Development of the Circum-Antarctic Current

Kennett, James P.; Houtz, Robert E.; Andrews, Peter B.; Edwards, Anthony; Gostin, Victor A.; Hajos, M.; Hampton, Monty A.; Jenkins, D. Graham; Margolis, Stanley V.; Ovenshine, A.T.; Perch-Nielsen, K.

doi:10.1126/science.186.4159.144

Cited by 109 publications

(41 citation statements)

References 11 publications

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“…It is well known that the Antarctic circulation began during the Eocene (Margolis and Kennett, 1970;Kennett, Houtz, et al, 1974;Schackleton and Kennett, 1975 a,b) and that the Antarctic bottom water circulation was definitely established in the western South Atlantic during the Oligocene (Perch-Nielsen, Supko, et al, 1975;LePichon et al, 1976). During the Neogene, the Antarctic bottom water …”

Section: A Tentative Ccd Curve For the South Atlantic Since The Cretamentioning

confidence: 99%

Facies Evolution, Carbonate Dissolution Cycles in Sediments from the Eastern South Atlantic (DSDP Leg 40) Since the Early Cretaceous

Melguen¹

1978

Initial Reports of the Deep Sea Drilling Project

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Section: A Tentative Ccd Curve For the South Atlantic Since The Cretamentioning

confidence: 99%

Facies Evolution, Carbonate Dissolution Cycles in Sediments from the Eastern South Atlantic (DSDP Leg 40) Since the Early Cretaceous

Melguen¹

1978

Initial Reports of the Deep Sea Drilling Project

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“…Closed Southern Ocean gateways (i.e., Drake Passage and the Tasmanian Gateway) obstructed the formation of an isolating circumpolar surface current: the Antarctic Circumpolar Current (ACC) and associated coastal currents. In the absence of the isolating ACC, warm, low latitude-derived currents were thought to have bathed the Antarctic continent (5). Southern Ocean SSTs were characterized by a marked, gradual cooling starting in the latest early Eocene (∼49.5 Ma) (2-4), which culminated in the onset of large-scale glaciation of Antarctica at 34 Ma (7,8).…”

mentioning

confidence: 99%

“…Both lines of evidence indicate remarkably warm climate conditions for the highest southern latitudes during peak Cenozoic greenhouse conditions. Early hypotheses explaining the Eocene warmth at high latitudes invoked a pivotal role of ocean surface currents that, subject to a continental configuration fundamentally different from today, facilitated an increased heat transport to the Antarctic coastline (5,6). Closed Southern Ocean gateways (i.e., Drake Passage and the Tasmanian Gateway) obstructed the formation of an isolating circumpolar surface current: the Antarctic Circumpolar Current (ACC) and associated coastal currents.…”

mentioning

confidence: 99%

Eocene cooling linked to early flow across the Tasmanian Gateway

Bijl

Bendle

Bohaty

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

266

337

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The warmest global temperatures of the past 85 million years occurred during a prolonged greenhouse episode known as the Early Eocene Climatic Optimum (52–50 Ma). The Early Eocene Climatic Optimum terminated with a long-term cooling trend that culminated in continental-scale glaciation of Antarctica from 34 Ma onward. Whereas early studies attributed the Eocene transition from greenhouse to icehouse climates to the tectonic opening of Southern Ocean gateways, more recent investigations invoked a dominant role of declining atmospheric greenhouse gas concentrations (e.g., CO 2 ). However, the scarcity of field data has prevented empirical evaluation of these hypotheses. We present marine microfossil and organic geochemical records spanning the early-to-middle Eocene transition from the Wilkes Land Margin, East Antarctica. Dinoflagellate biogeography and sea surface temperature paleothermometry reveal that the earliest throughflow of a westbound Antarctic Counter Current began ∼49–50 Ma through a southern opening of the Tasmanian Gateway. This early opening occurs in conjunction with the simultaneous onset of regional surface water and continental cooling (2–4 °C), evidenced by biomarker- and pollen-based paleothermometry. We interpret that the westbound flowing current flow across the Tasmanian Gateway resulted in cooling of Antarctic surface waters and coasts, which was conveyed to global intermediate waters through invigorated deep convection in southern high latitudes. Although atmospheric CO 2 forcing alone would provide a more uniform middle Eocene cooling, the opening of the Tasmanian Gateway better explains Southern Ocean surface water and global deep ocean cooling in the apparent absence of (sub-) equatorial cooling.

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“…Nevertheless, clockwise subpolar gyres in the South Atlantic and Pacific oceans are postulated to have existed in the absence of circumpolar circulation (Haq, 1981). In the late Eocene, the subsidence of the South Tasman Rise allowed at least surface water communication between the Indian and Pacific oceans (Kennett et al, 1974). Although the Drake Passage was still closed, the subsidence of the Rise enhanced the development of circumpolar circulation sufficiently to cool subantarctic and antarctic sur-face and bottom waters.…”

Section: Significance Of the Eocene-oligocene Cooling Eventmentioning

confidence: 99%

“…This would lower the average isotopic composition of today's oceans from -0.28% 0 to approximately -1.2% 0 relative to PDB. The value -1.2%o should be used as δ w in the paleotemperature equation for all samples older than middle Miocene, because it was during the middle Miocene that a substantial Antarctic ice cap developed (Shackleton and Kennett, 1975;Savin et al, 1975;Kennett et al, 1974).…”

Section: Isotopic Paleotemperature Estimatesmentioning

confidence: 99%

Paleogene Oxygen Record for Deep Sea Drilling Project Sites 511 and 512, Subantarctic South Atlantic Ocean: Paleotemperatures, Paleoceanographic Changes, and the Eocene/Oligocene Boundary Event

Muza¹,

Williams²,

Wise³

1983

Initial Reports of the Deep Sea Drilling Project

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An Eocene-Oligocene oxygen and carbon isotope history based on planktonic and benthic foraminifers from Deep Sea Drilling Project Leg 71 cores has been constructed for the Maurice Ewing Bank of the eastern Falkland Plateau, Southwest Atlantic Ocean. Specifically, the cores cover portions of the middle Eocene, upper Eocene, and lower Oligocene. Surface water isotopic temperatures postulated for the middle Eocene at Site 512 fluctuated within about four degrees but generally averaged about 9°C. Bottom isotopic temperatures at Site 512 (water depth, 1846 m) were generally a degree lower than surface water temperatures.Surface water isotopic temperatures at Site 511 initially averaged about 11 °C during the late Eocene, but dropped to an average of 7°C in the early Oligocene. Bottom isotopic temperatures at Site 511 (water depth, 2589 m) generally record temperatures between 12.5°C and 8°C, similar to the range in the surface water isotopic temperatures. During the early Oligocene, bottom isotopic temperatures dropped sharply and averaged about 2°C (very close to present-day values). Surface water temperature values also decreased to an average of about 7°C, therefore leading to a significant divergence between surface and bottom water isotopic temperatures during the early Oligocene. Comparisons among Southern Ocean DSDP Sites 511,512, and 277, and between these and other DSDP sites from central and northern latitudes (Sites 44, 167, 171, 292, 357, 398, 119, and 401) show that much of the Eocene was characterized by relatively warm temperatures until sometime in either the middle Eocene, late Eocene, or early Oligocene. At each site, conspicuous 18 O enrichments occur in both the benthic and planktonic foraminifers over a relatively short period of time. Although a general trend toward a climatic deterioration is evident, the density of data points among the various studies is still too sparse to determine either synchrony or time-transgression between the major isotopic events.A close correlation could be made between the Site 511 oxygen isotope temperature curve and paleoclimatic trends derived independently from radiolarian studies. The sharp temperature drop and the divergence between bottom and surface water temperatures during the early Oligocene apparently reflect a major expansion of the antarctic water mass. The migration of the boundary between the subantarctic and antarctic water masses over the site at this time would account in part for the sharp temperature changes. Sharp changes of this nature would not necessarily be noted in other geographic areas, particularly those to the north which have different Oceanographic regimes.

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Development of the Circum-Antarctic Current

Cited by 109 publications

References 11 publications

Facies Evolution, Carbonate Dissolution Cycles in Sediments from the Eastern South Atlantic (DSDP Leg 40) Since the Early Cretaceous

Facies Evolution, Carbonate Dissolution Cycles in Sediments from the Eastern South Atlantic (DSDP Leg 40) Since the Early Cretaceous

Eocene cooling linked to early flow across the Tasmanian Gateway

Paleogene Oxygen Record for Deep Sea Drilling Project Sites 511 and 512, Subantarctic South Atlantic Ocean: Paleotemperatures, Paleoceanographic Changes, and the Eocene/Oligocene Boundary Event

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