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  • 2020-2024  (15)
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  • 1
    Publication Date: 2024-02-28
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉The ultimate demise of the Laurentide Ice Sheet (LIS) and the preceding and succeeding oceanographic changes along the western Labrador Sea offer insights critically important to improve climate predictions of expected future climate warming and further melting of the Greenland ice cap. However, while the final disappearance of the LIS during the Holocene is rather well constrained, the response of sea ice during the resulting meltwater events is not fully understood. Here, we present reconstructions of paleoceanographic changes over the past 9.3 Kyr BP on the northwestern Labrador Shelf, with a special focus on the interaction between the final meltwater event around 8.2 Kyr BP and sea ice and phytoplankton productivity (e.g., IP〈sub〉25〈/sub〉, HBI III (Z), brassicasterol, dinosterol, biogenic opal, total organic carbon). Our records indicate low sea‐ice cover and high phytoplankton productivity on the Labrador Shelf prior to 8.9 Kyr BP, sea‐ice formation was favored by decreased surface salinities due to the meltwater events from Lake Agassiz‐Ojibway and the Hudson Bay Ice Saddle from 8.55 Kyr BP onwards. For the past ca. 7.5 Kyr BP sea ice is mainly transported to the study area by local ocean currents such as the inner Labrador and Baffin Current. Our findings provide new insights into the response of sea ice to increased meltwater discharge as well as shifts in atmospheric and oceanic circulation.〈/p〉
    Description: Key Points: 〈list list-type="bullet"〉 〈list-item〉 〈p xml:lang="en"〉Sea ice on the Labrador Shelf mainly follows the solar insolation and meltwater input from the decaying Laurentide Ice Sheet〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉Sea ice increased following the Lake Agassiz outburst and Hudson Bay Ice Saddle Collapse between 8.5 and 8.2 Kyr BP〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉Low sea ice conditions during the Holocene Thermal Maximum were replaced by an increase following the Neoglacial cooling trend〈/p〉〈/list-item〉 〈/list〉 〈/p〉
    Description: Ocean Frontier Institute
    Description: NSERC
    Description: https://doi.org/10.4095/221564
    Description: https://doi.org/10.1594/PANGAEA.949244
    Description: https://doi.org/10.5281/zenodo.8247131
    Description: https://doi.org/10.1594/PANGAEA.949065
    Description: https://doi.org/10.1594/PANGAEA.949056
    Keywords: ddc:551.7 ; sea ice ; Atlantic Ocean ; IP25 ; 8.2 event
    Language: English
    Type: doc-type:article
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  • 2
    Publication Date: 2023-10-28
    Description: Diatom assemblage of sediment core M77/2_003-2
    Keywords: Actinocyclus curvatulus; Actinocyclus exiguus; Actinocyclus octonarius; Actinocyclus spp.; Actinoptychus senarius; Actinoptychus spp.; Actinoptychus vulgaris; Alveus marinus; Amphiascus minutus; Amphora spp.; Asteromphalus arachne; Azpeitia africana; Azpeitia nodulifera; Azpeitia tabularis; Biddulphia alternans; Biddulphia spp.; Cerataulina pelagica; Chaetoceros; Chaetoceros cinctus; Chaetoceros diadema; Chaetoceros didymus; Chaetoceros lorenzianus; Chaetoceros spp.; Climate - Biogeochemistry Interactions in the Tropical Ocean; Cocconeis californica; Cocconeis costata; Cocconeis dirupta; Cocconeis distans; Cocconeis placentula; Cocconeis scutellum; Cocconeis spp.; Coscinodiscus asteromphalus; Coscinodiscus centralis; Coscinodiscus concinnus; Coscinodiscus radiatus; Coscinodiscus spp.; Cyclotella spp.; Cyclotella striata; Cyclotella stylorum; Cymbella pusilla; Delphineis karstenii; DEPTH, sediment/rock; diatoms; Diatoms; Diploneis spp.; Discoaster spp.; Ditylum brightwellii; Eucampia spp.; Eunotia spp.; Eunotogramma debile; Fragilariopsis doliolus; Glyphodesmis distans; Grammatophora spp.; Hemiaulus spp.; Hemidiscus cuneiformis; M77/2; M77/2_003-2; M77/2_636-1; Meteor (1986); Minidiscus chilensis; Navicula spp.; Nitzschia bicapitata; Nitzschia gandersheimiensis; Nitzschia interruptestriata; Nitzschia ovalis; Nitzschia sicula; Odontella spp.; Paralia sulcata; PC; Peru; Phytoliths; Piston corer; Plagiogramma tessalatum; Plagiogrammopsis vanheurckii; Planktonellia sol; Pleurosigma spp.; Proboscia alata; Pseudogomphonema spp.; Pseudo-nitzschia pungens; Pseudosolenia calcar-avis; Radiolarians; Rhizosolenia acicularis; Rhizosolenia acuminata; Rhizosolenia bergonii; Rhizosolenia castracanei; Rhizosolenia clevei; Rhizosolenia decipiens; Rhizosolenia hyalina; Rhizosolenia imbricata; Rhizosolenia spp.; Roperia tessellata; SFB754; Silicoflagellates; Skeletonema costatum; Sponge spiculae; Stephanopyxis spp.; Thalassionema bacillaris; Thalassionema nitzschioides; Thalassionema nitzschioides var. capitulata; Thalassionema nitzschioides var. claviformis; Thalassionema nitzschioides var. inflata; Thalassionema nitzschioides var. lanceolata; Thalassionema nitzschioides var. nitzschioides; Thalassionema nitzschioides var. parva; Thalassiosira eccentrica; Thalassiosira leptopus; Thalassiosira oestrupii; Thalassiosira pacifica; Thalassiosira spp.; Thalassiothrix longissima; Trachyneis spp.
    Type: Dataset
    Format: text/tab-separated-values, 8295 data points
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  • 3
    Publication Date: 2023-10-28
    Description: The dataset comprises all d30Si signatures and biogenic opal content (%) of core M772_003-2 off Peru
    Keywords: AGE; biogenic opal; Climate - Biogeochemistry Interactions in the Tropical Ocean; DEPTH, sediment/rock; Diatoms, δ30Si; M77/2; M77/2_003-2; M77/2_636-1; Meteor (1986); Opal, biogenic silica; PC; Peru; Piston corer; Sample code/label; SFB754; Standard deviation; δ30Si, biogenic silica
    Type: Dataset
    Format: text/tab-separated-values, 486 data points
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  • 4
    Publication Date: 2024-02-21
    Description: Biogenic opal (BSi) concentrations were analysed as indicator for past primary productivity on gravity core MSM45_19-2 from the northern Labrador Shelf. Gravity core MSM45_19-2 was obtained during R/V Maria S. Merian expedition MSM45 (58°45.68'N, 61°56.25'W, water depth: 202 m) in 2015 (Schneider et al., 2016). Biogenic opal was determined at Dalhousie University following the method of (Mortlock and Froelich , 1989). Briefly, amorphous silica was extracted from ca. 20 mg subsamples using a 2 M Na2 CO3 solution at 85°C for 5 h, followed by the measurement of dissolved silica concentrations by molybdenum blue spectrophotometry.
    Keywords: 8.2 ka event; Accumulation rate, biogenic silica per year; Accumulation rate per year; After Mortlock and Froelich (1981); biogenic opal; DEPTH, sediment/rock; GC; Gravity corer; Holocene; Labrador Sea; Labrador Shelf; Maria S. Merian; MSM45; MSM45_418-2; MSM45-19-2; Opal, biogenic silica; primary production
    Type: Dataset
    Format: text/tab-separated-values, 655 data points
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  • 5
    Publication Date: 2024-04-18
    Description: The dataset comprises all d30Si signatures (bSiO2 and Coscinodiscus) of surface sediments off Peru
    Keywords: biogenic opal; Climate - Biogeochemistry Interactions in the Tropical Ocean; DEPTH, water; Event label; LATITUDE; LONGITUDE; M77/1; M77/1_420-1; M77/1_450-1; M77/1_462-1; M77/1_469-1; M77/1_471-1; M77/1_482-1; M77/1_543-1; M77/1_615-1; M77/1_620-1; M77/1_623-1; M77/2; M77/2_002-5; M77/2_005-5; M77/2_022-2; M77/2_028-2; M77/2_029-5; M77/2_045-3; M77/2_050-1; M77/2_052-3; M77/2_053-1; M77/2_060-1; M77/2_062-2; M77/2_067-2; M77/2_076-2; M77/2_635-6; M77/2_649-1; M77/2_669; M77/2_685; M77/2_692; M77/2_717; M77/2_727; M77/2_734; M77/2_736; M77/2_756; M77/2_762; M77/2_776; M77/2_800; Meteor (1986); MUC; MultiCorer; Multicorer with television; Peru; SFB754; Standard deviation; TVMUC; δ30Si; δ30Si, biogenic silica
    Type: Dataset
    Format: text/tab-separated-values, 67 data points
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  • 6
    Publication Date: 2024-04-20
    Description: Eastern boundary upwelling systems (EBUS) are among the most productive marine ecosystems on Earth. The production of organic material is fueled by upwelling of nutrient-rich deep waters and high incident light at the sea surface. However, biotic and abiotic factors can mod- ify surface production and related biogeochemical processes. Determining these factors is important because EBUS are considered hotspots of climate change, and reliable predic- tions of their future functioning requires understanding of the mechanisms driving the biogeochemical cycles therein. In this field experiment, we used in situ mesocosms as tools to improve our mechanistic understanding of processes con- trolling organic matter cycling in the coastal Peruvian up- welling system. Eight mesocosms, each with a volume of ∼ 55 m3, were deployed for 50 d ∼ 6 km off Callao (12◦ S) during austral summer 2017, coinciding with a coastal El Niño phase. After mesocosm deployment, we collected sub- surface waters at two different locations in the regional oxy- gen minimum zone (OMZ) and injected these into four meso- cosms (mixing ratio ≈ 1.5 : 1 mesocosm: OMZ water). The focus of this paper is on temporal developments of organic matter production, export, and stoichiometry in the indi- vidual mesocosms. The mesocosm phytoplankton commu- nities were initially dominated by diatoms but shifted to- wards a pronounced dominance of the mixotrophic dinoflag- ellate (Akashiwo sanguinea) when inorganic nitrogen was exhausted in surface layers. The community shift coincided with a short-term increase in production during the A. san- guinea bloom, which left a pronounced imprint on organic matter C : N : P stoichiometry. However, C, N, and P export fluxes did not increase because A. sanguinea persisted in the water column and did not sink out during the experiment. Accordingly, export fluxes during the study were decou- pled from surface production and sustained by the remain- ing plankton community. Overall, biogeochemical pools and fluxes were surprisingly constant for most of the experiment. We explain this constancy by light limitation through self- shading by phytoplankton and by inorganic nitrogen limita- tion which constrained phytoplankton growth. Thus, gain and loss processes remained balanced and there were few oppor- tunities for blooms, which represents an event where the sys- tem becomes unbalanced. Overall, our mesocosm study re- vealed some key links between ecological and biogeochem- ical processes for one of the most economically important regions in the oceans.
    Keywords: Binary Object; Binary Object (File Size); Binary Object (Media Type); Climate - Biogeochemistry Interactions in the Tropical Ocean; KOSMOS_2017; KOSMOS_2017_Peru; KOSMOS Peru; MESO; Mesocosm experiment; SFB754
    Type: Dataset
    Format: text/tab-separated-values, 11 data points
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  • 7
    Publication Date: 2024-06-12
    Description: We determined dissolved stable silicon isotopes along with silicic acid concentrations in geochemically well-characterized seawater samples recovered during the expeditions TRANSDRIFT-XX (TI12, March and April 2012), TRANSDRIFT-XXI (VB13, August and September 2013) and TRANSDRIFT-XXII (VB14, September and October 2014) to the Laptev Sea. During the winter TRANSDRIFT-XX expedition, samples were collected using 2-l-Niskin bottles mounted on a frame at several helicopter stations to the sea ice, while during the summer expeditions TRANSDRIFT-XXI and TRANSDRIFT-XXII the samples were recovered with a carousel water sampler equipped with 12 Niskin bottles (2.5 L) under ice-free conditions onboard the Russian research vessel RV Viktor Buynitskiy on the entire Laptev Sea shelf and above the shelf slope. The dataset includes dissolved stable silicon isotope and silicic acid concentration data, which provide important information on the distribution and biogeochemical cycling of silicon and other nutrients in the Laptev Sea.
    Keywords: Arctic Ocean; Bottle, Nansen; calculated, 2 sigma; CTD/Rosette; CTD-RO; DATE/TIME; Depth, bathymetric; DEPTH, water; Event label; Helicopter; Laptev Sea; LATITUDE; LONGITUDE; NAS; nutrient; silicate; Silicate; stable Si isotopes; Station label; System Laptev-Sea: Transdrift; TI12_02-3; TI12_05-3; TI12_06-2; TI12_07-2; TI12_10-3; TRANSDRIFT; Transdrift-XX; Transdrift-XXI; Transdrift-XXII; VB13; VB13_10-1; VB13_1-1a; VB13_12-1; VB13_14-1; VB13_15-2; VB13_16-1; VB13_17-1; VB13_18-1; VB13_19-1; VB13_20-1; VB13_3-3d; VB13_5-4; VB13_7-3; VB13_8-1; VB13_9-1; VB14; VB14_11-1d; VB14_11-1e; VB14_12-1c; VB14_12-1d; VB14_13-1c; VB14_13-1e; VB14_15-7-1b; VB14_16-1c; VB14_16-1d; VB14_17-1d; VB14_17-1e; VB14_17-1f; VB14_18-1a; VB14_19-2d; VB14_19-2e; VB14_21-1c; VB14_21-1f; VB14_2-1c; VB14_2-1d; VB14_23-1d; VB14_26-1b; VB14_4-2e; VB14_4-2f; VB14_4-2g; VB14_4-2h; VB14_5-1d; VB14_5-1e; VB14_6-3c; VB14_6-3d; VB14_7-1c; VB14_7-1d; VB14_8-1c; VB14_8-1d; Viktor Buynitskiy; δ29Si, silicic acid; δ29Si, silicic acid, standard deviation; δ30Si, silicic acid; δ30Si, silicic acid, standard deviation
    Type: Dataset
    Format: text/tab-separated-values, 546 data points
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  • 8
    Publication Date: 2023-02-08
    Description: Benthic fluxes of dissolved silica (Si) from sediments into the water column are driven by the dissolution of biogenic silica (bSiO2) and terrigenous Si minerals and modulated by the precipitation of authigenic Si phases. Each of these processes has a specific effect on the isotopic composition of silica dissolved in sediment pore waters such that the determination of pore water δ30Si values can help to decipher the complex Si cycle in surface sediments. In this study, the δ30Si signatures of pore fluids and bSiO2 in the Guaymas Basin (Gulf of California) were analyzed, which is characterized by high bSiO2 accumulation and hydrothermal activity. The δ30Si signatures were investigated in the deep basin, in the vicinity of a hydrothermal vent field, and at an anoxic site located within the pronounced oxygen minimum zone (OMZ). The pore fluid δ30Sipf signatures differ significantly depending on the ambient conditions. Within the basin, δ30Sipf is essentially uniform averaging +1.2 ± 0.1 ‰ (1SD). Pore fluid δ30Sipf values from within the OMZ are significantly lower (0.0 ± 0.5 ‰, 1SD), while pore fluids close to the hydrothermal vent field are higher (+2.0 ± 0.2 ‰, 1SD). Reactive transport modelling results show that the δ30Sipf is mainly controlled by silica dissolution (bSiO2 and terrigenous phases) and Si precipitation (authigenic aluminosilicates). Precipitation processes cause a shift to high pore fluid δ30Sipf signatures, most pronounced at the hydrothermal site. Within the OMZ however, additional dissolution of isotopically depleted Si minerals (e.g. clays) facilitated by high mass accumulation rates of terrigenous material (MARterr) is required to promote the low δ30Sipf signatures while precipitation of authigenic aluminosilicates seems to be hampered by high water / rock ratios. Guaymas OMZ δ30Sipf values are markedly different from those of the Peruvian OMZ, the only other marine setting where Si isotopes have been investigated to constrain early diagenetic processes. These differences highlight the fact that δ30Sipf signals in OMZs worldwide are not alike and each setting can result in a range of δ30Sipf values as a function of the environmental conditions. We conclude that the benthic silica cycle is more complex than previously thought and that additional Si isotope studies are needed to decipher the controls on Si turnover in marine sediment and the role of sediments in the marine silica cycle.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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  • 9
    Publication Date: 2023-02-08
    Description: Estuarine systems are of key importance for the riverine input of silicon (Si) to the ocean, which is a limiting factor of diatom productivity in coastal areas. This study presents a field dataset of surface dissolved Si isotopic compositions (30SiSi(OH)4) obtained in the estuaries of three of the world’s largest rivers, the Amazon (ARE), Yangtze (YRE), and Pearl (PRE), which cover different climate zones. While 30SiSi(OH)4 behaved conservatively in the YRE and PRE supporting a dominant control by water mass mixing, significantly increased 30SiSi(OH)4 signatures due to diatom utilization of Si(OH)4 were observed in the ARE and reflected a Si isotopic enrichment factor 30 of −1.0±0.4‰ (Rayleigh model) or −1.6±0.4‰ (steady state model). In addition, seasonal variability of Si isotope behavior in the YRE was observed by comparison to previous work and most likely resulted from changes in water residence time, temperature, and light level. Based on the 30 value obtained for the ARE, we estimate that the global average 30SiSi(OH)4 entering the ocean is 0.2-0.3‰ higher than that of the rivers due to Si retention in estuaries. This systematic modification of riverine Si isotopic compositions during estuarine mixing, as well as the seasonality of Si isotope dynamics in single estuaries, needs to be taken into account for better constraining the role of large river estuaries in the oceanic Si cycle.
    Type: Article , PeerReviewed
    Format: text
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  • 10
    Publication Date: 2023-02-08
    Description: Eastern boundary upwelling systems (EBUS) are among the most productive marine ecosystems on Earth. The production of organic material is fueled by upwelling of nutrient-rich deep waters and high incident light at the sea surface. However, biotic and abiotic factors can modify surface production and related biogeochemical processes. Determining these factors is important because EBUS are considered hotspots of climate change, and reliable predictions of their future functioning requires understanding of the mechanisms driving the biogeochemical cycles therein. In this field experiment, we used in situ mesocosms as tools to improve our mechanistic understanding of processes controlling organic matter cycling in the coastal Peruvian upwelling system. Eight mesocosms, each with a volume of ∼55 m3, were deployed for 50 d ∼6 km off Callao (12∘ S) during austral summer 2017, coinciding with a coastal El Niño phase. After mesocosm deployment, we collected subsurface waters at two different locations in the regional oxygen minimum zone (OMZ) and injected these into four mesocosms (mixing ratio ≈1.5 : 1 mesocosm: OMZ water). The focus of this paper is on temporal developments of organic matter production, export, and stoichiometry in the individual mesocosms. The mesocosm phytoplankton communities were initially dominated by diatoms but shifted towards a pronounced dominance of the mixotrophic dinoflagellate (Akashiwo sanguinea) when inorganic nitrogen was exhausted in surface layers. The community shift coincided with a short-term increase in production during the A. sanguinea bloom, which left a pronounced imprint on organic matter C : N : P stoichiometry. However, C, N, and P export fluxes did not increase because A. sanguinea persisted in the water column and did not sink out during the experiment. Accordingly, export fluxes during the study were decoupled from surface production and sustained by the remaining plankton community. Overall, biogeochemical pools and fluxes were surprisingly constant for most of the experiment. We explain this constancy by light limitation through self-shading by phytoplankton and by inorganic nitrogen limitation which constrained phytoplankton growth. Thus, gain and loss processes remained balanced and there were few opportunities for blooms, which represents an event where the system becomes unbalanced. Overall, our mesocosm study revealed some key links between ecological and biogeochemical processes for one of the most economically important regions in the oceans.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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