Swedish Museum of Natural History
Not a member yet
1516 research outputs found
Sort by
The Eocene-Oligocene transition: a review of marine and terrestrial proxy data, models and model-data comparisons
No full textThe Eocene–Oligocene transition (EOT) was a climate shift from a largely ice-free greenhouse world to an icehouse climate, involving the first major glaciation of Antarctica and global cooling occurring ∼ 34 million years ago (Ma) and lasting ∼ 790 kyr. The change is marked by a global shift in deep-sea δ18O representing a combination of deep-ocean cooling and growth in land ice volume. At the same time, multiple independent proxies for ocean tempera- ture indicate sea surface cooling, and major changes in global fauna and flora record a shift toward more cold-climate- adapted species. The two principal suggested explanations of this transition are a decline in atmospheric CO2 and changes to ocean gateways, while orbital forcing likely influenced the precise timing of the glaciation. Here we review and synthesise proxy evidence of palaeogeography, temperature, ice sheets, ocean circulation and CO2 change from the marine and terrestrial realms. Furthermore, we quantitatively com- pare proxy records of change to an ensemble of climate model simulations of temperature change across the EOT. The simulations compare three forcing mechanisms across the EOT: CO2 decrease, palaeogeographic changes and ice sheet growth. Our model ensemble results demonstrate the need for a global cooling mechanism beyond the imposition of an ice sheet or palaeogeographic changes. We find that CO2 forcing involving a large decrease in CO2 of ca. 40 % (∼ 325 ppm drop) provides the best fit to the available proxy evidence, with ice sheet and palaeogeographic changes play- ing a secondary role. While this large decrease is consistent with some CO2 proxy records (the extreme endmember of decrease), the positive feedback mechanisms on ice growth are so strong that a modest CO2 decrease beyond a critical threshold for ice sheet initiation is well capable of triggering rapid ice sheet growth. Thus, the amplitude of CO2 decrease signalled by our data–model comparison should be consid- ered an upper estimate and perhaps artificially large, not least because the current generation of climate models do not in- clude dynamic ice sheets and in some cases may be under- sensitive to CO2 forcing. The model ensemble also cannot exclude the possibility that palaeogeographic changes could have triggered a reduction in CO2.This research was alsosupported by the Bolin Centre for Climate Research (Research Area 6), and the Danish Council for Independent Research – Natural Sciences (DFF/FNU; grant no. 11-107497)</p
Brachiopods in early Mesozoic cryptic habitats: Continuous colonization, rapid adaptation, and wide geographic distribution
No full textLate Triassic and early Jurassic dikes and fissures in the Dachstein Limestone in the Northern Calcareous Alps harbor mass occurrences of the rhynchonellide brachiopods Sulcirostra juvavica and Halorella amphitoma. To test recent hypotheses about their paleoecology, we characterized these habitats using petrography, carbon stable isotopes, and trace element patterns, and found no evidence for hydrocarbon seepage or hydrothermal venting. Thus the brachiopods lived under normal-marine conditions, in darkness and absence of local photosynthetic primary production, hence relying on the supply of limited and presumably small-sized food washed into the dikes and fissures. Because Halorella and Sulcirostra occur in dikes and fissures since the beginning of their stratigraphic ranges, these rhynchonellides are not relics of formerly widely distributed taxa, but instead are two genera that rapidly adapted to these habitats. Both Halorella and Sulcirostra occur also in late Triassic and early Jurassic deep-water settings such as deep-marine sills and hydrocarbon seeps, indicating that close phylogenetic relationships between submarine cave faunas and deep-sea faunas, as seen today, existed also in the early Mesozoic, albeit among very different taxa. Another analogy to the modern cave fauna is the wide but disjunct geographic distribution of Sulcirostra and Halorella, both found throughout the Tethys and Panthalassa oceans. Our findings support the view that submarine cave habitats were continuously colonized by new taxa throughout Earth’s history.Financial support was provided by the Fonds zur Förderung der wissenschaftlichen Forschung (FWF) through grant M1779-N29 to Kiel and Peckmann</p
Palynology from ground zero of the Chicxulub impact, southern Gulf of Mexico
No full textPalynological analysis of Site M0077A in the Chicxulub impact crater has yielded a record of the immediate Cretaceous/Paleogene (K/Pg) recovery from ground zero of the end-Cretaceous mass extinction, followed by a record of the Paleocene–Eocene Thermal Maximum (PETM) and later Ypresian (Eocene), including the Early Eocene Climatic Optimum (EECO). Eight specimens of the dinoflagellate cyst Trithyrodinium evittii have been observed near the base of the K/Pg transitional unit; these likely representa post-impact dinoflagellate disaster recovery assemblage deposited within several days following the impact, although the possibility that some or all of the T. evittii specimens are reworked Maastrichtian cysts cannot be fully excluded. Despite high-resolution sampling of the lowermost Paleocene successions, the oldest identifiable terrestrial palynomorphs observed in the Site M0077A core, two specimens of Deltoidospora fern spores, occur at least c. 200,000 years after the impact. Other than these occurrences, the Paleocene section is nearly barren in terms of palynomorphs, likely a result of poor preservation of organic material combined with a long recovery time for vegetation in the vicinity of the crater. Pollen and fungal spore concentrations spike in an anoxic dark shale deposited during the PETM around 56 Ma, with a diverse pollen assemblage indicating the presence of a coastal shrubby tropical forest in the geographic vicinity, likely in the Yucatan Peninsula to the south. In the marine realm, this interval is characterized by thermophilic assemblages of dinoflagellate cysts. Stratigraphically constrained cluster analysis identified four statistically robust sample clusters in the lower Eocene successions, with Malvacipollis spp. and Milfordia spp. abundances driving the highest average dissimilarity between clusters. A second notable spike in palynological concentrations above the PETM section may represent another early Eocene hyperthermal event. Pollen and plant spore concentrations generally increased during the EECO, associated with increases in terrestrial input during basin infilling.Also funded by the Research Foundation Flanders (FWO grant 12Z6618N)</p
Near-future pCO2 during the hot Mid Miocene Climatic Optimum
No full textTo improve future predictions of anthropogenic climate change, a better understanding of the relationship between global temperature and atmospheric concentrations of CO2 (pCO2), orclimate sensitivity, is urgently required. Analyzing proxy data from climate change episodesin the past is necessary to achieve this goal, with certain geologic periods, such as the midMiocene Climatic Optimum (MCO), a transient period of global warming with globaltemperatures up to ~7°C higher than today, increasingly viewed as good analogues to future climate under present emission scenarios. However, a problem remains that climate modelscannot reproduce MCO temperatures with less than ~800 ppm pCO2, while most previously published proxies record pCO2 <450 ppm. Here, we reconstructed MCO pCO2 with a multitaxon fossil leaf database from the well-dated MCO Lagerstätte deposits of Clarkia, Idaho,USA, using four current methods of pCO2 reconstructions. The methods are principally based on either stomatal densities, carbon isotopes, or a combination of both – thus offering independent results. The total of six reconstructions mostly record pCO2 of ~450–550 ppm. Although slightly higher than previously reconstructed pCO2, the discrepancy with the ~800 ppm required by climate models remains. We conclude that climate sensitivity was heightened during MCO, indicating that highly elevated temperatures can occur at relatively moderate pCO2. Ever higher climate sensitivity with rising temperatures should be very seriously considered in future predictions of climate change
The Preliminary Analysis of Cave Lion Cubs Panthera spelaea (Goldfuss, 1810) from the Permafrost of Siberia
No full textModern Siberian dog ancestry was shaped by several thousand years of Eurasian-wide trade and human dispersal
No full textThe Hymenoptera collection of Lars Huggert housed in the Swedish Museum of Natural History
No full textIn the autumn of 2006 the large insect collection of Lars Huggert (1942–2003) was kindly donated to the Swedish Museum of Natural History in Stockholm by the siblings of the collector. A first assessment of the size of the collection, estimated more than 30 000 specimens of Coleoptera, 23 000 specimens of Hymenoptera and about 2 000 specimens of Diptera. Here an inventory of the Hymenoptera part of the Lars Huggert donation is given including an account of type specimens of 32 taxa described by Huggert and currently housed in NHRS. Specimens of more than 1 330 species of Hymenoptera were included in the donation which enriched the existing NHRS collections immensely. Huggert described 80 species and 34 genera/subgenera in the families Diapriidae Haliday, 1833, Platygastridae Haliday, 1833, Scelionidae, Haliday 1839 and Pteromalidae Dalman, 1820 and these families are particularly well-represented in the donation.Under sensommaren 2006 anlände Lars Huggerts insektssamling till Naturhistoriska Riksmuseet (NHRS). Vid en första uppskattning av samlingens storlek beräknades till att bestå av 30 000 torr- monterade skalbaggar, 23 000 steklar och 2 000 tvåvingar. I den här artikeln ges en översikt av stekeldelen i Lars Huggerts samling, samt en typlista för de 32 stekeltaxa beskrivna av Huggert som återfanns i den donerade samlingen. Dessa finns nu i NHRS typsamling och är registrerade i våra databaser. Donationen innehöll material av minst 1 330 olika arter av steklar. Stekelfamiljer som hyllhorn- steklar (Diapriidae Haliday, 1833), äggmärkarste- klar (Scelionidae Haliday, 1839) och gallmyggeste- klar (Platygastridae Haliday, 1833) var särskilt väl- representerade, och berikade museets samlingar med tiotusentals exemplar och minst 330 nya arter. Huggert beskrev under sin livstid 80 nya arter, 34 släkten och undersläkten och ett tribus, huvud- sakligen inom dessa familjer samt enstaka pupp- glanssteklar (Pteromalidae Dalman, 1820). Förutom ett rikt tillskott av de grupper som Huggert själv studerade flitigast, fanns även material av stekelgrupper som saknades helt (fikonsteklar, Agaonidae Walker, 1846) eller fanns mycket få av i NHRS samling; gropglanssteklar (Perilampidae Förster, 1856), Roproniidae Bradley, 1905, Monomachidae Ashmead, 1902 och Vanhorniidae Crawford, 1909. Sammantaget är detta ett enormt viktigt och värdefullt tillskott av små och dåligt kända steklar som folk sällan samlar in till stekelsamlingen på Naturhistoriska Riksmuseet. Samlingen kommer vara en viktig källa för forskare och studenter som vill studera små parasitsteklar
