scholarly journals Tracing Southwest Pacific Bottom Water Using Potential Vorticity and Helium-3

2012 ◽  
Vol 42 (12) ◽  
pp. 2153-2168 ◽  
Author(s):  
Stephanie M. Downes ◽  
Robert M. Key ◽  
Alejandro H. Orsi ◽  
Kevin G. Speer ◽  
James H. Swift
Keyword(s):  
Potential Vorticity ◽  
Hydrothermal Vents ◽  
Bottom Water ◽  
Drake Passage ◽  
South Pacific ◽  
The South ◽  
Southwest Pacific ◽  
The Pacific ◽  
Circumpolar Current ◽  
The Antarctic

Abstract This study uses potential vorticity and other tracers to identify the pathways of the densest form of Circumpolar Deep Water in the South Pacific, termed “Southwest Pacific Bottom Water” (SPBW), along the 28.2 kg m−3 surface. This study focuses on the potential vorticity signals associated with three major dynamical processes occurring in the vicinity of the Pacific–Antarctic Ridge: 1) the strong flow of the Antarctic Circumpolar Current (ACC), 2) lateral eddy stirring, and 3) heat and stratification changes in bottom waters induced by hydrothermal vents. These processes result in southward and downstream advection of low potential vorticity along rising isopycnal surfaces. Using δ3He released from the hydrothermal vents, the influence of volcanic activity on the SPBW may be traced across the South Pacific along the path of the ACC to Drake Passage. SPBW also flows within the southern limb of the Ross Gyre, reaching the Antarctic Slope in places and contributes via entrainment to the formation of Antarctic Bottom Water. Finally, it is shown that the magnitude and location of the potential vorticity signals associated with SPBW have endured over at least the last two decades, and that they are unique to the South Pacific sector.

scholarly journals Coupling Influences of ENSO and PDO on the Inter-Decadal SST Variability of the ACC around the Western South Atlantic

2019 ◽  
Vol 11 (18) ◽  
pp. 4853
Author(s):  
You-Lin Wang ◽  
Yu-Chen Hsu ◽  
Chung-Pan Lee ◽  
Chau-Ron Wu
Keyword(s):  
Antarctic Circumpolar Current ◽  
Water Mass ◽  
Southern Oscillation ◽  
Drake Passage ◽  
South Atlantic ◽  
Sst Variability ◽  
The Pacific ◽  
Circumpolar Current ◽  
The Antarctic

The Antarctic Circumpolar Current (ACC) plays an important role in the climate as it balances heat energy and water mass between the Pacific and Atlantic Oceans through the Drake Passage. However, because the historical measurements and observations are extremely limited, the decadal and long-term variations of the ACC around the western South Atlantic Ocean are rarely studied. By analyzing reconstructed sea surface temperatures (SSTs) in a 147-year period (1870–2016), previous studies have shown that SST anomalies (SSTAs) around the Antarctic Peninsula and South America had the same phase change as the El Niño Southern Oscillation (ENSO). This study further showed that changes in SSTAs in the regions mentioned above were enlarged when the Pacific Decadal Oscillation (PDO) and the ENSO were in the same warm or cold phase, implying that changes in the SST of higher latitude oceans could be enhanced when the influence of the ENSO is considered along with the PDO.

Preliminary biostratigraphy of IODP Expedition 383 sites

2021 ◽  
Author(s):  
Mariem Saavedra-Pellitero ◽  
Anieke Brombacher ◽  
Oliver Esper ◽  
Alexandre de Souza ◽  
Elisa Malinverno ◽  
...  
Keyword(s):  
High Resolution ◽  
Water Mass ◽  
Global Climate ◽  
Drake Passage ◽  
Meridional Overturning Circulation ◽  
The Pacific ◽  
Meridional Overturning ◽  
Circumpolar Current ◽  
Oceanic Carbon ◽  
The Antarctic

<p>The Antarctic Circumpolar Current (ACC) is a major driver of global climate. It connects all three ocean basins, integrating global climate variability, and its vertical water mass structure plays a key role in oceanic carbon storage. The Atlantic and Indian sectors of the ACC are well studied, but the Pacific sector lacks deep-sea drilling records. Therefore, past water mass transport through the Drake Passage and its effect on Atlantic Meridional Overturning Circulation are not well understood. To fill this gap, IODP Expedition 383 recovered sediments from three sites in the central South Pacific and three sites from the southern Chilean Margin.</p><p>Here we present the preliminary biostratigraphy developed during the expedition. The sediments contained abundant nannofossils, foraminifera, radiolarians, diatoms and silicoflagellates which produced age models that were in excellent agreement with the shipboard magnetostratigraphy. Two sites contain high-resolution Pleistocene records, one site goes back to the Pliocene, and two others reach back to the late Miocene. Post-cruise research will further refine these age models through high-resolution bio-, magneto- and oxygen isotope stratigraphies that are currently being generated.</p>

Investigating the Dynamics of the Pacific Antarctic Circumpolar Current – Initial Results from International Ocean Discovery Program Expedition 383 (DYNAPACC)

2020 ◽  
Author(s):  
Frank Lamy ◽  
Gisela Winckler ◽  
Carlos Zarikian ◽  
Expedition 383 Scientists
Keyword(s):  
Antarctic Circumpolar Current ◽  
Global Climate ◽  
South Pacific ◽  
Global Ocean ◽  
Sedimentary Sequences ◽  
The Pacific ◽  
Circumpolar Current ◽  
The Antarctic ◽  
Central South ◽  
Chilean Margin

<p>The Antarctic Circumpolar Current (ACC) is the world’s strongest zonal current system that connects all three major basins of the global ocean, and therefore integrates, forces and responds to global climate variability. In contrast to the Atlantic and Indian sectors of the ACC, and with the exception of drill cores from the Antarctic continental margin and off New Zealand, the Pacific sector of the ACC lacks information on its Cenozoic paleoceanography from deep-sea drilling records.</p><p>To advance our knowledge and understanding of Miocene to Holocene atmosphere-ocean-cryosphere dynamics in the Pacific and their implications for regional and global climate and atmospheric CO<sub>2</sub>, IODP Expedition 383 recovered sedimentary sequences at: (1) Three sites located in the central South Pacific (Sites U1539, U1540 and U1541); (2) two sites at the Chilean Margin (U1542, U1544); and (3) one site from the hemipelagic eastern South Pacific (U1543) close to the entrance to the Drake Passage. Age control based on magneto and bio-stratigraphically constrained orbital tuning of physical properties in the Plio-Pleistocene sediments is remarkable, with Sites U1541 and U1543 extending the record back to the late Miocene, and Site U1540 to the earliest Pliocene. Pleistocene sedimentary sequences with high sedimentation rates in the order of 40 cm/kyr were drilled in the Central South Pacific (U1539) and along the Chilean Margin. Taken together, the sites represent a depth transect from ~1100 m at the Chilean margin (U1542) to ~4070 m in the Central South Pacific (U1539), and allow reconstructing changes in the vertical structure of the ACC – a key issue for understanding the role of the Southern Ocean in the global carbon cycle- to be investigated. The sites are located at latitudes and water depths where sediments will allow the application of a wide range of siliciclastic, carbonate, and opal-based proxies to address our objectives of reconstructing, with unprecedented stratigraphic detail, surface to deep ocean variations and their relation to atmosphere and cryosphere changes through stadial-to-interstadial, glacial-to-interglacial and warmer than present time intervals.</p>

scholarly journals Massive Southern Ocean phytoplankton bloom fed by iron of possible hydrothermal origin

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Casey M. S. Schine ◽  
Anne-Carlijn Alderkamp ◽  
Gert van Dijken ◽  
Loes J. A. Gerringa ◽  
Sara Sergi ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Primary Production ◽  
Hydrothermal Vent ◽  
Hydrothermal Vents ◽  
Phytoplankton Bloom ◽  
Hydrothermal Origin ◽  
The Pacific ◽  
High Nutrient ◽  
Circumpolar Current ◽  
The Antarctic

AbstractPrimary production in the Southern Ocean (SO) is limited by iron availability. Hydrothermal vents have been identified as a potentially important source of iron to SO surface waters. Here we identify a recurring phytoplankton bloom in the high-nutrient, low-chlorophyll waters of the Antarctic Circumpolar Current in the Pacific sector of the SO, that we argue is fed by iron of hydrothermal origin. In January 2014 the bloom covered an area of ~266,000 km2 with depth-integrated chlorophyll a > 300 mg m−2, primary production rates >1 g C m−2 d−1, and a mean CO2 flux of −0.38 g C m−2 d−1. The elevated iron supporting this bloom is likely of hydrothermal origin based on the recurrent position of the bloom relative to two active hydrothermal vent fields along the Australian Antarctic Ridge and the association of the elevated iron with a distinct water mass characteristic of a nonbuoyant hydrothermal vent plume.

Late Oligocene initiation of the Antarctic Circumpolar Current: Evidence from the South Pacific

Geology ◽  
2007 ◽  
Vol 35 (8) ◽  
pp. 691 ◽  
Author(s):  
Mitchell Lyle ◽  
Samantha Gibbs ◽  
Theodore C. Moore ◽  
David K. Rea
Keyword(s):  
Antarctic Circumpolar Current ◽  
South Pacific ◽  
Current Evidence ◽  
Late Oligocene ◽  
The South ◽  
Circumpolar Current ◽  
The Antarctic

scholarly journals Estimating a Submesoscale Diffusivity Using a Roughness Measure Applied to a Tracer Release Experiment in the Southern Ocean

2015 ◽  
Vol 45 (6) ◽  
pp. 1610-1631 ◽  
Author(s):  
Emma J. D. Boland ◽  
Emily Shuckburgh ◽  
Peter H. Haynes ◽  
James R. Ledwell ◽  
Marie-José Messias ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Antarctic Circumpolar Current ◽  
Drake Passage ◽  
Velocity Fields ◽  
Small Scale ◽  
The Pacific ◽  
Circumpolar Current ◽  
The Antarctic ◽  
Mesoscale Processes ◽  
Submesoscale Processes

AbstractThe use of a measure to diagnose submesoscale isopycnal diffusivity by determining the best match between observations of a tracer and simulations with varying small-scale diffusivities is tested. Specifically, the robustness of a “roughness” measure to discriminate between tracer fields experiencing different submesoscale isopycnal diffusivities and advected by scaled altimetric velocity fields is investigated. This measure is used to compare numerical simulations of the tracer released at a depth of about 1.5 km in the Pacific sector of the Southern Ocean during the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES) field campaign with observations of the tracer taken on DIMES cruises. The authors find that simulations with an isopycnal diffusivity of ~20 m2 s−1 best match observations in the Pacific sector of the Antarctic Circumpolar Current (ACC), rising to ~20–50 m2 s−1 through Drake Passage, representing submesoscale processes and any mesoscale processes unresolved by the advecting altimetry fields. The roughness measure is demonstrated to be a statistically robust way to estimate a small-scale diffusivity when measurements are relatively sparse in space and time, although it does not work if there are too few measurements overall. The planning of tracer measurements during a cruise in order to maximize the robustness of the roughness measure is also considered. It is found that the robustness is increased if the spatial resolution of tracer measurements is increased with the time since tracer release.

scholarly journals An Exchange Window for the Injection of Antarctic Intermediate Water into the South Pacific

2007 ◽  
Vol 37 (1) ◽  
pp. 31-49 ◽  
Author(s):  
Daniele Iudicone ◽  
Keith B. Rodgers ◽  
Richard Schopp ◽  
Gurvan Madec
Keyword(s):  
Southern Ocean ◽  
Large Scale ◽  
South Pacific ◽  
Intermediate Water ◽  
The South ◽  
Antarctic Intermediate Water ◽  
South Pacific Ocean ◽  
The Pacific ◽  
Basin Scale ◽  
Circumpolar Current

Abstract Antarctic Intermediate Water (AAIW) occupies the intermediate horizon of most of the world oceans. Formed in the Southern Ocean, it is characterized by a relative salinity minimum. With a new, denser in situ National Oceanographic Data Center dataset, the authors have reanalyzed the export characteristics of AAIW from the Southern Ocean into the South Pacific Ocean. These new data show that part of the AAIW is exported from the subpolar frontal region by the large-scale circulation through an exchange window of 10° width situated east of 90°W in the southeast corner of the Pacific basin. This suggests the origin of this water to be in the Antarctic Circumpolar Current. A set of numerical modeling experiments has been used to reproduce these observed features and to demonstrate that the dynamics of the exchange window is controlled by the basin-scale meridional pressure gradient. The exchange of AAIW between the Southern and Pacific Oceans must therefore be understood in the context of the large basin-scale dynamical balance rather than simply local effects.

New World Origins of Southwest Pacific Gesneriaceae: Multiple Movements Across and Within the South Pacific

2011 ◽  
Vol 172 (3) ◽  
pp. 434-457 ◽  
Author(s):  
Vincent L. Woo ◽  
Minde M. Funke ◽  
James F. Smith ◽  
Peter J. Lockhart ◽  
Philip J. Garnock-Jones
Keyword(s):  
New World ◽  
South Pacific ◽  
The South ◽  
Southwest Pacific

Transcending the colonial gaze: Empathy, agency and community in the South Pacific photography of John Watt Beattie1

2020 ◽  
Vol 8 (2) ◽  
pp. 151-170 ◽  
Author(s):  
Terry M. Brown
Keyword(s):  
Solomon Islands ◽  
South Pacific ◽  
British Colonialism ◽  
The South ◽  
The Pacific ◽  
Norfolk Island ◽  
The Church

For three months in 1906, John Watt Beattie, the noted Australian photographer – at the invitation of the Anglican Bishop of Melanesia, Cecil Wilson – travelling on the church vessel the Southern Cross, photographed people and sites associated with the Melanesian Mission on Norfolk Island and present-day Vanuatu and Solomon Islands. Beattie reproduced many of the 1500-plus photographs from that trip, which he sold in various formats from his photographic studio in Hobart, Tasmania. The photographs constitute a priceless collection of Pacific images that began to be used very quickly in a variety of publications, with or without attribution. I shall examine some of these photographs in the context of the ethos of the Melanesian Mission, British colonialism in the Solomon Islands, and Beattie’s previous photographic experience. I shall argue that Beattie first exhibited a colonial gaze of objectifying his dehumanized exotic subjects (e.g. as ‘savages’ and ‘cannibals’) but with increased familiarity with them, became empathetic and admiring. In this change of attitude, I argue that he effectively transcended his colonial gaze to produce photographs of great empathy, beauty and longevity. At the same time, he became more critical of the colonial enterprise in the Pacific, whether government, commercial or church.

scholarly journals Intrinsic variability of the Antarctic Circumpolar Current system: low- and high-frequency fluctuations of the Argentine Basin flow

Ocean Science ◽  
2014 ◽  
Vol 10 (2) ◽  
pp. 201-213 ◽  
Author(s):  
G. Sgubin ◽  
S. Pierini ◽  
H. A. Dijkstra
Keyword(s):  
High Frequency ◽  
Antarctic Circumpolar Current ◽  
Current System ◽  
Low Frequency ◽  
Drake Passage ◽  
Ocean Model ◽  
Intrinsic Variability ◽  
Circumpolar Current ◽  
The Antarctic ◽  
Argentine Basin

Abstract. In this paper, the variability of the Antarctic Circumpolar Current system produced by purely intrinsic nonlinear oceanic mechanisms is studied through a sigma-coordinate ocean model, implemented in a large portion of the Southern Ocean at an eddy-permitting resolution under steady surface heat and momentum fluxes. The mean transport through the Drake Passage and the structure of the main Antarctic Circumpolar Current fronts are well reproduced by the model. Intrinsic variability is found to be particularly intense in the Subantarctic Front and in the Argentine Basin, on which further analysis is focused. The low-frequency variability at interannual timescales is related to bimodal behavior of the Zapiola Anticyclone, with transitions between a strong and collapsed anticyclonic circulation in substantial agreement with altimeter observations. Variability on smaller timescales shows clear evidence of topographic Rossby-wave propagation along the eastern and southern flanks of the Zapiola Rise and of mesoscale eddies, also in agreement with altimeter observations. The analysis of the relationship between the low- and high-frequency variability suggests possible mechanisms of mutual interaction.

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