Australodelphis mirus, a bizarre new toothless ziphiid-like fossil dolphin (Cetacea: Delphinidae) from the Pliocene of Vestfold Hills, East Antarctica

Australodelphis mirus (Delphinidae n. gen., n. sp) is a small extinct Early Pliocene dolphin known from five individuals from shallow-water strata of the Sørsdal Formation, Vestfold Hills, East Antarctica. Australodelphis mirus is the first higher vertebrate named from the Oligocene-Pleistocene interval on land in Antarctica, and is the first cetacean fossil from the polar margin of circum-Antarctic Southern Ocean that postdates the break-up of Gondwana. The dolphin is convergent in skull form with some living beaked whales (Mesoplodon spp.; Family Ziphiidae) in its long, narrow and toothless upper jaw and face, but skull suture patterns, basicranial sinuses, and ear-bones indicate close relationship with living long-beaked dolphins (Delphinidae). Australodelphis mirus perhaps was a suction-feeding squid-eater which occupied quiet near-shore shelf waters influenced by glaciers but probably lacking major sea-ice. Possible ecological equivalents of A. mirus (small ziphiids, long-beaked dolphins) do not occupy Antarctic waters today, perhaps excluded by cold conditions and/or sea-ice cover. Earlier Pliocene cetaceans worldwide reveal significant extinct and sometimes bizarre taxa, and extant families with ranges quite different from today, pointing to climate-related changes in cetacean ecology in the last 2–3 million years.

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Stratigraphy of Antarctic late Cenozoic pectinid-bearing deposits

Antarctic Science ◽

10.1017/s0954102098000212 ◽

1998 ◽

Vol 10 (2) ◽

pp. 161-170 ◽

Cited By ~ 20

Author(s):

H.A. Jonkers

Keyword(s):

Southern Ocean ◽

Food Availability ◽

Habitat Loss ◽

Antarctic Peninsula ◽

East Antarctica ◽

Combined Effects ◽

Late Cenozoic ◽

Late Pliocene ◽

Antarctic Waters ◽

The Antarctic

Antarctic late Cenozoic pectinid-bearing sedimentary strata are chiefly confined to localities in the northern part of the Antarctic Peninsula, in the McMurdo Sound area, and Marine Plain, East Antarctica. Ages of these deposits range from Oligocene to Holocene. Chlamys-like scallops, which are absent from today's Southern Ocean, thrived in Antarctic waters during both glacial and interglacial episodes, but disappeared during the Late Pliocene. Their extinction is believed to result from the combined effects of increased carbonate solubility, habitat loss and limitations in food availability, associated with major cooling.

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MONITORING OF THE NELLA FJORD WATER-ICE ECOSYSTEM (PRUDS BAY, EAST ANTARCTIC): SEASON RAE-65

Journal of Oceanological Research ◽

10.29006/1564-2291.jor-2020.48(2).10 ◽

2020 ◽

Vol 48 (2) ◽

pp. 163-165

Author(s):

I. A. Melnikov

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

East Antarctica ◽

Water Ice ◽

Project Assessment ◽

Antarctic Sea Ice ◽

Antarctic Expedition ◽

Russian Antarctic Expedition ◽

The Antarctic

During the seasonal work of the Russian Antarctic expedition (RAE-65), the monitoring of the water-ice ecological system was conducted in the Nella fjord (Prude Bay, East Antarctica). This monitoring is conducted annually since the IPY in 2007 in frames of the project “Assessment of the ecology of the Antarctic sea ice zone” (“Krial”) (Melnikov, 2020). The purpose of the monitoring is the assessment of the role of water-ice biota in global biosphere processes in the Southern Ocean.

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Highly branched isoprenoids as proxies for variable sea ice conditions in the Southern Ocean

Antarctic Science ◽

10.1017/s0954102011000381 ◽

2011 ◽

Vol 23 (5) ◽

pp. 487-498 ◽

Cited By ~ 55

Author(s):

Guillaume Massé ◽

Simon T. Belt ◽

Xavier Crosta ◽

Sabine Schmidt ◽

Ian Snape ◽

...

Keyword(s):

Organic Matter ◽

Southern Ocean ◽

Sea Ice ◽

Sediment Sample ◽

East Antarctica ◽

The Arctic ◽

Sediment Samples ◽

Isotopic Compositions ◽

Antarctic Sea Ice ◽

Ice Conditions

AbstractConcentrations of a highly branched isoprenoid (HBI) diene determined in over 200 sediment samples from the Arctic co-vary with those of an HBI monoene (IP25) shown previously to be a sedimentary sea ice proxy for the Arctic. The same diene, but not monoene IP25, occurred in nine sea ice samples collected from various locations around Antarctica. The diene has been reported previously in Antarctic sea ice diatoms and the 13C isotopic compositions of the diene determined in two Antarctic sea ice samples were also consistent with an origin from sea ice diatoms (δ13C -5.7 to -8.5‰). In contrast, HBIs found in two Antarctic phytoplankton samples did not include the diene but comprised a number of tri- to pentaenes. In sediment samples collected near Adélie Land, East Antarctica, both the diene and the tri- to pentaenes often co-occurred. 13C isotopic compositions of the tri- to pentaenes in three sediment samples ranged from -35 to -42‰ whereas that of the diene in a sediment sample was -18‰. We propose the presence of this isotopically 13C enriched HBI diene in Antarctic sediments to be a useful proxy indicator for contributions of organic matter derived from sea ice diatoms. A ratio of the concentrations of diene/trienes might reflect the relative contributions of sea ice to phytoplanktonic inputs of organic matter to Antarctic sediments.

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Population structure and long-term decline in three species of heart urchins Abatus spp. near-shore in the Vestfold Hills region, East Antarctica

Marine Ecology Progress Series ◽

10.3354/meps11573 ◽

2016 ◽

Vol 545 ◽

pp. 227-238 ◽

Cited By ~ 2

Author(s):

C Carrea ◽

CP Burridge ◽

CK King ◽

KJ Miller

Keyword(s):

Population Structure ◽

East Antarctica ◽

Near Shore ◽

Vestfold Hills

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Diversity and genomics of Antarctic marine micro-organisms

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2006.1944 ◽

2007 ◽

Vol 362 (1488) ◽

pp. 2259-2271 ◽

Cited By ~ 90

Author(s):

Alison E Murray ◽

Joseph J Grzymski

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Phytoplankton Bloom ◽

Vital Role ◽

Rrna Gene ◽

Culture Collections ◽

Cold Environments ◽

Group I ◽

Antarctic Waters ◽

Micro Organisms

Marine bacterioplanktons are thought to play a vital role in Southern Ocean ecology and ecosystem function, as they do in other ocean systems. However, our understanding of phylogenetic diversity, genome-enabled capabilities and specific adaptations to this persistently cold environment is limited. Bacterioplankton community composition shifts significantly over the annual cycle as sea ice melts and phytoplankton bloom. Microbial diversity in sea ice is better known than that of the plankton, where culture collections do not appear to represent organisms detected with molecular surveys. Broad phylogenetic groupings of Antarctic bacterioplankton such as the marine group I Crenarchaeota, α-Proteobacteria ( Roseobacter -related and SAR-11 clusters), γ-Proteobacteria (both cultivated and uncultivated groups) and Bacteriodetes-affiliated organisms in Southern Ocean waters are in common with other ocean systems. Antarctic SSU rRNA gene phylotypes are typically affiliated with other polar sequences. Some species such as Polaribacter irgensii and currently uncultivated γ-Proteobacteria (Ant4D3 and Ant10A4) may flourish in Antarctic waters, though further studies are needed to address diversity on a larger scale. Insights from initial genomics studies on both cultivated organisms and genomes accessed through shotgun cloning of environmental samples suggest that there are many unique features of these organisms that facilitate survival in high-latitude, persistently cold environments.

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Late Oligocene obliquity-paced contourite sedimentation in the Wilkes Land margin of East Antarctica: implications for paleoceanographic and ice sheet configurations

10.5194/cp-2017-152 ◽

2017 ◽

Cited By ~ 1

Author(s):

Ariadna Salabarnada ◽

Carlota Escutia ◽

Ursula Röhl ◽

C. Hans Nelson ◽

Robert McKay ◽

...

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Ross Sea ◽

Global Climate ◽

Ice Sheet ◽

East Antarctica ◽

Late Oligocene ◽

Early Oligocene ◽

Geochemical Parameters ◽

Wilkes Land

Abstract. The late Oligocene experienced atmospheric concentrations of CO2 between 400 and 750 ppm, which are within the IPCC projections for this century, assuming unabated CO2 emissions. However, Antarctic ice sheet and Southern Ocean paleoceanographic configurations during the late Oligocene are not well resolved, but are important to understand the influence of high-latitude Southern Hemisphere feedbacks on global climate under such CO2 scenarios. Here, we present late Oligocene (26–25 Ma) ice sheet and paleoceanographic reconstructions recorded in sediments recovered by IODP Site U1356, offshore of the Wilkes Land margin in East Antarctica. Our study, based on a combination of sediment facies analysis, physical properties, and geochemical parameters, shows that glacial and interglacial sediments are continuously reworked by bottom-currents, with maximum velocities occurring during the interglacial periods. Glacial sediments record poorly ventilated, low-oxygenation bottom water conditions, interpreted to represent a northward shift of westerly winds and surface oceanic fronts. During interglacial times, more oxygenated and ventilated conditions prevailed, which suggests enhanced mixing of the water masses with enhanced current velocities. Micritic limestone intervals within some of the interglacial facies represent warmer paleoclimatic conditions when less corrosive warmer northern component water (e.g. North Atlantic sourced deep water) had a greater influence on the site. The lack of iceberg rafted debris (IRD) throughout the studied interval contrasts with early Oligocene and post-Oligocene sections from Site U1356 and with late Oligocene strata from the Ross Sea (CRP and DSDP 270), which contain IRD and evidence for coastal sea ice and glaciers. These observations, supported by elevated paleotemperatures and the absence of sea-ice, suggest that between 26 and 25 Ma reduced glaciers or ice caps occupied the terrestrial lowlands of the Wilkes Land margin. Unlike today, the continental shelf was not over-deepened, and thus marine-based ice sheet expansion was likely limited to coastal regions. Combined, these data suggest that ice sheets in the Wilkes Subglacial Basin were largely land-based, and therefore retreated as a consequence of surface melt during late Oligocene, rather than direct ocean forcing and marine ice sheet instability processes as it did in younger past warm intervals. Spectral analysis on late Oligocene sediments from the eastern Wilkes Land margin show that the glacial-interglacial cyclicity and resulting displacements of the Southern Ocean frontal systems between 26–25 Ma were forced by obliquity.

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On the impact of sea ice in a global ocean circulation model

Annals of Glaciology ◽

10.3189/s0260305500013884 ◽

1997 ◽

Vol 25 ◽

pp. 111-115 ◽

Cited By ~ 3

Author(s):

Achim Stössel

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Ocean Circulation ◽

General Circulation ◽

Thermohaline Circulation ◽

Circulation Model ◽

Deep Ocean ◽

Global Ocean ◽

Convective Activity ◽

The Impact

This paper investigates the long-term impact of sea ice on global climate using a global sea-ice–ocean general circulation model (OGCM). The sea-ice component involves state-of-the-art dynamics; the ocean component consists of a 3.5° × 3.5° × 11 layer primitive-equation model. Depending on the physical description of sea ice, significant changes are detected in the convective activity, in the hydrographic properties and in the thermohaline circulation of the ocean model. Most of these changes originate in the Southern Ocean, emphasizing the crucial role of sea ice in this marginally stably stratified region of the world's oceans. Specifically, if the effect of brine release is neglected, the deep layers of the Southern Ocean warm up considerably; this is associated with a weakening of the Southern Hemisphere overturning cell. The removal of the commonly used “salinity enhancement” leads to a similar effect. The deep-ocean salinity is almost unaffected in both experiments. Introducing explicit new-ice thickness growth in partially ice-covered gridcells leads to a substantial increase in convective activity, especially in the Southern Ocean, with a concomitant significant cooling and salinification of the deep ocean. Possible mechanisms for the resulting interactions between sea-ice processes and deep-ocean characteristics are suggested.

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DASSO: a data assimilation system for the Southern Ocean that utilizes both sea-ice concentration and thickness observations

Journal of Glaciology ◽

10.1017/jog.2021.57 ◽

2021 ◽

pp. 1-6

Author(s):

Hao Luo ◽

Qinghua Yang ◽

Longjiang Mu ◽

Xiangshan Tian-Kunze ◽

Lars Nerger ◽

...

Keyword(s):

Data Assimilation ◽

Southern Ocean ◽

Sea Ice ◽

Coupled Model ◽

Sea Ice Concentration ◽

Model Free ◽

Antarctic Sea Ice ◽

Ice Concentration ◽

Data Assimilation System ◽

Assimilation System

Abstract To improve Antarctic sea-ice simulations and estimations, an ensemble-based Data Assimilation System for the Southern Ocean (DASSO) was developed based on a regional sea ice–ocean coupled model, which assimilates sea-ice thickness (SIT) together with sea-ice concentration (SIC) derived from satellites. To validate the performance of DASSO, experiments were conducted from 15 April to 14 October 2016. Generally, assimilating SIC and SIT can suppress the overestimation of sea ice in the model-free run. Besides considering uncertainties in the operational atmospheric forcing data, a covariance inflation procedure in data assimilation further improves the simulation of Antarctic sea ice, especially SIT. The results demonstrate the effectiveness of assimilating sea-ice observations in reconstructing the state of Antarctic sea ice, but also highlight the necessity of more reasonable error estimation for the background as well as the observation.

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