scholarly journals Spatial distribution of benthic foraminiferal stable isotopes and dinocyst assemblages in surface sediments of the Trondheimsfjord, central Norway

2013 ◽  
Vol 10 (3) ◽  
pp. 5889-5921 ◽  
Author(s):  
G. Milzer ◽  
J. Giraudeau ◽  
J. Faust ◽  
J. Knies ◽  
F. Eynaud ◽  
...  
Keyword(s):  
Organic Matter ◽  
Climatic Variability ◽  
Intermediate Water ◽  
North Atlantic Current ◽  
Local Conditions ◽  
Bottom Water Temperature ◽  
The North ◽  
Show Evidence ◽  
Matter Flux ◽  
Instrumental Records

Abstract. Instrumental records from the Norwegian Sea and the Trondheimsfjord show evidence that changes of bottom water temperature and salinity in the fjord are linked to the salinity and temperature variability of the North Atlantic Current (NAC). Changes in primary productivity and salinity in the surface and intermediate water masses in the Trondheimsfjord as well as the fjord sedimentary budget are mainly driven by changes in riverine input. In this study we use 59 surface sediment samples that are evenly distributed in the fjord to examine whether dinocyst assemblages and stable isotope ratios of benthic foraminifera reflect the present-day hydrology and can be used as paleoceanographic proxies. In general, modern benthic δ18O and δ13C values decrease from the fjord entrance towards the fjord head with lowest values close to river inlets. This is essentially explained by gradients in the amounts of freshwater and terrigenous organic matter delivered from the hinterland. The distribution of benthic δ13C ratios across the fjord is controlled by both the origin (terrigenous vs. marine) of organic matter and local topography-induced variability in organic matter flux at the water-sediment interface. The dinocyst assemblages display the variations in hydrography with respect to the prevailing currents, the topography, and the freshwater and nutrient supply from rivers. The strength and depth of the pycnocline in the fjord strongly varies seasonally and thereby affects water mass characteristics as well as nutrient availability, temporally creating local conditions that explain the observed species distribution. Our results prove that dinocyst assemblages and benthic foraminiferal isotopes reliably mirror the complex fjord hydrology and can therefore be used as proxies of Holocene climatic variability.

scholarly journals Spatial distribution of benthic foraminiferal stable isotopes and dinocyst assemblages in surface sediments of the Trondheimsfjord, central Norway

2013 ◽  
Vol 10 (7) ◽  
pp. 4433-4448 ◽  
Author(s):  
G. Milzer ◽  
J. Giraudeau ◽  
J. Faust ◽  
J. Knies ◽  
F. Eynaud ◽  
...  
Keyword(s):  
Organic Matter ◽  
Climatic Variability ◽  
Intermediate Water ◽  
North Atlantic Current ◽  
Local Conditions ◽  
Bottom Water Temperature ◽  
The North ◽  
Show Evidence ◽  
Matter Flux ◽  
Instrumental Records

Abstract. Instrumental records from the Norwegian Sea and the Trondheimsfjord show evidence that changes of bottom water temperature and salinity in the fjord are linked to the salinity and temperature variability of the North Atlantic Current (NAC). Changes in primary productivity and salinity in the surface and intermediate water masses in the Trondheimsfjord as well as the fjord sedimentary budget are mainly driven by changes in riverine input. In this study we use 59 surface sediment samples that are evenly distributed in the fjord to examine whether dinocyst assemblages and stable isotope ratios of benthic foraminifera reflect the present-day hydrology and can be used as palaeoceanographic proxies. In general, modern benthic δ18O and δ13C values decrease from the fjord entrance towards the fjord head with lowest values close to river inlets. This is essentially explained by gradients in the amounts of fresh water and terrigenous organic matter delivered from the hinterland. The distribution of benthic δ13C ratios across the fjord is controlled by the origin (terrigenous vs. marine) of organic matter, local topography-induced variability in organic matter flux at the water–sediment interface, and organic matter degradation. The dinocyst assemblages display the variations in hydrography with respect to the prevailing currents, the topography, and the freshwater and nutrient supply from rivers. The strength and depth of the pycnocline in the fjord strongly vary seasonally and thereby affect water mass characteristics as well as nutrient availability, temporally creating local conditions that explain the observed species distribution. Our results prove that dinocyst assemblages and benthic foraminiferal isotopes reliably mirror the complex fjord hydrology and can be used as proxies of Holocene climatic variability.

A multi-proxy reconstruction of climate during the late-Pleistocene to early Holocene transition in the northeastern, USA

2021 ◽  
pp. 1-17
Author(s):  
Laurie D. Grigg ◽  
Kevin J. Engle ◽  
Alison J. Smith ◽  
Bryan N. Shuman ◽  
Maximilian B. Mandl
Keyword(s):  
Late Pleistocene ◽  
Climatic Variability ◽  
Warming Trend ◽  
Early Holocene ◽  
Individual Species ◽  
Environmental Preferences ◽  
The North ◽  
Show Evidence ◽  
Dry Conditions ◽  
Components Analysis

Abstract A multiproxy record from Twin Ponds, VT, is used to reconstruct climatic variability during the late Pleistocene to early Holocene transition. Pollen, ostracodes, δ18O, and lithologic records from 13.5 to 9.0 cal ka BP are presented. Pollen- and ostracode-inferred climatic reconstructions are based on individual species’ environmental preferences and the modern analog technique. Principal components analysis of all proxies highlights the overall warming trend and centennial-scale climatic variability. During the Younger Dryas cooling event (YD), multiple proxies show evidence for cold winter conditions and increasing seasonality after 12.5 cal ka BP. The early Holocene shows an initial phase of rapid warming with a brief cold interval at 11.5 cal ka BP, followed by a more gradual warming; a cool, wet period from 11.2 to 10.8 cal ka BP; and cool, dry conditions from 10.8 to 10.2 cal ka BP. The record ends with steady warming and increasing moisture. Post-YD climatic variability has been observed at other sites in the northeastern United States and points to continued instability in the North Atlantic during the final phases of deglaciation.

scholarly journals A 36 kyr geochemical record from the Sea of Japan of organic matter flux variations and changes in intermediate water oxygen concentrations

1999 ◽  
Vol 14 (2) ◽  
pp. 248-259 ◽  
Author(s):  
John Crusius ◽  
Thomas F. Pedersen ◽  
Stephen E. Calvert ◽  
Gregory L. Cowie ◽  
Tadamichi Oba
Keyword(s):  
Organic Matter ◽  
Sea Of Japan ◽  
The Sea Of Japan ◽  
Intermediate Water ◽  
Water Oxygen ◽  
Matter Flux ◽  
Oxygen Concentrations

scholarly journals FACTORS CONTROLLING THE RECENT SEDIMENTATION IN THE UPPER CONTINENTAL SLOPE OF THE JACUÍPE BASIN (NE BRAZIL)

2018 ◽  
Vol 2 (4) ◽  
pp. 250-273
Author(s):  
Maria Virginia Alves Martins ◽  
Egberto Pereira ◽  
Sérgio Bergamaschi ◽  
Denise Terroso ◽  
Paulo Miranda ◽  
...  
Keyword(s):  
Organic Matter ◽  
Continental Slope ◽  
Bottom Sediments ◽  
Compositional Data ◽  
Northern Region ◽  
Conditioning Factors ◽  
The North ◽  
Anoxic Environments ◽  
North Brazil ◽  
Matter Flux

This work is based on textural, mineralogical (XRD) and compositional data of 50 bottom sediments’ samples in the upper continental slope between 80-1000 m water depth of the Jacuípe Basin, northern region of Bahia State (Brazil). It intends to study the recent sedimentary coverture and infer possible conditioning factors influencing the recent sedimentation in this region. Despite the study area has been considered oligotrophic, pyrite that is supposed to be mostly the result of the initial diagenetic processes of organic matter degradation, occurs throughout the upper slope of the Jacuípe Basin. The organic matter flux is abundant enough to establish anoxic environments or microenvironments favorable to the formation and preservation of pyrite. The textural, mineralogical and compositional data allow us to define latitudinal and longitudinal variations of bottom sediments possibly influenced by changes in the geomorphology of the study area and hydrodynamic conditions. The supply of detrital sediments to the southern region seems to be scarce but relatively more abundant in the northern part, closer to the São Francisco River delta. The northern region is also more favorable to sediment deposition than the southern one, where erosional processes appear to be more common. This difference may also be ascribed to the process of formation of the Brazil Current, and its southward development. A significant compositional change of sediments was observed at about 435 m depth possibly due to the enhanced influence of the North Brazil Undercurrent.

Signatures of rapid climatic changes in organic matter records in the western Mediterranean Sea during the last glacial period

2007 ◽  
Vol 178 (1) ◽  
pp. 3-13 ◽  
Author(s):  
François Baudin ◽  
Nathalie Combourieu-Nebout ◽  
Rainer Zahn
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Mediterranean Sea ◽  
North Atlantic ◽  
River Runoff ◽  
Western Mediterranean ◽  
Terrestrial Organic Matter ◽  
The North ◽  
The North Atlantic ◽  
Matter Flux

Abstract Records of calcium carbonate, organic matter (organic carbon content, palynology) and planktonic foraminiferal oxygen isotopes from ODP Site 976, Alboran Sea, are used to reconstruct the evolution of continental climates and oceanic productivity in the westernmost Mediterranean over the past 50,000 years. The records mimic the Greenland ice core records in that they display the Heinrich events and the rapid Dansgaard/Oeschger-type stadial-interstadial oscillations. Warm interstadials correlate with an expansion of deciduous forests on the adjacent continents and enhanced river runoff and organic matter flux from terrestrial sources. In contrast, cold stadials are characterized by an expansion of semi-desert vegetation, reduced river runoff and limited terrestrial organic matter flux. The organic carbon record displays a longer-term cyclicity that correlates with the North Atlantic ’Bond’ cooling cycles. The records enable the documentation of rapid changes of continental climates in the western Mediterranean borderlands that caused changes in river runoff and in oceanic productivity that were driven by rapid fluctuations of the Atlantic inflow into the Mediterranean Sea. The combined terrestrial-marine patterns demonstrate the close linking of western Mediterranean climate with the climatic evolution in the North Atlantic region.

scholarly journals Eddies Observed by Argo Floats. Part I: Eddy Transport in the Upper 1000 dbar

2016 ◽  
Vol 46 (11) ◽  
pp. 3471-3486 ◽  
Author(s):  
Katsuro Katsumata
Keyword(s):  
North Atlantic ◽  
Kuroshio Extension ◽  
Intermediate Water ◽  
Diffusivity Coefficient ◽  
North Atlantic Current ◽  
Argo Floats ◽  
The North ◽  
South Indian ◽  
Eddy Transport ◽  
The North Atlantic

AbstractArgo floats measure horizontal current velocities at the parking depth and vertical profiles of temperature and salinity. The data are sufficient for simultaneous estimates of velocities and vertical displacements of isopycnal surfaces. More than 980 000 pairs of observations of current velocity and water column stratification were used to calculate eddy transport above 1000 dbar and its uncertainty based on the temporal-residual-mean framework. Eddy transports larger than 1.0 m2 s−1 were found in the North Atlantic, western North Pacific, and Southern Oceans. The eddy transport T had components perpendicular and parallel to the density contours at 1000 dbar. In the midlatitude oceans, eddy transport was weaker (<0.5 m2 s−1), mostly perpendicular to the density contours, and equatorward. A large area of northward was found in the south Indian Ocean; analysis of velocity and thickness perturbations suggested that this transport was a northward intrusion of Antarctic Intermediate Water. In the midlatitude oceans and in most of the southern part of the Antarctic Circumpolar Current (ACC), was generally upgradient in density on 1000 dbar. Downgradient was found along the North Atlantic Current and Kuroshio Extension as well as in the northern part of the ACC. Zonally integrated meridional transport was poleward at latitudes higher than approximately 40° and equatorward at lower latitudes. The quasi-Stokes or Gent–McWilliams diffusivity coefficient was on the order of 1000 m2 s−1 but was associated with such large uncertainty that it was statistically indistinguishable from zero, except at midlatitudes in the Southern Hemisphere.

Past changes in North Pacific (de)oxygenation – a complex interplay between water mass ventilation and organic matter respiration

2020 ◽  
Author(s):  
Samuel Jaccard
Keyword(s):  
Organic Matter ◽  
North Pacific ◽  
Critical Role ◽  
Meridional Overturning Circulation ◽  
Intermediate Water ◽  
Labile Organic Matter ◽  
Abrupt Decrease ◽  
Future Evolution ◽  
The North ◽  
The North Pacific

&lt;p&gt;The North Pacific basin has undergone large changes in subsurface oxygenation in the past. In general, oxygen-depleted zones increased volumetrically as climate warmed, with the rate of warming playing a critical role in determining the spatial extent of subsurface deoxygenation. The most pronounced deoxygenation episode in the upper ocean occurred midway through the deglaciation, an interval referred to as the Bolling/Allerod (B/A), associated with the reinvigoration of the Atlantic Meridional Overturning Circulation (AMOC). At this time, the upper Indo-Pacific ocean was probably less oxygenated than today. The B/A was characterized by substantial changes in intermediate water circulation, combined with efficient removal of oxygen associated with enhanced remineralization of labile organic matter, as export production increased throughout the subarctic North Pacific. The abrupt decrease in oxygenation affected large swaths of the North Pacific, including shelf environments with detrimental consequences for marine ecosystems.&lt;br&gt;This contribution will review the available paleoceanographic evidence spanning the last 3 million years and distill the salient constraints that can help better predicting the future evolution of North Pacific (de)oxygenation in the context of anthropogenic climate forcing.&lt;/p&gt;

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