ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    facet.materialart.
    Unknown
    PANGAEA
    In:  Supplement to: Cook, Mea S; Keigwin, Lloyd D; Birgel, Daniel; Hinrichs, Kai-Uwe (2011): Repeated pulses of vertical methane flux recorded in glacial sediments from the southeast Bering Sea. Paleoceanography, 26(2), PA2210, https://doi.org/10.1029/2010PA001993
    Publication Date: 2020-01-17
    Description: here is controversy over the role of marine methane hydrates in atmospheric methane concentrations and climate change during the last glacial period. In this study of two sediment cores from the southeast Bering Sea (700 m and 1467 m water depth), we identify multiple episodes during the last glacial period of intense methane flux reaching the seafloor. Within the uncertainty of the radiocarbon age model, the episodes are contemporaneous in the two cores and have similar timing and duration as Dansgaard-Oeschger events. The episodes are marked by horizons of sediment containing 13C-depleted authigenic carbonate minerals; 13C-depleted archaeal and bacterial lipids, which resemble those found in ANME-1 type anaerobic methane oxidizing microbial consortia; and changes in the abundance and species distribution of benthic foraminifera. The similar timing and isotopic composition of the authigenic carbonates in the two cores is consistent with a region-wide increase in the upward flux of methane bearing fluids. This study is the first observation outside Santa Barbara Basin of pervasive, repeated methane flux in glacial sediments. However, contrary to the "Clathrate Gun Hypothesis" (Kennett et al., 2003), these coring sites are too deep for methane hydrate destabilization to be the cause, implying that a much larger part of the ocean's sedimentary methane may participate in climate or carbon cycle feedback at millennial timescales. We speculate that pulses of methane in these opal-rich sediments could be caused by the sudden release of overpressure in pore fluids that builds up gradually with silica diagenesis. The release could be triggered by seismic shaking on the Aleutian subduction zone caused by hydrostatic pressure increase associated with sea level rise at the start of interstadials.
    Type: Dataset
    Format: application/zip, 11 datasets
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Publication Date: 2020-01-17
    Type: Dataset
    Format: text/tab-separated-values, 424 data points
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Publication Date: 2020-01-17
    Type: Dataset
    Format: text/tab-separated-values, 232 data points
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    facet.materialart.
    Unknown
    PANGAEA
    In:  Supplement to: Caissie, Beth; Brigham-Grette, Julie; Lawrence, Kira T; Herbert, Timothy D; Cook, Mea S (2010): Last Glacial Maximum to Holocene sea surface conditions at Umnak Plateau, Bering Sea, as inferred from diatom, alkenone, and stable isotope records. Paleoceanography, 25(1), PA1206, https://doi.org/10.1029/2008PA001671
    Publication Date: 2020-01-17
    Description: The Bering Sea gateway between the Pacific and Arctic oceans impacts global climate when glacial-interglacial shifts in shore line position and ice coverage change regional albedo. Previous work has shown that during the last glacial termination and into the Holocene, sea level rises and sea ice coverage diminishes from perennial to absent. Yet, existing work has not quantified sea ice duration or sea surface temperatures (SST) during this transition. Here we combine diatom assemblages with the first alkenone record from the Bering Sea to provide a semiquantitative record of sea ice duration, SST, and productivity change since the Last Glacial Maximum (LGM). During the LGM, diatom assemblages indicate that sea ice covered the southeastern Bering Sea perennially. At 15.1 cal ka B.P., the diatom assemblage shifts to one more characteristic of seasonal sea ice and alkenones occur in the sediments in low concentrations. Deglaciation is characterized by laminated intervals with highly productive and diverse diatom assemblages and inferred high coccolithophorid production. At 11.3 cal ka B.P. the diatom assemblage shifts from one dominated by sea ice species to one dominated by a warmer water, North Pacific species. Simultaneously, the SST increases by 3°C and the southeastern Bering Sea becomes ice-free year-round. Productivity and temperature proxies are positively correlated with independently dated records from elsewhere in the Bering Sea, the Sea of Okhotsk, and the North Pacific, indicating that productivity and SST changes are coeval across the region.
    Type: Dataset
    Format: text/tab-separated-values, 20 data points
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Publication Date: 2020-01-18
    Type: Dataset
    Format: text/tab-separated-values, 90 data points
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Publication Date: 2020-01-18
    Type: Dataset
    Format: text/tab-separated-values, 84 data points
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    facet.materialart.
    Unknown
    PANGAEA
    In:  Supplement to: Galbraith, Eric D; Jaccard, Samuel L; Pedersen, Thomas F; Sigman, Daniel M; Haug, Gerald H; Cook, Mea S; Southon, John R; Francois, Roger (2007): Carbon dioxide release from the North Pacific abyss during the last deglaciation. Nature, 449(7164), 890-894, https://doi.org/10.1038/nature06227
    Publication Date: 2020-01-18
    Description: Atmospheric carbon dioxide concentrations were significantly lower during glacial periods than during intervening interglacial periods, but the mechanisms responsible for this difference remain uncertain. Many recent explanations call on greater carbon storage in a poorly ventilated deep ocean during glacial periods (Trancois et al., 1997, doi:10.1038/40073; Toggweiler, 1999, doi:10.1029/1999PA900033; Stephens and Keeling, 2000, doi:10.1038/35004556; Marchitto et al., 2007, doi:10.1126/science.1138679; Sigman and Boyle, 2000, doi:10.1038/35038000), but direct evidence regarding the ventilation and respired carbon content of the glacial deep ocean is sparse and often equivocal (Broecker et al., 2004, doi:10.1126/science.1102293). Here we present sedimentary geochemical records from sites spanning the deep subarctic Pacific that -together with previously published results (Keigwin, 1998, doi:10.1029/98PA00874)- show that a poorly ventilated water mass containing a high concentration of respired carbon dioxide occupied the North Pacific abyss during the Last Glacial Maximum. Despite an inferred increase in deep Southern Ocean ventilation during the first step of the deglaciation (18,000-15,000 years ago) (Marchitto et al., 2007, doi:10.1126/science.1138679; Monnin et al., 2001, doi:10.1126/science.291.5501.112), we find no evidence for improved ventilation in the abyssal subarctic Pacific until a rapid transition ~14,600 years ago: this change was accompanied by an acceleration of export production from the surface waters above but only a small increase in atmospheric carbon dioxide concentration (Monnin et al., 2001, doi:10.1126/science.291.5501.112). We speculate that these changes were mechanistically linked to a roughly coeval increase in deep water formation in the North Atlantic (Robinson et al., 2005, doi:10.1126/science.1114832; Skinner nd Shackleton, 2004, doi:10.1029/2003PA000983; McManus et al., 2004, doi:10.1038/nature02494), which flushed respired carbon dioxide from northern abyssal waters, but also increased the supply of nutrients to the upper ocean, leading to greater carbon dioxide sequestration at mid-depths and stalling the rise of atmospheric carbon dioxide concentrations. Our findings are qualitatively consistent with hypotheses invoking a deglacial flushing of respired carbon dioxide from an isolated, deep ocean reservoir periods (Trancois et al., 1997, doi:10.1038/40073; Toggweiler, 1999, doi:10.1029/1999PA900033; Stephens and Keeling, 2000, doi:10.1038/35004556; Marchitto et al., 2007, doi:10.1126/science.1138679; Sigman and Boyle, 2000, doi:10.1038/35038000; Boyle, 1988, doi:10.1038/331055a0), but suggest that the reservoir may have been released in stages, as vigorous deep water ventilation switched between North Atlantic and Southern Ocean source regions.
    Type: Dataset
    Format: application/zip, 2 datasets
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    facet.materialart.
    Unknown
    Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
    Publication Date: 2017-01-05
    Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February, 2006
    Description: In this thesis, I present high-resolution stable-isotope and planktonic-fauna records from Bering Sea sediment cores, spanning the time period from 50,000 years ago to the present. During Marine Isotope Stage 3 (MIS3) at 30-20 ky BP (kiloyears before present) in a core from 1467m water depth near Umnak Plateau, there were episodic occurrences of diagenetic carbonate minerals with very low δ13C (-22:4h), high δ18O (6.5h), and high [Mg]/[Ca], which seem associated with sulfate reduction of organic matter and possibly anaerobic oxidation of methane. The episodes lasted less than 1000 years and were spaced about 1000 years apart. During MIS3 at 55-20 ky BP in a core from 2209m water depth on Bowers Ridge, N. pachyderma (s.) and Uvigerina δ18O and δ13C show no coherent variability on millennial time scales. Bering Sea sediments are dysoxic or laminated during the deglaciation. A high sedimentation rate core (200 cm/ky) from 1132m on the Bering Slope is laminated during the Bolling warm phase, Allerod warm phase, and early Holocene, where the ages of lithological transitions agree with the ages of those climate events in Greenland (GISP2) to well within the uncertainty of the age models. The subsurface distribution of radiocarbon was estimated from a compilation of published and unpublished North Pacific benthic-planktonic 14C measurements (475-2700 m water depth). There was no consistent change in 14C profiles between the present and the Last Glacial Maximum, Bolling-Allerod, or the Younger Dryas cold phase. N. pachyderma (s.) δ18O in the Bering Slope core decreases rapidly (in less than 220 y) by 0.7-0.8% at the onset of the Bolling and the end of the Younger Dryas. These isotopic shifts are accompanied by transient decreases in the relative abundance of N. pachyderma (s.), suggesting that the isotopic events are transient warmings and sustained freshenings.
    Description: The work in this thesis was supported by the National Science Foundation award OPP-9912122 to Lloyd Keigwin, the Oak Foundation of Boston, Massachusetts, the Stanley Watson Fellowship, the Paul Fye Fellowship, and the Academic Programs Office at WHOI.
    Keywords: Paleoceanography ; Marine sediments ; Healy (Ship) Cruise HLY02-02
    Repository Name: Woods Hole Open Access Server
    Type: Thesis
    Format: 2917694 bytes
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Publication Date: 2017-01-04
    Description: Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 30 (2015): 174–195, doi:10.1002/2014PA002649.
    Description: During the last deglaciation, the ventilation of the subarctic Pacific is hypothesized to have changed dramatically, including the rejuvenation of a poorly ventilated abyssal water mass that filled the deep ocean, and fluctuations in the strength of North Pacific intermediate and deep water formation at millennial timescales. Foraminiferal radiocarbon reconstructions of past ventilation changes in the Pacific are valuable but are hampered by poor carbonate preservation, low sediment accumulation rates, bias from bioturbation, and poorly constrained past surface reservoir age. In this study, we present paired benthic-planktonic radiocarbon measurements from the Okhotsk Sea and Emperor Seamounts. We take advantage of large contemporaneous peaks in benthic abundances from the last glacial maximum, Bolling-Allerod (BA), and early Holocene to produce time slices of radiocarbon from 1 to 4 km water depth. We explore the impact of uncertain surface reservoir age and evaluate several approaches to quantifying past ocean radiocarbon distribution using our NW Pacific data and a compilation of published data from the North Pacific. Both the calendar age and the absolute value of an ocean radiocarbon estimate depend on the assumed surface reservoir age. But for a time slice from a small geographical area with radiocarbon-independent stratigraphic correlation between cores, the shape of a water column profile is independent of surface reservoir age. The NW Pacific profiles are similar in shape to the compilation profiles for the entire North Pacific, which suggests that deglacial surface reservoir age changes across the N Pacific did not diverge dramatically across the areas sampled. The Last Glacial Maximum (LGM) profile 〉2 km spans a wide range of values, ranging from values similar to today to lower than today. However, by the BA the profile has a similar shape to today. Ultimately, local surface reservoir ages, end-member water mass composition, and mixing ratios must each be constrained before a radiocarbon activity reconstruction can be used to confidently infer ventilation changes.
    Description: Support for this project was from NSF grants 0526764, 8312240, and 9912122, and the Williams College Divisional Research Funding Committee. M.S.C. participated in the GAIN writing retreat, which was support by NSF grants 0620101 and 0620087.
    Description: 2015-09-12
    Keywords: Deglaciation ; Radiocarbon ; Pacific Ocean ; Ocean circulation
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
    Format: image/gif
    Format: text/plain
    Format: application/postscript
    Format: text/csv
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Publication Date: 2017-01-05
    Description: Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B. V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 52 (2005): 2163-2173, doi:10.1016/j.dsr2.2005.07.004.
    Description: The lithology of deglacial sediments from the Bering Sea includes intervals of laminated or dysaerobic sediments. These intervals are contemporaneous with the occurrence of laminated sediments from the California margin and Gulf of California, which suggests widespread low-oxygen conditions at intermediate depths in the North Pacific Ocean. The cause could be reduced intermediate water ventilation, increased organic carbon flux, or a combination of the two. We infer abrupt decreases of planktonic foraminifer δ18O at 14,400 y BP and 11,650 y BP, which may be a combination of both freshening and warming. On the Shirshov Ridge, the abundance of sea-ice diatoms of the genus Nitzschia reach local maxima twice during the deglaciation, the latter of which may be an expression of the Younger Dryas. These findings expand the extent of the expression of deglacial millennial-scale climate events to include the northernmost Pacific.
    Description: The Oak Foundation of Boston, Massachusetts, and the WHOI Academic Programs Office provided support for Mea Cook. This project was funded by NSF grant OPP-9912122.
    Keywords: Anoxic sediments ; Deglaciation ; Diatoms ; Foraminifera ; Oxygen isotope stratigraphy ; Bering Sea
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: 278378 bytes
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...