Annual cycle of steric height in the Indian Ocean estimated from the thermal field

Peter, Benny N.; Mizuno, Keisuke

doi:10.1016/s0967-0637(99)00088-6

Cited by 13 publications

(5 citation statements)

References 23 publications

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“…, consistent with previous observations of Rossby waves in this region (Peter and Mizuno 2000). The trace of the signals is not seen west of the bend in the coastal waveguide where Sumatra and Java meet.…”

supporting

confidence: 92%

Vertical Structure of Kelvin Waves in the Indonesian Throughflow Exit Passages

Drushka

Sprintall

Gille

et al. 2010

Journal of Physical Oceanography

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The subsurface structure of intraseasonal Kelvin waves in two Indonesian Throughflow (ITF) exit passages is observed and characterized using velocity and temperature data from the 2004-06 International Nusantara Stratification and Transport (INSTANT) project. Scatterometer winds are used to characterize forcing, and altimetric sea level anomaly (SLA) data are used to trace the pathways of Kelvin waves east from their generation region in the equatorial Indian Ocean to Sumatra, south along the Indonesian coast, and into the ITF region.During the 3-yr INSTANT period, 40 intraseasonal Kelvin waves forced by winds over the central equatorial Indian Ocean caused strong transport anomalies in the ITF outflow passages. Of these events, 21 are classed as ''downwelling'' Kelvin waves, forced by westerly winds and linked to depressions in the thermocline and warm temperature anomalies in the ITF outflow passages; 19 were ''upwelling'' Kelvin waves, generated by easterly wind events and linked to shoaling of the thermocline and cool temperature anomalies in the ITF. Both downwelling and upwelling Kelvin waves have similar vertical structures in the ITF outflow passages, with strong transport anomalies over all depths and a distinctive upward tilt to the phase that indicates downward energy propagation. A linear wind-forced model shows that the first two baroclinic modes account for most of the intraseasonal variance in the ITF outflow passages associated with Kelvin waves and highlights the importance of winds both in the eastern equatorial Indian Ocean and along the coast of Sumatra and Java for exciting Kelvin waves.Using SLA as a proxy for Kelvin wave energy shows that 37% 6 9% of the incoming Kelvin wave energy from the Indian Ocean bypasses the gap in the coastal waveguide at Lombok Strait and continues eastward. Of the energy that continues eastward downstream of Lombok Strait, the Kelvin waves are split by Sumba Island, with roughly equal energy going north and south to enter the Savu Sea.

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supporting

confidence: 92%

Vertical Structure of Kelvin Waves in the Indonesian Throughflow Exit Passages

Drushka

Sprintall

Gille

et al. 2010

Journal of Physical Oceanography

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“…Of most interest for this study are those waves north of 13°S. The model results compare well with other work on Rossby waves in the tropical South Indian Ocean [ Perigaud and Delecluse , 1992, 1993; Masumoto and Meyers , 1998; Peters and Mizuno , 2000; White , 2000; Matano et al , 2002; Wang et al , 2001; Jury and Huang , 2004; Baquero‐Bernal and Latif , 2005]. The Rossby waves at 12°S in particular have been studied in some detail, with Matano et al [2002] suggesting that they are topographically steered and Wang et al [2001] showing that the influence of localized forcing between 70°E and 80°E causes the waves to “breakdown.” It is evident from Figure 6 that at 9°S–11°S, the Rossby wave starts to breakdown west of 75°E–80°E while another Rossby waveforms at 65°E.…”

Section: Influence Of Rossby Wavessupporting

confidence: 73%

Annual cycle of the South Indian Ocean (Seychelles‐Chagos) thermocline ridge in a regional ocean model

Hermes¹,

Reason²

2008

J. Geophys. Res.

160

158

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The presence of an upwelling “dome”‐like feature in the thermocline depth at 55°E–65°E, 5°S–12°S in the southwest tropical Indian Ocean (SWTIO) has been suggested in earlier work. However, the position, shape, and forcing mechanisms behind this upwelling region are not well understood. In this study, a regional ocean model is applied to the tropical South Indian Ocean. Experiments with monthly climatological winds from both Quick Scatterometer (QuikSCAT) and the National Centers for Environmental Protection (NCEP) reanalyses are performed. An annual and semiannual signal is present in the depth of the model thermocline. The model results suggest that SWTIO upwelling is focused in the west during austral spring and summer and forms a zonally elongated ridge during austral autumn and winter, termed here the Seychelles‐Chagos thermocline ridge. Although the large‐scale wind stress curl plays a major role in maintaining this upwelling ridge, local divergence between the southeasterly trade winds and the monsoon westerlies are shown to impact this region, as well as remote forcing through the arrival of both upwelling and downwelling annual Rossby waves from the eastern Indian Ocean.

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“…Without the trough, these flows would presumably reverse during the opposite seasons and not have much impact. But there clearly seems to be a convergence into the SECC from the north that persists over the annual cycle (Figure 5 in Peter & Mizuno, ). The inflow from the north then joins with the outflow from the Pacific and becomes part of the Agulhas Current along the coast of Africa, as illustrated in the bottom panel of Figure .…”

Section: Discussionmentioning

confidence: 99%

Upwelling in the Ocean Basins North of the ACC: 2. How Cool Subantarctic Water Reaches the Surface in the Tropics

et al. 2019

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Large volumes of cool water are drawn up to the surface in the tropical oceans. A companion paper shows that the cool water reaches the surface in or near the upwelling zones off northern and southern Africa and Peru. The cool water has a subantarctic origin and spreads extensively across the Atlantic and Pacific basins after it reaches the surface. Here, we look at the spreading in two low‐resolution ocean general circulation models and find that the spreading in the models is much less extensive than observed. The problem seems to be the way the upwelling and the spreading are connected (or not connected) to the ocean's large‐scale overturning. As proposed here, the cool upwelling develops when warm buoyant water in the western tropics is drawn away to become deep water in the North Atlantic. The “drawing away” shoals the tropical thermocline in a way that allows cool subantarctic water to be drawn up to the surface along the eastern margins. The amounts of upwelling produced this way exceed the amounts generated by the winds in the upwelling zones by as much as 4 times. Flow restrictions make it difficult for the warm buoyant water in our models to be drawn away.

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Annual cycle of steric height in the Indian Ocean estimated from the thermal field

Cited by 13 publications

References 23 publications

Vertical Structure of Kelvin Waves in the Indonesian Throughflow Exit Passages

Vertical Structure of Kelvin Waves in the Indonesian Throughflow Exit Passages

Annual cycle of the South Indian Ocean (Seychelles‐Chagos) thermocline ridge in a regional ocean model

Upwelling in the Ocean Basins North of the ACC: 2. How Cool Subantarctic Water Reaches the Surface in the Tropics

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