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1. Five million years of Antarctic Circumpolar Current strength variability

Author

Lamy, F, Winckler, G, Arz, H, Farmer, J, Gottschalk, J, Lembke-Jene, L, Middleton, J, van der Does, M, Tiedemann, R, Alvarez Zarikian, C, Basak, C, Brombacher, A, Dumm, L, Esper, O, Herbert, L, Iwasaki, S, Kreps, G, Lawson, V, Lo, L, Malinverno, E, Martinez-Garcia, A, Michel, E, Moretti, S, Moy, C, Ravelo, A, Riesselman, C, Saavedra-Pellitero, M, Sadatzki, H, Seo, I, Singh, R, Smith, R, Souza, A, Stoner, J, Toyos, M, de Oliveira, I, Wan, S, Wu, S, Zhao, X, Lamy F., Winckler G., Arz H. W., Farmer J. R., Gottschalk J., Lembke-Jene L., Middleton J. L., van der Does M., Tiedemann R., Alvarez Zarikian C., Basak C., Brombacher A., Dumm L., Esper O. M., Herbert L. C., Iwasaki S., Kreps G., Lawson V. J., Lo L., Malinverno E., Martinez-Garcia A., Michel E., Moretti S., Moy C. M., Ravelo A. C., Riesselman C. R., Saavedra-Pellitero M., Sadatzki H., Seo I., Singh R. K., Smith R. A., Souza A. L., Stoner J. S., Toyos M., de Oliveira I. M. V. P., Wan S., Wu S., Zhao X., Lamy, F, Winckler, G, Arz, H, Farmer, J, Gottschalk, J, Lembke-Jene, L, Middleton, J, van der Does, M, Tiedemann, R, Alvarez Zarikian, C, Basak, C, Brombacher, A, Dumm, L, Esper, O, Herbert, L, Iwasaki, S, Kreps, G, Lawson, V, Lo, L, Malinverno, E, Martinez-Garcia, A, Michel, E, Moretti, S, Moy, C, Ravelo, A, Riesselman, C, Saavedra-Pellitero, M, Sadatzki, H, Seo, I, Singh, R, Smith, R, Souza, A, Stoner, J, Toyos, M, de Oliveira, I, Wan, S, Wu, S, Zhao, X, Lamy F., Winckler G., Arz H. W., Farmer J. R., Gottschalk J., Lembke-Jene L., Middleton J. L., van der Does M., Tiedemann R., Alvarez Zarikian C., Basak C., Brombacher A., Dumm L., Esper O. M., Herbert L. C., Iwasaki S., Kreps G., Lawson V. J., Lo L., Malinverno E., Martinez-Garcia A., Michel E., Moretti S., Moy C. M., Ravelo A. C., Riesselman C. R., Saavedra-Pellitero M., Sadatzki H., Seo I., Singh R. K., Smith R. A., Souza A. L., Stoner J. S., Toyos M., de Oliveira I. M. V. P., Wan S., Wu S., and Zhao X.

Abstract

The Antarctic Circumpolar Current (ACC) represents the world’s largest ocean-current system and affects global ocean circulation, climate and Antarctic ice-sheet stability1–3. Today, ACC dynamics are controlled by atmospheric forcing, oceanic density gradients and eddy activity4. Whereas palaeoceanographic reconstructions exhibit regional heterogeneity in ACC position and strength over Pleistocene glacial–interglacial cycles5–8, the long-term evolution of the ACC is poorly known. Here we document changes in ACC strength from sediment cores in the Pacific Southern Ocean. We find no linear long-term trend in ACC flow since 5.3 million years ago (Ma), in contrast to global cooling9 and increasing global ice volume10. Instead, we observe a reversal on a million-year timescale, from increasing ACC strength during Pliocene global cooling to a subsequent decrease with further Early Pleistocene cooling. This shift in the ACC regime coincided with a Southern Ocean reconfiguration that altered the sensitivity of the ACC to atmospheric and oceanic forcings11–13. We find ACC strength changes to be closely linked to 400,000-year eccentricity cycles, probably originating from modulation of precessional changes in the South Pacific jet stream linked to tropical Pacific temperature variability14. A persistent link between weaker ACC flow, equatorward-shifted opal deposition and reduced atmospheric CO2 during glacial periods first emerged during the Mid-Pleistocene Transition (MPT). The strongest ACC flow occurred during warmer-than-present intervals of the Plio-Pleistocene, providing evidence of potentially increasing ACC flow with future climate warming.

Published
2024

2. Expedition 383 summary

Author

Lamy, F., Winckler, G., Alvarez Zarikian, C.A., and the Expedition 383 Scientists, Winckler, G, Lamy, F, Alvarez Zarikian, C, Arz, H, Basak, C, Brombacher, A, Esper, O, Farmer, J, Gottschalk, J, Herbert, L, Iwasaki, S, Lawson, V, Lembke-Jene, L, Lo, L, Malinverno, E, Michel, E, Middleton, J, Moretti, S, Moy, C, Ravelo, A, Riesselman, C, Saavedra-Pellitero, M, Seo, I, Singh, R, Smith, R, Souza, A, Stoner, J, Venancio, I, Wan, S, Zhao, X, Foucher McColl, N, Winckler, G., Lamy, F., Alvarez Zarikian, C. A., Arz, H. W., Basak, C., Brombacher, A., Esper, O. M., Farmer, J. R., Gottschalk, J., Herbert, L. C., Iwasaki, S., Lawson, V. J., Lembke-Jene, L., Lo, L., Malinverno, E., Michel, E., Middleton, J. L., Moretti, S., Moy, C. M., Ravelo, A. C., Riesselman, C. R., Saavedra-Pellitero, M., Seo, I., Singh, R. K., Smith, R. A., Souza, A. L., Stoner, J. S., Venancio, I. M., Wan, S., Zhao, X., Foucher McColl, N., Lamy, F., Winckler, G., Alvarez Zarikian, C.A., and the Expedition 383 Scientists, Winckler, G, Lamy, F, Alvarez Zarikian, C, Arz, H, Basak, C, Brombacher, A, Esper, O, Farmer, J, Gottschalk, J, Herbert, L, Iwasaki, S, Lawson, V, Lembke-Jene, L, Lo, L, Malinverno, E, Michel, E, Middleton, J, Moretti, S, Moy, C, Ravelo, A, Riesselman, C, Saavedra-Pellitero, M, Seo, I, Singh, R, Smith, R, Souza, A, Stoner, J, Venancio, I, Wan, S, Zhao, X, Foucher McColl, N, Winckler, G., Lamy, F., Alvarez Zarikian, C. A., Arz, H. W., Basak, C., Brombacher, A., Esper, O. M., Farmer, J. R., Gottschalk, J., Herbert, L. C., Iwasaki, S., Lawson, V. J., Lembke-Jene, L., Lo, L., Malinverno, E., Michel, E., Middleton, J. L., Moretti, S., Moy, C. M., Ravelo, A. C., Riesselman, C. R., Saavedra-Pellitero, M., Seo, I., Singh, R. K., Smith, R. A., Souza, A. L., Stoner, J. S., Venancio, I. M., Wan, S., Zhao, X., and Foucher McColl, N.

Abstract

The Antarctic Circumpolar Current (ACC), the world’s strongest zonal current system, connects all three major ocean basins of the global ocean and therefore integrates and responds to global climate variability. Its flow is largely driven by strong westerly winds and is constricted to its narrowest extent in the Drake Passage. Fresh and cold Pacific surface and intermediate water flowing through the Drake Passage (cold-water route) and warm Indian Ocean water masses flowing through the Agulhas region (warm-water route) are critical for the South Atlantic contribution to Meridional Overturning Circulation changes. Furthermore, physical and biological processes associated with the ACC affect the strength of the ocean carbon pump and therefore are critical to feedbacks linking atmospheric CO2 concentrations, ocean circulation, and climate/cryosphere on a global scale. In contrast to the Atlantic and Indian sectors of the ACC, and with the exception of drill cores from the Antarctic continental margin and off New Zealand, there are no deep-sea drilling paleoceanographic records from the Pacific sector of the ACC. To advance our understanding of Miocene to Holocene atmosphere-ocean-cryosphere dynamics in the Pacific and their implications for regional and global climate and atmospheric CO2, International Ocean Discovery Program Expedition 383 recovered sedimentary sequences at (1) three sites in the central South Pacific (CSP) (U1539, U1540, and U1541), (2) two sites at the Chilean margin (U1542 and U1544), and (3) one site from the pelagic eastern South Pacific (U1543) close to the entrance to the Drake Passage. Because of persistently stormy conditions and the resulting bad weather avoidance, we were not successful in recovering the originally planned Proposed Site CSP-3A in the Polar Frontal Zone of the CSP. The drilled sediments at Sites U1541 and U1543 reach back to the late Miocene, and those at Site U1540 reach back to the early Pliocene. High sedimentation rate s

Published
2021

3. Site U1542.

Author

Lamy, F., Winckler, G., Zarikian, C. A. Alvarez, Arz, H. W., Basak, C., Brombacher, A., Esper, O. M., Farmer, J. R., Gottschalk, J., Herbert, L. C., Iwasaki, S., Lawson, V. J., Lembke-Jene, L., Lo, L., Malinverno, E., Michel, E., Middleton, J. L., Moretti, S., Moy, C. M., and Ravelo, A. C.

Subjects
OCEAN temperature, CARBON cycle, BIOLOGICAL productivity, ICE sheets
Published
2021
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4. Site U1541.

Author

Winckler, G., Lamy, F., Zarikian, C. A. Alvarez, Arz, H. W., Basak, C., Brombacher, A., Esper, O. M., Farmer, J. R., Gottschalk, J., Herbert, L. C., Iwasaki, S., Lawson, V. J., Lembke-Jene, L., Lo, L., Malinverno, E., Michel, E., Middleton, J. L., Moretti, S., Moy, C. M., and Ravelo, A. C.

Subjects
CARBON cycle, BIOLOGICAL productivity, ICE sheets, OCEAN temperature
Published
2021
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5. Expedition 383 methods.

Author

Winckler, G., Lamy, F., Zarikian, C. A. Alvarez, Arz, H. W., Basak, C., Brombacher, A., Esper, O. M., Farmer, J. R., Gottschalk, J., Herbert, L. C., Iwasaki, S., Lawson, V. J., Lembke-Jene, L., Lo, L., Malinverno, E., Michel, E., Middleton, J. L., Moretti, S., Moy, C. M., and Ravelo, A. C.

Subjects
ICE sheets, CARBON cycle, GLOBAL Positioning System, INFORMATION retrieval
Published
2021
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6. Expedition 383 summary.

Author

Winckler, G., Lamy, F., Zarikian, C. A. Alvarez, Arz, H. W., Basak, C., Brombacher, A., Esper, O. M., Farmer, J. R., Gottschalk, J., Herbert, L. C., Iwasaki, S., Lawson, V. J., Lembke-Jene, L., Lo, L., Malinverno, E., Michel, E., Middleton, J. L., Moretti, S., Moy, C. M., and Ravelo, A. C.

Subjects
ANTARCTIC Circumpolar Current, CARBON cycle, BIOLOGICAL productivity, ICE sheets, PALEOCEANOGRAPHY
Abstract

The Antarctic Circumpolar Current (ACC), the world's strongest zonal current system, connects all three major ocean basins of the global ocean and therefore integrates and responds to global climate variability. Its flow is largely driven by strong westerly winds and is constricted to its narrowest extent in the Drake Passage. Fresh and cold Pacific surface and intermediate water flowing through the Drake Passage (cold-water route) and warm Indian Ocean water masses flowing through the Agulhas region (warmwater route) are critical for the South Atlantic contribution to Meridional Overturning Circulation changes. Furthermore, physical and biological processes associated with the ACC affect the strength of the ocean carbon pump and therefore are critical to feedbacks linking atmospheric CO2 concentrations, ocean circulation, and climate/cryosphere on a global scale. In contrast to the Atlantic and Indian sectors of the ACC, and with the exception of drill cores from the Antarctic continental margin and off New Zealand, there are no deep-sea drilling paleoceanographic records from the Pacific sector of the ACC. To advance our understanding of Miocene to Holocene atmosphere-ocean-cryosphere dynamics in the Pacific and their implications for regional and global climate and atmospheric CO2, International Ocean Discovery Program Expedition 383 recovered sedimentary sequences at (1) three sites in the central South Pacific (CSP) (U1539, U1540, and U1541), (2) two sites at the Chilean margin (U1542 and U1544), and (3) one site from the pelagic eastern South Pacific (U1543) close to the entrance to the Drake Passage. Because of persistently stormy conditions and the resulting bad weather avoidance, we were not successful in recovering the originally planned Proposed Site CSP-3A in the Polar Frontal Zone of the CSP. The drilled sediments at Sites U1541 and U1543 reach back to the late Miocene, and those at Site U1540 reach back to the early Pliocene. High sedimentation rate sequences reaching back to the early Pleistocene (Site U1539) and the late Pleistocene (Sites U1542 and U1544) were recovered in both the CSP and at the Chilean margin. Taken together, the sites represent a depth transect from ~1100 m at Chilean margin Site U1542 to ~4070 m at CSP Site U1539 and allow investigation of changes in the vertical structure of the ACC, a key issue for understanding the role of the Southern Ocean in the global carbon cycle. The sites are located at latitudes and water depths where sediments will allow the application of a wide range of siliciclastic-, carbonate-, and opalbased proxies to address our objectives of reconstructing, with unprecedented stratigraphic detail, surface to deep-ocean variations and their relation to atmosphere and cryosphere changes. [ABSTRACT FROM AUTHOR]

Published
2021
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11. Metergoline as an alternative to bromocriptine in amenorrhoea

Author

Hicks, B. H., Finer, N., and Herbert, L. C.

Abstract

Abstract. The results of this study offer further evidence that metergoline is a valuable alternative to bromocriptine in the suppression of excessive prolactin secretion. Forty-nine hyperprolactinaemic and 44 normoprolactinaemic women with amenorrhoea took part in a double-blind trial to compare the efficacy of metergoline 12 mg/day and bromocriptine 7.5 mg/day in restoring menstruation and ovulation. All the women had normal results on conventional tomography of the sella turcica, normal gonadotrophin levels and normal androgen levels. In the hyperprolactinaemic group, metergoline and bromocriptine were equally effective, with 84 and 75% respectively achieving menstruation, and 76 and 67% respectively achieving ovulation, within 4 months. In the normoprolactinaemic group, 47% menstruated and 40% ovulated on metergoline, against comparative figures of 36 and 21% for bromocriptine and 20 and 13% for placebo, but the differences were not statistically significant. Side effects were not a major problem.

Published
1984
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12. Letters.

Author

Greenfield, Peter, Wright, J. L., Eades, A., Long, Graham, Herbert, L. C., Corp, David, MacDonald, Jose, Stephens, D., Rimington, John, Ward, Ashley, Braid, Jim, Simpson, Jo, Howarth, Robert, and Rowland, Wendy

Subjects
LETTERS to the editor, AGRICULTURE, DAIRY farming, ASSOCIATIONS, institutions, etc.
Abstract

Presents letters to the editor referencing articles and topics discussed in previous issues. Proposed requirements for cross-compliance for British growers to qualify for the new single farm payments from 2005; "Talking Point," by Geoffrey Hollis in the April 23, 2004 issue; Importance of the Milk Development Council and the National Dairy Council.

Published
2004

13. Effect of propylthiouracil treatment during prenatal and early postnatal development on the neocortex of rat pups.

Author

Behnam-Rassoli M, Herbert LC, Howard V, Pharoah PO, and Stanisstreet M

Subjects
Animals, Cell Count, Cerebral Cortex drug effects, Cerebral Cortex growth & development, Female, Litter Size drug effects, Maternal-Fetal Exchange, Neuroglia cytology, Neurons cytology, Pregnancy, Rats, Rats, Inbred Strains, Thyroxine pharmacology, Triiodothyronine pharmacology, Cerebral Cortex embryology, Propylthiouracil pharmacology
Abstract

The effects of a pre- and postnatal hypothyroid environment on the development of the neocortex have been determined. Rats were treated with propylthiouracil (PTU) with or without thyroid hormone supplementation during pregnancy and throughout the early development of the pups. The Cavalieri method was used to provide an estimate of the volume of the neocortex, and a combination of the Cavalieri method and the 'disector' particle-counting method provided an unbiased estimate of the numbers of glia and neurons in the neocortex. In pups from non-treated rats the mean volume of the neocortex increased from 31.3 mm3 at 5 days postnatally to 191.5 mm3 at 20 days and then remained constant to day 48. Similarly, the mean number of glial cells increased from 5.2 x 10(6) at day 5 to 12.0 x 10(6) on day 20 and then remained constant to day 48. The mean number of neurons in the neocortex in the control condition was constant at about 14.6 x 10(6) from day 5 to day 48. PTU treatment during pregnancy and postnatal development significantly decreased the mean volume of the neocortex at all of the stages studied, for example from 31.3 to 23.3 mm3 (p less than 0.001) on day 5 and from 191.5 to 155.0 mm3 (p less than 0.001) on day 20. Supplementation with thyroxine (T4) or tri-iodothyronine partially reversed this at certain stages. For example, the mean volume of the neocortex at 48 days was 197.5 mm3 in control rats, 118.1 mm3 in PTU-treated rats and 169.3 mm3 in PTU-treated rats supplemented with T4. Within the neocortex, the volume of the neuropile was more severely affected than was the volume of the neuron cell bodies.(ABSTRACT TRUNCATED AT 250 WORDS)

Published
1991
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14. Metergoline as an alternative to bromocriptine in amenorrhoea.

Author

Hicks BH, Finer N, and Herbert LC

Subjects
Adult, Clinical Trials as Topic, Dose-Response Relationship, Drug, Double-Blind Method, Female, Follicle Stimulating Hormone blood, Humans, Luteinizing Hormone blood, Menstruation drug effects, Ovulation drug effects, Progesterone blood, Random Allocation, Time Factors, Amenorrhea drug therapy, Bromocriptine therapeutic use, Ergolines therapeutic use, Metergoline therapeutic use, Prolactin blood
Abstract

The results of this study offer further evidence that metergoline is a valuable alternative to bromocriptine in the suppression of excessive prolactin secretion. Forty-nine hyperprolactinaemic and 44 normoprolactinaemic women with amenorrhoea took part in a double-blind trial to compare the efficacy of metergoline 12 mg/day and bromocriptine 7.5 mg/day in restoring menstruation and ovulation. All the women had normal results on conventional tomography of the sella turcica, normal gonadotrophin levels and normal androgen levels. In the hyperprolactinaemic group, metergoline and bromocriptine were equally effective, with 84 and 75% respectively achieving menstruation, and 76 and 67% respectively achieving ovulation, within 4 months. In the normoprolactinaemic group, 47% menstruated and 40% ovulated on metergoline, against comparative figures of 36 and 21% for bromocriptine and 20 and 13% for placebo, but the differences were not statistically significant. Side effects were not a major problem.

Published
1984
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