Seasonal Phasing of Agulhas Current Transport Tied to a Baroclinic Adjustment of Near‐Field Winds

Katherine Hutchinson; Lisa M. Beal; Pierrick Penven; Isabelle Ansorge; Juliet Hermes

doi:10.1029/2018jc014319

Evidence that Agulhas Current transport is maintained during a meander

Journal of Geophysical Research Oceans ◽

10.1002/2014jc009802 ◽

2014 ◽

Vol 119 (6) ◽

pp. 3806-3817 ◽

Cited By ~ 11

Author(s):

Greta M. Leber ◽

Lisa M. Beal

Keyword(s):

Current Transport ◽

Agulhas Current

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Impact of the Indonesian Throughflow on Agulhas leakage

Ocean Science ◽

10.5194/os-9-773-2013 ◽

2013 ◽

Vol 9 (5) ◽

pp. 773-785 ◽

Cited By ~ 19

Author(s):

D. Le Bars ◽

H. A. Dijkstra ◽

W. P. M. De Ruijter

Keyword(s):

Large Scale ◽

Ocean Model ◽

Global Ocean ◽

Momentum Balance ◽

Indonesian Throughflow ◽

Current Transport ◽

Flat Bottom ◽

Agulhas Current ◽

The Pacific ◽

Wide Range

Abstract. Using ocean models of different complexity we show that opening the Indonesian Passage between the Pacific and the Indian oceans increases the input of Indian Ocean water into the South Atlantic via the Agulhas leakage. In a strongly eddying global ocean model this response results from an increased Agulhas Current transport and a constant proportion of Agulhas retroflection south of Africa. The leakage increases through an increased frequency of ring shedding events. In an idealized two-layer and flat-bottom eddy resolving model, the proportion of the Agulhas Current transport that retroflects is (for a wide range of wind stress forcing) not affected by an opening of the Indonesian Passage. Using a comparison with a linear model and previous work on the retroflection problem, the result is explained as a balance between two mechanisms: decrease retroflection due to large-scale momentum balance and increase due to local barotropic/baroclinic instabilities.

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Decoupling of the Agulhas Leakage from the Agulhas Current

Journal of Physical Oceanography ◽

10.1175/jpo-d-13-093.1 ◽

2014 ◽

Vol 44 (7) ◽

pp. 1776-1797 ◽

Cited By ~ 39

Author(s):

Benjamin R. Loveday ◽

Jonathan V. Durgadoo ◽

Chris J. C. Reason ◽

Arne Biastoch ◽

Pierrick Penven

Keyword(s):

Wind Stress ◽

Ocean Basin ◽

Global Ocean ◽

Trade Wind ◽

Current Transport ◽

Trade Winds ◽

Agulhas Current ◽

Basin Scale ◽

Stress Changes ◽

The Indian Ocean

Abstract The relationship between the Agulhas Current and the Agulhas leakage is not well understood. Here, this is investigated using two basin-scale and two global ocean models of incrementally increasing resolution. The response of the Agulhas Current is evaluated under a series of sensitivity experiments, in which idealized anomalies, designed to geometrically modulate zonal trade wind stress, are applied across the Indian Ocean Basin. The imposed wind stress changes exceed plus or minus two standard deviations from the annual-mean trade winds and, in the case of intensification, are partially representative of recently observed trends. The Agulhas leakage is quantified using complimentary techniques based on Lagrangian virtual floats and Eulerian passive tracer flux. As resolution increases, model behavior converges and the sensitivity of the leakage to Agulhas Current transport anomalies is reduced. In the two eddy-resolving configurations tested, the leakage is insensitive to changes in Agulhas Current transport at 32°S, though substantial eddy kinetic energy anomalies are evident. Consistent with observations, the position of the retroflection remains stable. The decoupling of Agulhas Current variability from the Agulhas leakage suggests that while correlations between the two may exist, they may not have a clear dynamical basis. It is suggested that present and future Agulhas leakage proxies should be considered in the context of potentially transient forcing regimes.

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Impact of the Indonesian throughflow on Agulhas leakage

Ocean Science Discussions ◽

10.5194/osd-10-353-2013 ◽

2013 ◽

Vol 10 (1) ◽

pp. 353-391 ◽

Cited By ~ 5

Author(s):

D. Le Bars ◽

H. A. Dijkstra ◽

W. P. M. De Ruijter

Keyword(s):

Indian Ocean ◽

Ocean Model ◽

Global Ocean ◽

Indonesian Throughflow ◽

Current Transport ◽

Flat Bottom ◽

Agulhas Current ◽

The Pacific ◽

Wide Range ◽

The Indian Ocean

Abstract. Using ocean models of different complexity we show that opening the Indonesian Passage between the Pacific and the Indian Ocean increases the input of Indian Ocean water into the South Atlantic via the Agulhas leakage. In a strongly eddying global ocean model this response results from an increased Agulhas Current transport and a constant proportion of Agulhas retroflection south of Africa. The leakage increases through an increased frequency of ring shedding events. In an idealized two-layer and flat-bottom eddy resolving model, the proportion of the Agulhas Current transport that retroflects is (for a wide range of wind stress forcing) not affected by an opening of the Indonesian Passage. A linear ocean model is not able to explain this behavior which reveals the importance of mixed barotropic/baroclinic instabilities in controlling the Agulhas leakage.

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Near-field scanning optical microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100144644 ◽

1986 ◽

Vol 44 ◽

pp. 642-643

Author(s):

E. Betzig ◽

A. Harootunian ◽

M. Isaacson ◽

A. Lewis

Keyword(s):

Near Field ◽

Optical Microscope ◽

Visible Radiation ◽

Field Methods ◽

Optical Elements ◽

Optical Region ◽

Order Of Magnitude ◽

Nondestructive Imaging ◽

Scanning Optical Microscopy ◽

Near Field Scanning

In general, conventional methods of optical imaging are limited in spatial resolution by either the wavelength of the radiation used or by the aberrations of the optical elements. This is true whether one uses a scanning probe or a fixed beam method. The reason for the wavelength limit of resolution is due to the far field methods of producing or detecting the radiation. If one resorts to restricting our probes to the near field optical region, then the possibility exists of obtaining spatial resolutions more than an order of magnitude smaller than the optical wavelength of the radiation used. In this paper, we will describe the principles underlying such "near field" imaging and present some preliminary results from a near field scanning optical microscope (NS0M) that uses visible radiation and is capable of resolutions comparable to an SEM. The advantage of such a technique is the possibility of completely nondestructive imaging in air at spatial resolutions of about 50nm.

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