Volcanic features and the hydrological setting of Southern Thule, South Sandwich Islands

2008 ◽  
Vol 20 (3) ◽  
pp. 301-308 ◽  
Author(s):  
Claire S. Allen ◽  
John L. Smellie
Keyword(s):  
High Resolution ◽  
Warming Trend ◽  
Hydrothermal Activity ◽  
The South ◽  
Scotia Sea ◽  
Ice Caps ◽  
Low Salinity ◽  
Salinity Data ◽  
South Sandwich Islands ◽  
Salinity Water

AbstractThis paper provides new observations of volcanic features and hydrological characteristics in and around Southern Thule, the southernmost group of islands in the South Sandwich Islands, including the first high-resolution bathymetric image of the Douglas Strait caldera. The South Sandwich Islands are the summits of several very large subduction-related volcanoes constructed at the eastern boundary of the Scotia Sea. Observations of the islands are scarce owing to their remote location and they are only rarely visited, yet the area is an active volcanic arc that is rapidly changing as a result of eruptions, including one (on Montagu Island) that has been ongoing for six years and is creating new land. The three islands that make up Southern Thule are morphologically different, and they illustrate different stages in the construction and evolution of islands in the South Sandwich group. We present the results of an acoustic and hydrographic survey that resulted in the first high-resolution, multibeam ‘swath’ image of the submarine Douglas Strait caldera. The results confirm the presence of a large sediment mound (c. 1000 m3 in volume) on the floor of the Douglas Strait caldera related to a flank collapse of Thule Island. The image also shows an extensive arcuate fault structure, interpreted as evidence that the caldera is nested, and its geomorphological freshness suggests that it is a very young feature that formed conceivably in the last few decades or centuries. The bathymetric image also reveals at least three cone- or mound-like structures within the caldera that may relate to renewed post-caldera volcanism (as pyroclastic cones and/or pillow mounds). Recently formed cones and faults associated with caldera rims are often associated with hydrothermal activity. However, temperature and salinity data collected within the caldera do not yet show any evidence of hydrothermal venting. The ocean surrounding Southern Thule has a prominent surface layer of low salinity water that is probably caused by a high meltwater flux derived from ice caps on the islands. This flux may have been enhanced by the recent warming trend observed in the Antarctic Peninsula, although volcano-related geothermal melting in the ice-filled Thule Island caldera may also contribute to the meltwater flux.

scholarly journals ASIRI: An Ocean–Atmosphere Initiative for Bay of Bengal

2016 ◽  
Vol 97 (10) ◽  
pp. 1859-1884 ◽  
Author(s):  
Hemantha W. Wijesekera ◽  
Emily Shroyer ◽  
Amit Tandon ◽  
M. Ravichandran ◽  
Debasis Sengupta ◽  
...  
Keyword(s):  
Boundary Layer ◽  
High Resolution ◽  
Indian Ocean ◽  
Bay Of Bengal ◽  
Regional Scale ◽  
Ocean Dynamics ◽  
Coastal Current ◽  
Northeast Monsoon ◽  
Low Salinity ◽  
Salinity Water

Abstract Air–Sea Interactions in the Northern Indian Ocean (ASIRI) is an international research effort (2013–17) aimed at understanding and quantifying coupled atmosphere–ocean dynamics of the Bay of Bengal (BoB) with relevance to Indian Ocean monsoons. Working collaboratively, more than 20 research institutions are acquiring field observations coupled with operational and high-resolution models to address scientific issues that have stymied the monsoon predictability. ASIRI combines new and mature observational technologies to resolve submesoscale to regional-scale currents and hydrophysical fields. These data reveal BoB’s sharp frontal features, submesoscale variability, low-salinity lenses and filaments, and shallow mixed layers, with relatively weak turbulent mixing. Observed physical features include energetic high-frequency internal waves in the southern BoB, energetic mesoscale and submesoscale features including an intrathermocline eddy in the central BoB, and a high-resolution view of the exchange along the periphery of Sri Lanka, which includes the 100-km-wide East India Coastal Current (EICC) carrying low-salinity water out of the BoB and an adjacent, broad northward flow (∼300 km wide) that carries high-salinity water into BoB during the northeast monsoon. Atmospheric boundary layer (ABL) observations during the decaying phase of the Madden–Julian oscillation (MJO) permit the study of multiscale atmospheric processes associated with non-MJO phenomena and their impacts on the marine boundary layer. Underway analyses that integrate observations and numerical simulations shed light on how air–sea interactions control the ABL and upper-ocean processes.

scholarly journals Subduction of a low-salinity water mass around the Xisha Islands in the South China Sea

2018 ◽  
Vol 8 (1) ◽  
Author(s):  
Zhida Huang ◽  
Wei Zhuang ◽  
Hailong Liu ◽  
Jianyu Hu
Keyword(s):  
South China Sea ◽  
South China ◽  
Water Mass ◽  
The South China Sea ◽  
The South ◽  
Xisha Islands ◽  
China Sea ◽  
Low Salinity ◽  
Low Salinity Water ◽  
Salinity Water

scholarly journals Distribution of Vulnerable Marine Ecosystems at the South Sandwich Islands: Results From the Blue Belt Discovery Expedition 99 Deep-Water Camera Surveys

2021 ◽  
Vol 8 ◽  
Author(s):  
Anna-Leena Downie ◽  
Rui P. Vieira ◽  
Oliver T. Hogg ◽  
Chris Darby
Keyword(s):  
Marine Protected Area ◽  
Benthic Communities ◽  
Marine Ecosystem ◽  
Latitudinal Gradients ◽  
The South ◽  
Indicator Taxa ◽  
Scotia Sea ◽  
Benthic Environment ◽  
South Sandwich Islands ◽  
A Chain

The South Sandwich Islands (SSI) are a chain of volcanic islands located to the east of the Scotia Sea, approximately 700 km south-east of South Georgia. To date, knowledge of the SSI benthic environment remains limited. In this context, the Blue Belt Programme conducted a scientific survey in the SSI Marine Protected Area (MPA) during February/March 2019 to examine the biodiversity and distribution of benthic communities and their potential vulnerability to licensed longline research fisheries. Here we report results from analysis of multibeam echosounder (MBES) data and drop camera imagery data collected in selected locations around the SSI. A total of eight vulnerable marine ecosystem (VME) indicator morphotaxa were mapped along the slopes of the SSI, showing a substantial variation in taxon composition and frequency of occurrence, both along bathymetric and latitudinal gradients. Our results suggest that VME indicator taxa are mostly restricted to waters shallower than 700 m. As such, based on our present understanding of the region’s benthic environment the MPA, as currently established, offers effective protection for the majority of the VME indicator taxa.

The Maximum Ice Extent on Island Groups in the Scotia Sea, Antarctica

1977 ◽  
Vol 7 (2) ◽  
pp. 268-282 ◽  
Author(s):  
D.E. Sugden ◽  
C.M. Clapperton
Keyword(s):  
Ice Cover ◽  
South Shetland Islands ◽  
Falkland Islands ◽  
The South ◽  
Scotia Sea ◽  
Shetland Islands ◽  
South Georgia ◽  
Orkney Islands ◽  
Ice Caps ◽  
The Antarctic

Evidence is presented for a more extensive ice cover over South Georgia, the South Orkney Islands, the South Shetland Islands, and the tip of the Antarctic Peninsula. Ice extended across the adjacent submarine shelves to a depth of 200 m below present sea level. Troughs cut into the submarine shelves by ice streams or outlet glaciers and ice-scoured features on the shelf areas suggest that the ice caps were warm-based. The South Shetland Islands appear not to have been overrun by continental ice. Geomorphological evidence in two island groups suggests that the maximum ice cover, which was responsible for the bulk of glacial erosion, predates at least one full glaciation. Subsequently there was a marine interval and then a glaciation which overran all of the lowlying peninsulas. The Falkland Islands, only 2° of latitude north of South Georgia, were never covered by an ice cap and supported only a few slightly enlarged cirque glaciers. This suggests that the major oceanographic and atmospheric boundary represented by the Antarctic Convergence, which is presently situated between the Falkland Islands and South Georgia, has remained in a similar position throughout the glacial age. Its position is probably bathymetrically controlled.

scholarly journals Analysis of Surface Sound Duct in the Northern Shelf of the South China Sea

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Ke Qu ◽  
Shengchun Piao ◽  
Jianbo Zhou ◽  
Fengqin Zhu
Keyword(s):  
South China Sea ◽  
South China ◽  
The South China Sea ◽  
The South ◽  
Near Surface ◽  
Northern Shelf ◽  
China Sea ◽  
Low Salinity ◽  
Low Salinity Water ◽  
Salinity Water

The northern shelf of the South China Sea (NSSCS) is characterized by surface low-salinity water due to discharge from the Pearl River. In such an environment, the surface sound duct (SSD) is the most important duct for near-surface sonar applications. Nevertheless, the mechanism of SSD formation is very complicated and is influenced by salinity, temperature at the air-sea interface, and various additional marine phenomena. In this study, an 8-year conductivity-temperature-depth (CTD) profile of the NSSCS was used to analyze the SSD formation. An advanced diagrammatic method is proposed to provide a quantitative analysis of the contribution of salinity, temperature, and hydrostatic pressure on SSD formation. Large salinity gradient (0.25 psu/m) was shown to play a crucial role in SSD formation when a mixed layer exists. As representative examples, the sea under cold surges, typhoon genesis, and low-salinity lenses were studied. Conversely, the absence of SSDs in low-salinity water was also observed in upwelling regions. This study further showed that highly negative temperature gradients affect SSD formation even in low-salinity water. Furthermore, although the duct depth of a low-salinity SSD is usually less than 10 meters, it still can serve as an effective duct for acoustic propagation.

scholarly journals High-Resolution (3.5kHz) Echo Characters of the Northern South Shetland Continental Margin and the South Scotia Sea, Antarctica

2003 ◽  
Vol 25 (4) ◽  
pp. 557-567
Author(s):  
Sang-Hoon Lee ◽  
Young-Keun Jin ◽  
Kyu-Jung Kim ◽  
Sang-Heon Nam ◽  
Yea-Dong Kim
Keyword(s):  
High Resolution ◽  
Continental Margin ◽  
The South ◽  
Scotia Sea

MODELING THE SOUTH ATLANTIC OCEAN FROM MEDIUM TO HIGH RESOLUTION

2014 ◽  
Vol 31 (2) ◽  
Author(s):  
Mariela Gabioux ◽  
Vladimir Santos da Costa ◽  
Joao Marcos Azevedo Correia de Souza ◽  
Bruna Faria de Oliveira ◽  
Afonso De Moraes Paiva
Keyword(s):  
High Resolution ◽  
Atlantic Ocean ◽  
Large Scale ◽  
South Atlantic ◽  
Surface Relaxation ◽  
The South ◽  
Small Surface ◽  
Basic Model ◽  
Basic Set ◽  
Set Up

Results of the basic model configuration of the REMO project, a Brazilian approach towards operational oceanography, are discussed. This configuration consists basically of a high-resolution eddy-resolving, 1/12 degree model for the Metarea V, nested in a medium-resolution eddy-permitting, 1/4 degree model of the Atlantic Ocean. These simulations performed with HYCOM model, aim for: a) creating a basic set-up for implementation of assimilation techniques leading to ocean prediction; b) the development of hydrodynamics bases for environmental studies; c) providing boundary conditions for regional domains with increased resolution. The 1/4 degree simulation was able to simulate realistic equatorial and south Atlantic large scale circulation, both the wind-driven and the thermohaline components. The high resolution simulation was able to generate mesoscale and represent well the variability pattern within the Metarea V domain. The BC mean transport values were well represented in the southwestern region (between Vitória-Trinidade sea mount and 29S), in contrast to higher latitudes (higher than 30S) where it was slightly underestimated. Important issues for the simulation of the South Atlantic with high resolution are discussed, like the ideal place for boundaries, improvements in the bathymetric representation and the control of bias SST, by the introducing of a small surface relaxation. In order to make a preliminary assessment of the model behavior when submitted to data assimilation, the Cooper & Haines (1996) method was used to extrapolate SSH anomalies fields to deeper layers every 7 days, with encouraging results.

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