Water Column Stratification in the Antarctic Zone of the Southern Ocean During the Mid-Pleistocene Climate Transition

2018 ◽  
Vol 33 (5) ◽  
pp. 432-442 ◽  
Author(s):  
Katharina Billups ◽  
Kelsee York ◽  
Louisa I. Bradtmiller
2012 ◽  
Vol 345-348 ◽  
pp. 194-202 ◽  
Author(s):  
Laura Rodríguez-Sanz ◽  
P. Graham Mortyn ◽  
Alfredo Martínez-Garcia ◽  
Antoni Rosell-Melé ◽  
Ian R. Hall

2021 ◽  
Author(s):  
Eivind Straume ◽  
Aleksi Nummelin ◽  
Carmen Gaina ◽  
Kerim Nisancioglu

<p>The Eocene – Oligocene Transition (~33.7 million years ago), marks the largest step transformation within the Cenozoic cooling trend, and is characterized by a sudden growth of the Antarctic ice sheets. The role of changes in oceanic basin configuration and the evolution of key oceanic gateways in triggering these climatic variations remains disputed. Here we implement a new state-of-the-art paleogeography model in the Norwegian Earth System Model (NorESM-F) to investigate the effect of oceanic gateway changes on the Eocene – Oligocene climate. We run different cases using realistic max/min depth configurations of the Atlantic – Arctic oceanic gateways, the Tethys Seaway, and the Southern Ocean gateways, and investigate the ocean and climate sensitivity to these changes. In addition, we run separate simulations investigating the impact on the carbon cycle. The models show that changes in the Atlantic – Arctic gateways (i.e. Greenland – Scotland Ridge and the Fram Strait) cause the most significant changes in ocean circulation and climate compared to the Southern Ocean gateways or the Tehthys Seaway. The Iceland mantle plume caused depth variations on the Greenland – Scotland Ridge at this time, and our model result indicate that variations in dynamic support from the Iceland plume could have played a key role in the Eocene – Oligocene climate transition. Essentially, reduced dynamic support from the plume deepen the Greenland – Scotland Ridge and cause freshwater leakage from the Arctic Ocean which inhibits deep water formation in the North Atlantic, reducing the AMOC and ultimately cool the Northern Hemisphere.</p>


Formidable legal and administrative complexities arise from conflicting claims to jurisdiction and the continued absence of generally recognized sovereignty over much of the region. Existing conservation measures fall into three groups: elaborate laws made by governments claiming Antarctic territories, more restricted laws, and simple instructions for particular expeditions. The Antarctic Treaty, 1959, made it possible to begin coordinating all these separate instruments. No claimed jurisdiction has been surrendered or recognized: each government has started to harmonize its own control measures with the ‘Agreed Measures for the Conservation of Antarctic Fauna and Flora’, 1964. This scheme applied only to land areas and has since been evolving in the light of experience. Although not yet formally approved by all the governments concerned, it is working effectively by voluntary agreement. Different approaches are necessary for conservation of Southern Ocean resources, especially krill. A start has been made with the ‘ Convention for the Conservation of Antarctic Seals’, 1972. There are many outstanding problems: all require effective cooperation between scientific and legal advisers, diplomats and politicians. Mention is made of recent British conservation legislation for South Georgia, the Falkland Islands and the Tristan da Cunha group. Some of the next steps are outlined.


1996 ◽  
Vol 74 (8) ◽  
pp. 1485-1496 ◽  
Author(s):  
B. J. McConnell ◽  
M. A. Fedak

Twelve southern elephant seals (Mirounga leonina) were tracked for an average of 119 days as they left their breeding or moulting beaches on the island of South Georgia between 1990 and 1994. Females travelled either eastward up to 3000 km away to the open Southern Ocean or to the continental shelf on or near the Antarctic Peninsula. Males either stayed close to South Georgia or used South Georgia as a base for shorter trips. The females all left South Georgia in a directed manner at an average rate of 79.4 km/day over at least the first 15 days. Thereafter travel was interrupted by bouts of slower travel or stationary phases. The latter were localized at sites on the continental shelf or along its edge. Three seals that were tracked over more than one season repeated their outward direction of travel and used some of the same sites in subsequent years. The magnitude of the movements makes most of the Southern Ocean potentially available to elephant seals.


2017 ◽  
Vol 3 (4) ◽  
pp. 316-329 ◽  
Author(s):  
Xylar S. Asay-Davis ◽  
Nicolas C. Jourdain ◽  
Yoshihiro Nakayama

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