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- Adler, Ruth E., et al.
(author)
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Sediment record from the western Arctic Ocean with an improved Late Quaternary age resolution : HOTRAX core HLY0503-8JPC, Mendeleev Ridge
- 2009
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In: Global and Planetary Change. - : Elsevier BV. - 0921-8181 .- 1872-6364. ; 68:02-jan, s. 18-29
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Journal article (peer-reviewed)abstract
- Sediment core HLY0503-8JPC raised by the HOTRAX'05 expedition from the Mendeleev Ridge was analyzed for multiple lithological, paleontological. and stable-isotopic proxies to reconstruct paleoceanographic conditions in the western Arctic Ocean during the Late Quaternary. The core, extensively sampled in the upper 5 m, reveals pronounced changes in sedimentary environments during the ca. 250 kyr interval encompassing Marine Isotopic Stages (MIS) 1 to 7. An estimated average resolution of 500 yr/sample, at least for the last glacial cycle including the last interglacial, provides more detail than seen in other sedimentary records from the western Arctic Ocean. The age control is provided by C-14 and amino acid racemization measurements on planktonic foraminifers and correlations with the stratigraphy developed for the central Lomonosov Ridge and with glacial events at the Eurasian Arctic margin. Cyclic variations in lithology combined with foraminiferal abundance and stable-isotopic composition indicate profound changes in hydrographic and depositional environments between interglacial-type and glacial-type periods apparently reflecting a combination of 100-kyr and precessional time scales. This periodicity is complicated by abrupt iceberg- and/or meltwater-discharge events with variable (Laurentide vs. Eurasian) provenance. The proxy record from the interval identified as the last interglacial (MIS 5e), which may aid in understanding the future state of the Arctic Ocean, indicates low ice conditions and possibly enhanced stratification of the water column.
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- Darby, Dennis, et al.
(author)
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The 2005 HOTRAX Expedition to the Arctic Ocean
- 2009
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In: Global and Planetary Change. - : Elsevier BV. - 0921-8181 .- 1872-6364. ; 68:1-2, s. 1-4
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Journal article (peer-reviewed)abstract
- The Healy–Oden Trans-Arctic Expedition (HOTRAX'05) recovered 29 long piston cores and associated multicores along a transect from the Alaskan margin across the central Arctic Ocean to the northern Svalbard margin. The initial results focus on the age and stratigraphy of these cores using a variety of approaches including radiocarbon, paleomagnetic and other chronostratigraphic methods as well as detailed correlations of proxy records. High sedimentation cores from probable drift deposits are described from the shelf and continental slope north of Alaska. Provenance and sedimentary processes in these deposits include both currents and sea-ice rafting. Much lower sedimentation rates in the central Arctic Ocean show geographic variability consistent with the patterns of expected sediment distribution by ice and, to a smaller extent, subsurface currents. Insights into the Upper Quaternary stratigraphy and depositional history are provided in two papers on a core from the Mendeleev Ridge with sedimentation rates relatively elevated for this region. To compliment the results from the HOTRAX cores, two papers are included dealing with the stratigraphy and sedimentary processes on the Chukchi shelf and a modeling study addressing why the Marine Isotopic Stage 6 (ca. 140 ka) glaciation was substantially more extensive in the Arctic than the Last Glacial Maximum.
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| 5. |
- Darby, Dennis, et al.
(author)
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The role of currents and sea ice in both slowly deposited central Arctic and rapidly deposited Chukchi-Alaskan margin sediments
- 2009
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In: Global and Planetary Change. - : Elsevier BV. - 0921-8181 .- 1872-6364. ; 68:1-2, s. 58-72
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Journal article (peer-reviewed)abstract
- A study of three long cores from the outer shelf and continental slope north of Alaska in the Arctic Ocean indicate that localized drift deposits occur here with sedimentation rates of more than 1.5 m/kyr during the Holocene. Currents in this area average about 5–20 cm/s but can reach 100 cm/s and these velocities transport the sediment found in these cores primarily as intermittent suspended load. These high accumulation sediments form levee-like deposits associated with margins of canyons cutting across the shelf and slope. Unlike most textural investigations of Arctic sediment that focus on the coarser ice-rafted detritus (IRD), this paper focuses on the > 95% of the sediment, which is finer than 45 μm. The mean size of this fraction varies between 6 and 15 μm in Holocene sediments from the Chukchi–Alaskan shelf and slope with the higher values closer to shore. Analysis of detailed size distributions of these Holocene deposits are compared to 34 sediment samples collected from sea ice across the Arctic Ocean and to Holocene sediment from central Arctic Ocean cores and indicate that similar textural parameters occur in all of these sediments. Principal components of these size distributions indicate that sea ice is an important link between the shelves and the central Arctic. Factor scores indicate nearly identical components in the clay and fine silt size fractions but very different components in the coarse silt for sea ice sediment and central Arctic ridge sediments compared to shelf and continental slope deposits. Sea ice must contribute to sedimentation in both of these Arctic regions, but bottom currents dominate in the slope region, forming drift deposits.
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| 10. |
- Hanslik, Daniela, et al.
(author)
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Late Pleistocene and Holocene benthic and planktonic foraminifera from the central Lomonosov Ridge
- 2007
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In: First Conference on Arctic Palaeoclimate and its Extremes (APEX).
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Conference paper (other academic/artistic)abstract
- Presently available bathymetric charts show that the area between about 88°15’–89°N and 140°–180°E of the Lomonosov Ridge is characterized by a >1000 m deep depression in the ridge morphology forming a local "intra basin". During the 2005 Beringia/Healy-Oden Trans-Arctic EXpedition (HOTRAX), a detailed investigation of this part of the Lomonosov Ridge was conducted including multibeam bathymetric mapping, subbottom profiling, hydrographic measurements and sediment coring (Darby et al., 2005). The subbottom profiles reveal an expanded sediment stratigraphy in the intra basin suggesting that the area have acted as a local sediment trap with higher sediment accumulation rates compared to the 1000 m shallower ridge crest (Björk et al., in press). Core HLY0503-18JPC, investigated in this study, was retrieved at 2598 m water depth from the floor of the intra basin. The top 68 cm of this 12 m long sediment core contain abundant calcareous nanno- and microfossils. For this study, the content of benthic and planktonic foraminifera was quantified. The number of specimens per gram sediment showed several major peaks and valleys. Peak abundances of benthic and planktonic foraminifera coincide well with each other. The largest peak occurs near the base of this 68 cm long calcareous-rich sequence. All calcareous microfossils are well preserved, showing no signs of dissolution in the larger grain size fraction (>150 m). Assemblage analyses of four samples, of the size fraction >150 m, show a dominant abundance of Neogloboquadrina pachyderma (sinistral), accounting for up to 99% of the assemblage. There is no complete age model yet established for core HLY0503-18JPC, although 14C dating made on tube worms and bryozoan mats show ages of 35.200 ± 1500 (radiocarbon yrs) at 28-29 cm core depth and 32.800 ± 1500 (radiocarbon yrs) at 39 cm indicating sedimentation rates of about 1 cm/kyr. These 14C ages are in stark contrast to the nannofossil stratigraphy where the most nannofossil rich samples found between 42 and 56 cm suggest a Holocene age (Fornaciari et al., 2006) implying several times higher sedimentation rates. Additional 14C dating will be carried out on planktonic and benthic foraminifera as a next step in this study.
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| 11. |
- Jakobsson, Martin, et al.
(author)
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Arctic Ocean glacial history
- 2014
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In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 92, s. 40-67
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Research review (peer-reviewed)abstract
- While there are numerous hypotheses concerning glacial interglacial environmental and climatic regime shifts in the Arctic Ocean, a holistic view on the Northern Hemisphere's late Quaternary ice-sheet extent and their impact on ocean and sea-ice dynamics remains to be established. Here we aim to provide a step in this direction by presenting an overview of Arctic Ocean glacial history, based on the present state-of-the-art knowledge gained from field work and chronological studies, and with a specific focus on ice-sheet extent and environmental conditions during the Last Glacial Maximum (LGM). The maximum Quaternary extension of ice sheets is discussed and compared to LGM. We bring together recent results from the circum-Arctic continental margins and the deep central basin; extent of ice sheets and ice streams bordering the Arctic Ocean as well as evidence for ice shelves extending into the central deep basin. Discrepancies between new results and published LGM ice-sheet reconstructions in the high Arctic are highlighted and outstanding questions are identified. Finally, we address the ability to simulate the Arctic Ocean ice sheet complexes and their dynamics, including ice streams and ice shelves, using presently available ice-sheet models. Our review shows that while we are able to firmly reject some of the earlier hypotheses formulated to describe Arctic Ocean glacial conditions, we still lack information from key areas to compile the holistic Arctic Ocean glacial history.
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| 15. |
- Polyak, Leonid, et al.
(author)
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History of sea ice in the Arctic
- 2010
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In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 29:15-16, s. 1757-1778
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Journal article (peer-reviewed)abstract
- Arctic sea-ice extent and volume are declining rapidly. Several studies project that the Arctic Ocean may become seasonally ice-free by the year 2040 or even earlier. Putting this into perspective requires information on the history of Arctic sea-ice conditions through the geologic past. This information can be provided by proxy records from the Arctic Ocean floor and from the surrounding coasts. Although existing records are far from complete, they indicate that sea ice became a feature of the Arctic by 47 Ma, following a pronounced decline in atmospheric pCO(2) after the Paleocene-Eocene Thermal Optimum, and consistently covered at least part of the Arctic Ocean for no less than the last 13-14 million years. Ice was apparently most widespread during the last 2-3 million years, in accordance with Earth's overall cooler climate. Nevertheless, episodes of considerably reduced sea ice or even seasonally ice-free conditions occurred during warmer periods linked to orbital variations. The last low-ice event related to orbital forcing (high insolation) was in the early Holocene, after which the northern high latitudes cooled overall, with some superimposed shorterterm (multidecadal to millennial-scale) and lower-magnitude variability. The current reduction in Arctic ice cover started in the late 19th century, consistent with the rapidly warming climate, and became very pronounced over the last three decades. This ice loss appears to be unmatched over at least the last few thousand years and unexplainable by any of the known natural variabilities.
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| 16. |
- Polyak, Leonid, et al.
(author)
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Quaternary sedimentation in the Arctic Ocean : Recent advances and further challenges
- 2011
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In: Oceanography. - : The Oceanography Society. - 1042-8275. ; 24:3, s. 52-64
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Journal article (peer-reviewed)abstract
- This paper reviews current knowledge of sedimentation patterns in the Arctic Ocean during the pronounced climatic cycles of the last several hundred thousand years, an especially relevant time period that provides long-term context for present climate change. The review is largely based on data collected during recent research icebreaker cruises to the Arctic Ocean, with a focus on the 2005 Healy-Oden TransArctic Expedition (HOTRAX) and 2007 Lomonosov Ridge Off Greenland (LOMROG) expedition. The sediment cores and geophysical seafloor mapping data collected enable reconstruction of past oceanic environments. Evaluation of these data suggests that the two major Arctic Ocean circulation systems, the Trans-Polar Drift and the Beaufort Gyre, persisted throughout most of the Late to Middle Quaternary, approximately the last 0.5 to 0.7 million years. Extreme conditions, nonanalogous to modern environments, also occurred in the past, especially during Pleistocene glacial intervals. Some of these intervals likely featured much thickened and/or concentrated sea ice and incursions of ice shelves and armadas of megasized icebergs from the margins to the center of the Arctic Ocean. In contrast, much warmer conditions with reduced sea ice extent existed during interglacial periods. Characterization of ice conditions during these intervals is critical for evaluating the present and projected future reduction of Arctic sea ice.
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| 17. |
- Polyak, Leonid, et al.
(author)
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Stratigraphic constraints on late Pleistocene glacial erosion and deglaciation of the Chukchi margin, Arctic Ocean
- 2007
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In: Quaternary Research. - : Cambridge University Press (CUP). - 0033-5894 .- 1096-0287. ; :67, s. 234-245
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Journal article (peer-reviewed)abstract
- At least two episodes of glacial erosion of the Chukchi margin at water depths to ca 450 m and 750 m have been indicated by geophysical seafloor data. We examine sediment stratigraphy in these areas to verify the inferred erosion and to understand its nature and timing. Our data within the eroded areas show the presence of glaciogenic diamictons composed mostly of reworked local bedrock. The diamictons are estimated to form during the last glacial maximum (LGM) and an earlier glacial event, possibly between OIS 4 to 5d. Both erosional events were presumablycaused by the grounding of ice shelves originating from the Laurentide ice sheet. Broader glaciological settings differed between these events as indicated by different orientations of flutes on eroded seafloor. Postglacial sedimentation evolved from iceberg-dominated environments to those controlled by sea-ice rafting and marine processes in the Holocene. A prominent minimum in planktonic foraminiferal δ18O is identified in deglacial sediments at an estimated age near 13,000 cal yr BP. This δ18O minimum, also reported elsewhere in the Amerasia Basin, is probably related to a major Laurentide meltwater pulse at the Younger Dryas onset. The Bering Strait opening is also marked in the composition of late deglacial Chukchi sediments.
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