scholarly journals The Passage of the Bomb Radiocarbon Pulse into the Pacific Ocean

Radiocarbon ◽  
2010 ◽  
Vol 52 (3) ◽  
pp. 1182-1190 ◽  
Author(s):  
William J Jenkins ◽  
Kathryn L Elder ◽  
Ann P McNichol ◽  
Karl von Reden
Keyword(s):  
Water Mass ◽  
Source Region ◽  
South Pacific ◽  
Intermediate Water ◽  
Positive Anomaly ◽  
Low Salinity ◽  
Difference Field ◽  
The Pacific ◽  
The Pacific Ocean ◽  
The Antarctic

We report and compare radiocarbon observations made on 2 meridional oceanographic sections along 150°W in the South Pacific in 1991 and 2005. The distributions reflect the progressive penetration of nuclear weapons-produced 14C into the oceanic thermocline. The changes over the 14 yr between occupations are demonstrably large relative to any possible drift in our analytical standardization. The computed difference field based on the gridded data in the upper 1600 m of the section exhibits a significant decrease over time (approaching 40 to 50‰ in Δ14C) in the upper 200–300 m, consistent with the decadal post-bomb decline in atmospheric 14C levels. A strong positive anomaly (increase with time), centered on the low salinity core of the Antarctic Intermediate Water (AAIW), approaches 50–60‰ in Δ14C, a clear signature of the downstream evolution of the 14C transient in this water mass. We use this observation to estimate the transit time of AAIW from its “source region” in the southeast South Pacific and to compute the effective reservoir age of this water mass. The 2 sections show small but significant changes in the abyssal 14C distributions. Between 1991 and 2005, Δ14C has increased by 9‰ below 2000 m north of 55°S. This change is accompanied overall by a modest increase in salinity and dissolved oxygen, as well as a slight decrease in dissolved silica. Such changes are indicative of greater ventilation. Calculation of “phosphate star” also indicates that this may be due to a shift from the Southern Ocean toward North Atlantic Deep Water as the ventilation source of the abyssal South Pacific.

Water Mixing and Circulation within the South Atlantic Basin Constrained by Seismic Reflection Images

2020 ◽  
Author(s):  
Jingxuan Wei ◽  
Robert Reece ◽  
Will Fortin ◽  
Tanner Acquisto
Keyword(s):  
Seismic Reflection ◽  
Water Mass ◽  
South Atlantic ◽  
Intermediate Water ◽  
The South ◽  
Antarctic Intermediate Water ◽  
Low Salinity ◽  
Mid Atlantic Ridge ◽  
The Antarctic ◽  
Seismic Images

<p>South Atlantic water masses and circulation significantly influence the dynamics and water mass structure of the Atlantic Meridional Overturning Circulation (AMOC). Previous research in the South Atlantic has mostly focused on energetic regions such as the Brazil/Malvinas Confluence Zone along the western boundary and the Agulhas retroflection to the east. However, it is also important to understand water circulation and diapycnal mixing within the South Atlantic Basin (SAB). Previous studies have observed low salinity patches of the Antarctic Intermediate Water within the western side of the SAB at 30<sup>o</sup> S, but the temporal variability of the scales, locations and structures of these low salinity patches are still uncertain. Former studies also show an increased level of mixing within the SAB above the Mid-Atlantic Ridge, but did not evaluate mixing on smaller scales such as mesoscale and sub-mesoscale.</p><p>Here we present a water mass structure analysis at 30<sup>o</sup> S from Rio Grande Rise to the Mid-Atlantic Ridge by using Seismic Oceanography (SO). SO is being applied around the world to image mesoscale water mass structures using the seismic reflection method. Reflections in the seismic images are essentially temperature gradients that are proxies for isopycnal surfaces. We paid particular attention in seismic processing to imaging of structures that characterize the boundary between water masses. We imaged the upper South Atlantic Central Water, and identified discontinuous water boundaries (about 150 km long) between the Antarctic Intermediate Water and the North Atlantic Deep Water that could correspond to the intermittent appearance of low salinity patches. We combine seismic images with previous hydrographic measurements to investigate the temporal change of these low salinity patches. We use a horizontal slope spectra to quantify mixing rate from tracked seismic horizons to evaluate mesoscale and sub-mesoscale mixing events such as internal waves and eddies. Through SO, we hope to better constrain South Atlantic circulation and contribute to the understanding of AMOC as a whole.</p>

scholarly journals Antarctic ice-shelf calving triggered by the Honshu (Japan) earthquake and tsunami, March 2011

2011 ◽  
Vol 57 (205) ◽  
pp. 785-788 ◽  
Author(s):  
Kelly M. Brunt ◽  
Emile A. Okal ◽  
Douglas R. MacAyeal
Keyword(s):  
Pacific Ocean ◽  
Northern Hemisphere ◽  
European Space Agency ◽  
Observational Evidence ◽  
Ice Shelf ◽  
Wave Impact ◽  
Space Agency ◽  
The Pacific ◽  
The Pacific Ocean ◽  
The Antarctic

AbstractWe use European Space Agency Envisat data to present the first observational evidence that a Northern Hemisphere tsunami triggered Antarctic ice-shelf calving more than 13 000 km away. The Honshu tsunami of 11 March 2011 traversed the Pacific Ocean in <18 hours where it impinged on the Sulzberger Ice Shelf, resulting in the calving of 125 km2 of ice from a shelf front that had previously been stable for >46 years. This event further illustrates the growing evidence of ocean-wave impact on Antarctic calving and emphasizes the teleconnection between the Antarctic ice sheet and events as far away as the Northern Hemisphere.

Sailing into the Anthropocene

2016 ◽  
Author(s):  
Peter Dauvergne
Keyword(s):  
South Pacific ◽  
The Political ◽  
Pacific Island ◽  
The South ◽  
Large Numbers ◽  
The Pacific ◽  
History Of ◽  
The Pacific Ocean ◽  
Starting Date ◽  
History Of The South

Chapters 2–6 survey the political and socioeconomic forces underlying the global sustainability crisis. Understanding the scale and depth of contemporary forces of capitalism and consumerism requires a close look at the consequences of imperialism and colonialism on patterns of violence and exploitation. This chapter begins this process of understanding by sketching the history of ecological imperialism after 1600, seeing this as a reasonable starting date for the beginning of what many scholars are now calling the Anthropocene Epoch (or the age of humans, replacing the geologic epoch of the Holocene beginning 12,000 years ago). It opens with Captain Pedro Fernandes de Queirós’s voyage across the Pacific Ocean in 1605–06 to “discover” modern-day Vanuatu, before turning to look more globally at the devastation of imperialism – and later colonialism – for the South Pacific, the Americas, Africa, and Asia. Over this time conquerors enslaved and murdered large numbers of indigenous people; cataclysmic change came as well, however, from the introduction of European diseases, plants, and animals. This chapter’s survey of imperialism, colonialism, and globalization sets the stage for Chapter 3, which explores the devastating history of the South Pacific island of Nauru after 1798.

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.

scholarly journals Oceanic Radiocarbon Between Antarctica and South Africa Along Woce Section 16 at 30°E

Radiocarbon ◽  
1999 ◽  
Vol 41 (1) ◽  
pp. 51-73 ◽  
Author(s):  
Viviane Leboucher ◽  
James Orr ◽  
Philippe Jean-Baptiste ◽  
Maurice Arnold ◽  
Patrick Monfray ◽  
...  
Keyword(s):  
South Africa ◽  
Surface Waters ◽  
Polar Front ◽  
Return Flow ◽  
Intermediate Water ◽  
Data Set ◽  
Deep Waters ◽  
The Pacific ◽  
Ocean Carbon ◽  
The Antarctic

Accelerator mass spectrometry (AMS) radiocarbon measurements were made on 120 samples collected between Antarctica and South Africa along 30°E during the WOCE-France CIVA1 campaign in February 1993. Our principal objective was to complement the Southern Ocean's sparse existing data set in order to improve the 14C benchmark used for validating ocean carbon-cycle models, which disagree considerably in this region. Measured 14C is consistent with the θ-S characteristics of CIVA1. Antarctic Intermediate Water (AAIW) forming north of the Polar Front (PF) is rich in 14C, whereas surface waters south of the PF are depleted in 14C. A distinct old 14C signal was found for the contribution of the Pacific Deep Water (PDW) to the return flow of Circumpolar Deep Waters (CDW). Comparison to previous measurements shows a 14C decrease in surface waters, consistent with northward displacement of surface waters, replacement by old deep waters upwelled at the Antarctic Divergence, and atmospheric decline in 14C. Conversely, an increase was found in deeper layers, in the AAIW. Large uncertainties, associated with previous methods for separating natural and bomb 14C when in the Southern Ocean south of 45°S, motivated us to develop a new approach that relies on a simple mixing model and on chlorofluorocarbon (CFC) measurements also taken during CIVA1. This approach leads to inventories for CIVA1 that are equal to or higher than those calculated with previous methods. Differences between old and new methods are especially high south of approximately 55°S, where bomb 14C inventories are relatively modest.

IODP Expedition 378 South Pacific Paleogene Climate: New high-resolution high-latitude Cenozoic Section

2020 ◽  
Author(s):  
Ursula Röhl ◽  
Deborah J Thomas ◽  
Laurel Childress ◽  
Keyword(s):  
Pacific Ocean ◽  
High Latitude ◽  
Global Climate ◽  
South Pacific ◽  
The South ◽  
Red Clay ◽  
South Pacific Ocean ◽  
The Pacific ◽  
The Pacific Ocean ◽  
International Ocean Discovery Program

&lt;p&gt;As the world&amp;#8217;s largest ocean, the Pacific Ocean is intricately linked to major changes in the global climate system. International Ocean Discovery Program (IODP) Expedition 378 is designed to recover Paleogene sedimentary sections in the South Pacific to reconstruct key changes in oceanic and atmospheric circulation. These cores will provide an unparalleled opportunity to add crucial new data and geographic coverage to existing reconstructions of Paleogene climate and as part of a major regional slate of expeditions in the Southern Ocean to fill a critical need for high-latitude climate reconstructions. Appropriate high-latitude records are unobtainable in the Northern Hemisphere of the Pacific Ocean.&lt;/p&gt;&lt;p&gt;The drilling strategy included a transect of sites strategically positioned in the South Pacific to recover Paleogene carbonates buried under red clay sequences at present latitudes of 40&amp;#176;&amp;#8211;52&amp;#176;S in 4650 &amp;#8211; 5075 meters of water depth. Due to technical issues we no longer will be able to reach the deeper sites. Therefore, the focus of Expedition 378 will be now to obtain a continuous sedimentary record of a previously single hole, rotary-drilled, spot-cored, classic Cenozoic high-latitude DSDP Site 277 and provide a crucial, multiple hole, mostly APC-cored, continuous record of the intermediate-depth Subantarctic South Pacific Ocean from the Latest Cretaceous to late Oligocene.&lt;/p&gt;

Tracing the thermohaline Conveyor Belt circulation; from the Drake Passage to the Pacific Ocean

2020 ◽  
Author(s):  
Sara Berglund ◽  
Kristofer Döös ◽  
Jonas Nycander
Keyword(s):  
Pacific Ocean ◽  
Water Mass ◽  
Drake Passage ◽  
Conveyor Belt ◽  
Volume Transport ◽  
Equatorial Undercurrent ◽  
Internal Mixing ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Water Mass Transformation

&lt;p&gt;This study describes an important pathway of the thermohaline conveyor belt circulation and connects the geographical distribution of water masses with water mass transformation.&amp;#160;&lt;br&gt;In the Southern Ocean, cold and fresh water up-wells to the surface and returns northward, entering the Pacific, Atlantic and Indian Ocean. This reflects an important part of the thermohaline conveyor belt circulation. As the water flows northward, it changes temperature and salinity, and thus density. These changes can be caused either by internal mixing or air-sea interactions.&amp;#160;&lt;/p&gt;&lt;p&gt;In this study, Lagrangian trajectories are used to follow the pathway from Drake Passage to the warm Pacific Ocean. Trajectories are started in the Drake Passage, and are ended when they either reach 25$^\circ$C or return to the Drake Passage. The trajectories entering the Pacific Ocean follow the Antarctic circumpolar current and separate then into two pathways. The first enters the Pacific Ocean close to the South American coast and flows along the coast until it reaches 25$^\circ$C close to the equator. The second pathway, which corresponds to most of the total volume transport entering the Pacific, are subducted around 40$^\circ$S. The water then moves westward until it reaches Australia where it turns northward and ultimately joins the equatorial undercurrent.&amp;#160;&lt;/p&gt;&lt;p&gt;Along these two pathways, the water changes temperature and salinity, going from cold and fresh to warm and saline. Preliminary results indicate that the water mass transformation for the first pathway are due to air-sea interactions, and internal mixing for the second.&amp;#160;&lt;/p&gt;

New constraints upon isotope variation during the early Cretaceous (Barremian–Cenomanian) from the Pacific Ocean

2003 ◽  
Vol 140 (5) ◽  
pp. 513-522 ◽  
Author(s):  
GREGORY D. PRICE
Keyword(s):  
Pacific Ocean ◽  
Carbon Isotope ◽  
Hydrothermal Activity ◽  
Intermediate Water ◽  
Ontong Java Plateau ◽  
Oceanic Anoxic Event ◽  
The Pacific ◽  
Carbon And Oxygen Isotope ◽  
Isotope Profile ◽  
The Pacific Ocean

Carbon and oxygen isotope data from a succession of Cretaceous (Barremian–Cenomanian) age recovered from the Pacific Ocean (DSDP site 463) are presented. The carbon isotope curve reveals a large isotope excursion within the early Aptian where δ13C values reach ~4.8‰ in the L. cabri–G. ferreolensis foraminifera zone. A decrease in δ13C values is observed at the base G. algerianus zone, before a return to more positive values at the top of the G. algerianus–T. bejaouaensis zone. The pronounced early Aptian positive event is preceded by a large negative isotope excursion, confined to the G. blowi zone. Synchronous with this excursion are increased total organic carbon values and increases in Mn and Fe concentrations. Integrated biostratigraphic and magnetostratigraphic data, together with the carbon isotope profile, suggest that the organic-rich units of site 463 are correlatable with Oceanic Anoxic Event 1a. The input of isotopically light volcanic CO2 in concert with the intensification and upwelling of intermediate water enriched in 12C could account for the observed trends. A potential trigger may have been the destabilization of the water column and the prodigious CO2 emissions associated with hydrothermal activity and the emplacement of the Ontong Java Plateau. Coupled with faunal evidence, the subsequent positive carbon isotope excursion is interpreted to be resulting from high, but decreasing, productivity and possibly increasing ocean stratification resulting in strong carbon isotopic gradients and 13C-enriched surface waters. The decrease in δ13C within the G. algerianus zone is coincident with more positive δ18O values. If these are interpreted in terms of temperature this interval may be characterized by a period of cooling and possibly a waning of Corg cycling. A return to lower δ13C values during the middle Albian is considered to be related to the increased influence of upwelling, as opposed to a waning of Corg cycling. Upwelling introduced isotopically light carbon to the surface, arresting the stratified oceanic conditions.

25.—Challenger's Voyage and the Black Sea Investigations at the close of the Nineteenth Century.

1972 ◽  
Vol 72 (1) ◽  
pp. 273-275
Author(s):  
I. A. Fedosseyev ◽  
A. F. Plakhotnick
Keyword(s):  
Nineteenth Century ◽  
World Ocean ◽  
The Arctic ◽  
The Black Sea ◽  
Important Work ◽  
The Pacific ◽  
The World ◽  
Antarctic Continent ◽  
The Pacific Ocean ◽  
The Antarctic

Though Russia, in contrast with England, had no broad access to the oceans, Russian oceanographers always took a great interest in the world ocean investigations. To confirm this we would first of all like to mention the Russian cruises around the world, made by I. F. Krusenstern and Ju. F. Lisjansky in 1803–06, V. M. Golovnin in 1806–13 and 1817–19, M. P. Lazarev in 1819–21 and 1822–25 (the second voyage, the main result of which was the discovery of the Antarctic Continent, was made together with F. F. Bellingshauzen), O. E. Kotsebu in 1815–18 and 1823–26, and F. O. Litke in 1826–29. The names of several Russian explorers who carried on important work in various parts of the Arctic and the Pacific Oceans in different periods of the nineteenth century are well known. At one time valuable results of the oceanological investigations, carried out by Admiral S. O. Makarov on the ship Vitjaz in the Pacific Ocean in 1886–89, attracted much attention. The fact that Vitjaz is lettered on the pediment of the Oceanographical Museum of Monaco among the ten ships most distinguished in oceanographical explorations from the whole world testifies to the scientific importance of Makarov's investigations.

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