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You searched for subject:(Solander). Showing records 1 – 2 of 2 total matches.

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University of Otago

1. Smith, Robert Owain. Variability of the Subtropical Front in the Tasman Sea .

Degree: University of Otago

The subtropical front (STF) is a fundamental feature of the Southern Ocean. It separates waters in the subtropical gyres from Subantarctic waters. At present however only a rudimentary understanding exists about its temporal variability. Variations in the physical state of the STF (i.e. its location, intensity and hydrography) have implications for atmospheric circulation, marine productivity and climate. This thesis focuses on improving temporal understanding of this major Southern Ocean front. Observations of the temporal variability of the STF in the Tasman Sea are presented. These are obtained through a synthesis of repeat hydrographic sections and remotely sensed sea surface temperature (SST) and sea surface salinity (SSS) data. This work aims to contribute to an improved understanding of how the physical state of the STF varies in time, and of role that topography and surface winds play in this variability. Using three hydrographic surveys and remotely sensed SST data collected during the austral autumns of 2007, 2008 and 2011, the interaction of the south subtropical front (S-STF) with topography around southern New Zealand is investigated. The poleward limit of the S-STF is found to be remarkably consistent, crossing the Macquarie Ridge north of a seamount at 49.6°S, before turning equatorward east of 166°E to follow the upper continental shelf. This is contrary to some previous descriptions that placed the S-STF lying across the Snares Shelf close to 47.5°S. Cross-frontal temperature and salinity gradients at the S-STF are also found to be intensified in regions of shallow bathymetry. Both results are attributed to topographic steering of the S-STF by bathymetry at approximately 500 m depth. Thermal fronts detected using thirty years (1982-2011) of remotely sensed SST data are combined with 27 months (2013-2015) of remotely sensed SSS data, to provide new insights on the typical position and seasonal migration of the S-STF in the Tasman Sea. By examining thirty year annual-mean and seasonal-mean distributions of hundreds of thermal fronts that are identified as likely to be surface expressions of the S-STF, a long-term, statistical view of the S-STF’s position in the western and eastern Tasman Sea is developed. It is apparent that seasonal migrations of the S-STF in these locations do not exceed 1°, contrary to a recent suggestion that the subtropical frontal zone undergoes a global, seasonal shift of 5-7°. The distributions of thermal fronts also contain an intriguing suggestion that the S-STF might behave bimodally at the Macquarie Ridge. SSTs across the S-STF south of New Zealand exhibit marked interannual variability. SST variability in this region may have significant impacts on regional climate. Recent studies have shown that variability in the basin-wide wind stress curl significantly influence SSTs in other parts of the South Pacific subtropical gyre. Using thirty years of remotely sensed SST and atmospheric reanalysis data, variability of subtropical and Subantarctic SSTs at the S-STF south of… Advisors/Committee Members: Vennell, Ross (advisor).

Subjects/Keywords: Subtropical Front; New Zealand; Tasman Sea; Southern Ocean; Macquarie Ridge; Solander Trough; Snares Depression; oceanic front; frontal zone; S-STF; N-STF

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APA (6th Edition):

Smith, R. O. (n.d.). Variability of the Subtropical Front in the Tasman Sea . (Doctoral Dissertation). University of Otago. Retrieved from http://hdl.handle.net/10523/7780

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Chicago Manual of Style (16th Edition):

Smith, Robert Owain. “Variability of the Subtropical Front in the Tasman Sea .” Doctoral Dissertation, University of Otago. Accessed October 18, 2019. http://hdl.handle.net/10523/7780.

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MLA Handbook (7th Edition):

Smith, Robert Owain. “Variability of the Subtropical Front in the Tasman Sea .” Web. 18 Oct 2019.

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No year of publication.

Vancouver:

Smith RO. Variability of the Subtropical Front in the Tasman Sea . [Internet] [Doctoral dissertation]. University of Otago; [cited 2019 Oct 18]. Available from: http://hdl.handle.net/10523/7780.

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Council of Science Editors:

Smith RO. Variability of the Subtropical Front in the Tasman Sea . [Doctoral Dissertation]. University of Otago; Available from: http://hdl.handle.net/10523/7780

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No year of publication.


University of Otago

2. Lennon, Tim. Linking Shallow and Deep Features on the Shelf East and West of Stewart Island .

Degree: University of Otago

The sedimentary basins that have developed to the east and west of Stewart Island are linked through similar tectonic and depositional processes during their formation. The sediment supply and tectonic rifting phases are common to both basins, while sedimentation rates and tectonic subsidence define their unique characteristics. To the east, the Great South Basin is the Campbell Plateau's largest sedimentary basin; it has accumulated up to 8.6 km of sediment since it was formed during mid-Cretaceous rifting related to the separation of New Zealand from western Antarctica. West of Stewart Island lies the Solander Basin, which formed during the Cretaceous - late Eocene extensional regime that led to the opening of the Tasman Sea. Hydrocarbon exploration using seismic and well data has suggested that some of the rift basins formed by the spreading of the Tasman Sea and the break-up of Gondwana have become significant petroleum basin depocentres. In this thesis, high-resolution seismic data have been used in conjunction with existing data to further investigate the geological history and hydrocarbon potential of these basins. Several specific features are addressed as outlined below. On the southeastern side of Stewart Island, a detachment fault associated with late Cretaceous rifting from Gondwana has previously been proposed for the region. Information on the offshore geometry and extent of this, the Sisters Shear Zone, is limited - particularly with regard to its morphology and geological history. Recent work has allowed the dating of rifting episodes across the zone, but its general form is still mostly unknown. This study investigates the shear zone using high-resolution seismic imaging to reconstruct seafloor morphology and shallow fault geometry. High frequency, sub-bottom images were acquired aboard the University of Otago's R/V Polaris II, while seismic processing and interpretation techniques have been employed to investigate the shallow geometry and location of the offshore segment of this proposed detachment fault. On the west side of Stewart Island, a 240-km-long line of multi-channel seismic reflection data, recorded aboard R/V Maurice Ewing in 1996, has imaged several complex structural features along the shelf adjacent to the Solander Basin. Reprocessing of these data and further high-resolution imaging focuses on faulting that appears to outcrop on the seafloor, as well as inferred erosional features on the shelf margin. The collection of high-frequency boomer data in January 2009 has improved the resolution and interpretability of these features. Direct comparison of single-channel boomer data and multi-channel reflection data has revealed several near surface features which are below the Rayleigh resolution limit of the older low-frequency data, including a Bottom Simulating Reflection and turbidity/contour current erosional features. Advisors/Committee Members: Gorman, Andrew R (advisor).

Subjects/Keywords: Geophysics; Stewart Island; New Zealand; Solander Basin; Great South Basin; Oil; Gas; Hydrate; Gas Hydrate; shelf margin; Boomer; Seismic; seismic stratigraphy; sequence stratigraphy

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Lennon, T. (n.d.). Linking Shallow and Deep Features on the Shelf East and West of Stewart Island . (Masters Thesis). University of Otago. Retrieved from http://hdl.handle.net/10523/5058

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Chicago Manual of Style (16th Edition):

Lennon, Tim. “Linking Shallow and Deep Features on the Shelf East and West of Stewart Island .” Masters Thesis, University of Otago. Accessed October 18, 2019. http://hdl.handle.net/10523/5058.

Note: this citation may be lacking information needed for this citation format:
No year of publication.

MLA Handbook (7th Edition):

Lennon, Tim. “Linking Shallow and Deep Features on the Shelf East and West of Stewart Island .” Web. 18 Oct 2019.

Note: this citation may be lacking information needed for this citation format:
No year of publication.

Vancouver:

Lennon T. Linking Shallow and Deep Features on the Shelf East and West of Stewart Island . [Internet] [Masters thesis]. University of Otago; [cited 2019 Oct 18]. Available from: http://hdl.handle.net/10523/5058.

Note: this citation may be lacking information needed for this citation format:
No year of publication.

Council of Science Editors:

Lennon T. Linking Shallow and Deep Features on the Shelf East and West of Stewart Island . [Masters Thesis]. University of Otago; Available from: http://hdl.handle.net/10523/5058

Note: this citation may be lacking information needed for this citation format:
No year of publication.

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