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  • 1
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    Constraints on Earth System Functioning at the Paleocene‐Eocene Thermal Maximum From the Marine Silicon Cycle (2020)
    AGU (American Geophysical Union) | Wiley
    Details
    Publication Date: 2023-02-08
    Description: The Paleocene‐Eocene Thermal Maximum (PETM, ca. 56 Ma) is marked by a negative carbon isotope excursion (CIE) and increased global temperatures. The CIE is thought to result from the release of 13C‐depleted carbon, although the source(s) of carbon and triggers for its release, its rate of release, and the mechanisms by which the Earth system recovered are all debated. Many of the proposed mechanisms for the onset and recovery phases of the PETM make testable predictions about the marine silica cycle, making silicon isotope records a promising tool to address open questions about the PETM. We analyzed silicon isotope ratios (δ30Si) in radiolarian tests and sponge spicules from the Western North Atlantic (ODP Site 1051) across the PETM. Radiolarian δ30Si decreases by 0.6‰ from a background of 1‰ coeval with the CIE, while sponge δ30Si remains consistent at 0.2‰. Using a box model to test the Si cycle response to various scenarios, we find the data are best explained by a weak silicate weathering feedback, implying the recovery was mostly driven by nondiatom organic carbon burial, the other major long‐term carbon sink. We find no resolvable evidence for a volcanic trigger for carbon release, or for a change in regional oceanography. Better understanding of radiolarian Si isotope fractionation and more Si isotope records spanning the PETM are needed to confirm the global validity of these conclusions, but they highlight how the coupling between the silica and carbon cycles can be exploited to yield insight into the functioning of the Earth system.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    The biogeochemical impact of glacial meltwater from Southwest Greenland (2019)
    Elsevier
    In:  Progress in Oceanography, 176 . Art.Nr. 102126.
    Details
    Publication Date: 2022-01-31
    Description: Highlights • Novel multi-disciplinary approach to tracing freshwater and particle transport into boundary currents; • Significant glacial inputs reach coastal waters and are transported rapidly offshore; • Low surface water dissolved silicon concentrations maintained by diatom activity despite strong glacial and benthic supplies. Abstract Biogeochemical cycling in high-latitude regions has a disproportionate impact on global nutrient budgets. Here, we introduce a holistic, multi-disciplinary framework for elucidating the influence of glacial meltwaters, shelf currents, and biological production on biogeochemical cycling in high-latitude continental margins, with a focus on the silica cycle. Our findings highlight the impact of significant glacial discharge on nutrient supply to shelf and slope waters, as well as surface and benthic production in these regions, over a range of timescales from days to thousands of years. Whilst biological uptake in fjords and strong diatom activity in coastal waters maintains low dissolved silicon concentrations in surface waters, we find important but spatially heterogeneous additions of particulates into the system, which are transported rapidly away from the shore. We expect the glacially-derived particles – together with biogenic silica tests – to be cycled rapidly through shallow sediments, resulting in a strong benthic flux of dissolved silicon. Entrainment of this benthic silicon into boundary currents may supply an important source of this key nutrient into the Labrador Sea, and is also likely to recirculate back into the deep fjords inshore. This study illustrates how geochemical and oceanographic analyses can be used together to probe further into modern nutrient cycling in this region, as well as the palaeoclimatological approaches to investigating changes in glacial meltwater discharge through time, especially during periods of rapid climatic change in the Late Quaternary.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    Format: text
    DOI: 10.1016/j.pocean.2019.102126
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Deglacial diatom production in the tropical North Atlantic driven by enhanced silicic acid supply (2016)
    Elsevier
    Details
    Publication Date: 2023-08-01
    Description: Major shifts in ocean circulation are thought to be responsible for abrupt changes in temperature and atmospheric CO2 during the last deglaciation, linked to variability in meridional heat transport and deep ocean carbon storage. There is also widespread evidence for shifts in biological production during these times of deglacial CO2 rise, including enhanced diatom production in regions such as the tropical Atlantic. However, it remains unclear as to whether this diatom production was driven by enhanced wind-driven upwelling or density-driven vertical mixing, or by elevated thermocline concentrations of silicic acid supplied to the surface at a constant rate. Here, we demonstrate that silicic acid supply at depth in the NE Atlantic was enhanced during the abrupt climate events of the deglaciation. We use marine sediment archives to show that an increase in diatom production during abrupt climate shifts could only occur in regions of the NE Atlantic where the deep supply of silicic acid could reach the surface. The associated changes are indicative of enhanced regional wind-driven upwelling and/or weakened stratification due to circulation changes during phases of weakened Atlantic meridional overturning. Globally near-synchronous pulses of diatom production and enhanced thermocline concentrations of silicic acid suggest that widespread deglacial surface-driven breakdown of stratification, linked to changes in atmospheric circulation, had major consequences for biological productivity and carbon cycling.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    North Atlantic EM-122 multibeam swath bathymetry collected during RRS Discovery cruise DY081 (links to raw files and gridded data) (2018)
    PANGAEA
    Details
    Publication Date: 2023-03-28
    Description: This data release includes 56,432 square kilometers of multibeam swath bathymetry collected during a 2017 (June - August) research expedition onboard the RRS Discovery, DY081, in the North Atlantic Ocean. DY081 was the first fieldwork component of a European Research Council funded project, ICY-LAB, led by Dr. K. Hendry from the University of Bristol to study nutrient cycling in the North Atlantic. Four sites of interest were surveyed with an EM-122 echosounder prior to scientific operations, such as CTD deployment, sediment coring, and/or ROV dives. The four sites were Orphan Knoll off the coast of Newfoundland, and Nuuk, Nasrsaq, and Cape Farewell off southwest Greenland. Multibeam data was also recorded and processed during transit between locations. Data from the study sites and transits (EM-122 raw .all files and 25-meter resolution grids) are provided.
    Keywords: CT; Discovery (2013); DY081; DY081_CapeFarewell; DY081_Narsaq; DY081_Nuuk; DY081_OrphanKnoll; DY081_Transit1; DY081_Transit2; DY081_Transit3; DY081_Transit4; DY081_Transit5; DY081-underway; EM122; EM122 multibeam echosounder; Event label; File content; File format; File name; File size; ICY-LAB; South Atlantic Ocean; Underway cruise track measurements; Uniform resource locator/link to file
    Type: Dataset
    Format: text/tab-separated-values, 80 data points
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    DATA PANGAEA
  • 5
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    Updated age model for OMEXII-9K based on recalibrated radiocarbon ages (2018)
    PANGAEA
    Details
    Publication Date: 2023-02-10
    Keywords: Age model; DEPTH, sediment/rock; OMEXII-9K_2; Tropical North Atlantic
    Type: Dataset
    Format: text/tab-separated-values, 85 data points
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    DATA PANGAEA
  • 6
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    Stable isotope data of benthic foraminifera from OMEXII-9K (2018)
    PANGAEA
    Details
    Publication Date: 2023-02-12
    Description: This data release contains stable isotope data from benthic foraminifera isolated from sediment core OMEXII-9K off the Iberian Margin, from 0 to 204cm, and an updated age model.
    Keywords: Cibicidoides pachyderma, δ13C; Cibicidoides pachyderma, δ13C standard deviation; Cibicidoides pachyderma, δ18O; Cibicidoides pachyderma, δ18O standard deviation; Cibicidoides wuellerstorfi, δ13C; Cibicidoides wuellerstorfi, δ13C, standard deviation; Cibicidoides wuellerstorfi, δ18O; Cibicidoides wuellerstorfi, δ18O standard deviation; DEPTH, sediment/rock; OMEXII-9K_2; Tropical North Atlantic
    Type: Dataset
    Format: text/tab-separated-values, 140 data points
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    DATA PANGAEA
  • 7
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    (Table 2b) Opal chemistry of sediment core MB_BC390
    PANGAEA
    Details
    Publication Date: 2023-05-12
    Keywords: Aluminium/Silicon ratio; BC; Box corer; DEPTH, sediment/rock; Marguerite Bay; MB_BC390; Standard deviation; Zinc/Silicon ratio
    Type: Dataset
    Format: text/tab-separated-values, 108 data points
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    DATA PANGAEA
  • 8
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    (Table 2a) Opal chemistry of sediment core MB_BC388
    PANGAEA
    Details
    Publication Date: 2023-05-12
    Keywords: Aluminium/Silicon ratio; BC; Box corer; DEPTH, sediment/rock; Marguerite Bay; MB_BC388; Standard deviation; Zinc/Silicon ratio
    Type: Dataset
    Format: text/tab-separated-values, 88 data points
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    DATA PANGAEA
  • 9
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    (Table 1) Opal chemistry of coastal Antarctic core-top sediments
    PANGAEA
    Details
    Publication Date: 2023-05-12
    Keywords: Aluminium/Silicon ratio; BC; Box corer; DEPTH, sediment/rock; Elevation of event; Event label; Latitude of event; Longitude of event; Marguerite Bay; MB_BC383; MB_BC384; MB_BC385; MB_BC386; MB_BC388; MB_BC390; MB_BC391; Standard deviation; Zinc/Silicon ratio
    Type: Dataset
    Format: text/tab-separated-values, 30 data points
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    DATA PANGAEA
  • 10
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    Opal chemistry of costal Antarctic sediments
    PANGAEA
    In:  Supplement to: Hendry, Katharine R; Rickaby, Rosalind E M (2008): Opal (Zn/Si) ratios as a nearshore geochemical proxy in coastal Antarctica. Paleoceanography, 23(2), PA2218, https://doi.org/10.1029/2007PA001576
    Details
    Publication Date: 2023-05-12
    Description: During the last 50 years, the Antarctic Peninsula has experienced rapid warming with associated retreat of 87% of marine and tidewater glacier fronts. Accelerated glacial retreat and iceberg calving may have a significant impact on the freshwater and nutrient supply to the phytoplankton communities of the highly productive coastal regions. However, commonly used biogenic carbonate proxies for nutrient and salinity conditions are not preserved in sediments from coastal Antarctica. Here we describe a method for the measurement of zinc to silicon ratios in diatom opal, (Zn/Si)opal, which is a potential archive in Antarctic marine sediments. A core top calibration from the West Antarctic Peninsula shows (Zn/Si)opal is a proxy for mixed layer salinity. We present down-core (Zn/Si)opal paleosalinity records from two rapidly accumulating sites taken from nearshore environments off the West Antarctic Peninsula which show an increase in meltwater input in recent decades. Our records show that the recent melting in this region is unprecedented for over 120 years.
    Type: Dataset
    Format: application/zip, 3 datasets
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    DATA PANGAEA
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