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2021 ◽  
pp. 1-12
Author(s):  
Julie Dabkowski ◽  
Nicole Limondin-Lozouet

Abstract Many recent palaeoclimatic studies have focused on Pleistocene interglacials, especially Marine Isotopic Stages (MIS) 5e and 11, as analogs to our modern interglacial (MIS 1). In continental area, archives allowing comparison between interglacials remain scarce. Calcareous tufa deposits, as they are characteristic of these periods and can provide long, almost continuous, palaeoclimatic records through their isotopic content, appear highly suitable for such investigation. In this paper, δ18O and δ13C values from the three well-dated tufas of Saint-Germain-le-Vasson, Caours, and La Celle are combined to compare temperature and moisture conditions prevailing during MIS 1, 5e, and 11, in the Paris Basin. Both Pleistocene interglacials, and especially their optima, appear stronger than the Holocene: MIS 11 was wetter and warmer than both the Holocene and MIS 5e, which itself experienced wetter conditions than the Holocene. These observations are consistent with palaeontological data from the studied sites, especially malacological assemblages, which record, as at other European tufa sites, a relative depletion of molluscan diversity during the Holocene compared with the Pleistocene (MIS 5 and 11) interglacials.


2021 ◽  
Author(s):  
Trinidad Torres ◽  
José E. Ortiz ◽  
Rosa Mediavilla ◽  
Yolanda Sánchez-Palencia ◽  
Juan Ignacio Santisteban ◽  
...  

AbstractThe coastal zone in which the lagoons of La Mata and Torrevieja (Eastern Spain) developed can be described as a compilation of geo-hazards typical of the Mediterranean realm. This study has focused mainly on those linked to recent tectonics. Extensive use of the amino acid racemization dating method allowed us to establish the evolution of all the geomorphological units differentiated in the area, the most striking manifestation being at the La Mata Lagoon Bar, where MIS 5 deposits settled on MIS 7 sediments along a marked erosive unconformity, thereby attesting coastal uplift between these two stages. In addition, recent uplift processes were reflected on stepped abrasion platforms and, in some cases, enormous boulders were transported over these platforms by extreme surge waves. Furthermore, we obtained feasible evidence that, during the end of MIS 5, an earthquake with an offshore epicenter linked to Torrevieja Fault, Bajo Segura Fault or the set of faults linked to the former, was responsible for tsunami surge deposits represented in accumulations of randomly arranged and well-preserved Glycymeris and Acanthocardia shells. Recent catastrophic effects linked to the earthquakes were also detected. In this regard, comparison of the paleontological and taphonomic analyses allowed us to discern between wave and tsunami surge deposits. Therefore, evidence of these hazards undoubtedly points to important future (and present) erosive and/or catastrophic processes, which are enhanced by the presence of tourist resorts and salt-mining industry. Thus, these sites are also threatened by future increases in sea level in the context of warmer episodes, attested by raised marine fossil deposits. At the north of Cervera Cape, beaches will be eroded, without any possibility of sediment input from the starved Segura River delta. At the south of this cape, waves (and tsunamis) will erode the soft rocks that built up the cliff, creating deep basal notches.


2021 ◽  
Author(s):  
◽  
Bella Jane Duncan

<p>Coccolithophores play a key role in the ocean carbon cycle, regulating the uptake and release of CO2. Satellite observations over the past few decades show ocean change in a warming world is accompanied by changes in the latitudinal distribution of coccolithophore blooms. Despite their importance in the carbon cycle, knowledge of the causes of coccolithophore blooms, and how they may respond to future climate change is limited. In this study evidence from marine sedimentary cores is used to derive longer, more complete records of past coccolithophore productivity, and the factors that potentially caused enhanced coccolithophore productivity in previous interglacials. Carbonate-rich marine cores; subtropical P71 from north of New Zealand (33°51.3‟S, 174°41.6‟E) and subantarctic Ocean Drilling Project (ODP) 1120 from the Campbell Plateau (50°3.803‟S, 173°22.300‟E) show abrupt changes between foraminiferal-rich sediments during glacials to coccolith-rich sediments during interglacials. Both cores encompass the last two complete interglacial cycles, Marine Isotope Stage (MIS) 5 (71-130ka) and MIS 7 (191- 243ka). While MIS 5 has been well-studied in the Southwest Pacific Ocean, research on MIS 7 is limited. From the literature, and data from this study, new insights are presented into the climatic and oceanographic conditions during MIS 7. Sea surface temperatures in the subtropical Tasman Inflow were comparable to present during MIS 7a (191-222ka), but were cooler in MIS 7c (235-243ka), implying a change in flow regime potentially related to the dynamics of the South Pacific Gyre. During MIS 7a and 7c the temperature gradient across the Subtropical Front (STF), which separates subtropical and subantarctic waters, was greater than present on the Chatham Rise, at >2°C per 1° latitude. In the Tasman Sea, the STF moved northwards by ~2° latitude. This thesis employs grain size data and scanning electron microscope images to show that significant coccolithophore blooms occurred during MIS 7a at subtropical core P71, but not during interglacial peak MIS 5e (117-130ka), whilst the reverse is true at subantarctic core ODP 1120. A range of paleo-environmental proxies are used to determine the potential conditions that caused these coccolithophore blooms. This includes mass accumulation rates of CaCO3 and % of <20μm grain size that texturally identifies coccoliths, to determine relative rates of coccolithophore productivity. Oxygen isotopes (δ18O) of multiple planktic and benthic foraminifera provide age models, with the former also helping to identify upper water column stratification. Mg/Ca ratios in planktic foraminifera, Globigerinoides ruber, and Random Forest modelling of planktic foraminifera assemblages have been used to derive paleo-temperature estimates. These methods, coupled with trace element data from G. ruber as a productivity proxy, foraminifera assemblages, data on solar insolation and scanning electron microscope images, collectively determine the oceanic conditions at the time of coccolithophore blooms at each core site. The results suggest that no one factor was responsible for blooming, rather it was the combination, and interactions between different environmental processes, that were important. At P71, key factors for bloom formation in MIS 7a were high insolation, thermal stratification of the uppermost ocean, and well-mixed source waters from the Tasman Inflow. At ODP 1120, blooms in MIS 5e resulted from decreased windiness, warmer sea surface temperatures and reduced oceanic circulation over the Campbell Plateau, resulting in marked thermal stratification. It is likely that coccolithophore blooms further enhanced stratification at each core site, and restricted productivity further down the water column. At P71, modern oceanic trends suggest that conditions that caused blooms during MIS 7a will not be met in the near future, and blooming is unlikely to increase at this core site. At ODP 1120, modern trends are less clear, but future conditions are projected to be comparable to MIS 5e, suggesting that coccolithophore blooming may increase in the future in subantarctic waters.</p>


2021 ◽  
Author(s):  
◽  
Bella Jane Duncan

<p>Coccolithophores play a key role in the ocean carbon cycle, regulating the uptake and release of CO2. Satellite observations over the past few decades show ocean change in a warming world is accompanied by changes in the latitudinal distribution of coccolithophore blooms. Despite their importance in the carbon cycle, knowledge of the causes of coccolithophore blooms, and how they may respond to future climate change is limited. In this study evidence from marine sedimentary cores is used to derive longer, more complete records of past coccolithophore productivity, and the factors that potentially caused enhanced coccolithophore productivity in previous interglacials. Carbonate-rich marine cores; subtropical P71 from north of New Zealand (33°51.3‟S, 174°41.6‟E) and subantarctic Ocean Drilling Project (ODP) 1120 from the Campbell Plateau (50°3.803‟S, 173°22.300‟E) show abrupt changes between foraminiferal-rich sediments during glacials to coccolith-rich sediments during interglacials. Both cores encompass the last two complete interglacial cycles, Marine Isotope Stage (MIS) 5 (71-130ka) and MIS 7 (191- 243ka). While MIS 5 has been well-studied in the Southwest Pacific Ocean, research on MIS 7 is limited. From the literature, and data from this study, new insights are presented into the climatic and oceanographic conditions during MIS 7. Sea surface temperatures in the subtropical Tasman Inflow were comparable to present during MIS 7a (191-222ka), but were cooler in MIS 7c (235-243ka), implying a change in flow regime potentially related to the dynamics of the South Pacific Gyre. During MIS 7a and 7c the temperature gradient across the Subtropical Front (STF), which separates subtropical and subantarctic waters, was greater than present on the Chatham Rise, at >2°C per 1° latitude. In the Tasman Sea, the STF moved northwards by ~2° latitude. This thesis employs grain size data and scanning electron microscope images to show that significant coccolithophore blooms occurred during MIS 7a at subtropical core P71, but not during interglacial peak MIS 5e (117-130ka), whilst the reverse is true at subantarctic core ODP 1120. A range of paleo-environmental proxies are used to determine the potential conditions that caused these coccolithophore blooms. This includes mass accumulation rates of CaCO3 and % of <20μm grain size that texturally identifies coccoliths, to determine relative rates of coccolithophore productivity. Oxygen isotopes (δ18O) of multiple planktic and benthic foraminifera provide age models, with the former also helping to identify upper water column stratification. Mg/Ca ratios in planktic foraminifera, Globigerinoides ruber, and Random Forest modelling of planktic foraminifera assemblages have been used to derive paleo-temperature estimates. These methods, coupled with trace element data from G. ruber as a productivity proxy, foraminifera assemblages, data on solar insolation and scanning electron microscope images, collectively determine the oceanic conditions at the time of coccolithophore blooms at each core site. The results suggest that no one factor was responsible for blooming, rather it was the combination, and interactions between different environmental processes, that were important. At P71, key factors for bloom formation in MIS 7a were high insolation, thermal stratification of the uppermost ocean, and well-mixed source waters from the Tasman Inflow. At ODP 1120, blooms in MIS 5e resulted from decreased windiness, warmer sea surface temperatures and reduced oceanic circulation over the Campbell Plateau, resulting in marked thermal stratification. It is likely that coccolithophore blooms further enhanced stratification at each core site, and restricted productivity further down the water column. At P71, modern oceanic trends suggest that conditions that caused blooms during MIS 7a will not be met in the near future, and blooming is unlikely to increase at this core site. At ODP 1120, modern trends are less clear, but future conditions are projected to be comparable to MIS 5e, suggesting that coccolithophore blooming may increase in the future in subantarctic waters.</p>


2021 ◽  
Vol 17 (5) ◽  
pp. 2273-2289
Author(s):  
Sarah Shackleton ◽  
James A. Menking ◽  
Edward Brook ◽  
Christo Buizert ◽  
Michael N. Dyonisius ◽  
...  

Abstract. Deglaciations are characterized by relatively fast and near-synchronous changes in ice sheet volume, ocean temperature, and atmospheric greenhouse gas concentrations, but glacial inception occurs more gradually. Understanding the evolution of ice sheet, ocean, and atmosphere conditions from interglacial to glacial maximum provides insight into the interplay of these components of the climate system. Using noble gas measurements in ancient ice samples, we reconstruct mean ocean temperature (MOT) from 74 to 59.7 ka, covering the Marine Isotope Stage (MIS) 5a–4 boundary, MIS 4, and part of the MIS 4–3 transition. Comparing this MOT reconstruction to previously published MOT reconstructions from the last and penultimate deglaciation, we find that the majority of the last interglacial–glacial ocean cooling must have occurred within MIS 5. MOT reached equally cold conditions in MIS 4 as in MIS 2 (−2.7 ± 0.3 ∘C relative to the Holocene, −0.1 ± 0.3 ∘C relative to MIS 2). Using a carbon cycle model to quantify the CO2 solubility pump, we show that ocean cooling can explain most of the CO2 drawdown (32 ± 4 of 40 ppm) across MIS 5. Comparing MOT to contemporaneous records of benthic δ18O, we find that ocean cooling can also explain the majority of the δ18O increase across MIS 5 (0.7 ‰ of 1.3 ‰). The timing of ocean warming and cooling in the record and the comparison to coeval Antarctic isotope data suggest an intimate link between ocean heat content, Southern Hemisphere high-latitude climate, and ocean circulation on orbital and millennial timescales.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Carlos Neto de Carvalho ◽  
Zain Belaústegui ◽  
Antonio Toscano ◽  
Fernando Muñiz ◽  
João Belo ◽  
...  

AbstractTracks and trackways of newborns, calves and juveniles attributed to straight-tusked elephants were found in the MIS 5 site (Upper Pleistocene) known as the Matalascañas Trampled Surface (MTS) at Huelva, SW Spain. Evidence of a snapshot of social behaviour, especially parental care, can be determined from the concentration of elephant tracks and trackways, and especially from apparently contemporaneous converging trackways, of small juvenile and larger, presumably young adult female tracks. The size frequency of the tracks enabled us to infer body mass and age distribution of the animals that crossed the MTS. Comparisons of the MTS demographic frequency with the morphology of the fore- and hind limbs of extant and fossil proboscideans shed light into the reproductive ecology of the straight-tusked elephant, Palaeloxodon antiquus. The interdune pond habitat appeared to have been an important water and food resource for matriarchal herds of straight-tusked elephants and likely functioned as a reproductive habitat, with only the rare presence of adult and older males in the MTS. The preservation of this track record in across a paleosol surface, although heavily trampled by different animals, including Neanderthals, over a short time frame, permitted an exceptional view into short-term intraspecific trophic interactions occurring in the Last Interglacial coastal habitat. Therefore, it is hypothesized that Neanderthals visited MTS for hunting or scavenging on weakened or dead elephants, and more likely calves.


2021 ◽  
Author(s):  
KIRAN MORE ◽  
Sheila Aiyer ◽  
Ashish Goti ◽  
Manan Parikh ◽  
Samir Sheikh ◽  
...  

Abstract Multisystem inflammatory syndrome(MIS) in children (MIS-C) associated with severe acute respiratory syndrome coronavirus-2 (SARS-CoV2) is well recognised in children, however, rarely reported in newborns. We describe a case series of 20 neonates who were diagnosed as MIS in neonates (MIS-N). We grouped cases into three categories as Most likely MIS(5), Possible MIS(9) and Unlikely MIS(6). All neonates had high titres of SARS CoV 2 IgG antibodies and were negative for SARS CoV 2 antigens. The most common clinical findings noted in Most Likely MIS neonates were respiratory distress (4/5), shock with hypotension (4/5) and encephalopathy (4/5). Inflammatory markers like CRP (1/5), Procalcitonin (1/5), Ferritin (3/5), D-dimer (4/5) and LDH (2/5) were found to be elevated, and four of them had significantly high levels of proBNP. The majority of them (4/5) responded to immunomodulators, three discharged home and two neonates died. The most common clinical findings in Possible MIS infants were fever (6/9), respiratory distress (3/9), refusal to feeds (6/9), lethargy (5/9) and tachycardia (3/9). ProBNP as a marker of cardiac dysfunction was noted to be elevated in five infants correlating with Echocardiography in two. All infants in this group responded to immunomodulators.MIS-N manifested as a milder disease in term neonates than preterms, where it was a more severe presentation with cardiac dysfunction. The diagnosis of MIS-N can be challenging and requires a high index of suspicion and early, proactive management. However, it is also important to be cautious of incorrect or overdiagnosis of this condition during the current pandemic.


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