...

Keyword(s):

Arctic Ocean ◽

Climate Models ◽

Sea Surface ◽

The Arctic ◽

Temperature Sensitive ◽

Lomonosov Ridge ◽

Early Eocene ◽

Terrestrial Vegetation ◽

Late Paleocene ◽

Thermal Maximum

Abstract. The Integrated Ocean Drilling Program Arctic Coring Expedition on Lomonosov Ridge, Arctic Ocean (IODP Expedition 302 in 2004) delivered the first Arctic Ocean sea surface temperature (SST) and land air temperature (LAT) records spanning the Paleocene-Eocene Thermal Maximum (PETM; ~56 Ma) to Eocene Thermal Maximum 2 (ETM2; ~54 Ma). The distribution of glycerol dialkyl glycerol tetraether (GDGT) lipids indicated elevated SST (ca. 23 to 27 °C) and LATs (ca. 17 to 25 °C). However, recent analytical developments have led to: (i) improved temperature calibrations and (ii) the discovery of new temperature-sensitive glycerol monoalkyl glycerol tetraethers (GMGTs). Here, we have analyzed GDGT and GMGT distributions in the same sediment samples using new analytical procedures, interpret the results following the currently available proxy constraints and assess the fidelity of new temperature estimates in our study site. The influence of several confounding factors on TEX86 SST estimates, such as variations in export depth and input from exogenous sources, are typically negligible. However, contributions of isoGDGTs from land, which we characterize in detail, complicate TEX86 paleothermometry in the late Paleocene and part of the interval between the PETM and ETM2. The isoGDGT distribution further supports temperature as the likely variable controlling TEX86 values and we conclude that background early Eocene SSTs generally exceeding 20 °C, with peak warmth during the PETM (~26 °C) and ETM2 (~27 °C). We also report high abundances of branched glycerol monoalkyl glycerol tetraethers throughout (branched GMGTs), most likely dominantly marine in origin, and show that their distribution is sensitive to environmental parameters. Further analytical, provenance and environmental work is required to test if and to what extent temperature may be an important factor. Published temperature constraints from branched GDGTs and terrestrial vegetation also support remarkable warmth in the study section and elsewhere in the Arctic basin, with vegetation proxies indicating coldest month mean temperatures of 6–13 °C. If TEX86-derived SSTs truly represent mean annual SSTs, the seasonal range of Arctic SST was in the order of 20 °C, higher than any open marine locality in the modern ocean. If SST estimates are skewed towards the summer season, seasonal ranges were comparable to those simulated in future ice-free Arctic Ocean scenarios. This uncertainty remains a fundamental issue, and one that limits our assessment of the performance of fully-coupled climate models under greenhouse conditions.

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Early to middle Eocene calcareous nannofossils of the SW Pacific: Paleobiogeography and paleoclimate

10.26686/wgtn.17057960.v1 ◽

2021 ◽

Author(s):

◽

Claire Louise Shepherd

Keyword(s):

Temperature Gradient ◽

Middle Eocene ◽

Warm Water ◽

East Australian Current ◽

Early Eocene ◽

Calcareous Nannofossil ◽

Cool Water ◽

Sw Pacific ◽

Geochemical Proxies ◽

Dsdp Site

Earth’s climate underwent a long-term warming trend from the late Paleocene to early Eocene (~58–51 Ma), with global temperature reaching a sustained maximum during the Early Eocene Climatic Optimum (EECO; 53–50 Ma). Geochemical proxies indicate tropical or warm subtropical sea-surface temperature (SST) conditions in middle and high latitudes in the early Eocene, implying a very low latitudinal temperature gradient. This study investigates whether calcareous nannofossil assemblages in the southwest (SW) Pacific provide evidence of these conditions at middle latitudes in the early to middle Eocene, particularly during the EECO. Specifically, this study documents the biogeographic changes of warm- and cold-water nannofossil species along a paleolatitudinal transect through the EECO to track changes in water masses/ocean circulation at that time. Early to middle Eocene calcareous nannofossil assemblages were examined from four sites along a latitudinal transect in the SW Pacific, extending from Lord Howe Rise in the north to Campbell Plateau in the south and spanning a paleolatitude of ~46–54°S. All of the sections studied in this project span nannofossil zones NP10–16 (Martini, 1971). The data indicate up to three regional unconformities through the sections: at mid-Waipara, Deep Sea Drilling Project (DSDP) Site 207 and 277, part or all of Zone NP10 (lower Waipawan) is missing; at Sites 207 and 277 a possible hiatus occurs within NP12 (upper Waipawan–lower Mangaorapan); and at all sites part or all of Zone NP15 (lower Bortonian) is missing. Results of this study indicate that nannofossil assemblages in the SW Pacific are more similar to floras at temperate to polar sites rather than those at tropical/subtropical sites. However, variations in the relative abundance of key species in the SW Pacific are broadly consistent with the trends seen in the geochemical proxy records: an increase in warm-water taxa coincided with the EECO, corroborating geochemical evidence for a temperature maximum in the SW Pacific during this interval. The increase in the abundance and diversity of warm-water taxa and decrease in the abundance of cool-water taxa through the EECO supports previous suggestions that a warm-water mass (northward of the proto-Tasman Front) extended to ~55°S paleolatitude during this interval in response to enhanced poleward heat transport and intensification of the proto-East Australian Current. At the southernmost site, DSDP Site 277, a relatively short-lived influx of warm-water taxa at ~51 Ma suggests that warm waters expanded south at this time. However, greater diversity and abundance of warm-water taxa throughout the EECO at DSDP Site 207, suggests that the proto-East Australian Current exerted greater influence at this latitude for a longer duration than at Site 277. An increase in the abundance of cool-water taxa and decrease in diversity and abundance of warm-water taxa at all sites is recorded following the termination of the EECO. This corresponds with the contraction of the proto-Tasman Front due to weakened proto-East Australian Current flow and associated amplification of the proto-Ross Gyre. Previous estimates of SSTs from geochemical proxies in the SW Pacific during the EECO indicate that there was virtually no latitudinal temperature gradient and temperatures were tropical to subtropical (>20°C). However, nannofossil data from this study indicate warm temperate conditions (~15–20°C) during the EECO, suggesting that a reduced latitudinal gradient was maintained through this interval, which is in agreement with climate models.

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Resilience of SW Pacific marine plankton to Cenozoic global warming events

10.5194/egusphere-egu21-1004 ◽

2021 ◽

Author(s):

Chris Hollis ◽

Giuseppe Cortese ◽

Martin Crundwell ◽

Claire Shepherd ◽

Erica Crouch ◽

...

Keyword(s):

Global Warming ◽

Environmental Changes ◽

Middle Eocene ◽

Marine Plankton ◽

Last Interglacial ◽

Deep Sea Sediment ◽

Sw Pacific ◽

Thermal Maximum ◽

Future Global Warming ◽

Plankton Communities

Ceonozoic deep-sea sediment archives from the southwest Pacific have been used to reconstruct regional climatic and environmental changes associated with global warming events from the earliest Eocene to the Last Interglacial. Less attention has been given to the biotic significance of associated changes in microfossil assemblages. Here we report what is currently known of the effects that global warming events have had on regional plankton communities, specifically foraminifera, calcareous nannoplankton, radiolarians and dinoflagellates. We focus on a succession of events representative of different magnitudes of global warming, including the Paleocene-Eocene thermal maximum, early and middle Eocene climatic optima, middle Miocene climatic optimum, mid-Pliocene warm period, and the Last Interglacial. From this study, we hope to establish ways in which the fossil record can be applied to assess the resilience of modern marine plankton communities to current and future global warming.

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Early to middle Eocene calcareous nannofossils of the SW Pacific: Paleobiogeography and paleoclimate

10.26686/wgtn.17057960 ◽

2021 ◽

Author(s):

◽

Claire Louise Shepherd

Keyword(s):

Temperature Gradient ◽

Middle Eocene ◽

Warm Water ◽

East Australian Current ◽

Early Eocene ◽

Calcareous Nannofossil ◽

Cool Water ◽

Sw Pacific ◽

Geochemical Proxies ◽

Dsdp Site

Earth’s climate underwent a long-term warming trend from the late Paleocene to early Eocene (~58–51 Ma), with global temperature reaching a sustained maximum during the Early Eocene Climatic Optimum (EECO; 53–50 Ma). Geochemical proxies indicate tropical or warm subtropical sea-surface temperature (SST) conditions in middle and high latitudes in the early Eocene, implying a very low latitudinal temperature gradient. This study investigates whether calcareous nannofossil assemblages in the southwest (SW) Pacific provide evidence of these conditions at middle latitudes in the early to middle Eocene, particularly during the EECO. Specifically, this study documents the biogeographic changes of warm- and cold-water nannofossil species along a paleolatitudinal transect through the EECO to track changes in water masses/ocean circulation at that time. Early to middle Eocene calcareous nannofossil assemblages were examined from four sites along a latitudinal transect in the SW Pacific, extending from Lord Howe Rise in the north to Campbell Plateau in the south and spanning a paleolatitude of ~46–54°S. All of the sections studied in this project span nannofossil zones NP10–16 (Martini, 1971). The data indicate up to three regional unconformities through the sections: at mid-Waipara, Deep Sea Drilling Project (DSDP) Site 207 and 277, part or all of Zone NP10 (lower Waipawan) is missing; at Sites 207 and 277 a possible hiatus occurs within NP12 (upper Waipawan–lower Mangaorapan); and at all sites part or all of Zone NP15 (lower Bortonian) is missing. Results of this study indicate that nannofossil assemblages in the SW Pacific are more similar to floras at temperate to polar sites rather than those at tropical/subtropical sites. However, variations in the relative abundance of key species in the SW Pacific are broadly consistent with the trends seen in the geochemical proxy records: an increase in warm-water taxa coincided with the EECO, corroborating geochemical evidence for a temperature maximum in the SW Pacific during this interval. The increase in the abundance and diversity of warm-water taxa and decrease in the abundance of cool-water taxa through the EECO supports previous suggestions that a warm-water mass (northward of the proto-Tasman Front) extended to ~55°S paleolatitude during this interval in response to enhanced poleward heat transport and intensification of the proto-East Australian Current. At the southernmost site, DSDP Site 277, a relatively short-lived influx of warm-water taxa at ~51 Ma suggests that warm waters expanded south at this time. However, greater diversity and abundance of warm-water taxa throughout the EECO at DSDP Site 207, suggests that the proto-East Australian Current exerted greater influence at this latitude for a longer duration than at Site 277. An increase in the abundance of cool-water taxa and decrease in diversity and abundance of warm-water taxa at all sites is recorded following the termination of the EECO. This corresponds with the contraction of the proto-Tasman Front due to weakened proto-East Australian Current flow and associated amplification of the proto-Ross Gyre. Previous estimates of SSTs from geochemical proxies in the SW Pacific during the EECO indicate that there was virtually no latitudinal temperature gradient and temperatures were tropical to subtropical (>20°C). However, nannofossil data from this study indicate warm temperate conditions (~15–20°C) during the EECO, suggesting that a reduced latitudinal gradient was maintained through this interval, which is in agreement with climate models.

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Critical Evaluation of the State of the Art in Surgery for Parkinson Disease: Should We Use the Same Criteria as for Drug Trials?

Archives of Neurology ◽

10.1001/archneur.58.2.315 ◽

2001 ◽

Vol 58 (2) ◽

pp. 315-316

Author(s):

M. I. Hariz

Keyword(s):

Parkinson Disease ◽

State Of The Art ◽

Critical Evaluation ◽

The State ◽

Drug Trials

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Smartphone-Based Indoor Visual Navigation with Leader-Follower Mode

ACM Transactions on Sensor Networks ◽

10.1145/3448417 ◽

2021 ◽

Vol 17 (2) ◽

pp. 1-22

Author(s):

Jingao Xu ◽

Erqun Dong ◽

Qiang Ma ◽

Chenshu Wu ◽

Zheng Yang

Keyword(s):

Real Time ◽

Environmental Changes ◽

State Of The Art ◽

Visual Navigation ◽

Indoor Navigation ◽

Location Services ◽

Localization And Mapping ◽

Leaders And Followers ◽

Indoor Navigation System ◽

Free Pair

Existing indoor navigation solutions usually require pre-deployed comprehensive location services with precise indoor maps and, more importantly, all rely on dedicatedly installed or existing infrastructure. In this article, we present Pair-Navi, an infrastructure-free indoor navigation system that circumvents all these requirements by reusing a previous traveler’s (i.e., leader) trace experience to navigate future users (i.e., followers) in a Peer-to-Peer mode. Our system leverages the advances of visual simultaneous localization and mapping ( SLAM ) on commercial smartphones. Visual SLAM systems, however, are vulnerable to environmental dynamics in the precision and robustness and involve intensive computation that prohibits real-time applications. To combat environmental changes, we propose to cull non-rigid contexts and keep only the static and rigid contents in use. To enable real-time navigation on mobiles, we decouple and reorganize the highly coupled SLAM modules for leaders and followers. We implement Pair-Navi on commodity smartphones and validate its performance in three diverse buildings and two standard datasets (TUM and KITTI). Our results show that Pair-Navi achieves an immediate navigation success rate of 98.6%, which maintains as 83.4% even after 2 weeks since the leaders’ traces were collected, outperforming the state-of-the-art solutions by >50%. Being truly infrastructure-free, Pair-Navi sheds lights on practical indoor navigations for mobile users.

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