Comparison of Glacial and Interglacial Oceanographic Conditions in the South Atlantic from Variations in Calcium Carbonate and Radiolarian Distributionsc

1979 ◽  
Vol 12 (3) ◽  
pp. 396-408 ◽  
Author(s):  
Joseph J. Morley ◽  
James D. Hays
Keyword(s):  
Calcium Carbonate ◽  
Polar Front ◽  
South Atlantic ◽  
Antarctic Polar Front ◽  
The South ◽  
Temperature Changes ◽  
The Antarctic ◽  
The Last Glacial Maximum ◽  
Oceanographic Conditions ◽  
The Last Glacial

Temperature estimates produced by a radiolarian-based transfer function, factor distributions of radiolarian assemblages, and variations in calcium carbonate were used to reconstruct the oceanographic conditions in the South Atlantic during the last glacial maximum (18,000 yr B.P.). This study suggests that while the position of the Subtropical Convergence at 18,000 yr B.P. was very similar to its present position, the Antarctic Polar Front shifted northward 1° to 3° of latitude in the eastern South Atlantic and 3° to 5° of latitude in the western South Atlantic. The largest temperature changes occurred in the subantarctic region and along the eastern portion of the Subtropical Gyre.

A numerical study of the South Atlantic circulation at the Last Glacial Maximum

2007 ◽  
Vol 253 (3-4) ◽  
pp. 509-528 ◽  
Author(s):  
Gabriel Clauzet ◽  
Ilana Wainer ◽  
Alban Lazar ◽  
Esther Brady ◽  
Bette Otto-Bliesner
Keyword(s):  
Last Glacial Maximum ◽  
Numerical Study ◽  
South Atlantic ◽  
Glacial Maximum ◽  
The South ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Northward Migration of Antarctic Polar Front during the Quaternary: Planktic Foraminiferal Record from Southeast Indian Ocean

2021 ◽  
Vol 7 (1) ◽  
pp. 13-24
Author(s):  
Ashutosh Kumar Singh ◽  
Devesh K. Sinha
Keyword(s):  
Indian Ocean ◽  
Volume Expansion ◽  
Census Data ◽  
Cold Water ◽  
Species Group ◽  
Polar Front ◽  
Antarctic Polar Front ◽  
The South ◽  
Ice Volume ◽  
The Antarctic

The ODP Hole 763A is influenced by the northward-flowing cold West Australian Current (WAC) and Southward flowing warm Leeuwin Current (LC). LC is a branch of the South Equatorial Current (SEC), which brings relatively warmer waters from the tropical Pacific Ocean into the Indian Ocean via Indonesian Throughflow (ITF). The modern planktic foraminiferal fauna thrives along the western margin of Australia. It consists mainly of warm water assemblages brought by the LC. The present study provides planktic foraminiferal census data from ODP Hole 763A, influenced by the LC and WAC, to document the history of cold water influence at the site during the quaternary. The northward migration of the Antarctic Polar Front (APF) and resultant intensification of the cold West Australian Current have been inferred based on the dramatic increase in the relative abundance of temperate water species group Globoconella at Hole 763A situated in the low latitude region. The Quaternary planktic foraminiferal census data shows several episodes of invasion of Globoconella. These intervals of high abundance of Globoconella group have been attributed to the intensification of WAC, probably due to Antarctic ice volume expansion and resultant northward migration of the APF at 0.05 Ma, 0.2 Ma, 0.45 Ma, 0.7 Ma and 1.2 Ma. We have documented that the amplitude of fluctuations in cold/warm events has increased after the Mid-Pleistocene Transition (MPT). LC is a heat supplier to the higher latitudes, its weakening during such intervals might have contributed to the ice volume expansion over Antarctica. Thus, the study proposes that the Antarctic ice cap formation creates a positive feedback mechanism by lowering sea level, reduced strength of LC due to a decrease in ITF and less heat supply towards the South Pole. All these phenomena add to further cooling.

The diets and dietary segregation of sooty albatrosses (Phoebetria spp.) at subantarctic Marion Island

1995 ◽  
Vol 7 (1) ◽  
pp. 15-23 ◽  
Author(s):  
John Cooper ◽  
Norbert T.W. Klages
Keyword(s):  
Foraging Behaviour ◽  
Stomach Contents ◽  
Polar Front ◽  
Antarctic Polar Front ◽  
Marion Island ◽  
The South ◽  
The Antarctic

Subantarctic Marion Island is one of the few localities where the congeneric albatrosses Phoebetria fusca and P. palpebrata breed sympatrically. Chicks of both species at Marion Island were induced to regurgitate their stomach contents after being fed. Liquid formed over half the diet by mass. Cephalopods occurred most frequently in both species' diets. In terms of mass, cephalopods formed the larger part of the diet of sooty albatrosses, whereas fish was more important to light-mantled sooty albatrosses. Crustaceans and birds were also recorded for both species. Squid of the families Onychoteuthidae, Histioteuthidae, Chiroteuthidae and Cranchiidae occurred most abundantly in both species. Most squid taken by both albatrosses were of species known to float after death, suggesting that scavenging plays an important role in the species' foraging behaviour. Light-mantled sooty albatrosses consumed more squid restricted to the south of the Antarctic Polar Front than did sooty albatrosses, supporting a trend to latitudinal segregation of the two species while foraging.

scholarly journals The impacts of Meltwater Pulse-1A in the South Atlantic Ocean deep circulation since the Last Glacial Maximum

2013 ◽  
Vol 9 (6) ◽  
pp. 6375-6395 ◽  
Author(s):  
J. M. Marson ◽  
I. Wainer ◽  
Z. Liu ◽  
M. M. Mata
Keyword(s):  
Atlantic Ocean ◽  
Sea Level ◽  
Last Glacial Maximum ◽  
South Atlantic ◽  
Glacial Maximum ◽  
South Atlantic Ocean ◽  
The South ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. Since 21 000 yr ago, the oceans have received large amounts of freshwater in pulses coming from the melting ice sheets. A specific event, known as meltwater pulse 1A (MWP-1A), has been identified in sea-level and temperature proxy records as responsible for the increase of ~20 m in sea level in less than 500 yr. Although its origin and timing are still under discussion, MWP-1A seems to have had a significant impact on several components of the climatic system. The present work aims to elucidate these impacts on the water mass distribution of the South Atlantic Ocean through the analysis of a transient simulation of the climate evolution from the Last Glacial Maximum to Present Day using a state-of-art CGCM, the National Center for Atmospheric Research Community Climate System Model version 3 (NCAR CCSM3). Results show that the freshwater discharge associated with the timing of MWP-1A was crucial to establish the present thermohaline structure associated with the North Atlantic Deep Water, marking the transition between a shallower and a deeper Atlantic Meridional Overturning Circulation.

scholarly journals Linking glacial and future climates through an ensemble of GCM simulations

2007 ◽  
Vol 3 (1) ◽  
pp. 77-87 ◽  
Author(s):  
J. C. Hargreaves ◽  
A. Abe-Ouchi ◽  
J. D. Annan
Keyword(s):  
Climate Sensitivity ◽  
Atmospheric Carbon Dioxide ◽  
Future Research ◽  
Sea Ice Extent ◽  
Temperature Changes ◽  
Climate Forecasting ◽  
The Tropics ◽  
The Antarctic ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. In this paper we explore the relationships between the modelled climate of the Last Glacial Maximum (LGM) and that for doubled atmospheric carbon dioxide compared to the pre-industrial climate by analysing the output from an ensemble of runs from the MIROC3.2 GCM. Our results lend support to the idea in other recent work that the Antarctic is a useful place to look for historical data which can be used to validate models used for climate forecasting of future greenhouse gas induced climate changes, at local, regional and global scales. Good results may also be obtainable using tropical temperatures, particularly those over the ocean. While the greater area in the tropics makes them an attractive area for seeking data, polar amplification of temperature changes may mean that the Antarctic provides a clearer signal relative to the uncertainties in data and model results. Our result for Greenland is not so strong, possibly due to difficulties in accurately modelling the sea ice extent. The MIROC3.2 model shows an asymmetry in climate sensitivity calculated by decreasing rather than increasing the greenhouse gases, with 80% of the ensemble having a weaker cooling than warming. This asymmetry, if confirmed by other studies would mean that direct estimates of climate sensitivity from the LGM are likely to be underestimated by the order of half a degree. Our suspicion is, however, that this result may be highly model dependent. Analysis of the parameters varied in the model suggest the asymmetrical response may be linked to the ice in the clouds, which is therefore indicated as an important area for future research.

scholarly journals Meridional overturning circulation in the South Atlantic at the last glacial maximum

2006 ◽  
Vol 7 (10) ◽  
pp. n/a-n/a ◽  
Author(s):  
Jean Lynch-Stieglitz ◽  
William B. Curry ◽  
Delia W. Oppo ◽  
Ulysses S. Ninneman ◽  
Christopher D. Charles ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
South Atlantic ◽  
Glacial Maximum ◽  
Meridional Overturning Circulation ◽  
The South ◽  
Overturning Circulation ◽  
Last Glacial ◽  
Meridional Overturning ◽  
The Last Glacial Maximum ◽  
The Last Glacial

scholarly journals Linking glacial and future climates through an ensemble of GCM simulations

2006 ◽  
Vol 2 (5) ◽  
pp. 951-977 ◽  
Author(s):  
J. C. Hargreaves ◽  
A. Abe-Ouchi ◽  
J. D. Annan
Keyword(s):  
Climate Sensitivity ◽  
Atmospheric Carbon Dioxide ◽  
Future Research ◽  
Sea Ice Extent ◽  
Temperature Changes ◽  
Climate Forecasting ◽  
The Tropics ◽  
The Antarctic ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. In this paper we explore the relationships between the modelled climate of the Last Glacial Maximum (LGM) and that for doubled atmospheric carbon dioxide compared to the pre-industrial climate by analysing the output from an ensemble of runs from the MIROC3.2 GCM. Our results lend support to the idea in other recent work that the Antarctic is a useful place to look for historical data which can be used to validate models used for climate forecasting of future greenhouse gas induced climate changes, at local, regional and global scales. Good results may also be obtainable using tropical temperatures, particularly those over the ocean. While the greater area in the tropics makes them an attractive area for seeking data, polar amplification of temperature changes may mean that the Anatarctic provides a clearer signal relative to the uncertainties in data and model results. Our result for Greenland is not so strong, possibly due to difficulties in accurately modelling the sea ice extent. The MIROC3.2 model shows an asymmetry in climate sensitivity calculated by decreasing rather than increasing the greenhouse gases, with 80% of the ensemble having a weaker cooling than warming. This asymmetry, if confirmed by other studies would mean that direct estimates of climate sensitivity from the LGM are likely to be underestimated by the order of half a degree. Our suspicion is, however, that this result may be highly model dependent. Analysis of the parameters varied in the model suggest the asymmetrical response may be linked to the ice in the clouds, which is therefore indicated as an important area for future research.

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