scholarly journals Evidence for the Antarctic circumpolar wave in the sub-Antarctic during the past 50 years

2005 ◽  
Vol 32 (14) ◽  
pp. n/a-n/a ◽  
Author(s):  
J.-L. Mélice ◽  
J. R. E. Lutjeharms ◽  
H. Goosse ◽  
T. Fichefet ◽  
C. J. C. Reason
Keyword(s):  
The Past ◽  
Antarctic Circumpolar Wave ◽  
The Antarctic

scholarly journals Whales as Indicators of Historical and Current Changes in the Marine Ecosystem of the Indo-Pacific Sector of the Antarctic

2020 ◽  
Author(s):  
Yoshihiro Fujise ◽  
Luis A. Pastene
Keyword(s):  
Marine Ecosystem ◽  
Recruitment Rate ◽  
Minke Whale ◽  
Past Century ◽  
Baleen Whale ◽  
The Past ◽  
Antarctic Minke Whale ◽  
Minke Whales ◽  
Nutritional Conditions ◽  
The Antarctic

We review the scientific information on whales that could be indicative of historical and current changes in the ecosystem in the Indo-Pacific sector of the Antarctic. The increased krill availability in the middle of the past century as a result of the heavy harvesting of the larger baleen whale species could have been translated into better nutritional conditions for the Antarctic minke whale, resulting in a decreasing trend in the age at sexual maturity and an increasing trend in recruitment rate and hence total population size between approximately 1940 and 1970. This nutritional condition has deteriorated more recently, as revealed by a decrease in energy storage and stomach content weight since the 1980’s; these changes coincide with appreciable increases in the abundances of humpback and fin whales, which were heavily harvested in the first half of the past century. The historical demographic changes observed in the Antarctic minke whale are consistent with the pattern to be expected under the krill surplus hypothesis, with minke whales now again competing with other (recovering) baleen whale species for krill. However, these minke whales could also be using alternative feeding areas (e.g. polynias within the pack-ice) in response to the increase in abundance and geographical expansion of these other large whale species. This could provide an alternative explanation for indications from sighting surveys and population models of a decrease and then re-stabilisation of minke whale abundance in open water areas since the 1970s.

L’Antartide è veramente un "awful place"? I caratteri ambientali del continente più freddo della Terra

2012 ◽  
pp. 29-46
Author(s):  
Claudio Smiraglia
Keyword(s):  
Indigenous Population ◽  
Terrestrial Ecosystems ◽  
South Pole ◽  
The Past ◽  
Unique Information ◽  
The World ◽  
Antarctic Continent ◽  
Harsh Climate ◽  
The Many ◽  
The Antarctic

The Antarctic continent is certainly made an "awful" place by its harsh climate: in the past, explorers and researchers endured terrible hardships and the climate remains a challenge today, in spite of the many improvements in knowledge and technology. The Antarctic may be termed "the continent of the extremes", as it occupies an area unlike any other on earth. It is the farthest and most inaccessible and isolated continent; the most regular because of its rounded shape, with the South Pole at the centre; the coldest continent, with temperatures falling to -90°C; the driest (with an average of 130 mm of precipitation); the windiest, the highest, the most glacialized (it contains 91% of the volume of the earth’s ice). It also displays the most monotonous landscapes and presents the greatest contrast between marine and terrestrial ecosystems. But the Antarctic is also "extreme" because it is the least populated continent, with no indigenous population at all, while its few settlements (consisting in scientific bases) are concentrated on the coast; it is the only place that does not belong to one nation, but to all the world; it is the place where unique information on the past, present and future of humankind is revealed.

Cryosphere

2004 ◽  
Author(s):  
Kenneth M. Hinkel ◽  
Andrew W. Ellis
Keyword(s):  
Sea Ice ◽  
Snow Cover ◽  
Global Climate ◽  
Ice Sheets ◽  
Past Century ◽  
High Latitudes ◽  
Ice Shelves ◽  
The Past ◽  
Third Assessment Report ◽  
The Antarctic

The cryosphere refers to the Earth’s frozen realm. As such, it includes the 10 percent of the terrestrial surface covered by ice sheets and glaciers, an additional 14 percent characterized by permafrost and/or periglacial processes, and those regions affected by ephemeral and permanent snow cover and sea ice. Although glaciers and permafrost are confined to high latitudes or altitudes, areas seasonally affected by snow cover and sea ice occupy a large portion of Earth’s surface area and have strong spatiotemporal characteristics. Considerable scientific attention has focused on the cryosphere in the past decade. Results from 2 ×CO2 General Circulation Models (GCMs) consistently predict enhanced warming at high latitudes, especially over land (Fitzharris 1996). Since a large volume of ground and surface ice is currently within several degrees of its melting temperature, the cryospheric system is particularly vulnerable to the effects of regional warming. The Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) states that there is strong evidence of Arctic air temperature warming over land by as much as 5 °C during the past century (Anisimov et al. 2001). Further, sea-ice extent and thickness has recently decreased, permafrost has generally warmed, spring snow extent over Eurasia has been reduced, and there has been a general warming trend in the Antarctic (e.g. Serreze et al. 2000). Most climate models project a sustained warming and increase in precipitation in these regions over the twenty-first century. Projected impacts include melting of ice sheets and glaciers with consequent increase in sea level, possible collapse of the Antarctic ice shelves, substantial loss of Arctic Ocean sea ice, and thawing of permafrost terrain. Such rapid responses would likely have a substantial impact on marine and terrestrial biota, with attendant disruption of indigenous human communities and infrastructure. Further, such changes can trigger positive feedback effects that influence global climate. For example, melting of organic-rich permafrost and widespread decomposition of peatlands might enhance CO2 and CH4 efflux to the atmosphere. Cryospheric researchers are therefore involved in monitoring and documenting changes in an effort to separate the natural variability from that induced or enhanced by human activity.

scholarly journals Evaluation of the Antarctic Circumpolar Wave Simulated by CMIP5 and CMIP6 Models

Atmosphere ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 931
Author(s):  
Zhichao Lu ◽  
Tianbao Zhao ◽  
Weican Zhou
Keyword(s):  
Large Scale ◽  
Global Climate ◽  
Coupled Model ◽  
Cmip5 Models ◽  
Weather Forecasts ◽  
Antarctic Circumpolar Wave ◽  
Sst Variability ◽  
The Antarctic ◽  
Chemistry Module ◽  
Better Than

As a coupled large-scale oceanic and atmospheric pattern in the Southern Ocean, the Antarctic circumpolar wave (ACW) has substantial impacts on the global climate. In this study, using the European Centre for Medium-Range Weather Forecasts ERA5 dataset and historical experiment outputs from 24 models of the Coupled Model Intercomparison Project Phase 5 and Phase 6 (CMIP5/CMIP6) spanning the 1980s and 1990s, the simulation capability of models for sea-level pressure (SLP) and sea surface temperature (SST) variability of the ACW is evaluated. It is shown that most models can capture well the 50-month period of the ACW. However, many simulations show a weak amplitude, but with various phase differences. Selected models can simulate SLP better than SST, and CMIP6 models generally perform better than the CMIP5 models. The best model for SLP simulation is the CanESM5 model from CMIP6, whereas the best model for SST simulation is the ACCESS1.3 model from CMIP5. It seems that the SST simulation benefits from the inclusion of both a carbon cycle process and a chemistry module, while the SLP simulation benefits from only the chemistry module. When both SLP and SST are taken into consideration, the CanESM5 model performs the best among all the selected models.

scholarly journals The influence of ice sheets on temperature during the past 38 million years inferred from a one-dimensional ice sheet–climate model

2017 ◽  
Vol 13 (9) ◽  
pp. 1243-1257 ◽  
Author(s):  
Lennert B. Stap ◽  
Roderik S. W. van de Wal ◽  
Bas de Boer ◽  
Richard Bintanja ◽  
Lucas J. Lourens
Keyword(s):  
Climate Model ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Atmospheric Temperature ◽  
Temperature Changes ◽  
One Dimensional ◽  
Ice Volume ◽  
The Past ◽  
Polar Amplification ◽  
The Antarctic

Abstract. Since the inception of the Antarctic ice sheet at the Eocene–Oligocene transition (∼ 34 Myr ago), land ice has played a crucial role in Earth's climate. Through feedbacks in the climate system, land ice variability modifies atmospheric temperature changes induced by orbital, topographical, and greenhouse gas variations. Quantification of these feedbacks on long timescales has hitherto scarcely been undertaken. In this study, we use a zonally averaged energy balance climate model bidirectionally coupled to a one-dimensional ice sheet model, capturing the ice–albedo and surface–height–temperature feedbacks. Potentially important transient changes in topographic boundary conditions by tectonics and erosion are not taken into account but are briefly discussed. The relative simplicity of the coupled model allows us to perform integrations over the past 38 Myr in a fully transient fashion using a benthic oxygen isotope record as forcing to inversely simulate CO2. Firstly, we find that the results of the simulations over the past 5 Myr are dependent on whether the model run is started at 5 or 38 Myr ago. This is because the relation between CO2 and temperature is subject to hysteresis. When the climate cools from very high CO2 levels, as in the longer transient 38 Myr run, temperatures in the lower CO2 range of the past 5 Myr are higher than when the climate is initialised at low temperatures. Consequently, the modelled CO2 concentrations depend on the initial state. Taking the realistic warm initialisation into account, we come to a best estimate of CO2, temperature, ice-volume-equivalent sea level, and benthic δ18O over the past 38 Myr. Secondly, we study the influence of ice sheets on the evolution of global temperature and polar amplification by comparing runs with ice sheet–climate interaction switched on and off. By passing only albedo or surface height changes to the climate model, we can distinguish the separate effects of the ice–albedo and surface–height–temperature feedbacks. We find that ice volume variability has a strong enhancing effect on atmospheric temperature changes, particularly in the regions where the ice sheets are located. As a result, polar amplification in the Northern Hemisphere decreases towards warmer climates as there is little land ice left to melt. Conversely, decay of the Antarctic ice sheet increases polar amplification in the Southern Hemisphere in the high-CO2 regime. Our results also show that in cooler climates than the pre-industrial, the ice–albedo feedback predominates the surface–height–temperature feedback, while in warmer climates they are more equal in strength.

scholarly journals Characteristics of ice rises and ice rumples in Dronning Maud Land and Enderby Land, Antarctica

2020 ◽  
Vol 66 (260) ◽  
pp. 1064-1078
Author(s):  
Vikram Goel ◽  
Kenichi Matsuoka ◽  
Cesar Deschamps Berger ◽  
Ian Lee ◽  
Jørgen Dall ◽  
...  
Keyword(s):  
Mass Balance ◽  
Ice Cores ◽  
Ice Thickness ◽  
Ice Shelf ◽  
Ice Dynamics ◽  
Surface Mass ◽  
Ice Shelves ◽  
The Past ◽  
Dronning Maud Land ◽  
The Antarctic

AbstractIce rises and rumples, locally grounded features adjacent to ice shelves, are relatively small yet play significant roles in Antarctic ice dynamics. Their roles generally depend upon their location within the ice shelf and the stage of the ice-sheet retreat or advance. Large, long-stable ice rises can be excellent sites for deep ice coring and paleoclimate study of the Antarctic coast and the Southern Ocean, while small ice rises tend to respond more promptly and can be used to reveal recent changes in regional mass balance. The coasts of Dronning Maud Land (DML) and Enderby Land in East Antarctica are abundant with these features. Here we review existing knowledge, presenting an up-to-date status of research in these regions with focus on ice rises and rumples. We use regional datasets (satellite imagery, surface mass balance and ice thickness) to analyze the extent and surface morphology of ice shelves and characteristic timescales of ice rises. We find that large parts of DML have been changing over the past several millennia. Based on our findings, we highlight ice rises suitable for drilling ice cores for paleoclimate studies as well as ice rises suitable for deciphering ice dynamics and evolution in the region.

Reproductive aspects of female crabeater seals (Lobodon carcinophagus) along the Antarctic Peninsula

1981 ◽  
Vol 59 (1) ◽  
pp. 92-102 ◽  
Author(s):  
John L. Bengtson ◽  
Donald B. Siniff
Keyword(s):  
Antarctic Peninsula ◽  
Reproductive Performance ◽  
Sexual Maturity ◽  
Marine Ecosystem ◽  
Geographical Differences ◽  
The Past ◽  
Antarctic Marine ◽  
Crabeater Seals ◽  
Lobodon Carcinophagus ◽  
The Antarctic

Examination of a sample of 94 female crabeater seals collected in November, 1977, indicated that, for the past 7 years, the average age at sexual maturity was 3.8 years. Reproductive performance as evidenced by uterine scars and ovarian corpora is discussed. No females inseminated at age 4 or less successfully carried a fetus full term. Timing of ovulation was affected by both age and social category. Younger seals ovulate later in the season than older seals. No females ovulated prior to weaning their pups. Ovulation in experienced females occurred sometimes while still in a mated pair, but mostly at or after dissolution of the pair bond. Comparison of recent age of sexual maturity with earlier reports shows an increase in this age since 1967. This trend may reflect geographical differences or changes in the Antarctic marine ecosystem following a slowdown in Antarctic whaling.

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