scholarly journals Late Quaternary paleoenvironment of the Ross Sea continental shelf, Antarctica

1998 ◽  
Vol 27 ◽  
pp. 275-280 ◽  
Author(s):  
Akira Nishimura ◽  
Toru Nakasone ◽  
Chikara Hiramatsu ◽  
Manabu Tanahashi
Keyword(s):  
Organic Carbon ◽  
Marine Environment ◽  
Environmental Changes ◽  
Ross Sea ◽  
Late Quaternary ◽  
Sedimentary Environment ◽  
Sediment Cores ◽  
Ice Sheet ◽  
Ice Shelf ◽  
Accelerator Mass Spectrometer

Based on sedimenlological and micropaleontological work on three sediment cores collected at about 167° Ε in the western Ross Sea, Antarctica, and accelerator mass spectrometer l4C ages of organic carbon, we have reconstructed environmental changes in the area during the late Quaternary. Since 38 ka BP at latest, this area was a marine environment with low productivity. A grounded ice sheet advanced and loaded the sediments before about 30-25 ka BP. After 25 ka BP, the southernmost site (76°46'S) was covered by floating ice (shelf ice), preventing deposition of coarse terrigenous materials and maintaining a supply of diatom tests and organic carbon until 20 ka BP. The northernmost site (74°33'S) was in a marine environment with a moderate productivity influenced by shelf ice/ice sheet after about 20 ka BP. Since about 10 ka BP, a sedimentary environment similar to the present-day one has prevailed over this area.

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 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 Changes in climate, ocean and ice-sheet conditions in the Ross embayment, Antarctica, at 6 ka

1998 ◽  
Vol 27 ◽  
pp. 305-310 ◽  
Author(s):  
Eric J. Steig ◽  
Charles P. Hart ◽  
James W. C. White ◽  
Wendy L. Cunningham ◽  
Mathew D. Davis ◽  
...  
Keyword(s):  
Sea Ice ◽  
Late Holocene ◽  
Environmental Changes ◽  
Ross Sea ◽  
Ice Core ◽  
Sediment Cores ◽  
Methanesulfonic Acid ◽  
Ice Shelf ◽  
Radiocarbon Dates ◽  
Ice Shelves

Evidence from the Ross embayment, Antarctica, suggests an abrupt cooling and a concomitant increase in sea-ice cover at about 6000 BP (6 ka). Stable-isotope (δD) concentrations in the Taylor Dome ice core, at the western edge of the Ross embayment, decline rapidly after 6 ka, and continue to decline through the late Holocene. Methanesulfonic acid concentrations at Taylor Dome show opposite trends to δD Sediment cores from the western Ross Sea show a percentage minimum for the sea-ice diatom Fragilariopsis curta between 9 and 6 ka, whenTaylor Dome δD values are highest, followed by an increase through the late Holocene. Radiocarbon dates from raised beach deposits indicate that the retreat of ice shelves in the Ross embayment ceased at about 6 ka, coincident with the environmental changes inferred from the sediment and ice-core records. The similarity in timing suggests an important role for climate in controlling the evolution of ice-shelf margins following the end of the last glaciation.

scholarly journals Variation of carbon contents in eelgrass ( Zostera marina ) sediments implied from depth profiles

2019 ◽  
Vol 15 (6) ◽  
pp. 20180831 ◽  
Author(s):  
Theodor Kindeberg ◽  
Emilia Röhr ◽  
Per-Olav Moksnes ◽  
Christoffer Boström ◽  
Marianne Holmer
Keyword(s):  
Organic Carbon ◽  
Zostera Marina ◽  
Large Scale ◽  
Environmental Changes ◽  
Sediment Cores ◽  
Depth Profiles ◽  
Seagrass Meadows ◽  
Spatio Temporal ◽  
Organic Carbon Storage ◽  
Eelgrass Beds

Seagrass meadows are able to store significant amounts of organic carbon in their underlying sediment, but global estimates are uncertain partly owing to spatio-temporal heterogeneity between and within areas and species. In order to provide robust estimates, there is a need to better understand the fate of, and mechanisms behind, organic carbon storage. In this observational study, we analyse a suite of biotic and abiotic parameters in sediment cores from 47 different eelgrass ( Zostera marina ) beds spanning the distributional range of the Northern Hemisphere. Depth profiles of particulate organic carbon (POC) revealed three patterns of vertical distribution where POC either increased, decreased or showed no pattern with sediment depth. These categories exhibited distinct profiles of δ 13 C and C:N ratios, where high POC profiles had a proportionally larger storage of eelgrass-derived material whereas low POC profiles were dominated by phytoplanktonic and macroalgal material. However, high POC did not always translate into high carbon density. Nevertheless, this large-scale dataset provides evidence that the variability in organic matter source in response to natural and anthropogenic environmental changes affects the potential role of eelgrass beds as POC sinks, particularly where eelgrass decline is observed.

Late Quaternary Iceberg Rafting along the Antarctic Peninsula Continental Rise and in the Weddell and Scotia Seas

2001 ◽  
Vol 56 (3) ◽  
pp. 308-321 ◽  
Author(s):  
Colm Ó Cofaigh ◽  
Julian A. Dowdeswell ◽  
Carol J. Pudsey
Keyword(s):  
Antarctic Peninsula ◽  
Late Quaternary ◽  
Sediment Cores ◽  
Regional Scale ◽  
Ice Sheet ◽  
Glacial Cycles ◽  
Continental Rise ◽  
The North ◽  
Glacial Periods ◽  
The Antarctic

AbstractSediment cores from the continental rise west of the Antarctic Peninsula and the northern Weddell and Scotia Seas were investigated for their ice-rafted debris (IRD) content by lithofacies logging and counting of particles >0.2 cm from core x-radiographs. The objective of the study was to determine if there are iceberg-rafted units similar to the Heinrich layers of the North Atlantic that might record periodic, widespread catastrophic collapse of basins within the Antarctic Ice Sheet during the Quaternary. Cores from the Antarctic Peninsula margin contain prominent IRD-rich units, with maximum IRD concentrations in oxygen isotope stages 1, 5, and 7. However, the greater concentration of IRD in interglacial stages is the result of low sedimentation rates and current winnowing, rather than regional-scale episodes of increased iceberg rafting. This is also supported by markedly lower mass accumulation rates (MAR) during interglacial periods versus glacial periods. Furthermore, thinner IRD layers within isotope stages 2–4 and 6 cannot be correlated between individual cores along the margin. This implies that the ice sheet over the Antarctic Peninsula did not undergo widespread catastrophic collapse along its western margin during the late Quaternary (isotope stages 1–7). Sediment cores from the Weddell and Scotia Seas are characterized by low IRD concentrations throughout, and the IRD signal generally appears to be of limited regional significance with few strong peaks that can be correlated between cores. Tentatively, this argues against pervasive, rapid ice-sheet collapse around the Weddell embayment over the last few glacial cycles.

Multi-proxy analysis of Late Quaternary ODYSSEA Contourite Depositional System (Ross Sea, Antarctica) and the depositional record of contour current and cold, dense waters

2020 ◽  
Author(s):  
Michele Rebesco ◽  
Renata Giulia Lucchi ◽  
Andrea Caburlotto ◽  
Stefano Miserocchi ◽  
Leonardo Langone ◽  
...  
Keyword(s):  
Ross Sea ◽  
Late Quaternary ◽  
Ice Sheet ◽  
Current Strength ◽  
Global Ocean ◽  
General Assembly ◽  
Geophysical Research ◽  
Dense Water ◽  
Depositional System ◽  
Ice Sheet Dynamics

&lt;p&gt;The Ross Ice Shelf is the Antarctic region that over the last deglaciation experienced the greatest change in areal ice cover. Today, cold, dense and saline water masses (brines) produced in the Ross Sea polynya, flow from the shelf to the deep ocean providing a significant contribution to the propelling of the global ocean circulation regulating the climate. In particular, the Hillary Canyon in the Eastern Ross Sea is the main conduit through which brines descend the slope to reach the deeper ocean and is thus one of the greatest regions of cold, dense water export in the world.&lt;/p&gt;&lt;p&gt;A Contourite Depositional System (the ODYSSEA CDS) on the western flank of the Hillary Canyon is inferred to have been generated through several hundred-thousand years by along-slope, contour currents that transported and accumulated the sediments brought down the Hillary Canyon by means of brines. A multi-proxy investigation was conducted on the shallowest part of the ODYSSEA CDS depositional sequences, which we expect to contain i) the record of the brine formation, ii) the indication on contour current strength through time, and iii) their interplay and modulation associated to climate change.&lt;/p&gt;&lt;p&gt;Six gravity cores, collected in both the proximal and distal area of the ODYSSEA CDS, were studied through multi-proxy analyses including sediment physical properties (texture, structures, water content, wet bulk density), compositional characteristics (XRF, geochemistry and detrital apatite, zircon, and rutile U-Pb on ice-rafted debris) (Lucchi et al., 2019; Neofitu et al., 2020) and microfossil content (planktonic and benthic foraminifera, calcareous nannofossils and diatoms). An age model has been reconstructed combining palaeomagnetic record, biostratigraphic content, tephrochronology and AMS radiocarbon dating on planktonic foraminifera tests.&lt;/p&gt;&lt;p&gt;Inferred variations in dense water formation, contour current strength and &lt;strong&gt;ice sheet dynamics &lt;/strong&gt;are discussed in the light of our data interpretation.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Lucchi, R.G., Caburlotto, A., Miserocchi, S., Liu, Y., Morigi, C., Persico, D., Villa, G., Langone, L., Colizza, E., Macr&amp;#236;, P., Sagnotti, L., Conte, R., Rebesco, M., 2019. The depositional record of the Odyssea drift (Ross Sea, Antarctica). Geophysical Research Abstracts, Vol. 21, EGU2019-10409-1, 2019. EGU General Assembly, Vienna (Austria), 7&amp;#8211;12, April, 2019 (POSTER).&lt;/p&gt;&lt;p&gt;Neofitu, R., Mark, C., Rebesco, M., Lucchi, R.G., Douss, N., Morigi, C., Kelley, S., Daly, J.S., 2020. Tracking Late Quaternary ice sheet dynamics by multi-proxy detrital mineral U-Pb analysis: A case study from the Odyssea contourite, Ross Sea, Antarctica. Geophysical Research Abstracts. EGU General Assembly, Vienna (Austria), 3&amp;#8211;8, May, 2020 (POSTER for session CL1.11).&lt;/p&gt;

Tracking Late Quaternary ice sheet dynamics by multi-proxy detrital mineral U-Pb analysis: A case study from the Odyssea contourite, Ross Sea, Antarctica

2020 ◽  
Author(s):  
Roland Neofitu ◽  
Chris Mark ◽  
Michele Rebesco ◽  
Renata Giulia Lucchi ◽  
Nessim Douss ◽  
...  
Keyword(s):  
Ross Sea ◽  
Late Quaternary ◽  
Ice Sheet ◽  
Source Area ◽  
Coarse Sand ◽  
Turbidity Currents ◽  
Provenance Analysis ◽  
Geophysical Research ◽  
Antarctic Ice Sheet ◽  
Volcanic Material

&lt;p&gt;Late Quaternary Antarctic ice-sheet instability is recorded by ice-rafted debris (IRD) in mid- to high-latitude marine sediment, especially during marine isotope stages (MIS) 2-3, but drivers of this instability remain enigmatic (Labeyrie et al., 1986). A key step in resolving this puzzle is to determine the location of iceberg calving sites, thus highlighting ice sheet sectors exhibiting repeated instability. Single-grain U-Pb provenance analysis applied to clastic IRD provides a suitable high-resolution tool for this task, and also permits discrimination of continental IRD from volcanic material. The application of multiple proxies (apatite, rutile, and zircon) is critical in order to reduce source area fertility biases: for example, the near exclusive occurrence of zircon in felsic-intermediate igneous rocks (e.g., Hietpas et al., 2010).&lt;/p&gt;&lt;p&gt;Here, we present detrital apatite, zircon, and rutile U-Pb data from samples taken from a gravity core from the Odyssea contourite drift system, located on the margin of the Ross Sea (Rebesco et al., 2018) and deposited during MIS2-3. Contourites are marine clastic sediment deposits forming by along-slope, bottom currents reworking of fine-grained (clay-silt) sediments delivered by down-slope sedimentary processes (e.g. meltwaters, turbidity currents, debris flows). Crucially, contourite targetting eliminates the challenge of distinguishing IRD from coarse (sand-gravel) turbidite material in basin deposits, as ice-sheet instability is also associated with turbidite production at glaciated shelf margins (e.g., Bart et al., 1999).&lt;/p&gt;&lt;p&gt;We couple our analysis with the multi-proxy sediment analyses previously performed by Lucchi et al. (2019). We consider the implications of our data for the advance and retreat of the Antarctic Ice Sheet during MIS 2-3, and discuss the further applicability of our multi-proxy approach around Antarctica.&lt;/p&gt;&lt;p&gt;Bart, P.J, et al., 1999, Journal of Sedimentary Research, v. 69, p. 1276&amp;#8211;1289, doi:10.2110/jsr.69.1276.&lt;/p&gt;&lt;p&gt;Hietpas, J, et al., 2010, Geology, v. 38, p. 167&amp;#8211;170, doi:10.1130/G30265.1.&lt;/p&gt;&lt;p&gt;Lucchi, R.G, et al., 2019. EGU General Assembly 2019, Vienna April 7&lt;sup&gt;th&lt;/sup&gt;&amp;#8211;12&lt;sup&gt;th&lt;/sup&gt;, Geophysical Research Abstracts Vol. 21, EGU2019-10409-1&lt;/p&gt;&lt;p&gt;Rebesco, M, et al., 2018, preliminary results, in POLAR 2018 SCAR/IASC Open Science Conference, v. GG2 Arctic, p. 14133.&lt;/p&gt;&lt;p&gt;Labeyrie, L, et al., 1986, Nature, v. 322, p. 701&amp;#8211;706.&lt;/p&gt;

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