Downslope flow observations near Cape Adare shelf-break

2004 ◽  
Vol 16 (2) ◽  
pp. 199-204 ◽  
Author(s):  
A. BERGAMASCO ◽  
V. DEFENDI ◽  
G. BUDILLON ◽  
G. SPEZIE
Keyword(s):  
Ross Sea ◽  
Spatial Scales ◽  
Shelf Break ◽  
Investigation Area ◽  
Shelf Slope ◽  
Antarctic Continental Shelf ◽  
Victoria Land ◽  
Downslope Flow ◽  
The Antarctic ◽  
Continental Shelf Break

The analysis of two high resolution hydrological datasets acquired during the 1997 and 2001 summers across the Antarctic continental shelf-break near Cape Adare (Ross Sea) is presented. The main focus of these cruises was the investigation of the overflow of the High Salinity Shelf Water (HSSW). This dense and salty water mass forms along Victoria Land and flows northward, descending the slope near Cape Adare. Water types characterizing the study area are detected through vertical salinity profiles and by the horizontal distributions of the temperature and salinity. Temperature and salinity hydrological sections obtained by means of objective analysis method well describe the water masses interactions at the shelf/slope edge. The 1997 dataset shows evidence of a strong HSSW signature on the slope, but it is difficult to quantify the spatial scales involved in the spreading mechanism, because the overflow takes place at the edge of the investigation area. The 2001 data, collected at the same position with improved spatial and temporal resolution, clearly indicates the absence of a “true” HSSW downslope process. Even though no estimation of the amount of downslope flow can be given at present due to the resolution of the available dataset, it is possible to get a better phenomenological picture of the process by comparing the two years.

Spatial and temporal variability of the Antarctic Slope Current in an eddying ocean-sea ice model

2021 ◽  
Author(s):  
Wilma Huneke ◽  
Adele Morrison ◽  
Andy Hogg
Keyword(s):  
Continental Shelf ◽  
Temporal Variability ◽  
Shelf Break ◽  
Spatial And Temporal Variability ◽  
Shelf Water ◽  
Antarctic Continental Shelf ◽  
Antarctic Slope Current ◽  
The Antarctic ◽  
Continental Shelf Break ◽  
Ice Model

<p> <span><span>The basal melt rate of Antarctica's ice shelves is largely controlled by heat delivered from the Southern Ocean to the Antarctic continental shelf. The Antarctic Slope Current (ASC) is an almost circumpolar feature that encircles Antarctica along the continental shelf break in an anti-clockwise direction. Because the circulation is to first order oriented along the topographic slope, it inhibits exchange of water masses between the Southern Ocean and the Antarctic continental shelf and thereby impacts cross-slope heat supply. Direct observations of the ASC system are sparse, but indicate a highly variable flow field both in time and space. Given the importance of the circulation near the shelf break for cross-shelf exchange of heat, it is timely to further improve our knowledge of the ASC system. This study makes use of the global ocean-sea ice model ACCESS-OM2-01 with a 1/10 degree horizontal resolution and describes the spatial and temporal variability of the velocity field. We categorise the modelled ASC into three different regimes, similar to previous works for the associated Antarctic Slope Front: (i) A surface-intensified current found predominantly in East Antarctica, (ii) a bottom-intensified current found downstream of the dense shelf water formation sit</span><span>e</span><span>s in the Ross, Weddell, and Prydz Bay Seas, and (iii) a reversed current found in West Antarctica where the eastward flowing Antarctic Circumpolar Current impinges onto the continental shelf break. We find that the temporal variability of the Antarctic Slope Current varies between the regimes. In the bottom-intensified regions, the variability is set by the timing of the dense shelf water overflows, whereas the surface-intensified flow responds to the sub-monthly variability in the wind field.</span></span></p>

Pathways and timescales of connectivity around the Antarctic continental shelf 

2021 ◽  
Author(s):  
Hannah Dawson ◽  
Adele Morrison ◽  
Veronica Tamsitt ◽  
Matthew England
Keyword(s):  
Continental Shelf ◽  
Ross Sea ◽  
Coastal Current ◽  
West Antarctica ◽  
Source Regions ◽  
Freshwater Forcing ◽  
Antarctic Continental Shelf ◽  
Antarctic Continent ◽  
Antarctic Slope Current ◽  
The Antarctic

<p><span xml:lang="EN-US" data-contrast="auto"><span>The Antarctic margin is surrounded by two westward flowing currents: the Antarctic Slope Current and the Antarctic Coastal Current. The former influences key processes near the Antarctic margin by regulating the flow of heat and nutrients onto and off the continental shelf, while together they </span></span><span xml:lang="EN-US" data-contrast="auto"><span>advect</span></span><span xml:lang="EN-US" data-contrast="auto"><span> nutrients, biological organisms, and temperature and salinity anomalies around the coastline, providing a connective link between different shelf regions. However, the extent to which these currents transport water from one sector of the continental shelf to another, and the timescales over which this occurs, remain poorly understood. Concern that crucial water formation sites around the Antarctic coastline could respond to non-local freshwater forcing </span></span><span><span xml:lang="EN-US" data-contrast="auto"><span>from ice shel</span></span></span><span><span xml:lang="EN-US" data-contrast="auto"><span>f meltwater</span></span></span> <span xml:lang="EN-US" data-contrast="auto"><span>motivates a more thorough understanding of zonal connectivity around Antarctica. In this study, we use daily velocity fields from a global high-resolution ocean-sea ice model, combined with the <span>Lagrangian</span> tracking software Parcels, to investigate the pathways and timescales connecting different regions of the Antarctic continental shelf<span> with a view to understanding</span><span> the timescales of meltwater transport around the continent</span>. Virtual particles are released over the continental shelf, poleward of the 1000 <span>metre</span> isobath, and are tracked for 20 years. Our results show a strong seasonal cycle connecting different sectors of the Antarctic continent, with more particles arriving further downstream during winter than during summer months. Strong advective links exist between West Antarctica and the Ross Sea while shelf geometry in some other regions acts as barriers to transport. We also highlight the varying importance of the Antarctic Slope Current and Antarctic Coastal Current in connecting different sectors of the coastline. Our results help to improve our understanding of circum-Antarctic connectivity <span>and the timescales </span><span>of meltwater transport from source regions to downstream </span><span>shelf locations. </span><span>Further</span><span>more, t</span><span>he timescales and pathways we </span><span>present </span><span>p</span>rovide a baseline from which to assess long-term changes in Antarctic coastal circulation due to local and remote forcing.<br></span></span></p>

Palaeomagnetic results from the middle Tertiary Meander Intrusives of northern Victoria Land, East Antarctica

1996 ◽  
Vol 8 (1) ◽  
pp. 61-72 ◽  
Author(s):  
Elena Belluso ◽  
Roberto Lanza
Keyword(s):  
Remanent Magnetization ◽  
Ross Sea ◽  
East Antarctica ◽  
Magnetic Mineralogy ◽  
Tilt Correction ◽  
Palaeomagnetic Data ◽  
Victoria Land ◽  
Geological Models ◽  
Laboratory Investigations ◽  
The Antarctic

The Tertiary stocks (Meander Intrusives) cropping out along the coasts of the Ross Sea were sampled for a palaeomagnetic study during the sixth Italian expedition to northern Victoria Land. Laboratory investigations concerned magnetic mineralogy and remanent magnetization. Minerals of the magnetiteulvöspinel series occur in the rocks from all stocks, with low-Ti titanomagnetite usually prevalent. Haematite and goethite occur in small amounts as alteration products. Large secondary components commonly screen the characteristic remanent magnetization and were removed by thermal or AF demagnetization at temperatures or peak-fields higher than 360°C and 20 mT respectively. A total of 10 VGPs were obtained from radiometrically dated rocks (42–22 Ma); the averaged position (69°S, 334°E; α95=9.9°) is the first middle Tertiary palaeomagnetic pole for East Antarctica, and gives evidence for a reversal in the course of the APW path. This evidence is not substantially altered by a supposed tilt-correction consistent with geophysical and geological models for the uplift of the Transantarctic Mountains. No definite conclusion about relative movements between East Antarctica and the Antarctic Peninsula can be drawn from the existing palaeomagnetic data.

scholarly journals Additions to the lichen flora of Victoria Land, Antarctica

2011 ◽  
Vol 32 (2) ◽  
pp. 123-138 ◽  
Author(s):  
Jerzy Smykla ◽  
Beata Krzewicka ◽  
Karina Wilk ◽  
Steven Emslie ◽  
Lucyna Śliwa
Keyword(s):  
Ross Sea ◽  
Land Area ◽  
Victoria Land ◽  
Continental Antarctica ◽  
The Antarctic ◽  
Lichen Flora

Additions to the lichen flora of Victoria Land, Antarctica Lichens of relict penguin colonies and sites affected by active penguin colonies were investigated in Victoria Land, Ross Sea sector, continental Antarctica. A total of 17 coastal sites, seven in northern and ten in southern Victoria Land, have been investigated across 7° of latitude from 71° to 78°S. Altogether 40 taxa of lichens have been identified. Four of the recorded species are new to the Antarctic - Caloplaca erecta, C. soropelta, C. tominii and Physcia tenella; two species are new to the Victoria Land area - Lecania nylanderiana and Lecanora polytropa. The first lichen records from Beaufort Island are also provided. Data presented here expand the knowledge on the occurrence, diversity and distribution of Victoria Land lichens.

scholarly journals Exploring the impact of atmospheric forcing and basal drag on the Antarctic Ice Sheet under Last Glacial Maximum conditions

2021 ◽  
Vol 15 (1) ◽  
pp. 215-231
Author(s):  
Javier Blasco ◽  
Jorge Alvarez-Solas ◽  
Alexander Robinson ◽  
Marisa Montoya
Keyword(s):  
Boundary Conditions ◽  
Continental Shelf ◽  
Last Glacial Maximum ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Shelf Break ◽  
Ice Volume ◽  
Basal Friction ◽  
The Antarctic ◽  
Continental Shelf Break

Abstract. Little is known about the distribution of ice in the Antarctic Ice Sheet (AIS) during the Last Glacial Maximum (LGM). Whereas marine and terrestrial geological data indicate that the grounded ice advanced to a position close to the continental-shelf break, the total ice volume is unclear. Glacial boundary conditions are potentially important sources of uncertainty, in particular basal friction and climatic boundary conditions. Basal friction exerts a strong control on the large-scale dynamics of the ice sheet and thus affects its size and is not well constrained. Glacial climatic boundary conditions determine the net accumulation and ice temperature and are also poorly known. Here we explore the effect of the uncertainty in both features on the total simulated ice storage of the AIS at the LGM. For this purpose we use a hybrid ice sheet shelf model that is forced with different basal drag choices and glacial background climatic conditions obtained from the LGM ensemble climate simulations of the third phase of the Paleoclimate Modelling Intercomparison Project (PMIP3). Overall, we find that the spread in the simulated ice volume for the tested basal drag parameterizations is about the same range as for the different general circulation model (GCM) forcings (4 to 6 m sea level equivalent). For a wide range of plausible basal friction configurations, the simulated ice dynamics vary widely but all simulations produce fully extended ice sheets towards the continental-shelf break. More dynamically active ice sheets correspond to lower ice volumes, while they remain consistent with the available constraints on ice extent. Thus, this work points to the possibility of an AIS with very active ice streams during the LGM. In addition, we find that the surface boundary temperature field plays a crucial role in determining the ice extent through its effect on viscosity. For ice sheets of a similar extent and comparable dynamics, we find that the precipitation field determines the total AIS volume. However, precipitation is highly uncertain. Climatic fields simulated by climate models show more precipitation in coastal regions than a spatially uniform anomaly, which can lead to larger ice volumes. Our results strongly support using these paleoclimatic fields to simulate and study the LGM and potentially other time periods like the last interglacial. However, their accuracy must be assessed as well, as differences between climate model forcing lead to a large spread in the simulated ice volume and extension.

scholarly journals Acceleration and Overturning of the Antarctic Slope Current by Winds, Eddies, and Tides

2019 ◽  
Vol 49 (8) ◽  
pp. 2043-2074 ◽  
Author(s):  
Andrew L. Stewart ◽  
Andreas Klocker ◽  
Dimitris Menemenlis
Keyword(s):  
Sea Ice ◽  
Continental Shelf ◽  
Continental Slope ◽  
Mesoscale Eddy ◽  
Shelf Break ◽  
Ekman Transport ◽  
Global Ocean ◽  
Antarctic Slope Current ◽  
The Antarctic ◽  
Continental Shelf Break

AbstractAll exchanges between the open ocean and the Antarctic continental shelf must cross the Antarctic Slope Current (ASC). Previous studies indicate that these exchanges are strongly influenced by mesoscale and tidal variability, yet the mechanisms responsible for setting the ASC’s transport and structure have received relatively little attention. In this study the roles of winds, eddies, and tides in accelerating the ASC are investigated using a global ocean–sea ice simulation with very high resolution (1/48° grid spacing). It is found that the circulation along the continental slope is accelerated both by surface stresses, ultimately sourced from the easterly winds, and by mesoscale eddy vorticity fluxes. At the continental shelf break, the ASC exhibits a narrow (~30–50 km), swift (>0.2 m s−1) jet, consistent with in situ observations. In this jet the surface stress is substantially reduced, and may even vanish or be directed eastward, because the ocean surface speed matches or exceeds that of the sea ice. The shelfbreak jet is shown to be accelerated by tidal momentum advection, consistent with the phenomenon of tidal rectification. Consequently, the shoreward Ekman transport vanishes and thus the mean overturning circulation that steepens the Antarctic Slope Front (ASF) is primarily due to tidal acceleration. These findings imply that the circulation and mean overturning of the ASC are not only determined by near-Antarctic winds, but also depend crucially on sea ice cover, regionally-dependent mesoscale eddy activity over the continental slope, and the amplitude of tidal flows across the continental shelf break.

Fishes of the genus Artedidraco (Pisces, Artedidraconidae) from the Ross Sea, Antarctica, with the description of a new species and a colour morph

1999 ◽  
Vol 11 (1) ◽  
pp. 13-22 ◽  
Author(s):  
Joseph T. Eastman ◽  
Richard R. Eakin
Keyword(s):  
New Species ◽  
Ross Sea ◽  
Colour Pattern ◽  
Bottom Fauna ◽  
Colour Morph ◽  
Antarctic Continental Shelf ◽  
Meristic Variation ◽  
Visceral Anatomy ◽  
The Antarctic ◽  
A New Species

Notothenioid fish of the artedidraconid genus Artedidraco are a little studied, component of the bottom fauna on the Antarctic continental shelf. Trawling in the south-western Ross Sea, especially in shallow areas with sponge beds, yielded a collection of 65 specimens of Artedidraco. These included all four species occurring in the Ross Sea as well as a new species. The new species Artedidraco glareobarbatus is described and illustrated. This species is most similar to A. orianae, but is distinguished by barbel morphology, by higher counts for dorsal rays and vertebrae, by lower counts for upper lateral-line scales and by colour pattern and visceral anatomy. A distinctive spotted colour morph of A. shackletoni is also documented and compared with the typical barred morph. Depth distribution and meristic variation among species of Artedidraco are summarized, and a taxonomic key to the six species is provided.

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