scholarly journals Cenozoic evolution of the Campbell Plateau, Subantarctic New Zealand: Insights from sub-bottom profile data

2021 ◽  
Author(s):  
◽  
Benjamin Cathie
Keyword(s):  
Ocean Circulation ◽  
Large Scale ◽  
Profile Data ◽  
Ocean Drilling Program ◽  
Sedimentary Deposits ◽  
Sedimentary Sequences ◽  
Circumpolar Current ◽  
Wind Driven Currents ◽  
Erosional Event ◽  
Drill Cores

<p>The Campbell Plateau represents ~30% of the submerged continent of Zealandia and represents part of the Gondwana super-continent that began to break-up ~98Ma. The focus of this MSc thesis is to use sub-bottom, profile data collected in 2017 and 2018 from Campbell Plateau to improve our understanding of the Cenozoic evolution of the region. The sub-bottom profiles show a rugged basement overlain by a variety of sedimentary sequences and subsurface features such as volcanoes, onlap, and downlap surfaces as well as multiple unconformities that can be traced throughout the Cenozoic (65Ma). The sub-bottom profiles are compared to 2 drill cores; Ocean Drilling Program (ODP) site 1120 on the eastern side of the plateau and Deep Sea Drilling Program (DSDP) site 277 in the south. These drill cores indicate that the lithology from the Cretaceous onwards is predominantly biogenic calcareous sandstone and mudstone, which changes to nannofossil-rich oozes in the Miocene and foraminiferal oozes and nannofossil oozes dated early to late Pleistocene. The northern plateau appears to be relatively quiescent with thin, relatively uniform strata, only influenced by small reverse faults. Sedimentary deposits such as wedges and contourites are also evident in the central and north-western part of the study area. The southern plateau appears to be have been highly dynamic with onlap/downlap surfaces, interpreted as current scours, and erosional surfaces. There is a plateau-wide unconformity during the Pliocene, as derived from the nannofossils of the ODP1120 drill core, which appears to have been a large-scale erosional event. The Southern Ocean circulation, dominated by Antarctic Circumpolar Current, the Subtropical Front, and local wind-driven currents, are the main drivers of these lithological changes and plateau-wide sedimentological structures.  Previous interpretations of the sub-surface structure of the plateau are seen to be invalid in relation to this study, with the sub-surface seen to be relatively undeformed with only minor reverse faulting present. Areas of possible uplifted basement seen near Campbell Island also indicate that the Campbell Plateau has been through substantial erosion and deformation since its’ separation from Gondwana ~98Ma and movement to its modern-day position.</p>

scholarly journals Cenozoic evolution of the Campbell Plateau, Subantarctic New Zealand: Insights from sub-bottom profile data

2021 ◽  
Author(s):  
◽  
Benjamin Cathie
Keyword(s):  
Ocean Circulation ◽  
Large Scale ◽  
Profile Data ◽  
Ocean Drilling Program ◽  
Sedimentary Deposits ◽  
Sedimentary Sequences ◽  
Circumpolar Current ◽  
Wind Driven Currents ◽  
Erosional Event ◽  
Drill Cores

<p>The Campbell Plateau represents ~30% of the submerged continent of Zealandia and represents part of the Gondwana super-continent that began to break-up ~98Ma. The focus of this MSc thesis is to use sub-bottom, profile data collected in 2017 and 2018 from Campbell Plateau to improve our understanding of the Cenozoic evolution of the region. The sub-bottom profiles show a rugged basement overlain by a variety of sedimentary sequences and subsurface features such as volcanoes, onlap, and downlap surfaces as well as multiple unconformities that can be traced throughout the Cenozoic (65Ma). The sub-bottom profiles are compared to 2 drill cores; Ocean Drilling Program (ODP) site 1120 on the eastern side of the plateau and Deep Sea Drilling Program (DSDP) site 277 in the south. These drill cores indicate that the lithology from the Cretaceous onwards is predominantly biogenic calcareous sandstone and mudstone, which changes to nannofossil-rich oozes in the Miocene and foraminiferal oozes and nannofossil oozes dated early to late Pleistocene. The northern plateau appears to be relatively quiescent with thin, relatively uniform strata, only influenced by small reverse faults. Sedimentary deposits such as wedges and contourites are also evident in the central and north-western part of the study area. The southern plateau appears to be have been highly dynamic with onlap/downlap surfaces, interpreted as current scours, and erosional surfaces. There is a plateau-wide unconformity during the Pliocene, as derived from the nannofossils of the ODP1120 drill core, which appears to have been a large-scale erosional event. The Southern Ocean circulation, dominated by Antarctic Circumpolar Current, the Subtropical Front, and local wind-driven currents, are the main drivers of these lithological changes and plateau-wide sedimentological structures.  Previous interpretations of the sub-surface structure of the plateau are seen to be invalid in relation to this study, with the sub-surface seen to be relatively undeformed with only minor reverse faulting present. Areas of possible uplifted basement seen near Campbell Island also indicate that the Campbell Plateau has been through substantial erosion and deformation since its’ separation from Gondwana ~98Ma and movement to its modern-day position.</p>

scholarly journals Study of the Antarctic Circumpolar Current via the Shallow Water Large Scale Modelling

2022 ◽  
Author(s):  
K. Marynets
Keyword(s):  
Boundary Value Problem ◽  
Ocean Circulation ◽  
Antarctic Circumpolar Current ◽  
Large Scale ◽  
Global Climate ◽  
Boundary Value ◽  
Global Ocean ◽  
Uniqueness Of Solutions ◽  
Circumpolar Current ◽  
The Antarctic

Abstract. This paper proposes a modelling of the Antarctic Circumpolar Current (ACC) by means of a two-point boundary value problem. As the major means of exchange of water between the great ocean basins (Atlantic, Pacific and Indian), the ACC plays a highly important role in the global climate. Despite its importance, it remains one of the most poorly understood components of global ocean circulation. We present some recent results on the existence and uniqueness of solutions of a two-point nonlinear boundary value problem that arises in the modeling of the flow of the (ACC) (see discussions in [4-9]).

scholarly journals On the Variability of Antarctic Circumpolar Current Fronts Inferred from 1992–2011 Altimetry*

2014 ◽  
Vol 44 (12) ◽  
pp. 3054-3071 ◽  
Author(s):  
Yong Sun Kim ◽  
Alejandro H. Orsi
Keyword(s):  
Ocean Circulation ◽  
Antarctic Circumpolar Current ◽  
Large Scale ◽  
Southern Oscillation ◽  
Climate Signal ◽  
Local Climate ◽  
Basin Scale ◽  
Southeast Pacific ◽  
Circumpolar Current

Abstract Antarctic Circumpolar Current (ACC) fronts, defined as water mass boundaries, have been known to respond to large-scale atmospheric variabilities, especially the Southern Hemisphere annular mode (SAM) and El Niño–Southern Oscillation (ENSO). Distinct patterns of localized variability in meridional front displacements during 1992–2011 are derived from the analysis of satellite sea surface height data. Major basin-scale differences are found between the southeast Pacific (150°–90°W) and the southeast Indian (75°–150°E) sectors of the ACC. Frontal positions in the southeast Pacific show large year-to-year meridional fluctuations, attributed mostly to ENSO and in part SAM, and no apparent seasonal cycles or long-term trends. In contrast, summer (winter) frontal locations in the southeast Indian extend farther to the south (north) of their long-term mean distribution. A southward drift of ACC fronts is indicated over the Indian sector during the past two decades. This long-term shift is not directly related to the atmospheric variabilities, but this is most likely in response to changes in large-scale ocean circulation, in particular to the poleward expansion of the Indian subtropical gyre. The existence of these localized, contrasting variability patterns suggests that a circumpolar-averaging analysis could possibly smooth out a local climate signal, with an emphasis on a basin-scale investigation for climate studies in the Southern Ocean.

Hydrographic changes across the Atlantic Ocean on interannual to decadal time scales – an EN4 profile data analysis

2020 ◽  
Author(s):  
Kristin Burmeister ◽  
Mark Inall ◽  
Clare Johnson
Keyword(s):  
Atlantic Ocean ◽  
Ocean Circulation ◽  
North Atlantic ◽  
Large Scale ◽  
Potential Temperature ◽  
South Atlantic ◽  
Climate Indices ◽  
Equatorial Atlantic ◽  
Profile Data ◽  
Mid Atlantic Ridge

&lt;p&gt;The Atlantic Ocean is influenced by large-scale physical variability like changes in the Subpolar Gyre (SPG), the Atlantic Multidecadal Variability (AMV), the Atlantic Meridional Mode (AMM) or changes in the South Atlantic Anticyclone (SAA). Associated changes in temperature and salinity may severely impact open-ocean and deep-sea ecosystems. We study the variability of potential temperature and salinity profiles associated with large-scale physical variations focusing on 12 marine regions across both the North and South Atlantic Ocean (subpolar Mid-Atlantic Ridge off Iceland; Rockall Trough to Porcupine Abyssal Plain; central Mid-Atlantic Ridge; northwest Atlantic; Sargasso Sea; eastern tropical North Atlantic; central equatorial Atlantic; ecosystems from Angola to the Congo Lobe; the Benguela Current region; ecosystems off Brazil; the Vit&amp;#243;ria-Trindade Seamount Chain off Brazil; Malvinas Upwelling Current off Argentina). These regions were selected within the framework of the EU Horizon 2020 iAtlantic project. They are in proximity to major ocean circulation pathways as well as ocean monitoring arrays and are important for international conservation, Blue Growth and Blue Economy attempts.&lt;/p&gt;&lt;p&gt;Our methodology builds on recent work (Johnson et al., accepted, Frontiers in Marine Science) that shows that climate indices are associated with statistically-significant and spatially-coherent changes in bottom conditions across the northern North Atlantic. We use the same composite approach to investigate the relationship between indices of physical variability and potential temperature and salinity but extend the analysis to include additional indices (e.g. AMM, SAA) and to cover the entire Atlantic basin. Additionally, we use profile data instead of a gridded data product and investigate the full water column by density class, rather than focusing on bottom conditions. This enables physical mechanisms of any observed signals across the Atlantic Ocean as a whole to be explored.&lt;/p&gt;

scholarly journals The Effect of the Kerguelen Plateau on the Ocean Circulation

2016 ◽  
Vol 46 (11) ◽  
pp. 3385-3396 ◽  
Author(s):  
Jinbo Wang ◽  
Matthew R. Mazloff ◽  
Sarah T. Gille
Keyword(s):  
Southern Ocean ◽  
Ocean Circulation ◽  
Antarctic Circumpolar Current ◽  
Large Scale ◽  
Pressure Field ◽  
Global Ocean ◽  
Kerguelen Plateau ◽  
Local Pressure ◽  
Circumpolar Current ◽  
The Antarctic

AbstractThe Kerguelen Plateau is a major topographic feature in the Southern Ocean. Located in the Indian sector and spanning nearly 2000 km in the meridional direction from the polar to the subantarctic region, it deflects the eastward-flowing Antarctic Circumpolar Current and influences the physical circulation and biogeochemistry of the Southern Ocean. The Kerguelen Plateau is known to govern the local dynamics, but its impact on the large-scale ocean circulation has not been explored. By comparing global ocean numerical simulations with and without the Kerguelen Plateau, this study identifies two major Kerguelen Plateau effects: 1) The plateau supports a local pressure field that pushes the Antarctic Circumpolar Current northward. This process reduces the warm-water transport from the Indian to the Atlantic Ocean. 2) The plateau-generated pressure field shields the Weddell Gyre from the influence of the warmer subantarctic and subtropical waters. The first effect influences the strength of the Antarctic Circumpolar Current and the Agulhas leakage, both of which are important elements in the global thermohaline circulation. The second effect results in a zonally asymmetric response of the subpolar gyres to Southern Hemisphere wind forcing.

scholarly journals Late oligocene–early miocene shortening in the Thrace Basin, northern Aegean

2021 ◽  
Author(s):  
Ümitcan Erbil ◽  
Aral I. Okay ◽  
Aynur Hakyemez
Keyword(s):  
Large Scale ◽  
Middle Eocene ◽  
Early Miocene ◽  
Fold Axis ◽  
Late Oligocene ◽  
The Balkans ◽  
Sedimentary Sequences ◽  
The North ◽  
Early Oligocene ◽  
Thrace Basin

AbstractLate Cenozoic was a period of large-scale extension in the Aegean. The extension is mainly recorded in the metamorphic core complexes with little data from the sedimentary sequences. The exception is the Thrace Basin in the northern Aegean, which has a continuous record of Middle Eocene to Oligocene marine sedimentation. In the Thrace Basin, the Late Oligocene–Early Miocene was characterized by north-northwest (N25°W) shortening leading to the termination of sedimentation and formation of large-scale folds. We studied the stratigraphy and structure of one of these folds, the Korudağ anticline. The Korudağ anticline has formed in the uppermost Eocene–Lower Oligocene siliciclastic turbidites with Early Oligocene (31.6 Ma zircon U–Pb age) acidic tuff beds. The turbidites are underlain by a thin sequence of Upper Eocene pelagic limestone. The Korudağ anticline is an east-northeast (N65°E) trending fault-propagation fold, 9 km wide and 22 km long and with a subhorizontal fold axis. It is asymmetric with shallowly-dipping northern and steeply-dipping southern limbs. Its geometry indicates about 1 km of shortening in a N25°W direction. The folded strata are unconformably overlain by Middle Miocene continental sandstones, which constrain the age of folding. The Korudağ anticline and other large folds in the Thrace Basin predate the inception of the North Anatolian Fault (NAF) by at least 12 myr. The Late Oligocene–Early Miocene (28–17 Ma) shortening in the Thrace Basin and elsewhere in the Balkans forms an interlude between two extensional periods, and is probably linked to changes in the subduction dynamics along the Hellenic trench.

A Near-Uniform Basin-Wide Sea Level Fluctuation of the Mediterranean Sea

2007 ◽  
Vol 37 (2) ◽  
pp. 338-358 ◽  
Author(s):  
Ichiro Fukumori ◽  
Dimitris Menemenlis ◽  
Tong Lee
Keyword(s):  
Atlantic Ocean ◽  
Mediterranean Sea ◽  
Sea Level ◽  
Ocean Circulation ◽  
Large Scale ◽  
Circulation Model ◽  
Level Fluctuation ◽  
Strait Of Gibraltar ◽  
Sea Level Fluctuation ◽  
The Mediterranean

Abstract A new basin-wide oscillation of the Mediterranean Sea is identified and analyzed using sea level observations from the Ocean Topography Experiment (TOPEX)/Poseidon satellite altimeter and a numerical ocean circulation model. More than 50% of the large-scale, nontidal, and non-pressure-driven variance of sea level can be attributed to this oscillation, which is nearly uniform in phase and amplitude across the entire basin. The oscillation has periods ranging from 10 days to several years and has a magnitude as large as 10 cm. The model suggests that the fluctuations are driven by winds at the Strait of Gibraltar and its neighboring region, including the Alboran Sea and a part of the Atlantic Ocean immediately to the west of the strait. Winds in this region force a net mass flux through the Strait of Gibraltar to which the Mediterranean Sea adjusts almost uniformly across its entire basin with depth-independent pressure perturbations. The wind-driven response can be explained in part by wind setup; a near-stationary balance is established between the along-strait wind in this forcing region and the sea level difference between the Mediterranean Sea and the Atlantic Ocean. The amplitude of this basin-wide wind-driven sea level fluctuation is inversely proportional to the setup region’s depth but is insensitive to its width including that of Gibraltar Strait. The wind-driven fluctuation is coherent with atmospheric pressure over the basin and contributes to the apparent deviation of the Mediterranean Sea from an inverse barometer response.

scholarly journals How ocean ridges affect large-scale ocean circulation

Eos ◽  
2011 ◽  
Vol 92 (42) ◽  
pp. 372-372
Author(s):  
Colin Schultz
Keyword(s):  
Ocean Circulation ◽  
Large Scale ◽  
Ocean Ridges

scholarly journals A Diagnostic Model of the Nordic Seas and Arctic Ocean Circulation: Quantifying the Effects of a Variable Bottom Density along a Sloping Topography

2008 ◽  
Vol 38 (12) ◽  
pp. 2685-2703 ◽  
Author(s):  
Signe Aaboe ◽  
Ole Anders Nøst
Keyword(s):  
Arctic Ocean ◽  
Ocean Circulation ◽  
Large Scale ◽  
The Arctic ◽  
Diagnostic Model ◽  
Large Scale Circulation ◽  
Nordic Seas ◽  
Variable Bottom ◽  
Canadian Basin ◽  
Baroclinic Transport

Abstract A linear diagnostic model, solving for the time-mean large-scale circulation in the Nordic seas and Arctic Ocean, is presented. Solutions on depth contours that close within the Nordic seas and Arctic Ocean are found from vorticity balances integrated over the areas enclosed by the contours. Climatological data for wind stress and hydrography are used as input to the model, and the bottom geostrophic flow is assumed to follow depth contours. Comparison against velocity observations shows that the simplified dynamics in the model capture many aspects of the large-scale circulation. Special attention is given to the dynamical effects of an along-isobath varying bottom density, which leads to a transformation between barotropic and baroclinic transport. Along the continental slope, enclosing both the Nordic seas and Arctic Ocean, the along-slope barotropic transport has a maximum in the Nordic seas and a minimum in the Canadian Basin with a difference of 9 Sv (1 Sv ≡ 106 m3 s−1) between the two. This is caused by the relatively lower bottom densities in the Canadian Basin compared to the Nordic seas and suggests that most of the barotropic transport entering the Arctic Ocean through the Fram Strait is transformed to baroclinic transport. A conversion from barotropic to baroclinic flow may be highly important for the slope–basin exchange in the Nordic seas and Arctic Ocean. The model has obvious shortcomings due to its simplicity. However, the simplified physics and the agreement with observations make this model an excellent framework for understanding the large-scale circulation in the Nordic seas and Arctic Ocean.

scholarly journals Structure of ocean circulation between the Galápagos Islands and Ecuador

2013 ◽  
Vol 33 ◽  
pp. 3-12 ◽  
Author(s):  
C. Collins ◽  
A. Mascarenhas ◽  
R. Martinez
Keyword(s):  
Sea Level ◽  
Ocean Circulation ◽  
Large Scale ◽  
Southern Oscillation ◽  
Galapagos Islands ◽  
Surface Flow ◽  
Climate Indices ◽  
Late Winter ◽  
Coastal Current ◽  
Galápagos Islands

Abstract. From 27 March to 5 April 2009, upper ocean velocities between the Galápagos Islands and Ecuador were measured using a vessel mounted ADCP. A region of possible strong cross-hemisphere exchange was observed immediately to the east of the Galápagos, where a shallow (200 m) 300 km wide northeastward surface flow transported 7–11 Sv. Underlying this strong northeastward surface current, a southward flowing undercurrent was observed which was at least 600 m thick, 100 km wide, and had an observed transport of 7–8 Sv. Next to the Ecuador coast, the shallow (< 200 m) Ecuador Coastal Current was observed to extend offshore 100 km with strongest flow, 0.33 m s−1, near the surface. Immediately to the west of the Ecuador Coastal Current, flow was directed eastward and southward into the beginnings of the Peru-Chile Countercurrent. The integral of the surface currents between the Galápagos and Ecuador agreed well with observed sea level differences. Although the correlation of the sea level differences with large scale climate indices (Niño3 and the Southern Oscillation Index) was significant, more than half of the sea level variability was not explained. Seasonal variability of the sea level difference indicated that sea level was 2 cm higher at the Galápagos during late winter and early spring, which could be associated with the pattern of northward surface flows observed by R/V Knorr.

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