| 1. |
- Cronin, T. M., et al.
(author)
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Quaternary Sea-ice history in the Arctic Ocean based on a new Ostracode sea-ice proxy
- 2010
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In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 29:25-26, s. 3415-3429
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Journal article (peer-reviewed)abstract
- Paleo-sea-ice history in the Arctic Ocean was reconstructed using the sea-ice dwelling ostracode Acetabulastoma arcticum from late Quaternary sediments from the Mendeleyev, Lomonosov, and Gakkel Ridges, the Morris Jesup Rise and the Yermak Plateau. Results suggest intermittently high levels of perennial sea ice in the central Arctic Ocean during Marine Isotope Stage (MIS) 3 (25–45 ka), minimal sea ice during the last deglacial (16–11 ka) and early Holocene thermal maximum (11–5 ka) and increasing sea ice during the mid-to-late Holocene (5–0 ka). Sediment core records from the Iceland and Rockall Plateaus show that perennial sea ice existed in these regions only during glacial intervals MIS 2, 4, and 6. These results show that sea ice exhibits complex temporal and spatial variability during different climatic regimes and that the development of modern perennial sea ice may be a relatively recent phenomenon.
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| 2. |
- Jakobsson, Martin, 1966-, et al.
(author)
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An Arctic Ocean ice shelf during MIS 6 constrained by new geophysical and geological data
- 2010
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In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 29:25-26, s. 3505-3517
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Journal article (peer-reviewed)abstract
- The hypothesis of floating ice shelves covering the Arctic Ocean during glacial periods was developed in the 1970s. In its most extreme form, this theory involved a 1000 m thick continuous ice shelf covering the Arctic Ocean during Quaternary glacial maxima including the Last Glacial Maximum (LGM). While recent observations clearly demonstrate deep ice grounding events in the central Arctic Ocean, the ice shelf hypothesis has been difficult to evaluate due to a lack of information from key areas with severe sea ice conditions. Here we present new data from previously inaccessible, unmapped areas that constrain the spatial extent and timing of marine ice sheets during past glacials. These data include multibeam swath bathymetry and subbottom profiles portraying glaciogenic features on the Chukchi Borderland, southern Lomonosov Ridge north of Greenland, Morris Jesup Rise, and Yermak Plateau. Sediment cores from the mapped areas provide age constraints on the glaciogenic features. Combining these new geophysical and geological data with earlier results suggests that an especially extensive marine ice sheet complex, including an ice shelf, existed in the Amerasian Arctic Ocean during Marine Isotope Stage (MIS) 6. From a conceptual oceanographic model we speculate that the cold halocline of the Polar Surface Water may have extended to deeper water depths during MIS 6 inhibiting the warm Atlantic water from reaching the Amerasian Arctic Ocean and, thus, creating favorable conditions for ice shelf development. The hypothesis of a continuous 1000 m thick ice shelf is rejected because our mapping results show that several areas in the central Arctic Ocean substantially shallower than 1000 m water depth are free from glacial influence on the seafloor.
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| 3. |
- Shlien, Adam, et al.
(author)
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Direct Transcriptional Consequences of Somatic Mutation in Breast Cancer
- 2016
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In: Cell Reports. - : Elsevier BV. - 2211-1247. ; 16:7, s. 2032-2046
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Journal article (peer-reviewed)abstract
- Disordered transcriptomes of cancer encompass direct effects of somatic mutation on transcription, coordinated secondary pathway alterations, and increased transcriptional noise. To catalog the rules governing how somatic mutation exerts direct transcriptional effects, we developed an exhaustive pipeline for analyzing RNA sequencing data, which we integrated with whole genomes from 23 breast cancers. Using X-inactivation analyses, we found that cancer cells are more transcriptionally active than intermixed stromal cells. This is especially true in estrogen receptor (ER)-negative tumors. Overall, 59% of substitutions were expressed. Nonsense mutations showed lower expression levels than expected, with patterns characteristic of nonsense-mediated decay. 14% of 4,234 rearrangements caused transcriptional abnormalities, including exon skips, exon reusage, fusions, and premature polyadenylation. We found productive, stable transcription from sense-to-antisense gene fusions and gene-to-intergenic rearrangements, suggesting that these mutation classes drive more transcriptional disruption than previously suspected. Systematic integration of transcriptome with genome data reveals the rules by which transcriptional machinery interprets somatic mutation.
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| 4. |
- Björk, Göran, 1956, et al.
(author)
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Bathymetry and deep-water exchange across the central Lomonosov Ridge at 88°-89°N
- 2007
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In: Deep-Sea Research I. - : Elsevier BV. ; 54, s. 1197-1208
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Journal article (peer-reviewed)abstract
- Seafloor mapping of the central Lomonosov Ridge using a multibeam echo-sounder during the Beringia/Healy–Oden Trans-Arctic Expedition (HOTRAX) 2005 shows that a channel across the ridge has a substantially shallower sill depth than the 2500 m indicated in present bathymetric maps. The multibeam survey along the ridge crest shows a maximum sill depth of about 1870 m. A previously hypothesized exchange of deep water from the Amundsen Basin to the Makarov Basin in this area is not confirmed. On the contrary, evidence of a deep-water flow from the Makarov to the Amundsen Basin was observed, indicating the existence of a new pathway for Canadian Basin Deep Water toward the Atlantic Ocean. Sediment data show extensive current activity along the ridge crest and along the rim of a local Intra Basin within the ridge structure.
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| 7. |
- Darby, D.A., et al.
(author)
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Trans-Arctic Coring Expedition Results
- 2005
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In: EOS Transactions, American Geophysical Union, v. 86(52). ; , s. Abstract PP33A-1559
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Conference paper (other academic/artistic)
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| 8. |
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| 9. |
- Gleason, J. D., et al.
(author)
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Sources and cycling of mercury in the paleo Arctic Ocean from Hg stable isotope variations in Eocene and Quaternary sediments
- 2017
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In: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 197, s. 245-262
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Journal article (peer-reviewed)abstract
- Mercury stable isotopic compositions were determined for marine sediments from eight locations in the Arctic Ocean Basin. Mass dependent fractionation (MDF) and mass independent fractionation (MIF) of Hg stable isotopes were recorded across a variety of depositional environments, water depths, and stratigraphic ages. delta(202) Hg (MDF) ranges from -2.34% to -0.78%; Delta(199) Hg (MIF) from -0.18% to +0.12%; and Delta(201) Hg (MIF) from -0.29% to + 0.05% for the complete data set (n = 33). Holocene sediments from the Chukchi Sea and Morris Jesup Rise record the most negative Delta(199) Hg values, while Pleistocene sediments from the Central Arctic Ocean record the most positive Delta(199) Hg values. The most negative delta(202) Hg values are recorded in Pleistocene sediments. Eocene sediments (Lomonosov Ridge) show some overlap in their Hg isotopic compositions with Quaternary sediments, with a sample of the Arctic Ocean PETM (56 Ma) most closely matching the average Hg isotopic composition of Holocene Arctic marine sediments. Collectively, these data support a terrestrially-dominated Hg source input for Arctic Ocean sediment through time, although other sources, as well as influences of sea ice, atmospheric mercury depletion events (AMDEs), and anthropogenic Hg (in core top samples) on Hg isotopic signatures must also be considered.
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| 10. |
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| 11. |
- Jakobsson, Martin, et al.
(author)
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Glacial geomorphology of the Central Arctic Ocean : The Chukchi Borderland and the Lomonosov Ridge
- 2008
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In: Earth Surface Processes and Landforms. - : Wiley. - 0197-9337 .- 1096-9837. ; 33:4, s. 526-545
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Journal article (peer-reviewed)abstract
- The last decade of geophysical seafloor mapping in the Arctic Ocean from nuclear submarines and icebreakers reveals a wide variety of glaciogenic geomorphic features at water depths reaching 1000 in. These findings provide new and intriguing insights into the Quaternary glacial history of the Northern Hemisphere. Here we integrate multi- and single beam bathymetric data, chirp sonar profiles and sidescan images from the Chukchi Borderland and Lomonosov Ridge to perform a comparative morphological seafloor study. This investigation aims to elucidate the nature and provenance of ice masses that impacted the Arctic Ocean sea floor during the Quaternary. Mapped glaciogenic bedforms include iceberg keel scours, most abundant at water depths shallower than similar to 350-400 m, flutes and megascale glacial lineations extending as deep as similar to 1000 m below the present sea level, small drumlin-like features and morainic ridges and grounding-zone wedges. The combination of these features indicates that very large glacial ice masses extended into the central Arctic Ocean from surrounding North American and Eurasian ice sheets several times during the Quaternary. Ice shelves occupied large parts of the Arctic Ocean during glacial maxima and ice rises were formed over the Chukchi Borderland and portions of the Lomonosov Ridge. More geophysical and sediment core data combined with modeling experiments are needed to reconstruct the timing and patterns of these events.
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| 19. |
- Svendsen, JI, et al.
(author)
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Late quaternary ice sheet history of northern Eurasia
- 2004
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In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 23:11-13, s. 1229-1271
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Research review (peer-reviewed)abstract
- The maximum limits of the Eurasian ice sheets during four glaciations have been reconstructed: (1) the Late Saalian (> 140 ka), (2) the Early Weichselian (100-80 ka), (3) the Middle Weichselian (60-50 ka) and (4) the Late Weichselian (25-15 ka). The reconstructed ice limits are based on satellite data and aerial photographs combined with geological field investigations in Russia and Siberia, and with marine seismic- and sediment core data. The Barents-Kara Ice Sheet got progressively smaller during each glaciation, whereas the dimensions of the Scandinavian Ice Sheet increased. During the last Ice Age the Barents-Kara Ice Sheet attained its maximum size as early as 90-80,000 years ago when the ice front reached far onto the continent. A regrowth of the ice sheets occurred during the early Middle Weichselian, culminating about 60-50,000 years ago. During the Late Weichselian the Barents-Kara Ice Sheet did not reach the mainland east of the Kanin Peninsula, with the exception of the NW fringe of Taimyr. A numerical ice-sheet model, forced by global sea level and solar changes, was run through the full Weichselian glacial cycle. The modeling results are roughly compatible with the geological record of ice growth, but the model underpredicts the glaciations in the Eurasian Arctic during the Early and Middle Weichselian. One reason for this is that the climate in the Eurasian Arctic was not as dry then as during the Late Weichselian glacial maximum.
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| 21. |
- Wood, Laura D, et al.
(author)
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The genomic landscapes of human breast and colorectal cancers.
- 2007
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In: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 318:5853, s. 1108-1113
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Journal article (peer-reviewed)abstract
- Human cancer is caused by the accumulation of mutations in oncogenes and tumor suppressor genes. To catalog the genetic changes that occur during tumorigenesis, we isolated DNA from 11 breast and 11 colorectal tumors and determined the sequences of the genes in the Reference Sequence database in these samples. Based on analysis of exons representing 20,857 transcripts from 18,191 genes, we conclude that the genomic landscapes of breast and colorectal cancers are composed of a handful of commonly mutated gene "mountains" and a much larger number of gene "hills" that are mutated at low frequency. We describe statistical and bioinformatic tools that may help identify mutations with a role in tumorigenesis. These results have implications for understanding the nature and heterogeneity of human cancers and for using personal genomics for tumor diagnosis and therapy.
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