Subsurface heat channel drove sea surface warming in the high-latitude North Atlantic during the Mid-Pleistocene Transition

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Catunda, M. C. A., Bahr, A., Kaboth-Bahr, S., Zhang, X., Foukal, N. P., & Friedrich, O. Subsurface heat channel drove sea surface warming in the high-latitude North Atlantic during the Mid-Pleistocene Transition. Geophysical Research Letters, 48(11), (2021): e2020GL091899, https://doi.org/10.1029/2020GL091899.The Mid-Pleistocene Transition (MPT, 1,200–600 ka) marks the rapid expansion of Northern Hemisphere (NH) continental ice sheets and stronger precession pacing of glacial/interglacial cyclicity. Here, we investigate the relationship between thermocline depth in the central North Atlantic, subsurface northward heat transport and the initiation of the 100-kyr cyclicity during the MPT. To reconstruct deep-thermocline temperatures, we generated a Mg/Ca-based temperature record of deep-dwelling (∼800 m) planktonic foraminifera from mid-latitude North Atlantic at Site U1313. This record shows phases of pronounced heat accumulation at subsurface levels during the mid-MPT glacial driven by increased outflow of the Mediterranean Sea. Concurrent warming of the subtropical thermocline and subpolar surface waters indicates enhanced (subsurface) inter-gyre transport of warm water to the subpolar North Atlantic, which provided moisture for ice-sheet growth. Precession-modulated variability in the northward transport of subtropical waters imprinted this orbital cyclicity into NH ice-sheets after Marine Isotope Stage 24.Catunda and A. Bahr were funded by DFG project BA 3809/8, O.F. by DFG project FR 2544/11. S. Kaboth-Bahr acknowledges an Open-Topic Post-Doc Grant from the University of Potsdam. X.Z. was funded via the Lanzhou University (project 225000–830006) and National Science Foundation of China (Grant 42075047). N.F. was funded by the NSF Grant 1756361. Open access funding enabled and organized by Projekt DEAL

The Product of the Saccharomyces Cerevisiae RSS1 Gene, Identified as a High-Copy Suppressor of the Rat7-1 Temperature-Sensitive Allele of the RAT7/NUP159 Nucleoporin, is Required for Efficient mRNA Export

RAT7/NUP159 was identified previously in a screen for genes whose products are important for nucleocytoplasmic export of poly(A)+ RNA and encodes an essential nucleoporin. We report here the identification of RSS1 (Rat Seven Suppressor) as a high-copy extragenic suppressor of the rat7-1 temperature-sensitive allele. Rss1p encodes a novel essential protein of 538 amino acids, which contains an extended predicted coiled-coil domain and is located both at nuclear pore complexes (NPCs) and in the cytoplasm. RSS1 is the first reported high-copy extragenic suppressor of a mutant nucleoporin. Overexpression of Rss1p partially suppresses the defects in nucleocytoplasmic export of poly(A)+ RNA, rRNA synthesis and processing, and nucleolar morphology seen in rat7-1 cells shifted to the nonpermissive temperature of 37 degrees C and, thus, restores these processes to levels adequate for growth at a rate approximately one-half that of wild-type cells. After a shift to 37 degrees C, the mutant Rat7-1p/Nup159-1p is lost from the nuclear rim of rat7-1 cells and NPCs, which are clustered together in these cells grown under permissive conditions become substantially less clustered. Overexpression of Rss1p did not result in retention of the mutant Rat7-1p/Nup159-1p in NPCs, but it did result in partial maintenance of the NPC-clustering phenotype seen in mutant cells. Depletion of Rss1p by placing the RSS1 open reading frame (ORF) under control of the GAL1 promoter led to cessation of growth and nuclear accumulation of poly(A)+ RNA without affecting nuclear protein import or nuclear pore complex distribution, suggesting that RSS1 is directly involved in mRNA export. Because both rat7-1 cells and cells depleted for Rss1p are defective in mRNA export, our data are consistent with both gene products playing essential roles in the process of mRNA export and suggest that Rss1p overexpression suppresses the growth defect of rat7-1 cells at 37 degrees C by acting to maintain mRNA export

Systematic analyses of radiocarbon ages of coexisting planktonic foraminifera

We compare radiocarbon (14C) ages of coexisting planktonic foraminifera species from sediment cores VM12-107 and KNR166-2-26JPC from the Equatorial Atlantic Ocean for three time periods (Holocene, Heinrich Stadial 1, last glacial maximum). We find a maximum inter-species difference of 1200 14C yr. On average, the 14C ages deviate by ∼300 yr between Globigerinoides ruber and other species. In most cases, this exceeds the analytical uncertainty range of the measurements and thus renders the choice of species for generating age models as important as sample weight. While modern stratified water-column profiles imply an increase in 14C ages with water depth, we observe an expected parallel increase of 14C ages and δ18O only at VM12-107. The mismatch between 14C ages and δ18O at KNR166-2-26JPC likely results from the effects of bioturbation and the hydrographic setting. The largest difference in 14C ages between mixed-layer versus thermocline-calcifying planktonic foraminifera are observed during Heinrich Stadial 1 despite a decrease in upper-ocean stratification at that time. This difference is likely the result of inconsistent increases in 14C reservoir ages during times of reduced overturning circulation masking the potential of 14C ages of coexisting planktonic foraminifera to reflect the density stratification of the water column

Mediterranean Outflow and surface water variability off southern Portugal during the early Pleistocene: A snapshot at Marine Isotope Stages 29 to 34 (1020-1135 ka)

Centennial-to-millennial scale records from IODP Site U1387, drilled during IODP Expedition 339 into the Faro Drift at 558 m water depth, now allow evaluating the climatic history of the upper core of the Mediterranean Outflow (MOW) and of the surface waters in the northern Gulf of Cadiz during the early Pleistocene. This study focuses on the period from Marine Isotope Stages (MIS) 29 to 34, i.e. the interval surrounding extreme interglacial MIS 31. Conditions in the upper MOW reflect obliquity, precession and millennial-scale variations. The benthic delta O-18 signal follows obliquity with the exception of an additional, smaller delta O-18 peak that marks the MIS 32/31 transition. Insolation maxima (precession minima) led to poor ventilation and a sluggish upper MOW core, whereas insolation minima were associated with enhanced ventilation and often also increased bottom current velocity. Millennial-scale periods of colder sea-surface temperatures (SST) were associated with short-term maxima in flow velocity and better ventilation, reminiscent of conditions known from MIS 3.A prominent contourite layer, coinciding with insolation cycle 100, was formed during MIS 31 and represents one of the few contourites developing within an interglacial period. MIS 31 surface water conditions were characterized by an extended period (1065-1091 ka) of warm SST, but SST were not much warmer than during MIS 33. Interglacial to glacial transitions experienced 2 to 3 stadial/interstadial cycles, just like their mid-to-late Pleistocene counterparts. Glacial MIS 30 and 32 recorded periods of extremely cold (<12 degrees C) SST that in their climatic impact were comparable with the Heinrich events of the mid and late Pleistocene. Glacial MIS 34, on the other hand, was a relative warm glacial period off southern Portugal. Overall, surface water and MOW conditions at Site U1387 show a strong congruence with Mediterranean climate, whereas millennial-scale variations are closely linked to North Atlantic circulation changes. (C) 2015 Elsevier B.V. All rights reserved.Fundação para a Ciência e a Tecnologia (FCT; Portugal) through MOWCADYN project [PTDC/MAR-PRO/3761/2012]; FCT [SFRH/BPD/66025/2009]; Deutsche Forschungsgemeinschaft (DFG) [BA 3809/4, RO 1113/6]; MARUM Research Center; Spanish Ministry of Science and Innovation [CTM 2011-24079]; European Union [228344-EUROFLEETS]info:eu-repo/semantics/publishedVersio

The full-ORF clone resource of the German cDNA Consortium

<p>Abstract</p> <p>Background</p> <p>With the completion of the human genome sequence the functional analysis and characterization of the encoded proteins has become the next urging challenge in the post-genome era. The lack of comprehensive ORFeome resources has thus far hampered systematic applications by protein gain-of-function analysis. Gene and ORF coverage with full-length ORF clones thus needs to be extended. In combination with a unique and versatile cloning system, these will provide the tools for genome-wide systematic functional analyses, to achieve a deeper insight into complex biological processes.</p> <p>Results</p> <p>Here we describe the generation of a full-ORF clone resource of human genes applying the Gateway cloning technology (Invitrogen). A pipeline for efficient cloning and sequencing was developed and a sample tracking database was implemented to streamline the clone production process targeting more than 2,200 different ORFs. In addition, a robust cloning strategy was established, permitting the simultaneous generation of two clone variants that contain a particular ORF with as well as without a stop codon by the implementation of only one additional working step into the cloning procedure. Up to 92 % of the targeted ORFs were successfully amplified by PCR and more than 93 % of the amplicons successfully cloned.</p> <p>Conclusion</p> <p>The German cDNA Consortium ORFeome resource currently consists of more than 3,800 sequence-verified entry clones representing ORFs, cloned with and without stop codon, for about 1,700 different gene loci. 177 splice variants were cloned representing 121 of these genes. The entry clones have been used to generate over 5,000 different expression constructs, providing the basis for functional profiling applications. As a member of the recently formed international ORFeome collaboration we substantially contribute to generating and providing a whole genome human ORFeome collection in a unique cloning system that is made freely available in the community.</p

Onset of Mediterranean outflow into the North Atlantic

Sediments cored along the southwestern Iberian margin during Integrated Ocean Drilling Program Expedition 339 provide constraints on Mediterranean Outflow Water (MOW) circulation patterns from the Pliocene epoch to the present day. After the Strait of Gibraltar opened (5.33 million years ago), a limited volume of MOW entered the Atlantic. Depositional hiatuses indicate erosion by bottom currents related to higher volumes of MOW circulating into the North Atlantic, beginning in the late Pliocene. The hiatuses coincide with regional tectonic events and changes in global thermohaline circulation (THC). This suggests that MOW influenced Atlantic Meridional Overturning Circulation (AMOC), THC, and climatic shifts by contributing a component of warm, saline water to northern latitudes while in turn being influenced by plate tectonics

Gibraltar Outflow and Mediterranean overturning circulation during the last 500 ky

20th Congress of the International Union for Quaternary Research (INQUA). Dublin, 25th and 31st July 2019, AbstractsIn order to explore past changes in the Mediterranean Outflow Water (MOW) we analyzed the fine sand content in the sediments together with some geochemical proxies and planktic and benthic stable isotopes at IODP site U1389. This site was recovered in the vicinity of the Strait of Gibraltar along the path of the main core of the MOW. The content of fine sand together with Zr/Al ratios were used to investigate the MOW speed variability along the past 500 ky. The MOW speed variability at this site was mainly driven by changes in the density contrast between the Inflow and Outflow, which was, in turn, governed by changes in the Mediterranean heat and freshwater budgets. Events of enhanced freshwater input to the Mediterranean associated to northward shifts of the Intertropical convergence Zone reduced the density contrast at Gibraltar and weakened the MOW at Gibraltar. Weak MOW events were recorded at times of sapropel deposition in the eastern Mediterranean. At millennial scale, the MOW intensified at times of Greenland stadials and weakened during interstadials. However, during Heinrich stadials typical three-phase events were observed, with a sandy contourite layer at the bottom and top and a phase of weak MOW in the middle of the stadial, coinciding with the arrival of icebergs to the Gulf of Cadiz. For Heinrich stadial 1 this weak MOW event occurred at the time of the massive release of icebergs from the Laurentian ice sheets. However, the inflow of less saline water to the Mediterranean should have increased not decreased the density contrast between the Inflow and Outflow, especially because freshwater discharge to the Mediterranean from the African monsoons was extremely low. We propose different scenarios to explain these weak MOW events in the middle of Heinrich stadials that were certainly triggered by prominent changes in the Mediterranean heat and freshwater budget.Universidad de Salamanca, EspañaUniversity of Cambridge, Reino UnidoLeibniz-Laboratory for Radiometric Dating and Isotope Research, AlemaniaJapan Agency for Marine-Earth Science and Technology, JapónInstitute of Earth Sciences, Heidelberg University, AlemaniaRoyal Holloway, University of London, Reino UnidoSchool of Environmental Sciences, University of Hull, Reino UnidoInstituto Geológico y Minero de España, Españ

Spätglaziale bis Holozäne Paläoumweltentwicklung des Schwarzen Meeres

Paleoenvironmental changes in the Black Sea since the LGM were reconstructed using a multi-proxy approach. The hydrology and water chemistry of the Black Sea were significantly influenced by meltwater pulses originated from the Scandinavian Ice Sheet between 15.5 and 18 ka. The subsequent warming during Bölling/Alleröd and Early Holocene led to calcite precipitation, interrupted by the YD cold period. A steady increase in the d18O of Black Sea water was related to a higher d18O of the meteoric precipitation. Diverging d18O trends from different water depths indicate a stratification of the then lacustrine Black Sea. At 9.3 ka the inflow of Mediterranean water started as indicated by a drastic increase in the Mg/Ca and Sr/Ca of ostracod shells. High-frequent fluctuations in the river run-off of the Danube and Sakarya (Anatolia) rivers could be linked to the NAO. The data shows the persistence of the NAO-influence also during deglacial times and on millennial to decadal time scales

Late Glacial to Holocene paleoenvironmental evolution of the Black Sea

Paleoenvironmental changes in the Black Sea since the LGM were reconstructed using a multi-proxy approach. The hydrology and water chemistry of the Black Sea were significantly influenced by meltwater pulses originated from the Scandinavian Ice Sheet between 15.5 and 18 ka. The subsequent warming during Bölling/Alleröd and Early Holocene led to calcite precipitation, interrupted by the YD cold period. A steady increase in the d18O of Black Sea water was related to a higher d18O of the meteoric precipitation. Diverging d18O trends from different water depths indicate a stratification of the then lacustrine Black Sea. At 9.3 ka the inflow of Mediterranean water started as indicated by a drastic increase in the Mg/Ca and Sr/Ca of ostracod shells. High-frequent fluctuations in the river run-off of the Danube and Sakarya (Anatolia) rivers could be linked to the NAO. The data shows the persistence of the NAO-influence also during deglacial times and on millennial to decadal time scales