The Island Mass Effect

Doty, Maxwell S.; Oguri, Mikihiko

doi:10.1093/icesjms/22.1.33

Cited by 299 publications

(183 citation statements)

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“…It also strongly impacts the local oceanic physical dynamics due to its island mass effect (Doty and Oguri, 1956). The interactions between geostrophic water flow disturbances due to the presence of the island, the tidal activity over the plateau, and the strong winds characterizing the area generate internal waves, eddies, jets, Ekman pumping, and a complex hydrodynamical environment (Heywood et al, 1990;Park et al, 2008;Gille et al, 2014).…”

Section: A J Cavagna Et Al: N Cycling In the Vicinity Of Kerguelenmentioning

confidence: 99%

Production regime and associated N cycling in the vicinity of Kerguelen Island, Southern Ocean

et al. 2015

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Abstract. Although the Southern Ocean is considered a high-nutrient, low-chlorophyll (HNLC) area, massive and recurrent blooms are observed over and downstream of the Kerguelen Plateau. This mosaic of blooms is triggered by a higher iron supply resulting from the interaction between the Antarctic Circumpolar Current and the local bathymetry. Net primary production, N uptake (NO − 3 and NH + 4 ), and nitrification rates were measured at eight stations in austral spring 2011 (October-November) during the KEOPS 2 cruise in the Kerguelen Plateau area. Natural iron fertilization stimulated primary production, with mixed layer integrated net primary production and growth rates much higher in the fertilized areas (up to 315 mmol C m −2 d −1 and up to 0.31 d −1 respectively) compared to the HNLC reference site (12 mmol C m −2 d −1 and 0.06 d −1 respectively). Primary production was mainly sustained by nitrate uptake, with f ratios (corresponding to NO − 3 -uptake / (NO − 3 -uptake + NH + 4 -uptake)) lying at the upper end of the observations for the Southern Ocean (up to 0.9). We report high rates of nitrification (up to ∼ 3 µmol N L −1 d −1 , with ∼ 90 % of them < 1 µmol N L −1 d −1 ) typically occurring below the euphotic zone, as classically observed in the global ocean. The specificity of the studied area is that at most of the stations, the euphotic layer was shallower than the mixed layer, implying that nitrifiers can efficiently compete with phytoplankton for the ammonium produced by remineralization at low-light intensities. Nitrate produced by nitrification in the mixed layer below the euphotic zone is easily supplied to the euphotic zone waters above, and nitrification sustained 70 ± 30 % of the nitrate uptake in the productive area above the Kerguelen Plateau. This complicates estimations of new production as potentially exportable production. We conclude that high productivity in deep mixing system stimulates the N cycle by increasing both assimilation and regeneration.

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Section: A J Cavagna Et Al: N Cycling In the Vicinity Of Kerguelenmentioning

confidence: 99%

Production regime and associated N cycling in the vicinity of Kerguelen Island, Southern Ocean

et al. 2015

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“…This allows the island to interact with the seasonally reversing monsoon. Many studies have reported the influence of flow interaction with islands and headlands leading to enhanced primary production -termed the island mass effect (IME) by Doty and Oguri (1956). These studies have included different spatial scales using laboratory and field experiments to understand circulation and enhanced productivity.…”

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confidence: 99%

Surface circulation and upwelling patterns around Sri Lanka

2014

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Abstract. Sri Lanka occupies a unique location within the equatorial belt in the northern Indian Ocean, with the Arabian Sea on its western side and the Bay of Bengal on its eastern side, and experiences bi-annually reversing monsoon winds. Aggregations of blue whale (Balaenoptera musculus) have been observed along the southern coast of Sri Lanka during the northeast (NE) monsoon, when satellite imagery indicates lower productivity in the surface waters. This study explored elements of the dynamics of the surface circulation and coastal upwelling in the waters around Sri Lanka using satellite imagery and numerical simulations using the Regional Ocean Modelling System (ROMS). The model was run for 3 years to examine the seasonal and shorter-term (∼ 10 days) variability. The results reproduced correctly the reversing current system, between the Equator and Sri Lanka, in response to the changing wind field: the eastward flowing Southwest Monsoon Current (SMC) during the southwest (SW) monsoon transporting 11.5 Sv (mean over [2010][2011][2012] and the westward flowing Northeast Monsoon Current (NMC) transporting 9.6 Sv during the NE monsoon, respectively. A recirculation feature located to the east of Sri Lanka during the SW monsoon, the Sri Lanka Dome, is shown to result from the interaction between the SMC and the island of Sri Lanka. Along the eastern and western coasts, during both monsoon periods, flow is southward converging along the southern coast. During the SW monsoon, the island deflects the eastward flowing SMC southward, whilst along the eastern coast, the southward flow results from the Sri Lanka Dome recirculation. The major upwelling region, during both monsoon periods, is located along the southern coast, resulting from southward flow converging along the southern coast and subsequent divergence associated with the offshore transport of water. Higher surface chlorophyll concentrations were observed during the SW monsoon. The location of the flow convergence and hence the upwelling centre was dependent on the relative strengths of wind-driven flow along the eastern and western coasts: during the SW (NE) monsoon, the flow along the western (eastern) coast was stronger, migrating the upwelling centre to the east (west).

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“…Satellite observations (CZCS-Coastal Zone Color Scanner) reveal distinct chlorophyll plumes trailing off to leeward of Seychelles atolls (Dustan, submitted) and a general increase in chlorophyll over the entire northern island platform encompassing the northern granitic islands. Such an island mass effect (sensu Doty and Oguri, 1956) would be enhanced by rainfall and subsequent nutrient runnoff in the high islands and would contribute significantly to the regional patchiness of phytoplankton production.…”

Section: Discussionmentioning

confidence: 99%

Estimates of Indian Ocean productivity using natural fluorescence

Dustan¹

1992

Atoll Research Bulletin

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Measurements of the vertical distribution of phytoplankton natural fluorescence in the equatorial Indian Ocean produced estimates of oceanic productivity ranging from 70 to 150 mg C-m' '.day-'. Vertical profiles of the water column revealed the presence of a distinct chlorophyll maximum which forms at or near the top of the thermocline at almost every station. Localized upwelling was observed in the vicinity of atolls which appears to be responsible for an island mass effect that may add to downstream oceanic productivity. There were no significant differences along an east and northward oceanic transect from 63" 20' E to 88" 56' E longitude. The estimates agree with previously reported production estimates for the Indian Ocean reinforcing the image of low and variable rates of production throughout the deep oceanic basin punctuated by localized islandinduced upwellings.

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The Island Mass Effect

Cited by 299 publications

References 0 publications

Production regime and associated N cycling in the vicinity of Kerguelen Island, Southern Ocean

Production regime and associated N cycling in the vicinity of Kerguelen Island, Southern Ocean

Surface circulation and upwelling patterns around Sri Lanka

Estimates of Indian Ocean productivity using natural fluorescence

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