The calving and drift of iceberg B-9 in the Ross Sea, Antarctica

1990 ◽  
Vol 2 (3) ◽  
pp. 243-257 ◽  
Author(s):  
Harry (J.R.) Keys ◽  
S.S. Jacobs ◽  
Don Barnett
Keyword(s):  
Ocean Circulation ◽  
Ross Sea ◽  
Maximum Velocity ◽  
Open Water ◽  
Ice Thickness ◽  
Ice Shelf ◽  
East Central ◽  
North West ◽  
Ross Ice Shelf ◽  
Subsurface Current

Major rifts is the Ross Ice Shelf controlled the October 1987 calving of the 154 × 35 km “B-9” iceberg, one of the longest on record. The 2000 km, 22 month drift of this iceberg and the quite different tracks of smaller bergs that calved with it have extended our understanding of the ocean circulation in the Ross Sea. B-9 initially moved north-west for seven months until deflected southward by a subsurface current which caused it to collide with the ice shelf in August 1988. It then completed a 100 km-radius gyre on the east-central shelf before resuming its north-westerly drift. Based upon weekly locations, derived from NOAA-10 and DMSP satellite and more frequent ARGOS data buoy positions, B-9 moved at an average speed of 2.4 km day−1 over the continental shelf. It was not grounded there at any time, but cast a large shadow of open water or reduced ice thickness during the austral winters. B-9 was captured by the continental slope current in May 1989, and attained a maximum velocity of 13 km day−1 before breaking into three pieces north of Cape Adare in early August 1989.

scholarly journals Last Glacial Maximum-Holocene Glacial and Depositional History From Sediment Cores at Coulman High Beneath the Ross Ice Shelf, Antarctica

2021 ◽  
Author(s):  
◽  
Sanne M Maas
Keyword(s):  
Last Glacial Maximum ◽  
Ross Sea ◽  
Sediment Cores ◽  
Ice Sheet ◽  
Open Water ◽  
Glacial Maximum ◽  
Ice Shelf ◽  
Last Glacial ◽  
Ross Ice Shelf ◽  
Grounding Line

<p>Sediment Cores collected from the shallow sub-sea floor beneath the Ross Ice Shelf at Coulman High have been analysed using sedimentological techniques to constrain the retreat history of the Last Glacial Maximum (LGM) ice sheet in the Ross Embayment, and to determine when the modern-day calving line location of the Ross Ice Shelf was established. A characteristic vertical succession of facies was identified in these cores, that can be linked to ice sheet and ice shelf extent in the Ross Embayment. The base of this succession consists of unconsolidated, clast rich muddy diamicts, and is interpreted to be deposited subglacially or in a grounding line proximal environment on account of a distinct provenance in the clast content which can only be attributed to subglacial transport from the Byrd Glacier 400 km to the south of the drill site. This is overlain by a mud with abundant clasts, similar in character to a granulated facies that has been documented previously in the Ross Sea, and is interpreted as being a characteristic grounding line lift-o facies in a sub-ice shelf setting. These glacial proximal facies pass upward into a mud, which comprises three distinctive units. i) Muds with sub-mm scale laminae resulting from traction currents occurring near the grounding line in a sub-ice shelf environment overlain by, ii) muds with sub-mm scale laminae and elevated biogenic content (diatoms and foraminifera) and sand/gravel clasts, interpreted as being deposited in open water conditions, passing up into a iii) bioturbated mud, interpreted as being deposited in sub-ice shelf environment, proximal to the calving line. The uppermost facies consists of a 20 cm thick diatom ooze with abundant clasts and pervasive bioturbation, indicative of a condensed section deposited during periodically open marine conditions. During post-LGM retreat of the ice sheet margin in western Ross Sea, and prior to the first open marine conditions at Coulman High, it is hypothesized that the grounding and calving line were in relative close proximity to each other. As the calving line became "pinned" in the Ross Island region, the grounding line likely continued its retreat toward its present day location. New corrected radiocarbon ages on the foraminifera shells in the interval of laminated muds with clasts, provide some of the first inorganic ages from the Ross Sea, and strengthen inferences from previous studies, that the first open marine conditions in the vicinity of Ross Island were 7,600 14C yr BP. While retreat of the calving line south of its present day position is implied during this period of mid-Holocene warmth prior to its re-advance, at present it is not possible to constrain the magnitude of retreat or attribute this to climate change rather than normal calving dynamics.</p>

scholarly journals Ice Movement Studies on the Skelton Glacier

1961 ◽  
Vol 3 (29) ◽  
pp. 873-878
Author(s):  
Charles R. Wilson ◽  
A. P. Crary
Keyword(s):  
Ross Sea ◽  
Ice Thickness ◽  
Strain Rates ◽  
Shelf Area ◽  
Dry Valleys ◽  
Ice Shelf ◽  
The West ◽  
Ross Ice Shelf ◽  
High Plateau ◽  
Plateau Area

The volume of ice that flows annually from the Skelton Glacier on the west side of the Ross Ice Shelf between the Worcester and Royal Society Ranges was determined during 1958–59 traverse operations to be approximately 791 × 106 m.3 or 712 × 106 m.3 water equivalent. Annual accumulation on the Skelton névé field and small cirque glaciers is estimated to be 1,018 × 106 m.3 water equivalent, but this figure can be reduced to 712 × 106 m.3 by assuming that 30 per cent of the expected accumulation in the lower slopes of the glacier is lost to adjacent areas of the Ross Ice Shelf by katabatic winds. It is evident that little or no contribution to the nourishment of the Skelton Glacier comes from the high plateau area of East Antarctica. It is suggested that this condition exists generally in the western Ross Sea and Ross Shelf area, and is responsible for the existence of the present “dry” valleys in the McMurdo Sound area.Some estimates of local ice regime are made at two sites on the glacier where ice thickness and strain rates are known.

Modelling the ocean circulation beneath the Ross Ice Shelf

2003 ◽  
Vol 15 (1) ◽  
pp. 13-23 ◽  
Author(s):  
DAVID M. HOLLAND ◽  
STANLEY S. JACOBS ◽  
ADRIAN JENKINS
Keyword(s):  
Ocean Circulation ◽  
General Circulation ◽  
Ross Sea ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Shelf Water ◽  
Ice Shelf ◽  
Ross Ice Shelf ◽  
The North ◽  
Ice Shelf Water

We applied a modified version of the Miami isopycnic coordinate ocean general circulation model (MICOM) to the ocean cavity beneath the Ross Ice Shelf to investigate the circulation of ocean waters in the sub-ice shelf cavity, along with the melting and freezing regimes at the base of the ice shelf. Model passive tracers are utilized to highlight the pathways of waters entering and exiting the cavity, and output is compared with data taken in the cavity and along the ice shelf front. High Salinity Shelf Water on the western Ross Sea continental shelf flows into the cavity along the sea floor and is transformed into Ice Shelf Water upon contact with the ice shelf base. Ice Shelf Water flows out of the cavity mainly around 180°, but also further east and on the western side of McMurdo Sound, as observed. Active ventilation of the region near the ice shelf front is forced by seasonal variations in the density structure of the water column to the north, driving rapid melting. Circulation in the more isolated interior is weaker, leading to melting at deeper ice and refreezing beneath shallower ice. Net melting over the whole ice shelf base is lower than other estimates, but is likely to increase as additional forcings are added to the model.

scholarly journals Last Glacial Maximum-Holocene Glacial and Depositional History From Sediment Cores at Coulman High Beneath the Ross Ice Shelf, Antarctica

2021 ◽  
Author(s):  
◽  
Sanne M Maas
Keyword(s):  
Last Glacial Maximum ◽  
Ross Sea ◽  
Sediment Cores ◽  
Ice Sheet ◽  
Open Water ◽  
Glacial Maximum ◽  
Ice Shelf ◽  
Last Glacial ◽  
Ross Ice Shelf ◽  
Grounding Line

<p>Sediment Cores collected from the shallow sub-sea floor beneath the Ross Ice Shelf at Coulman High have been analysed using sedimentological techniques to constrain the retreat history of the Last Glacial Maximum (LGM) ice sheet in the Ross Embayment, and to determine when the modern-day calving line location of the Ross Ice Shelf was established. A characteristic vertical succession of facies was identified in these cores, that can be linked to ice sheet and ice shelf extent in the Ross Embayment. The base of this succession consists of unconsolidated, clast rich muddy diamicts, and is interpreted to be deposited subglacially or in a grounding line proximal environment on account of a distinct provenance in the clast content which can only be attributed to subglacial transport from the Byrd Glacier 400 km to the south of the drill site. This is overlain by a mud with abundant clasts, similar in character to a granulated facies that has been documented previously in the Ross Sea, and is interpreted as being a characteristic grounding line lift-o facies in a sub-ice shelf setting. These glacial proximal facies pass upward into a mud, which comprises three distinctive units. i) Muds with sub-mm scale laminae resulting from traction currents occurring near the grounding line in a sub-ice shelf environment overlain by, ii) muds with sub-mm scale laminae and elevated biogenic content (diatoms and foraminifera) and sand/gravel clasts, interpreted as being deposited in open water conditions, passing up into a iii) bioturbated mud, interpreted as being deposited in sub-ice shelf environment, proximal to the calving line. The uppermost facies consists of a 20 cm thick diatom ooze with abundant clasts and pervasive bioturbation, indicative of a condensed section deposited during periodically open marine conditions. During post-LGM retreat of the ice sheet margin in western Ross Sea, and prior to the first open marine conditions at Coulman High, it is hypothesized that the grounding and calving line were in relative close proximity to each other. As the calving line became "pinned" in the Ross Island region, the grounding line likely continued its retreat toward its present day location. New corrected radiocarbon ages on the foraminifera shells in the interval of laminated muds with clasts, provide some of the first inorganic ages from the Ross Sea, and strengthen inferences from previous studies, that the first open marine conditions in the vicinity of Ross Island were 7,600 14C yr BP. While retreat of the calving line south of its present day position is implied during this period of mid-Holocene warmth prior to its re-advance, at present it is not possible to constrain the magnitude of retreat or attribute this to climate change rather than normal calving dynamics.</p>

Effects of giant icebergs on two emperor penguin colonies in the Ross Sea, Antarctica

2007 ◽  
Vol 19 (1) ◽  
pp. 31-38 ◽  
Author(s):  
Gerald L. Kooyman ◽  
David G. Ainley ◽  
Grant Ballard ◽  
Paul J. Ponganis
Keyword(s):  
Ross Sea ◽  
Emperor Penguin ◽  
Ice Shelf ◽  
West Antarctic Ice Sheet ◽  
North West ◽  
Ross Ice Shelf ◽  
The North ◽  
West Antarctic ◽  
South West ◽  
Wintering Areas

The arrival in January 2001 in the south-west Ross Sea of two giant icebergs, C16 and B15A, subsequently had dramatic affects on two emperor penguin colonies. B15A collided with the north-west tongue of the Ross Ice Shelf at Cape Crozier, Ross Island, in the following months and destroyed the penguins' nesting habitat. The colony totally failed in 2001, and years after, with the icebergs still in place, exhibited reduced production that ranged from 0 to 40% of the 1201 chicks produced in 2000. At Beaufort Island, 70 km NW of Crozier, chick production declined to 6% of the 2000 count by 2004. Collisions with the Ross Ice Shelf at Cape Crozier caused incubating adults to be crushed, trapped in ravines, or to abandon the colony and, since 2001, to occupy poorer habitat. The icebergs separated Beaufort Island from the Ross Sea Polynya, formerly an easy route to feeding and wintering areas. This episode has provided a glimpse of events which have probably occurred infrequently since the West Antarctic Ice Sheet began to retreat 12 000 years ago. The results allow assessment of recovery rates for one colony decimated by both adult and chick mortality, and the other colony by adult abandonment and chick mortality.

scholarly journals Ice Movement Studies on the Skelton Glacier

1961 ◽  
Vol 3 (29) ◽  
pp. 873-878 ◽  
Author(s):  
Charles R. Wilson ◽  
A. P. Crary
Keyword(s):  
Ross Sea ◽  
Ice Thickness ◽  
Strain Rates ◽  
Shelf Area ◽  
Dry Valleys ◽  
Ice Shelf ◽  
The West ◽  
Ross Ice Shelf ◽  
High Plateau ◽  
Plateau Area

The volume of ice that flows annually from the Skelton Glacier on the west side of the Ross Ice Shelf between the Worcester and Royal Society Ranges was determined during 1958–59 traverse operations to be approximately 791 × 106 m.3 or 712 × 106 m.3 water equivalent. Annual accumulation on the Skelton névé field and small cirque glaciers is estimated to be 1,018 × 106 m.3 water equivalent, but this figure can be reduced to 712 × 106 m.3 by assuming that 30 per cent of the expected accumulation in the lower slopes of the glacier is lost to adjacent areas of the Ross Ice Shelf by katabatic winds. It is evident that little or no contribution to the nourishment of the Skelton Glacier comes from the high plateau area of East Antarctica. It is suggested that this condition exists generally in the western Ross Sea and Ross Shelf area, and is responsible for the existence of the present “dry” valleys in the McMurdo Sound area. Some estimates of local ice regime are made at two sites on the glacier where ice thickness and strain rates are known.

scholarly journals Environmental and Oceanographic Conditions at the Continental Margin of the Central Basin, Northwestern Ross Sea (Antarctica) Since the Last Glacial Maximum

Geosciences ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 155
Author(s):  
Fiorenza Torricella ◽  
Romana Melis ◽  
Elisa Malinverno ◽  
Giorgio Fontolan ◽  
Mauro Bussi ◽  
...  
Keyword(s):  
Continental Margin ◽  
Ross Sea ◽  
Time Interval ◽  
Central Basin ◽  
Ice Shelf ◽  
Last Glacial ◽  
Ross Ice Shelf ◽  
Sedimentary Sequences ◽  
Ash Layer ◽  
The Last Glacial

The continental margin is a key area for studying the sedimentary processes related to the advance and retreat of the Ross Ice Shelf (Antarctica); nevertheless, much remains to be investigated. The aim of this study is to increase the knowledge of the last glacial/deglacial dynamics in the Central Basin slope–basin system using a multidisciplinary approach, including integrated sedimentological, micropaleontological and tephrochronological information. The analyses carried out on three box cores highlighted sedimentary sequences characterised by tree stratigraphic units. Collected sediments represent a time interval from 24 ka Before Present (BP) to the present time. Grain size clustering and data on the sortable silt component, together with diatom, silicoflagellate and foraminifera assemblages indicate the influence of the ice shelf calving zone (Unit 1, 24–17 ka BP), progressive receding due to Circumpolar Deep Water inflow (Unit 2, 17–10.2 ka BP) and (Unit 3, 10.2 ka BP–present) the establishment of seasonal sea ice with a strengthening of bottom currents. The dominant and persistent process is a sedimentation controlled by contour currents, which tend to modulate intensity in time and space. A primary volcanic ash layer dated back at around 22 ka BP is correlated with the explosive activity of Mount Rittmann.

scholarly journals A Cross-Sectional Model for West Antarctica

1984 ◽  
Vol 5 ◽  
pp. 95-99 ◽  
Author(s):  
B. J. McInnes ◽  
W. F. Budd
Keyword(s):  
Ross Sea ◽  
Dynamic State ◽  
Ice Thickness ◽  
Cross Sectional ◽  
West Antarctic Ice Sheet ◽  
Ross Ice Shelf ◽  
West Antarctic ◽  
Mass Fluxes ◽  
Ice Stream B ◽  
The One

The dynamic state of the West Antarctic ice sheet has been termed the grand problem of glaciology. An attempt is presented to assess it by simulating the observed ice thickness and ice velocities along a cross-section from ice stream B (Ross Sea) to Pine Island Glacier (Pine Island Bay) with a numerical model developed from the one described by Budd and McInnes (1978). A kinematic analysis with topographical and regime data from various sources shows the mass fluxes observed near the grounding line of the Ross Ice Shelf to be of the order expected for steady-state balance. Deformation of the ice accounts for only a small fraction of the observed flow there. Simulations (to be described in detail elsewhere) with the Budd/McInnes surging mechanism can approximate the existing ice thickness as a post-surge feature but fail to reproduce the high balance velocities. Both these velocities and the existing ice-thickness profile are simulated successfully as a state of steady sliding, with parameterizations involving the ice thickness above that corresponding to buoyancy and realistically assumed longitudinal strain-rates. A range of results is presented to illustrate the sensitivity of the simulation to changes in various parameters.

scholarly journals Electromagnetic Sounding of Bottom Crevasses on the Ross Ice Shelf, Antarctica

1979 ◽  
Vol 24 (90) ◽  
pp. 321-330 ◽  
Author(s):  
Kenneth C. Jezek ◽  
Charles R. Bentley ◽  
John W. Clough
Keyword(s):  
Flow Direction ◽  
Ice Shelf ◽  
Electromagnetic Sounding ◽  
West Antarctic Ice Sheet ◽  
North West ◽  
Ross Ice Shelf ◽  
North East ◽  
West Antarctic ◽  
Ice Stream B ◽  
Folded Dipole

AbstractDuring the 1976—77 season of the Ross Ice Shelf Geophysical and Glaciological Survey, a series of vertical electromagnetic sounding profiles of subsurface features was completed at station J-9. The survey comprised three five-kilometer north-west-south-east profiles separated by one kilometer and six two-kilometer north-east-south-west profiles, and was carried out on the surface using 35 MHz and 50 MHz radar systems. Folded-dipole antennae were used and oriented to detect reflectors both along and perpendicular to the profile path. This was done to facilitate the interpretation of the data, which indicated a complex system of bottom crevasses. Measurements of the positions, heights, and shapes of these crevasses showed at least two sets of crevasses varying in both strike and size. The larger crevasses, about 120 m high and oriented more or less normal to the flow direction, are probably associated with the movement of ice stream B across the grounding line between the West Antarctic ice sheet and the Ross Ice Shelf. A satisfactory explanation for the secondary set of crevasses, about 60 m high and forming an angle of 60° ±10° with the first set, has not yet been found.

scholarly journals Modeling the effect of Ross Ice Shelf melting on the Southern Ocean in quasi-equilibrium

2018 ◽  
Vol 12 (9) ◽  
pp. 3033-3044 ◽  
Author(s):  
Xiying Liu
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Ross Sea ◽  
Global Ocean ◽  
Freshwater Flux ◽  
Quasi Equilibrium ◽  
Ice Shelf ◽  
Sea Ice Concentration ◽  
Ross Ice Shelf ◽  
Ice Concentration

Abstract. To study the influence of basal melting of the Ross Ice Shelf (BMRIS) on the Southern Ocean (ocean southward of 35∘ S) in quasi-equilibrium, numerical experiments with and without the BMRIS effect were performed using a global ocean–sea ice–ice shelf coupled model. In both experiments, the model started from a state of quasi-equilibrium ocean and was integrated for 500 years forced by CORE (Coordinated Ocean-ice Reference Experiment) normal-year atmospheric fields. The simulation results of the last 100 years were analyzed. The melt rate averaged over the entire Ross Ice Shelf is 0.25 m a−1, which is associated with a freshwater flux of 3.15 mSv (1 mSv = 103 m3 s−1). The extra freshwater flux decreases the salinity in the region from 1500 m depth to the sea floor in the southern Pacific and Indian oceans, with a maximum difference of nearly 0.005 PSU in the Pacific Ocean. Conversely, the effect of concurrent heat flux is mainly confined to the middle depth layer (approximately 1500 to 3000 m). The decreased density due to the BMRIS effect, together with the influence of ocean topography, creates local differences in circulation in the Ross Sea and nearby waters. Through advection by the Antarctic Circumpolar Current, the flux difference from BMRIS gives rise to an increase of sea ice thickness and sea ice concentration in the Ross Sea adjacent to the coast and ocean water to the east. Warm advection and accumulation of warm water associated with differences in local circulation decrease sea ice concentration on the margins of sea ice cover adjacent to open water in the Ross Sea in September. The decreased water density weakens the subpolar cell as well as the lower cell in the global residual meridional overturning circulation (MOC). Moreover, we observe accompanying reduced southward meridional heat transport at most latitudes of the Southern Ocean.

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