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  • 1
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    On the southerly extent of the Antarctic Circumpolar the southeast Pacific (2020)
    Details
    Publication Date: 2021-05-19
    Description: A front at 67°S in the Bellingshausen Sea at 85°W is shown to be part of the Antarctic Circumpolar Current (ACC) and the southernmost zone of concentrated eastward transport at that longitude. The front lies 6° south of the Polar Front at 88°W and 3° north of the Continental Water Boundary. The front is continuous to the east through Drake Passage where it forms a southern branch of the Polar Front, for which reason we have named it the Southern Polar Front. Data from a towed profiling CTD were able to distinguish the Polar Front from the Southern Polar Front, even though they were only 0.5° apart. Thus the width of the ACC south of the Polar Front varied considerably. About a third of the transport of the ACC also lay south of the Polar Front, with 15 Sv carried by the Southern Polar Front alone at 85°W. Distinguishing features of the Southern Polar Front were a water mass boundary associated with a zone of concentrated baroclinic flow and a surface salinity minimum. These features also have been found at the Greenwich Meridian at 53°S, so the Southern Polar Front can be traced round at least a quarter of the globe. To the west of the Bellingshausen Sea both Eltanin data and the Fine Resolution Antarctic Model show that the AAC is at its narrowest at 145°W, where its southern boundaries lie as far north as 56°S. At this longitude the ACC meets the topographic barrier of the Pacific-Antarctic Ridge. To conserve potential vorticity the current is forced to make a southward loop as it crosses the ridge and the current broadens dramatically. The flow remains broad until forced to sharpen by the constriction of Drake Passage. A similar broadening of the ACC is seen where it crosses the Southwest Indian Ridge south of Africa at 30°E. Here it remains broad until it encounters the Kerguelen Plateau. Thus the eastern boundaries of both the Weddell and Ross Gyres are determined by where the ACC crosses midocean ridges.
    Description: Published
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed
    Format: pp.933-954
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  • 2
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    Connectivity pathways and advection timescales along the Antarctic continental shelf from a Lagrangian perspective (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-08-24
    Description: The Antarctic Slope Current (ASC) and Antarctic Coastal Current advect heat, freshwater, nutrients, and biological organisms westward around the Antarctic margin, providing a connective link between different sectors of the continental shelf. However, the timescales over which these currents transport water along the shelf, and the strength and pathways of connectivity around the continent, remain poorly understood. We use daily velocity fields from a global high-resolution ocean-sea ice model, combined with Lagrangian particle tracking, to provide a baseline estimate of advection timescales and improve our understanding of circumpolar connectivity around Antarctica. Analysis of particle trajectory experiments shows that advection around the continent is typically rapid with peak transit times of 1–5 years for particles to travel 90° of longitude downstream. The ASC plays a key role in driving connectivity in East Antarctica and the Weddell Sea, while the Coastal Current controls connectivity in West Antarctica, the eastern Antarctic Peninsula, and along the continental shelf east of Prydz Bay. Crucially, the West Antarctic sector, which has experienced rapid melting, has widespread connectivity with all regions of the Antarctic shelf. These findings assist us in understanding the locations and timescales over which anomalies, such as meltwater from the Antarctic Ice Sheet, can be redistributed downstream.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 3
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    Abyssal ocean overturning slowdown and warming driven by Antarctic meltwater (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-05-04
    Description: The abyssal ocean circulation is a key component of the global meridional overturning circulation, cycling heat, carbon, oxygen and nutrients throughout the world ocean. The strongest historical trend observed in the abyssal ocean is warming at high southern latitudes, yet it is unclear what processes have driven this warming, and whether it is linked to a slowdown in the ocean's overturning circulation. Furthermore, future change in the abyssal overturning remains uncertain, with the latest CMIP6 projections not accounting for dynamic ice-sheet melt. In this talk I will present new transient forced high-resolution coupled ocean – sea-ice model simulations to show that under a high emissions scenario, abyssal warming is set to accelerate over the next 30 years. We find that meltwater input around Antarctica drives a contraction of Antarctic Bottom Water (AABW), opening a pathway that allows warm Circumpolar Deep Water greater access to the continental shelf. The reduction in AABW formation results in warming and ageing of the abyssal ocean, consistent with recent measurements. In contrast, projected wind and thermal forcing has little impact on the properties, age, and volume of AABW. These results highlight the critical importance of Antarctic meltwater in setting the abyssal ocean overturning, with implications for global ocean biogeochemistry and climate that could last for centuries.
    Language: English
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  • 4
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    Wind– and sea-ice–driven interannual variability of Antarctic Bottom Water formation (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-06-05
    Description: Antarctic Bottom Water (AABW) is a major component of the global overturning circulation, originating around the Antarctic continental margin. In recent decades AABW has both warmed and freshened, but there is also evidence of large interannual variability. The causes of this underlying variability are not yet fully understood, in part due to a lack of ocean and air-sea-ice flux measurements in the region. Here, we simulate the formation and export of AABW from 1958 to 2018 using a global, eddying ocean–sea-ice model in which the four AABW formation regions and transports agree reasonably well with observations. The simulated formation and export of AABW exhibits strong interannual variability which is not correlated between the different formation regions. Reservoirs of very dense waters at depth in the Weddell and Ross Seas following 1-2 years of strong surface water mass transformation can lead to higher AABW export for up to a decade. In Prydz Bay and at the Adélie Coast in contrast, dense water reservoirs do not persist beyond 1 year which we attribute to the narrower shelf extent in the East Antarctic AABW formation regions. The main factor controlling years of high AABW formation are weaker easterly winds, which reduce sea ice import into the AABW formation region, leaving increased areas of open water primed for air-sea buoyancy loss and convective overturning. Our study highlights the variability of simulated AABW formation in all four formation regions, with potential implications for interpreting trends in observational data using only limited duration and coverage.
    Language: English
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  • 5
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    On the role of Dense Shelf Water overflows in the dynamics of the Antarctic Slope Current (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-06-08
    Description: The Antarctic Slope Current is guided by the topographic gradient of the continental slope and acts as a dynamical barrier between the continental shelf and the open ocean. Exchanges of water masses across the shelf break are important for future predictions of the Antarctic ice shelves and the ventilation of the deep ocean. The Antarctic Slope Current is surface-intensified in many regions but bottom-intensified in regions of dense overflows. This study investigates the role of dense overflows in contributing to the dynamics of the bottom-intensified flow using a 0.1° global ocean-sea ice model. The occurrence of the bottom-intensification is tightly linked to dense overflows and bottom speeds correlate with dense overflows on interannual time scales. A lack of vertical connectivity between the bottom and surface flow, however, suggests that the along-slope bottom water flows are coincidentally co-located with the Antarctic Slope Current, rather than dynamically a part of the current.
    Language: English
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  • 6
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    Antarctic Slope Current control on cross-slope heat transport (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-06-28
    Description: Ocean heat transport towards Antarctica directly drives the melting of Antarctic ice shelves, modulating sea level rise and the formation of Antarctic Bottom Water. A common dynamical assumption is that heat transport across the Antarctic continental slope is modulated by the strength of the Antarctic Slope Current (ASC), which is thought to act as a barrier to cross-slope heat transport. However, observations of the ASC are too scarce to investigate its relationship to poleward heat transport across large circumpolar spatial scales, or over long temporal scales. Also, until recently, ocean models lacked the spatial resolution required to accurately represent the ASC or the eddy heat transport onto the Antarctic shelf. In this study, we analyze the relationship between the ASC and the cross-slope heat transport in a circumpolar, eddy-rich ocean and sea ice simulation. We find that the local strength of the time-mean ASC is not a good predictor of local cross-slope heat transport, i.e., spatial variability in the ASC is not related to spatial variability in poleward heat transport. However, there is a relationship between ASC strength and cross-slope heat transport in the temporal domain. We quantify the strength of the relationship across different time scales (sub-seasonal, seasonal and interannual) and across varying model resolution (from 1/10º to 1/20º to 1/40º).
    Language: English
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  • 7
    Electronic Resource
    Electronic Resource
    Physicochemical Micromethods of Test for Petroleum Products (1950)
    s.l. : American Chemical Society
    Analytical chemistry 22 (1950), S. 188-191 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac60037a040
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  • 8
    Electronic Resource
    Electronic Resource
    Sugar Chromatography of Mammary Gland Extracts (1952)
    [s.l.] : Nature Publishing Group
    Nature 169 (1952), S. 1103-1104 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Our earlier report (see Malpress2) showed the presence of a fraction obtained by the direct trichlor- acetic acid extraction of lactating guinea pig and cow tissues, which gave evidence of the liberation of galactose and glucose after acid hydrolysis ; it also commented upon the liberation of ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/1691103b0
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  • 9
    Electronic Resource
    Electronic Resource
    Bacterial Arylsulphatase (1952)
    [s.l.] : Nature Publishing Group
    Nature 169 (1952), S. 711-712 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In the present investigation, a wide range of bacterial species has been examined for the presence of arylsulphatase, using potassium phenolphthalein disulphate as substrate. This compound has a number of advantages as a substrate; for example, it is stable under conditions used for sterilizing ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/169711b0
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  • 10
    Electronic Resource
    Electronic Resource
    1,000-Curie Cobalt-60 Units for Radiation Therapy (1951)
    [s.l.] : Nature Publishing Group
    Nature 168 (1951), S. 1035-1036 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Any attempt to obtain an improvement in the depth-dose by increasing the amount of radium, and correspondingly improving the ratio between the source-to-tumour distance and the source-to-skin distance, is limited by the high cost of radium, and by the required increase in the volume of the source. ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/1681035a0
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